Neuromuscular Physiology PDF

Neuromuscular Physiology Neuromuscular physiology - talks about the nerve and muscles of the human body. Two topics Neuro- Nerve Physiology Muscular- Muscle Physiology Membrane and Action Potential Membrane Potential It is a result of concentration difference of ions across a selectively...

Neuromuscular Physiology Neuromuscular physiology - talks about the nerve and muscles of the human body. Two topics Neuro- Nerve Physiology Muscular- Muscle Physiology Membrane and Action Potential Membrane Potential It is a result of concentration difference of ions across a selectively permeable membrane that is caused by diffusion (difference of concentration on ions) Action Potential This are rapid changes in the membrane potential that spread rapidly along the nerve fiber membrane. It begins with a sudden change from the normal resting negative membrane potential to a positive potential and ends vice versa Resting membrane Potential RMP (Resting Membrane Potential) Small= -70mV Large= -90mV Phases of Action Potential Sodium comes inside Resting Stage (Polarization) the cell and then if it Before the action potential begins is too much Potassium leaves the Depolarization Rise of potential in the positive direction cell caused by SODIUM inflow Repolarization Re-establishment of the normal negative membrane potential (RMP) Hyperpolarization (cell becomes too positive) An overshoot of the RMP toward negativity Voltage Gated Na and K Channels Necessary actors in causing depolarization and repolarization NA Channels K Channels Activation: Activation: When the membrane Gate of the potassium potential becomes less channel is closed and negative, it activates the potassium ions are activation gate causing prevented from passing sodium ions to pour inward through Inactivation: Inactivation: The same stimuli for When the membrane activation also closes the potential becomes less inactivation gate. negative causing opening of However, closes a few the gate to allow potassium 10,000ths of a second diffusion. However, it after the activation gate happens with a delay - Initiation of AP Threshold: -65mV - Required sudden rise is 15-30mV Any initial rise in the membrane potential will lead to a positive feedback cycle that would open the sodium channel Ex. Rising voltage in MP causes more Na channels to open Propagation of AP An action potential elicited at any one point on an excitable membrane usually excites adjacent(neighboring) portions of the membrane Action potential propagates in all directions All-or-None Principle The depolarization process travels over the entire membrane if the conditions are right, but it does not travel at all if conditions are not right Allows the spread of depolarization (except if there is an abnormal condition) Plateau The potential remains near the peak of the potential for many milliseconds before repolarization Causes: - Calcium (slow) channels- slow opening allows for prolonged depolarization - Potassium channels- slow activation leads to delayed depolarization Nerve Neuron Dendrites Receives signals from other Dendrites Axon Propagates signals or Action Potential Myelin Sheath Facilitates a faster a conduction of Action Potential Axon Terminals Nerve Fibers # Myelinated Fibers Unmyelinated Fibers Has Myelin Sheath— Has no Myelin Sheath electric insulator Has no Node of Ranvier Has Node of Ranvier — Seen in small fibers uninsulated area Conduction velocity: bet ween sheaths 0.25m/sec Seen in large fibers Conduction velocity: 100 m/sec Myelinated Nerve Fiber: Unmyelinated Nerve Fiber Alpha Nerve Fibers Delta Nerve Fiber Beta Nerve Fibers Gama Nerve Fibers