Lab Exam Two: Microscopic Skeletal Muscle Flashcards by Carissa Garcia

Skeletal muscle exhibits alternating light and dark transverse bands, or […].

striations

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What is the skeletal muscle cell?

myofiber

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Epimysium:

surrounds the entire muscle and connects tendons

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Perimysium:

surrounds bundles of muscle fibers separating them into fascicles

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Endomysium:

surrounds each muscle fiber

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Sarcolemma:

Sarcoplasm:

plasma membrane of the muscle fiber

cytoplasm

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What occupies the sarcoplasm?

myofibrils
glycogen
myoglobin

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Myofibrils:

long protein that occupies the sarcoplasm

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Muscle fibers have multiple […] inside the […].

nuclei; sarcolemma

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Most muscle repair is by […].

fibrosis

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The sarcolemma has tubular infoldings called […].

T tubules

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The smooth ER is a reservoir of […] ions; which activates the […] process.

calcium; muscle contraction

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Each myofibril is a bundle of parallel protein called […].

myofilaments

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What are the three kinds of myofilaments:

thick filaments
thin filaments
elastic filaments

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Thick filaments are made of […]. Thin filaments are made of […]. Elastic filaments are made of […].

myosin; actin; titin

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Each acting has an active site that can bind to […] molecule.

myosin

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Thin filaments have a protein called […] which blocks the […] of actins and prevents […] from […] during […].

tropomyosin; active sites; myosin; binding; muscle relaxation

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What is the purpose of elastic filaments?

titin anchor thick filaments to Z disc at one end and M line at the other

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Striated muscle has dark […] alternating with lighter […].

A bands; I bands

** dArk & lIght

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A band = […] filaments

thick

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In the middle of the A band there is a lighter region known as the […] into which […] filaments do not reach.

H band; thin

Sarcomere:

functional contractile unit of the muscle fiber

When nerve connection to muscle is severed or poisoned a muscle is […]. If not restored, the muscle undergoes a shrinkage called […].

paralyzed; denervation atrophy

Muscle strength can decline […] per day.

Paralyzed muscles may atrophy to [...] of the initial size. At this point rehabilitation is [...].

1/4; impossible

Skeletal muscles are served my nerve cells called [...]

somatic motor neurons

Somatic motor neurons axons are called [...].

somatic motor fibers

Motor unit:

one nerve fiber and all the muscle fibers innervated (supplied) by it

Synapse:

point where a nerve fiber meets its target cell

The synapse target is a muscle fiber therefore the synapse is also known as [...].

NMJ-- neuromuscular junction OR motor end plate

NMJ-- What is the neurotransmitter?

acetylcholine

NMJ-- The nerve impulse causes...

synaptic vesicles of ACh to undergo exocytosis

ACh functions as a [...] and [...].

neurotransmitter and chemical messenger

List the "Excitation" steps:

1. action potential at NMJ 2. ACh is released and binds to sarcolemma receptors 3. permeability of sarcolemma changes 4. local change in voltage (depolarization) 5. End plate potential (depolarization) ignites action potential in sarcolemma

List the "Excitation-Contraction Coupling" steps:

1. action potential travels across sarcolemma 2. action potential travels along T tubules 3. sarcoplasmic reticulum releases calcium ion which binds to troponin 4. troponin-tropomyosin complex changes shape 5. actin filaments bind to myosin heads 6. CONTRACTION BEGINS

During "Relaxation" ACh dissociates from its receptor, AChE [...].

breaks it down to fragments

During "Relaxation" calcium is stored by binding to [...].

calsequestrin protein

When does rigor mortis begin?

3 to 4 hours after death * *peaks at 12 hours * *diminishes after 48/60 hrs

Why does rigor mortis occur?

1. calcium is fully released due to deteriorating SR | 2. myosin cannot unbind due to lack of ATP

What are the 2 types of contractions?

1. isometric | 2. isotonic

Isometric:

develops tension NOT movement

Isotonic:

develops tension AND muscle shortening occurs

Muscle twitch:

motor unit's response to a single action potential of its motor neuron

Temporal summation:

muscles maintain prolonged contraction back-to-back

Incomplete tetanus is contractions [...]. Complete tetanus is contractions [...].

after partial rest; with no rest detected

ATP supplies muscle fibers to:

1. move and detach cross bridges 2. pump calcium back into SR 3. pump sodium/potassium back into cell after ECC

ATP is regenerated quickly by what 3 mechanisms?

1. direct phosphorylation 2. anaerobic 3. aerobic

Direct phosphorylation is done by [...]. Anaerobic pathway forms [...] and [...].

creatine phosphate; glycolysis and lactic acid

Pathway of ATP during high-intensity exercise:

1. ATP in muscles 2. ATP from direct phosphorylation 3. anaerobic pathway

Pathway of ATP during prolonged exercise:

aerobic pathway

Smooth muscle fibers contain [...] only.

endomysium

Which nerve fibers supply smooth muscles?

autonomic nerve fibers