Untitled Quiz

Questions and Answers

Which of the following is called for the response of multiple motor units in a muscle?

Multiple motor unit summation (correct)

Muscle twitch

Treppe

Temporal summation

Endurance exercise has no effect on muscle strength.

False

What is the effect of endurance exercise?

Increases oxygen transport in the blood (correct)

Decreases the amount of mitochondria

Has no effect on muscle strength

The rapid up-and-down voltage shift, created by the movement of Na+ and K+ across the cell membrane, is called a(n) __________ potential.

Action Signup and view all the answers

During excitation-contraction coupling, calcium is released into the sarcoplasm and binds to __________.

Troponin Signup and view all the answers

What are the two most important pathways by which ATP is generated in muscle cells?

Anaerobic fermentation and aerobic respiration Signup and view all the answers

Within a sarcomere, the overlap of actin and myosin produce the _____ bands.

A Signup and view all the answers

The cocking of the myosin head into a high-energy position occurs because of:

Energy released by hydrolysis of ATP Signup and view all the answers

_______ muscle frequently exhibits tetanus and is resistant to fatigue.

Smooth Signup and view all the answers

At the synaptic knob of the motor neuron, calcium stimulates exocytosis of the synaptic vesicles to release ___________ into the synapse.

Acetylcholine Signup and view all the answers

Describe myosin ATPase:

An enzyme located in the myosin head that hydrolyzes ATP Signup and view all the answers

What cellular feature leads to the striated appearance of skeletal muscles?

The alternating light and dark regions of the sarcomere Signup and view all the answers

Cells of _______ muscle are considered autorhythmic and contract independently.

Cardiac Signup and view all the answers

The _ _ of the skeletal muscle cell stores calcium.

Sarcoplasmic reticulum Signup and view all the answers

In muscle, which mechanism supplies ATP depends upon:

The duration of exercise Signup and view all the answers

Describe the function of a T-tubule (pick 2):

T-tubules carry the action potential through the sarcoplasm Signup and view all the answers

During repolarization, _____ ions diffuse out of the cell, changing the membrane potential back to a negative value.

K+ Signup and view all the answers

Describe the perimysium:

The connective tissue covering bundles of muscle fibers Signup and view all the answers

__________ is rarely seen in the muscles of the body:

Complete tetanus Signup and view all the answers

Small motor units are important in _________:

Fine motor control Signup and view all the answers

Infoldings of the sarcolemma, called transverse tubules, are associated with two terminal cisternae, forming a unit called a ________.

Triad Signup and view all the answers

Define muscle tone.

The partial contraction of resting muscles. Signup and view all the answers

The portion of the myofibril from one Z disc to the next is called a __________.

Sarcomere Signup and view all the answers

Name two regulatory proteins.

Troponin and tropomyosin. Signup and view all the answers

All of the muscle fibers innervated by a single nerve fiber constitute a .

Motor unit Signup and view all the answers

Describe smooth muscle.

Uninucleated, non-striated. Signup and view all the answers

Describe a neuromuscular junction.

Site where the nerve fiber communicates with the muscle fiber. Signup and view all the answers

The voltage measured across the muscle cell at rest is called the resting membrane _________.

Potential Signup and view all the answers

Aerobic metabolism utilizes _ and __ as fuel to generate ATP.

Glucose and fatty acids. Signup and view all the answers

The characteristic that allows muscles to pull on those and organs to create movement is called ___________.

Contractility Signup and view all the answers

When muscles stretch and recoil, they recoil to a shorter length. This property is called:

Elasticity. Signup and view all the answers

Walls of the heart consist of ________ muscle.

Cardiac Signup and view all the answers

Describe how smooth muscle myocytes differ from cardiocytes.

Smooth muscle myocytes have no T tubules while cardiac muscles do. Signup and view all the answers

Skeletal muscle exhibits alternating light and dark bands called __________.

Striations Signup and view all the answers

Aerobic metabolism produces ________ ATP than does glycolysis.

More Signup and view all the answers

Indicate the characteristics of cardiac muscle.

It has large stores of glycogen, it uses aerobic respiration almost exclusively, it is rich in myoglobin. Signup and view all the answers

Place in order the steps in the relaxation of muscle: (1) AChE breaks ACh down, (2) active transport pumps in the SR begin to pump calcium back into the cisternae, (3) nerve signal ceases, (4) tropomyosin covers the myosin binding sites, (5) calcium releases from troponin.

3, 1, 2, 5, 4 Signup and view all the answers

Name the type of contraction that involves the development of tension but NO change in length.

