electrical activity of the heart

Question 1

how is cardiac muscle electrically connected

Answer 1

gap junctions

Question 2

how is cardiac muscle physically connected

Answer 2

desmosomes

Question 3

intercalated discs

Answer 3

gap junction + desmosome

Question 4

cardiac muscle action potential

Answer 4

long - ~250m/s

long refractory period to can’t have tetanic contraction

Question 5

what regulates contraction

Answer 5

Ca2+ entry from outside cell

used to vary strength of contraction as does not saturate troponin

Question 6

pacemakers

Answer 6

unstable resting membrane potential and may spontaneously depolarise

Question 7

non pacemaker AP

Answer 7

resting membrane potential (high K+)
initial depolarisation (inc Na+)
plateua (inc Ca, dec K)
repolarisation (decrease Ca and increase K)

Question 8

pacemaker action potential

Answer 8

pacemaker potential

gradual decrease K, early increase Na, late increase Ca2+

Question 9

modulators of electrical activity

Answer 9

sympathetic + parasympathetic
drugs - CCB
temp 
hyperkalemia 
hypokalaeia 
hypercalcaemia 
hypocalcamia

Question 10

modulators of electrical activity: CCB

Answer 10

decrease force of contraction

Question 11

modulators of electrical activity: cardiac glycosides

Answer 11

inc force of contraction

Question 12

modulators of electrical activity: temperatire

Answer 12

increases ~10beats/min/degree C

Question 13

modulators of electrical activity: hyperkalaemia

Answer 13

fibrillation and heart block

Question 14

modulators of electrical activity: hypohalaemia

Answer 14

fibrillation and heart block

Question 15

modulators of electrical activity: hypercalaemia

Answer 15

increased HR and force of contraction

Question 16

modulators of electrical activity: hypocalcemia

Answer 16

decreased HR and force of contraction

Question 17

special conducting system

Answer 17

sinoatrial node
atriovenricular node
bundle of his
purkinje fibres