1. Physiology of the sympathetic and parasympathetic nervous system
Dr. Moizuddin Khan
Associate Professor of Physiology
Dr.Beenish Mukhtar
Lecturer of Physiology

2. Objectives
Upon completion of this lecture, students should be able to understand:
The anatomy of somatic and autonomic nervous system
Sympathetic and parasympathetic nerves
Pre and post ganglionic neurons
Functions of sympathetic and parasympathetic nerves in head & neck, chest, abdomen and pelvis
Neurotransmitters release at pre and post ganglionic sympathetic / parasympathetic nerves endings
Various responses due to stimulation of the sympathetic / parasympathetic nervous system

4. Peripheral Nervous System
Somatic NS
Permits voluntary action
Control activity of skeletal muscles (writing your name).
Autonomic NS
Permits Involuntary functions
Control of blood vessels,
Glands & internal organs
e.g.:- bladder, stomach, heart.
The two systems are anatomically separated form each other, but functionally they work with each other in an integrated manner

5. Divisions of Autonomic Nervous System
Anatomically Functionally
Cranial Thoracolumber Sacral
outflow outflow outflow
Sympathetic N.S Parasympathetic N.S.
Thoraco –lumber Cranio – sacral
T1 to L3 III –VII- IX- X
S2 to S5

7. The autonomic reflex arc
The reflex arc
The autonomic reflex arc
The somatic reflex arc
Receptor
Mostly in viscera
Mostly in skin
Afferent
identical
Center
Lateral horn cells
Anterior horn cells
Efferent
2 neuron, relay in autonomic ganglia outside the CNS.
One neuron, supply the effector organ directly.
Effector organs
Smooth , cardiac muscles
skeletal

8. The ANS is most important in two situations:
1- In emergencies that cause stress and require us to "fight" or take "flight" (run away).
2- In no emergencies that allow us to "rest" and "digest".

9. Functional Division of Autonomic Nervous System
Parasympathetic NS
Sympathetic NS

10. Sympathetic nervous system
The sympathetic nervous system has a thoracolumbar outflow (T1-L3)
The sympathetic connecting the spinal cord with different visceral effectors consists of 2 neurons, pre- and post ganglionic neurons.
Sympathetic Trunk Ganglia

11. Functions of sympathetic nervous system during stress (mass discharge)
Dilates the pupil.
Increases all properties of the heart.
Dilates the bronchioles.
Constriction of skin blood vessels.
Shift of blood flow from skin & splanchnic areas to heart, CNS and skeletal muscles.
Increases glycogenolysis in the liver.
Elevates blood glucose & free fatty acid level.

12. 8- Contraction of splenic capsule.
9- Increases the secretion of adrenaline & noradrenaline from the adrenal medulla.
10- Increases mental activity.
11- Increases sweat secretion.
12- Reinforcing the alert, aroused state by stimulation of reticular formation by
catecholamine.

13. Parasympathetic Nervous System
Activities directed toward conserving and restoring energy
that allow us to "rest" and "digest"
The parasympathetic nervous system has a craniosacral outflow.
Prepares the body for recovery & repair. Its activity continues and even increase during sleep & rest.

14. Important Functions : 1- Pupillary constriction & accommodation.
2- Stimulation of GIT secretion & peristalsis
3- Secretion of watery saliva
4- Decrease heart properties
5- Constriction of bronchioles
6- Secretion of tears
7- Stimulation of emptying mechanism of the rectum and urinary bladder micturation & defecation.
8- Nerve of erection.

16. Comparison between sympathetic & parasympathetic systems
Origin
Thoracolumber outflow (T1-L3)
Craniosacral outflow
III, VII, IX, X
S2,3,4
Preganglionic fibers
--Short, from spinal cord to sympathetic chain.
-- Synapse & activates many postganglionic fibers.
Long , from brain or spinal cord to ganglia in effector organ.
--Synapse & activates few postganglionic fibers.
Solitary innervation
- Smooth muscles of cutaneous blood vessels.
- Pilomotor muscles
Sweat glands
- Lacrimal glands
Post- ganglionic fibers
Long, from sympathetic chain to the effector organ
Short, because ganglia are embedded in effector organ
Functionally
-- catabolic
-- prepare the body for vigorous muscle activity (fight & flight)
--Action is wide spread
-- Anabolic
-- Concerned with vegetative aspects of day to day living
-- action is localized and discrete

