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Lecture 8

Lecture 8 - Action Potentials

5 Pages
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Department
Biological Sciences
Course Code
BIOC32H3
Professor
Kenneth Welch

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Lecture 8
Action Potentials
Frog Muscle Cell
The Goldman Equation: forces dictating electrical and concentration gradients
Leak Channels: resting cells; permeable to K+ and open at rest
Perturb the system:
oPuncturing the cell
oApplying a current across the electrodes to drive the _____
oPositive current moving into the cell and we can see the effect of this current
by the use of recording equipment
Excitable cells:
Hyperpolarized: already polarized and make it more polarized by moving it away
from 0
Accommodation: when a neuron is subjected to subthreshold stimuli of slowly
increasing intensity, the threshold potential increases; determines how individual
neurons respond to input whether they are continuously active or produce only
bursts of APs
oSome neurons accommodate rapidly and generate only one or two APs at the
beginning of the stimulus period = phasic response
oOther neurons accommodate more slowly and fire repeatedly, although with
gradually deceasing frequency, in response to a prolonged constant stimulus
have a = tonic response
The difference among neurons plays a key role in how sensory neurons transmit
information
www.notesolution.com
Reduction in the frequency of APs that is typically seen in a neuron that responds
tonically during a sustained stimulus
The intracellular AP
All or none: a stimulus that is just shy of the threshold
Compound AP: FIELD potential in one section of a nerve not over the entire
oAll of the electrical activity of the variety of axons that make up the entire
nerve
oIntensity
omax stimulation will be reached recruiting ALL the axons available (even if
you stimulate more, wont recruit any more)
essentially spatial recruitment
The Hodgkin Cycle
oPassive movement of Na+ making it more positive, depolarization, MORE
Na+ open = POSITIVE FEEDBACK
Rare for positive feedback because it moves it away from homeostasis
(while negative feedback keeps it at a balanced-ish level)
APs: the result of voltage-gated ion channel activity
oGraph on the lower part doesnt show direction of the current but the
conductance
The magnitude of the current peaks later than the _____
Na/K pump not responsible for cause repolarization:
oEven though it is pumping ions in and out and contributing to the negative
membrane potential (net negative charges in the inside of cell)
oYou can poison the pump and still get APs after poisoning has occurred
www.notesolution.com

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Description
Lecture 8 Action Potentials Frog Muscle Cell The Goldman Equation: forces dictating electrical and concentration gradients Leak Channels: resting cells; permeable to K+ and open at rest Perturb the system: o Puncturing the cell o Applying a current across the electrodes to drive the _____ o Positive current moving into the cell and we can see the effect of this current by the use of recording equipment Excitable cells: Hyperpolarized: already polarized and make it more polarized by moving it away from 0 Accommodation: when a neuron is subjected to subthreshold stimuli of slowly increasing intensity, the threshold potential increases; determines how individual neurons respond to input whether they are continuously active or produce only bursts of APs o Some neurons accommodate rapidly and generate only one or two APs at the beginning of the stimulus period = phasic response o Other neurons accommodate more slowly and fire repeatedly, although with gradually deceasing frequency, in response to a prolonged constant stimulus have a = tonic response The difference among neurons plays a key role in how sensory neurons transmit information www.notesolution.com
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