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Muscle contraction will always promote movement of body parts regardless of how they are attached.
The end of the muscle that typically moves when a muscle contracts is called the ________.
The connective tissue sheaths of skeletal muscle, in order from internal to external are the:
endomysium, perimysium, and epimysium
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 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
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 giant protein titin maintains the organization of the ________ assisting in muscle stretching
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:
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
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
When a muscle is unable to respond to stimuli temporarily, it is in which of the following periods
An anaerobic metabolic pathway that results in the production of two net ATPs per glucose plus two pyruvic acid molecules is
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
Which of the following is true
Skeletal muscle fibers contain sarcomeres; smooth muscle fibers do not
Smooth muscles that act like skeletal muscles but are controlled by autonomic nerves and hormones are
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
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 movements demonstrates a first-class lever?
raising your head up off your chest
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?
If L = load, F = fulcrum, and E = effort, what type of lever system is described as LEF?
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
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?
Which of the following types of glial cells produce the myelin sheaths that insulate the neural fibers in the CNS?
Which of the following PNS neuroglia help to form myelin sheaths around larger nerve fibers in the PNS?
Neuroglia that control the chemical environment around neurons by buffering potassium and recapturing neurotransmitters are ________.
Which neuron circuit pattern is involved in the control of rhythmic activities such as breathing?
Select the correct statement about serial processing.
Spinal reflexes are an example of serial processing.
Which of the following is an excitatory neurotransmitter secreted by motor neurons innervating skeletal muscle?
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) ________.
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)?
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.
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?
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
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.
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
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?
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
The membranes of neurons at rest are very permeable to _____ but only slightly permeable to _____.
During depolarization, which gradient(s) move(s) Na+ into the cell?
both the electrical and chemical gradients
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.
Which of the following are bundles of neurofilaments important in maintaining the shape and integrity of neurons?
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 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.
A neuron that has as its primary function the job of connecting other neurons is called a(n) ________.
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 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
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.
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.
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.
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.
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