A&P 1 Connect CH 9 Practice
Which enzyme is responsible for the transfer of a phosphate group from ATP to the light myosin molecules on the heads of myosin molecules?
Myosin kinase
List the end products of aerobic respiration.
-ATP -carbon dioxide -water
List the events that occur during the lag phase of the muscle twitch.
-An action potential is propagated to the presynaptic terminal of the motor neuron. -Calcium ions diffuse from the sarcoplasmic reticulum into the sarcoplasm.
Visceral smooth muscle is found in which of the following systems?
-Digestive -Urinary -Reproductive
List the functional properties of all muscle tissue types.
-Excitability -Contractility -Elasticity -Extensibility
Identify the types of ion channels involved in producing action potentials in muscle fibers
-Potassium voltage-gated channels -Sodium voltage-gated channels
Name the events that occur during the LAG phase of the muscle twitch.
-Sodium ions diffuse into the muscle fiber, causing a local depolarization that exceeds threshold and produces an action potential. -The troponin-tropomyosin complex changes its position and exposes active sites on the actin myofilaments.
Describe what occurs when recruitment increases
-The number of fibers contracting increases. -The amount of force produced during contraction increases
Describe what occurs when recruitment increases.
-The number of fibers contracting increases. -The amount of force produced during contraction increases
During intense muscular activity, creatine phosphate levels ______. Select all that apply.
-are unable to support maximal contraction after 8-10 seconds -decline quickly
Structures that contain multiunit smooth muscles include ______.
-arteries -the iris of the eye -pulmonary airways
The axons of the motor neurons extend from cell bodies located in the ______ to skeletal muscle fibers
-brain -spinal cord
The muscular fascia:
-compartmentalizes individual muscles or groups of muscles -is a layer of dense irregular connective tissue
The major functions of the muscular system include ______
-constriction of organs and vessels -body movement -respiration
The synaptic vesicles of the presynaptic neuron of the neuromuscular junction ______
-contain neurotransmitters -contain ACh -contain acetylcholine
A single muscle fiber twitch ______.
-contains a contraction and relaxation phase -is very short in duration
The cell bodies of motor neurons are located _______.
-in the brain -in the spinal cord
Recruitment increases the amount of force produced by ______.
-increasing the number of muscle fibers contracting -increasing the number of motor units stimulated
Action potential frequency ______
-is the rate at which a neuron is generating action potentials -is the number of action potentials produced per unit of time
The muscle plasma membrane in the area of the neuromuscular junction is the ______
-postsynaptic membrane -motor end plate
The sarcoplasmic reticulum of __________ muscle lacks the T tubule system found in ________ muscle.
-smooth -skeletal
As the strength of the stimulus applied to a neuron or a muscle fiber increases ______.
-the action potential frequency increases -the number of action potentials per unit of time increases
Once a cell's threshold has been reached ______.
-the sodium voltage-gated channels open rapidly -the depolarization phase begins
Describe myoglobin.
A molecule that stores oxygen in muscles
What is calmodulin?
A protein that replaces troponin in smooth muscle cells
ATP can be regenerated by transferring a phosphate from creatine phosphate to ______
ADP
In order for myosin to initiate contraction ______ must bind to the myosin head
ATP
When does the sarcoplasmic reticulum release calcium?
Calcium is released when the muscle fiber is depolarized or excited.
Describe what must occur before tropomyosin can move away from the myosin binding sites
Calcium must bind to troponin
Name the regulatory protein associated with the thick filament of smooth muscle which activates myosin light-chain kinase.
Calmodulin
After acetylcholine is broken down into acetic acid and choline by the enzyme acetylcholinesterase, what happens to the choline molecules?
Choline is actively transported back into the presynaptic neuron.
When is ATP required by muscle cells?
During both relaxation & contraction
What causes the cocking of the myosin head into a high energy (cocked) position?
Energy released by hydrolysis of ATP
Which phase of contraction links the action potential in the sarcolemma to the activation of the myofilament?
