Action Potential

how do the equilibrium potentials of K+ and Na+ match which way they leak?

the equilibrium potential of K+ is -90 mV so K+ leaves the cell. Na+ on the otherhand is +60 mV so Na+ enter the cell

how resting potential is like tug-of-war?

potassium is leaking out of the cell pulling the cell’s potential towards -90 mV while sodium is leaking into the cell pulling the potential towards +60 mV. However, neither ion ever wins, but reach a balance at around -70 mV

why is the resting membrane potential closer to K+’s equilibrium potential?

Because the cell is slightly more permeable to K+

Na+/K+ pumps job after an action potential?

to restore the resting potential and the Na+ and K+ gradients

T or F, as sodium rushes into one segment of the axon, it will only depolarize that segment

False, as sodium rushes into one segment of the axon, it will cause depolarization in the surrounding regions of the axon (reason for refractory so it doesn’t go backwards)

effector

postsynaptic cell that is a gland or muscle

how are neurotransmitters released into the synapse?

when the action potential reaches the nerve terminal, voltage-gated Ca2+ channels open, allowing Ca to flow into the cell triggering exocytosis of the neurotransmitter

the 4 methods of removing neurotransmitters from the synaptic cleft + example neurotransmitter

1) broken down by enzymatic reactions (acetylcholine)

2) brought back into the presynaptic neuron using reuptake carriers (serotonin)

3) diffuse out the synaptic cleft (NO)

4) astrocytes have pumps to remove neurotransmitters

a) I and II
b) I, II, and III
c) I only
d) I and III

b) I, II, and III

the three states of the voltage-gated sodium channel

closed: before threshold and after inactivation has been reversed

open: from threshold to ~+35 mV

inactive: ~+35 mV to resting

a) Sodium ions moving down the concentration gradient into the cell
b) Potassium ions moving down the concentration gradient into the cell
c) Active transport of sodium ions out of the cell
d) Active transport of potassium ions out of the cell

c) Active transport of sodium ions out of the cell