Physiology - Heart muscle

Question 1

what type of muscle is striated and branched with intercalated discs?

a. skeletal
b. cardiac
c. smooth

Answer 1

b.cardiac

Question 2

which type of muscle cell has a single nucleus and many mitochondria?

a. skeletal
b. cardiac
c. smooth

Answer 2

b.cardiac

Question 3

how is a resting potential established?

a. k+ leak out of the cell and Na+ does not leak in
b. K+ leaks into the cell and Na+ does not leak in
c. K+ and Na+ leak out of the cell

Answer 3

a.k+ leak out of the cell and Na+ does not leak in

Question 4

which type of cardiac cell is found in the SA and AV nodes?

a. pacemaker
b. non pacemaker

Answer 4

a.pacemaker

Question 5

what is the RMP of pacemaker cells found in the AV and SA nodes?

a. -52mV
b. varying
c. -92mV

Answer 5

b.varying

Question 6

what is the RMP of non pacemaker cells found in the atrial and ventricular myocardium ?

a. -52mV
b. varying
c. -92mV

Answer 6

c.-92 mV

Question 7

what happens to the Na+ channel at -70mV in non pacemaker cardiac cells?

a. open
b. close

Answer 7

a.open

Question 8

when do non pacemaker sodium channels close?

a. -30- -40mV
b. -40mV
c. -92 mV

Answer 8

a. -30- -40mV

Question 9

when do Ca2+ channels open in pacemaker muscle cells?

a. -30- -40mV
b. -40mV
c. -92 mV

Answer 9

b.-40mV

long lasting channels, current = IcaL

Question 10

what happens in phase 1 of the non pacemaker cell graph?

a. Na channels close, K+ channels open and Cl- channels open
b. slow prolonged opening of Ca2+ channels for plateau
c. further 2 k+ channels open
d. slow rise in Ca+ permeability and K+ permeability (creep potential)

Answer 10

a.Na channels close, K+ channels open and Cl- channels open

Question 11

Taking place in pacemaker muscle cells what causes the propagation of a creep potential?

a. opening of Na+ channel at -70mV
b. closure of Na + channel , opening of K+ channels (ITO) and Cl - channels (Icl)
c. long lasting calcium channels opening at -40mV
d. slow rise in Ca2+ permeability and K+ permeability - creep potential

Answer 11

d.slow rise in Ca2+ permeability and K+ permeability - creep potential

Question 12

the time after initial stimulation in which a muscle is unstimulable is known as what?

a. refractory period
n. recovery period
c. hyperpolarisation
d. tetanus

Answer 12

a.refractory period

Question 13

concentration of which ion going from 10-7 to 10-4 inside cells leads to heart muscle contraction?

a. sodium
b. chloride
c. calcium

Answer 13

c.calcium

Question 14

true or false cardiac muscle can produce a wide range of contraction strengths?

a. true
b. false

Answer 14

b.false

Cardiac muscle can not because all cells are linked (“functional syncitium”)

Question 15

what is the importance of a long refractory period in cardiac muscle?

a. prevents MI
b. prevents atrial fibrillation
c. prevents tetanic contractions

Answer 15

c.prevents tetanic contractions

Question 16

What happens to the heart in response to increased load?

a. atrophy
b. dystrophy
c. hypertrophy

Answer 16

c.hypertrophy

Question 17

What happens to the heart in Duchenne/ Becker muscular dystrophy?

a. heart muscle dystrophy
b. decreased heart size
c. increased heart size with hypertrophy
d. increased heart size without hypertrophy

Answer 17

d.increased heart size without hypertrophy

Question 18

what is the underlying cause of long QT syndrome?

a. enlarged heart without hypertrophy
b. problems with Na+ channels underlying depolarisation
c. problems with K+ channels underlying repolarisation

Answer 18

c.problems with K+ channels underlying repolarisation

Question 19

what properties does heart muscle possess that allow it to gain energy through aerobic means?

a. Hb and mitochindria
b. myoglobin and mitochondria
c. myoglobin and cox 3

Answer 19

b.myoglobin and mitochondria