Excitation-contraction coupling
True or false: The reduction of muscle mass with age is known as myoplasia.
False Age-related loss of muscle mass is called sarcopenia.
Which of the following is NOT a characteristic of slow oxidative fibers?
Few blood vessels
Which of the following is true of fine motor control?
Fine motor control requires small motor units
During muscle contraction, each _____ monomer has an open active site to bind with the protein myosin.
G-actin
Identify the structures in which cardiac muscle is located.
Heart
Which of the following would increase twitch strength in a muscle fiber?
High stimulus frequency
Where do you find acetycholine?
In synaptic vesicles
Which describes smooth muscle?
It is slow to contract and slow to relax.
What is active tension?
It is the force applied to an object to be lifted when a muscle contracts.
Describe the conditions needed to cause treppe.
Maximal stimuli but at a low frequency.
Describe the composition of human muscles in regards to fast and slow-twitch muscle fibers.
Most muscles have have both fast and slow-twitch muscle fibers but the numbers of each fiber type will vary dependent upon the muscle.
What term is used to describe a single, brief contraction and relaxation cycle in a muscle fiber?
Muscle twitch
Sodium is more abundant in which fluid compartment?
Outside the plasma membrane
Myoglobin would be most abundant in what type of muscle fiber?
Oxidative (slow) fibers
Name the term used to describe the difference between the resting rate of oxygen consumption and the elevated rate following exercise.
Oxygen debt
Name the type of stimuli that become progressively stronger and produce action potentials in axons of additional motor units.
Sub-maximal
________ -stimuli have no additional effects on force production than a maximal stimuli.
Supra-maximal
What returns the myosin heads to the "energized" configuration required for another cross-bridge formation?
The binding and hydrolysis of ATP
What triggers the release of calcium ions from the sarcoplasmic reticulum?
The depolarization of the adjacent transverse tubule
What is oxygen debt?
The difference between the resting rate of oxygen consumption and the elevated rate following exercise
Define acetylcholinesterase
The enzyme that breaks down the neurotransmitter in the neuromuscular junction
What is threshold, as applied to muscle physiology?
The minimum voltage necessary to generate an action potential
Which of the following ionic movements causes the repolarization phase of the action potential?
The movement of a large number of potassium ions out of the cell.
Which of the following ionic movements causes the depolarization phase of the action potential?
The movement of a large number of sodium ions into the cell
True or false: A muscle fiber twitch does not last long enough or generate enough tension to perform any work.
True
True or false: A whole muscle is usually innervated by more than one neuron.
True
True or false: In treppe, heat released by each twitch stimulates more efficient enzyme action.
True
True or false: Most regular muscle contractions are not strictly isotonic or isometric.
True
True or false: Recruitment occurs when more nerve fibers excite more motor units.
True
True or false: Sarcoplasmic reticulum is present in smooth muscle but it lacks the T tubule system found in skeletal muscle.
True
True or false: The proportion of slow twitch and fast twitch fibers differs among muscles.
True
What type of smooth muscle tissue is found within the digestive, reproductive and urinary tracts.
Visceral smooth muscle
Dense bodies and dense areas in smooth muscle are equivalent to _______ disks in skeletal muscle.
Z
The filamentous protein network that serves as the attachment site for actin myofilaments is called the _____
Z disk
The boundaries of the sarcomere are defined by the _____
Z disks
The energized or cocked myosin heads bind to _____ forming a _______.
actin, cross-bridge
The number of action potentials produced per unit of time is the ______.
action potential frequency
The force applied to an object to be lifted when a muscle contracts is called the ______.
active tension
The power stroke occurs because the myosin heads go from a high energy position to a low energy position once ______ is released.
adenine diphosphate (ADP)
Creatine phosphate is used to store energy that can be used to synthesize _____.
adenine triphosphate (ATP)
The mechanism of ATP production that requires oxygen is ______ respiration.
aerobic
The method of ATP production that can produce up to 36 ATP molecules for each glucose molecule is ___________ respiration.
aerobic
ATP, carbon dioxide, and water are the major end products of ______.
