Biology Chapter 9: Smooth Muscle Structure and Contraction

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What is the primary mechanism by which smooth muscle cells contract?

By a sliding-filament mechanism (correct)

Through the use of tropomyosin

Through the release of calcium ions from the mitochondria

Via the binding of actin to troponin

What is the effect of phosphorylation of smooth muscle myosin?

It increases the rate of ATP splitting

It allows myosin to bind to actin and undergo cross-bridge cycling (correct)

It inhibits the binding of Ca2+ by calmodulin

It reduces the tension produced per unit cross-sectional area

What is the role of the sarcoplasmic reticulum in smooth muscle contraction?

It is involved in the regulation of smooth muscle relaxation

It is the primary source of ATP for smooth muscle contraction

It is responsible for the release of calcium ions into the cytosol (correct)

It is the site of smooth muscle myosin phosphorylation

What happens to the tension produced by smooth muscle when cytosolic calcium ions are increased?

It increases due to the increased binding of myosin to actin (D) Signup and view all the answers

What is the characteristic of smooth muscle myosin that differs from striated muscle myosin?

It has a lower rate of ATP splitting (B) Signup and view all the answers

What is the role of calmodulin in smooth muscle contraction?

It binds to Ca2+ and activates myosin light-chain-kinase (D) Signup and view all the answers

What type of channels are responsible for the influx of calcium ions during the rising phase of the smooth muscle action potential?

voltage-gated Ca2+ channels (B) Signup and view all the answers

What is the term for the spontaneous, periodic depolarizations of the membrane potential seen in some smooth muscle pacemaker cells?

Slow waves (C) Signup and view all the answers

What is the characteristic of smooth muscle cells in terms of their response to neurotransmitters?

They may be influenced by neurotransmitters from more than one neuron (A) Signup and view all the answers

What is the main difference between smooth muscle cells and cardiac muscle cells in terms of their structure?

Smooth muscle cells have a specialized end-plate region (A) Signup and view all the answers

What is the term for the type of smooth muscle that can generate action potentials in the absence of any external input?

Pacemaker smooth muscle (B) Signup and view all the answers

How do smooth muscle cells differ from skeletal muscle cells in terms of their response to neurotransmitters?

Smooth muscle cells respond to neurotransmitters, whereas skeletal muscle cells do not (B) Signup and view all the answers

What is a key difference between cardiac muscle excitation-contraction coupling and skeletal muscle excitation-contraction coupling?

L-type Ca2+ channels are involved in cardiac muscle but not skeletal muscle (D) Signup and view all the answers

What is a characteristic shared by cardiac muscle and smooth muscle?

Arrangement in layers around hollow cavities (B) Signup and view all the answers

What is a key similarity between cardiac muscle and skeletal muscle?

Striation pattern (C) Signup and view all the answers

What is a feature of cardiac muscle contractions that is not seen in skeletal muscle?

The strength and frequency of contraction are modulated by autonomic neurotransmitters and hormones (C) Signup and view all the answers

What can be said about the comparison of skeletal, smooth, and cardiac muscles?

Cardiac muscle shares characteristics with both skeletal and smooth muscles (C) Signup and view all the answers