1. THE NERVOUS SYSTEM 1

2. Structure of the Nervous System
The nervous system is formed of two parts :-
Central Nervous System (CNS)
Includes Brain and Spinal cord
Peripheral Nervous System (PNS)
Includes Cranial nerves ; Spinal nerves and ganglia .
PNS further subdivided into:
Sensory division (input) and Motor division (output) 2

3. Functions of Nervous System
Sensory Function
Sensory receptors gather information
Information is carried to the CNS
Motor Function
Decisions are acted upon
Impulses are carried to effectors
Integrative Function
Sensory information used to create:
Sensations
Memory
Thoughts
Decisions 3

4. Central nervous system
Nerve cells (neurons)
Conduct electrical impulses
Gilal cells (neuroglia)
Supports and protect neurons

5. In peripheral nervous system
Nerve fibers
Nerve cells, only in ganglia.
Supported by connective
tissue

6. Classification of neurons according to function
Sensory neurons
Motor neurons
Association neurons
(interneurons)

7. Neuroglia
Nerve cells

8. Neuron It is the structural and functional unit of the nervous tissue.
Consists of the nerve cell body and its processes.
Processes are formed of
dendrites
axon

11. Neuron structure Neuron structure Cell body Cell processes Dendrites
Axon

12. Neuron Cell Body Nucleus: large, spherical
vesicular with a prominent nucleolus.
Central in most neurons,

13. Neuron Cell Body
The cell body contains the usual organelles except the centrioles. why? (not divide)
Nissl bodies: rER + free ribosomes & polysomes (protein and membrane making).

14. Neuron Cell Body Golgi apparatus: around the nucleus,
And function to Synthesize neuro-transmitters.
Mitochondria: cellular respiration.
Lysosomes: contain hydrolytic enzymes.
Lipofuscin: pigment that accumulate with age.

15. Neuron Cell Body contains:
Neurofilaments: intermediate filaments support.
Neurotubule:
maintains shape
intracellular transport mechanism.

16. Differences betwen the axon & denderites:
Single
Long, thin of uniform diameter.
Branches at terminal end
may give collateral arise at right angle.
Axoplasm lacks Nissl granules and Golgi complex.
Carries impulses away from cell body; centrifugal
May be myelinated.
Multiple
Short, irregular, wide base and tapering ends
Gives extensive branches arise at acute angle.
Cytoplasm contains all structures as the cell body except: no Golgi.
Carries impulses towards cell body; centripetal
Non-myelinated.

17. Neuroglial cells
Oligodentrocytes Schwan cells Astrocytes Ependymal cells Microglia cells

18. Types of Neuroglial Cells in the PNS
1) Schwann Cells
Produce myelin found on peripheral myelinated axons .
Speed up neurotransmission
2) Satellite Cells
Support clusters of neuron cell bodies in ganglia . 19

19. Types of Neuroglial Cells in the CNS
1) Microglia
Phagocytic cell
3) Oligodendrocytes
Responsible for Myelinaion
In the CNS
4) Ependyma or ependymal
Ciliated
Line central canal of spinal cord
Line ventricles of brain
help regulate composition of CSF
2) Astrocytes
aid in metabolism of certain substances
form blood-brain barrier.
Supportive in function.

20. Oligodendrocytes

21. Myelination of an Axon
Formed in peripheral nervous system ( PNS ) by Schwann cells

22. CNS Axons
Oligodendrocytes form the myelin sheaths around the fibers in the central nervous system (CNS ) .

23. Astrocytes

24. Ependymal cells
Lining the ventricle found in Brain and . spinal cord , in some places are ciliated to move the cerebrospinal fluid.

25. Microglial cells
Short elongated cells with short irregular process (elongated nucleus ). The other have spherical nucleus .

26. Central Nervous tissue
CNS
Spinal cord
Brain
Cerebrum
Cerebellum

27. CNS White matter Gray matter
Myelinated axons , Myelin- producing oligodendrocytes
Not contain neuronal
cell bodies ,
Present in central region
Nuclei (aggregates of neuronal cell bodies forming islands of gray matter embedded in white matter )
Neuronal cell bodies , dendrites and the initial unmyelinated portion of the axons and glial cells
Found at the surface of the cerebrum and cerebellum forming cerebral and cerebellar cortex.
White matter
Gray matter

28. Cerebral Cortex Has 6 layers of cells with different forms and sizes.
Some neuron are afferent (sensory) , other are efferent (motor).