aerobic respiration
Each action potential:
affects only a small area of the plasma membrane of the cell at a time
A maximal stimulus produces action potentials in the axons of _____ motor units of that muscle.
all
When a maximal stimulus occurs, action potentials are generated in the axons of ______ of that muscle
all motor units
Fast-twitch muscle fibers can be enlarged by ______ exercise.
anaerobic
Muscles ______.
are composed of slow and fast fibers
The muscle tissue found in the heart is called ______muscle.
cardiac
The muscle type found only in the heart is _________muscle. Its contractions provide the major force for moving blood through the circulatory system.
cardiac
An isotonic contraction in which tension in the muscle increases enough to overcome the opposing resistance, while the muscle shortens is a(n) ______ contraction.
concentric
A skeletal muscle myofilament ______
contains either actin or myosin proteins
A skeletal muscle myofilament ______.
contains either actin or myosin proteins
The ability of muscle to shorten forcefully is called ______
contractility
ATP is the muscle's first source of energy; however, during intense muscular contraction, _____ levels are quickly depleted.
creatine phosphate
During rest conditions, the energy from aerobic respiration is used to produce ______.
creatine phosphate
During a single contraction, each myosin molecule undergoes the cycle of cross-bridge formation, movement, release, and return to its original position many times. This process is called _______
cross-bridge cycling
Actin myofilaments are attached to dense bodies in the ______.
cytoplasm
The sarcoplasm of a muscle fiber is its ______
cytoplasm
A shift in the membrane potential towards a less negative value is called a ______
depolarization
A shift in the membrane potential towards a less negative value is called a ______.
depolarization
The sodium voltage-gated ion channel is primarily responsible for the _______ phase of the action potential while the potassium voltage-gated ion channel is primarily responsible for the _____ phase
depolarization, repolarization
A muscular contraction in which tension is maintained in a muscle, but the opposing resistance is great enough to cause the muscle to increase in length is a(n) ______ contraction.
eccentric
Anaerobic training, such as weight lifting, enlarges the _____ muscle fibers.
fast-twitch
The first stage of anaerobic and aerobic respiration is _______
glycolysis
The process of breaking down a glucose molecule into two molecules of pyruvic acid is called ______
glycolysis
Whole muscles respond to stimuli in a _____ fashion.
graded
Energy released from the hydrolysis of ATP is stored _____
in the heads of the myosin molecules
In order to increase the strength of the contraction of a muscle fiber, the stimulus frequency should _______.
increase
Increasing recruitment in a muscle, causes the strength of the contraction to _____ by ______.
increase, increasing the number of muscle fibers contracting
As the strength of the stimulus event increases, the frequency of the action potentials generated ______.
increases
The actin and myosin fibers in smooth muscle are arranged in ______.
loose bundles
A whole muscle is typically innervated by ______.
more than one neuron
Specialized nerve cells that stimulate muscles to contract are called ______.
motor neurons
All of the muscle fibers innervated by a single nerve fiber constitute a ______.
motor unit
The layer of dense irregular collagenous connective tissue that compartmentalizes individual muscles or groups of muscles is called the ______
muscular fascia
Calcium ion imbalances that occur as ATP levels drop lead to ______ fatigue.
muscular or muscle
During the recovery stroke, ATP binds to the _____ to recock it, beginning the cycle again
myosin head
The energized _____ attach to the exposed myosin binding site on G-actin forming a cross-bridge.
myosin heads
While muscle is relaxed, energy stored in the _______ is held in reserve until the next contraction.
myosin heads
During contraction of the sarcomere, the M line helps hold the ______ in place.
myosin myofilament
During contraction, the M line stabilizes the ________ myofilament, similar to the way the Z disk holds the actin myofilament in place.
myosin or thick
If the area just inside the membrane of a cell is more negative than the outside, the resting membrane potential will have a ______ value.
negative
The voltage of a repolarizing neuron or muscle fiber is becoming more ______ with respect to the extracellular fluid around it
negative
A chemical released at the distal end of an axon that either stimulates or inhibits an adjacent cell is called a(n) ______.
