Anatomy Muscle Review Quiz

Actin is the name of the thin filament in muscle cells. It is a protein that plays a crucial role in muscle contraction. Actin filaments slide past myosin filaments during contraction, causing the muscle to shorten. ATP provides the energy for this sliding process, while calcium ions regulate the interaction between actin and myosin. However, the specific thin filament referred to in the question is actin.

At rest, myosin cannot pull on actin because tropomyosin is in the way. Tropomyosin is a protein that covers the binding sites on actin, preventing myosin from attaching and initiating muscle contraction. When calcium ions are released, they bind to troponin, causing a conformational change that moves tropomyosin away from the binding sites, allowing myosin to bind to actin and initiate muscle contraction. Therefore, myosin is unable to pull on actin when tropomyosin is in the way.

Myosin is the correct answer because it is the name of the thick filament in muscle cells. Thick filaments are responsible for generating the force required for muscle contraction. Myosin molecules have a long tail and a globular head, which interacts with actin filaments during the contraction process. Tropomyosin and troponin are proteins associated with actin filaments, but they are not the thick filament itself.

The sarcoplasmic reticulum holds calcium ions. Calcium ions play a crucial role in muscle contraction. When a muscle is stimulated, calcium ions are released from the sarcoplasmic reticulum into the muscle fibers. This release of calcium ions triggers a series of events that lead to muscle contraction. Without the sarcoplasmic reticulum holding calcium ions, muscle contraction would not be possible.

Depolarization refers to the reversal of electrical charge of the sarcolemma, which is the cell membrane of muscle fibers. During depolarization, the electrical charge inside the sarcolemma becomes more positive, leading to the contraction of muscle fibers. This process is crucial for muscle contraction and is essential for various physiological processes such as movement and muscle coordination.

Hugh Huxley is the correct answer because he was one of the scientists who developed the Sliding Filament Theory. This theory explains how muscles contract and is a fundamental concept in muscle physiology. LeBron James, Albert Einstein, and Lance Armstrong are not associated with the development of this theory.

Myofibrils are the contractile units of muscle cells, responsible for muscle contraction. They are composed of smaller structures called myofilaments, which are responsible for generating the force necessary for muscle contraction. Therefore, the correct answer is myofilaments.

A fasicle is a term used in anatomy to refer to a bundle of muscle fibers. It is another word for a bundle, making it the correct answer to the question. The other options, myofibril, calcium ion, and filament, do not have the same meaning as bundle and are therefore incorrect.

A vesicle holds neurotransmitters. Neurotransmitters are chemical messengers that transmit signals across synapses in the nervous system. They are stored in vesicles within the presynaptic neuron and released into the synaptic cleft to bind with receptors on the postsynaptic neuron, allowing for the transmission of signals between neurons.

The bottom of a motor nerve is called the axon terminal. The axon terminal is the end of the nerve fiber that forms a synapse with a target cell, such as a muscle fiber. It is responsible for transmitting signals from the nerve to the target cell, allowing for the coordination of muscle contractions and movement.