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Which of the following is called for the response of multiple motor units in a muscle?
Which of the following is called for the response of multiple motor units in a muscle?
Endurance exercise has no effect on muscle strength.
Endurance exercise has no effect on muscle strength.
False
What is the effect of endurance exercise?
What is the effect of endurance exercise?
The rapid up-and-down voltage shift, created by the movement of Na+ and K+ across the cell membrane, is called a(n) __________ potential.
The rapid up-and-down voltage shift, created by the movement of Na+ and K+ across the cell membrane, is called a(n) __________ potential.
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During excitation-contraction coupling, calcium is released into the sarcoplasm and binds to __________.
During excitation-contraction coupling, calcium is released into the sarcoplasm and binds to __________.
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What are the two most important pathways by which ATP is generated in muscle cells?
What are the two most important pathways by which ATP is generated in muscle cells?
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Within a sarcomere, the overlap of actin and myosin produce the _____ bands.
Within a sarcomere, the overlap of actin and myosin produce the _____ bands.
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The cocking of the myosin head into a high-energy position occurs because of:
The cocking of the myosin head into a high-energy position occurs because of:
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_______ muscle frequently exhibits tetanus and is resistant to fatigue.
_______ muscle frequently exhibits tetanus and is resistant to fatigue.
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At the synaptic knob of the motor neuron, calcium stimulates exocytosis of the synaptic vesicles to release ___________ into the synapse.
At the synaptic knob of the motor neuron, calcium stimulates exocytosis of the synaptic vesicles to release ___________ into the synapse.
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Describe myosin ATPase:
Describe myosin ATPase:
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What cellular feature leads to the striated appearance of skeletal muscles?
What cellular feature leads to the striated appearance of skeletal muscles?
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Cells of _______ muscle are considered autorhythmic and contract independently.
Cells of _______ muscle are considered autorhythmic and contract independently.
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The ___________ ___________ of the skeletal muscle cell stores calcium.
The ___________ ___________ of the skeletal muscle cell stores calcium.
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In muscle, which mechanism supplies ATP depends upon:
In muscle, which mechanism supplies ATP depends upon:
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Describe the function of a T-tubule (pick 2):
Describe the function of a T-tubule (pick 2):
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During repolarization, _____ ions diffuse out of the cell, changing the membrane potential back to a negative value.
During repolarization, _____ ions diffuse out of the cell, changing the membrane potential back to a negative value.
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Describe the perimysium:
Describe the perimysium:
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__________ is rarely seen in the muscles of the body:
__________ is rarely seen in the muscles of the body:
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Small motor units are important in _________:
Small motor units are important in _________:
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Infoldings of the sarcolemma, called transverse tubules, are associated with two terminal cisternae, forming a unit called a ________.
Infoldings of the sarcolemma, called transverse tubules, are associated with two terminal cisternae, forming a unit called a ________.
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Define muscle tone.
Define muscle tone.
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The portion of the myofibril from one Z disc to the next is called a __________.
The portion of the myofibril from one Z disc to the next is called a __________.
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Name two regulatory proteins.
Name two regulatory proteins.
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All of the muscle fibers innervated by a single nerve fiber constitute a ________ ________.
All of the muscle fibers innervated by a single nerve fiber constitute a ________ ________.
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Describe smooth muscle.
Describe smooth muscle.
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Describe a neuromuscular junction.
Describe a neuromuscular junction.
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The voltage measured across the muscle cell at rest is called the resting membrane _________.
The voltage measured across the muscle cell at rest is called the resting membrane _________.
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Aerobic metabolism utilizes _________ and __________ as fuel to generate ATP.
Aerobic metabolism utilizes _________ and __________ as fuel to generate ATP.
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The characteristic that allows muscles to pull on those and organs to create movement is called ___________.
The characteristic that allows muscles to pull on those and organs to create movement is called ___________.
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When muscles stretch and recoil, they recoil to a shorter length. This property is called:
When muscles stretch and recoil, they recoil to a shorter length. This property is called:
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Walls of the heart consist of ________ muscle.
Walls of the heart consist of ________ muscle.
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Describe how smooth muscle myocytes differ from cardiocytes.
Describe how smooth muscle myocytes differ from cardiocytes.
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Skeletal muscle exhibits alternating light and dark bands called __________.
Skeletal muscle exhibits alternating light and dark bands called __________.