neurotransmitter
Substances that are released from a presynaptic membrane and inhibit or stimulate the activity of an adjacent cell are called ______
neurotransmitters
Muscle elasticity is defined as the ability ______
of a muscle to recoil to its original resting length after being stretched
The elasticity of muscle and its connective tissue contribute to _____ tension.
passive
The tension applied to the load when a muscle stretches but is not stimulated is called ______-tension.
passive
Each fasciculus is surrounded by a thick connective tissue layer called the ______
perimysium
Movement of the myosin molecule while the cross-bridge is attached is called the _______ stroke.
power
Upon the release of ADP, the myosin head pulls the thin filament past the myosin myofilaments; this is referred to as the _____
power stroke
Upon the release of ADP, the myosin head pulls the thin filament past the myosin myofilaments; this is referred to as the ______
power stroke
The creatine phosphate reaction ______.
produces ATP relatively quickly as long as creatine phosphate is available in the fiber
The phosphorylation of ADP by creatine phosphate occurs _______
rapidly
The development of rigid muscles several hours after death is called ______
rigor mortis
The actin and myosin myofilaments form highly ordered units called ______, which are joined end to end to form the ______.
sarcomeres, myofibrils
The formation of visceral smooth muscle is arranged in ______.
sheets
What is rigor mortis?
stiffening of muscles after death
Muscles are connected to bones or the skin by ______
tendons
The cell bodies of motor neurons are located in ______ and the axons of the motor neurons extend to ______.
the brain and spinal cord, skeletal muscle fibers
The dephosphorylation of ATP by myosin-ATPase leads to:
the cocking of the myosin head
Passive tension is generated by ______.
the elastic components of muscle and surrounding connective tissue
In order for local potentials to trigger an action potential, the membrane potential must reach a level called the ______
threshold
The minimum voltage necessary to generate an action potential is called the _______
threshold
Name the molecule used to store energy that can be used to synthesize ATP.
Creatine phosphate
What structure in a muscle fiber acts as a calcium reservoir or storage site?
Sarcoplasmic reticulum
Name the muscle fibers that contain abundant mitochondria, myoglobin and are typically red in color.
Slow oxidative
Tube-like invaginations of the sarcolemma that conduct action potentials toward the center of the muscle fiber are called _____
transverse tubules
The molecule that inhibits the binding of myosin to actin by blocking the binding site is _____.
tropomyosin
The organelles that are located within the presynaptic terminals and contain neurotransmitter are called synaptic ______
vesicles
The generation and propagation of the action potential in an axon involves ______.
voltage-gated ion channels
Give an example of the contractility of muscle
Lifting a textbook
Cardiac muscle is found within ______.
the wall of the heart
The cytoplasm of a muscle cell is called the _______
sarcoplasm
List the characteristics or structures that enable automaticity in cardiac muscle?
-Branched fibers -Intercalated disks
Identify characteristics of hypertrophy.
-Can occur in response to exercise -Is an increase in the size of a muscle fiber
Name the muscle types that normally contract involuntarily.
-Cardiac muscle -Smooth muscle
What does the sliding filament theory of muscle contraction predict about myofilaments and sarcomere length?
-During contraction, the total length of the sarcomere decreases. -During contraction, the thin myofilaments slide past the thick myofilaments.
Identify the functions of skeletal muscle.
-Thermoregulation -Locomotion -Facial expression -Inhalation and exhalation
List the properties of voltage-gated channels.
-They open and close in response to small voltage changes in the membrane potential. -They are specific for the type of ion that passes through them.
Choose characteristics of the sodium-potassium ion pump
-Uses ATP -Pumps sodium out of the cell against its concentration gradient
The function of a tendon is to ______.
-connect muscles to the skin -connect muscles to bone
List the characteristics or structures common to SKELETAL muscle tissue.
-controlled by motor units -many nuclei -striations
Acetylcholine ______.
