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

3. Preganglionic sympathetic as well as parasympathetic are known as cholinergic as they secret acetylcholine.
Post ganglionic sympathetic fibers are known as adrenergic as they secret norepinephrine (except fibers to sweat gland & blood vessels of skeletal muscle, they are cholinergic)
Post ganglionic parasympathetic fibers are known as cholinergic as they secret acetylcholine.

4. Autonomic Neurotransmitter Receptors
Tissues innervated by autonomic nervous system have one or more of several different receptor types for postganglionic chemical messengers
Cholinergic receptors – bind to Ach -2 types
Nicotinic receptors – found on postganglionic cell bodies of all autonomic ganglia
Muscarinic receptors – found on effector cell membranes
Andrenergic receptors – bind to norepinephrine and epinephrine
Alpha (α) receptors
Beta (β) receptors

5. NICOTINIC RECEPTORS (PREGANGLIONIC)
ACTIVATED BY ACETYL CHOLINE ENDOGENOUSLY AND NICOTINE EXOGENOUSLY
BLOCKED BY CURARE AND HEXAMETHONIUM

6. MUSCARINIC RECEPTORS (POSTGANGLIONIC)
ACTIVATED BY ACETYL CHOLINE ENDOGENOUSLY AND MUSCARINE EXOGENOUSLY
BLOCKED BY ATROPINE

7. Properties of cholinergic receptors
Nicotinic receptors: binding of Ach to these receptors initiates opening of non specific cation channels .
Muscarinic receptors : binding of Ach initiates G protein linked receptors pathways , depending on effector organ.

8. Properties of adrenergic receptors
α1 & α2 receptors have greater sensitivity to norepinephrine
β2 receptors binds exclusively with epinephrine
β1 receptors have equal affinity for epinephrine and norepinephrine
All adrenergic receptors are linked to G protein
Activation of β1 & β2 activates cAMP
Activation of α1 activates IP3 /Ca2+
Activation of α2 inhibits cAMP in target cells

9. In general α1
excitatory β1 α2
inhibitory β2

11. Adrenaline/epinephrine Noradrenaline/norepinephrine
Site of release
-Adrenal medulla ( 80% of its secretion ).
-Adrenal medulla ( 20% of its secretion ).
-Sympathetic postganglionic nerve endings.
Action on adrenergic receptors
Acts on both α and β receptors.
Acts mainly on α receptors.
Effect on the heart
More strong
Less strong
Effect on the blood vessels
Vasoconstriction ,
but it causes vasodilation in the BVs of the skeletal muscle and liver
Vasoconstrictor only.
I.e. it has more potent pressor action.
Relaxing effect on the GIT

13. Effect of ANS ON VARIOUS ORGANS

14. EFFECTS OF ANS

15. Functions of the sympathetic NS
sympathetic NS is characterized by:
It discharges during emergency and stress ( fight and flight reaction).
It acts as one unit (generalized action).
It has catabolic action.
Delays evacuation of visceral content.

16. Functions of the parasympathetic NS
Parasympathetic NS is characterized by:
It discharges during rest and sleep.
Its action is localized.
It has anabolic action (conserve body stores ).
It increases gastrointestinal secretion & motility
i.e. secretomotor.

17. Structures supplied only by sympathetic nervous system:
Skin
Sweat glands (sympathetic cholinergic)
Piloerector muscle.
Blood vessels all over the body except the penis & clitoris .
Dilator papillae muscle.
Blood vessels of the skeletal muscles
Adrenal medulla.
Capsule of the spleen .

18. Structures supplied only by Parasympathetic nervous system:
Constrictor papillae muscle.

19. Autonomic agonist and antagonist
Agonist : Binds to neurotransmitter’s receptor and causes the same response as neurotransmitter would.
E.g. Salbutamol β2 agonist ( bronchodilator)
Antagonist : Binds with the receptor preventing the neurotransmitter from binding and causing a response.
E.g. atropine blocks the effect of Ach on muscarinic receptors ( blocks the parasympathetic effect). Use to suppress the salivary and bronchial secretion before surgery
Metaprolol selectively blocks the β1 receptors use for treating blood pressure(β1 in heart )

20. Regions of CNS Involved in Control of Autonomic Activities
Hypothalamus plays important role in integrating autonomic, somatic, and endocrine responses that automatically accompany various emotional and behavioral states
Medulla within brain stem is region directly responsible for autonomic output( cardiovascular & respiratory centers)
Some autonomic reflexes, such as urination, defecation, and erection, are integrated at spinal cord level

21. Regulation of autonomic nervous system

22. 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