NERVOUS SYSTEM
Nervous system is divided into:
I. Central nervous system:
A- Brain.
B- Spinal cord.
II. Peripheral nervous
system:
A- Nerves:
1. Spinal nerves (31 pairs).
2. Cranial nerves (12 pairs).
B- Autonomic nervous
system:
1. Sympathetic.
2. Parasympathetic.
It is present inside the skull.
Parts:
A- Fore brain: consists of
two cerebral hemispheres and diencephalons.
B- Mid brain.
C- Hind brain: consists of pons, medulla oblongata and cerebellum.
Diencephalons:
Consists of five parts, the most important of them is the thalamus &
hypothalamus.
Brain stem: consists of 3 parts: 1- Midbrain. 2- Pons. 3-Medulla oblongata.
Cerebral hemisphere: has 4 lobes
1- Frontal lobe: It lies infront of the central sulcus.
It contains motor area (area 4) which controls the movement of the opposite
half of the body.
Brocha's area (motor speech area) (area 44) which control the speech and it
present in the left hemisphere of the right handed person.
2- The parietal lobe: It lies behind the central sulcus.
It contains the sensory area (area 3, 1, 2) which receives the sensation from the
opposite half of the body.
3- Temporal lobe: It lies below the lateral sulcus and contains the auditory area
(area 41, 42).
4- Occipital lobe: It lies posterior to the temporal and parietal lobes. It contains
the visual area (area 17, 18, 19).
Spinal Cord
Length: 45 cm.
Site: present inside the vertebral column.
Segments: 31 (8 cervical, 12 thoracic, 5 lumbar, 5 sacral and one coccygeal). Each
segment gives origin to a pair of spinal nervous.
Meninges
They are the coverings of central nervous system, and they are arranged from inside
outside:
1- Pia mater. 2- Arachnoid mater. 3- Dura mater.
The space which lies between the pia and arachnoid mater is called subarachnoid
space. It contains C.S.F. and the blood vessels of the brain.
Cerebral Spinal Fluid (CSF)
It is a clear fluid circulating inside the cavities of the CNS and in subarachnoid space
outside it. It supports and protects the brain and spinal cord.
Nerves
They arise from:
A- Spinal cord: (spinal nerves):
They are 31 pairs (8 cervical, 12 thoracic, 5 lumbar, 5 sacral and one coccygeal).
B- Brain (cranial nerves), they are 12 pairs.
Superficial attachment of the cranial nerves:
1 and 2 are attached to cerebral hemisphere.
3 and 4 are attached to midbrain.
5, 6, 7 and 8 are attached to pons.
9, 10, 11 and 12 are attached to medulla oblongata.
Cranial nerves and their functions:
1- Olfactory nerve: Smell.
2- Optic nerve: vision.
3- Oculomotor: Supplies all muscles of eye except 2 muscles.
4- Trochlear nerve: Supplies superior oblique muscle of the eye.
5- Trigeminal nerve:
a- Sensory to face and scalp and anterior 2/3 of tongue.
b- Motor for the 4 muscles of mastication and another 4 muscles.
6- Abducent nerves: Supplies the lateral rectus muscle of eye.
7- Facial nerve:
a- Motor to muscles of face (facial expression).
b- Sensory carries taste from the anterior 2/3 of the tongue.
8- Auditory nerve: Hearing and equilibrium.
9- Glossopharyngeal nerve:
a- Motor to one muscle of pharynx.
b- Sensory carries sensation from pharynx and general sensation and taste from
posterior 1/3 of tongue.
10- Vagus:
a- Motor: To muscles of larynx, pharynx and palate.
b- Parasympathetic: To heart, respiratory system and gastrointestinal tract.
11- Accessory nerve:
Supplies two muscles: trapezius and sternomastoid muscle.
12- Hypoglossal nerve:
Supplies all muscles of tongue except one muscle.
Autonomic Nervous System
It is concerned with involuntary activities. It supplies the heart, the smooth muscles
of the G.I.T, respiratory and urinary system and it stimulates the secretion of the
glands.
It has 2 parts:
A- Sympathetic nervous system.
B- Parasympathetic nervous system.