-is stored in the synaptic vesicles of the presynaptic cell at the neuromuscular junction -acts as a neurotransmitter
When a voltage gated Na+ channel opens, ______
-sodium ions move through the channel depending upon their gradient -there has been a change in the membrane potential of the cell
An action potential has two phases. The first phase is _______ and the second phase is___________
1) depolarization 2) repolarization
The capacity of a muscle to respond to an electrical stimulus is ______
excitability
Another name for a single skeletal muscle cell is a skeletal muscle______
fiber or myocyte
Enlargement of muscles in children and adults that results from an increase in the size of each muscle fiber is called______
hypertrophy
The enlargement of muscle in response to exercise is primarily due to ______
hypertrophy
A negative membrane potential indicates that the area with a more negative charge is on the ______ of the membrane.
inside
The structure within a muscle fiber that extends from one Z disk to another Z disk is a(n) ______
sarcomere
The sliding filament theory states that during contraction ______
sarcomeres shorten because actin myofilaments slide past the myosin myofilaments
The __________reticulum is a modified form of smooth endoplasmic reticulum located in muscle cells.
sarcoplasmic
In a muscle cell, the highly specialized, smooth endoplasmic reticulum is called the _________.
sarcoplasmic reticulum
Long, cylindrical, striated cells containing multiple nuclei are typical of _____ muscle tissue.
skeletal
The type of muscle that constitutes about 40% of the body's weight, is responsible for locomotion, facial expressions, posture, respiratory functions, and many other body movements is ________muscle
skeletal
What type of tissue is striated and voluntary?
skeletal muscle
Each G-actin monomer has an active site for the binding of what molecule?
Myosin
Which of the following events occur during the relaxation phase of the muscle twitch?
-Calcium ions are actively transported back into the sarcoplasmic reticulum. -The muscle fibers lengthen passively. -The troponin-tropomyosin complexes move to inhibit cross-bridge formation.
List the actions that occur during the process known as cross-bridge cycling
-Cross-bridge formation -Recovery stroke -Cross-bridge release -Power stroke
Which of the following is associated with the relaxation phase?
-Muscle tension declines. -Myosin releases thin filaments. -Calcium levels in the cytoplasm fall.
Which of the following best describes the term "propagate" in terms of the action potential?
-To move -To travel
Which of the following locations have single-unit (unitary) smooth muscle tissue?
-Urinary and reproductive tract -Walls of the esophagus
Which of the following ion channels directly generate the phenomenon known as the action potential in a motor neuron?
-Voltage gated sodium channel -Voltage gated potassium channel
Which of the following locations have multiunit smooth muscle tissue?
-Walls of blood vessels -Capsule of the spleen -Arrector pili muscles and iris of the eye
Acetylcholine released into the synaptic cleft is rapidly broken down to acetic acid and choline by ______.
-an enzyme -acetylcholinesterase
Multiple-wave summation ______.
-can occur because the relaxation of a muscle fiber is not required before a second action potential can stimulate a second contraction -occurs when the frequency of action potentials to a fiber increases causing a corresponding increase in fiber contraction -causes a sustained contraction in a muscle fiber
Both fast-twitch and slow-twitch muscle fibers can increase in _____ as a result of exercise and training
-efficiency -capacity -strength -size
The fundamental properties of smooth muscle include ______.
-exhibits a relatively constant tension -exhibits autorhythmic contractions
Muscles which have been trained have increased strength due to ______. Select all that apply
-increased blood vessels -increased connective tissue and mitochondria
The phases of the action potential include _____
1) depolarization 2) repolarization
What type of potential follows an all-or-none law?
Action potential
How many ATP molecules does aerobic respiration produce per glucose molecule?
36
What process is used during resting conditions to produce creatine phosphate?
Aerobic respiration
What is a motor unit?
All of the muscle fibers innervated by a single motor nerve fiber
True or false: Aerobic respiration does not require oxygen in order to produce ATP.
