Neurophysiology Ninjanerd

Question 1

Resting Membrane Potential Basic Definition

Answer 1

-The voltage difference across the cell membrane, when the cell is at rest
-Exists in neurons, as well as all other cells
-Average voltage range -70mv through -90mv

Question 2

Sodium Potassium ATPases (Na/K+ ATPases)

Answer 2

Pumps 3 sodium ions (Na+) out of the cell (cations or + ions), then pumps 2 potassium ions (K+) into the cell; 3 positive ions are leaving the cell and only 2 positive ions are coming back into the cell, leaving it slightly negative

Establish the concentration gradient for sodium and potassium; increases the concentration of sodium outside of the cell, decreasing the sodium contraction inside of the cell; pushed potassium into the cell, leaving more potassium inside the cell and less outside of the cell

Question 3

Leaky K+ Channels

Answer 3

Proteins embedded in the cell membrane that are always open, allowing for ions to move in and out of the cell freely and passively

Potassium is higher inside the cell and lower outside of the cell, so it wants to exit the cell through the leaky K+ channels, moving from high concentration to low concentration; potassium is bound to an anion so when it leaves the cell, it leaves behind an anion that is unoccupied - making the cell super negative

Question 4

Anions (A-)

Answer 4

-Phosphates are very negatively charged ions, difficult for them to move outside of the cell
-Proteins made of AA with lots of negative charges, cannot exit the cell
-These like to interact with positively charged potassium

Question 5

Leaky Sodium Channels

Answer 5

Allows for sodium to move in and out of the cell; since Na+ is higher outside of the cell and lower inside of the cell, the sodium wants to move into the cell and down the concentration gradient - leaving the cell more positive; The neuron is WAY more permeable to potassium (K+) than it is too sodium (Na+)

Question 6

Permeability factors

Answer 6

-Potassium is significantly more permeable
-Potassium can make more significant changes to RMP
-Only a small amount of Na+ can move into the cell, not much change to RMP in this case

Question 7

Nernst Potential

Answer 7

-used when K is moving out of the cell via concentration gradient and K is moving into the cell via electrostatic gradient

Question 8

Graded Potential

Answer 8

-Take the resting membrane potential and move it closer to threshold voltage (~ -55mv)
-Need to slight depolarization to go from -70mv to -55mv
-Sometimes can take it even lower than resting membrane potential (hyperpolarization, making the cell even more negative)

Question 9

RMP —> Threshold is

Answer 9

Trying to excite the cell; called EPSP

Question 10

Hyperpolarization RMP (-70) —> -90

Answer 10

Inhibiting (taking farther away from threshold); called IPSP

Question 11

Neurotransmitter Glutamate

Answer 11

-good stimulant within the CNS
-ligand gated ion channel
-binds onto the receptor site, opens the gate
-opens the channel for any cations to flow in, making the inside of the cell more positive
-leads to EPSP

Question 12

Neurotransmitter (Inhibitory); GABA

Answer 12

-binds onto the pocket with a closed gate, stimulates the channel and opens the gate
-allows for chloride ions to come into the cell, or potassium ions to leave the cell (leaving behind anions that cannot leave)
-inside of the cell is becoming more negative
-hyperpolarize the cell, called IPSP

Question 13

Action Potential

Answer 13

-voltage gated sodium channel is generally closed
-once you hit -55mv, voltage gated sodium channels are activated at the “activation gates”, sodium ions begin to rush in very powerfully making the inside of the cell super positive
-“inactivation gate” closes at +30mv
-55mv —> +30mv
-depolarizes the cell down the axon
-voltage gated calcium channel activates when you hit +30mv, calcium rushes into the axon terminal
-calcium links the SNAIR proteins together, and the synaptic vessel fuses with the cell membrane
-peptides are released out through the synaptic space

Question 14

Axon Hillock

Answer 14

“Trigger zone”
-once you hit a particular voltage inside the cell, you can trigger an action potential

Question 15

Depolarize

Answer 15

Make the cell more positive than it previously was

Question 16

Repolarization

Answer 16

Moving from positive voltage back to negative RMP

Question 17

Hyperpolarization

Answer 17

Take a negative cell and make it even more negative

Question 18

Repolarization Process

Answer 18

-activate voltage gated potassium channels for potassium to exit the cell, takes the voltage from +30mv to -90mv (super negative)
-90mv then inhibits the voltage gated calcium channel

Question 19

Voltage Gated Sodium Channels

Answer 19

-At RMP they have 2 gates (one outside of the cell) which is generally closed at rest (activation gate), internal gate is generally open and called inactivation gate (-70mv)

-Once you hit threshold, the activation gates become activated and inactivation gates start to slowly close (when stimulated) at -55mv approaching 30mv

-Inactivation gate finally fully closes at the peak point of the action potential, activation gate is fully opened; the inactivation gate will not allow any more positive ions to enter the cell (+30mv)

Question 20

What is resting membrane potential?

Answer 20

-70mv

Question 21

What is the threshold potential?

Answer 21

-55mv

Question 22

Temporal summation

Answer 22

One presynaptic neuron releases neurotransmitters over a period of time to fire action potential

Question 23

Spacial Summation

Answer 23

Multiple presynaptic neurons release neurotransmitters together to fire an action potential in the post synaptic neuron