The nervous system is divided into the central nervous system (CNS) and peripheral nervous system (PNS). The CNS contains the brain and spinal cord, while the PNS contains nerves that connect the CNS to sensory organs and effector organs. The basic functional unit of the nervous system is the neuron, which transmits electrochemical signals. The nervous system also contains neuroglial cells that provide support to neurons. Sensory neurons carry signals to the CNS, motor neurons carry signals from the CNS, and interneurons connect sensory and motor neurons within the CNS.

1. NERVOUS SYSTEM
by
Aswani Clevin

2. introduction
• Neuroscience is scientific study of the nervous
system combining physiology, anatomy, molecular
biology, developmental biology, cytology, computer
science and mathematical modeling to understand
the fundamental and emergent properties of
neurons and neural circuits.
• Neuroanatomy is study of the structural aspects of
the nervous system correlating them with their
function.

3. Division of the nervous system

4. Definition of terms
• Neurone:- structural & functional unit of the nervous system
• Stimuli:- change in internal & external environment that may or may not cause change.
• Receptor:- sensory end point that receives stimuli & converts it to electrical impulses
that the body can understand.
• Ganglion: group of cell bodies in the Peripheral nervous system
• Nuclei:- group of cell bodies in the central nervous system.
• Nerve:- group of axons in the peripheral nervous system.
• Tracts:- group of axons in the central nervous system.
• Ramus: a branch of nerve.

5. • Nerve plexus: serves as an area where spinal nerves come together, are sorted, and then travel
to their respective areas of the body e.g. cervical, brachial, lumbar, and sacral plexus
• Gray matter:- group of cell bodies that look grey because of nissil bodies filled with ribosomes.
• White matter:- myelinated axons appearing white because of the myelin sheath.
• Lamina/lemisci:- bundle of tracts having a different origin going to the same place or coming
from different places but going to the same origin
• Effector organ:- responds to stimuli
• Sensory organ:- carry sensory receptors
• Special sensory organs:- has specific receptors for specific stimuli e.g. tongue, eyes.

6. Cells/tissues making up the N.S
A. conducting cells:-
• Cells that have ability to generate an impulse and transmit it
from one area to another.
• only cell making up this is the neurone which is the
functional & structural unit of the nervous system.
• Its cytoplasm contains nissil granules/body that make it
appear grey(gray matter).
• Axon hillock which is the junction between the cell body and
axon lacks organelles
• Myelin sheath is a fatty tissue which insulates the axon
making the white matter

7. B. Supporting/neuroglial cells :- Provide structural and nutritional support to
neurones without them transmitting any impulse.

8. Classification of neurones
• Can be classified according to structure and
function.
A. functional classification:-
• Sensory/afferent neurones:- carry's
impulses for processing to the CNS.
• Motor /efferent neurons:- carry impulses
to the effector organ
• Interneurone /association neurone:-
commonly found in spinal cord connecting
motor and sensory neurons.

9. B. Structural classification:- according to the number of
processes (axons & dendrites) coming from the cell body.
• Anaxon:-lacks an axon but has dendrites. Found in special
sense organs like the retina of the eye.
• Unipolar:- lacks dendrites commonly found in sensory
organs.
• Pseudounipolar:- looks like bipolar but it is unipolar.
Commonly found in spinal cord & sensory nerves.
• Bipolar:- has one dendrite and one axon.
• Multipolar:- numerous dendrites and one axon. Commonly
making the motor nerves

10. Spinal cord
• Connects the CNS to PNS as a downward
extension of the medulla oblangata from the level
of upper border of C1 and extends down to the
level of lower border of L1.
• Length of the spinal cord is directly proportional
to that of the femur.
• It is around 45cm in female and 48cm in male.
• Produces spinal nerves and reflex arch.

11. • Lower part of the spinal cord is cone shaped called
conus medullaris held to the coccyx by a thin
fibrous strand/cord called filum terminale.
• It has two enlargements at the cervical and lumbar
regions.
Cervical enlargement:- larger (38mm) of the two found
at the level of C4 to T2 & is related to exit and entry of
nerves in to the upper limb(brachial plexus).
Lumbar enlargement:- (35mm) at the level of L2 to S3
related to entry and exit of the lumbar-sacral plexus.

12. Spinal segments
• Produce pairs of spinal nerves.
• There are 5 spinal segments
corresponding to 31 pairs of spinal nerves.
• There are 8 cervical nerves with 7
vertebral bones since the nerves in the
cervical segment emerge above the
vertebral bone while from T1 the nerves
emerge from below the vertebral bone.

13. Cross section of the spinal cord
White matter ( funiculus):-divided in to 3 parts:
• Anterior funiculus between ventral horns
and mainly contains motor/descending
tracts.
• Posterior funiculus between the dorsal horns
and contains mainly the sensory/ascending
tracts.
• Lateral funiculus found lateral to the gray
matter containing mainly mixed tracts

14. Formation of the spinal nerves
• Cell body's of motor nerves inside the
ventral horn while those of sensory nerves
on the dorsal horn join to form a spinal
nerve which is mixed(sensory & motor) .
• The spinal nerve will give off a dorsal/
posterior rami or an anterior/ventral rami.
• dorsal root gives off a dorsal root
ganglion(a group of cell bodies in the
P.N.S)

15. • endoneurial fluid: A low protein liquid that is the
peripheral nervous system equivalent to
cerebrospinal fluid in the central nervous system.
• perineurium: A protective sheath covering nerve
fascicles.
• glycocalyx: A glycoprotein-polysaccharide covering
that surrounds cell membranes.
• endoneurium: A layer of connective tissue that
surrounds axons.
• fascicles: A small bundle of nerve fibers enclosed
by the perineurium.
• epineurium: outermost layer of dense, irregular
connective tissue surrounding a peripheral nerve.

16. Brain
• brain is housed inside the bony covering called the
cranium. The cranium protects the brain from
injury. Together, the cranium and bones that
protect the face are called the skull.

18. meninges
• membranous coverings of the brain and
spinal cord.
• three layers of meninges, known as the dura
mater, arachnoid mater and pia mater.
• major functions:
• Provide a supportive framework for the cerebral
and cranial vasculature.
• Acting with cerebrospinal fluid to protect the CNS
from mechanical damage.

19. Dura Mater
• outermost layer of the meninges, lying directly
underneath the bones of the skull and vertebral
column.
• It is thick, tough and inextensible.
• Within the cranial cavity, the dura contains two
connective tissue sheets:
• Periosteal layer – lines the inner surface of the bones
of the cranium.
• Meningeal layer – deep to the periosteal layer inside
the cranial cavity. It is the only layer present in the
vertebral column.

20. • Between these two layers, the dural
venous sinuses are located. They are
responsible for the venous
vasculature of the cranium, draining
into the internal jugular veins.
• receives its own blood supply
primarily from the middle
meningeal artery and vein.
• innervated by the trigeminal nerve
(V1, V2 and V3).

21. arachnoid mater
• middle layer of the meninges, lying directly
underneath the dura mater.
• It consists of layers of connective tissue, avascular
and does not receive any innervation.
• Underneath the arachnoid is a space known as the
sub-arachnoid space. It contains cerebrospinal
fluid, which acts to cushion the brain.
• Small projections of arachnoid mater into the dura
known as arachnoid granulations allow CSF to re-
enter the circulation via the dural venous sinuses.

22. pia mater
• located underneath the sub-
arachnoid space.
• very thin, and tightly adhered to the
surface of the brain and spinal cord.
• It is the only covering to follow the
contours of the brain.
• highly vascularised, with blood
vessels perforating through the
membrane to supply the underlying
neural tissue.