Dr Gawad Physiology Course Online Exam - Excitable – Course Lecture 6

2.

About the of skeletal muscles, all the following is true except:

Hypertrophy develops as a result of forced repeated contractions.
The function of the T system is the rapid transmission of the action potential from the cell -membrane to inside the muscle fibre
After the spike potential, the muscle excitability is abolished
Acetylcholine released at the M.E.P. is rapidly hydrolyzed by cholinesterase.

Correct Answer

A. After the spike potential, the muscle excitability is abolished

Explanation

After the spike potential, the muscle excitability is not abolished. In fact, after the spike potential, the muscle excitability is increased. This is due to the release of calcium ions from the sarcoplasmic reticulum, which triggers muscle contraction. Therefore, the statement "After the spike potential, the muscle excitability is abolished" is not true.

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3.

Among the steps of skeletal muscle relaxation:

Inward spread of the depolarization wave along the transverse tubules.
Pumping of Ca back into the sarcoplasmic reticulum.
Release of Ca from the sarcoplasmic reticulum.
Binding of Ca to troponin C.

Correct Answer

A. Pumping of Ca back into the sarcoplasmic reticulum.

Explanation

During skeletal muscle relaxation, one of the steps involves the pumping of calcium (Ca) back into the sarcoplasmic reticulum. This process is essential for muscle relaxation as it helps to decrease the concentration of Ca in the cytoplasm. When the muscle is contracted, Ca is released from the sarcoplasmic reticulum, which allows for the binding of Ca to troponin C, leading to muscle contraction. However, during relaxation, the Ca needs to be removed from the cytoplasm to allow the muscle to return to its resting state. The pumping of Ca back into the sarcoplasmic reticulum helps to achieve this and allows for the muscle to relax.

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4.

Concerning isometric and isotonic muscle contractions:

In isometric contraction, the elastic elements are not stretched.
During isometric contraction a load is moved and work is done.
During isotonic contraction most of the energy transformed into heat.
During isotonic contraction the muscle length is not changed.

Correct Answer

A. During isotonic contraction most of the energy transformed into heat.

Explanation

During isotonic muscle contraction, most of the energy is transformed into heat. Isotonic contraction refers to a type of muscle contraction where the muscle length changes while maintaining a constant tension. This type of contraction is responsible for movement and work done by the muscles. As the muscle contracts and shortens, it generates heat due to metabolic processes and energy expenditure. Therefore, during isotonic contraction, a significant amount of energy is converted into heat.

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5.

In skeletal muscles:

The initiation of contraction occurs by binding of Ca to tropomyosin.
The action potential follows the work done.
The one way conduction at the M.E.P. is due to location of the chemical mediator (acetylcholine) in the nerve terminals.
Fatigue sets in after fatigue occurs in the nerves.

Correct Answer

A. The one way conduction at the M.E.P. is due to location of the chemical mediator (acetylcholine) in the nerve terminals.

Explanation

The correct answer states that the one-way conduction at the M.E.P. (motor end plate) is due to the location of the chemical mediator, acetylcholine, in the nerve terminals. This means that acetylcholine is released from the nerve terminals and binds to receptors on the motor end plate, triggering muscle contraction. This one-way conduction ensures that the signal travels in only one direction, from the nerve to the muscle, allowing for precise control of muscle movement.

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6.

A series of stimuli that cause summation of contractions leads to:

Rigor.
Contracture.
Tonus.
Tetanus
Spasm.

Correct Answer

A. Tetanus

Explanation

When a series of stimuli causes summation of contractions, it leads to tetanus. Tetanus is a sustained contraction of a muscle due to a rapid succession of stimuli. In this state, the muscle remains contracted and does not relax. This can occur naturally during certain activities or can be artificially induced in medical procedures. It is different from contracture, which refers to a prolonged muscle contraction due to a lack of relaxation, and tonus, which is the normal level of tension in a muscle at rest. Rigor refers to a stiffening of muscles after death, and spasm is an involuntary and sudden contraction of a muscle.

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7.

Regarding reaction of degeneration, which of the following is true:

There is increased muscle excitability
Skeletal muscle responds to both faradic and galvanic current
Skeletal muscle has longer chronaxie
ACC is lower than CCC

Correct Answer

A. Skeletal muscle has longer chronaxie

Explanation

The chronaxie is the minimum duration of an electrical stimulus required to elicit a response in a muscle or nerve. In the case of the reaction of degeneration, which occurs in damaged or denervated muscles, the muscle has a longer chronaxie. This means that it requires a longer duration of electrical stimulus to cause a contraction in the muscle. This is due to the loss of normal muscle innervation and the changes that occur in the muscle fibers as a result.

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Dr Gawad Physiology Course Online Exam - Excitable – Course Lecture 6

During muscle contraction, all the following is true except:

Quiz Preview

About the of skeletal muscles, all the following is true except:

Among the steps of skeletal muscle relaxation:

Concerning isometric and isotonic muscle contractions:

In skeletal muscles:

A series of stimuli that cause summation of contractions leads to:

Regarding reaction of degeneration, which of the following is true: