Human Anatomy and Physiology : Help with Smooth Muscle Physiology

Study concepts, example questions & explanations for Human Anatomy and Physiology

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Example Questions

Example Question #32 : Musculoskeletal Physiology

Which of the following characteristics is NOT typical of smooth muscle? 

Possible Answers:

Mononucleated

Involuntary control

No striations

Composed of sarcomeres

Correct answer:

Composed of sarcomeres

Explanation:

Of the three major muscle groups, smooth muscle is the only type not composed of sarcomeres. As a result, smooth muscle does not appear striated under a microscope. Smooth muscle is under involuntary control, innervated by the autonomic nervous system, and contains mononucleated cells.

Skeletal muscle is striated, multinucleated, and under voluntary control. Cardiac muscle is striated, mononucleated, and under involuntary control.

Example Question #2 : Help With Smooth Muscle Physiology

Three muscle cells are placed side by side.

In muscle cell 1, striations are clearly visible.

In muscle cell 2, striations are also present, with sharp discs periodically found along muscle fibers. Further examination shows gap junctions between adjacent cells.

In muscle cell 3, no striations are present.

A physician takes a sample of tissue from a patient's leg. The sample contains both sections of the extensor hallicus longus, as well as sweat glands serving the anterior tibial surface. With regard to the muscle cell types described, which two muscle types are most likely to be found in this sample?

Possible Answers:

Muscle type 1

Muscle types 2 and 2

Muscle type 2

Muscle types 1 and 3

Muscle type 3

Correct answer:

Muscle types 1 and 3

Explanation:

The physician has removed a sample of skeletal muscle (the extensor hallicus longus) as well as smooth muscle, which typically surrounds structures like sweat glands.

The smooth muscle is not under voluntary control and uses a unique mechanism of contraction, different from the striated pattern expected of sarcomeres in skeletal muscle. Instead of sarcomeres, smooth muscle contracts by using myosin light chain kinase to phosphorylate myosin, which can then interact with actin to cause a contraction. Due to the absence of striations, we can conclude the muscle type 3 corresponds to smooth muscle, and will be present in the sample.

Skeletal muscle is known for having distinct striations. Gap junctions, as seen in muscle type 2, would be characteristic only of cardiac muscle, and would not be found in skeletal muscle. We can conclude that muscle type 1 is skeletal muscle, and will be present in the sample.

Example Question #3 : Help With Smooth Muscle Physiology

Which muscle tissue type lacks striations?

Possible Answers:

Cardiac muscle

Smooth muscle

Skeletal muscle

Voluntary muscle

Multinucleated muscle

Correct answer:

Smooth muscle

Explanation:

There are three primary types of muscle tissue: smooth, skeletal, and cardiac. Skeletal muscle and cardiac muscle are striated, but smooth muscle is not.

Striations are formed by the organized units of actin and and myosin (sarcomeres) in a linear pattern. Smooth muscle still uses the mechanics of actin and myosin to generate contractile forces, but the filaments are not organized into sarcomeres. As a result, smooth muscle cells are not as linear as skeletal or cardiac muscle cells and contraction will not result in the standard "shortening" of the cell. Rather, contraction of a smooth muscle cell will cause the entirity of the cell to shrink inward. This is essential for smooth muscle functions that cause a reduction in surface area, such as the constriction of boold vessels.

Example Question #4 : Help With Smooth Muscle Physiology

What are the two types of smooth muscle cells?

Possible Answers:

Smooth and rough

Somatic and autonomic

Single-unit and mult-unit

Central and peripheral

Correct answer:

Single-unit and mult-unit

Explanation:

One of the two types of smooth muscle cells is called single-unit, where the cells are connected by gap junctions and the cells contract as a single unit. The other type of smooth muscle is called multi-unit, where the cells are not linked and each cell has to be individually stimulated. Single-unit cells are often found in the GI tract. A good example of mulit-unit cells would be in vascular smooth muscle. 

Example Question #5 : Help With Smooth Muscle Physiology

Which of the following is true regarding smooth muscle?

Possible Answers:

It has thick and thin filaments

It appears striated

It is arranged in sarcomeres

It has thin filaments only

Correct answer:

It has thick and thin filaments

Explanation:

Smooth muscle has thick and thin filaments that are not arranged in sarcomeres. Thus, smooth muscle does not appear striated, and appears homogenous. Smooth muscle comes in various types including: multi-unit smooth muscle, unitary (single unit) smooth muscle, and vascular smooth muscle.

Example Question #6 : Help With Smooth Muscle Physiology

Which subtype of smooth muscle is found in the iris and vas deferens?

Possible Answers:

Vascular smooth muscle

Striated smooth muscle

Unitary smooth muscle

Multi-unit smooth muscle

Correct answer:

Multi-unit smooth muscle

Explanation:

Smooth muscle comes in various types including: multi-unit smooth muscle, unitary (single unit) smooth muscle, and vascular smooth muscle. Multi-unit smooth muscle is present in the iris, ciliary muscle of the lens, and vas deferens. It behaves as separate motor units and has little to no electric coupling between cells. It is densely innervated and contraction is controlled by neural innervation. Unitary smooth muscle is the most common type of smooth muscle and is present in the uterus, gastrointestinal tract, ureter, and bladder. It is spontaneously active (has slow waves) and has “pacemaker” activity that is modulated by hormones and neurotransmitters. There is a high degree of electric coupling and allows for coordinated contraction. Vascular smooth muscle has properties of both multi-unit and single unit smooth muscle. Smooth muscle is not striated.

Example Question #41 : Musculoskeletal Physiology

Which subtype of smooth muscle can you find in the uterus, bladder, and gastrointestinal tract?

Possible Answers:

Unitary smooth muscle

Striated smooth muscle

Vascular smooth muscle

Multiunit smooth muscle

Correct answer:

Unitary smooth muscle

Explanation:

Smooth muscle comes in various types including: multi-unit smooth muscle, unitary (single unit) smooth muscle, and vascular smooth muscle. Unitary smooth muscle is the most common type of smooth muscle and is present in the uterus, gastrointestinal tract, ureter, and bladder. It is spontaneously active (has slow waves) and has “pacemaker” activity that is modulated by hormones and neurotransmitters. Thanks to electric coupling this muscle subtype is able to have coordinated contraction.

Multi unit smooth muscle is present in the iris, ciliary muscle of the lens, and vas deferens. It has little to no electric coupling between cells thus acts as separate motor units. Because of this it is controlled by neural innervation, and is thus densely innervated. Vascular smooth muscle shares properties of both multi-unit and single unit smooth muscle.

Example Question #42 : Musculoskeletal Physiology

What are the preganglionic and postganglionic neurotransmitters of the sympathetic nervous system, respectively?

Possible Answers:

preganglionic is acetylcholine; postganglionic is acetylcholine

Neither preganglionic or postganglionic neurons of the sympathetic nervous system use acetylcholine or norepinephrine.

preganglionic is acetylcholine; postganglionic is norepinephrine

preganglionic is norepinephrine; postganglionic is acetylcholine

preganglionic is norepinephrine; postganglionic is norepinephrine

Correct answer:

preganglionic is acetylcholine; postganglionic is norepinephrine

Explanation:

The sympathetic nervous system signals the activation of the fight-or-flight response in the body (including increased heart, blood vessel and eye pupil dilation, and increased stress hormone release). The sympathetic nervous system signal is transmitted via two chains of neurons — the preganglionic neuron and the postganglionic neuron. The preganglionic neuron uses the neurotransmitter acetylcholine. The postganglionic neuron uses the neurotransmitter norepinephrine.

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