Human Anatomy and Physiology Notes

 

Cardiovascular System

Blood flows from high pressure to low pressure; controlled by timing of contractions; directed by one-way valves Pulmonary Circuit – carries blood to and from gas exchange surfaces of lungs Systemic Circuit – carries blood to and from the body Blood Vessels distribute blood around the body; Arteries – carry blood away from the heart to the capillaries Capillaries – networks between arteries and veins; permits exchange of gases, nutrients and wastes between blood and tissues; composed of endothelium what sparse basal lamina; pericytes (smooth muscle like cells) on the outside help stabilise the capillary wall Veins – carry blood from capillaries to the heart Tunics – 3 layers of the arteries and veins; Tunica interna (intima)  – – includes endothelial layer and underlying layer of connective tissue containing elastic fibres; provides friction-free environment for easy passage of blood; arteries have a thick layer of elastic fibres, making an internal elastic membrane Tunica media – smooth muscle and elastic fibre layer; controls vasoconstriction/vasodilation of vessel; muscle cells contract and relax Tunica externa (adventitia) – collagen fibres with scattered bands of elastic fibres that protect and reinforce vessels to surrounding structures; larger vessels contain vasa vasorum, network of small blood vessels that supply blood to outer half of large blood vessels, inner half nourished by diffusion of blood from lumen Heart  – – pumps blood and maintains blood pressure

Layers of the Heart Wall Pericardium – double walled pericardial sac that is made of fibrous f ibrous tissue consisting of collagen fibres which enclose the heart and stabilise it; allows the heart to beat without friction, provides room to expand and yet resist excessive expansion Parietal Pericardium – outer wall of sac; superficial fibrous f ibrous layer of connective tissue; deep thin serous layer; not a heart wall layer but is continuous with serous membrane of the visceral pericardium Pericardial Cavity – space inside pericardial sac filled with 5-30mL of pericardial fluid Pericarditis – inflammation of the membranes; causes painful friction rub with each heartbeat Epicardium (visceral pericardium) – covers the surface of the heart; serous membrane consisting of simple squamous epithelium (produce lubricant that is released between the layers to maintain a slippery non-adhesive and protective surface) and underlying connective tissue (attached to myocardium) Myocardium – middle muscular layer forming atria and ventricles; contains cardiac muscle tissue, blood vessels and nerves; concentric muscle tissue layers (form a figure eight around the atria; superficial muscle layers wrap both ventricles; deep muscle layers form figure-eight f igure-eight around ventricles) Endocardium – covering inner surfaces of heart, including valves; composed of simple squamous epithelium and underlying areolar tissue; continuous with endothelium of the attached great blood vessels Cardiac Muscle Cells – small in size, have many mitochondria and capillaries; contain 1 or 2 nuclei; interconnected branching between cells; specialised intercellular connections between cells called intercalated discs Intercalated Discs – convey force of contraction, propagate action of potentials, allow all cells function f unction as one; secured by desmosomes which stabilise 2 adjacent cells and help resist shearing forces; also linked link ed by gap  junctions which allow ions to move directly between cells; cells; Inside the Heart Interatrial Septum – wall that separates atria Pectinate Muscles – woven ridges of cardiac muscle on interior of atrial walls; w alls; permits great strength of contraction with a minimum of muscle mass Interventricular Septum – muscular wall that separates ventricles

 

Trabecular Carnae – internal ridges of ventricles; prevents suction that would occur with a flat surfaced membrane

and thus impair heart’s ability to pump efficiently  Right Atrium collects blood from systemic circuit Superior Vena Cava – receives blood from upper body (head, neck, upper limbs and chest) Inferior Vena Cava – receives blood from lower body (trunk, viscera and lower limbs) Coronary Sinus – receives blood from cardiac veins Right Ventricle pumps blood to pulmonary circuit Left Atrium collects blood from pulmonary circuit Left Ventricle pumps blood to systemic circuit; thicker and more muscular than the right; does not have moderator band Heart Valves – two pairs of one-way valves preventing backflow during contraction Atrioventricular (AV) Valves – bicuspid valve cusps between atria and ventricles; chordae chordae tendineae connect the valves to papillary muscle, prevents it from swinging into the atria when it contracts Right AV Valve: aka tricuspid valve; opens from right atrium to right ventricle Left AV Valve: aka bicuspid valve, or mitral valve; opens from left atrium to left ventricle Semilunar Valves – pulmonary and aortic tricuspid valves that prevent backflow from pulmonary trunk and aorta into ventricles; have no muscular support; three cusps support like a tripod Pulmonary Valve: opens from right ventricle to pulmonary trunk; has 3 semilunar cusps Aortic Semilunar Valve: opens from left ventricle to ascending aorta AV Valve Mechanics Ventricles Relax: pressure drops  semilunar valves close as blood attempts to return to ventricles from vessels  AV

valves open to allow blood from atria

Ventricles Contract: AV valves close as blood attempts to return to atria  pressure increases semilunar valves open and blood flows into great vessels Coronary Artery Disease – heart muscles receive insufficient blood supply; narrowing of vessels (atherosclerosis [smooth muscle and fatty deposit build-up in walls of artery], artery spasm or clot) Treated with drugs, bypass graft of vessel, widening of the vessel via angioplasty, or stent Blood   – – transfers blood cells and dissolved substances (O 2, CO2, hormones, waste products); regulation of pH and ions

(by blood proteins); temperature regulation; defence against toxins and a nd pathogens (by leukocytes) Whole blood consists of Plasma (55%), Erythocytes (45%), and Leukocytes and Platelets (<1%); when separated by centrifuge, plasma is at the top, erythrocytes at the bottom, and a buffy coat (leukocytes and platelets) form in between. Hemopoiesis – formulation of cellular blood components by hemopoietic tissues Yolk sac produces first hemopoiesis stem cells in the foetus, which colonise the bone marrow, liver, spleen and thymus; liver stops producing blood cells at birth; spleen continues lymphocyte production; red bone marrow produces all the blood elements through pluripotent stem cells Plasma is a mixture of water, proteins, nutrients, electrolytes, nitrogenous wastes, hormones and gases Albumins (60%) proteins that transport fatty acids, thyroid hormones and steroid hormones Globulins (35%) can be antibodies also called immunoglobulins; also proteins that transport hormones, metallic ions, lipids and steroids Fibrinogens (5%) proteins that form clots and produce long insoluble strands of fibrin Leukocytes are white blood cells that are also part of the immune system; defends against infectious microorganisms and pathogens; removes toxins and wastes, attacks other abnormal cells; have no haemoglobin, but have nuclei and other organelles for protein synthesis; 5 types divided into 2 categories

 

 

Granulocytes have specific specific granules granules that contain enzymes and other other chemicals chemicals for defence against pathogens Neutrophils have barely visible granules, 3 to 5 lobed nucleus; increased numbers during bacterial infections, phagocytosis and release antimicrobial chemicals Eosinophils have large rosy-orange granules, bilobed nucleus; increased numbers during parasitic infections, collagen diseases, allergies, asthma, diseases of the spleen and CNS; phagocytosis of antigen antibody complexes, allergens and inflammatory chemicals; release enzymes to destroy large parasites Basophils have large abundant violet granules, obscure large S-shaped nucleus; increased numbers in i n chicken pox, sinusitis and parasitic infections; secretes histamine (vasodilator) to speed up flow of blood to an injured area; secretes heparin (anticoagulant) to promote the mobility of other WBCS Agranulocytes are apparently absent of granules; do contain nonspecific (azurophilic) granules which are lysozymes, inconspicuous so cytoplasm looks clear Lymphocytes have bluish cytoplasm, round uniform dark violet nucleus; increased numbers in diverse infections and immune responses; destroys cells (cancer, foreign and virally infected cells); activates and coordinates actions of other immune system cells; secretes antibodies and provides immunity memory Monocytes are the largest WBC, round with kidney or horseshoe shaped nucleus; increased numbers in viral infections and inflammation; leaves the bloodstream and transforms into macrophages to phagocytise pathogens and debris