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Aerobic metabolism produces ________ ATP than does glycolysis.
Aerobic metabolism produces ________ ATP than does glycolysis.
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Indicate the characteristics of cardiac muscle.
Indicate the characteristics of cardiac muscle.
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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.
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.
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Name the type of contraction that involves the development of tension but NO change in length.
Name the type of contraction that involves the development of tension but NO change in length.
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The step in which the muscle fiber develops tension and may shorten is called __________.
The step in which the muscle fiber develops tension and may shorten is called __________.
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Energy needed for short bursts of intense activity are provided by _________ and _________.
Energy needed for short bursts of intense activity are provided by _________ and _________.
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The progressive weakness and loss of contractility that results from prolonged use of the muscle is known as _________.
The progressive weakness and loss of contractility that results from prolonged use of the muscle is known as _________.
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The sliding filament theory describes how _________ occurs.
The sliding filament theory describes how _________ occurs.
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When stimulated, muscle cells will respond with ________ changes across the plasma membrane.
When stimulated, muscle cells will respond with ________ changes across the plasma membrane.
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The process by which action potentials of a nerve fiber lead to action potentials in the muscle fiber is called:
The process by which action potentials of a nerve fiber lead to action potentials in the muscle fiber is called:
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The enzyme that breaks down acetylcholine is called __________.
The enzyme that breaks down acetylcholine is called __________.
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Define acetylcholine.
Define acetylcholine.
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The autonomic nervous system is important in the control of _________ and __________ muscle.
The autonomic nervous system is important in the control of _________ and __________ muscle.
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Describe cardiac muscle.
Describe cardiac muscle.
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Cardiac and smooth muscle are types of _________ muscle.
Cardiac and smooth muscle are types of _________ muscle.
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Indicate the parameters that affect twitch strength.
Indicate the parameters that affect twitch strength.
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List the characteristics of smooth muscle.
List the characteristics of smooth muscle.
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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 ________ _________.
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 ________ _________.
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The prevailing theory regarding muscle contraction is called the _______ ________ theory.
The prevailing theory regarding muscle contraction is called the _______ ________ theory.
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Name the muscle type that is striated, uninucleated, and branching.
Name the muscle type that is striated, uninucleated, and branching.
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Within a skeletal muscle, a ________ extends from one Z-disc to the next and constitutes one contractile unit.
Within a skeletal muscle, a ________ extends from one Z-disc to the next and constitutes one contractile unit.
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Muscle fatigue results from increased levels of:
Muscle fatigue results from increased levels of:
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List the functions of smooth muscle.
List the functions of smooth muscle.
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List events during the relaxation phase.
List events during the relaxation phase.
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A characteristic of all cells, but one that muscles and nerves have developed to the highest degree, is:
A characteristic of all cells, but one that muscles and nerves have developed to the highest degree, is:
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__________ muscle cells have a fusiform shape and taper to a point at the ends.
__________ muscle cells have a fusiform shape and taper to a point at the ends.
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List the characteristics of cardiac cells.
List the characteristics of cardiac cells.
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The time between the stimulus and the twitch is known as the _________ period.
The time between the stimulus and the twitch is known as the _________ period.
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Aerobic respiration is important for producing energy for long-term energy needs.
Aerobic respiration is important for producing energy for long-term energy needs.
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Fibers that are well adapted to aerobic respiration are called ___________-fibers.
Fibers that are well adapted to aerobic respiration are called ___________-fibers.
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The presence of _________ is the immediate trigger for contraction in smooth muscle as well as skeletal and cardiac muscle.
The presence of _________ is the immediate trigger for contraction in smooth muscle as well as skeletal and cardiac muscle.
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The cross-bridge created by the binding of the myosin and actin is broken with the binding of _____________.
The cross-bridge created by the binding of the myosin and actin is broken with the binding of _____________.
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Which of the following is a unique cardiac tissue?
Which of the following is a unique cardiac tissue?
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Tonic contraction of ________ muscle plays an important role in maintaining blood pressure and in keeping the intestine partially contracted.
Tonic contraction of ________ muscle plays an important role in maintaining blood pressure and in keeping the intestine partially contracted.
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Identify a condition that would result in a stronger twitch.
Identify a condition that would result in a stronger twitch.
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_______ muscle typically is slow to contract and slow to relax.
