1. Autonomic Nervous System-I
بسم الله الرحمن الرحيم
Autonomic Nervous System-I
Dr.Mohammed Sharique Ahmed Quadri
Assistant prof. Physiology
Al Maarefa College

2. PNS: Efferent Division
Communication link by which CNS controls activities of muscles and glands
Two divisions of PNS
Autonomic nervous system (ANS)
Involuntary branch of PNS
Innervates cardiac muscle, smooth muscle, most exocrine glands, some endocrine glands, and adipose tissue
Somatic nervous system
Subject to voluntary control
Innervates skeletal muscle

3. Autonomic Nervous System
The portion of the nervous system which controls most visceral function of the body is called as autonomic nervous system.
Arterial pressure
heart rate
GI motility
GI secretion
Urinary bladder emptying
Sweating
Body temperature

4. The efferent autonomic signals are transmitted to the various organs of the body through 2 major subdivision.
Sympathetic nervous system
Parasympathetic nervous system

5. Physiologic anatomy of the ANS
Sympathetic nerve fibers originate in the spinal cord along with the spinal nerve between T1-L2/L3 ( thoraco lumbar ).
Parasympathetic nerve fibers originate from brain stem (midbrain, pons, and medulla) or the sacral spinal cord ( craniosacral).
The preganglionic fibers originates from nuclei of cranial nerves (CN) III, IV, IX and X or from sacral spinal segments S2-S4.

6. ANS Preganglionic fiber (synapses with cell body of second neuron)
Autonomic nerve pathway
Extends from CNS to an innervated organ
Two-neuron chain
Preganglionic fiber (synapses with cell body of second neuron)
Postganglionic fiber (innervates effector organ)

8. Physiologic anatomy of the sympathetic nervous system
Sympathetic nerve fibers originate in the spinal cord along with the spinal nerve between T1 – L2. ( thoraco lumbar )
Length of the pre & postganglionic fibers
Preganglionic fibers – are shorter
Post ganglionic fibers – are longer

9. sympathetic nervous system
Pre ganglionic sympathetic fibers always cholinergic, i.e. secretes Ach. This activates nicotinic receptors in the post ganglionic fibers. Post ganglionic fibers are adrenergic. They act on adrenoreceptors (α1, α2, β1, or β2). Only exception is post ganglionic fibers supplying thermoregulatory sweat glands that is cholinergic that acts on muscarinic receptors.

11. Functions of sympathetic nervous system
Sympathetic system dominates in emergency or stressful (“fight-or-flight”) situations
Promotes responses that prepare body for strenuous physical activity

12. Parasympathetic nervous system
Parasympathetic system originates from brain stem (midbrain, pons, and medulla) or the sacral spinal cord ( craniosacral).
The preganglionic fibers originates from nuclei of cranial nerves (CN) III, IV, IX and X or from sacral spinal segments S2-S4.

13. Parasympathetic nervous system
Length of the pre & postganglionic fibers
Preganglionic fibers –are longer
Post ganglionic fibers – are shorter
Pre ganglionic para sympathetic fibers always cholinergic, ie secretes Ach. This activates nicotinic receptors in the post ganglionic fibers.
Post ganglionic fibers are cholinergic.

14. Parasympathetic nervous system
e.g. parasympathetic innervation of eye muscles originates in the Edinger-Westphal nucleus in the midbarin. Like wise, X nerve (vagus) originates in the nuclei of the medulla.

16. ANS
Parasympathetic system dominates in quiet, relaxed (“rest-and-digest”) situations
Promotes body-maintenance activities such as digestion
It allows the body to recover from stress

17. ANS Sympathetic Nervous System Parasympathetic Nervous System
Fibers originate in thoracic and lumbar regions of spinal cord
Fibers originate from cranial and sacral areas of CNS
Most preganglionic fibers are short
Preganglionic fibers are longer
Long postganglionic fibers
Very short postganglionic fibers
Preganglionic fibers release acetylcholine (Ach)
Most postganglionic fibers release noradrenaline (norepinephrine), accept in sweat gland (Ach)
Postganglionic fibers release acetylcholine
Autonomic ganglio is prevertebral & paravertebral
Autonomic ganglia is near effector organ

18. ANS
Most visceral organs innervated by both sympathetic and parasympathetic fibers
In general produce opposite effects in a particular organ
Dual innervation of organs by both branches of ANS allows precise control over organ’s activity

20. EFFECTS OF ANS

21. ANS
Exceptions to general rule of dual reciprocal innervation by the two branches of autonomic nervous system
Most arterioles and veins receive only sympathetic nerve fibers (arteries and capillaries are not innervated)
Most sweat glands are innervated only by sympathetic nerves
Salivary glands are innervated by both ANS divisions but activity is not antagonistic – both stimulate salivary secretion

22. Distinguishing Characteristics of Sympathetic and Parasympathetic Nervous Systems

23. References Human physiology by Lauralee Sherwood, seventh edition
Text book physiology by Guyton &Hall,11th edition
Text book of physiology by Linda .s contanzo,third edition