Leukopoiesis – production of white blood cells with pluripotent stem cells; Granulocytes are formed by myeloblasts; stored and released by red bone marrow; circulates bloodstream for 4-8 hours and then migrate into tissues where they live for 5 days longer

Monocytes are formed monoblasts’and sotred andseveral released by red bone marrow;  circulates bloodstream for 20 hours, then transform into by macrophages live for years in tissues All lymphocytes are formed by lymphoblasts, with T lymphocyte completing development in the thymus; provide longterm immunity (approx decades) and are continuously recycled from blood to tissue fluid to lymph and back to blood Platelets involved in clotting (haemostasis); small fragments of megakaryocyte marrow cells; 2- 4μm diameter; has granules; secrete vasoconstrictors that help reduce blood loss; stick together to form platelet plugs to seal small breaks; secrete procoagulants or clotting factors to promote clotting; initiate formation of clot-dissolving enzyme; chemically attract neutrophils and monocytes to sites of inflammation; phagocytise and destroy bacteria; secreate growth factors that stimulate mitosis to repair blood vessels Haemostasis is the cessation of bleeding; stops potentially fatal leaks and excessive bleeding (haemorrhage); 3 mechanisms – vascular spasm, platelet plug formation, and blood clotting (coagulation) Vascular Spasm  – most immediate protection; prompt constriction of a broken vessel to decrease blood loss; activated by pain receptors; smooth muscle injury; reaction to serotonin, a vasoconstrictor released by platelets; allows time for other clotting pathways to act on injury site Platelet Plate Formation – broken vessel exposes collagen; platelets stick to damaged vessel and other platelets, contract and draw vessel walls together to form a platelet plug; positive feedback cycle active until the break is sealed Coagulation – conversion of plasma protein fibrinogen into insoluble fibrin threads to form f orm framework of clot; procoagulants/clotting factors are produced by the liver, and present in plasma, activate one after another to form a reaction cascade; each activated cofactor activates many more molecules in next step of sequence (12 > 11 > 9>8 > 10 >prothrombin activator > thrombin > fibrin); requires calcium ions Extrinsic Pathway – (3 > 7) initiated by damaged tissue releasing thromboplastin (factor 3) to bloodstream Intrinsic Pathway – (12 > 11 >9 > 8) initiated by platelets releasing Hageman factor (factor 12) Both pathways activate factor X, leads to production of prothrombin activator  converts prothrombin to thrombin  converts fibrinogen to fibrin; positive feedback – thrombin speeds up formation of prothrombin activator Clot retraction occurs within 30minutes; growth factors secreted by platelets and endothelial cells stimulate fibroblasts and smooth muscles to multiply and repair damaged vessel;

 

Fibrinolysis – dissolution of clot after tissue repair is complete; factor 12 also speeds up formation of kallikrein enzyme  converts plasminogen to plasmin, enzyme that dissolve clot Thrombopoiesis – platelet production; stem cells produce megakaryocytes, repeatedly replicate DNA without dividing to become gigantic cell with multilobed nucleus; 100μm diameter; lives in bone marrow until blood flow splits off fragments called platelets; circulate freely for 10 days Coagulation Disorders Haemophilia – lack of factor 8; sex-linked, mainly male; cannot stop bleeding Thrombosis – abnormal clotting in unbroken vessel; thrombus/clot most likely to occur in legs of inactive people Embolus – anything that can travel in the blood and block blood vessels Thromboembolism – travelling blood clots Pulmonary Embolism – clot travelling from veins to lungs Infarction – tissue death when clot blocks blood supply to an organ Erythrocytes are the red blood cells that transport O2 from the lungs to the cell tissues, and carry CO 2 from the tissues to the lungs; does anaerobic fermentation to produce ATP; no protein synthesis or mitosis; live about a bout 120 days

Disc shaped with thick rim and thin in the middle, 7.5μm in diameter, 2μm thick; has no nucleus, DNA, mitochondria; lack of organelles allows it to maximise O 2 transfer; actin and spectrin (cytoskeletal proteins) give membrane durability and resilience so they can stretch, bend and squeeze through small capillaries; high surface to volume ratio to increase diffusion rates; Haemoglobin – protein molecule that transports respir atory gases; contains 4 α and β protein chains (globin), 4 heme groups, ferrous ion at the centre of each that easily associates and dissociates with O 2  Formation of rouleaux stacks may indicate infection, inflammatory disease or connective tissue disease Blood Types determined by surface glycoproteins and glycolipids of RBC Antigens (or agglutinogens) are complex molecules on the RBC cell membrane surface; unique to each blood type; used to distinguish self from foreign; foreign antigens stimulate an immune response; made up of carbohydrate moieties (galactose, fucose and N-acetylgalactosamine) Antibodies (or agglutinins)are proteins secreted by plasma cells, found in plasma; binds to foreign antigens and mark them for destruction; causes agglutination, clumping of RBCs, finally haemolysis; appear 2-8 months after birth; at maximum concentration at 10yo Universal Donor type O – most common blood type; lacks any antigens Universal Recipient type AB – rarest blood type; lacks A and B antibodies Rh Group – + or – agglutinogens depending on presence of D antigen; Anti D agglutinins also no usually present in individuals; may form on exposure to Rh+ blood Complications with Rh- with an Rh+ foetus; no problems with first pregnancy but activates production of Rh antibodies; during second pregnancy, Rh antibodies of mother may cross into placenta and attack fetal RBCs, causing haemolysis and anaemia Erythropoiesis – formation of red blood cells; requires vitamin B12 and folic acid for rapid cell division and DNA systhesis; vitamin C and copper are cofactors required for synthesising haemoglobin

Homeostasis stimuli for increasing erythropoiesis processes: high altitude levels, increase in exercise, loss of lung tissue in emphysema, low O2 levels aka hypoxemia Negtive feedback control – drop in RBC, drop in O2, causes hypoxemia which is detected by the kidneys; the kidneys produce erythropoietin that stimulates bone marrow to produce more RBC

 

Erythrocyte Death and Disposal  – RBCs lyse in spleen and liver; macrophages in the spleen digest the RBC bits, and separate the heme from the globin  hydrolysed back into amino acids Haeme pigment is converted into biliverdin  bilirubin  excreted in urine and faeces Ferrous ion is removed from heme, and released into the blood stream to produce transferring; stored as dietary iron; later used in bone marrow to make more RBCs Sickle-Cell Disease – hereditary haemoglobin defects; caused by recessive allele that modifies structure of haemoglobin structure; replaced amino acid glutamine with valine HbS does not bind with O2 well; RBCs become rigid, sticky and pointed at ends; RBCs clump together and block vessels, may cause intense pain; could lead to organ failure, stroke, rheumatism or paralysis Blood Pressure (mm Hg) – (BP) force per unit area exerted on the wall of a blood pressure by its contained blood;

differences in BP within vascular system provide driving force that keeps blood moving from higher to lower pressure areas Venous Pressure describes the pressure of blood in the thoracic vena cava, near right atrium; reflects amount of blood

