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DPT 503 > Muscle Physiology > Flashcards

Muscle Physiology Flashcards

(49 cards)

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1
Q

What is the only source of energy for contractile activities?

A

ATP

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2
Q

characteristics of muscles tissue

A

excitable: can be stimulated; able to receive stimulus and respond

contractible: able to contract and become shorter

extensible: able to lengthen

elastic: able to go back to og shape/length after being deformed

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3
Q

muscle functions

A

produce movement

maintain posture/position

stabilize joints: more active than tendons and ligaments

generate heat: when muscles contract it creates heat (glycolysis)

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4
Q

skeletal muscle anatomy

A

connective tissue sheath: epimysium, endonysium

attachment

motor fibers innervate muscle fibers

blood supplies O2 and nutrients and removes waste products

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5
Q

sarcolemma

A

around the whole fiber

muscle fiber plasma membrane

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6
Q

sarcoplasm

A

muscle fiber cytoplasm

structure for metabolism

contains:
- glycosome: storage for glycogen (energy source for muscles contraction)
- myoglobin: carry O2 in muscle
- ribosome: synthesizes protein (RNA, DNA)
- mitochondria: creates ATP which produces energy

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7
Q

myofibril

A

densely packed, rod-like elements

a single muscle fiber can contain 1000s

has myofilaments, striations, and sarcomeres

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8
Q

myosin

A

thick filaments (16 nm diameter)

motor protein in all types of muscle

globular head and myosin tail

converts chem energy (ATP) to mechanical energy (contraction)

has actin binding sites

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9
Q

actin

A

thin filament (8 nm diameter)

double helix formation

has indentation for myosin head

tropomyosin: string

troponin: at regular intervals binds to tropomyosin and actin

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10
Q

myofibril striations

A

repeating series of dark and light bands along length of myofibril

A band, H zone, M line, I band, and Z disc

myosin and actin in hexagonal arrangement with myosin filaments surrounded by 6 actin filaments

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11
Q

A band

A

dark region-dark bc of the density of myosin and actin filaments

length of thick filament (myosin)

myosin and actin

has H zone and M line

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12
Q

H zone

A

lighter area in A band w/only myosin and no thin filaments (actin)

contains M line

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13
Q

M line

A

connects myosin vertically within the H zone in the A band

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14
Q

I band

A

light region

thin filaments (actin) only

actin extends across the I band and partway into the A band

has the Z disc

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15
Q

Z disc

A

anchors actin together within the I band

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16
Q

sarcomere

A

smallest contractile unit

area b/w Z discs

align along myofibril

A band and 1/2 I band on each side

shortened muscle=less sarcomeres in series (less=can’t lengthen)

2 sarcomeres connect at the Z disc

titan filament

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17
Q

sarcomeres and muscles length

A

less sarcomeres=shorter

add sarcomeres=lengthen muscle

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18
Q

titan filament

A

acts as spring tethering myosin to Z disc

contributes to stability of myosin

doesn’t contribute to contraction of muscles but is important to MUSCLE TONE

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19
Q

contractile proteins

A

myosin and actin

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20
Q

regulatory proteins

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A

tropomyosin and troponin

21
Q

tropomyosin

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A

covers binding sites, blocks the cross bridge

22
Q

troponin

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A

holds tropomyosin in place

high affinity for calcium

23
Q

sarcoplasmic reticulum (SR)

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A

web like structure
fluid filled intracellular organelle

spans the sarcomere and wraps up the contractile myofilaments

stores and releases Ca2+ which binds to troponin, moving tropomyosin off myosin binding sites so actin is ready to bind to it

has terminal cistern (cisterna)-enlarged space where the sarcomere ends.

