Question

question 5
1 pts
the repolarization of the action potential involves the opening of
o chemically gated na+ channels.
o voltage-gated na+ channels
o chemically gated k+ channels
o voltage-gated k+ channels

question 6
1 pts
the type of muscle fibers that have only a single nucleus, both thick and thin filaments, but
no z discs, are
o skeletal
o cardiac
o smooth,
o cardiac and smooth.
o cardiac and skeletal.

Explanation:

• For the first question (action potential repolarization):
• Action potential repolarization is mainly due to the efflux of \(K^{+}\). Voltage - gated \(K^{+}\) channels open during repolarization. Chemically - gated channels are more involved in synaptic transmission (not the main event in action potential repolarization). Voltage - gated \(Na^{+}\) channels are mainly involved in depolarization.
• For the second question (muscle fiber type):
• Skeletal muscle fibers are multinucleated. Cardiac muscle fibers have one or two nuclei and have Z - discs. Smooth muscle fibers have a single nucleus, contain thick and thin filaments, and lack Z - discs.

Answer:

• Question 5: voltage - gated \(K^{+}\) channels.
• Question 6: smooth.