Isometric contraction. Signup and view all the answers

The step in which the muscle fiber develops tension and may shorten is called __________.

Contraction Signup and view all the answers

Energy needed for short bursts of intense activity are provided by _ and _.

ATP and creatine phosphate. Signup and view all the answers

The progressive weakness and loss of contractility that results from prolonged use of the muscle is known as _________.

Fatigue Signup and view all the answers

The sliding filament theory describes how _________ occurs.

Muscle contraction. Signup and view all the answers

When stimulated, muscle cells will respond with ________ changes across the plasma membrane.

Electrical. Signup and view all the answers

The process by which action potentials of a nerve fiber lead to action potentials in the muscle fiber is called:

Excitation. Signup and view all the answers

The enzyme that breaks down acetylcholine is called __________.

AChE Signup and view all the answers

Define acetylcholine.

The neurotransmitter secreted at the neuromuscular junction. Signup and view all the answers

The autonomic nervous system is important in the control of _ and __ muscle.

Cardiac and smooth. Signup and view all the answers

Describe cardiac muscle.

Striated, uninucleated, branching. Signup and view all the answers

Cardiac and smooth muscle are types of _________ muscle.

Involuntary Signup and view all the answers

Indicate the parameters that affect twitch strength.

Temperature of the muscle, calcium concentration, how stretched the muscle was just before it was stimulated, stimulation frequency. Signup and view all the answers

List the characteristics of smooth muscle.

Has no T tubules, has little SR, uninucleated. Signup and view all the answers

A synapse is the point where a nerve fiber meets a target cell. When the target cell is a muscle fiber, this type of synapse is called the _.

Neuromuscular junction Signup and view all the answers

The prevailing theory regarding muscle contraction is called the _ __ theory.

Sliding filament Signup and view all the answers

Name the muscle type that is striated, uninucleated, and branching.

Cardiac. Signup and view all the answers

Within a skeletal muscle, a ________ extends from one Z-disc to the next and constitutes one contractile unit.

Sarcomere Signup and view all the answers

Muscle fatigue results from increased levels of:

Lactic acid. Signup and view all the answers

List the functions of smooth muscle.

Constrict or dilate blood vessels to control blood pressure, regulate pupil diameter, and move material through the digestive tract. Signup and view all the answers

List events during the relaxation phase.

Calcium levels in sarcoplasm fall, muscle tension declines, myosin releases thin filaments. Signup and view all the answers

A characteristic of all cells, but one that muscles and nerves have developed to the highest degree, is:

Excitability. Signup and view all the answers

__________ muscle cells have a fusiform shape and taper to a point at the ends.

Smooth Signup and view all the answers

List the characteristics of cardiac cells.

They are resistant to fatigue, they contract with regular rhythm, they contract nearly in unison. Signup and view all the answers

The time between the stimulus and the twitch is known as the _________ period.

Latent Signup and view all the answers

Aerobic respiration is important for producing energy for long-term energy needs.

True Signup and view all the answers

Fibers that are well adapted to aerobic respiration are called ___________-fibers.

Slow Signup and view all the answers

The presence of _________ is the immediate trigger for contraction in smooth muscle as well as skeletal and cardiac muscle.

Calcium Signup and view all the answers

The cross-bridge created by the binding of the myosin and actin is broken with the binding of _____________.

ATP Signup and view all the answers

Which of the following is a unique cardiac tissue?

Intercalated discs Signup and view all the answers

Tonic contraction of ________ muscle plays an important role in maintaining blood pressure and in keeping the intestine partially contracted.

Smooth. Signup and view all the answers

Identify a condition that would result in a stronger twitch.

Warm muscle conditions. Signup and view all the answers

_______ muscle typically is slow to contract and slow to relax.

Smooth. Signup and view all the answers

Describe what must occur before tropomyosin can move away from the myosin binding sites on actin.

Calcium must bind to troponin. Signup and view all the answers

Each tropomyosin molecule has a small calcium-binding protein called _______ bound to it.

Troponin. Signup and view all the answers

The glycogen-lactic acid system relies on ________ metabolism.

Anaerobic. Signup and view all the answers

Action potentials cause the opening of voltage-gated calcium ion channels in plasma membrane and the _. This leads to the release of calcium from the sarcoplasmic reticulum.

T tubules Signup and view all the answers

Describe the importance of the elastic elements to muscle function.

Elastic elements provide the recoil that helps return the sarcomere to its resting length. Signup and view all the answers

Complete ________ is the continuous forceful contraction in a muscle with no relaxation between stimuli.

