1/23 Neurotransmission Flashcards
(49 cards)
What prevents ion exchange and is necessary for neuron function?
phospholipid bilayer
What kind of ion channels are found in neurons?
sodium, potassium, chloride
What is the membrane potential?
difference in electrical charge between the inside and outside of the neuron
What changes membrane potential?
movement of ions through the channels
At rest the average neuron has a membrane potential of
-65 mV
What is depolarization?
when the membrane potential becomes more positive (moves toward 0).
What is hyperpolarization?
when the membrane potential becomes more negative
There is a pull on each ion to go through the channels based on?
concentration
electrical imbalances
What is equilibrium potential?
the flow of ions in and out has the same pull
What is the initial equilibrium potential of Na+?
initially drawn in by both electrical and concentration gradients
As the membrane potential reaches zero what happens to the electrical gradient for Na+?
electrical gradient starts pulling Na+ back out of the cell
What is the electrochemical gradient for Na+?
+60 mV
What is the electrochemical gradient for K+?
-85 mV
What is the electrochemical gradient for Cl-?
-65 mV
How is equilibrium for electrochemical gradients calculated?
using the Nernst equation
If the current membrane potential is at -70mV which direction will the Na+ ions go to reach their equilibrium?
enter the cell
the concentration gradient would pull into cell
the electrical gradient would pull into cell (+60mV)
If the current membrane potential is at -70mV which direction will the Cl- ions go to reach their equilibrium?
exit cell
electrical gradient stronger pulling negative ions out
concentration gradient weaker but would pull ions into cell
If the current membrane potential is at -70mV which direction will the K+ ions go to reach their equilibrium?
exit cell
electrochemical gradient would pull ions out of cell (-85mV)
concentration gradient would pull ions out of cell
What is happening to ion channels at rest?
K+ channels are open and ions flowing extracellularly
Half as many Cl- channels open (flow depends on membrane potential)
25x less Na+ channels
continuous flow helps to maintain stable resting membrane potential of -65mV
What happens with the sodium potassium pump?
To move potassium back into the cell and sodium out of the cell it requires energy (ATP activates sodium potassium pump)
3 Na+ are transported out
2 K+ are transported in
keeps resting membrane potential at -65mV
What are the dynamic changes in potential?
EPSP - excitatory postsynaptic potentials
IPSP - inhibitory postsynaptic potentials
Each EPSP adds to the previous one to create a summative change to the membrane potential
What happens with EPSP’s?
Stimulus may cause the sodium channels to open
Na+ will come into the cell causing depolarization
What happens with IPSP’s?
When chloride channels open it makes depolarization less likely
What is the action potential?
When the membrane potential decreases past threshold (≈ - 50mV) it creates a sudden opening of voltage gated sodium channels (Rising phase)
1 msec later sodium channels are deactivated and voltage
gated potassium channels are activated causing a rapid repolarization (Falling phase)
Once this process starts all parts will run until completion – “all or none”