returning to the heart and the heart’s ability to pump blood into the arterial system; non pulsatile; return aided by valves in veins, respiratory and muscular pump Arterial Pressure – pulsatile; high pressure to force blood through vascular system; normal is 120/80 Systolic Pressure – maximum pressure in an artery at the moment the heart pumps and pumps blood through the body; pressure exerted on arterial walls during ventricular contraction Diastolic Pressure – minimum pressure during relaxation and dilation of ventricles when

they’re filled with blood 

Pulse Pressure is the difference between the systolic and diastolic pressure Mean Arterial Blood Pressure – pressure that propels blood to tissues; depends on cardiac output(= heart rate x stroke volume), and TPVR (viscosity and reduced vessel diameter) MAP = diastolic pressure + 1/3 pulse pressure Mean Arterial Blood Pressure = Cardiac Output x Peripheral Per ipheral Resistance MAP = CO x TPVR Peripheral Resistance – the opposition to blood flow in vessels away aw ay from the heart; 3 variables: Blood Viscosity – RBC count and albumin concentration increase viscosity; anemia and hypoproteinemia decrease viscosity; polycythemia and dehydration increase viscosity; some elements in ciragettes increase viscosity Vessel Length – the farther liquid travels through a tube, the more cumulative friction it encounters; pressure and

flow decrease with distance; short distances don’t have a significant effect on resistance  Vessel Radius – most powerful influence on blood flow; only significant way of controlling peripheral resistance; can change with vasomotion; the larger the radius, the faster the blood flow velocity Baroreceptors are sensors in blood vessels that detect the BP to help maintain it High-Pressure Arterial Baroreceptors – located in carotid sinus and aortic arch; involved i nvolved in regulation of heart rate and blood vessel diameter through increase or decrease total peripheral resistance and cardiac output;; fast response; Baroreceptor Reflex: detects high BP  sends signal to cardiovascular control centre in medulla through to glossopharyngeal nerve (CNIX) and vagus nerve (CNX)  received by nucleus of solitary tract (NTS) in medulla Low Pressure Baroreceptors – located in walls of major veins and right and left atria; involved in regulation of blood volume slow response; Atrial or Bainbridge Reflex: responds to fullness of blood vessels (volume rather than pressure), which increases pressure in vena cavae  pressure increase in right atrium detected, signal sent to control centre to increase heart rate  reduces filling with each beat  pressure in great veins and right atrium decrease Other mechanisms to maintain BP

 

Kidney – macula densa cells in kidney activate renin secretion into the bloodstream when BP decreases  renin converts angiotensinogen, a protein, into angiotensin I  in lungs, angiotensin I is converted into angiotensin II by angiotensin-converting-enzyme (ACE)  ① signals to hypothalamus to cause person to thirst and drink liquids ② vasoconstriction of arterioles  restores fluid volume and increases BP Antidiuretic hormone (ADH) is released from pituitary gland; increases water reabsorption through kidneys Aldosterone is released from adrenal gland; increases sodium reabsorption and some water Erythropoetin (EPO) is released from kidneys; increases red blood formation in the bone; also released if O2 levels become abnormally low Atrial Natriuretic Peptides – released by atria when there is increase in blood volume and BP; increases sodium and water excretion Cardiovascular Control Centre is located in the medulla of the brainstem Cardiostimulatory Centre makes heart beat faster and stronger to increase BP Cardioinhibitory Centre slows the heart down to decrease BP Vasomotor Center – a cluster of sympathetic neurons in the medulla that controls changes in blood vessel diameter; di ameter; maintains blood vessel tone by innervating smooth muscles of blood vessels Cardiac Conduction System

Autorhythmic Cells – particular cardiac muscles cells that are self-excitable; repeatedly generate spontaneous action potentials to trigger heart contractions Sinoatrial (SA) Node – “natural pacemaker” embedded in posterior wall of right atrium, initiates heartbeat, sets heart rate; spreads signal to both atria, to AV node Fibrous Skeleton – insulates atria from ventricles Atrioventricular (AV) Node – in atrial septum; delivers electrical stimulus to ventricles via bundle branches; can beat by itself if SA node is i s damaged AV Bundle, or Bundle of His – pathways for signals from AV Node Right and Left Bundle Branches – divisions of AV bundle that enter interventricular septum Purkinje Fibres – located in the inner ventricular walls of the heart; lead l ead upward from apex spread throughout ventricular myocardium

Bachmann’s Bundle, or Interatrial band –  atrial muscles that connects right atrium to left atrium; preferential path for electrical activation of left atrium 0ms – SA node and atrial activation begins 50ms – stimulus from SA node spreads across atrial surfaces and reaches AV node 150ms – 100ms delay at AV node; atrial contraction begins 175ms – impulse travels along interventricular septum through bundles to Purkinje fibres and right ventricular papillary muscles through moderator band 225ms – impulse is distributed by Purkinje fibres and relayed throughout ventricular myocardium; atrial contraction is complete and ventricular contraction begins Action Potential Depolarisation – resting potential is at -90mv, sodium channels open and ions enter cell rapidly, increases positive membrane potential Plateau – 250ms, calcium channels open and ions enter cell while sodium channels close, maintains a positive membrane potential Repolarisation – calcium channels close, potassium channels open and ions leave the cell, membrane potential returns to negative Refractory Period – time interval of a cardiac muscle fibre when a second contraction cannot be triggered; longer than the contraction itself Electrocardiogram (ECG) – reads and puts together graph of all action potentials of nodal and myocardial cells detected, amplified and recorded by electrodes on arms, legs and chest

 

P Wave – SA node fires, atrial depolarision, atria contract QRS Complex – ventricular depolarisation, atrial repolarisation, atria relax, ventricles contract T Wave – ventricular repolarisation, ventricles relax Arrhythimia – “out of rhythm”, used to describe a

condition where heart beat becomes irregular 

Artificial Pacemakers – small battery operated device that helps heart to beat in a regular rhythm; implanted in

patients with abnormally slow heart rates; leads detect the heart’s electrical activity and sends information to the generator; information is analysed and pacemaker decides whether or not to pace; if heart rate drops to low, an electrical signal is transmitted to the heart to stimulate the heart muscle to contract Single Chamber – only 1 wire is placed into a chamber of the heart Dual Chamber – wires are placed in one atrium, one ventricle; mimics natural pacing of heart Rate-Responsive – sensors automatically automatically adjust in accordance to the person’s physical activity   Cardiac Cycle  – – period between start of one heartbeat and beginning of the next; includes contraction and relaxation

Systole – contraction; pressure rises Diastole – relaxation; pressure falls 1) 

Arterial systole begins; AV valves are open; atria contract and force blood into relaxed ventricles

2) 

Ventricles fill up to end-diastolic volume (EDV); AV valves close

3) 

Isovolumetric contraction – all 4 valves are shut very briefly

4) 

Ventricular pressure rises and exceeds pressure in arteries; semilunar valves open and blood ejected into pulmonary artery and aorta; about 60% of EDV is ejected = stroke volume (SV)

5) 

Semilunar valves close; ventricles contain the other 40% = end-systolic volume (ESV)

6)  7) 

Ventricular diastole begins; ventricular pressure is higher than atrial pressure Isovolumetric relaxation – all 4 valves are shut very briefly

8) 

Ventricular pressure decreases, atrial pressure increases; AV valves open and chambers are filled passively

