Physiology: sympathetic & parasympathetic control of HR

Question 1

what parts of the heart does the parasympathetic nerves supply

Answer 1

SA node and AV node

Question 2

what parts of the heart does the sympathetic nerves supply

Answer 2

SA node, AV node and myocardium

Question 3

what effect parasympathetic nerve supply have in resting conditions

Answer 3

vagal tone(parasympathetics) dominates over sympathetic and reduces HR from 100 to 60bpm

Question 4

what effect does vagal(parasympathetic) stimulation have on the heart

Answer 4

decreases HR and increases AV nodal conduction delay

Question 5

what neurotransmitter is used in parasympathetic supply of heart

Answer 5

ACh acting through muscarinic(M2) receptor

Question 6

what neurotransmitter is used in sympathetic supply of heart

Answer 6

Noradrenaline via b1 adrenoreceptor

Question 7

what effect does sympathetic stimulation have on the heart

Answer 7

increases HR and decreases AV nodal conduction delay

Question 8

describe the effect of vagal stimulation on the pacemaker action potential

Answer 8

causes pacemaker to take longer to reach threshold, slope of pacemaker potential decreases
action potential occurs less frequently

Question 9

describe the effect of sympathetic stimulation on the pacemaker action potential

Answer 9

slope of pacemaker potential increases
reaches threshold quicker
action potentials occur more frequently

Question 10

describe the inotropic and chronotropic effects of the parasympathetic stimulation

Answer 10

negative chronotropic effect

insignificant inotropic effect

Question 11

describe the inotropic and chronotropic effects of the sympathetic stimulation

Answer 11

positive chronotropic effect

positive inotropic effect