Lab Exam Two: Microscopic Skeletal Muscle Flashcards
Skeletal muscle exhibits alternating light and dark transverse bands, or […].
striations
What is the skeletal muscle cell?
myofiber
Epimysium:
surrounds the entire muscle and connects tendons
Perimysium:
surrounds bundles of muscle fibers separating them into fascicles
Endomysium:
surrounds each muscle fiber
Sarcolemma:
Sarcoplasm:
plasma membrane of the muscle fiber
cytoplasm
What occupies the sarcoplasm?
- myofibrils
- glycogen
- myoglobin
Myofibrils:
long protein that occupies the sarcoplasm
Muscle fibers have multiple […] inside the […].
nuclei; sarcolemma
Most muscle repair is by […].
fibrosis
The sarcolemma has tubular infoldings called […].
T tubules
The smooth ER is a reservoir of […] ions; which activates the […] process.
calcium; muscle contraction
Each myofibril is a bundle of parallel protein called […].
myofilaments
What are the three kinds of myofilaments:
- thick filaments
- thin filaments
- elastic filaments
Thick filaments are made of […]. Thin filaments are made of […]. Elastic filaments are made of […].
myosin; actin; titin
Each acting has an active site that can bind to […] molecule.
myosin
Thin filaments have a protein called […] which blocks the […] of actins and prevents […] from […] during […].
tropomyosin; active sites; myosin; binding; muscle relaxation
What is the purpose of elastic filaments?
titin anchor thick filaments to Z disc at one end and M line at the other
Striated muscle has dark […] alternating with lighter […].
A bands; I bands
** dArk & lIght
A band = […] filaments
thick
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.
5%
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:
- action potential at NMJ
- ACh is released and binds to sarcolemma receptors
- permeability of sarcolemma changes
- local change in voltage (depolarization)
- End plate potential (depolarization) ignites action potential in sarcolemma
List the “Excitation-Contraction Coupling” steps:
- action potential travels across sarcolemma
- action potential travels along T tubules
- sarcoplasmic reticulum releases calcium ion which binds to troponin
- troponin-tropomyosin complex changes shape
- actin filaments bind to myosin heads
- 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?
- calcium is fully released due to deteriorating SR
2. myosin cannot unbind due to lack of ATP
What are the 2 types of contractions?
- 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:
- move and detach cross bridges
- pump calcium back into SR
- pump sodium/potassium back into cell after ECC
ATP is regenerated quickly by what 3 mechanisms?
- direct phosphorylation
- anaerobic
- aerobic
Direct phosphorylation is done by […]. Anaerobic pathway forms […] and […].
creatine phosphate; glycolysis and lactic acid
Pathway of ATP during high-intensity exercise:
- ATP in muscles
- ATP from direct phosphorylation
- 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