MCAT Biology : Types of Muscle Cells
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Example Question #21 : Types Of Muscle Cells
Choose the answer that best describes the characteristics of the extraocular muscles.
Fatigable with large motor units
Non-fatigable with large motor units
Fatigable with small motor units
Non-fatigable with small motor units
Non-fatigable with small motor units
The extraocular muscles have small motor units to allow for very precise movements. These muscles are also non-fatigable because the muscles do not become weak after continual use throughout the day.
Large motor units would result in less precise control, affecting the ability of the eye to focus on a given target. Fatigable motor units would result in an inablility to keep the eye open and directed after sustained use.
Example Question #22 : Types Of Muscle Cells
Peristalsis takes place in the lower two-thirds of the esophagus.
What type of muscle is used in the process of peristalsis?
Involunary cardiac muscle
Involuntary smooth muscle
Voluntary skeletal muscle
Involuntary skeletal muscle
Involuntary smooth muscle
Involuntary smooth muscle is used in many parts of the digestive tract. Smooth muscle moves food through the digestive tract, while also methodically spreading out the food's surface area, maximizing exposure to the nutrient-absorbing layers of the intestines.
Example Question #21 : Types Of Muscle Cells
What is the difference between the muscles in a distance runner's legs compared to the muscles in a weight lifter's legs?
The weight lifter will have more type I muscle fibers than the runner
The runner will have more type IIB muscle fibers than the weight lifter
The weight lifter will have more type IIA muscle fibers than the runner
The weight lifter will have many more muscle cells than the runner
The weight lifter will have more type IIA muscle fibers than the runner
There are three types of muscle fibers: type I (slow twitch muscle fibers), type IIA, and type IIB (both fast twitch muscle fibers). Type I muscle fibers are very slow to fatigue, so we would expect to find them in athletes that specialize in endurance. Conversely, type IIA and B fibers are used for short lived, anaerobic activities. These fibers are typically seen in weight lifters. As a result, we would expect the weight lifter to have more type IIA and B muscle fibers than the runner.
Example Question #24 : Types Of Muscle Cells
Which of the following types of muscle can be electrically stimulated without any input from the human brain?
Skeletal muscle
Cardiac muscle
All muscle can act autonomously if the conditions are right
All muscle requires input from the brain
Smooth muscle
Cardiac muscle
Skeletal muscle and smooth muscle both require input from the brain in order to contract. Although smooth muscle is not under voluntary control, it is still controlled by the autonomic nervous system, which gets signals from the brain. Cardiac muscle has its own pacemaker cells and thus, even without any input from the brain, can keep the heart continuously beating.
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