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170 terms

test 4

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Which of the following is correctly paired?
Skeletal muscle: voluntary control
Muscle tissue does not
generate nerve impulses
Which type of muscle can contract without being stimulated by the nervous system?
cardiac
Which muscle characteristic describes the ability of muscle to respond to a stimulus
excitability
Which of the following surrounds the individual muscle cell?
endomysium
Muscle tissue has all of the following properties except ________.
secretion
Muscle contraction will always promote movement of body parts regardless of how they are attached.
false
One of the important functions of skeletal muscle contraction is production of heat.
true
The end of the muscle that typically moves when a muscle contracts is called the ________.
insertion
The connective tissue sheaths of skeletal muscle, in order from internal to external are the:
endomysium, perimysium, and epimysium
The smallest contractile unit of a muscle fiber is the
sarcomere.
Thick myofilaments are made of
myosin.
The major role of the sarcoplasmic reticulum is to regulate:
intracellular levels of Ca2
The distance between Z-discs ______ during muscle contraction
decreases
The sliding filament model of contraction states that:
during contraction, the thin filaments slide past the thick filaments so that actin and myosin filaments overlap
Which organelle contains the contractile elements found in skeletal muscle?
myofibril
Which protein inhibits skeletal muscle contraction, and what ion removes the inhibition?
Tropomyosin; calcium ions
What is the role of tropomyosin in skeletal muscles?
Tropomyosin serves as a contraction inhibitor by blocking the myosin binding sites on the actin molecules
Myoglobin
stores oxygen in muscle cells
What structure in skeletal muscle cells functions in calcium storage
sarcoplasmic reticulum
What produces the striations of a skeletal muscle cell?
the arrangement of myofilaments
The contractile units of skeletal muscles are
myofibrils
What is the functional role of the T tubules
enhance cellular communication during muscle contraction
What is the role of calcium ions in muscle contraction?
bind to regulatory sites on troponin to remove contraction inhibition
The muscle cell membrane is called the
sarcolemma
The giant protein titin maintains the organization of the ________ assisting in muscle stretching
A band
What part of the sarcolemma contains acetylcholine receptors
motor end plate
The first step toward generating a skeletal muscle contraction is:
stimulation of the muscle by a nerve ending
The response of a motor unit to a single action potential of its motor neuron is called a:
muscle twitch
Slow oxidative muscle fibers are best suited for
endurance activities.
What is a cross bridge cycle?
thick filaments pulling thin filaments toward the center of the sarcomere
Which of the following factors influence the velocity and duration of muscle contraction
load placed on the muscle
What does oxygen deficit represent?
the difference between the amount of oxygen needed for totally aerobic muscle activity and the amount actually used
Creatine phosphate functions in the muscle cell by
storing energy that will be transferred to ADP to resynthesize ATP
What controls the force of muscle contraction?
multimotor unit summation
During muscle contraction, myosin cross bridges attach to which active sites
actin filaments
Rigor mortis occurs because
no ATP is available to release attached actin and myosin molecules
During vigorous exercise, there may be insufficient oxygen available to completely break down pyruvic acid for energy. As a result, the pyruvic acid is converted to
lactic acid
When a muscle is unable to respond to stimuli temporarily, it is in which of the following periods
refractory period
In an isotonic contraction, the muscle
changes in length and moves the "load"
An anaerobic metabolic pathway that results in the production of two net ATPs per glucose plus two pyruvic acid molecules is
glycolysis
Muscle tone is
a state of sustained partial contraction
The sliding filament model of contraction involves
actin and myosin sliding past each other and partially overlapping
After nervous stimulation stops, what prevents ACh in the synaptic cleft from continuing to stimulate contraction
acetylcholinesterase destroying the ACh
Hypothetically, if a muscle were stretched to the point where thick and thin filaments no longer overlapped
no muscle tension could be generated
The calcium calmodulin system of contraction regulation is found in
smooth muscle only.
Which of the following is true
Skeletal muscle fibers contain sarcomeres; smooth muscle fibers do not
The type of muscle found in the walls of most hollow organs is
single-unit smooth muscle
Smooth muscles that act like skeletal muscles but are controlled by autonomic nerves and hormones are
multiunit muscles
Peristalsis is characteristic of smooth muscle
true
are muscles that serve as the primary promoters of a movement.
