The ANS (new)

Question 1

where do parasympathetic and sympathetic nerves originate

Answer 1

parasympathetic nerves: originate in lateral horn of medulla and sacrum

sympathetic nerves: originate in lateral horn of thoracolumbar spinal cord

Question 2

name 2 differences between sympathetic and parasympathetic nerves

Answer 2

parasympathetic nerves
1- long myelinated pre-ganglionic fibres and short unmyelinated post-ganglionic fibres
2- ganglia within innervated tissue

sympathetic nerves
1- short myelinated pre-ganglionic fibres and long unmyelinated post-ganglionic fibres
2- ganglia within paravertebral chain

Question 3

describe the neutrotransmitters and receptors used by the ANS

Answer 3

parasympathetic NS

• pre-ganglionic n. releases ACh - acts on nAChR
• post-ganglionic n. releases ACh - act on mAChR

sympathetic NS

• pre-ganglionic n. releases ACh - acts on nAChR
• most post-ganglionic n. release NA - acts on adrenoRs
• post-ganglionic n. to glands release ACh - act on mAChR (M1)
• chromaffin cells of adrenal medulla (= modified post-ganglion n.) release adrenaline

Question 4

what type of Rs are nAChR, mAChR and adrenoRs

Answer 4

nAChR = ligand-gated
mAChR = GPCR
adrenoR = GPCR

Question 5

name the subtypes of mAChR, their location and effect of stimulation

Answer 5

M1: glands - increased sweat/salivation/lacrimation (stimulated by sympathetic NS)
M2: heart SAN - decreased HR
heart AVN - decreased atrioventricular conduction
M3: lung SM - bronchoconstriction
GI SM - intestinal mobility
M4
M5

Question 6

name the subtypes of adrenoR, their location and effect of stimulation

Answer 6

a1: vasculature SM - vasoconstriction
a2
B1: heart SAN - increased HR
      heart ventricles - increased inotropy
B2: lung SM - bronchodilation
       vasculature SM - vasodilation

Question 7

what are NANC NTs, give examples

Answer 7

non-adrenergic, non-cholinergic NTs, e.g. ATP, NO, D-HT, neuropeptide/substance P

Question 8

what is the effect of sympathetic NA stimulation of kidney

Answer 8

renin release

Question 9

Why does the sympathetic system increase vaso-/veno-constriction in some tissues but not others?

Answer 9

Prioritises blood flow:

• Promotes vasodilation in the brain, skeletal muscle and heart
• Promotes vasoconstriction of BVs to skin - minimises bleeding in injured
• Promotes vasoconstriction to non-essential function organs (e.g. GI tract)
• Promotes venoconstriction to increase cardiac return