FALSE Aerobic respiration does require oxygen. In aerobic respiration, pyruvic acid is metabolized by chemical reactions within mitochondria. Two closely coupled sequences of reactions in mitochondria, called the citric acid cycle and the electron-transport chain, produce many ATP molecules. Carbon dioxide molecules are produced in the last step, oxygen atoms combine with hydrogen atoms to form water. Thus, carbon dioxide, water, and ATP are major end products of aerobic respiration.
True or false: Human muscles contain both fast-twitch and slow-twitch muscle fibers in equal amounts.
False
True or false: In order to initiate contraction, myosin heads must bind a molecule of acetylcholine (ACh)
False
True or false: Large numbers of motor units contract together as a unit in multiunit smooth muscle.
False
True or false: Smooth muscle responds in an all-or-nothing fashion to action potentials.
False
True or false: The size and capacity of muscle fibers cannot be increased by exercise and training.
False
True or false: The increased strength of a trained muscle is due only to the increase in fiber diameter.
False Increases in mitochondrial numbers, blood vessels and connective tissue all play a role in increasing strength of a myofiber.
Name the muscle fiber type that has fewer mitochondria, less myoglobin and fewer blood capillaries?
Fast glycolytic fibers
What are smaller motor units used for?
Fine motor control
What is the function of the enzyme adenylate kinase?
It transfers a phosphate group from creatine phosphate to ADP to form ATP.
What type of smooth muscle is found in blood vessels and arrector pili muscles?
Multiunit smooth muscle
What type of tension exists because the muscle and its associated connective tissues have elasticity?
Passive
Potassium and sodium ions play an important role in resting membrane potential. Which ion has the larger concentration inside the cell?
Potassium
Name the component of the neuromuscular junction that reabsorbs choline produced by actetylcholinesterase.
Presynaptic terminal
With which phase are the following associated: myosin releases thin filaments, muscle tension declines, and cytoplasmic calcium levels fall?
Relaxation
How does treppe occur?
Residual calcium in the sarcoplasm encourages treppe.
Name the muscle fibers that contract more slowly, have more mitochondria and are more fatigue resistant.
Slow twitch fibers
_______ muscle tissue is typically slow to contract and slow to relax.
Smooth
Which of the following demonstrates the graded response of whole muscle?
The force generated to lift a feather is much less than the force required to lift a 25-pound weight.
One of the consequences of treppe is the release of heat. Describe the effect that this has.
The heat released increases the activity of enzymes.
What is the effect when calcium binds to troponin?
The troponin-tropomyosin complex changes shape and exposes the myosin binding sites.
Some organs containing smooth muscle are capable of maintaining a constant contraction rhythm. How do they do this?
They contain pacemaker cells.
Identify the function of myosin kinase in smooth muscle contraction.
Transfers a phosphate group from ATP to myosin
Name the regulatory proteins in smooth muscle.
Tropomyosin and calmodulin
True or false: ATP is needed for both muscle contraction and muscle relaxation.
True
True or false: An action potential occurs in a very small area of the plasma membrane and does not affect the entire plasma membrane at one time.
True
True or false: Fast glycolytic, white fibers have fewer mitochondria, less myoglobin and fewer blood capillaries.
True
True or false: Smooth muscle tends to contract in response to being stretched
True
True or false: Some organs containing smooth muscle also have pacemaker cells.
True
Most muscle contractions are ______.
a combination of isometric and isotonic contraction
An intercalated disc can be described as ______.
a dark line observed between adjacent cardiac muscle cells
Smooth muscle responds to action potentials by ______
a slow contraction in response to a series of action potentials
Calmodulin in smooth muscle binds _____ and activates the myosin light-chain kinase.
calcium
Troponin binds to _____.
calcium
Muscle fiber fatigue results from ______.
calcium ion imbalances as ATP levels drop
During the repolarization phase of the action potential, the voltage-gated sodium ion channels are _____ while the voltage-gated potassium ion channels are ______.
closed; open
In smooth muscle, actin myofilaments are attached to ______ in the cytoplasm.
