Anatomy and Physiology: Muscle Tissue Chapter Review

Flashcards based on the Chapter 11 Review of muscle tissue properties, structures, and functions.

What are the five universal properties of muscle tissue?

Excitability, conductivity, contractility, extensibility, and elasticity

What does the property of "excitability" mean?

The ability to respond to stimuli such as chemical signals, stretch, or electrical changes

What is the definition of "contractility"?

The ability of muscle to shorten when stimulated

How is skeletal muscle characterized in terms of control and appearance?

Voluntary and striated

What causes the striations seen in skeletal muscle?

The arrangement of actin and myosin filaments

What is the name of the connective tissue that surrounds each individual muscle fiber?

Endomysium

What connective tissue layer surrounds a fascicle?

Perimysium

What connective tissue layer surrounds the entire muscle?

Epimysium

What is the sarcolemma?

The plasma membrane of a muscle fiber

What is the sarcoplasm?

The cytoplasm of a muscle fiber

What are myofibrils?

Long protein bundles responsible for muscle contraction

What is the specific function of myoglobin in muscle fibers?

It stores oxygen for muscle use

Why do muscle fibers contain a high number of mitochondria?

To produce the large amounts of $ATP$ required for contraction

What is the sarcoplasmic reticulum ($SR$)?

A smooth endoplasmic reticulum that stores calcium

What triggers muscle contraction by being released from the sarcoplasmic reticulum?

Calcium ions

What are T-tubules?

Tubes that carry electrical signals deep into the muscle fiber

What are the three types of myofilaments?

Thick (myosin), thin (actin), and regulatory (troponin and tropomyosin)

Identify the thick myofilament protein.

Myosin

Identify the thin myofilament protein.

Actin

Which proteins are classified as contractile proteins?

Actin and myosin

Which proteins are classified as regulatory proteins?

Troponin and tropomyosin

What is the function of tropomyosin?

It blocks the myosin-binding sites on the actin filament

What is the role of troponin in muscle contraction?

It binds calcium and moves tropomyosin it out of the way

What is a sarcomere?

The functional contractile unit of a muscle fiber, extending from Z disc to Z disc

What happens to filaments during contraction according to the sliding filament model?

Filaments slide past each other but do NOT shorten

Which structural unit actually shortens during muscle contraction?

The sarcomere

Can skeletal muscle contract without nerve stimulation?

No

What is denervation atrophy?

The shrinking of muscle due to the loss of its nerve supply

What constitutes a motor unit?

One motor neuron and all the muscle fibers it controls

Do all muscle fibers in a single motor unit contract at the same time?

Yes

What are small motor units utilized for?

Fine control

What are large motor units utilized for?

Strength and power

What is the primary neurotransmitter used at the neuromuscular junction ($NMJ$)?

Acetylcholine ($ACh$)

What is the synaptic cleft?

The gap between the neuron and the muscle fiber

What occurs when acetylcholine ($ACh$) binds to receptors on the muscle fiber?

It triggers a muscle action potential

What is the resting membrane potential?

The negative charge kept inside the cell at rest

Which ion causes depolarization when it enters the cell?

Sodium ($Na^+$)

Which ion causes repolarization when it exits the cell?

Potassium ($K^+$)

What is an action potential?

A rapid change in membrane voltage

Name the four phases of muscle contraction in order.

1. Excitation, 2. Excitation–contraction coupling, 3. Contraction, 4. Relaxation

What initiates the excitation phase of muscle contraction?

A nerve signal leading to the release of $ACh$

Which ion is essential for the contraction phase to occur?

Calcium

What provides the chemical energy for muscle contraction?

$$ATP$$

Why does rigor mortis occur after death?

The lack of $ATP$ prevents muscles from relaxing

What is a muscle twitch?

A single cycle of contraction and relaxation

What is a threshold stimulus?

The minimum stimulus needed to cause a muscle to contract

What is recruitment in muscle behavior?