Tetanus Signup and view all the answers

Gap junctions are important in:

Cardiac muscle because they allow the cells to contract in a coordinated fashion. Signup and view all the answers

The muscle shortens and moves the load during the _________ phase of a muscle twitch.

Contraction. Signup and view all the answers

The 'cocking' of the myosin head, hydrolysis of ATP and the power stroke occur during the ________ phase of skeletal muscle contraction.

Contraction Signup and view all the answers

The protein found in muscle cells that stores and then releases oxygen when needed is called __________.

Myoglobin. Signup and view all the answers

Actions that require physical strength typically involve:

Large motor units Signup and view all the answers

List three situations that lead to fatigue in long-duration exercise.

Central fatigue, fuel depletion, electrolyte loss. Signup and view all the answers

Define threshold, as applied to muscle physiology.

The minimum voltage necessary to generate an action potential. Signup and view all the answers

The muscle protein composed of two protein chains intertwined together, forming a head and a tail, is called _________.

Myosin. Signup and view all the answers

The nerve fiber ends in a bulbous swelling at each synapse. This structure is called the __ _.

Synaptic knob. Signup and view all the answers

In contrast to the action potential, the ___________ potential causes the opening of ion channels, which results in the initial movement of sodium and potassium across the plasma membrane at the neuromuscular junction.

End-plate. Signup and view all the answers

Muscles that are ________ are not attached to bones.

Involuntary. Signup and view all the answers

Indicate the several functions of actin and myosin.

Cellular movement, internal transportation, chromosome movement. Signup and view all the answers

The movement of an object or load results from the development of _______ tension.

External. Signup and view all the answers

A muscle shortens as it maintains tension in a ________ contraction.

Concentric. Signup and view all the answers

Muscle cells contain ________, a starch-like carbohydrate that provides energy during intense exercise.

Glycogen. Signup and view all the answers

The __________ of the heart triggers the wave of electrical excitation that causes the heart to contract.

Pacemaker. Signup and view all the answers

_ and _ muscle can be autorhythmic due to pacemaker cells that depolarize at regular intervals and set off waves of contraction.

Cardiac and smooth. Signup and view all the answers

The change in membrane potential with the entry of sodium ions is called:

Depolarization Signup and view all the answers

As the myosin head releases the thin filament, muscle tension declines during what is referred to as the _______ phase of a muscle twitch.

Relaxation. Signup and view all the answers

The sarcoplasmic reticulum serves as a reservoir for __________ ions.

Calcium. Signup and view all the answers

Contraction of muscles against a load that resists movement is called ________ EXERCISE.

Resistance. Signup and view all the answers

The region of a sarcomere composed primarily of __________ is called the I band.

Actin. Signup and view all the answers

Indicate the examples of sites for single-unit smooth muscle.

Wall of uterus, wall of stomach, wall of bladder. Signup and view all the answers

Temporal summation leads to a state of fluttering contraction known as:

Incomplete tetanus Signup and view all the answers

A record of the timing and strength of the muscle's contraction is called a __________.

Myogram. Signup and view all the answers

As a stimulus increases, an increasing number of motor neurons excite an increasing number of motor units.

This reflects the relationship between stimulus strength and motor unit recruitment. Signup and view all the answers

Study Notes

Muscle Tissue Fundamentals

Muscle tone refers to the partial contraction of resting muscles, maintaining posture and readiness for activity.
The sarcomere, the contractile unit of muscle fibers, extends from one Z disc to the next within myofibrils, facilitating muscle contraction.
Troponin and tropomyosin are regulatory proteins that play crucial roles in muscle contraction, particularly in the interaction with calcium ions.

Muscle Organization and Function

A motor unit consists of all muscle fibers innervated by a single nerve fiber, which coordinately contract in response to stimulation.
Smooth muscle is characterized as uninucleated and non-striated, supporting involuntary movements in various organs.
The neuromuscular junction is the critical site where nerve signals stimulate muscle fiber contraction.

Muscle Physiology

The resting membrane potential of muscle cells is approximately -90mV, critical for maintaining cellular excitability.
Aerobic metabolism primarily utilizes glucose and fatty acids for ATP production, advantageous for prolonged energy needs.
Contractility is the characteristic that enables muscles to exert force and generate movement by pulling on bones and organs.

Muscle Properties

Elasticity allows muscles to stretch and recoil to their original length after contraction, enhancing functional capability.
Cardiac muscle, striated, uninucleated, and branching, forms the heart walls, and is responsible for pumping blood.
Muscle contraction types include isotonic (changing length) and isometric (constant length), with isometric contractions developing tension without movement.

