Muscle Contraction Flashcards

1
Q

What kind of receptor does skeletal muscle have?

A

Nicotinic

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2
Q

Motor nerves release ____

A

acetylcholine

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3
Q

The acetylcholine-nicotinic receptor interaction results

A

in the nicotinic receptor opening as a sodium channel

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4
Q

Skeletal muscle depolarization causes activation of __________

A

L calcium channels (dihydropyridine receptors)

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5
Q

Calcium entry into muscle releases calcium from intracellular storage sites (sarcoplasmic reticulum) via ___________

A

calcium-induced calcium release (ryanodine receptors - physically coupled, don’t actually need Ca to go into cell)

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6
Q

Elevated intracellular calcium concentrations result in _______

A

calcium binding to troponin C

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7
Q

calcium binding to troponin C

—-> ____________

A

releases inhibition of actin-myosin interactions

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8
Q

______ heads then contact ________ to create muscle shortening and force generation, provided ________ is present

A

Myosin - actin

Requires ATP

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9
Q

acetylcholinesterase

A

breaks down acetylcholine into choline and acetate to stop signal

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10
Q

______ indicate borders of sarcomere

A

Z lines indicate borders of sarcomere

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11
Q

Muscle __ band remains same size but ____ bands decrease in width

A

A band

I band

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12
Q

Power stroke occurs as a result of _______

A

Release of Phosphate after cleaving ATP –> ADP + Pi which cocked the myosin head

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13
Q

When is ADP released during muscle contraction?

A

During/because of power stroke

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14
Q

_______ allows myosin head to be released from actin

A

Binding of ATP

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15
Q

Amyotrophic lateral sclerosis

A

degeneration of motor neurons

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16
Q

Lambert-Eaton syndrome

A

antibodies against Ca channels in motor neurons resulting in inability to release Ach

17
Q

Botulism toxin

A

prevents Ach release by cleaving synaptic associated proteins (SNAPs)

18
Q

Myasthenia gravis

A

autoantibodies against nicotinic receptors in skeletal muscle

19
Q

Malignant hyperthermia

A

caused by mutation of ryanodine receptor allowing excessive release of Ca - usually triggered by anesthetics

20
Q

Duchenne’s muscular dystrophy

A

mutation in dystrophin, skeletal muscle support protein

21
Q

Pesticides and nerve gases

A

Pesticides and nerve gases are anticholinergics (acetylcholinesterase inhibitors) → overstimulation of nicotinic receptors

22
Q

Amount of force generated by muscle directly proportional ______

A

to number of actin-myosin crossbridges per cross-sectional area

Work best when considerable overlap between actin and myosin
Stretched muscle → actin/myosin no longer interacting → no strength
As shorten muscle → actin and myosin interacting, force increases linearly
Maximal point - maximal # cross bridges (no more in center)
If go past that - disordered by no more cross bridges

23
Q

Force-velocity relationship

A

Muscles contract most rapidly when there is no load on the muscle

24
Q

Isotonic contraction

A

Load on muscle is constant

25
Isometric contration
Load is larger than muscle's ability to move it (shorten tendon, but can't move bony attachment)
26
Type I muscle Fiber
Slow twitch Slower myosin ATPase enzyme High proportions in distance runners or in postural muscles (soleus) Contain lots of myoglobin → “Red Fibers” Need myoglobin because they require a lot of oxygen to maintain contractions
27
Type II muscle fiber
High proportions in extraocular muscles of eye Faster myosin ATPase White fibers (less myoglobin) Anaerobic metabolism
28
Concentric contractions
Muscle contracts resulting in shortening | Typical biceps curl in weightlifting
29
Eccentric contractions
``` Muscle lengthens while attempting to shorten Much more damage to muscle with this type of contraction Running downhill (trying to contract while stretching) ```
30
Muscle conduction to contraction
AP depolarization opens presynaptic VG Ca channels inducing NT release --> Postsynaptic ligand binding leads to muscle cell depolarization in motor end plate --> depolarization travels along muscle cell and down Ttubule --> Depolarization at Voltage-sensitive DHP receptor, mechanically coupled to ryanodine receptor on SR, induced conformational change causing Ca release from SR --> release Ca binds to troponin C causing conformational change that moves tropomyosin out of myosin-binding groove on actin filaments --> myosin releases bound ADP and Pi - displacement of myosin on actin filament (power stroke) --> binding of new ATP molecule causes detachment of myosin head from actin filament, hydrolysis of ATP to ADP + Pi cocks head
31
Contraction of muscles results in what of bands
H and I bands shorten between Z lines (HIZ shrinkage) | A band is Always same length
32
Darker regions contain ______ | Lighter regions contain ______
dark - myosin | lighter - actin
33
Motor neurons release _____
acetylcholin
34
Cardiac muscle has ___ channels, more reliant on
L channels, ca-induced-ca-release (not physically coupled)
35
Smooth muscle contraction controlled by
Ca interacting w/ calcium dependent myosin light chain kinase