Central nervous system

During my 1st &2nd year of residency period , i used to teach Anatomy and Orthopaedics for foreign undergraduate medical students. At last year i taught Neurology for one batch. so i posted some of my collections for competely educational purpose coz i believe in knowledge ...inseted of deleting these ppts , they may me useful for others so i shared it ....

1. Central nervous system (BRAIN AND SPINAL CORD) Dr sunil pahari , 3 rd year resident Yangtze university , china

2. Spinal cord It is elongated, slightly flattened dorsoventrally , located in upper 2/3 rd of spinal canal. It is 42-45 cm long in adults with maximum transverse diameter being 10-12 mm. Starts or continuous with brain stem and ends at Conus medullaris at the level of L1. Conus medullaris is conical shaped it tapers into filum terminale consisting of pia matter and neuroglial elements . Protected by vertebras, Meninges and a cushion of CSF

3. Enlargement of spinal cord In thoracic region it is almost circular. In cervical and lumbosacral area it is enlarged due to greatly increased nervous neurons in number. The cervical enlargement includes segments C4-T1 with most of the spinal nerves forming brachial plexus Segments L2-S3 are included in lumbosacral enlargement and the corresponding nerves constitute most of lumbosacral plexuses.

4. External Longitudinal fissures and sulci Anterior median (ventral) fissure Posterior median (dorsal) sulcus Dorsal and ventral nerve root Lateral sulcus

5. Segments of spinal cords The part of spinal cord associated with emergence of a pair of spinal nerves is called a segment of spinal cord. Spinal cord is divided into 31 segments 8 cervical 12 thoracic 5 lumbar 5 sacral 1 coccygeal They vary in length and are about twice as long in the mid thoracic region as in cervical or upper lumbar area. There are no sharp boundaries within them

6. Vertebral Level of spinal cord segments In the third month of fetal life the spinal cord fills the length of vertebral canal but from then on vertebral column grows more rapidly than the spinal cord. At birth spinal cord extends to L3 while in adults it ends at the lower border level of body of L1 . It is important in surgery. A dorsal and ventral root unite to form a spinal nerve which emerge from vertebral canal via corresponding Intervertebral foramina. Lumbar and sacral roots descend for a considerable distance in subarachnoid space before reaching their respective Intervertebral foramina. The large number of lumbosacral roots surrounding the filum terminale is known as cauda equina .

7. Anatomic relationship of spinal cord with vertebral body in adults

8. Lumbar puncture

9. Internal Structure of Spinal Cord Grey matter The Grey matter is rich in nerve cell bodies, which form longitudinal column along the cord Its form and quantity varies as its proportion to white matter is greatest in lumbosacral and cervical region. In transverse section, the column form a “H” –shaped appearance in the central regions of the cord.

10. Columns Of Gray Matter and Central Canal It consists of the cell columns or horns Around the central canal is the grey commissure , connecting the grey matter of two sides. It encompasses the central canal , which is lined with ependymal cells and filled with CSF. It opens into inferior portion of 4 th ventricle. Canal usually disappears in adults except at cervical level. The Horns: The posterior horn extends posterolaterally , Somatic sensory nucleus . The anterior horn extends anterolaterally , Somatic motor nucleus . Lateral horn b/w the anterior and posterior from T1 to L3 (anterior portion is General visceral motor; posterior portion is General visceral sensory)

11. Laminae in Gray Matter Based upon the cytoarchitecture of neuronal cell bodies, a cross section of gray matter is classified into ten Rexed’s Laminae They are: Lamina I Posteromarginal Nucleus Lamina II Substantia Gelatinosa of Rolando Lamina III Lamina IV, V, VI ----- Nucleus Proprius Lamina VII - Intermediate Gray - Intermediolateral cell column (ILM) - Clarke’s column (Nucleus dorsalis ) - Intermediomedial cell column (IMM) Lamina VIII Lamina IX ---------- Anterior Horn (Motor) Cell Lamina X ----------- Gray Commissure

