PSIO 201 Exam Guide- |Questions with
100% Correct with Solutions
refractory period - ANSWER periods during which it is difficult or impossible to generate a
second AP
absolute refractory period - ANSWER immediately following inactivation of Na-channels,
membrane cannot be restimulated to produce AP
--involves resetting of Na-channels
relative refractory period - ANSWER a period during which a new AP can be produced, but
it takes a larger than normal stimulation
--involves resetting of K-channels
1. establish maximum rate of Action Potentials
2. influence the characteristics of AP propagation-forward propagation
propagation of the action potential - ANSWER 1. entry of Na+ produces a local current
--- spreads laterally to depolarize adjacent areas of membrane
2. entry of Na+ in the new region of membrane produces a local current that spreads to
adjacent areas
electronic conduction - ANSWER -local current flow that moves under the membrane but
also displaces charges on top of the membrane (causing the current to more towards the
area of initial depolarization)
-this local current diminishes over the distacne as energy dissipates
-in the axon, the ripples cause other channels to open in the nearby area
-however, conduction is slowed a bit when you have to wait for the opening channels have
to open along the whole length of the axon
velocity of propagation - ANSWER Two Factors:
1. Size (diameter of axon)
,2. 'Myelination'
size of propagation - ANSWER -bigger is faster
-resistance to current flow in axoplasm decreases as diameter increases
myelination of propagation - ANSWER -oliodendrocytes and schwann cells form insulating
layer (sheath) around axons
-it limits the amount of ions that leak across the membrane
- if the leak is limited that means the signal can travel a longer distance down the axon
saltatory conduction - ANSWER 1. Na channels at node open
2. electronic conduction
3. channels at next node open
4. electrotonic conduction
5. next node begins to activate
fast synapse - ANSWER -activate ion channels
-current flow/voltage change (ionotropic Rs)
-once ion move according to their electrochemical gradient to lead to voltage changes
pain relief - ANSWER -some metabotropic receptors are opioid receptors
- different opioid molecules (like morphine) can bind to these
receptors -when they do, they lead to hyperpolarization of the cell
-neuroins that send pain signals have opioid receptors
-if they are hyperpolarized, their membrane potential is further away from threshold
spatial summation - ANSWER -signals from many pre-synaptic neurons add up at the trigger
zone
temporal summation - ANSWER increased frequency of action potentials from one pre-
synaptic neuron
--multiple inputs from single neuron
sensory transduction - ANSWER -involves converting the stimulus into an electrical signal
-the action potential can then be interpreted by the nervous system to allow you to
perceive that stimulus
-recall that we looked at different regions of the brain that processed different types of
sensory info
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