Neuromuscular Junction and Sliding Filament Theory: The Process of Muscle Contraction, Slides of Neuroscience

Download Neuromuscular Junction and Sliding Filament Theory: The Process of Muscle Contraction and more Slides Neuroscience in PDF only on Docsity! Steps of the Neuromuscular Junction & Sliding Filament Theory 1. Motor neuron sends nerve impulse to axonal terminals 2. A chemical neurotransmitter, Acetylcholine (Ach), is released and diffuses across the synaptic cleft and attaches to receptors located on the sarcolemma 3. When Ach levels are high enough, the sarcolemma becomes temporarily more permeable to Sodium (Na+) ions which rush into the muscle cell, and Potassium (K+) diffuses out of the muscle cell. 4. The increased levels of positive ions inside the muscle cell causes depolarization, and generates an electrical current called an Action Potential. Once begun, the action potential is unstoppable, and it travels over the entire surface of the sarcolemma and down the t-tubule. 5. The sarcoplasmic reticulum (SR) then releases stored Calcium (Ca++) ions into the sarcoplasm. 6. Ca++ binds to proteins (Troponin and Tropomyosin) on actin filaments causing it to change their shape and position from a blocked to an unblocked position. 7. Myosin heads attach to the newly exposed binding sites on actin and pulls actin filaments toward the center of the sarcomere. (ATP provides energy for the myosin heads to simultaneously release and bind to actin). 8. Muscle contraction occurs 9. Potassium (K+) ions diffuse in of the muscle cell fiber (cell) and it returns to its resting state. (Sodium-Potassium pump is activated to move Na++ out of the cell, and K+ back into the cell.) 10. Calcium (Ca+) is reabsorbed into the sarcoplasmic reticulum, causing the myosin heads to be blocked from actin, releasing its hold causing the muscle cell to relax and lengthen.