12. White matter Surrounds the gray matter and is rich in nerve cell processes, which form large bundles or tracts that ascend and descend in the cord to other spinal cord levels or carry information to and from the brain. It consists of ascending ,descending fibers (tracts), and fasciculus proprius It is customary to divide spinal cord into three pairs of funiculi . The posterior funiculus lies between the posterior horn and posterior median septum. The lateral funiculus lies between the dorsal and ventral horns. The anterior funiculus lies between the anterior median fissure and the emerging ventral rootlets. Anterior to the grey commissure is the ventral white commissure . It connects the white matter on both sides.

13. Neural pathways In general, neural pathway (neural tractor fasiculi ) indicates the functional fiber bundles having the same origin, course and termination. Serve as to join the spinal cord with the brain. Long tracts connect the spinal cord with the brain Ascending tracts carry sensory impulses from spinal cord to the brain. Descending tracts carry the motor impulses from the brain to spinal cord. Long tracts tend to be located peripherally, while shorter propriospinal tracts tend to be situated adjacent to gray matter.

14. Fasciculus propius Ascending and descending association fiber systems of the spinal cord which lie deep in the anterior, lateral & posterior funiculi adjacent to the gray matter. These neurons are confined to spinal cord and constitute the propriospinal or intersegmental tracts. Mostly they are located in laminae V-VIII. Fasciculi proprii aka Flechsig's fasciculi or Ground bundles consist of anterior, lateral & intersegmental fasciculi

15. Tracts of the Spinal Cord Fasciculus Gracilis Fasciculus Cuneatus Tractus spinocerebellaris dorsalis Tractus corticospinalis lateralis Tractus spinothalamicus lateralis Tractus spinocerebellaris ventralis Tractus rubrospinalis Tractus spinotectalis Tractus corticospinalis anterior Tractus olivospinalis Tractus spinoolivaris Tractus tectospinalis Tractus reticulospinalis Tractus vestibulospinalis Tractus spinothalamicus anterior Raphe-spinal & Hypothalamospinal fibers

16. Ascending tracts A . Spinothalamic tract B. Dorsal / Posterior column C. Spinocerebellar tract

17. Ascending Tract Dorsal column (Fasciculus gracilis and cuneatus ) Modality : position and vibration sens. They ascend without crossing in posterior funiculus of spinal cord to lower brain stem. Fasciculus gracilis : , conducts lower half of body. I Fasciculus cuneatus : lies between fasciculus gracilis and dorsal gray column, transmits input from upper half of body . The posterior column contains fibers from all segments of ipsilateral half of the body arranged in an orderly fashion from medial to lateral, called as somatotopic organization

18. Spinothalamic tract Modality : Pain & Temperature Sensation, Touch. Anterior spinothalamic tract : located in anterior funiculus . Lateral spinothalamic tract : located in lateral funiculus .

19. Spinocerebellar tract The  spinocerebellar tract  is a set of  axonal  fibers originating in the spinal cord and terminating in the  ipsilateral cerebellum . function- co ordination of movement. Posterior spinocerebellar tract : Anterior spinocerebellar tract :

20. Descending Tracts corticospinal tract Important for controlling of voluntery movement. This system arises from cells in precentral , motor cortex , the postcentral gyrus and adjacent parietal cortex descends throughout the internal capsule and brain stem . It divides into three tracts: Lateral corticospinal tracts : 75- 90% of fibers. Anterior corticospinal tracts Anterolateral corticospinal tracts of Barnes : uncrossed corticospinal fibers of lateral tract

21. Function of Corticospinal Tract Lateral tract control distal limb muscles of hand and foot Anterior tract . It also projects to cervical and upper thoracic spinal cord and thus may be preferentially involved in control of neck, shoulder and upper trunk muscles. Anterolateral tract provide synaptic input to lower motor neurons controlling axial muscles involved in maintaining body posture.

