Manganese ion blocks the calcium channels in the cardiac muscle membrane. How would the presence of

a. The heart rate would increase.

b. The heart would beat less forcefully.

c. The plateau phase of contraction would be shorter.

d. The refractory period would be shorter.

e. The contraction phase would be prolonged.

Manganese ion blocks the calcium channels in the cardiac muscle membrane. How would the presence of manga?

Basically, calcium ions stimulate contraction as it binds with troponin to expose actin musles to myosin, thus initiating a contraction of muscle fibers. Lesser entry of calcium ions due to blockage means:

i) There is a decrease number of muscle fibers contracting, thus a decrease in muscle contraction. Therefore, the heart will beat less forcefully.

ii) As the heart beat less forcefully, the cardiac output will decrease. Thus, the body%26#039;s autonomic nervous system will act to stimulate the heart to beat faster as to restore the cardia output to a normal level. Therefore, the heart rate will increase.

Since the calcium ions are blocked (not completely by manganese), the entry of calcium ions are slow, so the contraction phase would be prolonged. Such %26#039;delay%26#039; can actually cause more calcium ions to enter, although not as much as it normally would.

Lastly, the calcium ions exit through a sodium-calcium pump. Since it is not affected, it would transport out calcium ions as usual. As there are lesser calcium ions in heart cells, the calcium ions are pumped out relatively quicker, thus the refractory period would be shorter. The same applies to the plateau phase too.

Manganese ion blocks the calcium channels in the cardiac muscle membrane. How would the presence of manga?

1. This should be under homework help.

2. Think about it.

If manganese blocks calcium channels in the cardiac muscle membrane. The cardiac action potential is largely sensitive to calcium influx and contributes to a longer action potential seen in cardiac muscle compared to skeletal muscle in order to adequately ventilate the cells so that sufficient oxygen can be distributed throughout the body. And since this ion BLOCKS this.. the reverse effect would occur.

e. the contraction phase would be shorter.. not longer.. so e is eliminated

d.. refractory period is the length of time between 2 action potentials where an action potential can not occur or a larger than normal stimulus is required. theres no effect on this. so d is eliminated

c.. yup yup yup

b.. nope nope..

a.. its blockin the ap.. so how would it increase?

best answer: c.