Physiology of Nerve Impulse Transmission

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Questions and Answers

What is the primary cause of muscle fatigue?

Lack of hydration

Oxygen debt (correct)

High muscle temperature

Excessive glucose

Which process is necessary to remove lactic acid buildup in fatigued muscles?

Enhanced ATP production

Increased blood flow

Protein synthesis

Oxygen repayment (correct)

During muscle contraction, what is the initial source of energy used by muscles?

Fatty acids

Stored ATP (correct)

Creatine phosphate

Glucose

What occurs during isotonic contractions?

Myofilaments slide past each other and the muscle shortens Signup and view all the answers

What happens to creatine phosphate (CP) after ATP is depleted in muscle cells?

It transfers energy to ADP to regenerate ATP. Signup and view all the answers

How long do the supplies of creatine phosphate typically last during intense muscle activity?

20 seconds Signup and view all the answers

What describes muscle tone?

Continuous contractions of some muscle fibers Signup and view all the answers

What is the primary byproduct of anaerobic glycolysis when glucose is broken down?

Lactic acid Signup and view all the answers

What are the two attachment points of a muscle?

Insertion and origin Signup and view all the answers

Which of the following accurately describes anaerobic glycolysis?

It produces lactic acid and is faster than aerobic respiration. Signup and view all the answers

Which effect is NOT typically a result of increased muscle use?

Increase in muscle flexibility Signup and view all the answers

Which type of contraction leads to muscle shortening?

Isotonic contraction Signup and view all the answers

Which process requires continuous oxygen for energy production in muscles?

Aerobic respiration Signup and view all the answers

What is the main drawback of anaerobic glycolysis in terms of energy production?

It leads to muscle fatigue due to lactic acid. Signup and view all the answers

How does increased muscle efficiency affect muscle performance?

Improves ability to sustain activity Signup and view all the answers

What is produced as a result of aerobic respiration?

Carbon dioxide and water Signup and view all the answers

What neurotransmitter is released by nerves to stimulate skeletal muscle contraction?

Acetylcholine Signup and view all the answers

What initial change occurs in the sarcolemma after the neurotransmitter attaches to its receptors?

Increased permeability to sodium Signup and view all the answers

What is the result of sodium rushing into the cell during muscle contraction?

Generation of an action potential Signup and view all the answers

What theory describes the process of muscle contraction involving myosin and actin?

Sliding Filament Theory Signup and view all the answers

What characteristic describes muscle fiber contraction within a skeletal muscle?

Contraction is an all-or-none response Signup and view all the answers

What influences the muscle force generated in response to stimuli?

Number of fibers stimulated Signup and view all the answers

What happens during tetanus in muscle contraction?

Constant contraction occurs with no relaxation Signup and view all the answers

What can limit the duration of muscle contraction?

Availability of oxygen and energy Signup and view all the answers

Which characteristic is unique to smooth muscle compared to other muscle types?

Spindle-shaped cells Signup and view all the answers

What is the primary function of muscles?

Generate warmth Signup and view all the answers

Where are cardiac muscle cells primarily found?

In the heart Signup and view all the answers

What separates cardiac muscle cells at intercalated discs?

Gap junctions Signup and view all the answers

What characteristic of skeletal muscle allows it to appear striated?

Arrangement of myofibrils Signup and view all the answers

What is the primary contractile unit of a muscle fiber?

Sarcomere Signup and view all the answers

Which of the following is NOT a characteristic of smooth muscle?

Striated appearance Signup and view all the answers

How are skeletal muscle cells different from cardiac muscle cells?

Skeletal muscle cells are multinucleate and voluntary Signup and view all the answers

What motion decreases the angle of a joint and brings two bones closer together?

Flexion Signup and view all the answers

Which term describes the movement of a bone around its longitudinal axis, such as shaking the head 'no'?

Rotation Signup and view all the answers

What is the role of a synergist muscle in body movements?

To aid a prime mover Signup and view all the answers

Which of the following is an example of abduction?

Lifting the leg away from the midline Signup and view all the answers

What term describes the shape of a triangular muscle, as exemplified by the deltoid muscle?

Deltoid Signup and view all the answers

What is the function of an antagonist muscle?

To oppose or reverse a prime mover's action Signup and view all the answers

In naming skeletal muscles, what does the term 'maximus' indicate?

