Introduction to Autonomic nervous system

1. Saddam Ansari
2nd Year
Tbilisi State Medical University
Autonomic Nervous System (ANS)

2. Parasympathetic division
Craniosacral
division
Cranial portion
innervates
 Blood vessels of
head and neck
 Thoracoabdominal
visceral organs

3. Continued…
Sacral portion
innervates
 Smooth muscles
forming the walls of
viscera
 Glands
 Large intestine
 Liver, spleen, kidney
s,bladder, genitalia

5. Characteristics of Sympathetic
and Parasympathetic Function
Neurotransmitters of ANS
 Cholinergic and Adrenergic Fibers

8. Synthesis of Acetylcholine
 Synthesized in terminal endings of cholinergic
fibers.
 Most of the synthesis occurs in axoplasm
outside the vesicles.

9. Destruction of Acetylcholine

10. Synthesis of Norepinephrine
 Synthesis begins in axoplasm of terminal nerve
endings of adrenergic nerve fibers
 But its completed in vesicles
 In adrenal medulla 80 % of norepinephrine is
transformed in epinephrine

11. Continued…

12. Continued…
After secretion of NE, it is removed from
the site by three ways:
1. Reuptake into adrenergic nerve endings by
active transport process (50 to 80 % of NE)
2. Diffusion away from the nerve endings into
the body fluids and then to the blood (remaining
NE)

13. Continued…
3. Destruction of small amount by tissue
enzyme:
Monoamine oxidase
Catechol-O-methyl transferase (occurs
mainly in liver)

14. Receptors on Effector Organs
 To stimulate effector organ, neurotransmitters
must bind with receptors on the effector cells
 Receptors are present outside the cell
membrane that penetrates cell membrane
 Binding causes conformational change in the
protein
 In turn, altered protein molecule excites or
inhibits the cell, most often by 2 means :

15. Continued…
1.Causing a change in the cell
membrane permeability to one or more
ions
2. Activating or inactivating an enzyme
attached to the other end of the receptor
protein

16. Types of Acetylcholine Receptors
Mainly 2 types
1.Muscarinic
 Origin- Muscarine means poison from
toadstool
 Activates only muscarinic receptors
 Found on all effector cells stimulated by
parasympathetic nervous system
 And also stimulated by cholinergic
neurons of sympathetic system

17. Continued…
2.Nicotinic
 Found at synapses between the pre and
postganglionic neurons of both sympathetic and
parasympathetic system
 Also present at nonautonomic nerve endings e.g.
neuromuscular junction in skeletal muscle
 Activated by nicotine , not muscarine
NOTE: Acetylcholine can activate both of the
receptors.

18. Adrenergic Receptors
Alpha Receptors (alpha1 and
alpha2)
Beta Receptors (beta1 and beta
2 and beta 3)

19. Function of Alpha Receptors
 Vasoconstriction
 Iris dilation
 Intestinal relaxation
 Intestinal sphincter contraction
 Pilomotor contraction
 Bladder sphincter contraction

20. Function of Beta Receptors
 Vasodilation -beta 2
 Cardioacceleration – beta 1
 Increased myocardial strength – beta 1
 Intestinal relaxation – beta 2
 Uterus relaxation – beta 2

21. Continued…
 Bronchodilation – beta 2
 Calorigenesis – beta 2
 Glycogenolysis – beta 2
 Lipolysis – beta 1
 Bladder wall relaxation – beta 2