Anatomy of the Nervous System. Brain Components

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Cameron Summers
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1 Anatomy of the Nervous System Brain Components

2 NERVOUS SYSTEM INTRODUCTION Is the master system of human body, controlling the functions of rest of the body systems

3 Nervous System CLASSIFICATION A. Anatomical division: (structural) Central Nervous System: Brain and Spinal cord Peripheral Nervous System: All peripheral nerves and Ganglia CNS receives all nervous impulses (intero-ceptive and extero-ceptive) while PNS serves to interconnect all other tissues and organs with the CNS.

4 Nervous System B. Functional division: Somatic Autonomic Each with central and peripheral divisions Somatic = Concerned with muscles, bones, joints. Skin etc Autonomic = Concerned with innervation of smooth and cardiac muscle and glands of the body.

5 Nervous System Nervous system CNS Brain and Spinal Cord PNS Cranial & Spinal Nerves Somatic Autonomic Somatic Autonomic

6 Nervous System Protection Brain and Spinal cord are delicate structures. Require protection Invested by three membranes: meninges: Pia Arachnoid Leptomeninges Dura Pachymeninges Float in CSF Encased in a bony vault.

7 Vertebral Column Bony Protection

Embryonic Development Nervous system develops from ectoderm By 3rd week, neural plate becomes a groove with neural folds along each side By 4th week, neural folds join to form neural tube lumen of

8 Embryonic Development Nervous system develops from ectoderm By 3rd week, neural plate becomes a groove with neural folds along each side By 4th week, neural folds join to form neural tube lumen of neural tube develops into central canal of S. cord & ventricles of brain Cells along margin of neural groove is called neural crest Develop into sensory & sympathetic neurons & schwann cells By 4th week, neural tube exhibits 3 anterior dilations CNS Development

10 Spinal cord Is the least modified caudal portion of the embryonic neural tube. Long cylindrical structure slightly flattened drosoventrally covered by meninges.

11 Spinal cord Extends from foramen magnum where it is continous with medulla oblongata, at the level of upper border of C1,atlas vertebra, to the lower border of L1 vertebra.

12 Spinal cord Occupies the upper 2/3 of vertebral canal (in adults). 2 % of CNS Weight is 35 grams. Length: Males: 45 cm, Females: 43 cm (length of vertebral canal is 70 cm)

13 Spinal cord Shows two swellings Cervical enlargement consisting the nerve roots supplying the upper limb that is from C5 to T1 forming brachial plexus. Lumber enlargement consisting the nerve roots supplying the lower limb that is from L1 to L4 and the sacral plexus that is L4 to S2.

terminale Filum terminale penetrates dural tube at level of S2 vertebra, invested

15 Spinal cord Lumber enlargement tapers into a conical termination Conus medullaris. A condensation of piamater extends from the conus medullaris known as Filum terminale Filum terminale penetrates dural tube at level of S2 vertebra, invested by the duramater forming Coccygeal ligament attached to the posterior surface of coccyx

segment is connected to the dorsal and ventral root filaments, 31

16 Spinal cord Gives origin to 31 pairs of spinal nerves, Portion of S.Cord to which a pair of spinal nerves is attached Spinal segment Each segment is connected to the dorsal and ventral root filaments, 31 segments, 8 cervical, 12 thoracic, 5 lumber, 5 sacral and 1 coccygeal. Disc prolapse Braceses

Spinal cord 8 Weeks 24 Weeks Newborn Adult Up to the 3rd month of fetal life, spinal cord occupies the entire length of vertebral canal Due to differential growth

17 Spinal cord 8 Weeks 24 Weeks Newborn Adult Up to the 3rd month of fetal life, spinal cord occupies the entire length of vertebral canal Due to differential growth vertebral column grows more in length At birth spinal cord lies at a higher level that is at L3 In adult between L1 tol2 vertebra and fills only upper 2/3 of vertebral canal,

Spinal cord Upper spinal nerves pass almost horizontally through their respective intervertebral foramina Lower spinal nerves pass downward

18 Spinal cord Upper spinal nerves pass almost horizontally through their respective intervertebral foramina Lower spinal nerves pass downward obliquely for some distance with lengthening of their roots, With the filum terminale forms a bunch of spinal nerves known as cauda equina {horse tail}.