22. Reticulospinal tract- The reticulospinal tract that descends from the reticular formation( a diffuse network of nerve pathways in the brainstem connecting the spinal cord, cerebrum, and cerebellum, and mediating the overall level of consciousness. ) in two tracts to act on the motor neurons supplying the trunk and proximal limb muscles. Rubrospinal tract- controlling limb muscle and regulating voluntary movement. Vestibulospinal tract- maintaining balance tectospnal tract- visual and auditory stimulation .

23. brain

24. Brain stem The major divisions of the brainstem: medulla oblongata , the pons and midbrain It is stalk like in shape and connects the narrow spinal cord with expanded forebrain The superior boundary is optic tract while its inferior boundary is upper border of first cervical nerve roots. Three important functions Serve as conduct for tracts, connecting brain and spinal cord. Contains important reflex centers associated with CVS and control of respiration, also associated with control of consciousness. Contains important nuclei of cranial nerve III through XII

25. Medulla oblongata The medulla oblongata (or medulla) is located in the hindbrain, anterior to the cerebellum. The medulla oblongata is a cone-shaped neuronal mass responsible for multiple autonomic (involuntary) functions ranging from vomiting to sneezing. The medulla contains the cardiac, respiratory, vomiting and vasomotor centers and therefore deals with the autonomic functions of breathing, heart rate and blood pressure .

26. It connects pons with spinal cord. The junction b/w medulla and spinal cord is at the level of foramen magnum .It is conical in shape, broad extremity being directed superiorly. The central canal of spinal cord continues upward into lower half of medulla, in the upper half it expands as the cavity of 4 th ventricle . Anterior median fissure divides medulla into Right and Left half symmetrically . Pyramid is located beside the Anterior median fissure, Olive is located lateral to the Pyramid which are oval elevations produced by the underlying inferior olivary nuclei. Posterior to olives are inferior cerebellar peduncles which connect medulla to cerebellum. Rootlets of Hypoglossal nerve emerge from between the Pyramid and Olive In the groove b/w the olive and inferior cerebellar peduncle emerge the roots of Glossopharyngeal , Vagus and Accessory emerge from superior to inferior. The posterior surface of superior half of medulla forms the lower part of floor of 4 th ventricle(rhomboid fossa) while posterior surface of inferior half is continuous with posterior half of spinal cord. On each side of midline there is gracile tubercle and lateral to it is cuneate tubercle . Superior to gracile tubercle is inferior cerebellar peduncle.

27. pons Pons is convex and is continuous laterally with the cerebellum . It connects medulla oblongata to midbrain. It is about 2.5 mm long It is superior to medulla and is separated by Pontomedullary sulcus. Ventral surface of pons is closely associated with four pairs of cranial nerves Ⅴ, Ⅵ, Ⅶ, Ⅷ Three pairs of cranial nerves Ⅵ,Ⅶ,Ⅷ emerge from the Pontomedullary sulcus . The posterior surface of pons is hidden from view by cerebellum. It forms upper half of floor of 4 th ventricle and is triangular.

28. midbrain The midbrain is smallest and least differentiated brain stem segments. It connects pons and cerebellum with forebrain. It is traversed by a narrow channel, the cerebral aqueduct which is filled with CSF. On posterior surface Four rounded eminences are arranged in pairs, are called superior and inferior colliculi . ( Quadrigemina corpora). The superior colliculi are associated with the optic system , The inferior colliculi are associated with the auditory pathway . Cranial nerve Ⅳ ( trochlear nerve ) emerges from the midbrain. On the dorsal surface of brain stem, there are pairs of superior, middle and inferior peduncles which connect brainstem with cerebellum. Oculomotor nerve emerging from the medial to the cerebellar peduncle.

29. Rhomboid fossa The anterior part of the  fourth ventricle  is named, from its shape, the  rhomboid fossa , and its anterior wall, formed by the back of the  pons  and  medulla oblongata , constitutes the floor of the fourth ventricle.

