exam #2: chapter 12 Flashcards by tori livelli

3 muscle types
all muscle types:
-contraction occurs by ___ of actin and myosin filaments
-___/___ coupling relies on increases in intracellular ___

3 types: skeletal, cardiac, and smooth
-contraction occurs by sliding of actin and myosin filaments
-excitation/contraction coupling relies on increases in intracellular calcium

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skeletal muscle
-___ is the smallest contractile unit; ___ appearance
-control by ___ motor neurons

-sarcomere ; striped
-somatic

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cardiac muscle
-___ is the smallest contractile unit ; ___ in appearance
-pacemaker cells: ___ rhythmic action potentials and contractions
-regulation of __ and __ of contraction by __ motor neurons

-sarcomere ; striped
-automatic
-strength, frequency ; autonomic

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smooth muscle
-no ___ ; no ___ appearance
-control by ___ motor neurons

-sarcomeres ; striped
-autonomic

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muscle = bundle of ___
fasciculus = bundle of ___
muscle fiber or myofiber = ___ cell
myofibril = serially-repeating ___
sarcomere = ___ contractile unit of muscle cell

-fasciculi
-muscle fibers
-muscle
-sarcomeres
-smallest

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sarcolemma = __ of a muscle cell
sarcoplasm = __ of a muscle cell
sarcoplasmic reticulum (SR) = __ of a muscle cell
muscle cells are multi-__
muscle cells appear ___ due to dark and light banding pattern of ___
a single muscle cell contains many ___

-plasma membrane
-cytoplasm
-specialized endoplasmic reticulum
-nucleated
-striated ; sarcomeres
-myofibrils

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-motor unit is comprised of a ___ motor neuron and __ muscle fibers (cells) it innervates
-a typical motor neuron innervates how many muscle cells?

-single ; all of the
-100 to 1,0000

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-one muscle cell is typically innervated by how many motor neurons?
-a muscle is compromised of (many/a few/none) motor units?
-all muscle fibers in the same motor unit are of the same __

-a single motor neuron
-many
-type

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the neuromuscular junction (NMJ):
specialized synapse between the __ and the __

somatic motor neuron’s nerve terminal and the motor end plate of the skeletal muscle

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the neuromuscular junction (NMJ):
an action potential propagated by the motor neuron typically results in?

an action potential across the muscle cell membrane

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the neuromuscular junction (NMJ):
transformation of this electrical signal (in the muscle cell) into contraction of sarcomeres is called?

excitation / contraction (E/C) coupling

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organization of the sarcolemma
____ invaginate the myofibrils and are continuous with the sarcolemma

T (transverse)-tubules

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organization of the sarcoplasmic reticulum (SR)
-___ are placed closely to the T-tubules
-the SR surrounds __ as a network of interconnected __

-terminal cisternae
-myofibrils ; sarcotubules

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does Ca2+ move into or out of the muscle sarcoplasm during excitation/contraction coupling?

into

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somatic motor neuron releases ACh path: sarcolemma (step 1)
-binds to ___ ACh receptors, opens ___ channels at the ___
-___ diffuses in, producing ___ stimulus
-___ produced

-binds to nicotinic ACh receptors, opens ligand (chemically)-gated channels at the motor end plate
-Na+ diffuses in, producing depolarizing stimulus
-action potential produced

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somatic motor neuron releases ACh path: transverse tubules (step 2)
-___ conducted across transverse tubules
-action potentials open ___ ___ channels (receptor type?)

-action potentials conducted across transverse tubules
-action potentials open voltage-gated Ca2+ channels (DHPRs)

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somatic motor neuron releases ACh path: sarcoplasmic reticulum (step 3)
-___ coupling going in
-___ release channels in SR open (receptor type?)
-___ diffuses out into ___

-E/C coupling going in
-Ca2+ release channels in SR open (RyRs)
-Ca2+ diffuses out into sarcoplasm

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somatic motor neuron releases ACh path: myofibrils (step 4)
-Ca2+ binds to ___, stimulating ___

-Ca2+ binds to troponin, stimulating contraction

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sarcomere
-thin filaments = what protein?
-thick filaments = what protein?
-sarcomeres shorten during ____ with/without a change in length of their filaments = ___ model of muscle contraction

-actin
-myosin
-muscle contraction ; without
-sliding filament

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A band
-does the length change or is it defined during contraction?
-thin of thick filament?
-dark or light?
-where is it located in a sarcomere?

-defined, never changes
-thick
-dark
-center

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H band
-does the length change or is it defined during contraction?
-thin of thick filament?
-overlap?

