Autonomic Nervous System 1

Question 1

What does the ANS do?

Answer 1

ANS controls all involuntary functions (heart rate, blood pressure, GI motility, iris diameter)
The ANS is separate from the somatic motor system
It is entirely efferent but regulated by afferent inputs.

Question 2

What systems are there in the ANS?

Answer 2

Sympathetic
Parasympathetic
Enteric

Question 3

What is the sympathetic nervous system?

Answer 3

A fight or flight. Increases heart rate, force of contraction and blood pressure.

Question 4

What is the parasympathetic nervous system?

Answer 4

Rest and digest. Regulates basal activities like basal heart rate.

Question 5

What are the division of the brain stem and spinal cord?

Answer 5

M - medullary
C - cranial
T - thoracic
L - lumbar
S - sacral

Question 6

How does the sympathetic nervous system differ to the parasympathetic structurally?

Answer 6

The sympathetic nervous system has a short preganglionic nerve fibre and a long postganglionic.
The parasympathetic has a long preganglionic nerve fibre and short post ganglionic.

Question 7

What is the main structural difference between postganglionic and preganglionic fibres?

Answer 7

Preganglionic are myelinated

Postganglionic are not myelinated

Question 8

What anatomical divisions connect to the PNS?

Answer 8

M - medullary
S - sacral
going via vagus nerve in M

Question 9

Give some features of the parasympathetic nerves.

Answer 9

Originate in the lateral horn of the medulla and the sacral spinal cord.
Long myelinated preganglionic fibres
Short unmyelinated postganglionic fibres
Ganglia are located within the innervated tissues
Have actions that oppose the sympathetic nervous system.

Question 10

Give some features of the sympathetic nerves.

Answer 10

Originate in the lateral horn of the lumbar and thoracic spinal cord.
Short myelinated preganglionic fibres
Long unmyelinated postganglionic fibres
Ganglia are located in the paravertebral chain close to the spinal cord (spinal nerve)
Have actions that oppose the parasympathetic nervous system.

Question 11

Which are the most common neurotransmitters in the ANS?

Answer 11

Acetylcholine and noradrenaline

Question 12

What neurotransmitters do all pre-ganglionic neurones use?

Answer 12

They use acetylcholine as their neurotransmitter

Question 13

All pre-ganglionic neurones are cholinergic. What does this mean?

Answer 13

That they use acetylcholine as their neurotransmitter.

nAChR and mAChR are also cholinergic receptors.

Question 14

What types of receptors are found in the post ganglionic fibres?

Answer 14

Nicotinic acetylcholine receptors at the neuromuscular junction for example.

Question 15

What types of channels are nicotinic acetylcholine receptors?

Answer 15

Ligand-gated channel ions

Question 16

What types of channels are muscarinic acetylcholine receptors?

Answer 16

GPCRs

Question 17

Look at page 13.

Answer 17

Yup.

Question 18

What types of receptors are also found in the parasympathetic post-ganglionic neurones?

Answer 18

Muscarinic acetylcholine receptors

Question 19

What is the main types of receptors found in sympathetic post-ganglionic neurones?

Answer 19

Noradrenergic receptors

Question 20

What are noradrenergic receptors?

Answer 20

GPCRs that use noradrenaline as their primary neurotransmitter.

Question 21

What are the two major classes of adrenoceptors (noradrenergic)?

Answer 21

alpha and beta adrenoceptors:
a1
a2
b1
b2
(b3)

Question 22

Give examples of sympathetic post-ganglionic neurones that are cholinergic instead of noradrenergic.

Answer 22

Innervating sweat glands and hair follicles.

Question 23

They are non-adrenergic and non-cholinergic transmitters as well in the ANS. Give some examples.

Answer 23

ATP
Nitric Oxide
Serotonin
Neuropeptides like VIP and substance P

Question 24

How are the sympathetic postganglionic neurones in the adrenal glands different?

Answer 24

They differentiate to form neurosecretory chromatin cells.
Chromaffin cells can be considered as postganglionic sympathetic neurones that do not project to a target tissue.
This also means that there is no ganglion found in the spinal nerve. The chromaffin cells work as their own ganglion.

Question 25

What do chromaffin cells release?

Answer 25

By sympathetic stimulation they release adrenaline as a hormone into the bloodstream.

Question 26

Where are chromaffin cells found?

Answer 26

In the adrenal medulla.

Question 27

Look at page 21.

Answer 27

Yup.

Question 28

Give examples of what parasympathetic release of ACh causes.

Answer 28

Heart (M2) - bradycardia and reduced cardiac conduction velocity
Smooth muscle:
bronchial/bronchiolar contraction (M3)
GI-motility
Bladder contraction and relaxation
Penile erection
Ciliary muscle and iris sphincter
Glandular:
Increased sweat/salivary/lacrimal secretion (M1/M3)

Question 29

Give examples of what sympathetic release of noradrenaline causes.

Answer 29

Heart: (b1)
Tachycardia
Positive inotropy
Smooth muscle:
Arteriolar contraction/venous contraction (a1,b2)
Bronchiolar/intestinal/uterine relaxation (b2)
Bladder sphincter contraction
Radial muscle contraction
Glandular:
Increased viscous secretion
Kidney:
Renin release

Question 30

How does vasoconstriction happen by the sympathetic nervous system?

Answer 30

By release of adrenaline or noradrenaline that binds to alpha1 adrenoceptors. This causes vasoconstriction.

Question 31

Nor/adrenaline also causes vasodilation by the sympathetic nervous system. How does this work when it also causes vasoconstriction?

Answer 31

alpha1 adrenoceptors are responsible for vasoconstriction. beta2 adrenoceptors are responsible for vasodilation. These two types of adrenoceptors are not found in the same tissues and organs in the body. For example alpha1 adrenoceptors are found in the skin, sphincters, brain, GI-system, kidney etc. These are organs you don’t need to work during fight or flight.