30. Internal structure Compared with spinal cord, the internal structure of brain stem appears the following characters ： 1. The structure of medulla oblongata’s inferior part is similar to spinal cord. The central canal still remains . 2. The gray matter of brain stem don’t continue and form gray column which run lengthwise through the total length of brain stem like that in spinal cord, but get together forming all kinds of nucleus separated with each other . 3. The nucleus groups of gray substance of brain stem all link with cranial nerve basically . 4. it contains many important nuclear groups of vital center , such as center of heartbeat, blood pressure and respiratory.

31. Grey matter of brain stem 1.Nuclei of cranial nerves 2.non-cranial nerves nuclei 3. relay nucleus 4. reticular nucleu somatic motor fiber visceral motor fiber visceral sensory fiber somatic sensory fiber 1. nuclei of cranial nerves （ 1 ） general somatic motor nuclei (4 pairs) * dominate skeletal muscle （ lingual muscle ， extraocular muscles ） nucleus of oculomotor nerve nucleus of trochlear nerve nucleus of abducent nerve nucleus of hypoglossal nerve

32. （ 2 ） special visceral motor nuclei (4 pairs) - Motor nucleus of trigeminal nerve -Nucleus of facial nerve -Nucleus ambiguus ( send fiber to glossopharyngeal, vagus and accessory) -Accessory nucleus ( supply SCM muscle and trapezius) （ 3 ） general visceral motor nuclei (4 pairs) Dominate smooth muscle 、 cardiac muscle and glands -accessory nucleus of oculomotor nerve -superior salivatory nucleus -inferior salivatory nucleus -dorsal nucleus of vagus nerve

33. （ 4 ） general and special visceral sensory nucleus (1 pair) Receives visceral afferent fibers from the f acia l , glossopharyngeal and vagus nerves, which enter the brain stem by passing through the posterolateral sulcus . Nucleus of solitary tract

34. Non cranial nerve nuclei Gracile and cuneate nuclei- touch and vibration Inferior olivery nuclei - give olive cerebellar fiber which take part in controlling and regulating movement . Pontine nuclei- relay station for cerebral cortex to cerebellum. Nucleus of inferior colliculus - relay station for auditory pathway. Nucleus of superior colliculus - receive fiber from optic tract and visual cortex . pretectal nucleus – receive fiber fron retina through optic tract . Related to the pupillary light reflex . Red nucleus- take part in somatic movement . Substantia niagra – release of dopamine , tremor, parkinsons dideases .

35. 1 . long ascending tracts (1) medial lemniscus - gracile and cuneate nuclei → ventral posterolateral nuleus of thalamus Conducting proprioceptive impulses . (2) spinothalamic lemniscus - Conducting the impulses of pain , thermal and tactile sensations from opposite side of body. (3) lateral lemniscus - Cochlear nuclei → trapezoid body → inferior colliculus → nucleus of medial geniculate body Conducting the auditory senses on both sides. (4) trigeminal lemniscus - Conducting the tactile, pressure, pain and thermal impulses of head and face of the opposite side. (5) medial longitudinal fasciculus – extraocular muscle , coordinate eye movement 2 . long descending tracts pyramidal tract 1. corticospinal tract 2 . corticobulbar tract tectospinal tract- the  tectospinal tract  (also known as colliculospinal   tract ) is a nerve pathway that coordinates head and eye movements. Voluntary movement of skeletal muscle

36. Reticular formation The  reticular   formation   is a set of interconnected nuclei that are located throughout the brainstem. The  reticular   formation  is not anatomically well defined because it includes neurons located in diverse parts of the  brain . Traditionally the nuclei are divided into three columns In the median column – the raphe nuclei In the medial column – gigantocellular nuclei (because of larger size of the cells) . In the lateral column – parvocellular nuclei function Somatic   motor  control – Cardiovascular control – Pain modulation Sleep and consciousness – . Habituation

37. cerebellum The cerebellum ( little brain) though small in size , serve important functions for maintaining tone ,posture and equilibrium of the body . it is situated in posterior cranial foss behind the pons and medulla. EXTERNAL FEATURES: Two cerebellar hemisphere united by median vermis each hemisphere is divided into three lobes: anterior , middle/ posterior, flocculonodular lobe. PARTS OF CEREBELLUM Horizontal fissure , primary fissure. Uvulonodular fissure.

