MCAT Biology : Other Muscle Concepts

Study concepts, example questions & explanations for MCAT Biology

varsity tutors app store varsity tutors android store

Example Questions

Example Question #1 : Other Muscle Concepts

Duchenne Muscular Dystrophy is an X-linked recessive genetic disorder, resulting in the loss of the dystrophin protein. In healthy muscle, dystrophin localizes to the sarcolemma and helps anchor the muscle fiber to the basal lamina. The loss of this protein results in progressive muscle weakness, and eventually death.

In the muscle fibers, the effects of the disease can be exacerbated by auto-immune interference. Weakness of the sarcolemma leads to damage and tears in the membrane. The body’s immune system recognizes the damage and attempts to repair it. However, since the damage exists as a chronic condition, leukocytes begin to present the damaged protein fragments as antigens, stimulating a targeted attack on the damaged parts of the muscle fiber. The attack causes inflammation, fibrosis, and necrosis, further weakening the muscle.

Studies have shown that despite the severe pathology of the muscle fibers, the innervation of the muscle is unaffected.

Which of the following would be true of a patient who has Duchenne Muscular Dystrophy?

Possible Answers:

An action potential to the muscle is delayed by the basal lamina.

As the muscle weakens, the neurons must produce more epinephrine to stimulate it.

Each neuromuscular junction consists of one axon and one muscle fiber.

Vesicles at the neuromuscular junctions contain acetylcholine.

An action potential to the muscle causes Na+ to be released from the sarcoplasmic reticulum.

Correct answer:

Vesicles at the neuromuscular junctions contain acetylcholine.

Explanation:

We know that the "innervation of the muscle is unaffected" in muscular dystrophy patients, so we are looking for the answer choice that is true of healthy muscle. A neuromuscular junction consists of one neuron and all the muscle fibers it innervates (not just one). The basal lamina does not interfere with action potentials; it just helps the fibers contract together by forming physical connections between fibers. The sarcoplasmic reticulum releases Ca2+, not Na+. Finally, epinephrine is not the neurotransmitter used at neuromuscular junctions.

All neuron-muscle interactions use acetylcholine as the neruotransmitter, thus vesicles at the neuromuscular junction will contain acetylcholine.

Example Question #2 : Other Muscle Concepts

Duchenne Muscular Dystrophy is an X-linked recessive genetic disorder, resulting in the loss of the dystrophin protein. In healthy muscle, dystrophin localizes to the sarcolemma and helps anchor the muscle fiber to the basal lamina. The loss of this protein results in progressive muscle weakness, and eventually death.

In the muscle fibers, the effects of the disease can be exacerbated by auto-immune interference. Weakness of the sarcolemma leads to damage and tears in the membrane. The body’s immune system recognizes the damage and attempts to repair it. However, since the damage exists as a chronic condition, leukocytes begin to present the damaged protein fragments as antigens, stimulating a targeted attack on the damaged parts of the muscle fiber. The attack causes inflammation, fibrosis, and necrosis, further weakening the muscle.

Studies have shown that despite the severe pathology of the muscle fibers, the innervation of the muscle is unaffected.

The “basal lamina” refers to __________.

Possible Answers:

the region of the muscle closest to the tendon

the extracellular matrix around the muscle fiber

the outer covering of the muscle body

the muscle fiber cytoplasm

the point of the sarcolemma closest to a synapse

Correct answer:

the extracellular matrix around the muscle fiber

Explanation:

The muscle fiber cytoplasm is the sarcoplasm. The outer covering of the muscle body is the epimysium. The region of the muscle closest to the tendon and the region of sarcolemma near the synapse do not have technical names that you need to know for the MCAT, nor do they make sense as answer choices; we are looking for something that the sarcolemma must be anchored to. The basal lamina is the extracellular matrix surrounding the muscle fiber, made up largely of collagen, that connects each muscle fiber to its neighbors and helps them contract in unison.

Example Question #272 : Systems Biology And Tissue Types

Which of the following muscles is an antagonist for the biceps brachii?

Possible Answers:

Biceps femoris

Brachioradialis

Triceps brachii

Brachialis

Correct answer:

Triceps brachii

Explanation:

An antagonist is defined as the muscle that strecthes when another muscle (the agonist) is contracting. When the antagonist contracts, it will stretch the agonist and move the bone in the opposite direction.

