Muscle Features and Skeletal Organization

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Questions and Answers

Which property of muscle cells allows them to return to their original shape after being stretched?

Extensibility

Plasticity

Elasticity (correct)

Contractility

What is the primary role of actin and myosin in muscle contraction?

To interact and shorten the sarcomere (correct)

To provide energy for the contraction

To stabilize the muscle structure

To transport calcium ions

What structure surrounds an entire skeletal muscle?

Perimysium

Myofibrils

Endomysium

Epimysium (correct)

Which protein blocks the binding sites on actin to prevent contraction when muscle is at rest?

Tropomyosin Signup and view all the answers

What initiates an action potential in the muscle cell at the neuromuscular junction?

Acetylcholine binding to receptors Signup and view all the answers

Which of the following structures is located inside muscle fibers and composed of sarcomeres?

Myofibrils Signup and view all the answers

Which characteristic of muscle cells allows them to adapt to various lengths and forces?

Plasticity Signup and view all the answers

What role does troponin play in muscle contraction?

It binds to calcium ions and moves tropomyosin. Signup and view all the answers

Which type of muscle is characterized by involuntary, rhythmic contractions and is found in the heart?

Cardiac Muscle Signup and view all the answers

What initiates the release of calcium ions from the sarcoplasmic reticulum?

Action potential stimulation Signup and view all the answers

What is the primary function of smooth muscle?

Controls the movement of substances within hollow organs Signup and view all the answers

What distinguishes asynchronous muscle found in certain insects?

Muscle fibers contract in a staggered fashion for rapid movements. Signup and view all the answers

Which role does troponin play during muscle contraction?

Exposes binding sites on actin Signup and view all the answers

Which energy system primarily provides high-intensity output for quick bursts of activity?

Immediate System Signup and view all the answers

What is the primary function of ATPase in muscle contraction?

To supply energy for the power stroke Signup and view all the answers

Skeletal muscle is known for which of the following characteristics?

Striated, long, multinucleated fibers under voluntary control Signup and view all the answers

What mechanism allows muscles to generate movement when attached to an exoskeleton?

Rigid external structure Signup and view all the answers

Which type of muscle cell is characterized by its quick contractions but rapid fatigue?

Glycolytic muscle cells Signup and view all the answers

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

It triggers the movement of tropomyosin to expose binding sites on actin. Signup and view all the answers

Which of the following is a characteristic of the glycolytic energy system?

It is anaerobic and uses glycogen to produce ATP. Signup and view all the answers

Which material in the skeleton aids in increasing the leverage of muscle contractions?

Apodemes Signup and view all the answers

What happens to calcium ions when the action potential ceases?

They are pumped back into the sarcoplasmic reticulum Signup and view all the answers

Which muscle type is specialized for rapid and sustained flight in both birds and insects?

Flight Muscles Signup and view all the answers

Which muscle cell type primarily utilizes aerobic metabolism to sustain contractions?

Slow twitch cells Signup and view all the answers

Study Notes

Muscle Features

Muscles can respond to electrical stimuli (excitability)
Muscles can shorten and create force (contractility)
Muscles can be stretched (extensibility)
Muscles return to their original shape after stretching or contracting (elasticity)
Muscles adapt to length and force changes (plasticity)

Vertebrate Skeletal Muscle Organization

Whole muscle contracts as a unit, surrounded by epimysium
Fascicle: bundle of muscle fibers (cells), surrounded by perimysium
Muscle fiber (cell): single muscle cell, surrounded by endomysium
Myofibrils: thread-like structures within muscle fibers, composed of sarcomeres
Sarcomeres: contractile units with actin (thin filaments) and myosin (thick filaments) arranged in a pattern
Actin and myosin filaments interact to shorten sarcomeres and generate force
Titin: protein stabilizing myosin filaments
Tropomyosin: protein blocking actin binding sites at rest
Troponin: protein complex moving tropomyosin, enabling contraction when calcium is present

Neuromuscular Junction Events

Action potential travels down a motor neuron to the neuromuscular junction
Acetylcholine (ACh) is released, binding to muscle cell membrane receptors
Muscle cell depolarizes, generating an action potential
Sarcoplasmic reticulum releases calcium ions (Ca2+)
Calcium binds to troponin, causing tropomyosin to move, exposing actin binding sites
Myosin heads bind to actin, creating cross-bridges
Myosin undergoes a power stroke, pulling the actin filament
ATPase activity provides the energy for the power stroke and detachment
Sarcoplasmic reticulum pumps calcium back in, causing relaxation

Skeletal Muscle Energy Systems

Immediate System: Uses ATP and creatine phosphate for quick energy bursts
Glycolytic System: Anaerobic energy production from glycogen, suitable for moderate-high intensity activities
Oxidative System: Aerobic energy production from fats, carbohydrates, and proteins, best for sustained, low intensity activities

Muscle Fiber Types

Glycolytic (Fast Twitch) Cells: Use anaerobic metabolism, contract quickly, fatigue rapidly (e.g., sprinters, predators)
Oxidative (Slow Twitch) Cells: Use aerobic metabolism, contract slowly, resist fatigue (e.g., long-distance runners, migratory birds)

Other Muscle Types

Cardiac Muscle: Striated, branched, interconnected, involuntary contractions for pumping blood (heart)
Smooth Muscle: Non-striated, spindle-shaped, involuntary contractions controlling movement in internal organs (stomach, blood vessels)

Muscle Modifications

Asynchronous Muscle: Staggered muscle fiber contraction in insects for continuous movement (e.g., wing beats)
Flight Muscles: Specialized muscles in birds and insects for sustained flight
Striated Cardiac Muscle: Coordinated muscle contractions in the heart of vertebrates

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Description

This quiz covers essential muscle features such as excitability, contractility, extensibility, elasticity, and plasticity. Additionally, it delves into vertebrate skeletal muscle organization including the structure of whole muscle, fascicles, and myofibrils. Test your understanding of how these elements work together in muscle function.