Muscle Study Questions Flashcards
What is the function of the ryanodine receptors?
to release Ca^{2+} into the cytosol from he SR in skeletal muscle cells
What happens in myosin/actin’s location during skeletal muscle contraction?
actin filaments slide past myosin filaments shorting the distance between z disks
Tetanic skeletal muscle tension is resulted from the sustained elevation of which molecule’s concentration?
Ca^{2+}
What does the pre-stimulation length of the muscle (%Lo) represent in terms of myosin/actin interaction?
Number of myosin cross bridges interacting with the actin
What are the differences between Type I (slow, red) fibers and Type II (fast, white) fibers?
Type 1 has more mitochondria, smaller diameter, more myoglobin, harder to get tired (fatigue), and lower glycolytic enzyme activity than type II
What is the primary function of gap junctions between smooth muscle cells?
They allow the neighboring smooth muscle cells to communicate electronically
What is the physiological result if the level of myosin light chain phosphorylation increases in smooth muscle?
The rate of actin-myosin cross bridge cycle increases. The maximum contraction force increases.
Which of the following structures in smooth muscle motor unit releases neurotransmitters as neuromuscular junction does in skeletal muscle?
Varicosity
What is the latch state in smooth muscle?
The cross bridge cycle is slowed down due to the myosin light chain dephosphorylation, but not completely stopped
What are the similarities between smooth muscle and skeletal muscle contraction?
They both involve voltage dependent calcium channels, ATP consumption, myosin-actin interaction and Ca^{2+} release from SR
What factors modulate smooth muscle contraction?
Autonomic nerves, circulating hormones, local signals from other cells, and electrical signals from other smooth muscle cells
Why does the force of smooth muscle in blood vessel continually increase after the optimal length?
Passive stress from other tissues continually increase
What are the sequence of events in smooth muscle cell contraction?
1) Increase in [Ca^{2+}]
2) Binding of Ca^{2+} to calmodulin
3) Activation of MLCK by Ca^{2+}/calmodulin complex
4) Phosphorylation of myosin light chain
5) Activation of myosin ATPase
what factors regulate intracellular calcium of skeletal muscle?
L-type Ca^{2+} channel, calcium pump, ryanodine Receptor, and Na/Ca exchanger
What are the differences in Skeletal, Smooth, and Cardiac muscle based on nucleus?
Skeletal muscle is multinucleate, Smooth is mono nucleated, and Cardiac is a mixture
What are the differences in skeletal, cardiac, and smooth muscle in terms of automatic phase contraction?
only smooth muscle has automatic phase contraction
What are the differences between skeletal, cardiac, and smooth muscle in terms of fatigue?
Only white fiber of skeletal muscle gets fatigue
Is skeletal muscle innervated by sympathetic nervous system?
No. Innervated by motor neurons only.
Does skeletal muscle always attach to bones?
No. Diaphragm and facial skeletal muscle are exceptions.
What type of contraction occurs when myosin head binds to the same F-actin monomer during the cross bridge cycling?
Isometric contraction
Why can airway allergies be treated with epinephrine?
Epinephrine activates B2 adrenergic receptor, which in turn activates cAMP signaling pathway, causes airway smooth muscle relaxation
Can nerve stimulation induce smooth muscle relaxation?
yes, smooth muscle innervation regulates both contraction and relaxation
In a single stimulated isotonic contraction, what changes in the shortness/time relationship curve when load is increasing?
1) latency of contraction increase
2) total shorten duration decrease
3) speed of contraction decrease
4) maximal shorten distance decrease
the following measure total body water
D2O, HTO
The following measure extracellular volume
1) Inulin
2) Mannitol
3) Radio-labeled Sodium
4) Radio-labeled sulfate
The following measure blood volume
1) Radio-labeled iron
2) Cr^51
The following measure plasma volume
1) RISA
2) T-1824 (Evan’s Blue)
