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Ch11 Musclar tissue2
Nerve–Muscle Relationship
Question | Answer |
---|---|
acetylcholinesterase(AChE) | breaks down ACh and limits the duration of contraction |
polarized | in an unstimulated (resting) cell, where more anions (negative ions) are found on the inside of the plasma membrane than on the outside; the membrane is therefore polarized, or charged. |
depolarization | cations override the negative charges in the ICF, and the inside of the membrane briefly becomes positive |
repolarization. | Na+ gates close & K+ gates open; K+ rushes out of the cell, results in the loss of positive K+ ions, turning the inside of the membrane negative again. |
Excitation | is the process in which action potentials in the nerve fiber lead to action potentials in the muscle fiber; it can be divided into 5 steps. |
Excitation–contraction coupling | refers to the events that link the action potentials on the sarcolemma to activation of the myofilaments; this process has 4 steps that follow from excitation. |
Contraction | is the step in which the muscle fiber develops tension & may shorten. Also known as the sliding filament theory. The process can be divided into 4 steps that follow excitation–contraction coupling |
Relaxation | When stimulation ceases, a muscle fiber relaxes & returns to it resting length; the process can be divided into 5 steps that follow the contraction phase. |
End-plate potential (EPP) | When the gates are opened, Na+ diffuses into the cell and K+ diffuses out; the sarcolemma reverses polarity from –90 mV to +75 mV, then falls back again as K+ diffuses out. |
power stroke | Myosin releases the ADP and phosphate and flexes into a bent, low energy shape, tugging the thin filament along with it |
Myosin ATPase | hydrolyzes ATP that is bound to the myosin head; the energy released activates the head by changing its shape into a “cocked” position |
recovery stroke | Upon binding to another ATP, myosin releases the actin; it is now prepared to repeat the process by hydrolyzing the ATP & recocking |
Active transport pumps | Located in the SR pump Ca2+ from the cytosol back into the cisternae.(Is why ATP is needed for muscle relaxation & contraction. |