Muscle Physiology Quiz

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What role does calcium play in the contraction-relaxation cycle of skeletal muscles?

It is responsible for pumping sodium ions out of the muscle cell.

It activates voltage-gated Na+ channels to depolarize the muscle fiber.

It binds to troponin to facilitate muscle contraction. (correct)

It initiates the release of acetylcholine at the neuromuscular junction.

Which component is responsible for releasing calcium ions from the sarcoplasmic reticulum during excitation-contraction coupling?

Acetylcholine receptor

Dihydropyridine receptor (DHPR)

Sodium-potassium pump

Ryanodine receptor (RyR) (correct)

What is the primary function of the neuromuscular junction?

To facilitate the exchange of nutrients between muscle fibers.

To connect motor neurons to sensory neurons.

To store calcium ions for muscle contraction.

To transmit signals from motor neurons to muscle fibers. (correct)

How are motor units categorized?

By their contractile and metabolic properties. Signup and view all the answers

What initiates the process of muscle contraction at the neuromuscular junction?

The binding of acetylcholine to its receptor. Signup and view all the answers

What primary effect does malignant hyperthermia have on the RYR channel?

It causes the RYR to remain open continuously. Signup and view all the answers

What is the main consequence of the elevated calcium levels in the sarcoplasm during malignant hyperthermia?

Sustained muscle cell contraction. Signup and view all the answers

Which of the following is a clinical manifestation of malignant hyperthermia?

Respiratory acidosis. Signup and view all the answers

What triggers the episode of malignant hyperthermia?

Anesthetic agents. Signup and view all the answers

What role does dantrolene sodium play in treating malignant hyperthermia?

It closes the RYR1 channel, reducing calcium flow. Signup and view all the answers

What is the consequence of ATP depletion during a malignant hyperthermia episode?

Widespread muscle fiber hypoxia. Signup and view all the answers

What is the role of the dihydropyridine receptor (DHPR) in normal muscle function?

It senses muscle cell depolarization. Signup and view all the answers

What is the primary function of the muscle spindle in skeletal muscle?

To monitor changes in muscle length Signup and view all the answers

What type of reflex is classified as an autonomic (visceral) reflex?

Reflexes important for homeostasis Signup and view all the answers

Which of the following appropriately describes the location and function of the Golgi tendon organ?

Located between the tendon and extrafusal fibers, monitoring tension Signup and view all the answers

What type of neurons innervate extrafusal muscle fibers?

Alpha motor neurons Signup and view all the answers

How do muscle spindles respond when a muscle is relaxed?

They continuously fire Signup and view all the answers

What is a key characteristic of sensory receptors (afferent neurons) related to skeletal muscle?

They relay information about muscle length and tension Signup and view all the answers

What is the role of gamma motor neurons in skeletal muscles?

To stabilize muscle spindles Signup and view all the answers

Which of the following statements about the structural organization of the muscle spindle is correct?

Extrafusal fibers surround the intrafusal muscle fibers Signup and view all the answers

What is the primary function of calcium binding proteins in muscle cells?

To restore resting intracellular Ca++ levels Signup and view all the answers

What occurs during the simultaneous excitation of agonist muscle and inhibition of antagonistic muscles?

Coordinated muscle action is facilitated Signup and view all the answers

What occurs during a state of rigor in muscle cells?

Actin and myosin are bound without ATP Signup and view all the answers

What is the primary energy source for myosin to detach from actin during muscle contraction?

ATP Signup and view all the answers

What happens during summation and tetanus in muscle contraction?

Multiple contractions occur before the muscle has relaxed Signup and view all the answers

How is ATP resynthesized for muscle contraction during prolonged activity?

By utilizing both aerobic and anaerobic means Signup and view all the answers

What does the term 'efferent' refer to in the context of muscle nerve signaling?

Signals that travel from the CNS to an effecter Signup and view all the answers

What is the result of the Na-K pump's activity in muscle cells?

Restoration of resting membrane potential Signup and view all the answers

During maximal contraction, how long can the cellular store of ATP sustain activity in skeletal muscle?

A few seconds Signup and view all the answers

What is primarily responsible for the power stroke that drives muscle contraction?

Hydrolysis of ATP by myosin ATPase Signup and view all the answers

Study Notes

Normal Skeletal Muscle Physiology: Contraction-Relaxation Steps

Skeletal muscle contraction is a complex process involving multiple steps.
Contraction and relaxation rely on the interaction of actin and myosin filaments, regulated by calcium.

