Autonomic nervous system

Question 1

What is the autonomic nervous system (ANS)?

Answer 1

A subdivision of the peripheral nervous system responsible for involuntary physiological functions.

Question 2

What are the two main divisions of the ANS?

Answer 2

Sympathetic (fight or flight) and parasympathetic (rest and digest).

Question 3

How many neurons are in the ANS pathway?

Answer 3

Two: a preganglionic neuron and a postganglionic neuron.

Question 4

Where do sympathetic nerves originate?

Answer 4

Thoracic lumbar region (T1–L2) of the spinal cord.

Question 5

Where do parasympathetic nerves originate?

Answer 5

Craniosacral region (cranial nerves III, VII, IX, X and S2–S4).

Question 6

Describe the fibre length in the sympathetic system.

Answer 6

Short preganglionic and long postganglionic fibres.

Question 7

Describe the fibre length in the parasympathetic system.

Answer 7

Long preganglionic and short postganglionic fibres.

Question 8

What are ganglia?

Answer 8

Clusters of neuron cell bodies where preganglionic neurons synapse with postganglionic neurons.

Question 9

What neurotransmitter is released by all preganglionic neurons?

Answer 9

Acetylcholine (ACh).

Question 10

What type of receptor is on postganglionic neurons?

Answer 10

Nicotinic cholinergic receptors (nAChRs).

Question 11

What neurotransmitter do parasympathetic postganglionic neurons release?

Answer 11

Acetylcholine (ACh).

Question 12

What receptors do parasympathetic postganglionic neurons act on?

Answer 12

Muscarinic cholinergic receptors.

Question 13

What neurotransmitter do most sympathetic postganglionic neurons release?

Answer 13

Norepinephrine (NE).

Question 14

What are the main adrenergic receptor types?

Answer 14

α1, α2, β1, β2, and β3.

Question 15

What does α1 receptor activation cause?

Answer 15

Vasoconstriction.

Question 16

What does β1 receptor activation cause?

Answer 16

Increased heart rate and contractility.

Question 17

What does β2 receptor activation cause?

Answer 17

Bronchodilation.

Question 18

How is ACh action terminated?

Answer 18

Enzymatic breakdown by acetylcholinesterase in the synaptic cleft.

Question 19

How is NE action terminated at synapses?

Answer 19

Reuptake via NET, metabolism by MAO or COMT.

Question 20

What enzyme metabolises NE in the neuron?

Answer 20

Monoamine oxidase (MAO).

Question 21

What enzyme metabolises NE in the liver or peripherally?

Answer 21

Catechol-O-methyltransferase (COMT).

Question 22

What is the adrenal medulla?

Answer 22

A modified sympathetic ganglion that releases NE and epinephrine into the bloodstream.

Question 23

What stimulates the adrenal medulla?

Answer 23

ACh acting on nicotinic receptors from preganglionic neurons.

Question 24

What is the result of adrenal medulla stimulation?

Answer 24

A global sympathetic response via circulating NE and epinephrine.

Question 25

What does the α2 receptor do presynaptically in the sympathetic?

Answer 25

Inhibits further NE release.

Question 26

What are the main functions of the parasympathetic system?

Answer 26

Pupil constriction, decreased heart rate, bronchoconstriction, increased GI motility, bladder contraction.

Question 27

What are the main functions of the sympathetic system?

Answer 27

Pupil dilation, increased heart rate, bronchodilation, decreased GI motility, bladder relaxation.

Question 28

What receptor controls pupil dilation?

Answer 28

α1 adrenergic receptor.

Question 29

What receptor controls pupil constriction?

Answer 29

M3 muscarinic receptor.

Question 30

What is the role of β3 receptors?

Answer 30

Lipolysis in adipose tissue.

Question 31

How does the body clear circulating NE and epinephrine?

Answer 31

Via MAO and COMT in the liver, kidneys, and GI tract.

Question 32

What is the effect of sympathetic stimulation on the bladder?

Answer 32

Relaxation of detrusor muscle and contraction of internal sphincter (β2, α1).

Question 33

What is the effect of parasympathetic stimulation on the bladder?

Answer 33

Contraction of detrusor muscle and relaxation of internal sphincter (M3).

Question 34

What is the clinical significance of autonomic drugs?

Answer 34

They can target receptors or enzymes to treat conditions like hypertension, asthma, and depression.

Question 35

How do β-blockers work?

Answer 35

By blocking β1 receptors in the heart to reduce heart rate and blood pressure.

Question 36

How do MAO inhibitors work?

Answer 36

They prevent breakdown of NE, increasing its availability in the synapse.

Question 37

What happens in adrenergic synapse if NET is blocked?

Answer 37

NE remains in the cleft longer, prolonging its effect.

Question 38

What is the function of sweat glands in sympathetic system?

Answer 38

Secrete sweat via muscarinic receptors using ACh.

Question 39

What type of receptor is used at adrenal medulla synapse?

Answer 39

Nicotinic cholinergic receptor.

Question 40

What are muscarinic receptors?

Answer 40

G protein-coupled receptors activated by ACh in parasympathetic system.