38. Morphological and functional division of cerebellum 1 . Archiocerebellum - it is made up of flocculonodular lobe and lingula.it controll the bilateral movement used for locomotion and maintanance of equilibrium. 2. paleocerebellum - it is made up of anterior lobe ,pyramid and uvula. Its connection are chiefly spinocerebellar . It controls tone, posture, and crud movement of limb. 3. neocerebellum - made up of posterior middle lobe. It is concerned with regulation of fine movement.

39. Ventricular system

40. DIENCEPHALON Between the brain stem and the hemispheres of the cerebrum -dorsal thalamus -hypothalamus - Metathalamus ( MGB & LGB) - Epithalamus (pineal BODY) - subthalamus (ventral thalamus)

41. THALAMUS Large mass of grey matter situated in the lateral wall of third venticle . The grey matter is divided to form several nuclei. anterior nuclei , medial nuclei , ventral nuclei, intralaminar nuclei . - proprio ceptive impulses ascend throught it . METATHALAMUS Medial geniculate body - auditory impulse to cerebral cortex lateral geniculate body - visual pathway to occipital cortex

42. thalamus

43. hypothalamus It lies below the dorsal thalamus and forms the floor and inferior part of lateral wall of third ventricle. When observeed from below ,hypothalamus is seen to be related to the following structure from anterior to posterior – optic chiasma tuber cinerium infundibulum mamillary body Function - endocrine fxn , neurosecretion , tempreature regulation, regulation of food and water intake, emotion fear , pleasure reward. Paraventricular nucleus supraoptic nucleus

44. Telencephalon ( cerebrum) Largest part of brain . Cerebrum is made up of two hemispheres which are incompletely seperated from each other by median longitudinal fissure . the hemisphere connected together by corpous callosum EXTERNAL FEATURE Three surface- superiolateral , medial ,inferior four border- superomedial , inferiolateral,medialorbital , medial occipital Three poles – frontal, occipital , temporal four lobes – frontal ,parietal, temporal, occipital

45. Sulcus and gyrus of cerebrum

46. Limbic system

47. Cerebral cortex The  cerebral cortex  is the cerebrum's (brain) outer layer of neural tissue in humans and other mammals. It is divided into two cortices, along the sagittal plane: the left and right cerebral hemispheres divided by the medial longitudinal fissure. The cerebral cortex plays a key role in memory, attention, perception, awareness,  thought,language , and consciousness . Divided into 6 layers . molecular external granular external pyramidal Internal granular Internal pyramidal polymorphic

48. Functional localization of cerebral cortex

49. A ) primary somato sensory area- it occupies the postcentral gyrus and posterior part of para centra gyrus . B) primary motor area – it is located into pre central gyrus .

50. Medullary area A.. Corpus callosum - is the largest commisure of the brain which connect two cerebral hemisphere. 4 parts - rostrum ,genu , trunk and splenium . Function- help in coordinating activity in two hemisphere. B.. Anterior commisure C.. fornix

51. Basal ganglia A region of the base of the brain that consists of three clusters of neurons ( caudate nucleus , putamen , and globus pallidus ) that are responsible for involuntary movements such as  tremor , athetosis , and chorea. The basal ganglia are abnormal in a number of important neurologic conditions, including  Parkinsons disease  and  Huntington's disease . Corpus striatum= putamen + caudate Corpous lentiform = putamen + gp