Muscle Function Overview
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Questions and Answers

What triggers depolarization and repolarization in action potential generation?

A stimulus reaching threshold

What connects a motor neuron to a muscle fiber?

Neuromuscular junction (NMJ)

Which neurotransmitter is released into the synaptic cleft?

  • Acetylcholine (correct)
  • Norepinephrine
  • Dopamine
  • Serotonin

The smooth muscles control movement within ______.

<p>organs and blood vessels</p> Signup and view all the answers

Skeletal muscles are under involuntary control.

<p>False (B)</p> Signup and view all the answers

What binds to troponin on actin during excitation-contraction coupling?

<p>Ca2+ (Calcium ions)</p> Signup and view all the answers

What is the appearance of cardiac muscle?

<p>Striated with intercalated discs (C)</p> Signup and view all the answers

What is required for cross-bridge formation and movement?

<p>ATP</p> Signup and view all the answers

The complex that covers myosin binding sites on actin returns to its original position during muscle ______.

<p>relaxation</p> Signup and view all the answers

Study Notes

Muscle Function

  • Skeletal Muscle: Attached to bones, voluntary control, responsible for movement, posture, respiration
  • Smooth Muscle: Found in the walls of hollow organs and blood vessels, involuntary control, responsible for movement of substances and blood flow regulation
  • Cardiac Muscle: Located in the heart, involuntary control, responsible for pumping blood

Muscle System Functions

  • Body Movement: Voluntary movements like walking and running
  • Posture Maintenance: Maintains muscle tone for stability
  • Respiration: Muscles in the thorax assist with breathing
  • Heat Production: Muscle contractions generate heat for temperature regulation
  • Communication: Facial expressions and speech
  • Organ Constriction: Smooth muscles control movement within organs and blood vessels
  • Heartbeat Regulation: Cardiac muscle drives heartbeats

Neuromuscular Junction (NMJ)

  • Connects a motor neuron to a muscle fiber
  • Composed of the presynaptic terminal, synaptic cleft, and motor end-plate
  • Neurotransmitter Release: Acetylcholine (ACh) is released into the synaptic cleft, binding to receptors on the muscle fiber, causing depolarization
  • Acetylcholinesterase: Breaks down ACh to prevent continuous stimulation

Excitation-Contraction Coupling

  • Action Potential Propagation: Action potentials travel along the sarcolemma and T tubules, triggering Ca2+ release from the sarcoplasmic reticulum (SR)
  • Calcium Binding: Ca2+ binds to troponin on actin, moving the troponin-tropomyosin complex to expose myosin binding sites

Cross-Bridge Cycle

  • Formation and Movement: Myosin heads attach to actin, perform a power stroke, pulling filaments towards the sarcomere center, and release. ATP is needed for each cycle to detach the myosin head and reset it
  • Energy Use: ATP is essential for cross-bridge formation and movement. It also allows the myosin head to return to its original position

Muscle Relaxation

  • Calcium Reuptake: Ca2+ is actively transported back into the SR, decreasing its concentration in the sarcoplasm
  • Troponin-Tropomyosin Complex: Returns to its original position, covering the myosin binding sites on actin, resulting in muscle relaxation due to decreased cross-bridge cycling

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Description

This quiz covers the three types of muscle tissue: skeletal, smooth, and cardiac. It explains their functions related to movement, posture, respiration, and other vital processes. Test your understanding of the neuromuscular junction and how muscles interact with the nervous system.

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