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Central Nervous System Brain & Spinal Cord

The Brain • Subdivided into forebrain, midbrain & hindbrain • Forebrain is subdivided into cerebral hemisphere (telencephalon) & diencephalon (containing thalamus & hypothalamus) • Midbrain containing mesencephalon • Hindbrain is subdivided into pons, medulla oblongata and cerebellum • Mesencephalon, pons & medulla oblongata  Brainstem

Contoh embrio 2 bln

Cerebral Hemisphere • The cerebral hemisphere has a layer of grey matter on its external surface, cerebral cortex, & white matter in the inferior in which there are nuclei forming basal ganglia • The cavity of cerebral hemisphere is lateral ventricle • The corpus callosum which is seen between the two hemispheres carries commissural fibres linking one hemisphere to the other

The Cerebral Hemisphere is divided into 4 lobes : 1. The frontal lobe lies in the anterior cranial fossa, & its anterior end is the frontal pole 2. The temporal lobe lies in the middle cranial fossa, with an anterior end the temporal pole & an upturned projection on its medial surface, the uncus 3. The parietal lobe lies above the temporal lobe between the frontal & the occipital lobes 4. The occipital lobe lies above the tentorium cerebelli, & its posterior end is the occipital pole

Basal Ganglia • These nuclei are situated deep in the cerebral hemisphere & consist of corpus striatum (containing caudate nucleus, putamen & globus pallidus) & claustrum & amygdala • The putamen and globus pallidus are together known as lentiform nucleus • The lentiform nucleus is separated from thalamus & caudate nucleus by internal capsule

Basal Ganglia (..cont.) • The caudate nucleus & putamen receive their afferent fibres mostly from cerebral cortex & thalamus & send their efferents to globus pallidus • Efferents from globus pallidus go to thalamus, substantia nigra, red nucleus & reticular formation in the brainstem • Basal ganglia & their connections form the major part of the extrapyramidal system

Diencephalon •  the middle portion of the forebrain • It consists of thalamus, hypothalamus & 3rd ventricle • A faint groove runnning from interventricular foramen to cerebral aqueduct separates thalamus from hypothalamus • The thalamus is the major relay centre in sensory pathway • Most sensations are carried from lower levels through various sensory tracts to thalamic nuclei, from where they are relayed to the sensory cortex • The hypothalamus, lying antero-inferior to thalamus, is coordinating area for visceral fx, it also contains centres for endocrine fx

Midbrain • The midbrain connects diencephalon to the pons & contains a small canal, the cerebral aqueduct (which extends from 3rd ventricle to 4th ventricle) • The part behind the aqueduct is tectum containing superior & inferior colliculi, which are respectively connected to visual & auditory pathways • The 2 cerebral peduncles lying in front of the aqueduct are further divided into tegmentum & basis pedunculi by substantia nigra • The basis pedunculi contain descending fibre tracts which are continuations of the internal capsule • The tegmentum has ascending tract as well as nuclei for oculomotor & trochlear nerves • The oculomotor nerve nuclei are situated at the level of superior colliculus & trochlear nerve nucleus at the level of inferior colliculus • The substantia nigra is connected to corpus striatum, providing dopaminergic innervation

Midbrain (..cont.) •  is contained in the gap between the free border & the tentorium cerebelli (the tentorial notch) • An increase in cranial pressure above or below the tentorium can displace the midbrain & compress the structures surrounding it against the unyielding tentorium • The temporal lobe can be compressed & the uncus can herniate through the tentorial notch • Supratentorial lesions raising the intracranial pressure often compresses the oculomotor nerves at this level.

Hindbrain • The hindbrain lies below the tentorium cerebelli in the post cranial fossa • Pons & medulla obl. lie on the clivus & extend from the mindbrain downwards where it passes through the foramen magnum to become continuous with the spinal cord • The cerebellum projects posteriorly, occupying most of the post cranial fossa • The 4th lies between the brainstem & cerebellum

Hindbrain (..cont.) • The anterior part of the pons contains fibres largely composed of those descending from the higher centres to synapse in the pontine nuclei • These fibres are relayed to cerebellum as middle cerebellar peduncles • The rest of the pons (the pontine tegmentum) contains a number of ascending & descending tracts as well as nuclei of the trigeminal, abducens, & facial nerve & reticular formation • Facial colliculus is a bulge at the posterior aspect of the pons, where facial nerve fibres wind round the abducens nerve nucleus • Most laterally in the pons is the nucleus complex associated with the vestibulocochlear nerve

