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Ch. 10 Muscle Tissue and Physiology
Amerman - Human Anatomy & Physiology 2nd Edition
Amerman2nd EditionHuman Anatomy & PhysiologyISBN: 9780136873822Non è quello che usi tu?Cambia libro di testo
Tutti i libri di testoAmerman 2nd EditionCh. 10 Muscle Tissue and PhysiologyProblema 20
Capitolo 10, Problema 20

Which of the following best describes single-unit smooth muscle tissue?
a. The fibers function individually.
b. It is found in organs that require precise control of contraction.
c. It contains gap junctions that couple the fibers electrically.
d. The amount of tension produced varies with the number of muscle cells recruited.

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1
Understand the characteristics of single-unit smooth muscle tissue: Single-unit smooth muscle is a type of smooth muscle where the fibers contract as a single unit due to electrical coupling through gap junctions. This is different from multi-unit smooth muscle, where fibers function independently.
Recall the role of gap junctions: Gap junctions are specialized intercellular connections that allow ions and electrical signals to pass directly between adjacent cells. This electrical coupling enables synchronized contraction of the muscle fibers in single-unit smooth muscle.
Identify where single-unit smooth muscle is typically found: Single-unit smooth muscle is commonly found in the walls of hollow organs such as the intestines, stomach, and blood vessels, where coordinated contraction is necessary for functions like peristalsis or blood flow regulation.
Eliminate incorrect options: a) 'The fibers function individually' describes multi-unit smooth muscle, not single-unit smooth muscle. b) 'It is found in organs that require precise control of contraction' is more characteristic of multi-unit smooth muscle. d) 'The amount of tension produced varies with the number of muscle cells recruited' applies to skeletal muscle, not single-unit smooth muscle.
Select the correct answer: Based on the characteristics of single-unit smooth muscle, the correct description is c) 'It contains gap junctions that couple the fibers electrically.'

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Single-Unit Smooth Muscle Tissue

Single-unit smooth muscle tissue, also known as visceral smooth muscle, is characterized by its fibers functioning as a single unit due to the presence of gap junctions. These junctions allow for electrical coupling between adjacent muscle cells, enabling coordinated contractions across the tissue. This type of muscle is typically found in hollow organs, such as the intestines and blood vessels, where rhythmic and involuntary contractions are necessary.
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Smooth Muscle Tissue

Gap Junctions

Gap junctions are specialized intercellular connections that facilitate communication between adjacent cells. In single-unit smooth muscle, these junctions allow ions and small molecules to pass directly from one cell to another, promoting synchronized contraction. This electrical coupling is crucial for the coordinated activity of smooth muscle, enabling it to function effectively as a unit rather than as isolated fibers.
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Cell Junctions

Coordinated Contraction

Coordinated contraction in single-unit smooth muscle refers to the simultaneous contraction of muscle fibers, which is essential for the proper functioning of various organs. This coordination is achieved through the electrical coupling provided by gap junctions, allowing the muscle to respond as a whole to stimuli. This is particularly important in organs that require rhythmic contractions, such as the digestive tract, to facilitate processes like peristalsis.
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Overview of Muscle Contraction
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Which of the following factors is/are responsible for muscular fatigue?

a. Accumulation of chemicals, including calcium and phosphate ions & increased blood flow to the muscle

b. Decreased availability of oxygen

c. Psychological and environmental factors

d. Depletion of key metabolic fuels, such as creatine phosphate

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Mark the following statements as true for smooth muscle tissue, cardiac muscle tissue, and/or skeletal muscle tissue.          

a. _________ Actin attaches to dense bodies.          

b. _________ Cells are joined by intercalated discs.          

c. _________ The thick and thin filaments are arranged into sarcomeres.          

d. _________ The thick filaments contain myosin heads along their entire length.          

e. _________ The cells depolarize and contract as a unit.          

f. _________ Ca2+ binding to troponin is the initiating event of contraction.          

g. _________ Ca2+ binding to calmodulin is the initiating event of contraction.          

h. _________ The sarcolemma has a distinct motor end plate.

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List some of the functions of smooth muscle tissue.

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What is thought to cause excess postexercise oxygen consumption?

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