dense bodies
Z-discs of skeletal muscle are equivalent to ____ of smooth muscle fibers
dense bodies
When the membrane potential of a cell becomes more positive than its resting potential, the cell is ______
depolarized
A sub-threshold stimulus ______.
does not cause a contraction
When the Na+ voltage-gated channels open, a large number of sodium ions _____ the cell resulting in the ________ phase of the action potential.
enter; depolarization
When the voltage-gated potassium channels open, a large number of potassium ions ______ the cell, resulting in the ______ phase of the action potential.
exit, repolarization
Cell-to-cell attachments composed of branching fibers from adjacent cardiac muscle cells are called ______
intercalated disks
A concentric contraction is a form of ______ contraction.
isotonic
An eccentric contraction is a form of ______ contraction.
isotonic
A supra-maximal stimulus has the same effect as a ______ stimulus
maximal
An increase in the number of muscle fibers responding or contracting in order to increase the force produced by a muscle is referred to as _____.
motor unit recruitment
As a stimulus increases, an increasing number of motor neurons excite an increasing number of motor units. This is called ______.
multiple motor unit summation
The process of ______ occurs when the frequency of action potentials sent to a skeletal muscle fiber increases thereby causing a corresponding increase in the duration of contraction until a period of sustained contraction is reached.
multiple-wave summation
The type of smooth muscle that contracts as many independent units is _________ smooth muscle.
multiunit
The type of smooth muscle that has fewer gap junctions than other smooth muscle types, and its cells or groups of cells act as independent units is ______ smooth muscle.
multiunit
Smooth muscles found in the iris of the eye and arteries are classified as _____.
multiunit smooth
The protein found in muscle cells that stores and then releases oxygen when needed is called _____
myoglobin
The return of the _____ head to its original position after cross-bridge release is called the recovery stroke
myosin
When a cell is in the repolarizing phase of an action potential, its intracellular environment is becoming more ______ when compared with the extracellular environment.
negative
In order for the excitation-contraction coupling to occur, the production of an action potential must occur within the ______ of a muscle fiber.
sarcolemma
The age-related loss of muscle tissue is known as ______.
sarcopenia
The _________reticulum in a muscle fiber stores calcium in between contractions.
sarcoplasmic
When the body temperature drops below a certain level, the nervous system induces rapid skeletal muscle contractions called _______
shivering
Actin and myosin fibers in ________ muscle overlap to form loose bundles.
smooth
Smooth muscle exhibits a relatively constant tension that is called ______
smooth muscle tone
When the threshold of a cell has been reached, the voltage-gated _____ channels open rapidly, giving rise to the depolarization phase of the action potential.
sodium
Stimuli which get progressively _____ and produce action potentials in axons of additional motor units are called sub-maximal stimuli
stronger
A ______ is not strong enough to cause an action potential in any of the axons in a nerve and therefore it does not cause a contraction.
sub-threshold stimulus
Excitation-contraction coupling refers to ______
the actions that link the action potential of the sarcolemma to the activation of the myofilament contraction
Describe what is meant by the threshold. It is ______
the minimum voltage that must be reached in order to cause the opening of the voltage gated ion channels of the axon hillock
Excitation-contraction coupling begins with ______.
the production of an action potential in the sarcolemma
The constant tension found in smooth muscle is called smooth muscle __________
tone or tonus
The sum of active and passive tension is called ________ tension.
total
The role of the transverse tubules is to ______
transmit the signal to contract deep into the muscle fiber
The action potential moves from the sarcolemma surface deep into the myofiber via the ______
transverse or T Tubules
When an action potential propagates, it ______.
travels across the plasma membrane by stimulating the production of another action potential
Frequent stimuli can lead to more tension with each stimulus, if all of the calcium has not been recovered by the sarcoplasmic reticulum. This step-like phenomenon is called ______.
treppe
Residual calcium in the sarcoplasm can lead to ______.
treppe
During skeletal muscle contraction, calcium binds to _____
troponin
In ______ smooth muscles, large numbers of muscles contract together as a unit.
visceral
The development of action potentials involves the opening of ______-regulated ion gates.
voltage
What is the resting membrane potential of most neurons and muscle fibers?
