1. Autonomic Nervous System
Prof. K. Sivapalan

2. Autonomic Nervous System.
Visceral function is regulated by autonomic reflexes and endocrines.
Many reflexes are coordinated at spinal level- bladder, rectum, and sexual reflexes- input from higher centers also.
Blood pressure, respiration, swallowing, coughing, sneezing, gagging and vomiting are coordinated in brain stem- medulla oblongata.
Light reflex is coordinated in midbrain.
Temperature regulation and many complex mechanisms are coordinated in hypothalamus.
9/28/2019
Thalamus & hypothalamus

3. Autonomic Nervous System
Comparison
Somatic NS
Autonomic NS
Voluntary
External sensory and motor
Motor- 1 neuron
Sensory in dorsal horn, motor in ventral horn
Involuntary
Internal sensory and motor
Motor- 2 neurons
Sensory in dorsal part of lateral horn, Motor in ventral part of lateral horn.
May 2013
Autonomic Nervous System

4. Autonomic Nervous System
May 2013
Autonomic Nervous System

5. Autonomic Nervous System
Divisions of ANS
Sympathetic
Parasympathetic
Thoraco-lumbar outflow - T1 to L2
Short preganglionic
Preganglionic ending- acetyl choline
Post ganglionic- noradrenalin, others in some areas
Fight or flight - catabolic
Cranio-sacral outflow – 3,7,9,10 and S-2,3,4
Long preganglionic
Preganglionic ending- acetyl choline
Post ganglionic- acetyl choline, others in some areas
Anabolic
May 2013
Autonomic Nervous System

6. Autonomic Nervous System
May 2013
Autonomic Nervous System

7. Autonomic Nervous System
General Facts
Most organs- dual innervation with opposing effects
Exceptions- blood vessels, reproductive function
Preganglionic- myelinated [white rami]
Postganglionic- nonmyelinated [gray rami]
May 2013
Autonomic Nervous System

8. Autonomic Nervous System
May 2013
Autonomic Nervous System

9. Autonomic Nervous System
May 2013
Autonomic Nervous System

10. Autonomic Nervous System
May 2013
Autonomic Nervous System

11. Autonomic Nervous System
May 2013
Autonomic Nervous System

12. Autonomic Nervous System
Receptors
Any cell responds to chemical substances only if they bind with a receptor.
The chemical may be a neuro-transmitter or a hormone
The receptor may be located on the cell membrane, in the cytoplasm or in the nucleus
Substances that bind to receptors in side the cell will have to go through the cell membrane
Most of the receptors are located on the outer surface of the cell membrane and also to effector molecules in the membrane or in the interior of the cell.
They sometimes act directly and some times through second messangers
May 2013
Autonomic Nervous System

13. Receptors for Neurotransmitters
Chemicals released from the nerve endings are called neuritransmitters
They generally increase or decrease permeability of specific ions by acting on the ligand gated channels
Alteration of sodium or potassium permiability will depolarize or hyperpolarize the membrane.
Alteration of calcium permiability may, in addition, bring about change in the action directly
Another mechanism is being linked to an enzyme such as adenylyl cyclase leading to formation of cAMP.
The action of autonomic nerves on the effector organs depends on the transmitter and more importantly on the type of receptor and its associated mechanisms
May 2013
Autonomic Nervous System

14. Acetyl Choline Receptors
Structure-
Nicotinic and muscarinic receptors
Muscarine is a poison from toadstool [a fungus]
Muscarinic receptors are found in effectors innervated by post ganglionic cholinergic endings
Nicotinic receptors are found in autonomic ganglia and in motor end plates
May 2013
Autonomic Nervous System

15. Autonomic Nervous System
Adrenergic Receptors
Noradrenaline [norepinephrine] and adrenaline [epinephrine] are known as catecholamines.
The receptors are categorised into alpha [α] and beta [β]. Each one is further subdivided into 1 and 2. The classification is based on the specific substances that stimulate and inhibit the functions.
Noradrenaline excites mainly α receptors and to a lessor extent on β receptors.
Adrenaline acts on both receptors equally.
May 2013
Autonomic Nervous System