The process of activating more motor units to increase contraction strength

What is temporal summation?

Increasing contraction strength by increasing the frequency of stimulation

Define isometric contraction.

A contraction that develops tension without changing the muscle length

Define isotonic contraction.

A contraction where the muscle changes length while maintaining tension

What occurs during a concentric contraction?

The muscle shortens

What occurs during an eccentric contraction?

The muscle lengthens

What is the primary molecule that directly powers muscle contraction?

$$ATP$$

What is anaerobic fermentation?

The production of $ATP$ without oxygen, resulting in the production of lactate

What is aerobic respiration?

A highly efficient method of producing $ATP$ that requires oxygen

What is the phosphagen system used for?

Short bursts of activity lasting approximately $6\,seconds$

What energy system is used for $30–40\,seconds$ of activity?

The glycogen–lactate system

Which energy system provides for long-term muscle activity?

Aerobic respiration

What is the definition of muscle fatigue?

A decline in muscle performance during activity

What causes fatigue during short, intense exercise?

Ion imbalance and the buildup of $ADP$

What is a primary cause of fatigue during long-duration exercise?

Fuel depletion

What does the acronym $EPOC$ stand for?

Excess Post-exercise Oxygen Consumption

What is the common name for $EPOC$?

Oxygen debt

What is the definition of $EPOC$?

The extra oxygen needed by the body after exercise

Slow-twitch fibers are best suited for what type of activity?

Endurance

Fast-twitch fibers are best suited for what type of activity?

Power and speed

Is cardiac muscle considered voluntary or involuntary?

Involuntary

What are intercalated discs?

Specialized connections between cardiac muscle cells

What is autorhythmicity?

The ability of a heart to contract without external nerve input

Does smooth muscle possess striations?

No

Where in the body is smooth muscle typically found?

In the walls of organs

Is smooth muscle capable of regeneration?

Yes

What systems or factors control the activity of smooth muscle?

The autonomic nervous system, hormones, and stretch

What does the property of "conductivity" involve?

The ability to transmit electrical signals through the tissue

What does the property of "extensibility" mean?

The ability of a muscle to stretch without being damaged

What does the property of "elasticity" mean?

The ability of a muscle to recoil back to its original length after stretching

What is the primary contractile protein in thick filaments?

Myosin

What is the primary contractile protein in thin filaments?

Actin

Which regulatory protein binds directly to calcium?

Troponin

Which regulatory protein blocks the active sites on actin when the muscle is at rest?

Tropomyosin

What determines the boundaries of a single sarcomere?

From one Z disc to the next Z disc

In muscle contraction, what does NOT happen to the myofilaments?

They do not shorten

What type of atrophy is specifically caused by the loss of nerve supply?

Denervation atrophy

A motor unit consists of one neuron and what else?

All the muscle fibers it controls

Small motor units are specialized for which task?

Fine control

Large motor units are specialized for which task?

Strength and power

Acetylcholine ($ACh$) is released into which specific space?

The synaptic cleft

What charge is found inside the cell during the resting membrane potential?

Negative charge

What is the rapid change in membrane voltage called?

An action potential

What ion's entry into the cell causes the charge to become more positive (depolarization)?

Sodium ($Na^+$)

What ion's exit from the cell restores the negative charge (repolarization)?

Potassium ($K^+$)

Rigor mortis occurs because the body runs out of which chemical?

$$ATP$$

The process of activating more motor units is known as what?

Recruitment

Increasing the frequency of stimulation to increase strength is called what?

Temporal summation

An isotonic contraction where the muscle shortens is called?

Concentric contraction

An isotonic contraction where the muscle lengthens is called?

Eccentric contraction

Which energy system provides for about the first $6\,seconds$ of exercise?

The phosphagen system

Which energy system produces lactate as a byproduct?

Anaerobic fermentation

The extra oxygen required after exercise is known as what?

Oxygen debt (or $EPOC$)

Which type of muscle tissue is characterized by intercalated discs?

Cardiac muscle