23 Inferior End of Spinal Cord Conus medullaris - inferior end of spinal cord proper Filum terminale - filamentous end of meninges, "tie-down" Cauda equina - individual spinal nerves within spinal canal

24 Vertebrae and vertebral column Spinal nerves develop segmentally; that is, each spinal nerve emerges at the same level as the corresponding somite, then how the spinal nerves escape from the developing vertebrae? A related question is why eight cervical sclerotomes produce seven cervical vertebrae, whereas in the rest of the vertebral column there is a one-to-one correspondence of sclerotomes to vertebrae

25 Vertebrae and vertebral column The answer to these questions is; Sclerotomes split and recombine to produce vertebral rudiments that lie intersegmentally Each sclerotome splits into a loose cranial half and a compact caudal half

of the succeeding sclerotome The resulting

26 Vertebrae and vertebral column As the segmental spinal nerves grow out to innervate the myotomes, the caudal half of each sclerotome fuses with the cranial half of the succeeding sclerotome The resulting composite structure produces a vertebra that lies intersegmentally

Vertebrae and vertebral column Seven cervical vertebrae form from eight cervical somites because the cranial half of the C1 sclerotome fuses with the caudal half of the O4 sclerotome and contributes

27 Vertebrae and vertebral column Seven cervical vertebrae form from eight cervical somites because the cranial half of the C1 sclerotome fuses with the caudal half of the O4 sclerotome and contributes to the formation of the base of the skull The caudal half of the C1 sclerotome then fuses with the cranial half of the C2 sclerotome to form the first cervical vertebra (the atlas), and so on down the spine The eighth cervical sclerotome thus contributes its cranial half to the C7 vertebra and its caudal half to the first thoracic vertebra Atlas and Axis Disc Repair

28 Normal Scoliosis

29 Spinal cord First cervical nerve emerges between atlas and occiput, 8th cervical root between C7 and T1 intervertebral foramina. Remaining spinal nerves emerges below the vertebra of their same number. Dorsal root fibers are usually absent in C1 and coccygeal roots. Ruptured Disc

Spinal cord Each root is attached to the

32 Spinal cord Each root is attached to the cord by a series of rootlets to corresponding segment of cord. Each posterior nerve root has a posterior root ganglion with pseudounipolar cells which gives T shaped peripheral and central nerve fibers.

Spinal cord Anterior root have cell bodies in anterior gray horn & carries impulses away from C.N.S, such fibers are called efferent fibers (motor to sk.

33 Spinal cord Anterior root have cell bodies in anterior gray horn & carries impulses away from C.N.S, such fibers are called efferent fibers (motor to sk. ms for contraction). Posterior have cell bodies in the ganglion and carries impulses to C.N.S with afferent fibers sensation of pain, touch,temperature and vibration (PTTV)

Spinal cord Topography; Incompletely divided into two halves by an

Anterior median fissure (crack or split or cleft) is a deep groove (3 mm)

34 Spinal cord Topography; Incompletely divided into two halves by an anterior median fissure and a posterior median sulcus. Anterior median fissure (crack or split or cleft) is a deep groove (3 mm) in the midline, lined by piamater, does not reaches central gray commissure. Posterior median sulcus is a shallow, narrow midline sulcus and is continous with a septum of neuroglial tissue, Posterior median septum which extends upto the gray matter.

35 Cross-Sectional Anatomy of the Spinal Cord Central area of gray matter shaped like a butterfly and surrounded by white matter in 3 columns

Spinal cord Lateral to post median sulcus on each side lies a

Lateral to anterior median fissure on each side lies a less

36 Spinal cord Lateral to post median sulcus on each side lies a posteriolateral sulcus, close to dorsal roots entry zones. Lateral to anterior median fissure on each side lies a less distinct anterolateral sulcus corresponding to attachment of ventral roots. In upper thoracic and cervical regions there is a less definite post. Intermediate septum which divide Post. funiculus into 2 white columns.

ramus passes backwards supplying ms. and skin of back, Ant.

38 Spinal cord After emerging from the intervertebral foramen each spinal nerve divides into a large Anterior ramus and a smaller posterior ramus. Post. ramus passes backwards supplying ms. and skin of back, Ant. ramus passes anteriorly supplying muscle and skin of antero-lateral body wall and all muscle and skin of limbs.

39 Spinal cord Anterior rami joins at roots of limbs to form nerve plexus i.e. Cervical & brachial plexuses at root of upper limb while lumber & sacral plexus at root of lower limbs.

40 Spinal cord Surrounded by three membranous covering called Meninges, which are from the inside Piamater, Arachnoid & Duramater mater. Subarachnoid space has CSF which gives protection to the cord.

41 Spinal cord Spinal cord is anchored to dural tube by a series of flattened bands of piamater (epipial tissue) known as Denticulate ligaments.

42 Spinal cord Each ligament is of triangular shape with its base arising from pia mater between anterior and posterior roots and its apex attached to arachnoid and inner surface of dura mater Pia mater Arachnoid Dura mater

Human Anatomy. Spinal Cord and Spinal Nerves

Human Anatomy. Spinal Cord and Spinal Nerves Human Anatomy Spinal Cord and Spinal Nerves 1 The Spinal Cord Link between the brain and the body. Exhibits some functional independence from the brain. The spinal cord and spinal nerves serve two functions: