Chapter 9

Check all that occur during the production of an action potential.

Neurotransmitters bind to ligand-gated ion channels, causing them to open Voltage-gated K+ channels open, allowing K+ to move out of the cell

A band

both actin and myosin

In ___________, muscle fibers partially relax between contractions, and in ___________, no relaxation occurs between contractions.

incomplete tetanus, complete tetanus

H band

myosin

The point where the axon terminal synapses with the muscle fiber sarcolemma is called the _____________.

neuromuscular junction

As a result of extreme muscular fatigue, muscles can become incapable of relaxing or contracting, which is called _____________. Similarly, several hours after death, ATP levels decline, causing muscle muscle rigidity, known as ____________.

physiological contracture, rigor mortis

Movement of the myosin head while the cross-bridge is attached is called the ________, and the return of the head to its original position after releasing from the cross-bridge is called the __________.

power stroke, recovery stroke

When _________ causes more motor units to contract in a whole muscle as the stimulus strength increases, the relationship between increased stimulus strength and increased number of motor units contracting is called ___________.

recruitment, multiple motor unit summation

The force of a contraction can be increased with _________, which involves increasing the force of contraction of the muscle fibers, as well as with __________, which involves increasing the number of muscle fibers contracting.

summation, recruitment

If body temperature drops, muscles respond by contracting rapidly in order to produce heat, a process known as ___________.

shivering

A single motor neuron and the muscle fibers that it innervates is called a ___________.

motor unit

Match the characteristic of each muscle type with its function.

1. Skeletal muscle- Constitutes 40% of the body's weight; voluntarily controlled. 2. Smooth muscle- The most widely distributed muscle type; involuntarily controlled. 3. Cardiac muscle- Found only in the heart; involuntarily controlled.

Put the following events of excitation-contraction coupling in the correct order.

1. A nerve impulse causes ACh to be released at a neuromuscular junction 2. The T tubules carry the action potential to the interior of the muscle fiber 3. Calcium ions are released into the sarcoplasm 4. Calcium ions bind to troponin molecules on the actin myofilaments 5. The troponin-tropomysin complex moves, exposing active sites on the actin myofilaments 6. The heads of myosin myofilaments bind to sites on the actin myofilaments, forming cross-bridges

Match each phase of a muscle twitch with the associated event.

1. An action potential is propagated to the presynaptic terminal- Lag phase 2. Depolarization occurs- Lag phase 3. Cross-bridges from- Contraction phase 4. Energy is released as heat- Contraction phase 5. Calcium ions are actively transported into the sarcopasmic reticulum- Relaxation phase 6. Cross-bridge formation is inhibited- Relaxation phase

Indicate whether each statement is true or false.

1. Cardiac muscle is striated- true 2. Each cardiac muscle cell contains multiple nuclei- false 3. Intercalated discs attach cardiac cells to each other- true 4. Cardiac muscle cells cannot be autorhythmic- false

Match the functional property of muscle tissue with its description.

1. Contractility- A muscle shortens forcefully. 2. Excitability- A muscle responds to a stimulus. 3. Extensibility- A muscle can stretch beyond its normal resting length and still contract 4. Elasticity- A muscle recoils to its original resting length after having been stretched.

Indicate whether each statement is true or false.

1. During contraction, the myosin myofilaments shorten- true 2. During contraction, the actin myofilaments shorten- false 3. The sliding filament model explains how myofilaments slide past each other- true 4. The sliding of the myofilaments past each other cause the sarcomere to shorten- true

Indicate whether each statement is true or false.

1. Each cycle of cross-bridge formation requires one ATP molecule. true 2. Energy stored in the head of a mysosin molecule is not released during cross-bridge movement. false 3. Movement of the myosin head causes the actin myofilament to slide. true 4. The myosin head breaks ATP into ADP and phosphate. true

Match the connective tissue with the skeletal muscle component that it surrounds.

1. Endomysium- Muscle fibers 2. Perimysium- Fasciculi 3. Epimysium- Muscles

Indicate whether each statement regarding muscle relaxation is true or false.

1. It takes about twice as long for a muscle to contract as it does to relax- false 2. Energy is needed to make muscles relax- true 3. Relaxation occurs when Ca2+ is transported back into the sarcoplasmic reticulum- true 4. The active transport of Ca2+ into the sarcoplasmic reticulum requires ATP- true

Indicate whether each statement is true or false.

1. Most muscle fibers are innervated by only one neuron- true 2. Muscle fibers do not have arterial supply- false 3. Each motor neuron innervates more than one muscle fiber- true 4. Motor neurons can cause muscle cells to contract- true

Indicate whether each statement is true or false regarding action potentials and the all-or-none principle.

1. Once the threshold is reached, an action potential will proceed without stopping- true 2. The action potentials will be different in different parts of the cell- false 3. If threshold is not reached, an action potential will occur, but it will be weaker- false 4. If threshold is not reached, an action potential will not occur- true

Match the component of a neuromuscular junction with its location.

1. Postsynaptic membrane Muscle plasma membrane 2. Presynaptic terminal Axon 3. Synaptic cleft Between the presynaptic terminal and the muscle fiber

Match the type of muscle fatigue with its cause.

1. Psychological fatigue - An individual falsely believes that muscles can no longer function. 2. Muscular fatigue - Drop in ATP levels causes calcium ion imbalances. 3. Synaptic fatigue - Synaptic vesicles become depleted of ACh.

Match the muscle fiber component with its description.

1. Sarcolemma- Plasma membrane 2. Endomysium- Connective tissue 3. Sarcoplasm- Cytoplasm of a muscle cell 4. Myofibril- Bundle of protein filaments

Match the description with the type of muscle contraction.

1. The length of the muscle changes- Isotonic contraction 2. No change in the length of the muscle- Isometric contraction 3. The tension of the muscle increases during the contraction- Isometric contraction 4. The tension of the muscle remains constant during contraction- Isotonic contraction

Check all that apply to smooth muscle regulation.

Hormones stimulate muscle cells The autonomic nervous system innervates smooth muscle Nerves that innervate smooth muscle release norepinephrine and epinephrine

Which of the following is not a function of the myosin heads?

Produce tropomyosin to facilitate binding to actin molecules

________ occurs when a rested muscle is stimulated repeatedly, at low frequencies, allowing relaxation between contractions. This causes each contraction to be stronger than the previous one until the levels of tension are equal between contractions.

Treppe

I band

actin

The myofilaments that contain two strands of F actin coiled together to form a double helix are ________ myofilaments, and the myofilaments that are composed of molecules that are shaped like golf clubs are _________ myofilaments.

actin, myosin

Thin myofilaments are _______ myofilaments, and thick myofilaments are _________ myofilaments.

actin, myosin

The cycle of a mysosin molecule forming cross-bridges, moving, then releasing and returning to its original position is called _____________.

cross-bridge movement

During the ___________ phase, the inside of the cell becomes positively charged, and during the _________ phase, the membrane potential returns to its resting value.

depolarization, repolarization

When the sarcomere contracts, the H band does what

disappears

Hypertrophy means that there is a(n) ______________ in the size of the muscle fibers, and there is usually _________ muscle fibers.

increase, no change in the number of

The constant tension produced by muscles for long periods of time is ___________.

muscle tone

Muscle cells originate from __________.

myoblasts

The charge difference across the plasma membrane of an unstimulated cell is called the __________.

resting membrane potential

During exercise, the rate of chemical reactions increases in muscle cells, causing the body's temperature to ________.

rise

Each presynaptic terminal contains ___________, which contain the neurotransmitter __________ that, when released, cause ligand-gated Na+ channels to open in the postsynaptic membrane. This causes __________ in the muscle cell.

synaptic vesicles, acetylcholine, depolarization