Cardiac Output (ml/min) – amount of blood pumped by each ventricle in 1 minute; heart rate is number of heart beats per minute (beats/min); stroke volume is amount of blood pumped out by ventricle with each beat (ml/beat) Cardiac Reserve – difference between resting and maximal CO Factors Affecting CO CO – changes in HR and SV HR – adjusted by autonomic nervous system or hormones SV – changes in EDV and ESV; valve problems Heart Rate – Pulse – surge of pressure produced by each heart beat; can be felt by palpitating superficial artery with the fingertips; pressure wave that contracts and expands arterial walls Tachycardia – resting adult heart beat above a bove 100bpm; due to stress, anxiety, drugs, heart disease, fever, etc Bradycardia – resting adult heart beat less than 60bpm; during sleep, or due to low body temperature, well trained endurance athletes

 

Factors affecting Heart Rate Positive Chronotropic Agents – factors that increase heart rate Drugs – caffeine, cocaine, nicotine, alcohol, pseudoephedrine - Caffeine and Nicotine – increase heart beats of ectopic pacemakers Hormones – epinephrine/adrenaline, norepinephrine, thyroid hormone Negative Chronotropic Agents – factors that decrease heart rate

Calcium channel blockers, β blockers, etc  Cardiovascular Control Centre – mostly hormone related nd Increased Sympathetic Activity – stimulates release of norepinephrine (NE)  initiates a cyclic AMP 2   



messenger system  increases open state of calcium and sodium ions  increased heart rate Increased Parasympathetic Activity – stimulates release of acetylcholine (Ach)  activates G proteins   increases open state of potassium channels and closed state of calcium channels  decreased heart rate Stroke Volume – EDV minus ESV; preload, contractility and afterload EDV = end-diastolic volume; amount of blood collected in ventricle; affected by increased duration of ventricular diastole, increased venous pressure, return and blood flow = increased EDV ESV = end-systolic volume; amount of blood remaining in ventricle after contraction; affected by preload, decreased contractility, increased afterload = increased ESV Physical limits – ventricular expansion limited by myocardial connective tissue, cardiac fibrous skeleton, pericardial sac Contractility – how hard the myocardium contracts for a given preload Positive Inotropic Agents – increase contractility Hypercalcemia can cause strong prolonged contractions and even cardiac arrest in systole Catecholamines increase calcium levels Glucagon stimlutes cAMP production Digitalis increase intracellular calcium levels and contraction strength Negative Inotropic Agents – reduce contractility Hypocalcemia can cause weak irregular heartbeats and cardiac arrest in diastole Hyperkalemia reduces strength of myocardial action potentials and release of calcium into the sarcoplasm Preload – degree of ventricular stretching during ventricular diastole; volume of blood returning to the heart, directly proportional to EDV; affects ability of muscle cells to produce tension Afterload – resistance against which heart has to pump; increased by any factors that restrict arterial blod flow; as afterload increases, SV decreases Frank-Starling Law of the Heart - as EDV increases, SV increases Force of contraction is directly related to degree of stretch of cardiac muscle cells prior to contraction (preload) Ventricles tend to eject as much blood as they receive – within constraints of muscle tissue Slow heartbeat and exercise increase venous return to the heart  – increases SV Blood loss and extremely rapid heartbeat decrease SV Heart Sounds S1 – loud; produced by AV valves closing S2 – loud; produced by semilunar valves closing S3 – caused by oscilliation of blood back and forth between atria and ventricles; may indicate ventricle volume increase S4 – occurs in 40 or 50 yo because of reduced ventricular compliance, or increased resistance to ventricular filling, during atrial contraction; forceful atrial a trial contraction into hypertrophied, noncompliant ventricle will produce S4

 

Endocrine System

System includes glands, tissues and cells that secrete hormones Endocrinology – study of this system and the diagnosis and treatment of related disorders Endocrine Glands – organs that are traditional sources of hormones Hormones – chemical messengers that are transported by the bloodstream and stimulate physiological responses in cells of another tissue of organ, often a considerable distance away; extraordinarily potent chemicals; very small stimulus can produce very large effect and hence circulating concentrations and very low Hypothalamus – provides highest level of endocrine control; shaped like a flattened funnel; forms floor and walls of third ventricle of the brain; regulates primitive functions of the body from water balance and thermoregulation to sex drive and childbirth; many functions carried out by pituitary gland Hypophyseal Portal System – system of blood vessels that link hypothalamus with anterior pituitary Produce 8 hormones; 6 to regulate anterior; other 2 are stored in posterior and later released into bloodstream

TRH, CRH, GnRH and GHRH affect anterior’s secretion of TSH, PRL, ACTH, FSH, LH and GH  PIH inhibits secretion of prolactin Somatostatin inhibits secretion of growth hormone and thyroid stimulating hormone Pituitary Gland, or Hypophysis – suspended from hypothalamus by a stalk called infundibulum; i nfundibulum; located in depression of the sphenoid bone, called sella turcica; size and shape of kidney ki dney bean, 1.3cm wide Anterior or Glandular Pituitary – ¾ of gland; fleshy and glandular; contain: Acidophils stain red or orange; contain polypeptide hormones – GH and PRL Basophils stain blue; contain glycoprotein hormones – TSH, LH, FSH, ACTH Chromophobes stain very poorly; have minimal or no hormonal content; may be stem cells yet to be differentiated into hormone-producing cells Anterior lobe synthesises and secretes 6 principal hormones 2 gonadotropin hormones that target gonads Follicle Stimulating Hormone (FSH) – stimulates secretion of ovarian sex hormones, development of ovarian follicles, and sperm production Luteinising Hormone (LH) – stimulates ovulation, corpus luteum l uteum to secrete progesterone, and testes to secrete testosterone Thyroid Stimulating Hormone (TSH) – stimulates secretion of TH, which increases metabolic rate, stimulates appetite, increase growth of hair, skin, teeth, increase respiratory and heart rate Adrenocorticotropic Hormone (ACTH) – stimulates adrenal cortex to secrete glucorticoids, eg. Cortisol which stimulates fat and protein metabolism, and gluconeogenesis to help repair damaged tissues and has an antiinflammatory effect Prolactin (PRL) – stimulates mammary glands to synthesis milk after birth, or enhances secretion of testosterone by tests Growth Hormone (GH) – stimulates mitosis and cellular differentiation; has widespread effect on body tissue including cartilage, bones, muscles and fat; stimulates liver to breakdown glycogen, synthesis somatomedins which increase tissue uptake of amino acids and synthesis s ynthesis proteins; suppresses protein catabolism; increased lipid metabolism to provide energy for growing tissues Acromegaly – hypersecretion of GH in adults  thickening of bones and soft tissues, esp hands, feet and face Gigantism – hypersecretion in children Pituitary Dwarfism – hyposecretion of GH Posterior or Neural Pituitary – ¼ of gland; down growth from brain; neural composition; merely stores hormones, no synthesis; transported to posterior through axoplasmic transport Antidiuretic Hormone (ADH) – increases water retention, reducing urine volume and preventing dehydration; also a vasopression because it can induce vasoconstriction Oxytocin (OT) – released during sexual arousal and orgasm, stimulating uterine contractions and propulsion of semen; promotes feelings of sexual satisfaction and emotional bonding between partners; stimulates labor

 

contractions during childbirth; stimulates flow of milk during lactation, promoting emotional bonding between mother and infant Pineal Gland – attached to roof of third ventricle beneath posterior end of corpus callosum; shrinks after 7yo; regulates hormonal changes in sexual maturity puberty and regulates timing of puberty Melatonin – affects modulation of wake/sleep patterns (produced when it is dark, drops when it is light); helps control timing and release of female reproduction hormones Thymus – bilobed gland in mediastinum superior to heart; shrinks after puberty; site of maturation for T lymphocytes; secretes thymopoietin, thymosin and thymulin, to stimulate growth of other lymphatic organs Thyroid Gland – largest endocrine gland; two lobes and isthmus below larynx; dark reddish brown colour dur to rich blood supply Thyroxine and Triiodothyronine (T4 and T3, reference to number of iodine atoms) – increase metabolic rate, O2  consumption, heat production, appetite, growth hormone secretion, alertness and quicker reflexes Calcitonin – secreted by parafollicular when blood calcium increases; stimulates osteoblast activity and bone formation a nd antibody Hashimoto’s Thyroiditis   –– autoimmune disease in which thyroid gland is gradually destroyed by cell and mediated immune processes Endemic Goiter – dietary iodine deficiency; no TH  no feedback  increased TSH  stimulates hypertrophy

Toxic Goiter (or Grave’s Disease)   –– autoantibodies mimic effect of TSH on thyroid  hypersecretion  enlargement of thyroid gland Parathyroid Glands – four glands partially embedded in posterior surface of the thyroid Parathyroid Hormone (PTH) – promotes synthesis of calcitriol  increases absorption of calcium  decreases urinary excretion  increases bone reabsorption  increases osteoclast activity Hypoparathyroidism – underproduction of PTH; leads to low levels of calcium ca lcium  cramping, twitching, tetany Hyperparathyroidism – excess PTH secretion; could develop parathyroid tumour; bones become soft, fragile and deformed; calcium and phosphate levels increase; promotes renal calculi/kidney stone formation Adrenal Gland – sits on top of each kidney; are retroperitoneal Adrenal Medulla – inner core of the gland; mostly modified sympathetic neurons called chromaffin cells or neuroendocrine cells which have no dendrites or axons, but receive sympathetic input and release products directly into blood stream; when stimulated, release catecholamines (epinephrine and noreprinephrine) Increases alertness (fight or flight) and prepares body for physical activity; mobilises high energy fuels, lactate, fatty acids, glucose; stimulate glycogenolysis and gluconeogenesis to boost glucose levels; ; increases BP, heart rate, blood flow to muscles, pulmonary air flow and metabolic rate; decreases digestion and urine production Adrenal Cortex – thick outer layer surrounding adrenal medulla; produces steroid hormones called corticosteroids; has 3 layers: Zona Glomerulosa – thin outer layer; cells a rranged in rounded clusters; secretes aldosterone to regulate body’s electrolyte balance, sodium retention Zona Fasciculata – thick middle layer; cells arranged in fascicles separated by capillaries; capillar ies; secretes cortisol to regulate metabolism of glucose, suppresses immune system to help body adapt to stress and repair tissues Zona Reticularis – narrow inner layer; cells in branching network; secretes sex steroids like androgens, estrogen Cushing Syndrome – excess cortisol secretion; leads to hyperglycemia, hypertension, weakness, edema; rapid muscle and bone loss due to protein catabolism; abnormal fat deposition  moon face and buffalohump Adrenogenital Syndrome (AGS) – adrenal androgen hypersecretion, accompanies cushing syndrome; enlargement of external sexual organs in children and causes early onset of puberty; masculinising effects on women such as as increased body hair, deeper voice and beard growth

 

Pancreas Alpha Cells secrete Glucagon  – raises blood glucose by increasing liver glycogen breakdown (glycogenolysis); stimulates gluconeogenesis Beta Cells secretes Insulin – lowers blood glucose by increasing glucose uptake and utilisation by cells; increases glycogen production in liver and skeletal muscles Delta Cells secretes Peptide Hormone – suppresses release of glucagon and insulin; slows food absorption and enzyme secretion rate in digestive tract; stimulates fat catabolism and release of fatty acids in adipose tissue G Cells secrete Gastrin – stimulates stomach acid secretion, motility and emptying F Cells secrete Pancreatic Polypeptide  – inhibits gallbladder contraction; reduces pancreatic secretions; inhibits intestinal mobility Skin – keratinocytes convert cholesterol-like steroid into Cholecalciferol (vitamin D) using sun UV Liver – converts cholecalciferol into Calcidiol; secretes Angiotensinogen that helps in regulating BP; secretes Erythropoietin that stimulates bone marrow to produce blood; secretes Hepcidin that promotes intestinal absorption of iron; secretes IGF-I that controls action of GH Kidneys – converts calcidiol into Calcitriol to increase calcium absorption by intestines to inhibit urine loss; secretes Renin that converts angiotensinogen to angiotensin I, helps hel ps increase BP by vasoconstriction; v asoconstriction; produces Erythropoietin that stimulates bone marrow to produce blood Hormones and System Integration – most cells sensitive to more than one hormone and exhibit interactive effects or hormones Antagonistic Effects – 2 opposing hormones activate and produce weaker effects than if they were unopposed; eg. PTH and calcitonin; insulin and glucagon Permissive Effects – one hormone is needed for the other to produce its effect; eg. Epinephrine activates in presence of thyroid hormones Additive Effects – net result of two hormones is greater than if each was acting alone; eg. Enhancement of glucosesparing action of GH in presence of glucocorticoids Integrative Effects – hormones produce different but complementary effects; eg. Calcitriol and PTH Hormone Synthesis – 3 chemical classes, all are made from cholesterol or amino acids, with carbohydrates to make glycoproteins Steroids – derived cholesterol; secreted by gonads and adrenal glands; eg estrogen, progesterone, testosterone, cortisol, corticosterone, aldosterone, DHEA, calcitriol Peptides and glycoproteins – created from chains of amino acids; secreted by pituitary and hypothalamus; eg OT, ADH, releasing and inhibiting hormones, anterior pituitary hormones Monoamines (biogenic amines) – derived from amino acids; secreted by adrenal, pineal, thyroid; eg epinephrine, norepinephrine, melatonin, TH Hormone-Receptor Binding – hormones only stimulate cells with specific receptors; receptors are protein or glycoprotein molecules; act like switches swi tches turning on metabolic pathways; receptors become saturated when occupied Target Cell Sensitivity can be adjusted by changing number of receptors Up Regulation – increased number, increased sensitivity, stronger response; eg uterus cells for OT Down Regulation – decreased number, decreased sensitivity, diminished response; adiopocytes and high levels of isulin Plasma Membrane Receptors – for water-soluble hormones that cannot cross plasma membrane; acts as first messenger, relaying message to intermediary/second messenger, which then affects enzyme activity a ctivity and changes cellular metabolic reactions; eg cAMP and calcium ions; inositol phosphate (IP3) pathway; diglyceride (DAG) pathway Hormone binds to cell-surface receptor  activates a G protein  activates adenylate cyclise to produce cAMP  activates

kinases  activates enzymes to synthesis or secrete products

 

Cytoplasm of Nucleus Receptors – for lipid soluble hormones that can diffuse through the membrane Steroid hormones affect DNA transcription rate and protein synthesis; change synthesis of enzymes and structural proteins; affecting cell’s metabolic activity and structure  TH bind to receptors on mitochondria, increasing energy production; bind to receptors on nucleus, increasing metabolic activity and structure

Nervous System

Works together with endocrine system to maintain health and homeostasis; responsible for behaviours, memories and movements Neurons

