Muscular System 2 Flashcards
What is the function sarcoplasmic reticulum?
Interconnecting bundles of tubes that surround each myofibril, stores and regulate the release of calcium during muscle stimulation
What is Transverse Tubules (T-tubules)?
Extensions of the sarcolemma that provide channels from the surface of the cell towards the center of muscle fibers
What four events must occur during muscle contraction?
Nerve stimulation, AP generation in sarcolemma, AP propagation across sarcolemma, increase in intracellular Ca+2 concentration
How are skeletal muscles stimulated?
By somatic motor neurons
What happens when a nerve is stimulated?
An action potential travels across the axon from the axon hillock toward the ends of the axons called axon terminals which connect to single muscle fibers at the synapse or Neuromuscular Junction
What is the Neuromuscular Junction?
Small-gaped communication junction between the neuron & skeletal muscle
What 2 events happen in the Neuromuscular Junction?
Nerve impulses arrive at the synaptic end bulb stimulating the opening of calcium-voltage gated channels which cause synaptic vesicles to release acetylcholine across the synaptic cleft, which binds to the receptors of sarcolemma and stimulate the opening of sodium channels and generate AP in the sarcolemma
What 2 events happen in the excitation-contraction coupling?
As AP propagates across sarcolemma, to T-tubules to SR generate the release of calcium which binds to troponin which triggers the removal of tropomyosin and subsequent cross-bridge formation
When does muscle relaxation occur?
When nerve impulses cease
What actions occur when the muscle relaxes?
Sodium channels in SR close, and calcium is pumped by ATP back to SR, and the absence of calcium break the cross-bridge formations
How are innervations of muscles controlled?
Each nerve motor neuron stimulates at least one muscle fiber
What happens when more muscle fiber stimulation is required?
More motor units are activated
Explain the role of ATP in Myosin binding?
Myosin heads hydrolyze ATP into P & ADP, which gives them energy to form cross-bridge and power stroke actin towards center releasing ATP, and then ATP binding on myosin causes detachment and provides power boost
What are the three needs of ATP?
ATP generates the sliding mechanism, pumps calcium back into SR during resting, and regulates RMP through sodium-potassium pumps
