PSIO 201 5th Edition Lecture 19 Outline of Last Lecture Sarcomere Outline of Current Lecture I Excitation Contraction Coupling II Terms III Excitation IV EC Coupling V Contraction VI Relaxation Current Lecture Excitation electrical signal is transmitted from a motor neuron to the muscle fiber Excitation contraction coupling the events that connect excitation to contraction Contraction the events that cause the sarcomere and the muscle fiber to shorten Relaxation the events that cause the sarcomere and the muscle fiber to return to resting length Sequence of events 1 electrical signal transmitted from a motor neuron to a skeletal muscle fiber excitation 2 triggers release of Ca2 from SR EC coupling 3 Ca2 brings to troponin on the thin filament crossbridge forms contraction 4 Removal of Ca2 relaxation These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute A Excitation Neuromuscular Transmission Activation of skeletal muscle is voluntary Requires a signal from the central nervous system Signal results in electrical impulse Steps of Excitation 1 Action potential arrives at synaptic end bulb of motor neuron and causes opening of voltage gated Ca2 channels 2 Synaptic vessels containing the neurotransmitters ACh goes under exocytosis 3 Ach is released into the synaptic cleft and binds to Ach receptors on the sarcolemma motor end plate 4 ACh receptors open and allow Na to enter the muscle fibers generating action potential on sarcolemma 5 ACh is quickly broken down to acetate and AChE B 1 2 3 4 5 Contraction Coupling Release of Ca2 from SR AP runs along sarcolemma continues into T tubules Triggers release of Ca2 from SR Ca2 diffuses into sarcoplasm and myofibrils Ca2 bings to Toponin on thin filament Crossbridges form and tension is generated Contraction C Relaxation Sequestrations of Ca2 1 2 3 4 5 6 When AP s stop arriving at the NMJ the trigger to release Ca2 from the SR stops Active Ca2 transporters in the SR membrane pump Ca2 back into the SR Cytoplasmic Ca2 decreases Myosin binding sites get covered by tropomyosin Crossbridge cycling stops and tension drops Titin brings the sarcomere back to resting position
View Full Document
Unlocking...