Neural Tissue Neurons – cells that send and receive signals  Sensory/Afferent Neurons – transmits information to brain or spinal cord from receptors that detect changes in body and external environment Interneurons (Association Neurons) – lie between sensory and motor pathways, confined in CNS; 90% of neurons; process, store and retrieve information Motor /Efferent Neurons – sends signals to muscles and gland cells from CNS; organs that carry out effector responses Neuroglia (Glial Cells) – cells that support and protect signals Oligodendrocytes – form myelin sheaths in CNS only Ependymal Cells – line central cavities of brain; produce CSF Microglia (macrophages) – formed from monocytes; phagotise neuronal debris or invading microorganisms in infection, trauma or stroke Astrocytes – most abundant glial cell, form framework of CNS; biochemical support of endothelial cells that form BBB; contribute to BBB and regulate composition of brain tissue fluid Schwann Cells – form myelin sheaths in PNS only Satellite Cells – found in PNS; supplies nutrients to surround neurons; structural function as protective and cushioning cells Myelination – formation of myelin sheath by Schwann cells in PNS and oligodendrocytes ol igodendrocytes in CNS; surrounds axons and insulates it; increases speed of nerve impulse conduction Speed of Nerve Signals depends on fibre diameter and presence of myelin – large fibres have more SA for signals Small unmyelinated fibres = 0.5 to 2.0 m/s Small myelinated fibres = 5 to 15 m/s Large myelinated fibres = up to 120m/s Slow signals supply stomach and dilate pupil Fast signals supply skeletal muscles and transport sensory signals for vision and balance Membrane Potential – distribution of charges inside and outside the plasma membrane Ion Channels – protein complexes that allow water soluble, charged molecules to move across membrane Gated Channels – open and close in response to a stimulus, ie neuron excitability Chemical – ligand molecule binds to receptors to open channel

 

Voltage – respond to changes in membrane potential leading to open channel Mechanical – respond to physical distortion of membrane surface Leakage (nongated) channels – always open; nerve cells have more potassium than sodium leakage channels; more permeable to potassium, explaining resting potential of -70mv Resting Membrane Potential – negative ions inside, positive ions outside; concentrations are different inside and outside; extracellular fluid rich in sodium and chloride; cytosol rich in potassium, phosphate and amine acids; inward flow of sodium is slower than outward flow of potassium; Generation of an Action Potential – sequence of rapidly occurring events that decrease and eventually reverse membrane potential and then restore it to the resting state; sodium and potassium channels open in sequence; neurons send messages electrochemically (chemicals cause electrical signal) All or None Principle – stimulus reaches threshold and send signal; stronger stimulus will not cause larger impulse 1)  At resting potential of -70mv; depolarising stimulus occurs 2)  Membrane depolarises to threshold; voltage sodium gates open and sodium enters cell; voltage potassium gates open slowly 3)  Rapid sodium entry depolarises cell; reaches maximum of +30mv and sodium gates close; potassium gates open 4)  Potassium moves from cell to extracellular fluid 5)  Potassium gates remain open, but additional potassium also leaves the cell, hyperpolarising it 6)  Potassium gates close and potassium leakage decreases 7)  Cell returns to resting potential Continuous/Impulse Conduction – in unmyelinated fibres; step by step depolarisation of each portion of the length of the axolemma Saltatory Conduction – depolarisation only at nodes of Ranvier where there is a high density of voltage gated ion channels, allowing fast sodium diffusion in areas a reas between the myelin sheaths; current carried by ions flowing through extracellular fluid from node to node Stimulus Intensity – Firmer pressure generates impulses at a higher frequency and stimulates more neurons Synaptic Events – transmission of a message or nerve impulse within a neuron = action potential generation and propagation; or transfer of message between cells (from a neuron to another neuron or effector cell) = must be relayed across a synapse Synapses are functional junctions between one neuron to another, or between a neuron and an effector; there are both chemical and electrical synapses 1) Arrival of depolarisation wave at pre-synaptic terminal (knob) 2) Wave causes opening of calcium channels and calcium ions flow into the cell 3) Calcium ions promote the fusion of synaptic vesicles with the pre-synaptic membrane and secretion of neurotransmitter into the synaptic cleft (exocytosis) 4) Neurotransmitter diffuses across the synaptic cleft and binds to receptors on the post synaptic membrane 5) Binding of neurotransmitter opens ion channels on the post synaptic membrane which are usually sodium channels 6) Sodium ions flow into the cell, leading to depolarisation 7) When a depolarising post-synaptic potential reaches threshold, it triggers an action potential, usually at the axon hillock 8) Neurotransmitters are degraded by the enzyme acetylcholinesterase and reabsorbed into the pre-synaptic pre -synaptic membrane and reused 9) Neurotransmitter is formed in the cell body, transported down the axon to the knob, and packaged into vesicles

 

Axonal Transport – movement of substances after they are synthesised in cell body, ie neurotransmitters, repair proteins Slow Axonal Flow – one directional only, away from cell body, anterograde a nterograde transport; 0.5 to 10mm per day; moves enzymes and cytoskeletal components; renews work out axoplasmic components in mature neurons and a nd supplies axoplasm for regenerating and repairing neurons Fast Axonal Flow – two way flow; anterograde  – moves organelles, synaptic vesicles, calcium ions, enzymes, glucose, amino acids along surface surf ace of microtubules; 20 to 400mm per day; retrograde – returns or recycles synaptic vesicles and other materials to soma and informs soma of conditions at know Neurophysiology neaural activity and transmembrane  changes in transmembrane potential can cause muscle

 – contraction, gland secretion, or transfer of information Resting Potential – all neural activities begin when a change from resting potential Graded Potential – temporary localised change in membrane potential due to stimulus; decreases with distance from stimulus Action Potential (nerve message) – electrical event involving on location of axonal membrane; is propagated along axon surface toward synaptic terminals Synaptic Activity – release of neurotransmitters by presynaptic cell; bind to receptors on postsynaptic cell; changing permeability to certain ions and produce graded potential; when threshold is reached, action potential is generated Summation – combined effect generating a nerve impulse, when several presynaptic end bulbs release neurotransmitters at the same time Spatial – multiple synapses are active simultaneously Temporal – a single synapse fires repeatedly in succession Electrical Synapses presynaptic and postsynaptic membranes are a re locked together by gap junction; changes in potential are transferred directly between the cells; occurs in some areas of the brain, eye, ciliary ganglia of PNS; found in neural systems that require fastest possible reponse, such as defensive reflexes; faster than chemical synapses Neurotoxins Blue Ringed Octopus – toxin blocks sodium channels, causing motor paralysis and respiratory arrest within minutes Puffer Fish – toxin blocks sodium channel, prevents action potential, leads to reduced muscle contraction and death Funnel Web Spiders – toxin causes nerves to rapidly fire electrical impulses, floods synaptic gaps with neurotransmitters; overstimulates nerve, overstimulates muscles leading to muscle spasm and paralysis Botox (Botulinum Toxin) – produced by bacteria, causes serious and life threatening botulism, food poisoning; type A blocks release of neurotransmitter, unable to signal muscle it supplies, results in weakened or no contraction Myasthenia Gravis – autoimmune disorder; antibodies attack neuromuscular junction (NMJ), destruction of receptors, decreased sensitivity to neurotransmitters; result in drooping eyelids, double vision, swallowing difficulties, weak limbs and muscles, respiratory failure Brain

Gray Matter – neurons cell bodies, neuroglia, dendrites and synapses; forms cortex and nuclei deep within brain White Matter – myelinated bundles of axons; form tracts that connect parts of the brain; pathways going up and down in spinal cord Meninges- protects the CNS; meningitis (inflammation) Ventricles – contain CSF that is produced by the choroid plexus – cauliflower like growths of network capillaries in walls of ventricles; capillaries are covered by ependymal cells that from CSF from blood plasma by filtration and secretion; has ion pumps that allow them to alter ion i on concentration of CSF; ependymal cells have cilia, beat in one coordinated direction to circulate CSF around brain

 

