Autonomic Nervous System

Question 1

What does the autonomic nervous system control?

Answer 1

• the ANS controls non-skeletal peripheral function:
• cardiac muscle
• smooth muscle
• internal organs
• skin

Question 2

What is the parasympathetic NS otherwise known as?

Answer 2

“rest and digest”

‘P’ for ‘potato couch’ therefore rest and digest

Question 3

What is the sympathetic NS otherwise known as?

Answer 3

“fight or flight”

Question 4

What effect does the Parasympathetic/Sympathetic NS have on:

a) the heart
b) the stomach
c) the pupil
d) salivary glands
e) lungs
f) GIT
g) liver
h) bladder

Answer 4

Parasympathetic NS:

a) decreases rate and contractility
b) increases motility and secretions
c) constriction
d) increase secretions
e) constriction
f) increase motility and secretions
g) increase bile release
h) constriction

Sympathetic NS:

a) increases rate and contractility
b) decreases motility and secretions
c) dilation
d) decrease secretion
e) dilation
f) decrease motility and secretions
g) increase glucose release
h) relaxation

Question 5

What is relationship between the baroreceptors firing rate and the visceral motors?

Answer 5

• baroreceptors measure blood pressure
• if the baroreceptors firing rate increases, the parasympathetic NS activity increases, slowing the heart rate
• if the baroreceptors firing rate increases, the SNS is inhibited(if bp too how, SNS is LESS inhibited)

Question 6

Where do the visceral motor nuclei originate in?

Answer 6

-the hypothalamus

Question 7

Tell me about the pre- and post-ganglionic neurons in the PNS vs SNS vs Adrenal gland

Answer 7

PNS:

• long pre-ganglionic fibres
• ganglions close to (or embedded within) effector tissues
• short post-ganglionic fibres

SNS:

• short pre-ganglionic fibres
• ganglions close to the originating site of the pre-ganglionic neuron
• long post-ganglionic fibres

(This is because sympathetic responses are often a lot more coordinated in the ‘fight or flight response.’ Parasympathetic is mainly discrete.)

Adrenal Gland:
-only one sympathetic nerve to the adrenal gland

Question 8

Which neurotransmitters are release by the pre- and post ganglionic neurons in the PNS and SNS?

Answer 8

• ACh by the pre-ganglionic P, by the post-ganglionic P and the pre-ganglionic S
• NA by the post-ganglionic sympathetic

(Ash is the same neurotransmitter released in both ganglion since all you need to do is transmit the signal from one neurone to the next. Post-Ganglionic fibres P and S need to have different effects, therefore need different neurotransmitter to meditate these effects).

Question 9

What effect would a drop in blood pressure have on the ANS function to the heart?

Answer 9

• lose parasympathetic effects

- less inhibition of the sympathetic in order to increase the heart rate

Question 10

What effect would the smell of food have on the ANS function to the stomach?

Answer 10

• parasympathetic becomes dominant (in order to increase function of GIT and stomach
• enteric nervous system has influence over the gut function i.e it is the ‘min-brain’ of the GIT)

Question 11

What effect would exposure to bright light have on the ANS function to the pupil?

Answer 11

-need constriction so parasympathetic becomes dominant

Question 12

Why is the regulation of function of the lung an unusual situation?

Answer 12

• only parasympathetic nerves innervate the lung tissue-
• no sympathetic neurons
• the sympathetic control (constriction) is done via adrenaline secretion
• control via hormone, not neurotransmitter

Question 13

Tell me about the micturition reflex.

Answer 13

• controls the bladder
• pressure builds up in bladder
• parasympathetic stimulated, causing the detrusor muscle to contract
• sympathetic inhibited so the internal sphincter muscle relaxes, allowing urine out
• there is also somatic motor control- conscious control of the internal sphincter

Question 14

What type of receptor is at the autonomic ganglia (from pre-ganglionic fibres) and adrenal gland?

Answer 14

• Nicotine acetylcholine receptor nACh mediate responses to ACh
• Ion channel receptor because it is a fast response

Question 15

What receptors mediate the effects of neurotransmitters released from post ganglionic fibres?

Answer 15

• G-protein coupled receptor
• slow response (sec/mins)
• Muscarinic receptors for ACh at parasympathetic
• Adrenergic receptors for NA at sympathetic
• effector may be enzymes (e.g adenyl cyclise) or channels (Ca or K)

Question 16

What is the sequence of events for biosynthesis and metabolism of Acetylcholine ?

Answer 16

1. Choline (from diet) combined with acetylcholine CoA by choline acetyl transferase
2. ACh packaged into vesicles
3. Depolarisation causes Ca influx and exocytosis
4. Exocytosis and neurotransmitter release
5. Muscarinic or nicotinic receptor activation
6. ACh rapidly degraded by acetylcholineesterase in the synapse. Choline then taken up into presynaptic terminal or glial cell

Question 17

What is the sequence of events for the biosynthesis and metabolism of Noradrenaline?

Answer 17

1. Tyrosine (from diet) converted to DOPA by tyrosine hydroxylase. DOPA converted to dopamine by DOPA decarboxylase
2. Dopamine packaged into vesicles with dopamine B hydroxylase. NA made.
3. Depolarisation cause Ca influx and exocytosis
4. Exocytosis and neurotransmitter release
5. Adregernic receptors activated
6. Removal of NA via uptake into presynaptic terminal then metabolised by MOA-O enzyme, or glial cells then metabolised by COMT enzyme.

Question 18

What is the sequence of events for the biosynthesis and metabolism of adrenaline?

Answer 18

1. Tyrosine (from diet) converted to DOPA by tyrosine hydroxylase. DOPA converted to dopamine by DOPA decarboxylase
2. Dopamine packaged into vesicles with dopamine B hydroxylase. NA made.
3. NA converted to adrenaline in the cytoplasm by phenylethanol methyl transferase
4. Depolarisation causes Ca influx and exocytosis
5. Adrenaline diffuses into the capillary and is transported to tissues in the blood