Contraction Mechanism

During muscle relaxation, AChE breaks down acetylcholine, the neurotransmitter, ceasing the nerve signal, leading to subsequent muscle relaxation.
Calcium's role is vital for muscle contraction initiation, linking the sliding filament mechanism of actin and myosin.
The sliding filament theory explains how overlapping thick (myosin) and thin (actin) filaments in sarcomeres lead to muscle contraction.

Energy and Fatigue

Short bursts of activity primarily utilize ATP and creatine phosphate through anaerobic pathways, enabling rapid energy release.
Muscle fatigue stems from lactic acid accumulation, depletion of energy stores, and electrolyte imbalances during prolonged exertion.
Slow-twitch fibers are adapted for aerobic respiration and endurance, allowing sustained activity.

Specialized Structures

Intercalated discs are unique to cardiac muscles, enhancing cell communication and coordinated contractions.
Myoglobin, a muscle protein, stores oxygen, which is essential for aerobic metabolism and energy production during extended activity.
T-tubules and the sarcoplasmic reticulum are critical for calcium release and muscle fiber excitation-contraction coupling.

Muscle Control and Coordination

The autonomic nervous system regulates involuntary muscle types: cardiac and smooth muscle, ensuring automatic control of essential body functions.
Action potentials trigger calcium ion channels, leading to muscle activation through neuromuscular transmission at the synaptic knob.
Gap junctions in cardiac muscles allow synchronized contraction, vital for effective heart function.

Muscle Rhythms and Responses

Cardiac and smooth muscles are autorhythmic, meaning they can initiate contraction without external stimuli due to pacemaker cells.
Excitability is a key characteristic in both nerve and muscle cells, allowing them to respond to stimuli effectively.
Threshold voltage is necessary to generate action potentials, essential for initiating contraction in muscle fibers.

Summary of Muscle Mechanics

Muscle contraction occurs in phases: latent, contraction, and relaxation, with distinct physiological and biochemical processes in each.
A myogram records muscle contraction timing and strength, providing insights into muscle performance.
The I band in a sarcomere consists mainly of actin filaments, while the A band contains both actin and myosin for contraction dynamics.### Muscle Physiology and Contraction Mechanisms
Multiple Motor Unit Summation: Involves the recruitment of more motor units for a stronger muscle contraction.
Muscle Twitch: A single brief contraction of a muscle fiber followed by relaxation.
Treppe: A staircase-like increase in muscle tension when stimuli are applied repeatedly.
Temporal Summation: Increased muscle tension from successive stimuli applied in quick succession.

Endurance Exercise

Increases oxygen transport in the blood, enhancing aerobic capacity.
Effect on Muscle Strength: Endurance exercise has no direct impact on increasing muscle strength.
Mitochondrial Effect: Contrary to the statement, endurance training typically increases the number of mitochondria.

Action Potential

Defined as the rapid voltage shift due to Na+ influx and K+ efflux across the cell membrane, essential for muscle contraction.

Excitation-Contraction Coupling

Calcium ions released into the sarcoplasm bind to troponin, facilitating muscle contraction.

ATP Generation in Muscle Cells

Primarily produced through anaerobic fermentation and aerobic respiration.

Sarcomere Structure

A bands: Regions of overlapping actin and myosin, contributing to muscle striation.
Light and dark bands in the sarcomere create the striated appearance of skeletal muscles.

Myosin Head Function

The cocking of the myosin head into a high-energy state relies on energy released from ATP hydrolysis.

Muscle Types and Characteristics

Smooth Muscle: Exhibits tetanus and is resistant to fatigue.
Cardiac Muscle: Autorhythmic and contracts independently from neural stimulation.

Calcium Storage and Action

Sarcoplasmic Reticulum: Organelle responsible for storing calcium ions in skeletal muscle cells.
T-tubules: Carry action potentials through the sarcoplasm and stimulate terminal cisternae to release calcium.

Factors Influencing ATP Supply

The method of ATP generation in muscle cells is largely dependent on the duration of exercise.

T-tubule Functions

T-tubules conduct action potentials and trigger calcium release from the sarcoplasmic reticulum, facilitating contraction.

Repolarization Process

During repolarization, K+ ions diffuse out of the cell, restoring a negative membrane potential.

Connective Tissue Structure

Perimysium: Connective tissue that surrounds bundles of muscle fibers, providing support and structure.

Muscle Contraction Patterns

Rarely observed is complete tetanus, which represents a sustained contraction without relaxation.
Fine motor control relies on small motor units for precision and dexterity, unlike coarse control used in larger muscles.

Structural Units

A triad consists of a T-tubule flanked by two terminal cisternae, vital for coordinating muscle contraction.

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