Nerve Physiology Notes

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Nerve Physiology Notes
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RESTING MEMBRANE POTENTIAL

• Nerve at rest or inactive
• Plasma membrane has electric voltage difference
  across membrane measured in Volts
• Membrane at rest is polarized fewer potassium
  (K) ions inside more sodium (Na) ions outside
  (less negative inside) -70 V

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ACTION POTENTIAL

• Nerve impulse is transmitted during action
  potential (30)
• Strong enough stimulation cause Na gates to open
  ? Na rush into cell causing depolarization

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• Na rushes into cell, membrane potential goes to
  0, and momentarily becomes positive
• If a strong enough depolarization occurs,
  threshold potential is reached and
  impulse is sent down axon

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• If another stimulus of same type arrives before
  effect of first stimulus wears off, additive
  effect of two (or more) stimuli is called
  summation
• Graded response stronger stimulus stronger
  response will be

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Threshold Potential
Resting Membrane Potential
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• K rush out of neuron after Na rush in, which
  repolarizes membrane back to resting potential

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• Refractory period is that time during which no
  stimulus can cause another action potential

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TYPES OF CONDUCTION

• continuous conduction unmyelinated axon
  conducts an impulse over its entire surface
• saltatory conduction myelinated axon jump
  from one node to next much faster

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SYNAPSE

• Gap between neuron
• presynaptic neuron neuron before the synapse
• postsynaptic neuron - neuron after synapse
• Nerve impulse travels from presynaptic to
  postsynaptic neuron

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• An impulse traveling down an axon of a
  presynaptic neuron reaches synaptic end bulb,
  opens Ca channels
• Ca rushes into cell causes synaptic vesicles to
  fuse with cell membrane and release their
  neurotransmitter into the synaptic cleft

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• Neurotransmitter binds with receptors on the
  postsynaptic neurons cell membrane

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NEUROTRANSMITTERS

• At least 30 50 different neurotransmitters
  identified
• Synaptic end bulbs may contain 2 or 3 different
  neurotransmitters
• Needs to be removed or will influence nerve
  indefinitely
• Some degraded by enzymes
• Some reuptake into cells

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REFLEX

• Reflex rapid, predictable, and involuntary
  responses to stimuli
• Reflex arc direct route from a sensory neuron,
  to an interneuron, to an effector