Bio 130 Chapter 9 Quiz (Muscle Physiology)

The downward curve back to the baseline of a myogram represents the relaxation period. During this period, the muscle fibers are no longer contracting and are returning to their resting state. This is characterized by a decrease in tension and the muscle lengthening. The relaxation period is important for allowing the muscle to recover and prepare for the next contraction.

During the contraction period, muscle tension increases. This is the phase when the muscle fibers are actively shortening and generating force. The contraction period follows the latent period, during which the muscle is preparing for contraction, and precedes the relaxation period, when the muscle fibers are returning to their resting length. The threshold stimulus is the minimum level of stimulation required to elicit a muscle contraction, but it does not specifically refer to a period of time.

The latent period refers to the time delay between the stimulation of a muscle and the onset of a response. During this period, there is no visible muscle contraction as the muscle is preparing for contraction by releasing calcium ions and generating action potentials. This delay allows for the necessary processes to take place before the actual contraction occurs. Therefore, the latent period represents the time it takes for the muscle to respond after being stimulated.

The correct answer is "All-or-None law." This law states that when a muscle fiber is stimulated to contract, it will contract fully and with maximum force, or it will not contract at all. This means that the strength of muscle contraction does not depend on the strength of the stimulus, but rather on whether or not the stimulus reaches the threshold required for contraction.

The correct answer is "Contration Period." This is the phase in muscle contraction where the muscle fibers are actively generating tension and shortening. It is represented by an upward sweeping line on a myogram because it shows the increase in muscle activity during this period. The myogram is a graphical representation of muscle contraction, with the contraction period being the phase where the muscle is actively contracting.

Wave summation is the process by which the force of a muscle contraction increases with each successive action potential, leading to a smooth and sustained contraction. This occurs due to the overlapping of twitches, which are individual contractions caused by a single action potential. Therefore, the correct answer, "Summation of Twitches," accurately describes the phenomenon of wave summation.

A muscle fiber remains unresponsive to stimuli until it reaches the threshold stimulus. The threshold stimulus is the minimum level of stimulation required to initiate a muscle contraction. Before reaching this threshold, the muscle fiber remains in a state of rest and does not respond to any stimuli. Once the threshold stimulus is reached, the muscle fiber will start to contract and respond to further stimulation.

Continuous stimulation at relaxation interrupting frequencies results in incomplete tetanus. In incomplete tetanus, the muscle fibers are stimulated rapidly, but with short breaks in between. This allows the muscle to partially relax before the next stimulus, resulting in sustained contractions with some degree of relaxation. In contrast, complete tetanus occurs when the muscle is stimulated at such a high frequency that it is unable to relax at all, leading to a continuous and sustained contraction.

Both options B and C, complete titanic contraction and complete tetanus, can result in a muscle being stimulated so often that the contraction period is interrupted. In complete titanic contraction, the muscle remains contracted without any relaxation, while in complete tetanus, the muscle is stimulated at such a high frequency that it reaches a state of continuous contraction without any relaxation. In both cases, the muscle is unable to complete its normal contraction and relaxation cycle, leading to an interrupted contraction period.

A twitch is the basic unit of a mechanical action with a skeletal muscle. It refers to a single contraction and relaxation cycle of a muscle fiber in response to a single electrical stimulus. This brief and rapid contraction is the smallest observable unit of muscle movement and is responsible for generating force and movement in the body.

Continuous stimulation at relaxation is displayed on a myogram as a staircase pattern. This is because during relaxation, the muscle fibers are able to partially recover before the next stimulus is applied. As a result, each subsequent contraction is slightly stronger than the previous one, creating a staircase-like pattern on the myogram. This phenomenon is known as treppe or the staircase effect.

When a contraction period is interrupted often, the myogram displays a smooth line. This is because interruptions in the contraction period prevent the muscle from fully contracting and relaxing, resulting in a smoother and less pronounced waveform on the myogram. The smooth line indicates a lack of strong and consistent muscle contractions, which can be caused by factors such as fatigue or nerve damage.