The biceps brachii is responsible for flexion of the forearm, while the triceps brachii is responsible for the extension of the forearm. As a result, we say that the triceps brachii is the antagonist of the biceps brachii.

Example Question #81 : Musculoskeletal System And Muscle Tissue

The masseter is the most prominent muscle involved in eating food. It is responsible for elevating the jaw during mastication. The temporalis is a muscle located on the outside of the temporal bone. It also elevates the mandible during the chewing of food.

Based on this information, how would you describe the temporalis in relation to the masseter?

Possible Answers:

The temporalis is the antagonist of the masseter.

The temporalis is the synergist of the masseter.

The temporalis is the insertion of the masseter.

The temporalis is the origin of the masseter.

Correct answer:

The temporalis is the synergist of the masseter.

Explanation:

Synergistic muscles assist agonists by properly positioning the insertion bone or stabilizing the origin bone. This cooperation by multiple muscles allows for better movement and posture. Since the temporalis assists in raising the jaw with the masseter, we say that the temporalis is the synergist of the masseter.

Example Question #82 : Muscles And Myocytes

During muscle contraction, which parts of a sarcomere change in length?

Possible Answers:

The H zone and I band

The H zone and actin

The H zone and myosin

The A band and H zone

The I band and A band

Correct answer:

The H zone and I band

Explanation:

During muscle contraction, the H zone and I band contract, decreasing in length. The A band never changes in length. Also, while actin and myosin myofilaments slide over each other, their length does not change either.

Example Question #6 : Other Muscle Concepts

Which type of muscle has both striations and multiple nuclei?

Possible Answers:

Both skeletal muscle and smooth muscle

Both skeletal muscle and cardiac muscle

Skeletal muscle

Smooth muscle

Cardiac muscle

Correct answer:

Skeletal muscle

Explanation:

There are three primary types of muscle tissue: skeletal, smooth, and cardiac.

Skeletal muscle and cardiac muscle are highly organized, with their contractile filaments arranged into sarcomeres. This organization results in a "striped" look on the cells, known as striations. Smooth muscle contains the same contractile filaments, but lacks the sort of highly organized structure found in the other two muscle types. As a result, smooth muscle is not striated.

Smooth muscle and cardiac muscle are generally mononucleate, meaning that each cell has only on nucleus. In contrast, skeletal muscle cells contain multiple nuclei.

The correct answer is that skeletal muscle is striated and contains multiple nuclei per cell.

Example Question #82 : Musculoskeletal System And Muscle Tissue

Which of the following answer options is not a function of the sarcolemma?

Possible Answers:

Creates T-tubules from invaginations along the membrane

Allows attachment sites for communication hormones

Controls the iron levels of cardiac tissue

Creates an ion potential across the muscle surface

Controls the tonic state of myocytes

Correct answer:

Controls the iron levels of cardiac tissue

Explanation:

The sarcolemma is the specialized cell membrane of a myocyte, or muscle cell. It performs all of the functions of a non-specialized plasmolemma, and forms T-tubules, which are important for muscle contraction.

Example Question #83 : Musculoskeletal System And Muscle Tissue

Which is not a function of muscle tissue?

Possible Answers:

Peristalsis

Motion

Thermoregulation

Locomotion

Leverage

Correct answer:

Leverage

Explanation:

The primary functions of muscle tissue are motion and locomotion (movement in relation to the body, and movement of the entire body). Muscle is also responsible for the shiver response, used in thermoregulation. Finally, smooth muscles move substances through the body in the process known as peristalsis.

Leverage is a function primarily accomplished by bone.

Example Question #9 : Other Muscle Concepts

What type of muscle cell is quadrangular, and features intercalated disks and multiple nuclei?

Possible Answers:

Smooth muscle

Skeletal muscle

Cardiac muscle

None of the other answers

Thick muscle

Correct answer:

None of the other answers

Explanation:

None of the answer options satisfy all of the criteria given in the question. Cardiac muscle cells have intercalated discs, but are mononucleate.

Learning Tools by Varsity Tutors

Incompatible Browser

Please upgrade or download one of the following browsers to use Instant Tutoring: