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BIO SCI N113L Study Guide - Winter 2019, Comprehensive Final Exam Notes - Square Enix Europe, Ion, Memory


Department
Biological Sciences
Course Code
BIO SCI N113L
Professor
Lew
Study Guide
Final

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BIO SCI N113L

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Bio Sci N113L
Distinguish extracellular, intracellular, patch-clamp and optical imaging of electrical activity.
Extracellular: measures voltage change along outside of cell providing a reflection of
inside of cell
o Voltage diff b/w two recording electrodes placed outside of cell
Intracellular: measures voltage diff b/w the inside and outside of cell membrane
o One into the cell, one outside
Patch clamp: measures electrical currents through single ion channels in a membrane
o Isolate one channel
Optical imaging: direct visualization of voltage difference across the cell membrane
o Spatial and temporal resolution with voltage sensitive dye
Distinguish spontaneous activity from evoked activity.
Spontaneous activity: neuronal firing without external stimulation
Evoked activity: activity evoked by external stimulation
Identify sensory adaptation on recorded electrical activity trace.
Sensory adaptation: evoked activity can often decrease as a result of prolonged
stimulation
Start with larger CAP, then smaller, then none
Use stimulus-duration curve to determine chronaxie time and rheobase and draw implications
on neuron excitability.
Rheobase: weakest stimulus that will elicit any response from the nerve
o Lower rheobase = greater nerve excitability
Chronaxie time: stimulus duration required to elicit a response when stimulated at 2x
rheobase
o Lower chronaxie time = greater nerve excitability
If nerve is more excitable, curve shifts to the left
Identify factors which contribute to neuron excitability.
Strength
Duration
Fiber recruitment: increasing amp or duration increases number of fibers activated
o Starts with the largest diameter axons since have the lowest internal resistance
o End of the CAP have slow fiber (small diameter, high threshold)
Describe mechanisms underlying absolute vs. relative refractory period.
Absolute refractory period: no amount of stimulation can trigger an AP
o Due to inactivation of voltage gated Na channels which makes AP unidirectional
Relative refractory period: a second AP can be generated with greater stimulation (or
produces a lower amplitude AP)
o After a single AP, voltage gated Na channels recover at slightly different times so
when some channels have recovered, they can be opened again with greater
stimulus intensity
o CAP is decreased on the second one
Compare and contrast single action potential from compound action potential.
CAP: sum of multiple single action potentials firing simultaneously
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o Can increase in size with increasing stimulus strength or duration
o Graded
o Always A-B so if recording electrodes are switched, then cap will look go the
opposite way
o Only observe half a CAP if only one electrode
AP: one singular
o All or nothing
Identify a stimulus artifact in a trace of electrical activity.
Stimulus artifact: echo of original stimulus and not related to neural response
o Some of the electrical current from stimulating pulse is conducted passively
down the leg
Explain how salutatory conduction uses both active and passive conduction and how channels
are involved.
3 types of conduction: electrotonic, active, saltatory
Passive: electrotonic; passive spread of membrane potentials through the cell
o Decay over time and distance as current gradually leaks out of the cell
o No channels opening or AP
o Kick a soccer ball and it slowly rolls
Active: maintenance and rejuvenation of membrane potential
o AP propagation in unmyelinated regions of axons due to voltage gated channels
o Drippling soccer ballconstantly gets a little boost at each section
Active at node of Ranvier, then passive down myelinated area, then active again at node
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