Formation and Transmission Of An Action Potential Flashcards
Which cells are the only cells that are charged?
Nerve cells
What creates the potential difference in neurons?
They have a rich supply of positive and negative ions inside and outside of the cell
How are Electrochemical signals generated?
Unequal concentrations of positive ions across a membrane
Nephrons establish a voltage difference to generate a nerve impulse. What is the charge separation called?
The membrane potential
What is Resting Membrane Potential?
The potential difference across a resting neuron
What is the charge in a resting neuron?
-70 mV
Why are neurons negative on the inside?
Large protein molecules that can’t pass through the membrane and Cl+ ions
What is the use of the Sodium-Potassium exchange pump?
It uses ATP to transport Na+ ions out of the cell and K+ ions into the cell
Pump exchanges 3 Sodium for 2 Potassium ions - this leaves an excess positive charge on the outside of the cell
Which results in the -70 mV resting membrane potential
What is a nerve impulse?
A series of action potentials (action taking place on one segment of axon)
It is an “All of nothing response” once initiated it will continue
Depolarization (reduced voltage (towards positive) between -70mV and -55mV has no effect)
Depolarization between 0 and -55mV will produce identical action potentials
Where do action potentials occur?
The Nodes of Ranvier
What is the threshold potential
-55mV
When does Depolarization occur?
When the transmembrane potential reaches threshold potential which leads to an Action Potential
When the Nerve cell gets excited, the Na+ channels open and the K+ gated close
High conc. of Na+ rush into cell (driven by c.g.)
This leads to a charge reversal (+35mV)
The charge becomes positive and the sodium gates close
Repolarization
K+ gates will open once again
K+ follows the c.g. And moves out of nerve cell (carrying their positive charge outside the membrane)
The cell returns to previous polarized state
Hyperpolarization
When the membrane returns to its previous polarized state, it became too negative for a split second
The Sodium-Potassium pump becomes active once again to
Move Sodium out of the neuron
Move Potassium into the neuron
Uses cellular energy (ATP) and takes 0.001s
Nerve cells must repolarize before a second action potential can occur
Refractory Period
The recovery time required before a neuron can produce another action potential
