10 Steps Of Muscle Contraction
Question: Step 1 - Nerve Impulse reaches Neuromuscular Junction
Answer: Nerve signal from brain arrives at neuromuscular junction & axon terminal of motor neuron
Question: Step 2 - Acetylcholine (ACH) Released by Motor Neuron
Answer: Motor neuron releases neurotransmitter Acetylcholine (Ach) into synaptic gap between nerve & muscle cells
Question: Step 3 - ACH binds to Muscle Receptor Sites
Answer: ACH (key) binds to receptors on the muscle cell
Question: Step 4 - Sodium Channels in muscle OPEN
Answer: Receptors stimulated by ACH allow sodium (Na+) channels in muscle cell to open
Question: Step 5 - Na+ Ion rush causes change in cell charge
Answer: Na+ influx into muscle cell causes polarity change, creates electrical current called an Action Potential
Question: Step 6 - Action Potential charge travels down muscle cell
Answer: Action Potential impulse travels down the sarcolemma membrane and all over the muscle cell
Question: Step 7 - Release of Ca+ into cell
Answer: Action potenial impulse causes the sarcoplasmic reticulum web to release stored Ca++ into the cell and around sarcomere contraction units
Question: Step 8 - Ca+ influx causes Myosin & Actin to bind
Answer: Inside sarcomeres, Ca++ ions allow myosin heads to fit onto actin filaments
Question: Step 9- CONTRACTION
Myosin & Actin move, Sacromere shortens
Answer: Myosin heads “pull” Actin filaments toward center, allowing filaments to slide past each other in opposite directions, shortens sacromere
Question: Step 10 - RELAXATION
Answer: When action potential ends, Ca++ is reabsorbed by sacroplasmic reticulum, myosin & actin return to orginal position, and muscle relaxes