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79 Cards in this Set
- Front
- Back
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A single somatic motor neuron and all of the muscle fibers it stimulates
is known as a _________. |
motor unit
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The synaptic end bulbs of somatic motor neurons contain synaptic
vesicles filled with the neurotransmitter ___________. |
acetylcholine
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T or F:
The ability of muscle cells to respond to stimuli and produce electrical signals is known as excitability. |
true
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The sequence of events resulting in skeletal muscle contraction are
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(a) generation of a nerve impulse;
(b) release of the neurotransmitter acetylcholine; (c) generation of a muscle action potential; (d) release of calcium ions from the sarcoplasmic reticulum; (e) calcium ion binding to troponin; (f) power stroke with actin and myosin binding and release. |
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In muscle physiology, the latent period refers to
(a) the period of lost excitability that occurs when two stimuli are applied immediately one after the other. (b) the brief contraction of a motor unit. (c) the period of elevated oxygen use after exercise. (d) an inability of a muscle to contract forcefully after prolonged activity. (e) a brief delay that occurs between application of a stimulus and the beginning of contraction. |
(e) a brief delay that occurs between application of a stimulus and
the beginning of contraction. |
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Which of the following muscle proteins and their descriptions are
mismatched? (a) titin: regulatory protein that holds troponin in place (b) myosin: contractile motor protein (c) tropomyosin: regulatory protein that blocks myosin-binding sites (d) actin: contractile protein that contains myosin-binding sites (e) calsequestrin: calcium-binding protein |
(a) titin: regulatory protein that holds troponin in place
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During muscle contraction all of the following occur except
(a) cross-bridges are formed when the energized myosin head attaches to actin’s myosin-binding site. (b) ATP undergoes hydrolysis. (c) the thick filaments slide inward toward the M line. (d) calcium concentration in the cytosol increases. (e) the Z discs are drawn toward each other. |
(c) the thick filaments slide inward toward the M line.
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Which of the following is not true concerning sarcomeres (before
contraction begins) and muscle fiber length–tension relationships? (a) If sarcomeres are stretched, the tension in the fiber decreases. (b) If a muscle cell is stretched so that there is no overlap of the filaments, no tension is generated. (c) Extremely compressed sarcomeres result in less muscle tension. (d) Maximum tension occurs when the zone of overlap between a thick and thin filament extends from the edge of the H zone to one end of a thick filament. (e) If sarcomeres shorten, the tension in them increases. |
(e) If sarcomeres shorten, the tension in them increases.
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Which of the following are sources of ATP for muscle contraction?
(1) creatine phosphate, (2) glycolysis, (3) anaerobic cellular respiration, (4) aerobic cellular respiration, (5) acetylcholine. (a) 1, 2, and 3 (b) 2, 3, and 4 (c) 2, 3, and 5 (d) 1, 2, 3, and 4 (e) 2, 3, 4, and 5 |
(d) 1, 2, 3, and 4
creatine phosphate glycolysis aerobic cellular respiration anaerobic cellular repiration |
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What would happen if ATP were suddenly unavailable after the
sarcomere had begun to shorten? (a) Nothing. The contraction would proceed normally. (b) The myosin heads would be unable to detach from actin. (c) Troponin would bind with the myosin heads. (d) Actin and myosin filaments would separate completely and be unable to recombine. (e) The myosin heads would detach completely from actin. |
b) The myosin heads would be unable to detach from actin.
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neuromuscular junction
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synapse between a motor
neuron and a muscle fiber |
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myoglobin
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oxygen-binding protein found
only in muscle fibers |
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satellite cells
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myoblasts that persist in mature
skeletal muscle |
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sarcoplasmic
reticulum |
Ca2-storing tubular system
similar to smooth endoplasmic reticulum |
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muscle fatigue
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inability of a muscle to maintain
its strength of contraction or tension during prolonged activity |
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twitch
contraction |
a brief contraction of all the
muscle fibers in a motor unit of a muscle in response to a single action potential in its motor neuron |
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fused (complete)
tetanus |
sustained contraction of a muscle,
with no relaxation between stimuli |
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wave summation
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larger contractions resulting from
stimuli arriving at different times |
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motor unit
recruitment |
process of increasing the number
of activated motor units |
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concentric isotonic contraction
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contraction in which the muscle
shortens |
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unfused (incomplete) tetanus
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sustained, but wavering contraction
with partial relaxation between stimuli |
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muscle tone
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produced by the continual
involuntary activation of a small number of skeletal muscle motor units; results in firmness in skeletal muscle |
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isometric contraction
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contraction in which muscle tension
is generated without shortening of the muscle |
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eccentric isotonic contraction
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contraction in which a muscle lengthens
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Weight lifter Jamal has been practicing many hours a day, and his
muscles have gotten noticeably bigger. He tells you that his muscle cells are “multiplying like crazy and making him get stronger and stronger.” Do you believe his explanation? Why or why not? |
-hypertrophy
-increasing number of myofibrils -increasing number of thick and thin filaments -no increasing number of muscle cells (stops after birth) |
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slow oxidative fibers
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-small diameter
-least powerful contraction -high in myoglobin, mitochondria, blood capillaries -dark colour -aerobic cellular respiration -slow contraction -low fatigability -high endurance |
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Fast oxidative glycolytic fibers
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-intermediate diameter
-high in myoglobin, mitochondria -medium amount of blood capillaries - aerobic & anaerobic -fast contraction -intermediate fatigability -high source of glycogen (ATP by glucose) |
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fast glycolytic
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-large diameter
-most powerful contraction -low in myoglobin, mitochondria, blood capillaries - ATP from anaerobic -fast contraction -high fatigability -large source of glycogen -aerobic mov't, short duration |
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force produced in muscle is greatest when....