24
Q

T tubules

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A

vertical; overlies Z disc

continuation of sarcolemma

allows AP to reach deep into each muscle fiber

b/w terminal cistern

25
triad
2 terminal cistern and 1 T-tubule transmission of AP along T-tubules cause Ca2+ release from the SR (terminal cistern)
26
Why is Ca2+ important?
troponin has calcium binding sites and high affinity for calcium when Ca2+ binds to troponin, it moves the tropomyosin and uncovers myosin binding sites on actin so it's ready to bind
27
sliding filament theory
relaxation and contraction is caused by actin and myosin sliding past each other relaxation: filaments only overlap slightly - H zone wide in middle of A band - lighter band is wider contraction: thin filaments slide past thick filaments - myosin fits into spaces made by actin - in fully contracted muscle, everything comes together and fully overlap - no/very little I band bc actin and myosin overlap more - light region gets much shorter, dark region remains pretty unchanged - sarcomere shortens - progressive pulling of actin towards myosin
28
what triggers muscle contractions?
AP in somatic motor neurons AP arrives at axon terminal voltage-gated calcium channels open release ACh into synaptic cleft - acetylcholinesterase degrades ACh later ACH binds to receptors on sarcolemma that surrounds the fiber opens voltage-gated ion channels end plate potential (EPP) (local depolarization/excitation) triggers an AP AP propogates along sarcolemma and T-tubules voltage sensitive proteins in tubules stimulate Ca2+ release from SR Ca2+ binds to troponin, moves tropomyosin off binding sites so myosin can bind to actin
29
activation of cross-bridges
cross bridge formation: high energy myosin head with ADP and P attaches to actin power (working) stroke: myosin head pulls actin towards in at the M line - ADP and P detach from myosin cross bridge detachment: ATP attaches to myosin head, causing bridge to detach cocking of myosin head: energy from hydrolysis of ATP "cocks" myosin head into high energy state - hydrolysis of ATP-ADP and P that's ready to attach to myosin head and allow it to attach to actin and start cycle again
30
role of ATP in muscles
both contraction and relaxation
31
what does no ATP do to muscles
rigid muscles (rigor mortis)
32
relaxation phase
APs of motor neurons stop Ca2+ pumped back into SR - requires ATP (active transport) - prevents myosin cross bridge formation
33
muscle innervation
each muscle innervated by one motor nerve (bundle of motor neurons axons)
34
motor unit
one motor neuron and all muscle fibers it supplies fibers innervated are dispersed throughout muscle, so an AP would only contract those fibers (very weak contraction)
35
motor unit innervation ratio
muscle fibers per motor neuron
36
low motor unit innervation ratio
20:1 for example fine motor control finger muscles, extraocular muscles, face muscles, larynx need great amount of precision, control, and stabilization
37
high motor unit innervation ratio
2000: 1 for example gross motor controls quads, hamstrings, thigh muscles, gastrocs, etc.
38
muscle twitch
brief activation of a single motor unit w/a single action potential just 1 AP lasts only a couple hundred milliseconds VERY small force generated summation of twitches makes things functional latency period: (2 ms) contraction period (10-100 ms) -max tension relaxation period: (10-100 ms) contracts faster than relaxes
39
frequency (temporal) summation
muscle response to increases in stimulus frequency increased frequency (decreased interval b/w twitches)=twitches summate b4 motor unit completely relaxes, give another stimulus high frequency=high force
40
unfused tetanus
high tension w/ wave-like pattern (quiver) on top 20-40 Hz
41
fused tetanus
over 20-40 Hz max tension that can be generated from that motor unit no quiver, one smooth contractions
42
multiple motor unit summation
muscle response to increased stimulus strength increased strength=increased motor units recruited subthreshold stimulus: below 5 volts; not going to recruit threshold stimulus: 5 volts; start to recruit max stimulus: no more motor units to recruit high stimulus=high recruitment= high force
43
what determines which motor units are recruited 1st vs later?
size principle
44
size principle
smaller motor units recruited 1st, larger motor units recruited later w/stronger stimulus smallest, highly excitable (lower threshold) motor neurons innervate the smaller muscle fibers with small amount of force generated larger, less excitable (higher threshold) motor neurons innervate larger muscle fibers with larger amount of force generated
45
benefit of recruiting motor units asynchronously
helps reduce muscle fatigue
46
isometric muscle contraction
tension at cross bridge is equal to resistance constant muscle length exercise when holding a a position (holding a dumbbell for a few minutes)
47
isotonic muscle contraction
muscle tension remains constant concentric and eccentric contractions
48
concentric muscle contraction
tension at cross bridges is enough to overcome resistance muscle shortens: biceps shorten with bicep curls
49
eccentric muscle contraction
tension at cross bridges is less than resistance muscle lengthens: slowly lower down the dumbbell, the biceps contracts eccentrically

DPT 503 (22 decks)

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