Agonists
When the term biceps, triceps, or quadriceps forms part of a muscle's name, what does it tell you about the muscle
The muscle has two, three, or four origins, respectively
A muscle group that works with and assists the action of a prime mover is a
synergist
Which generalization concerning movement by skeletal muscles is not true
During contraction the two articulating bones move equally
Which of the following is not used as a criterion for naming muscles
Whether the muscle is controlled by the involuntary or voluntary nervous system
Which of the following muscles is named for its origin and insertion?
sternocleidomastoid
Which of the following muscles is named for its action?
levator labii superioris
What is a muscle that provides the major force for producing a specific movement called?
an agonist
What are the muscles that are found at openings of the body collectively called?
circular muscles
Muscles are only able to pull, they never push.
true
Which of the following is correctly matched?
Convergent arrangement of fascicles: fan shaped muscle
Most skeletal muscles of the body act as:
third-class levers.
Which of the following movements demonstrates a first-class lever?
raising your head up off your chest
Which type of lever is demonstrated by using scissors?
a first-class lever
What is the major factor controlling how levers work?
the difference in the positioning of the effort, load, and fulcrum
If a lever operates at a mechanical disadvantage, it means that the ________.
load is far from the fulcrum and the effort is applied near the fulcrum
What type of muscle assists an agonist by causing a like movement or by stabilizing a joint over which an agonist acts?
a synergist
If L = load, F = fulcrum, and E = effort, what type of lever system is described as LEF?
third-class lever
Both first- and second-class levers operate at a mechanical disadvantage.
False
The main forearm extensor is the:
triceps brachii.
Which of the following is NOT a rotator cuff muscle?
teres major
The supraspinatus is named for its location on the posterior aspect of the scapula above the spine. What is its action?
to stabilize the shoulder joint and help prevent downward location of the humerus and to assist in abduction
The extensor carpi radialis brevis ________.
extends and abducts the wrist and is short
Which of the following types of glial cells monitor the health of neurons, and can transform into a special type of macrophage to protect endangered neurons?
Microglia
Which of the following types of glial cells produce the myelin sheaths that insulate the neural fibers in the CNS?
Oligodendrocytes
Which of the following PNS neuroglia help to form myelin sheaths around larger nerve fibers in the PNS?
Schwann cells
Which of the following is true of axons?
Each neuron has a single axon.
Ependymal cells ________.
help to circulate the cerebrospinal fluid
Neuroglia that control the chemical environment around neurons by buffering potassium and recapturing neurotransmitters are ________.
astrocytes
Schwann cells are functionally similar to ________.
oligodendrocytes
Neurons and nerve cells are different names for the same thing.
true
Which neuron circuit pattern is involved in the control of rhythmic activities such as breathing?
reverberating circuit
Select the correct statement about serial processing.
Spinal reflexes are an example of serial processing.
Which neurotransmitter(s) is/are the body's natural pain killer?
endorphins
Which of the following is an excitatory neurotransmitter secreted by motor neurons innervating skeletal muscle?
acetylcholine
What is the role of acetylcholinesterase?
destroy ACh a brief period after its release by the axon endings
The substance released at axon terminals to propagate a nervous impulse is called a(n) ________.
neurotransmitter
Which of the following is not a chemical class of neurotransmitters?
nucleic acid
Enkephalins and endorphins are peptides that act like morphine.
true
Which of the following circuit types is involved in the control of rhythmic activities such as the sleep-wake cycle, breathing, and certain motor activities (such as arm swinging when walking)?
Reverberating circuits
An impulse from one nerve cell is communicated to another nerve cell via the ________.
synapse
An inhibitory postsynaptic potential (IPSP) is associated with ________.
hyperpolarization
Which of the following will occur when an excitatory postsynaptic potential (EPSP) is being generated on the dendritic membrane?
A single type of channel will open, permitting simultaneous flow of sodium and potassium.
In a synapse, neurotransmitters are stored in vesicles located in the
presynaptic neuron
An action potential releases neurotransmitter from a neuron by opening which of the following channels
voltage-gated Ca2+ channels
Binding of a neurotransmitter to its receptors opens __________ channels on the __________ membrane.
chemically gated; postsynaptic
Binding of the neurotransmitter to its receptor causes the membrane to __________.
either depolarize or hyperpolarize
The mechanism by which the neurotransmitter is returned to a presynaptic neuron's axon terminal is specific for each neurotransmitter. Which of the following neurotransmitters is broken down by an enzyme before being returned?
acetylcholine
What type of conduction takes place in unmyelinated axons?
