3. Neurophys Flashcards
Monosynaptic/myotatic Stretch Reflex
Tap Tendon–>stretch quad–>receptor potential–> AP in sensory neuron–>synapse with alpha motor neuron in spinal cord–>NMJ–>endplate potential–> muscle contraction
Ohm’s Law
V=IR
conductance(G)
1/R
Capacitor
2 conductors with very thin insulator between
Resting Membrane Potential and what ion is it due to?
-70mV due to K+
Nernst equation
Eion=61log[ion]o/[ion]i
What is GHK equation essentially?
Nernst taking into account the permeability and concentrations of the various ions
Steps of Action Potential(very general)
- -70mV at rest/permeable to K+
- stimuli leads to increased Na permeability and depolarization
- repolarization as Na channels close
- hyperpolarization because K+ channels are delayed in opening
Action Potentials v Graded Potentials
Action-active, all or nothing response once threshold has been met
Graded-passive response proportional to amplitude of stimulus; ex. receptor and synaptic potentials
Threshold (in terms of ionic current)
balance between inward Na and outward K
3 functional states of channels
closed, open, inactivated
Relative vs Absolute Refractory Period
Relative requires larger stimulus for AP(bc inc K permeability)
Absolute-no stimulus can cause AP(too many inactive Na channels)
Depolarization
increased activation of Na channels, inward Na current, depolarization causes positive feedback (K causes basically the opposite)
how to increase conduction velocity
increase diameter of axon (less charge lost thru membrane)
myelination(decreased capacitance=more charge reaches Node of Ranvier)
Difference in how AP propogates along myelinated vs unmyelinated axon
Unmyelinated-conduction velocity proportional to axon diameter; slower than myelinated
Myelinated-increased resistance and decreased capacitance=Ricky Bobby
