Synaptic Transmission & Excit. Contraction Coupling Flashcards
At a synaptic transmission, it can be ________ or _________.
Electrical
Chemical
This type of synaptic transmission is not common in mammals. The best example is between cardiac myocytes using gap junctions.
Electrical
This type of synaptic transmission utilizes a neurotransmitter diffusing across the synaptic clefts and binding to a receptor.
Chemical
At the NMJ, the chemical is ACh. The presynaptic axon can innervate as few as 1 or many muscles, and the postsynaptic cell (muscle) receives signals from (ONE/MANY) presynaptic axon(s).
One
Action potential travels form the spinal cord via myelinated motor neuron axons to synapse on one or more muscle fibers. There is one synapse per fiber, and the specialized synaptic region is called the…
Motor end plate
Put the following steps in order:
A. ACh causes opening of Na+ channels.
B. AP travels to motor end plate causing Ca2+ channels to open.
C. Entry of Na+ causes depolarization and generation of an AP.
D. Entry of Ca2+ causes ACh vesicles to release contents into synaptic clefts.
1) B
2) D
3) A
4) C
Put the following steps of the sliding filament theory of contraction in order:
A. Causes troponin to influence tropomyosin to expose binding sites.
B. Myosin heads bind actin, pull the two actin molecules, release the site, bind to the next site and pull again.
C. Skeletal muscle cell stimulated at NMJ.
D. Causes release of Ca2+ from SR.
E. AP spreads over surface and into T tubules.
F. Process continues until skeletal muscle is no longer being stimulated at the NMJ.
1) C
2) E
3) D
4) A
5) B
6) F
Put the following steps in order:
A. Ryanodine receptors cause Ca2+ channels of SR to open.
B. Ca2+/Troponin complex causes tropomyosin to pull of of binding sites of actin.
C. In skeletal muscle, AP causes DHP receptors to physically alter the state of the underlying Ryanodine Receptors, causing the Ca2+ channel (in SR) to open.
D. Ca2+ diffuses to troponin component of actin.
E. Skeletal muscle stimulated at NMJ.
F. Action potential spreads over surface and into T tubules.
1) E
2) F
3) C
4) A
5) D
6) B
This is a long molecule which helps align actin.
Nebulin
This is a large, long, elastic protein associated with myosin and anchors it within the sarcomere. It also acts to return a stretched sarcomere to its resting length.
Titin
This is a huge protein that connects the muscle cell cytoskeleton including actin to the ECM.
Dystrophin
What sequesters Ca2+ back into the SR?
SERCA
Put the following steps in order:
A. The Pi is released causing the myosin head to pull the actin past it.
B. The ATP is hydrolyzed to ADP and Pi causing the myosin head to re-cock.
C. The cycle continues until Ca2+ is re-sequestered into the SR (via SERCA).
D. Myosin, which has ADP and Pi attached to it, binds to the actin site.
E. The remaining ADP is released and replaced with an ATP, causing the myosin head to unbind from the actin.
1) D
2) A
3) E
4) B
5) C
For _________, at the termination of the AP the SR begins re-sequestering the Ca2+ via a Ca2+/ATPase Pump (SERCA). Removal of Ca2+ causes binding sites to again be covered and myosin is no longer able to complete its cycle of pulling the actin.
Relaxation
This type of fatigue is when a contraction requires the availability of ATP. Stored sources mainly as phosphocreatine.
Peripheral fatigue