Continuous conduction
An action potential is self-regenerating because __________.
depolarizing currents established by the influx of Na+ flow down the axon and trigger an action potential at the next segment
Why does regeneration of the action potential occur in one direction, rather than in two directions?
The inactivation gates of voltage-gated Na+ channels close in the node, or segment, that has just fired an action potential.
What is the function of the myelin sheath?
The myelin sheath increases the speed of action potential conduction from the initial segment to the axon terminals.
What changes occur to voltage-gated Na+ and K+ channels at the peak of depolarization?
Inactivation gates of voltage-gated Na+ channels close, while activation gates of voltage-gated K+ channels open.
In which type of axon will velocity of action potential conduction be the fastest?
Myelinated axons with the largest diameter
How is an action potential propagated along an axon?
An influx of sodium ions from the current action potential depolarizes the adjacent area.
Why does the action potential only move away from the cell body?
The areas that have had the action potential are refractory to a new action potential.
The velocity of the action potential is fastest in which of the following axons?
a small myelinated axon
Where do most action potentials originate?
Initial segment
What opens first in response to a threshold stimulus?
Voltage-gated Na+ channels
What characterizes depolarization, the first phase of the action potential?
The membrane potential changes from a negative value to a positive value.
What characterizes repolarization, the second phase of the action potential?
Once the membrane depolarizes to a peak value of +30 mV, it repolarizes to its negative resting value of -70 mV.
What event triggers the generation of an action potential?
The membrane potential must depolarize from the resting voltage of -70 mV to a threshold value of -55 mV.
What is the first change to occur in response to a threshold stimulus?
Voltage-gated Na+ channels change shape, and their activation gates open.
Where in the neuron is an action potential initially generated?
axon hillock
The depolarization phase of an action potential results from the opening of which channels?
voltage-gated Na+ channels
The repolarization phase of an action potential results from __________.
the opening of voltage-gated K+ channels
Hyperpolarization results from __________.
slow closing of voltage-gated K+ channels
What is the magnitude (amplitude) of an action potential?
100 mV
Ions are unequally distributed across the plasma membrane of all cells. This ion distribution creates an electrical potential difference across the membrane. What is the name given to this potential difference?
Resting membrane potential (RMP)
Sodium and potassium ions can diffuse across the plasma membranes of all cells because of the presence of what type of channel?
Leak channels
On average, the resting membrane potential is -70 mV. What does the sign and magnitude of this value tell you?
The inside surface of the plasma is much more negatively charged than the outside surface.
The plasma membrane is much more permeable to K+ than to Na+. Why?
There are many more K+ leak channels than Na+ leak channels in the plasma membrane.
The resting membrane potential depends on two factors that influence the magnitude and direction of Na+ and K+ diffusion across the plasma membrane. Identify these two factors.
The presence of concentration gradients and leak channels
What prevents the Na+ and K+ gradients from dissipating?
Na+-K+ ATPase
The membranes of neurons at rest are very permeable to _____ but only slightly permeable to _____.
K+; Na+
During depolarization, which gradient(s) move(s) Na+ into the cell?
both the electrical and chemical gradients
What is the value for the resting membrane potential for most neurons?
-70 mV
The Na+-K+ pump actively transports both sodium and potassium ions across the membrane to compensate for their constant leakage. In which direction is each ion pumped?
Na+ is pumped out of the cell and K+ is pumped into the cell.
The concentrations of which two ions are highest outside the cell.
Na+ and Cl-
Which of the following are bundles of neurofilaments important in maintaining the shape and integrity of neurons?
Neurofibrils
Which of the following is the conducting region of the neuron?
Axon
Which of the following are gaps found along a myelin sheath?
Nodes of Ranvier
Which criteria is used to functionally classify neurons?
The direction in which the nerve impulse travels relative to the central nervous system.
Which of the following is not a functional classification of neurons?
Extraneurons
Which of the following does not factor into the rate of impulse propagation?
The number of axon collaterals extending from a truncated axon.
Which of the following is not true of an electrical synapse?
They are specialized for release and reception of chemical neurotransmitters.
