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49 Introduction Any activity in our life is under control of one of the main control systems: 1- Endocrine system: This controls the slow action by hormones.II. The parasympathetic nervous system:
o This arises from the 2nd, 3rd and 4th sacral segments of the spinal cord as well as from the nuclei of some cranial nerves III, VII, IX and X cranial nerves (Cranio-sacral outflow).The regulation of blood pressure, gastrointestinal responses to food, contraction of the urinary bladder, focusing of the eyes, and thermoregulation are just a few of the many homeostatic functions regulated by the ANS. 31 segments (8 cervical, 12 thoracic, 5 lumbar, 5 sacral and 1 coccegeal).o Divided into: 3 cervical, 12 thoracic, 4 lumber, 4 = sacral.- Inferior mesentric ganglion.????

49
Introduction
Any activity in our life is under control of one of the main control systems:
1- Endocrine system: This controls the slow action by hormones.
2- Nervous system: this controls the rapid action by neurotransmitters.
Division of nervous system:

A. Central nervous system:
a) Brain:
➢ Brain stem (mid brain, pons and medulla oblongata).
➢ Cerebellum.
➢ Cerebral cortex.

b) Spinal cord:

➢ 31 segments (8 cervical, 12 thoracic, 5 lumbar, 5 sacral and 1
coccegeal).
B. Peripheral nervous system:

a) Cranial nerves:
 Autonomic (involuntary).
 Somatic (voluntary).
b) Spinal nerves:
 Autonomic.
 Somatic.
Compare between somatic and autonomic nervous
system??????
Autonomic nervous system (ANS):
• Also known as the visceral or involuntary nervous system, the ANS
functions without conscious, voluntary control.

• It innervates cardiac muscle, smooth muscle, and various
endocrine and exocrine glands, this nervous system influences the
activity of most tissues and organ systems in the body.

• Therefore, the ANS makes a significant contribution to homeostasis.
The regulation of blood pressure, gastrointestinal responses to food,
contraction of the urinary bladder, focusing of the eyes, and
thermoregulation are just a few of the many homeostatic functions
regulated by the ANS. 50
Divisions of the A.N.S:
The A.N.S. is divided into the following 2 systems:
I. The sympathetic nervous system:

• This arises from the lateral horn cells (LHCs) of all thoracic and
upper 3 lumbar segments of the spinal cord (thoraco-lumbar
outflow).
II. The parasympathetic nervous system:

• This arises from the 2nd, 3rd and 4th sacral segments of the
spinal cord as well as from the nuclei of some cranial nerves
III, VII, IX and X cranial nerves (Cranio-sacral outflow).
Autonomic Ganglia
Definition: It is the site of physiological contact between pre and post
ganglionic fibers.
Types:

a) Lateral (sympathetic).
b) Collateral (mixed) or pure sympathetic.
c) Terminal (parasympathetic).
Lateral (paravertebral):
• These are 23 ganglia that form the sympathetic chain.

• Divided into: 3 cervical, 12 thoracic, 4 lumber, 4 = sacral.
Collateral:

• Around the large blood vessels as:
– Caeliac ganglion.
– Superior mesentric ganglion.
– Inferior mesentric ganglion.
Terminal: (in the wall of organ, no post-ganglionic or very short post-
ganglionic fiber may be present).
Functions:

1. Distributing center.


2. Relay station between pre and postganglionic fiber.