Question

Essay: Susie was hospitalized because she cut herself in an accident. Susie cut her nerve that supplies a muscle in her arm. Please explain to Susie because she is having a difficult time understanding why her muscle doesn’t work if she cut her nerve. You can do so by writing an essay on skeletal muscle excitation and contraction. You should be very detail and descriptive when explaining. Your essay should include and not be limited to the following events:

- describe excitation of the muscle fiber and the events at the neuromuscular junction starting with the release of the neurotransmitter to all the possible things that can occur to or from it

- generation of an action potential

- propagation along the sarcolemma

- the events that lead to the release of “certain” ions

- the events that take place inside the cell which lead to excitation contraction coupling and cross-bridge cycling in detail.

Answer 1

When an injury occurs, it causes fibers within the nerve to break.This may interfere with the nerve's ability to send or receive signals.Skeletal muscles contract and relax to mechanically move the body. Messages from the nervous system cause these muscle contractions. these contraction occurs through a process known as Excitation contraction coupling, the steps of this process is as follows.

Muscle contraction begins when the nervous system generates a signal. The signal, an impulse called an action potential, travels through a type of nerve cell called a motor neuron.

The signal than reaches the neuromuscular junction, this causes release of acetylcholine into motor end plate (neuromuscular junction)

Acetylcholine ininitates depolarization within the sarcolemma, which is spread through the muscle fiber via T-tubules.

Depolarization causes sarcoplasmic reticulum to release calcium ions, these calcium ions binds to troponin, which in turn causes tropomyosium to move this results in myosin head getting exposed, the actin head and myosin forms a cross bridge.

ATP hydrolysis cause myosin head to swivel and change shape myosin head binds to actin filament, the actin filament moves towards the center of sarcomere.

The sliding of actin along myosin shortens sarcolemma causing muscle contraction.

So if the nerve is cut off, as in this case, then there would be no flow of information or impulses across the nerve this would prevent depolarization from happening as result muscle contraction wont happen.