Autonomic Physiology

Question 1

Describe the anatomy of the sympathetic branches of the ANS

Answer 1

“fight or flight”

sympathetic ganglia lie close to spinal cord in the sympathetic trunk (paravertebral ganglia), or in collateral (prevertebral)

sympathetic postganglionic fibres release noradrenalin which acts on a or B adregenic receptors

preganglionic fibres are short and postganglionic are long

Question 2

Describe the anatomy of the parasympathetic branches of the ANS

Answer 2

parasympathetic ganglia lie close to, or within the target

parasympathetic postganglionic fibres release acetylcholine- which acts on muscarinic cholinergic receptors

preganglionic fibres are long and postganglionic fibres are short

Question 3

Describe the neurotransmitters, receptors and functional aspects of autonomic innervation

Answer 3

pre-ganglionic fibres - small myelinated

postganglionic fibre - unmyelinated

less specialised junction than CNS

metabotropic receptors

may excite or inhibit target

Question 4

Describe simple autonomic reflexes

Answer 4

baroreceptor reflex:

baroreceptor detect blood pressure

integrating centre looks at the information

coordinates a sympathetic and parasympathetic outflow to vary heart rate, strength of contraction, and constriction of blood vessels accordingly

Question 5

Describe the effect the autonomic innervation on major organs

Answer 5

Activation of the SNS leads to a state of overall elevated activity and attention: the “fight or flight” response, In this process, blood pressure and heart rate increase, glycogenolysis ensues, gastrointestinal peristalsis ceases, etc The SNS innervates nearly every living tissue in the body

The PNS promotes the “rest and digest” processes; heart rate and blood pressure lower, gastrointestinal peristalsis/digestion restarts, etc.
The PNS innervates only the head, viscera, and external genitalia, notably vacant in much of the musculoskeletal system and skin, making it significantly smaller than the SNS