Brainstem

Medulla Oblongata • The medulla extends from the pons downwards for about 2,5 cm, where it passes through the foramen magnum to become continuous with the spinal cord • The anterior surface of the medulla is grooved by an anteromedial sulcus on either side of which are two elevations, the pyramids • The pyramid contains the corticospinal fibres a large proportion of which decussate at the lower part of the medulla in the pyramidal decussation • Lateral to the pyramid is another bulge, the olive, which contains inferior olivary nucleus, which relays fibres to cerebellum • The groove between pyramid & olive contains the rootlets of hypoglossal nerve which originate from hypoglossal nerve which originate from hypoglossal nucleus in the substance of medulla • Posterolaterally the medulla has the inferior cerebellar peduncle which connects the medulla to the cerebelum • The sulcus between inferior cerebellar peduncle & olive has the 9th, 10th, 11th cranial nerves, the nuclei of these are also seen in the medulla

Cerebellum • The cerebellum is the largest part of the hindbrain • It is made up of 2 lateral cerebellar hemispheres separated by the vermis • The cerebellum is connected to the brainstem by the 3 pairs of cerebellar peduncles • The superior cerebellar peducles connect the cerebellum to the midbrain & contain efferent fibres from cerebellum to midbrain & thalamus • The middle cerebellar peduncles connect pons & cerebellum & contain the axons of pontine nuclei relaying impulses from the higher centres to cerebellum • The inferior cerebellar peduncles form the connection between medulla obl. & cerebellum & carry fibres connecting vestibular nuclei, spinal cord & inferior olivary nuclei to the cerebellum

Cerebellum • The most anterior & caudal part of the lateral lobe is the flocculus attached to the nodule in the midline • The flocculonodular lobe is an important part in the vestibular system, which maintains balance • The bulge of the lateral lobe that projects inferiorly posterolateral to the medulla obl. is the tonsil • In cases where there is raised intracranial tension, the tonsils can herniate into the foramen magnum & compress medulla obl. following a lumbar puncture

Meninges • The 3 layers of the meninges are duramater, arachnoid mater, & piamater • The 3 meningeal spaces are extradural (epidural), subdural & subarachnoid space • The epidural space between the cranial bones & the endosteal layer of dura; this is a potential space which becomes a real space when there is an extradural haemorrhage from a torn meningeal vessel • The subdural space is a potential space that may enlarge after head injury • The subarachnoid space between the arachnoid & pia, which contains CSF & the blood vessels of the brain

Spinal Cord

Anatomi Medula Spinalis • Medula spinalis org dws berakhir pd L-1 sbg Conus medularis, di bwh level ini tdp Cauda equina • Dr byk traktus pda medula spinalis hanya 3 yg dpt diperiksa scr klinis: Tr Corticospinalis, Tr Spinothalamicus, Kolum Posterior

Spinal Cord Tracts • • • • • • • • • • •

Lateral spinothalamicPain and temperature Anterior spinothalmicPain and temperature Fasciculus gracileTouch, pressure and conscious muscle joint sense Fasciculus cuneateTouch, pressure and conscious muscle joint sense Dorsal spinocerebellarProprioception Ventral spinocerebellarProvide input to the cerebellum Lateral corticospinalVoluntary skilled movement of trunk and hind limbs Ventral corticospinalVoluntary skilled movement of forelimb TectospinalReflex postural movement in response to visual stimuli Rubrospinal Facilitate activity of flexor muscles and inhibits extensors Vestibulospinal tractFacilitates activity of extensor muscles and inhibition of flexor muscles under the influence of the ear and cerebellum in maintenance of balance

1. Fasciculus gracilis 2. Fasciculus cuneatus 3. Posterior (Dorsal) spinocerebellar 4. Lateral corticospinal 5. Lateral spinothalmic 6. Anterior (Ventral) spinocerebellar 7. Rubrospinal 8. Spinotectal 9. Anteroror (Ventral) corticospinal 10. Olivospinal 11. Spinoolivaris 12. Tectospinal 13. Reticulospinal 14. Vestibulospinal 15. Anterior (Ventral) spinothalmic

Tr Corticospinalis • tdp pd segmen posterolateral medula spinalis • fx utk mengontrol kekuatan motoris pd sisi yg sama pd tubuh • dpt diuji dg kontraksi otot volunter atau respon involunter thd stimulus nyeri

Tr Spinothalamicus • Tdp pd daerah anterolateral medula spinalis • Mentransmisikan sensasi nyeri & temperatur dr sisi yg berlawanan pd tubuh • Dpt dilakukan tes dg pin prick & raba halus

Kolum Posterior • Membawa proprioseptif, vibrasi & sensasi raba halus dr sisi yg sama pd tubuh • Diuji dg rasa posisi pd jari atau vibrasi dg menggunakan garpu tala • Bila tdk tdp fx, baik mot m/ sens, dikenal sbg complete spinal cord injury • Sacral sparing mgkn hanya satu-satunya tanda fx yg tertinggal, didemonstrasikan dg msh adanya persepsi sensoris di daerah perianal & / kontraksi volunter sfingter rektal

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