_______ muscle typically is slow to contract and slow to relax.
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Describe what must occur before tropomyosin can move away from the myosin binding sites on actin.
Describe what must occur before tropomyosin can move away from the myosin binding sites on actin.
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Each tropomyosin molecule has a small calcium-binding protein called _______ bound to it.
Each tropomyosin molecule has a small calcium-binding protein called _______ bound to it.
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The glycogen-lactic acid system relies on ________ metabolism.
The glycogen-lactic acid system relies on ________ metabolism.
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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.
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.
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Describe the importance of the elastic elements to muscle function.
Describe the importance of the elastic elements to muscle function.
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Complete ________ is the continuous forceful contraction in a muscle with no relaxation between stimuli.
Complete ________ is the continuous forceful contraction in a muscle with no relaxation between stimuli.
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Gap junctions are important in:
Gap junctions are important in:
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The muscle shortens and moves the load during the _________ phase of a muscle twitch.
The muscle shortens and moves the load during the _________ phase of a muscle twitch.
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The 'cocking' of the myosin head, hydrolysis of ATP and the power stroke occur during the ________ phase of skeletal muscle contraction.
The 'cocking' of the myosin head, hydrolysis of ATP and the power stroke occur during the ________ phase of skeletal muscle contraction.
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The protein found in muscle cells that stores and then releases oxygen when needed is called __________.
The protein found in muscle cells that stores and then releases oxygen when needed is called __________.
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Actions that require physical strength typically involve:
Actions that require physical strength typically involve:
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List three situations that lead to fatigue in long-duration exercise.
List three situations that lead to fatigue in long-duration exercise.
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Define threshold, as applied to muscle physiology.
Define threshold, as applied to muscle physiology.
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The muscle protein composed of two protein chains intertwined together, forming a head and a tail, is called _________.
The muscle protein composed of two protein chains intertwined together, forming a head and a tail, is called _________.
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The nerve fiber ends in a bulbous swelling at each synapse. This structure is called the ____________ ___________.
The nerve fiber ends in a bulbous swelling at each synapse. This structure is called the ____________ ___________.
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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.
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.
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Muscles that are ________ are not attached to bones.
Muscles that are ________ are not attached to bones.
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Indicate the several functions of actin and myosin.
Indicate the several functions of actin and myosin.
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The movement of an object or load results from the development of _______ tension.
The movement of an object or load results from the development of _______ tension.
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A muscle shortens as it maintains tension in a ________ contraction.
A muscle shortens as it maintains tension in a ________ contraction.
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Muscle cells contain ________, a starch-like carbohydrate that provides energy during intense exercise.
Muscle cells contain ________, a starch-like carbohydrate that provides energy during intense exercise.
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The __________ of the heart triggers the wave of electrical excitation that causes the heart to contract.
The __________ of the heart triggers the wave of electrical excitation that causes the heart to contract.
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_________ and _________ muscle can be autorhythmic due to pacemaker cells that depolarize at regular intervals and set off waves of contraction.
_________ and _________ muscle can be autorhythmic due to pacemaker cells that depolarize at regular intervals and set off waves of contraction.
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The change in membrane potential with the entry of sodium ions is called:
The change in membrane potential with the entry of sodium ions is called:
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As the myosin head releases the thin filament, muscle tension declines during what is referred to as the _______ phase of a muscle twitch.
As the myosin head releases the thin filament, muscle tension declines during what is referred to as the _______ phase of a muscle twitch.
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The sarcoplasmic reticulum serves as a reservoir for __________ ions.
The sarcoplasmic reticulum serves as a reservoir for __________ ions.
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Contraction of muscles against a load that resists movement is called ________ EXERCISE.
Contraction of muscles against a load that resists movement is called ________ EXERCISE.
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The region of a sarcomere composed primarily of __________ is called the I band.
The region of a sarcomere composed primarily of __________ is called the I band.
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Indicate the examples of sites for single-unit smooth muscle.
Indicate the examples of sites for single-unit smooth muscle.
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Temporal summation leads to a state of fluttering contraction known as:
Temporal summation leads to a state of fluttering contraction known as:
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A record of the timing and strength of the muscle's contraction is called a __________.
A record of the timing and strength of the muscle's contraction is called a __________.
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As a stimulus increases, an increasing number of motor neurons excite an increasing number of motor units.
As a stimulus increases, an increasing number of motor neurons excite an increasing number of motor units.
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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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