29. Cerebellar Cortex Has 3 layers ;
1) outer molecular layer ; less cell dense layer
2) central layer (Purkinje cells) ;which have spicuous cell body and long dendrites reach to molecular layer .
3) inner(granular) layer ; formed by very small neurons (smallest one in the body) , compactly disposed.

30. Spinal cord White matter is peripheral.
Gray matter is central (H shape).
In horizontal part of H open a central canal lined with Ependymal cells
The legs of H forming anterior horns , which contain motor neuron make up ventral root , the gray matter also form posterior horns , which receive sensory fibers make up dorsal root .

31. Meninges
Membranous connective tissue
Dura mater
Arachnoid
Pia mater

34. Dura mater External layer
Composed of dense connective tissue continuous with periosteum of the skull.
Epidural space contains thin walwd vein , loose CT and adipose tissue
Separted from arachnoid by subdural space .
Its internal surface lined with simple squam. Epith.

35. Arachnoid Has 2 components;
Layer in contact with dura mater and system of trabeculae connecting to pia mater , the cavities between the trabeculae form subarachnoid space.

36. Pia mater
Loose connective tissue

37. Choroid plexus and CSF

38. (BBB) Blood Brain Barrier
Highly selective permeability barrier that separates the circulating blood from the brain extracellular fluid in the central nervous system.
Formed by brain endothelial cells, which are connected by tight junctions with an extremely high electrical resistivity .
allows the passage of water, some gases, and lipid-soluble molecules by passive diffusion, as well as the selective transport of molecules such as glucose and amino acids that are crucial to neural function. On the other hand, the blood–brain barrier may prevent the entry of lipophilic, potential neurotoxins by way of an active transport mechanism mediated by P-glycoprotein. Astrocytes are necessary to create the blood–brain barrier. A small number of regions in the brain, including the circumventricular organs (CVOs), do not have a blood–brain barrier.

39. Peripheral nerve system

40. Unmyelinated nerve

41. Myelinated nerve

44. CT Sheath

45. Nerve ganglia
Is a collection of nerve cells and fibers surrounded by a connective tissue capsule outside the CNS.
There are two types of ganglia.
Autonomic
Sensory (Spinal )
parasympathetic
Sympathetic

46. Autonomic (Symp. & para. )
Nerve ganglia
Sensory (Spinal)
Autonomic (Symp. & para. )
Two types:
*sympathetic.
*parasympathetic.
Motor.
Thin capsule.
Nerve cells:
* multipolar
* Few
* Small and equal in diameter.
* Scattered throughout the ganglion
* Nucleus is eccentric.
* Capsule of satellites is incomplete.
Sensory.
Thick capsule.
Nerve cells:
*unipolar
* many
* Variable in size (20-120µ)
* Grouped
* Nucleus large and central
* Surrounded by complete capsule of satellite cells

47. Autonomic (Sympathetic )
Nerve ganglia
Sensory (Spinal)
Autonomic (Sympathetic )
Nerve fibers:
* thick & myelinated
* widely separated from each other.
Nerve Fibers:
* Thin & non myelinated
* Close to each other.

50. Autonomic nervous system
Sympatatic & parasympatatic

51. Main changes that take place in an injured nerve fiber.
A: Normal nerve fiber, with its perikaryon and effector cell (striated skeletal muscle). Note the position of the neuron nucleus and the quantity and distribution of Nissl bodies.
B: When the fiber is injured, the neuronal nucleus moves to the cell periphery, and Nissl bodies become greatly reduced in number. The nerve fiber distal to the injury degenerates along with its myelin sheath. Debris is phagocytosed by macrophages.
C: The muscle fiber shows a pronounced denervation atrophy. Schwann cells proliferate, forming a compact cord penetrated by the growing axon. The axon grows at the rate of 0.5—3 mm/day.
D: Here, the nerve fiber regeneration was successful. Note that the muscle fiber was also regenerated after receiving nerve stimuli.
E: When the axon does not penetrate the cord of Schwann cells , its
growth is not organized.