Biochem In Person

Question 1

Which of these statements is true about phase 2 of the action potential?
A. Na+ and Ca2+ are the primary permeating ions
B. Na+ and K+ are the primary permeating ions
C. Ca2+ and K+ are the primary permeating ions
D. Ca2+ is the only permeating ion

Answer 1

C. Ca2+ and K+ are the primary permeating ions

Question 2

What causes the action potential to transition from phase 2 to phase 3?

Answer 2

Ca2+ channels inactivate meaning a high proportion of the membrane current is K+. Ca2+ channels then shut more because of the membrane potential polarisation

Question 3

Which of the following ionic concentrations best represents the resting concentration of calcium in a cardiac cell?
A. 1000nm
B. 100nm
C. 0.1um
D. 1um

Answer 3

B. 100nm
C. 0.1um

Question 4

What is the reason for a prolonged cardiac action potential in the myocardium?

Answer 4

To give an ordered depolarisation and long enough time for the increase in calcium to trigger a coordinated contraction

Question 5

Do vascular smooth muscle cells fire action potentials?

Answer 5

Generally no, but some venous tissue may

Question 6

Describe the vascular smooth muscle membrane potential

Answer 6

VSM cells rest between -55 and -45 mV to allow them to be partially constricted