-length changes because surrounding thin filaments push in during contraction
-thick filaments only
-no overlap

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I band
-does the length change or is it defined during contraction?
-thin of thick filament?
-overlap?
-dark or light?
-where is it located in a sarcomere?

-will change in contraction, more contraction = more narrow
-thin filaments only
-no overlap
-light
-1/2 in one sarcomere, 1/2 in the other

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Z disc
-center of individual __ band
-connects what?

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-I band
-neighboring sarcomeres, creates boundary

muscle contraction means ___ of muscle fibers (cells) that results in ___ of myofibrils which means movement of ___ closer to one another

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shortening
shortening
Z-discs

sarcomeres shorten via sliding of thin filaments under or over thick filaments? -do filaments shorten?

over -filaments do NOT shorten

-each myosin head group has a __-binding domain and a __-binding domain -myosin heads will bind ___ (thin filaments) only in the presence of __ -myosin heads exist in either a __ or __ position relative to ___ -the ___ causes the sliding of thin filaments across thick filaments

-ATP ; actin -actin ; Ca -"cocked" or "flexed" ; actin -"power stroke"

the cross-bridge cycle: 1. ___ muscle fiber, no __ present, cross bridge is not attached to __ 2. __ must be present, cross bridge binds to __ 3. __ is released causing conformational change in __, expulsion of __ leads to ___ 4. __ causes filaments to slide; __ is released 5. __ binding causes __ to detach from ___, a new __ binds to myosin head, allowing it to release from ___ 6. ___ hydrolysis: ___ of myosin head, ___ is hydrolyzed causing cross bridge to return to its original orientation -energy producing step? -step that explains rigor mortis?

the cross-bridge cycle: molecular mechanism of the sliding filament model 1. resting muscle fiber, no Ca present, cross bridge is not attached to actin 2. Ca must be present, cross bridge binds to actin 3. Pi is released causing conformational change in myosin, expulsion of Pi leads to power stroke 4. power stroke causes filaments to slide; ADP is released 5. ATP binding causes myosin to detach from actin, a new ATP binds to myosin head, allowing it to release from actin 6. ATP hydrolysis: "cocking" of myosin head, ATP is hydrolyzed causing cross bridge to return to its original orientation -energy producing step = step 6 -step that explains rigor mortis = step 4

when cross-bridges attach to actin, ___ occur and __ contract

power-strokes muscles

in relaxed muscle, the __ interaction is inhibited -___ lies in the grooves of the __ filament and blocks the association of __ with __ filaments

-myosin/actin -tropomyosin -actin -myosin with actin

__ is associated with tropomyosin -complex of how many proteins? -stimulated muscle: Ca interacts with ___ --> tropomyosin moves --> myosin associates with actin

-troponin -3 -troponin C

-muscle action potential results in the release of __ from the __ -intracellular __ binds to __, leading to a shift in the __ molecules, thus allowing for cross-bridge attachment (__/__ interactions) -multiple cross-bridge cycles (___) lead to muscle ___

-muscle action potential results in the release of Ca from the SR -intracellular Ca binds to troponin, leading to a shift in the tropomyosin molecules, thus allowing for cross-bridge attachment (myosin/actin interactions) -multiple cross-bridge cycles (power strokes) lead to muscle contraction

twitch -the __ quantum unit of a contraction -response of a muscle to a single __

-smallest -action potential

as action potential frequency increases, the muscle response is called what? (3 types)

summation unfused (incomplete) tetanus fused (complete tetanus)

successive iometric twitches -few or many cross bridges? -does Ca2+i return to baseline?

-few -yes

summation or unfused tetanus -do force and Ca2+i return to baseline between successive twitches? -more or less cross bridges form?

-no -more

fused tetanus -can individual twitches be distinguished? -what cross-bridge activation state?

-no -maximal

individual motor units respond with ___ and sometimes ___

twitches unfused tetanus

whole-muscle movements are generally smooth and sustained = ___ activation of multiple motor units

asynchronous

contraction strength increases as: -more/less motor units are recruited -number of myofibers increases/decreases -frequency of stimulation increases/decreases -myofiber thickness increases/decreases -based on length of myofibers at rest: optimal?