Muscle Structure

Muscle tissue is organized into hierarchical structures:
- Epimysium surrounds the entire muscle.
- Perimysium surrounds fascicles (bundles of muscle fibers).
- Endomysium surrounds individual muscle fibers.
Muscle fibers contain myofibrils, composed of repeating units called sarcomeres.
Sarcomeres are the functional units of muscle contraction.
Myofibrils are composed of actin and myosin filaments.
Sarcolemma is the muscle cell membrane.
The sarcoplasmic reticulum (SR) stores and releases calcium ions.
T-tubules are invaginations of the sarcolemma that transmit action potentials into the muscle fiber.
A triad is a combination of a T-tubule and two terminal cisternae of the SR.

Proteins of Myofibrils

Contractile proteins: Myosin (thick filament) and Actin (thin filament)
Regulatory proteins: Tropomyosin (covers actin active site) and Troponin complex (Ca2+ binding)
Structural proteins: Titin and Nebulin

Myotonia Congenita

Inherited disorder characterized by muscle membrane hyperexcitability
Muscle stiffness
Genetic defect in chloride channel CLCN1

Duchenne Muscular Dystrophy

Progressive muscle weakness caused by dystrophin deficiency.
Results in early death

Other Structural Proteins

Dystrophin : Important for structural integrity of muscle cells.
Dystroglycan complex : Important for anchoring the muscle cell to its surroundings.

Excitation-Contraction Coupling

Neuromuscular Junction: ACh release from motor neuron triggers muscle fiber excitation.
Depolarization travels along sarcolemma and into T-tubules.
Release of Ca2+ from the sarcoplasmic reticulum.
Sliding Filament Theory: Increases overlap between actin and myosin, leading to muscle shortening.
Contraction/Relaxation Cycle: The cycle of events involved in the sliding-filament theory.

Protein Interactions During Muscle Contraction

ATP binding to myosin causes myosin head to detach from actin.
ATP hydrolysis "cocks" the myosin head.
Myosin head binds to a new position on actin filaments.
Release of inorganic phosphate causes power stroke.
Release of ADP causes myosin head to return to resting conformation.

Rigor Mortis

Muscle stiffness after death due to lack of ATP.
Myosin heads remain bound to actin, preventing muscle relaxation.

Energy Requirements for Skeletal Muscle Contraction

ATP hydrolysis provides energy for the power stroke.
Ca-ATPase pumps and Na-K pumps are essential for relaxation and maintaining resting membrane potential.

Twitch and Tetanus

Twitch: A single contraction-relaxation cycle in a muscle fiber.
Tetanus: Sustained muscle contraction due to rapid stimulation, characterized by incomplete and complete tetanus.

Motor Units

A motor unit consists of a motor neuron and all the muscle fibers it innervates.
Motor units are categorized by their properties into fiber types.

Somatic Reflexes

Reflexes based on somatic efferent pathways.
Reflexes are categorized by the effector, integrating region, time of development, and number of neurons involved.
Classified as monosynaptic (two neurons involved) and polysynaptic (three or more neurons involved).

Muscle Spindles

Sensory receptors that monitor muscle length changes.
Consist of intrafusal fibers located within extrafusal fibers.
Provide feedback to the CNS regarding muscle length.
Primary afferent endings : Rapidly adapt to changes in muscle length.
Secondary afferent endings : Slowly adapt to changes in muscle length.

Golgi Tendon Organs (GTOs)

Located in the tendons of muscles, monitoring tendon tension.
Consist of specialized sensory endings wrapped around collagen fibers within tendons and responding to muscle tensions.
Provides information regarding tension produced by muscles, providing feedback to the CNS about tension in the muscle-tendon complex.

Alpha-Gamma Coactivation

Simultaneous activation of alpha and gamma motor neurons.
Ensures that spindle receptors continue to provide feedback to CNS.
Maintains optimal sensitivity of the muscle spindle during muscle shortening.

Flexor Reflex

A reflex movement of a limb away from a painful stimulus.

Crossed Extensor Reflex

Reciprocal inhibition reflex, supporting body weight as weight shifts to the opposite limb.
Compensatory action to maintain balance.

Review of Normal Physiology Somatic Reflexes and Sensory Receptors

Includes a comprehensive overview of the somatic reflexes and sensory receptors.
Muscle spindles and Golgi tendon organs are key sensory components to report muscle tension.

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Description

Test your knowledge on the role of calcium in muscle contraction and relaxation cycles. This quiz covers key concepts like excitation-contraction coupling, the function of the neuromuscular junction, and categorization of motor units. Perfect for students of physiology or anatomy.