II Regulation of Muscle Contraction
A. The Motor Cortex of the brain (Kenzie) releases motor impulse (Erin) down pathway leading to target muscle
B. It reaches the Synaptic Knob (Bryan) where a Neurotransmitter (Ach-Brennan) is released into the Neuromuscular Junction - the synapse between nerve and muscle
C. Ach bonds to receptor sites on the Sarcoplasmic Reticulum (SR-Holden) Membrane which surrounds and permeates muscle and also holds a resting charge. The SR will now "fire" and release Ca2+ (Carson) ions into the muscle fibers.
D. Ca2+ will now bond to Troponin (Maddie). Troponin is a smaller protein found along the length of a larger, cable-like, protein called Tropomyosin.
E. This causes the Tropomyosin cable to shift position exposing the Actin Binding Sites (Rachel) to the Myosin Heads (Bryar). RESULT: CONTRACTION.
NOTE: The regulation of Muscle Contraction (strength and duration) is directly controlled by the amount of Ca2+ that are bonded to Troponin molecules at any one time.