Cerebrospinal Fluid (CSF) – watery solution similar in composition to blood plasma, contains less protein and different ion concentrations; forms liquid cushion that gives buoyancy to CNS organs; mechanical protection –  shock absorber; chemical protection – provides optimal environment for proper neuronal function; allows exchange of nutrients and wastes between blood and brain Blood Cerebrospinal Barrier – capillaries of choroid plexus are surrounded by single layer of ependymal cells which form tight junctions with adjoining cells; blood filtrate must move through these cells and be processed before it can enter ventricles as CSF; ion pumps on ependymal cells modify filtrate by actively transporting certain ions into CSF; then CSF moves through ventricles aided by long microvilli of ependymal cells; CSF is later reabsorbed into the blood stream through one way valves in large veins Hydrocephalus – condition where drainage of CSF is blocked causing increase in intracranial pressure Blood Brain Barrier – protective mechanism that helps in maintaining a stable environment for the brain; resides within endothelial cells of brain capillaries; adjacent a djacent endothelial cells come together, forming tight junct junctions ions between cells; all substances leaving or entering brain must through 2 plasma membranes and the cytoplasm of the endothelial cells Brain Stem – bridge between brain and spinal cord; relays messages between brain and motor and sensory nerves; has ha s 3 portions: Medulla Oblongata – continuation of spinal cord; ascending sensory tracts, descending motor tracts; nuclei of 5 nerves; relays information to and from cerebellum; contains cardiovascular centre that maintains heart rate and vasomotion; contains respiratory centre that controls respiration movements and timing; contains reflex centres for coughing, sneezing and swallowing Pons – one inch long; with fibre tracts ascend and descend; pneumotaxi centre – antagonises apneutistic centre by inhibiting inspiration; fine tunes respiratory rate; prevents over distension of lunds and maintains normal breathing pattern; apneustic centre – promotes inspiration by stimulating neurons in medulla; inhibits pneumotaxic, leading to increase depth of respiration, decreased respiratory rate Reticular Formation – reticular activating system – alerts cerebral cortex to sensory signals to awaken from sleep; maintains consciousness and helps keep you awake with stimuli from fr om ears, eyes, skin and muscles; involved in maintaining muscle tone Cerebellum – located behind the brain stem; responsible for motor skills such as a s movement, coordination and balance; processes information from cerebral motor cortex, proprioceptors, visual and equilibrium pathways; provides instructions to motor cortex centres that result in i n proper balance, posture and smooth coordinated skeletal muscle movement Thalamus – on top of brain stem; sensory information is sorted by thalamus, then routes it to most appropriate area of cerebral cortex; registers conscious recognition of pain, temperature and some awareness of light touch and pressure; essential role in awareness and knowledge acquisition and cognition Epithalamus – lies superior and posterior to thalamus and contains pineal gland  – releases melatonin; and habenular nuclei – involved in olfaction, emotional responses to odours Hypothalamus – inferior to thalamus; controls body activities and regulates homeostasis; controls ANS; produces hormones; regulates emotional and behavioural patterns; regulates eating and drinking through feeding centre, satiety centre, and thirst centre; controls body temperature; regulates circadian rhythms and conscious state Cerebrum – largest part of brain; right and Left halves, called hemispheres, separated by longitudinal fissure; internally, is it connected by corpus callosum, bundle of transverse white fibres Cerebral Cortex – surface layer that is 2-4 mm thick, 6 layered tissue; elevated ridges of tissues called gyri are separated by shallow grooves called sulci; deeper grooves called fissures separate large regions of the brain; composed of gray matter; contains billion of neurons; contains stellate cells (dendrites projecting in all directions), and pyramidal cells (axon passes out of these areas); role in memory, attention, perceptual awareness, thought, language and consciousness

 

Cerebral White Matter – beneath cortex; tracts connect parts of brain with itself and other parts of the nervous system Lobes: Frontal (voluntary motor function, planning, mood, smell, social judgement), Parietal (receives and integrates sensory information), Occipital (visual centre of brain), Temporal (areas for hearing, smell, learning, memory, emotional behaviour) Basal Ganglia – located deep within cerebral hemispheres (gray matter); receives input from cerebral cortex and provides output to motor parts of the cortex; helps regulate initiation and termination of movements; damage may lead to Parkinson Disease (uncontrollable shaking and stiffness) Limbic System – made up of various structures, amygdale, hippocampus, cingulated gyrus; also called emotion brain, or pleasure zone, role in emotions such as pain, pleasure, docility, affection, anger, happiness and sexual desire; some memory processing Cranial Nerves – 12 pairs of cranial nerves; I and II are called sensory nerves; III to XII have a mixture of both sensory and motor neurons; III, IV, VI, XI and XII contain mainly motor neurons I – Olfactory Nerve – transmits information from receptors in the olfactory epithelium; II  – Optic Nerve – transmits information from receptors in eye; III – Oculomotor Nerve – controls muscles for eyeballs and eyelids, constriction of pupil and lensshape; IV  – Trochlear Nerve – controls eyeball muscles; V – Trigeminal Nerve – chewing muscles; VI – Abducens Nerve – eyeball muscles; VII – Facial Nerve – muscles for facial expression, swallowing; nose, palate, lacrimal and salivary glands; VII  – Vestibulocochlear Nerve – transmits information from receptors to ears; IX  –  Glossopharyngeal Nerve – swallowing muscles and parotid gland; X  – Vagus Nerve – muscles for pharynx, larynx, glands of thoracic and abdominal cavities; XI  Accessory Nerve  neck muscles; XII  Hypoglossal Nerve  tongue muscles

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Autonomic Nervous System – operates without us being aware Sympathetic Division – activates during exertion, stress or emergency; increase mental alertness, metabolic rate, respiratory rate, heart rate, BP and muscular abilities; reduced digestive and urinary functions; energy reserves and sweat glands activated Parasympathetic Division – activates during resting conditions; reduces r educes metabolic rate, heart rate and BP and promotes digestion; conserves energy and promotes sedentary activities; increased salivary and digestive gland secretion; increase motility and blood flow in digestive tract; Spinal Cord   – – information highway between brain and body; extends through vertebral canal from fforamen oramen magnum to

L1; component of CNS; involved with involuntary reflex responses Spinal Meninges – series of specialised membranes that provide physical stability and shock absorption for spinal cord Pia Mater Layer – innermost layer; meshwork of elastic and collagen fibres; bound to underlying nervous tissue Arachnoid Mater Layer – middle layer; simple squamous epithelium (arachnoid membrane); network of collagen and elastic fibres connected to pia meter; Sub Arachnoid Space – between arachnoid and pia mater; contains CSF to act as shock absorber Dura Mater Layer – outermost layer; contains dense longitudinal collagen fibres; subdural space that separates it from arachnoid mater Epidural Space – between dura mater and vertebral canal; contains connective tissue, lymphatics, spinal nerve roots, small arteries, epidural venous plexus (network of large thin walled blood vessels) and protective adipose tissue (fat) Denticulate Ligaments – extend from pia, arachnoid to dura mater; has saw tooth pattern along length of spinal cord on both sides; prevents lateral movement of spinal cord; secures spinal cord to bony walls of vertebral column; protects spinal cord against sudden displacement, shock

