Physiology

Question 1

where does excitation of the heart originate from? and what cells?

Answer 1

Sino-atrial node

pacemaker cells

Question 2

location of SA node

Answer 2

in the right atrium (close to where superior vena cava enteres

Question 3

what is the pacemaker potential?

Answer 3

occurs in the cells of SA node
the unstable membrane potential
(gradually depolarisation till threshold)

Question 4

what causes the pacemaker potential?

Answer 4

the decrease in K+ efflux and increase in Na+ influx

Question 5

what happens once membrane potential reaches threshold?

Answer 5

there is a transient influx of Ca2+ causing depolarisation

Question 6

where is the AV node located?

Answer 6

at the base of the right atrium

Question 7

what is the purpose of a delay in the AV node conduction?

Answer 7

to allow all the blood to enter the ventricle before ventricle systole

Question 8

what are the main phases of action potential in contractile cells?

Answer 8

phase 4- resting membrane potential
phase 0- depolarisation
phase 1- small repolarisation
phase 2- plateau phase
phase 3- repolarisation

Question 9

action potentials in contractile cells phase 4?

Answer 9

resting membrane potential due to K+ efflux

Question 10

AP in contractile cells phase 0?

Answer 10

depolarisation caused by Na+ influx

Question 11

AP in contractile cells phase 1?

Answer 11

little repolarisation caused by closure of Na+ channels and opening of K+ channels
K+ efflux is dominant

Question 12

AP in contractile cells phase 2?

Answer 12

plateau phase caused by Ca+ influx via L-type channels and K+ efflux simultaneous
essential to muscle contraction of heart

Question 13

AP in contractile cells phase 3?

Answer 13

repolarisation caused by closure of Ca+ channels and K+ efflux
3 types of K+ channels used

Question 14

what is the purpose of drugs that reduced the plateau phase of the AP?

Answer 14

reduces muscle contraction

Question 15

what are funny potassium channels?

Answer 15

K+ channels opened by hyperpolarisation

Question 16

what is a positive chronotropic effect?

Answer 16

an increase the number of AP causing more frequent contraction

Question 17

what is a positive inotropic effect?

Answer 17

an increase the strength of contraction

Question 18

what is a positive dromotropic?

Answer 18

an increase in the rate of AP

Question 19

what nerve dominates the heart under resting conditions?

Answer 19

Vagus nerve (CN X)
parasympathetic control on the heart

Question 20

what does the vagus nerve supply to in the heart?

Answer 20

SA node and AV node

Question 21

what exactly does vagus nerve stimulation do?

Answer 21

slows heart rate and increases the AV node delay

Question 22

what happens to the pacemaker potential slope in parasympathetic effects?

Answer 22

it decreases

Question 23

what do cardiac sympathetic nerves supply?

Answer 23

SA node, AV node and myocardium

Question 24

what is the neurotransmitter and receptor used in sympathetic response?

Answer 24

noradrenaline acting on B1 adrenoceptors

Question 25

in an ECG what does P wave mean?

Answer 25

Atrial Depolarisation

Question 26

in an ECG what is the QRS complex?

Answer 26

Ventricle Depolarisation

Question 27

in an ECG what is the T wave?

Answer 27

Ventricle Repolarisation