Autonomic Nervous System (ANS)

Question 1

What is the autonomic nervous system (ANS)?

Answer 1

Subconscious ability to adapt to environmental stressors and other challenges

Innervate all tissues other than skeletal muscle (motor)

It is efferent (conducts outwardly)

Question 2

What are the three divisions of the autonomic nervous system?

Answer 2

Sympathetic
Parasympathetic
Enteric

Question 3

What is the enteric division?

Answer 3

A specialised nerve network in the wall of the intestinal tract which regulates the glands and smooth muscles in that area

Question 4

What are the functions of the ANS and, specifically, the sympathetic and parasympathetic divisions?

Answer 4

ANS = maintain homeostasis
Sympathetic = fight or flight response
Parasympathetic = rest and digest

Question 5

What is the structure of the ANS?

Answer 5

A cell cluster with many neurons and synapses called the ganglion is the first junction between the central nervous system to various effector sites

The myelinated postganglionic axon connects to the CNS

The unmyelinated postganglionic axon connects to effectors

Sympathetic has a shorter preganglionic axon, whereas parasympathetic has a longer preganglionic axon

Question 6

What are the major neurotransmitters for the ANS?

Answer 6

Acetylcholine = inhibiting / calming effect

Norepinephrine / noradrenaline = stimulating effect

Question 7

What are the differences in neurotransmitters between the sympathetic and parasympathetic divisions?

Answer 7

Preganglionic neurons = always secrete acetylcholine

Sympathetic
Secretes acetylcholine at the ganglion, this acts on the postganglionic axon to secrete norepinephrine at the effector site
The preganglionic nerves can also use acetylcholine to activate the adrenal medulla to secrete epinephrine and norepinephrine which will act on various tissues etc

Parasympathetic
Acetylcholine is secreted at both the preganglionic nerves and postganglionic nerves

Question 8

What are the different receptors found in the ANS for acetylcholine and norepinephrine / noradrenaline?

Answer 8

Acetylcholine receptors = nicotinic receptors (postganglionic neurons) and muscarinic receptors (inhibitory cardiac muscle and arterial smooth muscle)

Norepinephrine / noradrenaline receptors = adrenergic receptors (effects impacted by receptor subtype and by second messengers)

Question 9

What is the purpose of putting adrenaline in LA such as lignocaine?

Answer 9

Inhibits blood flow and so allows the LA to linger longer