-more -increases -increases -increases -not too tight or too loose

concentric v.s isometric v.s eccentric contraction

concentric = gradually increasing weight and slowing until the muscle can no longer contract isometric = muscle holding steady, still doing work, weight equals force of contraction eccentric = muscle is stretched because weight is greater than force of contraction

myosin ATPases --> contraction or relaxation Ca2+ ATPases --> contraction or relaxation

contraction relaxation

how muscles make ATP: aerobic respiration = ___ phosphorylation (mitochondria) what kind of activity? anaerobic respiration = ___ and ___ to lactate what kind of activity?

aerobic = oxidative light activity or rest anaerobic = glycogenolysis, fermentation bursts of heavy activity

Ca-ATPases in skeletal muscle -PMCA and SERCA both burn ___ to move ___ out of the cytosol

ATP calcium

muscle fatigue: repeated __ of muscle fibers = __ of energy stores = muscle fatigue -increased or decreased force production -increased or reduced rate of rise of force -shorter or longer time to relax

activation, depletion decreased reduced longer

factors contributing to muscle fatigue -depletion of muscle ___ stores -___ accumulation -impaired ____ (decreased release of Ca2+ from SR)

glycogen lactic acid E/C coupling

three types of motor units: vary by -___ of contraction (type I = ___, type II =___) -___ of contraction -_____

-speed (type I=slow-twitch, type II=fast-twitch) -strength -fatigueability

SLOW (type I) -red/white fibers -slow/fast oxidative fibers -smaller/larger diameter and more/less myosin = less/more forceful contractions -experience fatigue or fatigue resistant? -high or low oxidative capacity (small/large capillary supply, few/many mitochondria and oxphos enzymes, high/low concentration of myoglobin)

-RED fibers -SLOW oxidative fibers -SMALLER diameter and LESS myosin = LESS forceful contractions - fatigue RESISTANT -HIGH oxidative capacity (LARGE capillary supply, MANY mitochondria and oxphos enzymes, HIGH concentration of myoglobin)

FAST (Type IIA) -red/white fibers -slow/fast oxidative fibers -smaller/larger diameter and more/less myosin = less/more forceful contractions -experience fatigue or fatigue resistant? -high or low oxidative capacity

-RED fibers -FAST oxidative fibers -MEDIUM diameter and MORE myosin = INTERMEDIATE forceful contractions -fatigue RESISTANT -RELATIVELY HIGH oxidative capacity

FAST (Type IIX) -red/white fibers -slow/fast glycolytic fibers -smaller/larger diameter and more/less myosin = less/more forceful contractions -experience fatigue or fatigue resistant? -high or low oxidative capacity (few/many capillaries, mitochondria, and more/less myoglobin, increased/decreased glycogen stores, increased/decreased concentration of glycolytic enzymes)

-WHITE fibers -FAST glycolytic fibers -LARGE diameter and MORE myosin = GREATEST forceful contractions -experience fatigue QUICKLY -LOW oxidative capacity (FEW capillaries, mitochondria, and LESS myoglobin, INCREASED glycogen stores, INCREASED concentration of glycolytic enzymes)

neural control of skeletal muscle: -proprioceptors in musculature = ___ apparatus and ___ tendon organs -___ interneurons -lower motor neurons = _-motoneurons and _-motoneurons -___ (pyramidal) tract = motor cortex, spinal cord -___ tract = cerebral cortex, thalamus/basal ganglia/cerebellum, brain step, spinal cord

-proprioceptors in musculature =muscle single apparatus and Golgi tendon organs -spinal interneurons -lower motor neurons = alpha-motoneurons and gamma-motoneurons -corticospinal (pyramidal) tract = motor cortex, spinal cord -extrapyramidal tract = cerebral cortex, thalamus/basal ganglia/cerebellum, brain step, spinal cord

muscle spindle apparatus = motor/sensory feedback -located on extrafusal/intrafusal muscle fibers -muscle stretch = spindle ___ = stimulation of ___ neurons -___length of muscle = ___ AP frequency

sensory -intrafusal -spindle, sensory -increased, increased

lower motor neurons = control of ____ -alpha-motoneuron = innervation of intramural/extrafusal muscle fibers -gamma-motorneurons = innervation of intramural/extrafusal muscle fibers

musculature -alpha = extrafusal -gamma = intrafusal

knee jerk reflex -what is stretched? -activates what neuron? -activates alpha or gamma motoneuron? -that motoneuron stimulates intrafusal or extrafusal muscle fibers to contract?

-spindle -sensory alpha -extrafusal

reciprocal innervation: agonist/antagonist muscles -as spindle is stretched from knee-jerk reflex, agonist muscle relaxes or contracts and antagonist muscle relaxes or contracts?

agonist contracts antagonist relaxes

double reciprocal innervation: crossed/extensor reflex 1. flexor ___ and extensor __ to withdraw foot 2. extensor __ and flexor __ to contralateral leg to support weight

1.contracts ; relaxes 2. contracts ; relaxes

exam #2: chapter 12 Flashcards

(55 cards)