The central nervous system

Prepared by

Nouf Alyami

Contents

• CNS

• PNS

• the nerves tissue

• the brain parts

• The brain meninges

• The brain barriers

• cerebrum

• The Basal ganglia

• Cerebral cortex

• The spinal cord

• diseases

peripheral nervous system consists of 12 pairs of cranial nerves, which emerge from your brain and mainly serve your head and neck. It also contains 31 pairs of spinal nerves, which branch off from your spinal cord and supply the rest of your body.

Subdivision of the nervous system

CNS PNS

Brain Spinal cord Outside these organs

CNS

White matter Gray matter

The brain

Cerebral cortex

White matter

Cerebral cortex

The following six layers are present:

1. the molecular layer: it is the most superficial layer. It is formed mainly of the nerve fibres (axons & dendrites) of the nuclear and the pyramidal cell layers.

2. The External nuclear: it is formed of stellate-shape cells.

3. The small pyramidal cell layer:it is formed of small pyramidal-shape nerve cells.

4. The internal nuclear: it is formed of small stellate-shape nerve cells.

5. The large Pyramidal cell layer:it is formed of large pyramidal-shape nerve cells.

6. The Polymorphic cell layer: it is formed of different nerve cells and fibers.

pyramidal

pyramidal

The spinal cored

White matter

Gray matter

Nerves tissue

Supporting cells of nervous

tissues:1-Astrocytes.

2-Microglia.

3-Ependymal.

4-Oligodendrocytes. 5-Schwann cells.

Neurons.

classification of neurons on the basis of structure:

1-Multipolar.

2-Bipolar.

3-unipolar.

1-Astrocytes:

3-Ependymal:

4-Oligodendrocytes:

5-Schwann cells:

The neroglia

These are the supporting cells and fibres which are present between the neurones of the brain and spinal cored.

Type and function:

1. protoplasmic macroglia nutritive

2. Fibrous macroglia White mater Support isolate

3. Microglia Grey & white Phagocytic cells

4. oligodendroglia Grey & white Myelin sheaths

Grey mater

classification of neurons on the basis of structure:

Video time

The Brian

The brain meninges

The central nervous system is covered by 3 protective membranes called meninges

These meninges are:

1.Pia mater

2.Arachnoid mater

3.Dura mater

The pia mater:It is the vascular membrane of the meninges. It fits directly on the outer surface of the brain and spinal cord.

The pia mater is formed of :• autre layer which is formed of collagenous bundles.

• inner layer which is formed of reticular and elastic fibres.

The pia is covered with simple squamous epithelium

The arachnoid mater: it is formed of C.T fibres devoid of blood vessels.

The subarechnoid space is area between arachniod mater and the pia mater. It contains:

• the cerebro –spinal fluid (C.S.F).

• the blood vessels of the brain.

N.B. the subarachnoid space is narrow but in certain areas, it may

become wide to form the subarachnoid cisternae.

The (C.S.F):It is about 135 c.c circulating in the brain ventricles, in the central canals of the brain and the spinal cord as well as in the subarachnoid space.it is formed by the choroid plexus of the brain ventricles.

Any obstruction to the normal passage of the C.S.F causes the fluid to accumulate in the brain ventricles

leading to increase in the intracranial pressure (Hydrocephalus)

The choroid plexuses:They are formed by single layer of cuboidal cells with a plexus of blood capillaries. They are present in the wall of the brain ventricles.

Video time

The dura mater:It is the moust external covering of the brain. It is formed of dense C,T rich in collagenous fibres. it contains venous sinuses which drain the blood and the C.S.F from the brain.

The brain barriers

The brain cells and the cerebro spinal fluid in the brain cavities and canals are protected from micro organisms and other harmful substances which may be present in the circulating blood by 3 barriers. And they are:

1. the blood brain barrier.

2. the blood C.S.F barrier.

3. the brain C.S.F barrier.

1. the blood brain barrier.

2. the blood C.S.F barrier.

3. the brain C.S.F barrier.

The brain consists of the following parts

The brain stem The cerebrum The cerebellum

The brain stem connects the brain with the spinal cord and is composed of 3 structures: the midbrain, pons, and medulla oblongata. The brain stem provides us with automatic functions that are necessary for survival.

The cerebellum is located near the base of the head. It creates automatic programs so we can make complex movements without thinking.

cerebrum

The is two hemispheres connected by corpus callosum, each hemispheres contains of grey and white matter which contain the basal ganglia.

Cerebral map

Homunculus

The Basal ganglia

The Basal ganglia are formed of 4 nuclei which are present in the white matter. The Nuclei of the Basal ganglia:

1. the Caudate nucleus

2. the Lentiform nucleus

3. the Claustreum nucleus

4. the Amygdaliod nucleus

The Basal ganglia

The spinal cored

8

12

5

5

1

Each part of the C.N.S is composed of:

• Grey and white matter.

• Nucleus in C.N.S.: group of nerve cells laying very close to each other and having the same function.

• Tract: group of nerve fibres (axons) which arise from the same origin and terminate at the same termination and they have the same function.

• Bundle: group of nerve fibres some them are ascending and the other descending. the fibres arise from the different origin and terminate at the same termination .the fibres of the bound carry different inpules.

• Relay (synapse)

• commissure(is a band of with matter connecting a part of the C.N.S on one side with the same part on the other side.

1

2

3

4

5

67

89

10

diseases

Epilepsy : has deen recognized for 2400 years,drived from the Greek

means attack . It is syndrome of disturbed electrical activity in the brain.

Alzheimer's: dementia (among older people) Which involves the parts of the brain that control thought,

memory, and language.

Parkinson : The most common diseases. Occurs between 50 and 65 age. It may be inherited , man are likely to have it than women.