17. Sympathetic Tone
The sympathetic division controls blood pressure and keeps the blood vessels in a continual state of partial constriction
This sympathetic tone (vasomotor tone):
Constricts blood vessels and causes blood pressure to rise as needed
Prompts vessels to dilate if blood pressure is to be decreased
Alpha-blocker drugs interfere with vasomotor fibers and are used to treat hypertension

18. Parasympathetic Tone Parasympathetic tone:
Slows the heart
Dictates normal activity levels of the digestive and urinary systems
The sympathetic division can override these effects during times of stress
Drugs that block parasympathetic responses increase heart rate and block fecal and urinary retention

19. Effects of Sympathetic Activation
Sympathetic activation is long-lasting because
Norepinephrin……
Is inactivated more slowly than ACh
Is an indirectly acting neurotransmitter, using a second-messenger system
And epinephrine are released into the blood and remain there until destroyed by the liver

20. Balance Between The Two Is Responsible For Maintaining A Stable Internal Environment.

21. CNS control of the ANS
15.17

22. Neurotransmitters & Receptors of the ANS
All preganglionic fibers of ANS release and all parasympathetic postganglionic fiber release acetylcholine (ACh) (cholinergic).
MOST sympathetic postganglionic fibers release norepinephrine (adrenergic), except at sweat glands and some blood vessels in skeletal muscles where they release Ach.
 All cholinergic receptors on the postganglionic neurons of sympathetic and parasympathetic systems, and on the adrenal gland are nicotinic
 All cholinergic receptors on effector cells are muscarinic

23. 1. Cholinergic Receptors
They are named after the drugs that bind to them:
A. Muscarinic (G-ptotein coupled) Receptors (bind muscarine)
B. Nicotinic (ligand-gated) Receptors (bind nicotine)
Muscarine (Mushroom) Nicotine (Tobacco)
M1 M2 M3 M4 M5
Blocker: Atropine blocks M receptors and is used to inhibit salivary and bronchial secretion before surgery.

24. 2. Adrenergic Receptors
Adrenergic receptors bind to norepinephrine and epinephrine
α1-receptors: their activation usually produces excitation (most target tissues)
α2-receptors: their activation usually produce inhibition (digestive organs)
β1-receptors:. They cause an excitatory response (mainly in heart).
β2-receptors: their activation in general causes inhibition (blood vessels and airways).
β3-receptors: ???

25. Functions of Adrenergic Receptors
Alpha ( α-) Receptor
Beta (β-) Receptor
Vasoconstriction
Vasodilation ( β2
Iris dilation
Cardioacceleration (β1
Intestinal sphincter contraction
Increased myocardial strength (β1)
Bladder sphincter contraction
Glycogenolysis (β2)
Pilomotor contraction

26. Effects of Sympathetic and Parasympathetic Stimulation on Specific Organs

27. Effects of Sympathetic and Parasympathetic Stimulation on Specific Organs

28. Function of the Adrenal Medullae
Stimulation of the sympathetic nerves to the adrenal medullae causes large quantities of epinephrine and norepinephrine to be released into the circulating blood, and these two hormones in turn are carried in the blood to all tissues of the body.
On the average, about 80 per cent of the secretion is epinephrine and 20 per cent is norepinephrine

29. Epinephrine causes almost the same effects as those caused by norepinephrine, but the effects differ in the following respects:
First, epinephrine, because of its greater effect in stimulating the beta receptors, has a greater effect on cardiac stimulation than does norepinephrine.
Second, epinephrine causes only weak constriction of the blood vessels in the muscles, in comparison with much stronger constriction caused by norepinephrine
this difference is of special importance because norepinephrine greatly increases the total peripheral resistance and elevates arterial pressure
whereas epinephrine raises the arterial pressure to a lesser extent but increases the cardiac output more.

30. A third difference between the actions of epinephrine and norepinephrine relates to their effects on tissue metabolism.
Epinephrine has 5 to 10 times as great a metabolic effect as norepinephrine.
Epinephrine can increase the metabolic rate of the whole body often to as much as 100 per cent above normal,
in this way increasing the activity and excitability of the body.
It also increases the rates of other metabolic activities, such as glycogenolysis in the liver and muscle, and glucose release into the blood.

31. Thank You