Differences Between Smooth and Skeletal Muscle Contraction

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Questions and Answers

Which type of muscle contraction is regulated by thick filaments?

Visceral muscle contraction

Striated muscle contraction

Smooth muscle contraction (correct)

Skeletal muscle contraction

What type of smooth muscle is characterized by having extensive intercellular electrical communication?

Multi-unit smooth muscle

Tonic smooth muscle

Syncytial smooth muscle (correct)

Single-unit smooth muscle

In smooth muscles, what controls the contractile process by causing changes in intracellular calcium concentration?

Production of second messengers (correct)

Activation of neuromuscular junctions

Action potentials

Opening of membrane channels

Which type of smooth muscle operates with each fiber being innervated by a single nerve ending, similar to skeletal muscle fibers?

Multi-unit smooth muscle Signup and view all the answers

What is the normal range of intracellular potential in smooth muscle at rest?

$-50$ to $-60$ millivolts Signup and view all the answers

What is the key characteristic of multi-unit smooth muscle fibers?

Independent contraction of each fiber Signup and view all the answers

In which type of smooth muscle do action potentials occur similarly to skeletal muscle?

Unitary smooth muscle Signup and view all the answers

Which component is absent in multi-unit smooth muscle fibers compared to skeletal muscle fibers?

Neuromuscular junction Signup and view all the answers

Which type of smooth muscle contraction responds to electrical and hormonal stimulation?

Single/multi-unit muscle contraction Signup and view all the answers

What type of junctions join the cell membranes of syncytial smooth muscle fibers?

Gap junctions Signup and view all the answers

What is the main mechanism by which chemical factors control the function of smooth muscle cells?

Production of second messengers Signup and view all the answers

Which characteristic distinguishes tonic smooth muscle from other types of smooth muscle?

Each fiber operates independently Signup and view all the answers

What is a major difference between the physical organization of smooth muscle and skeletal muscle?

Absence of sarcoplasmic reticulum in smooth muscle Signup and view all the answers

How is smooth muscle contraction dependent on calcium ions?

Extracellular calcium ion concentration Signup and view all the answers

What type of pump is required for smooth muscle relaxation?

Calcium pump Signup and view all the answers

What is the duration of contraction like in smooth muscle compared to skeletal muscle?

Shorter in smooth muscle Signup and view all the answers

What controls the contractile process in smooth muscle?

Calcium ions Signup and view all the answers

Which structure is not well-developed in smooth muscle compared to skeletal muscle?

T-tubules Signup and view all the answers

What is the primary step in the regulation of smooth muscle contraction?

Phosphorylation of the regulatory light chains of the myosin molecule Signup and view all the answers

Which factor causes smooth muscle relaxation and vasodilation due to lack of oxygen in local tissues?

Adenosine buildup Signup and view all the answers

Which hormone does not affect smooth muscle contraction according to the text?

Aldosterone Signup and view all the answers

What is the rhythmic potential change called that results from the periodic variation of the resting potential in smooth muscles?

Slow wave Signup and view all the answers

Which ion plays a role in smooth muscle relaxation based on the text?

Increased potassium ions Signup and view all the answers

What must occur for myosin to interact with actin during smooth muscle contraction?

Phosphorylation of myosin light chains Signup and view all the answers

What is the structural difference in actin and myosin filament arrangement between smooth muscle and skeletal muscle?

In smooth muscle, actin filaments are attached to dense bodies, while in skeletal muscle, they are arranged in a striated pattern with myosin filaments. Signup and view all the answers

How are the dense bodies in smooth muscle related to Z lines in skeletal muscle?

Dense bodies in smooth muscle are the functional equivalents of Z lines in skeletal muscle. Signup and view all the answers

What type of junctions provide low-resistance pathways for action potentials to propagate between smooth muscle cells?

Gap junctions Signup and view all the answers

Which molecule activates the contractile process in smooth muscle cells?

Calcium ions Signup and view all the answers

How is the control of contraction different between smooth muscle and skeletal muscle?

Smooth muscle lacks the troponin complex that controls contraction in skeletal muscle. Signup and view all the answers

What provides the energy for contraction in smooth muscle cells?

Adenosine triphosphate (ATP) Signup and view all the answers

Study Notes

Smooth muscle fibers can be arranged in sheets/bundles, with cell membranes adhering to each other to transmit force.
Unitary smooth muscle has extensive intercellular electrical communication and is also known as syncytial smooth muscle.
Multi-unit smooth muscle is composed of separate fibers that operate independently, each innervated by a single nerve ending.
Multi-unit smooth muscle lacks T-tubules, troponin complex, and neuromuscular junctions found in skeletal muscle.
Smooth muscle contraction is activated by calcium ions, with differences in excitation-contraction coupling compared to skeletal muscle.
Smooth muscle contraction is dependent on extracellular calcium ion concentration, requiring a calcium pump for relaxation.
Factors like lack of oxygen, excess carbon dioxide, and various hormones can affect smooth muscle contraction.

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Description

Explore the major differences between the physical organization of smooth muscle and skeletal muscle, as well as variations in excitation-contraction coupling, calcium ion control, duration of contraction, and energy requirements in the contraction process.