Largest muscle Signup and view all the answers

Which of the following refers to the cone-shaped movement around a joint?

Circumduction Signup and view all the answers

Study Notes

Transmission of Nerve Impulse to Muscle

Neurotransmitters are chemicals released upon nerve impulse, specifically acetylcholine for skeletal muscles.
Acetylcholine binds to receptors on the sarcolemma, making it permeable to sodium ions (Na+).
The influx of sodium generates an action potential which initiates muscle contraction, an irreversible process once started.

The Sliding Filament Theory of Muscle Contraction

Activation from the nerve causes myosin heads (crossbridges) to attach to thin filament binding sites.
Myosin heads continue to bind to consecutive sites along the thin filament, resulting in the sliding of myosin along actin.
This sliding mechanism causes muscle shortening (contraction).

Contraction of Skeletal Muscle

Muscle fiber contraction operates on an "all or none" principle; not all fibers may contract simultaneously.
Different combinations of fiber contractions create graded responses with varying degrees of shortening.
Rapid stimuli can lead to continuous contraction or tetanus due to increased muscle fiber activation.

Muscle Response to Strong Stimuli

Muscle force correlates with the number of fibers stimulated; more active fibers result in greater muscle tension.
Muscles maintain contraction until energy reserves are depleted.

Energy for Muscle Contraction

Muscles initially utilize stored ATP for energy, sufficient for 4-6 seconds.
After depleting ATP, creatine phosphate (CP) facilitates energy transfer to ADP, regenerating ATP before CP runs out in about 20 seconds.
Anaerobic glycolysis breaks down glucose without oxygen, yielding ATP quickly but inefficiently, producing lactic acid which leads to fatigue.
Aerobic respiration, occurring in mitochondria, breaks down glucose into carbon dioxide and water, generating energy while requiring continuous oxygen.

Muscle Fatigue and Oxygen Debt

Muscle fatigue results in an inability to contract, primarily due to oxygen debt that needs to be repaid to detoxify lactic acid.
Increased lactic acid acidity and ATP depletion diminish muscle contractility.

Types of Muscle Contractions

Isotonic contractions involve myofilaments sliding past each other, resulting in muscle shortening.
Isometric contractions cause muscle tension to increase without shortening.

Muscle Tone

Some muscle fibers remain contracted even at rest, providing muscle tone through involuntary control of various fibers.

Muscles and Body Movements

Movement is achieved as muscles pull on bones at least two attachment points: the origin (movable bone) and insertion (immovable bone).

Effects of Exercise on Muscle

Enhanced muscle usage results in increased muscle size, strength, efficiency, and fatigue resistance.

Smooth Muscle Characteristics

Lacks striations, composed of spindle-shaped cells, and operates involuntarily; found in hollow organ walls and contracts slowly and consistently.

Cardiac Muscle Characteristics

Striated muscle with typically one nucleus per cell, connected by intercalated discs, operates involuntarily and is exclusive to the heart, maintaining steady contractions.

Functions of Muscles

Muscles produce movement, maintain posture, stabilize joints, and generate heat.

Microscopic Anatomy of Skeletal Muscle

Skeletal muscle fibers are multinucleate with nuclei located underneath the sarcolemma.
Sarcolemma is a specialized plasma membrane; sarcoplasmic reticulum is a specialized smooth endoplasmic reticulum.
Myofibrils contain aligned bundles of myofilaments creating distinct I (light) and A (dark) bands.

Types of Ordinary Body Movements

Common movements: flexion (decreases joint angle), extension (opposite of flexion), rotation (bone movement around its axis), abduction/adduction (moving away/toward the midline), and circumduction (cone-shaped movement).

Types of Muscles

Prime mover: primary muscle for a movement.
Antagonist: opposing muscle to the prime mover.
Synergist: assists prime mover and stabilizes movement.

Naming of Skeletal Muscles

Muscles are named based on:
- Direction of fibers (e.g., rectus for straight)
- Size (e.g., maximus for largest)
- Location (e.g., temporalis for located near bone)
- Number of origins (e.g., triceps for three heads)
- Shape (e.g., deltoid for triangular)
- Action (e.g., flexor for muscle that flexes a bone).

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Description

This quiz focuses on the transmission of nerve impulses to muscles, specifically the role of neurotransmitters like acetylcholine and the effects on the sarcolemma. Test your understanding of how nerve impulses initiate muscle contraction through chemical signaling.