ANS

Question 1

What is the ANS?

Answer 1

Autonomic Nervous System
- Sub-division of the PNS
- Unconscious control

Question 2

What are the 2 divisions of the ANS?

Answer 2

1. Sensory —> somatic
   —> visceral
2. Motor —> somatic
   —> visceral —> sympathetic
   —> parasympathetic

Question 3

What is the difference between sympathetic and parasympathetic neurones?

Answer 3

Sympathetic —> Fight or Flight
- short pre-g, long post-g
- pre-g —> nAChr (ion)
post-g —> muscarinic NAr (G-coupled)

Parasympathetic —> Rest and Digest
- long pre-g, short post-g
- pre-g —> nAChr
post-g —> muscarinic ACHr

Question 4

What is special about ANS control of blood vessel tone?

Answer 4

Only sympathetic nervous control (SNS)
- both constriction and dilation

Question 5

How do visceral motor neurones of the ANS work?

Answer 5

Visceral motor nuclei start in hypothalamus —> project to brainstem/spinal cord —> synapse with autonomic neurones

Question 6

What is special about ANS control of the adrenal gland?

Answer 6

Only 1 fibre
- Sympathetic nerve —> adrenal gland —> adrenaline
straight to blood (no ‘post-g’)

Question 7

What is special about ANS control of the GI system?

Answer 7

Sympathetic/parasympathetic neurones interact with own enteric nervous system

Question 8

What is special about ANS control of the lungs?

Answer 8

No sympathetic neurones
- Parasympathetic —> dec
- Adrenal gland —> inc

Question 9

How does the ANS control the bladder?

Answer 9

Micturition reflex:
High pressure in bladder —> need to urinate —> choose whether to urinate (voluntary aspect)
- parasympathetic —> detrusor muscle contracts —>
hold urine in
- sympathetic —> detrusor muscle relaxes —>
let urine pass

Question 10

Which receptors are present at pre-ganglionic neurones?

Answer 10

Parasympathetic —> nACh r (ion - Na+)
Sympathetic —> nACh r
Adrenal gland —> nACh r

Question 11

Which receptors are present at post-ganglionic neurones?

Answer 11

Parasympathetic —> muscarinic ACh r (G-coupled)
Sympathetic —> adrenergic r (G-coupled)

Question 12

How does neurotransmission occur for acetylcholine?

Answer 12

1. ACh production:
   
   • Choline into pre-s n —> reacts with acetyl CoA via
     choline acetyl transferase —> ACh
2. Vesicles:
   
   • ACh into vesicles
3. Exocytosis:
   
   • Na+ influx depolarises pre-s n —> Ca2+ in —>
     vesicle exocytosis —> ACh across synapse
4. Receptor activation:
   
   • ACh binds to ACh receptor (nicotinic if pre-g,
     muscarinic if post-g) —> AP in post-s n
5. Receptor inactivation:
   
   • ACh leaves receptor —> breakdown via
     acetylcholinesterase in synapse —> choline back
     to pre-s n or glial cell via choline uptake proteins

Question 13

How does neurotransmission occur for noradrenaline?

Answer 13

1. NA production:
   
   • Tyrosine into pre-s n —> converted to DOPA via
     tyrosine hydroxylase —> converted to dopamine
     via DOPA decarboxylase
2. Vesicles:
   
   • Dopamine into vesicles with dopamine β
     hydroxylase —> NA in vesicles
3. Exocytosis:
   
   • Na+ influx depolarises pre-s n —> Ca2+ in —>
     vesicle exocytosis —> NA across synapse
4. Receptor activation:
   
   • NA binds to adrenergic receptor —> AP in post-s n
5. Receptor inactivation:
   
   • NA leaves receptor —> NA back to pre-s n or glial
     cell —> breakdown via MOA-O in pre-s n or COMT
     in glial

Question 14

How does neurotransmission occur for adrenaline in the adrenal medulla?

Answer 14

1. NA production:
   
   • Tyrosine into neurone —> converted to DOPA via
     tyrosine hydroxylase —> converted to dopamine
     via DOPA decarboxylase
2. Vesicles:
   
   • Dopamine into vesicles with dopamine β
     hydroxylase —> NA in vesicles
3. Exocytosis:
   
   • Na+ influx depolarises neurone —> Ca2+ in —>
     NA release to cytoplasm —> converted to
     adrenaline by phenylethanol methyl tranferase
4. Adrenaline out neurone —> into blood

Question 15

What are the 2 main differences between ACh and NA receptors?

Answer 15

1. Production
   
   • ACh —> 1 reaction
     - choline + acetyl CoA —> ACh
     (choline acetyl transferase)
   • NA —> many reactions
     - tyrosine —> DOPA
     (tyrosine hydroxylase)
     - DOPA —> dopamine
     (DOPA decarboxylase)
     - dopamine —> NA
     (dopamine β hydroxylase)
2. Metabolism
   
   • ACh —> in synapse
   • NA —> in pre-s n/glial cell