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-increase of # motor units recruited
-increase frequency of stimulation -optimal overlap bw actin & myosin |
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factors regulating muscle force
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-length (length-tension relationship)
-stimulation of frequency -# of muscle fibers recruited |
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hypertrophy
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-increase number of myofibrils, thick&thin filaments.
-overall increases muscle mass -NOT increase # of muscle fibers, increase size |
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neuron functions
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1) sensory (afferent) neurons
2) interneurons (integration) 3) motor (efferent) neurons |
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neuron structure/classification
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1)multipolar
2)bipolar 3) unipolar |
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neuron vs neuroglia
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neuron: info transfer
neuroglia: support, nurture, protects neurons etc. |
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types of neuroglia cells in CNS
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1) oligodendrocytes
2)ependymal 3) microglial 4) astrocytes |
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astrocytes
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-star shaped
-structural support to neurons -maintain blood brain barrier - development (help guide neurons to appropriate targets) |
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microglial
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-part of immune system
-type of phagocytes -cleans up cellular debris, waste products - active after injury, infection, disease |
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ependymal
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-produces cerebrospinal fluid in ventral
-circulation of CSF |
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oligodendrocytes
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-myelin wrapping around axons in CNS
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Multipolar neurons
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-several dendrites
-one axon - Most neurons in CNS -all motor neurons |
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bipolar neurons
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-one main dendrite
- one axon - found in the retina of the eye, the inner ear, and the olfactory in the brain |
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unipolar neurons
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- dendrites and one axon that are fused together to form a continuous process that emerges from the
cell body -sensory receptors |
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neuroglia in PNS
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1) schwann cells
2) satellite cells |
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neuroglia cells that produce myelin
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1) oligodendrocytes (CNS)
2) schwann cells (PNS) |
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oligodendrocytes vs schwann cell
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oligodendrocytes (CNS):
-multiple wrapping of myelin for multiple cells schwann cells (PNS): -one wrapping for one cell |
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white matter
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myelinated axons
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gray matter
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cell bodies, dendrites,
and axon terminals of neurons, unmyelinated axons, and neuroglia |
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graded potential vs action potential
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GP: short distance communication
AP: communication over longer distance within the body |
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leak channel
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- Found in nearly all cells, including dendrites, cell
bodies, and axons of all types of neurons. - channels randomly open |
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ligand-gated channels
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-open in response to binding
- found in dendrites of some sensory, inter-, motor neurons |
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mechanically-gated channels
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-open in response to mechanical stimulus (touch, pressure etc)
-dendrites of some sensory neurons (touch, pressure receptors etc.) |
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voltage-gated channels
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-open in response to voltage stimulus (change in membrane potential)
-found in axons of all types of neurons |
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graded potential
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-small and local change in membrane potential
- size of GP related to size of stimulus |
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electrochemical gradient
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3 Na out vs 2 K in
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concentration gradient
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-more Na outside of cell
-more K inside of cell |
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all or nothing phenomenon
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if a stimulus is strong enough to generate an action potential,
the impulse generated is of a constant size |
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what happens in depolarization
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-Na channels open
- membrane polarizes from -70mV to +30mV |
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what happens in repolarization
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- Na channels close
- K channels open - membrane repolarizes from +30mV to -70mV |
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absolute refractory period
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another stimulus can not be generated
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relative refractory period
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a stimulus can be generated (larger than normal stimulus)
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saltatory conduction
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the impulse “leaps”
from one node of Ranvier to the next along a myelinated axon |
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how does size of diameter relate to speed of conducting an impulse?
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larger diameter means low resistance --> conducts higher speed impulse
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hyperpolarization
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K channels remain open and membrane potential decreases from -70mV to -90mV
- ion channels reset then go back to resting potention (-70mV) |
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classification of nerve fibers
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1) A fibers
-5 to 20um - myelinated 2) B fibers - 2 to 3um - myelinated 3) C fibers - 0.5 to 1.5 um -unmyelinated |
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excitatory neurotransmitter
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depolarizes postsynaptic neuron's membrane
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inhibitory neurotransmitter
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hyperpolarizes postsynaptic neuron's membrane
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ways to remove NT
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1) enzymes
2) reuptake 3) diffusion |
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parts of synapses
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1) axon terminal of presynaptic neuron
2) synaptic cleft 3)membrane of post synaptic cell (dendrites or motor end plate) |
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events of synapse
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1) nerve impulse in presynaptic neuron
2) Ca channels open (depolarization) 3) increase in [Ca], exocytosis of vesicles, merge w/plasma membrane, NT release in synaptic cleft 4)NT diffuse across synaptic cleft 5) NT bind to NT receptors 6) ions flow through channels creating post synaptic potential 7) depolarizing in postsynaptic neuron; reaches threshold; triggers AP in axon |
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Cholinergic receptor for....
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acetylcholine
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glutaminergic receptor for
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glutamate
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GABA-ergic receptor for...
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GABA
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acetylcholine functions
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-excitatory NT (acts on skeletal mm)
- opens ligand-gated ion channels -AChE breaks it down |
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glutamate functions
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- major excitatory NT in CNS
-opens ligand-gated Ca channel -removed by reuptake -causes depolarization - excitatory post synaptic potential |
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EPSP
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excitatory post synaptic potential
(depolarization;graded potential) |
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GABA (gamma aminobutyric acid) functions
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- major inhibitory NT in CNS
- causes hypepolarization (IPSP) - opens ligand-gated Cl channels -removed by reuptake |
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IPSP
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inhibitory post synaptic potential
(hyperpolarization; graded potential) |
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agonist
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substance that activates receptor (mimics NT)
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antagonist
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substance that inhibits receptor
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