Which part of the neuron is responsible for generating a nerve impulse?
axon
Bipolar neurons are commonly ________.
found in the retina of the eye
The part of a neuron that conducts impulses away from its cell body is called a(n) ________.
axon
Collections of nerve cell bodies outside the central nervous system are called ________.
ganglia
A neuron that has as its primary function the job of connecting other neurons is called a(n) ________.
association neuron
Which of the following is not one of the basic functions of the nervous system?
Neural genesis
Which of the following allows us to consciously control our skeletal muscles?
The somatic nervous system
What part of the nervous system performs information processing and integration?
central nervous system
Which of the following types of neurons carries impulses away from the CNS?
motor
Which of the choices below describes the ANS?
motor fibers that conduct nerve impulses from the CNS to smooth muscle, cardiac muscle, and glands
Which of the following describes the nervous system integrative function
analyzes sensory information, stores information, makes decisions
The term central nervous system refers to the ________.
brain and spinal cord
Efferent nerve fibers may be described as motor nerve fibers.
True
Action potential propagation in a skeletal muscle fiber ceases when acetylcholine is removed from the synaptic cleft. Which of the following mechanisms ensures a rapid and efficient removal of acetylcholine?
Acetylcholine is degraded by acetylcholinesterase.
The neuromuscular junction is a well-studied example of a chemical synapse. Which of the following statements describes a critical event that occurs at the neuromuscular junction?
Acetylcholine is released by axon terminals of the motor neuron.
Action potentials travel the length of the axons of motor neurons to the axon terminals. These motor neurons __________.
extend from the brain or spinal cord to the sarcolemma of a skeletal muscle fiber
Calcium entry into the axon terminal triggers which of the following events?
Synaptic vesicles fuse to the plasma membrane of the axon terminal and release acetylcholine.
Acetylcholine binds to its receptor in the sarcolemma and triggers __________.
the opening of ligand-gated cation channels
Sodium and potassium ions do not diffuse in equal numbers through ligand-gated cation channels. Why?
The inside surface of the sarcolemma is negatively charged compared to the outside surface. Sodium ions diffuse inward along favorable chemical and electrical gradients.
Excitation-contraction coupling is a series of events that occur after the events of the neuromuscular junction have transpired. The term excitation refers to which step in the process?
Excitation, in this case, refers to the propagation of action potentials along the sarcolemma.
Excitation of the sarcolemma is coupled or linked to the contraction of a skeletal muscle fiber. What specific event initiates the contraction?
Calcium release from the sarcoplasmic reticulum initiates the contraction.
One component of the triad is a T tubule. How does activity in the T tubule impact the other two components?
The T tubule is linked to two adjacent terminal cisternae of the sarcoplasmic reticulum by a series of proteins.
What is name given to the regularly spaced infoldings of the sarcolemma?
transverse or T tubules
A triad is one portion of a T tubule plus two adjacent terminal cisternae of the sarcoplasmic reticulum. What is the significance of this arrangement?
Action potentials propagating down the T tubule trigger the release of calcium ions by the terminal cisternae.
What is the relationship between the number of motor neurons recruited and the number of skeletal muscle fibers innervated?
Typically, hundreds of skeletal muscle fibers are innervated by a single motor neuron.
What is the role of calcium in the cross bridge cycle?
Calcium binds to troponin, altering its shape.
During contraction, what prevents actin myofilaments from sliding backward when a myosin head releases?
There are always some myosin heads attached to the actin myofilament when other myosin heads are detaching.
What, specifically, is a cross bridge?
myosin binding to actin
Which event causes cross bridge detachment?
ATP binding to the myosin head
How/when does the myosin head cock back to store energy for the next cycle?
After the myosin head detaches, energy from ATP hydrolysis is used to re-cock the myosin head.
Where in the cross bridge cycle does ATP hydrolysis occur?
during the cocking of the myosin head
What role does tropomyosin play in the cross bridge cycle?
The displacement of tropomyosin exposes the active sites of actin, allowing cross bridges to form.
BMD (2,3-butanedione 2-monoximime) inhibits myosin, such that ATP can bind to myosin but myosin is unable to hydrolyze the bound ATP. What effect would BMD have on the cross bridge cycle?
Myosin heads would remain detached, unable to cock.
How does troponin facilitate cross bridge formation?
Troponin controls the position of tropomyosin on the thin filament, enabling myosin heads to bind to the active sites on actin.