ans

1. CHAPTER 9
Autonomic Nervous System (ANS)
• Divisions of ANS
– Sympathetic
– Parasympatheitc
• Functions of ANS
• Control of ANS
Dr. Hameed Al-Sarraf
Dept. Physiology
hameed_alsarraf@hotmail.com

2. Autonomic Nervous System
• Nervous system that controls many involuntary functions
of the body.
• ANS effects (controls) organs which are under involuntary
control.
• Effectors of ANS usually are:
– Cardiac Muscle
– Smooth Muscle
– Glands

4. Divisions of ANS
• 1- Sympathetic (Thoracolumbar) Division
• 2- Parasympathetic (Craniosacral) Division.

5. Sympathetic

6. Sympathetic Chain

7. Sympathetic Chain

8. Parasympathetic

9. Parasympathetic

11. Innervation of Body Organs
- In the body there are organs which are innervated by both
sympathetic and parasympathetic systems:
- Heart
- Digestive tract
- Pupil of the eye
- Salivary glands, etc
-There are organs with only sympathetic innervation:
- Adrenal medulla
- Sweat glands
- Most blood vessels

12. Functions of ANS
1- Sympathetic system:
-Mass discharge of sympatheic system prepares the body for
activity (Fight/Flight).
- Excitation of sympathetic centers will cause:
- Increase in heart rate.
- increase in blood pressure,
- blood glucose is elevated
- increase in the rate of metabolism
- mental activity is also raised,
- blood is diverted to skeletal muscle.
2- Parasympathetic system: usually has opposite effects to those of sympathetic
system. Excitation of parasympathetic causes:
- decrease in heart rate,
- increase blood flow to the digestive system,
- increase activity of the digestive system.

13. Sympathetic and Prasympathetic Tone
- Normally both symathetic and parasympathetic systems continuously transmit
action potentials (signals) at low rate throughout their nerve fibers.
- By doing this the ANS can have both positive and negative effects on its
effector organs:
e.g control of blood vessel diameter by sympathetics,
Fast rate of action potentials Vasoconstriction
vessel diameter
Sympathetic slow rate of action potentials
at rest
tone
Stop sending action potentials Vasodialatation

14. Examples of Sympathetic System in Action
Mass discharge (activation) of sympathetic system prepares the body for activity
Example 1:
Blood flow to muscle in exercise:
Sympathetic nervous system causes blood shift to muscle
during exercise by vasoconstriction of blood vessels of all
other organs except heart and brain.
Example 2:
Liver:
Stimulation of glycogenolysis to produce glucose which will
be release into blood to provide muscle with fuel .

15. Examples of Parasympathetic
System in Action
Activation of parasympathetics usually has opposite effects to the sympathetics.
Example 1:
on gastrointestinal tract:
Parasympathetic system causes increased blood flow, motility and secretion
of gastrointestinal tract (e.g. stomach, small intestine)
Example 2:
Heart and lungs:
Reduced heart rate and constriction of air tubes (bronchioles) in the lung.

16. Neurotransmitters of the ANS
1- Acetylcholine (ACh)- the transmission is said to be cholinergic.
- ACh is the transmitter released by:
- all preganglionic fibers
- most parasympathetic postganglionic fibers
- some sympathetic postganglionic fibers
2- Norepinephrine (noradrenaline)- the transmission is said to be adernergic.
- Norepinephrine is the transmitter released by:
- most postganglionic sympathetic fibers,
3- Non-adernergic non-cholinergic (NANC)-
- the transmitter is neither ACh nor NE
- proposed candidates are: ATP, VIP, and NO.

17. *Some sympathetics that innervate blood vessels and all sympathetics that
supply sweat glands release acetylcholine (ACh) as their neurotransmitter.

18. Sympathetic and
Parasympathetic innervation
of Effectors.

19. Receptors
-NE causes excitation to some tissues while it inhibits others.
This is due to the presence of different receptors on the target cells.
- There are two types of adernergic receptors:
- α-adernergic receptors
- β-adernergic receptors
- ACh also has two types of receptors:
- Nicotinic
- Muscarinic

20. Adernergic Receptors
1- Binding of epinephrine or norepinephrine (NE) to α-receptor causes increase in
cytoplasmic Ca++ levels:
NE
Membrane
α-receptor Phospholipase C
Increase cytoplasmic Ca ++
Endoplasmic Reticulum
Inositol triphosphate (IP3)
receptor
Closed Ca++ channels Opening Ca++ channels

21. Adernergic Receptors
2- Binding of epinephrine or norepinephrine to β-receptor stimulates the production
of cyclic adonesine monophosphate (cAMP).
NE
Membrane
β-receptor Adenylate cyclase (inactive)
Adenylate cyclase (active)
Cytoplasm
ATP cAMP
Catalyse many
Protein kinase Protein kinase Reactions in the
(inactive) (active) cell

23. Control of the ANS by Higher Brain Centers
Higher Brain
Hypothalamus
Centers
Contain centers which control:
cardiovascular, pulmonary,
Medulla Oblongata urinary, reproductive and
digestive system.
Sensory
Inputs
Effector
Organs

24. Control of ANS by Centers in Brain
Brain stem – mainly controls vascular system and respiration.
Hypothalamus-
-Cardiovascular system; stimulation of:
- posterior hypothalamus causes increase in blood pressure and heart rate ,
- anterior hypothalamus causes decrease in blood pressure and heart rate.
-Body temperature:
- changes in blood temperature in anterior hypothalamus causes several
mechanisms to operate for temperature regulation.
- Body water- secretion of ADH and signals to initiate thirst
- Feeding – hunger and satiety centers
- Excitement and rage- perifornical nucleus in hypothalamus
- Endocrine function – neurosecretory substances secretion to anterior pituatory.

25. Reflex Effects of Sensory Inputs
to Brain Centers
Organ Type of Receptor Reflex Effect
Lung Stretch receptor inhalation is inhibited
and heart rate increase
Aorta Chemoreceptor increase breathing and heart
rate
Baroreceptor decrease in heart rate
Heart Stretch receptor increase volume of urine
excreted
and decrease in heart rate
G.I. Tract Stretch receptor feeling of satiety