- 70 and - 90 mV
Potassium is more abundant in which fluid compartment?
Compartment inside of the cell
Match each muscle cell type to its function.
Smooth muscle cells- involuntary contraction of the GI tract Cardiac muscle cells- involuntary contraction of the heart muscle Skeletal muscle cells- voluntary movement of bones
What is the neuromuscular junction?
It is the site where the nerve fiber innervates the muscle fiber.
Identify the function of cardiac muscle.
Provides the major force for moving blood through the circulatory system
Typically, each motor neuron innervates _____.
more than one muscle fiber
What is the synaptic cleft?
Space between the presynaptic terminal and myofiber
What is the space between the presynaptic terminal and myofiber called?
Synaptic cleft
Skeletal muscle is described as striated. What does that mean?
The tissue exhibits alternating dark and light bands.
What are the transverse (T) tubules?
They are tube-like invaginations of the sarcolemma that extend inward throughout the muscle cell.
Which of the following molecules covers the active sites on the G-Actin molecule when the muscle fiber is relaxed?
Tropomyosin
The perimysium is ______
a thick connective tissue layer around each fasciculus
A sarcomere is formed from the arrangement of _______ and myosin myofilaments.
actin
During contraction of the sarcomere, the Z disk helps hold the ______ in place.
actin myofilament
A(n) ________potential is a propagated change in the membrane potential of a cell such as a neuron.
action
Electrical signals, called _________potentials travel from the brain or spinal cord along the axons to muscle fibers and cause them to contract.
action
The extensibility of muscle ______.
allows a muscle to stretch beyond its resting length
The sodium-potassium ion pump uses active transport therefore it requires ______.
an investment of ATP
Match the characteristics with the muscle cell type.
cardiac muscle cells- Intercalated disks join cells to one another skeletal muscle cells- Are incapable of spontaneous contraction smooth muscle cells- Do not appear striated because actin and myosin are organized as loose bundles
Match the muscle tissue type to the structural characteristics the determine its function.
cardiac muscle- branched cells that are autorhythmic and respond to nervous or hormonal stimulation. smooth muscle- overlapping filiform-shaped cells with gap junctions that allow rapid communication and coordinated movement. skeletal muscle- Very long cells but do not spontaneously contract
Correctly pair the characteristics with the muscle cell type.
cardiac- Cylindrical, branched cells with a single centrally located nucleus skeletal- Long, cylindrical, non-branching cells with many peripherally located nuclei smooth- spindle-shaped cells with a single centrally located nucleus
The concentration of sodium ions is _________in the cytosol of the cell at rest than it is in the surrounding extracellular fluid.
lower
A neuron that innervates skeletal muscle fibers is called a(n) ______ neuron.
motor
_______ neurons have axons that extend to skeletal muscle fibers through nerves.
motor
Maintenance of posture, production of body heat and movement of the body are primarily the responsibility of the ______ system
muscular
Muscle fibers develop from less mature, multinucleated cells called _____
myoblasts
The actin and myosin ______ form highly ordered units called sarcomeres which are joined end to end to form the ______
myofilaments, myofibrils
The inside of a resting cell is more ______ in charge than the extracellular fluid around the cell.
negative
Typically, the resting potential of a cell is between -70 and -90 mV. This means that the inside of the cell is more __________ than its surrounding environment.
negative
The nerve fiber innervates the muscle fiber at the ______
neuromuscular junction
The charge difference across the plasma membrane in a cell at rest is called the _____ potential.
resting membrane
The charge difference across the plasma membrane of an unstimulated cell is called the ______
resting membrane potential
When examined in a longitudinal section, skeletal muscle has alternating light and dark bands producing a(n) ______ appearance
striated
At the neuromuscular junction, each presynaptic terminal contains numerous small, spherical sacs called _____, which contain acetylcholine
synaptic vesicles
Myoblast(s) are ______
the precursors of muscle fibers