GRE Subject Test: Biology : Understanding Musculoskeletal Structures

Study concepts, example questions & explanations for GRE Subject Test: Biology

varsity tutors app store varsity tutors android store

Example Questions

Example Question #1 : Understanding Musculoskeletal Structures

Which structure releases calcium ions prior to muscle contraction?

Possible Answers:

T-tubule

Sarcolemma

Sarcoplasmic reticulum

Myosin 

Correct answer:

Sarcoplasmic reticulum

Explanation:

Before muscle contraction can take place, tropomyosin must be removed from the active site on actin, so that myosin heads can attach. Calcium ions are responsible for attaching to troponin, which will then pull tropomyosin away from the active sites. These calcium ions are stored in the sarcoplasmic reticulum until an action potential stimulates their release.

T-tubules serve to conduct the action potential to the interior of the muscle fiber, allowing for coordinated contraction of sarcomeres throughout the fiber. The sarcolemma is simply the cell membrane of the muscle fiber. Myosin is the filament responsible for binding actin, but does not directly interact with calcium.

Example Question #2 : Understanding Musculoskeletal Structures

Which bone cell is responsible for resorbing bone matrix?

Possible Answers:

Osteocyte

Osteoclast

Osteoblast

Osteogenic cell

Correct answer:

Osteoclast

Explanation:

Bone tissue is formed by four bone cell types. Osteogenic cells are the progenitor stem cells that differentiate into osteoblasts. Osteoblasts are responsible for creating bone matrix by depositing hydroxyapatite crystal. They will eventually become encapsulated by the bone matrix, and differentiate into osteocytes. Osteocytes are primarily involved in communication and nutrient transfer within the bond matrix. Osteoclasts perform the opposite action osteoblasts and resorb the bone matrix. This process increases mineral concentrations in the blood.

Example Question #3 : Understanding Musculoskeletal Structures

Which of the following is true concerning all muscle types?

Possible Answers:

All muscle fibers are composed of sarcomeres

All muscle types are uninucleated

Mitosis does not take place in muscle cells

All muscle appears striated under a microscope

Correct answer:

Mitosis does not take place in muscle cells

Explanation:

Muscle cells are considered quiescent, and are incapable of mitosis. Instead, muscle mass will increase by hypertrophy (cell growth without division). In the event of damage, muscle satellite cells will differentiate into new myocytes, but the mature myocytes will not divide.

Only skeletal muscle and cardiac muscle contain organized sarcomeres, leading to their striated appearance. Smooth muscle does not contain sarcomeres and does not appear striated. Instead, actin and myosin align in multiple directions, allowing non-linear contraction in smooth muscle. Smooth muscle and cardiac muscle are generally uninucleated, but skeletal muscle cells contain numerous nuclei.

Example Question #4 : Understanding Musculoskeletal Structures

Which of the following muscle types can be consciously controlled?

Possible Answers:

Skeletal muscle

Cardiac muscle

Smooth muscle

All of these

Correct answer:

Skeletal muscle

Explanation:

There are three main divisions of muscle tissue. Of these three, only skeletal muscle can be consciously controlled. Smooth muscle and cardiac muscle are under the control of the autonomic nervous system.

Skeletal muscle is used in locomotion and conscious actions, such as eye movements or forced respiration. Smooth muscle is used in vasodilation and vasoconstriction, and surrounds most organs in the body. Smooth muscle is responsible for unconscious diaphragm contractions, stomach contractions, and other visceral activity. Cardiac muscle is only found in the heart and is capable of independent, spontaneous contraction without nervous intervention.

Example Question #5 : Understanding Musculoskeletal Structures

What is a hydrostatic skeleton?

Possible Answers:

A system of fluid-filled, rigid vessels which use water pressure to support organisms living in moist environments

A specialized exoskeleton in marine organisms which is stiff yet flexible enough to allow an organism to survive underwater at high pressures

An organ such as the tongue in mammals, composed mainly of muscle but relying on the fact that water is nearly incompressible for motion

A support system consisting of porous bones with the cavities filled with fluid in order to increase density

A flexible support structure consisting of a coelom surrounded by muscles

Correct answer:

A flexible support structure consisting of a coelom surrounded by muscles

Explanation:

The hydrostatic skeleton is a fluid-filled coelom surrounded by but not made chiefly of muscles in soft bodied, aquatic organisms such as echinoderms.

Learning Tools by Varsity Tutors

Incompatible Browser

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