Question

Please answer all parts. Thanks in advance

19) Which statement(s) is(are) NOT true regarding cardiac muscle? Choose ALL that apply. (2.5 pts) a) Autorhythmic cells do not contribute significantly to the force of heart contraction because they do not contain many myofibrils. b) Cardiac muscle consists of autorhythmic fibers and contractile fibers. c) Cardiac muscle is similar to skeletal muscle since t contains thick and thin filaments, d) Cardiac muscle is similar to skeletal muscle in that the muscle fibers function independently of e Cardiac muscle is similar to skeletal muscle in that an external stimulus is required for muscle sarcoplasmic reticulum, and T tubules. one another fibers to contract. 20) Autorhythmic cardiac muscle fibers lack which of the following electrical events? (2 points) a) depolarizing phase b) pacemaker potential c) plateau potential d) repolarizing phase e) They have all of these electrical events. 21) The depolarizing phase of the action potential in an autorhythmic cell is due to opening of what type of channel? (2 points) a) sodium (If) b) voltage-gated calcium c) fast voltage-gated potassium d) slow voltage-gated potassium

Answer 1

19) Right option is e) cardiac muscle is similar to skeletal muscles in that an external stimulus is required for muscle fibers to contract.

Because cardiac mussels doesn't require any external stimulus to contact as the they are auto stimulatory, the pacemaker cells of cardiac muscle stimulates them to contract.

20) Right option is (b)

Because, they have a resting potential which is unstable called pacemaker cells.

Immediately after the repolarization of previous action potential the depolarization started by the combination of Ca+ and slow Na+ channels.

But there no plateau potential , which required to prolong the contractions of cardiac muscle which is a property of contractile cells.

21) right option is (b)  

The the combination of Ca+ and slow Na+ channels lead the autorythamic cells to depolarization immediately after the realization of previous action potential.