 

nd

External Anatomy – extends from medulla oblongata to superior border of 2  lumber vertebra; have more nerves running to and from cervical (upper limbs and shoulders) and lumber (lower limbs and a nd pelvis) regions; nerves arising in lumbar, sacral, coccygeal regions of SC do not leave VC at the same level but exit SC as a bundle of nerves; nerve roots and called cauda equine (horses hair)  – formed by never root s caudal to the level of spinal cord termination Spinal Nerves – contains axons of both motor and sensory neurons; sensory enter CNS via dorsal, exit via ventral; paths of communication between SC and nerves supplying specific regions Doral Root – contains axons of neurons whose cell bodies are in the Dorsal Root Ganglion  – contains sensory cell bodies; each spinal segment contains one on each side Ventral Root  contains axons of motor neurons extending into periphery to control somatic and visceral effectors

 – Coverings of Spinal Nerves: Connective Tissue Endoneurium – covers each individual axon; capillaries supply axons, Schwann cells and fibroblasts Perineurium – outer covering of fascicles which contain bundles of axons Epineirium – outermost covering of entire nerve made up of dense collagen fibres; blood vessels from here continue on to form capillaries with endoneurium Reflexes   – – rapid automatic responses to specific stimuli, little variability; preserve homestasis by making rapid

adjustments in functions of organs; sensory fibres carry information from peripheral receptors to integration centre  motor fibres carry

motor commands from integration centre to peripheral effectors

Spinal Reflex – integration takes place in spinal cord Cranial Reflex – integration takes place in brain stem Somatic Reflex – contraction of skeletal muscles Autonomic (Visceral) Reflex- responses of smooth muscle, cardiac muscle and glands; not consciously perceived Reflex Arc – specific nerve impulse pathway; receptor  sensory neuron  integrating centre  motor neuron   effector Stretch Reflex feedback mechanism to control muscle length by causing a muscle contraction via muscle spindles which respond to change in muscle length; l ength; prevents injury over stretching because muscle contracts when it i t is stretched Muscle Spindles – sensory receptors of stretch reflex; intrafusal muscle fibres, surrounded by larger skeletal muscle fibres; responsible for muscle tone and contraction of entire muscle; sensory neurons surround muscle spindle and sends impulses to CNS through dorsal root; gamma motor neurons alter tension in spindle and control sensitivity of receptors Patellar Reflex – stimulated by tapping patellar tendon  receptors (muscle spindles) stimulate sensory neuron that extends into spinal cord  synapses with motor neuron via interneurons  information processed in spinal cord  motor neuron activated and action potential is generated and propagated  skeletal muscle fibres stimulated,

leading to contraction of quadriceps (knee extensors) that extend knee in a brief kick Tendon Reflex – feedback mechanism to control muscle tension by causing relaxation before muscle force becomes so great that tendons might be torn; increased tension stimulates golgi-tendon organ  nerve impulses travel along sensory neuron to spinal cord  activates inhibitory neuron  synapses to motor neuron  generates fewer impulses  muscle relaxes and relieves tension Flexor or Withdraw Reflex – contraction of flexor muscles to move a limb away from possibly dangerous stimulus; impulse travels along sensory neuron to spinal cord  interneuron excites motor neuron  flexor or hamstring muscles contract and withdraw limb to avoid damage Crossed Extensor Reflex – extension of limb to maintain one’s balance or protect self from damage  Plantar Flexion Reflex – test to detect proper foot growth in toddlers; stroking the lateral margin of the sole should make toes curl; Babinski sign – abnormal upward fanning of toes due to incomplete myelination  

 

Homeostasis

Body’s ability to detect change, activate mechanisms that oppose it, and thereby maintain relatively stable internal conditions Feedback Loops – involves a receptor to detect changes in the body; control centre that processes sensory information, and directs appropriate response; effector that carries out final corrective action to restore homeostasis Negative Feedback – mechanisms are activated to reverse changes; dynamic equilibrium, eg thermoregulation, glucose levels, BP maintenance Positive Feedback – stimulus produces response that exaggerates or enhances the change; typically occurs when a potentially dangerous or stressful process must be completed quickly; eg clotting during child labour Could be harmful during fever, as cycle continues to reinforce itself; elevates metabolic rate and accelerates tissue repair, inhibits reproduction of bacteria and viruses, promotes interferon activity to boost immune system, increases motility of WBC and proliferation of T cells; but as metabolic rate increases, body produces heat faster and body temperature rises, further increasing metabolic rate = could die if body overheats Tissues – group of cells closely associated that have a similar structure and perform a related function Epithelium – a tissue composed of cells that line cavities and surfaces surf aces of structures throughout the body; lies on top of connective tissue, separated by basement membrane; sheets of cells that over external surfaces of body; selective barrier, secreting and absorbing specific materials Protection – protect underlying tissue from mechanical injury, harmful chemicals, pathogens and excessive water loss Sensation – sensory stimuli detected by specialised cells that contain sensory nerve endings Secretion – specialised in glands to secrete specific chemical substances such as enzymes, hormones, lubricant Absorption – specialised cells in small intestine absorb nutrients from digested food and water Excretion – specialised cells in kidney excrete waste products from body and reabsorb needed materials from urine; sweat also excreted in sweat glands Diffusion – promotes diffusion of gases, liquids and nutrients thanks to thin lining Basal Surface – supportive sheet between epithelium and underlying connective tissue; contains collagen, adhesive glycoproteins called laminin and large protein-carbohydrate complexes; basement membrane is bottom reticular fibre layer containing collagen Types of Epithelial Cells: Simple Squamous Epithelium – one layer of flat cells; found f ound in lining areas where thin walls help in rapid diffusion in gases; eg lungs, capillaries Simple Cuboidal Epithelium – one layer of angular cells; secretive and absorptive functions; eg kidneys, pancreas, salivary glands Simple Columnar Epithelium – one layer of long/tall cells; extremely high secretive or absorptive areas; goblet cells inbetween produce muscus as lubricant; eg intestines Pseudostratified Epithelium – one layer of columnar cells with mismatched heights, appearance of several layers; secretes and propels mucus, may have cilia; eg respiratory tract Stratified Squamous Epithelium – multiple cell layers; eg skin Stratified Cuboidal Epithelium – sweat glands and sperm producing ducts Transitional Epithelium – found in tissues and can appear to be stratified, may be stretched to make up for water absorption; eg bladder, wreter, urethra Digitalis – slows sodium ion calcium ion antiporters, allowing more calcium to stay inside heart muscle cells, which increases the force of their contraction and thus strengthens heart beart Exocrine Glands – secrete substances onto body surface or into body cavity; eg salivary, mammary, sweat

 

Endocrine Glands – secrete product into the blood stream; either stored in secretory cells or in follicle surrounded by secretory cells; eg thyroid, pituitary, adrenal Connective Tissue – most abundant and widely distributed,; binds organs as tendons and ligaments; supports bones and cartilage, eg ear nose trachea; physical protection in cranium ribs sternum fatty cushions around eye and kidney; immune protection; movement; storaye for energy; heat production; blood Fibrous Connective Tissue Components Cells – fibroblasts produce fibres and ground substance; marcophages; leukocytes; plasma cells that synthesis disease antibodies; mast cells that are along the side of blood vessels and secrete heparin to inhibit clotting and dilates blood vessels; adipocytes that store fat Fibres – collagenous fibres that are thick, strong, tough, flexible and resist stretching; make up tendons and ligaments; reticular fibres – thing collagen fibres coated with glycoprotein and strong and form branching networks; join connective tissues to other tissues and form framework of spleen and lymph nodes; elastic fibres –  thin slender and very stretchy fibres; made of elastin and branch and rejoin each other; can stretch and recoil, found in lung tissue and arteries Ground Substance – gel like non cellular component of extracellular matrix where fibres and cells of connective tissue are embedded; contains glycosaminoglycans, proteoglycan, adhesive glycoproteins