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Wk 1 STUDY QUESTIONS - ch 1-4
Terms in this set (17)
How do the cytoplasm of the axon and the axon terminal differ?
- microtubules do not enter the terminal
- synaptic vesicles in the terminal
- dense proteins along membrane of pre-synaptic neuron (terminal) (?)
- multiple mitochondria in axon terminal, due to high energy demand
Explain equilibrium potential, using K+ as an example
If only ion channels permeable to K+ are open, the membrane potential will reach -80 mV instead of the resting -65 mV
Diffusion allows K+ to start leaving the inside of the cell, depolarizing membrane.
However, the highly negative electrical charge of the cell inside will begin to pull some K+ back, until a ~stable -80 mV is reached
Where is the difference in electrical charge seen in a neuron?
Right at the cell membrane, over a micrscopic distance (not really scattered)
Explain the sodium-potassium pump
- 3 Na+ OUT, 3 K+ IN
- uses ATP for energy to change channel shape
- goes from low to high gradient (against concentration)
- only pumps sodium and potassium
What happens when increasing levels of extracellular potassium, and why?
What happens when membrane potential = 0 mV?
no electric potential means no channels, no method to move.
What happens if K+ concentration is increased outside the membrane?
Increased electrical potential → increased current once K channels are opened (I THINK)
If there is a greater ionic concentration OUTSIDE than inside the membrane, is Eion positive or negative? Provide an example
Positive (for Na+ and Ca2+)
e.g. Na+ (Eion 62 mV) has a higher concentration OUTSIDE the cell membrane, and therefore flows in
If there is a greater ionic concentration INSIDE than outside the membrane, is Eion negative or positive? Provide an example
Negative (for K+ and Cl-, even though Cl- is more concentrated outside the cell)
e.g. K+ (Eion = -80 mV) has a higher concentration INSIDE the cell membrane, and therefore flows out
Why is E(Cl-) negative?
Because even though the concentration of Cl- is higher outside the membrane, its negative charge (z) makes the result of the Nernst eq negative
Which ion(s) are more concentrated outside the neuronal membrane when at rest?
Na+, Ca++, and Cl-
Which ion(s) are more concentrated inside the neuronal membrane when at rest?
The neuronal membrane at rest is most permeable to which ion?
therefore very sensitive to changes in concentration of extracellular potassium
Driving force if Vm = Ek; if gk = 0
Can an action potential change direction midway through? Why/why not?
No, bc the membrane where the action potential just came from is undergoing the refractory period (Na+ channels deactivated)
Why are smaller axons more sensitive to local anesthetics than bigger axons?
NaV channels are open more often to ensure the AP doesn't fade, giving anesthetics a greater chance to bind to these NaV channels and prevent APs
Why does the myelin sheath require nodes of Ranvier?
Breaks in insulation contain the NaV channels required to generate APs
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