The resting membrane potential

Question 1

Sensory neuron

Answer 1

carries info about the 5 sense

Question 2

interneuron

Answer 2

is in the spinal cord, activate a motor neuron

Question 3

motor neuron

Answer 3

causes muscle to contract, impacts other body reactions

Question 4

how can a interneuron not send a motor neuron in response to a sensory neuron

Answer 4

brain sends a signal down a neuron in the spinal cord that release inhibitory neurotransmitter onto the interneuron

Question 5

Ions

Answer 5

Single atoms/molecules that have unequal numbers of protons and electrons, they have a net electrical charge

Question 6

Cations

Answer 6

positive charge

Question 7

Anions

Answer 7

negative charge

Question 8

Most relevant ions

Answer 8

Na+ and K+, Ca^2+, Cl-

Question 9

Salts

Answer 9

Chemical compounds made of ions bound together, such there is a 0 net charge, table salt = potassium chloride, can be dissolved in water

Question 10

Diffusion

Answer 10

Molecules dissolved in water want to all equal space out from each other, they will flow down the concentration gradient, from high to low, until the distribution is equal (equilibrium)

Question 11

Electricity

Answer 11

Electrical current = flow of charged particles

Question 12

Electrical potential

Answer 12

= Voltage = force that moves particles away from the same charged particles away from the same charge and towards the opposite charge

Question 13

Electrical conductance

Answer 13

= ability of charge to move through a substance, opposite of resistance

Question 14

Ohm’s law

Answer 14

I=gV
I= current
g= conductance
V= potential

Question 15

Resting membrane potential, how does it acquire that negative voltage?

Answer 15

The inside of the cell contains neg charged proteins, K+ is pumped INTO the cell, Na+ and Ca^2+ is pumped out, K+ flows down the concentration gradient out of the cell through selective channels in the membrane, Net outflow of positive charge contributes to a negative membrane potential, the potential reaches “steady state” due a balance of concentration gradients and electrical potential

Question 16

During action potential

Answer 16

Na+ and Ca^2+ flow in

Question 17

Typical ion concentrations

Answer 17

Not shown: organic anions (negatively charged proteins) inside the cell, more potassium inside, more sodium, calcium , and chloride outside, each has an equilibrium potential

Question 18

Ion pumps

Answer 18

The sodium-potassium pump expends ATP to pump sodium out and potassium in, against their concentration gradients

Question 19

Ion pumps, how much is pumped in and out

Answer 19

every 2 K+ pulled in, 2 Na+ get pushed out, contributing to the negative charge

Question 20

Also a calcium pump

Answer 20

push calcium out, the mitochondria and endoplasmic reticulum also pull calcium out of the cytosol

Question 21

Potassium channels

Answer 21

most permeable to K+, which passively flows out of the cell, down its concentration gradient, establishing a negative resting potential, the resting potential would be equilibrium potential for K+ (Ek=-80mV) but some Na+ leaks in, so the resting potential is roughly -65mV

Question 22

Importance of potassium

Answer 22

The relatively low K+ concentration outside the cell, and in the blood in CRITICAL, the blood-brain barrier helps maintain extracellular K+ concentration in the brain, as do astrocytes, Mutations of the K+ channel lead to poorly functioning neurons

Question 23

What happens if the extracellular K+ concentration becomes too high? Does the membrane potential goes up or down?

Answer 23

K+ ions pumped into the cell no longer have a reason to flow outward, so the cell’s membrane potential rises, becoming less negative (depolarized)

Question 24

resting potential

Answer 24

ions are charged atoms, here dissolved in fluid, pumps establish concentration gradients (Na+ and Ca^2+ out and K+ in), selective channels allow K+, positively charged to flow out, the balance of electrical force and concentration gradients settle at -65 mV.

Question 25

2 forces that push sodium into the cell when sodium channels open

Answer 25

Electrostatic pressure and diffusion

Question 26

Electrostatic pressure

Answer 26

like charges repel, opposites attract, Na+ wants to go towards the negative inside the cell

Question 27

Diffusion

Answer 27

ions want to be spread out from other ions of the same element, so the move down their concentration gradients. Sodium is more concentrated outside the cell, so it wants to get inside