Physiology and Action Potential Flashcards
Steps 1 and 2 of muscle fiber contraction is ____.
activation
Where do steps 1 and 2 take place?
At the neuromuscular junction
Steps 3 and 4 of muscle fiber contraction are called ___________
excitation - contraction coupling
What do steps 3 and 4 do?
link the electrical signal to contraction
Steps 1 and 2: Activation must
- must be a nervous system stimulation
- must generate action potential to sarcolemma
Steps 3 and 4: Excitation-contraction coupling is
- action potential propogated along sarcolemma
- intracellular Ca2+ levels must rise briefly
Phase 1, step 1?
Action potential (AP) arrives at axon terminal at neuromuscular junction
Phase 1, step 2?
ACh released; binds to receptors on sarcolemma
Phase 1, step 3?
Ion permeability of sarcolemma changes
Phase 1, step 4?
Local change in membrane voltage (depolarization) occurs
Phase 1, step 5?
Local depolarization (end plate) potential) ignites AP in sarcolemma
Phase 2, step 1?
AP travels across the entire sarcolemma
Phase 2, step 2?
AP travels across the entire sarcolemma
Phase 2, step 3?
SR releases Ca2+; Ca2+ binds to troponin; myosin-binding sites (active sites) on actin exposed
Phase 2, step 4?
Myosin heads bind to actin; contraction begins
The nerve cells that activate skeletal muscle fibers is called
somatic motor neurons
Somatic motor neurons reside in the brain and spinal cord, but their long threadlike extensions called ___ travel, bundled within nerves, to the muscle cells they serve to stimulate.
axons
Each axon forms several brances as it enters the muscle. Each axon nerve ending gives off several short, curling brances that collectively form an elliptical ___ ___, or end plate, with a single muscle fiber.
neuromuscular junction
What is another name for neuromuscular junction?
end plate
Integral proteins are found
In between the opening of the sarcomere’s triad
Integral proteins are responsible for the
release of calcium
What is responsible for the coupling of excitation to the contraction of skeletal muscle fibers?
Calcium ions
The sequence of events by which transmission of an action potential along the sarcolemma which then leads to the sliding of myofilaments is called
Excitation-contraction coupling
What starts the excitation-contraction coupling process?
The events at the neuromuscular junction set the stage for E-C coupling by providing excitation.
What is released at the neuromuscular junction to create excitation?
Acetylcholine
What does the Acetylcholine bind to?
Binds to receptor proteins in the sarcolemma and triggers an action potential in a muscle fiber.
