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Flashcards in Action Potentials Deck (44):

If an ion flows down a concentration gradient through a channel, what kind of transport is this?

Mediated diffusion


If you place a cell in a concentrated Mg solution, what will happen?

The cell volume will decrease (Mg is non pentrarint



a single nerve cell
Can only send one type of signal in one direction
send electrical signals within the cell, and NT to signal between cells



a collection of axons outside the brain/spinal cord


General overview of neuron communication

Dendrites ad the cell body receive information/stimuli.
They transmit an electrical signal along the axon
The electrical signal reachers the end of the axon
This triggers the release of a chemical neurotransmitter
The neurotransmitter then communicates with a neighboring cell


Afferent neuron

brings sensory information in


Efferent neuron

Tells muscles what to do


What compromises the CNS

spinal cord and brain



transport neurotransmitter to the axon terminal of the neuron



protein that moves NT from the axon terminal back to the cell body



protein that moves NT to the synaptic terminal from the cell body


Resting membrane potential

Always more negative INSIDE than outside
In non-excitable cells=-5mV
in Excitable cells=-70mV


What kinds of cells are excitable?

only neurons and muscle cells


Why is the inside of a membrane negative?

Ion, but a large part is negatively charged proteins inside the cell


Na/K Pump

Active transport of ions
3Na out
2K in
1ATP used
results in a build up of + ions outside the cell- the cell is polarized and at disequilibrium.


If a cell is at -70mV and the Na channels open, which way does Na go?

Into the cell


At rest, what where is there more Na? K? + charge?

There is more Na outside the cell
There is more K inside the cell
There is overall more + charge outside the cell


When is an ion said to be at equilibrium potential?

When the electrical gradient is equal and opposite the chemical gradient


What is the equiibrium potential for K?



What is the equilibrium potential of Na?



Will a cell ever be in equilibrium for both Na and K?

No, since EP for K is -90, and EP for Na is +60. Since it can never be both of these, ions are always in flux.


Action Potential

an impulse or signal transmitted along the membrane of an excitable cell by a transient change in the membrane potential. The cell will have an influx of + ions and become temporarily more + inside than outside.


All or None law

sn individual neuron either fires or doesnt. If the stimulus doesnt depolarize the membrane to threshold, no action potential will occur


What is threshold for an action potential?



Mechanically gated ion channels

are found in sensory neurons, open in response to stretch of the membrane


chemically gated ion channels

open in response to ligand binding to a receptor. Channels open, +ions flow in, if enough flow in then they will trigger voltage gated ions to open


voltage gated ion channels

open in response to a change in voltage away from RMP. Specifically, they will open at -55mV. + ions will then rush into the cell, and it will rapidly depolarize to +30mC


Which types of channels start action potentials by creating small, local depolarizing events?

Mechanically gated and chemically cgated ion channels


Which type of channel causes a massive depolarization of the membrarne?

Voltage gated ion channels, will open when the membrane voltage reaches -55mV


What are some ways of making a graded potential into an action potential?

-Leave NT in the synapse for a long time, which will lead to repeated binding and opening of chemically gated channels
-Fire AP of the presynaptic neuron over and over again, continuing to release NT over and over again
-Have more than one presynaptic neuron release NT into the synapse


What gradients are present in a neuron?

There is more Na outside the cell, and more K inside the cell.


What Equilibrium potentials are relevent for action potentials?

Na will want to flow until the cell is at +60mV
K will want to flow until the cell is at -90mV


How do local anesthetics like lidocaine and novocaine work?

They block voltage gated ion channels
Pain receptors have numerous graded potentials i response to tissue damage, but no action potential will be reached, so the message of pain will not go to the brain.


Why do Na channels have inactivation gates?

because they have a positive feedback loop and can not resolve it on its own, while K has a negative feedback


refractory period

The period between action potentials where no action potential can be fired


Absolute refractory period

all voltage gated Na channels are either already open or inactivated. This means no more Na channels can open and the action potential can not occur.


relative refractory period

some voltage gated Na channels have returned to resting, but some are still inactivated. K channels may still be open, and the cell may be hyperpolarized. The AP could occur, it the stimulus was greater than normal


continual conduction

for unmylenated cells, the axon must be covered in Na/K pumps and voltage gated channels to maintain the signal (otherwise the leakage willl degrade the signal over distance)


What tyypes of cells are in the nervous system?

Neurons and Glial cells


Schwann cells

Glial cells that modify their plasma membranes to wrap axons, these insulate and prevent leakage.


Nodes of Ranvier

spaces between Schwann cells where pumps and channels still exist


Saltatory conduction

channels only exist at the nodes of ranvier, so the signal "jumps" from node-to node.



removal of the myelin sheath/ the death of schwann cells


Multiple sclerosis

Immune attack of myelin sheath and killing of schwann cells
Is an autoimmune disease
sporadic/periodic attacks (flare ups)