lecture 3 electricity in neurons

Question 1

how does information flow in the nervous system?

Answer 1

electricity

Question 2

what field of study studies the flow of information in the nervous system

Answer 2

electrophysiology

Question 3

who was the first electrophysiologist

Answer 3

luigi galvani

Question 4

what did luigi galvani discover

Answer 4

used electricity attached to frog legs and noticed the legs twitched, showing how important electricity is for motor movements (inspired frankenstein)

Question 5

what are ions

Answer 5

ions are atoms that are electrically charged (neutral atoms have an equal amount of protons and electrons, ions dont)

Question 6

difference between cation and anion

Answer 6

anions are negatively charged (extra electrons) and cations are positively charged (more protons than electrons)

Question 7

do electrons or ions move in neurons

Answer 7

ions

Question 8

what is membrane potential

Answer 8

differences in net charge between inside and outside of neuron

Question 9

what makes up the cell membrane

Answer 9

phospholipid bilayer (phosphate hydrophilic head and hydrocarbon hydrophobic tail), cholesterol, integral and peripheral proteins

Question 10

what cation is mostly in the extracellular space

Answer 10

sodium (na+)

Question 11

what cation is mostly in the intracellular space

Answer 11

potassium (k+)

Question 12

can ions pass through the phospholipid membrane

Answer 12

no, it is impermeable to charged atoms due to the hydrocarbon tail being nonpolar

Question 13

what causes membrane potential

Answer 13

ion selective channels

Question 14

what are ion selective channels made of

Answer 14

different polypeptide units

Question 15

how do ions pass through protein channels

Answer 15

they have “pores”

Question 16

how does water pass through the bilayer

Answer 16

aquaporin

Question 17

what kind of transport is ion flux

Answer 17

passive diffusion (or brownian motion), no added energy required

Question 18

what is the channel pore for cations lined with

Answer 18

negatively charged amino acid groups that repel anions (and vice versa)

Question 19

what is ion selectivity for one cation over another related to

Answer 19

hydration shell of water molecules

Question 20

how does passive flux across membranes happen

Answer 20

via permeable channels (no channels, no ions)
*also water cant cross without aquaporins

Question 21

when is eqilibrium reached

Answer 21

when concentrations no longer change (equal flux in both directions)

Question 22

what is membrane potential/electrical gradient

Answer 22

measure of difference in net charge between inside and outside of membrane = 0 mV

Question 23

why are there leak channels?

Answer 23

leak channels bring the membrane potential back to normal after the na/k pump brings increases the concentration gradient to create energy

Question 24

why is the membrane potential more permeable to potassium than sodium

Answer 24

potassium is more permeable and there are more potassium channels open (which is why the cell’s membrane potential is close to potassium’s equilibrium potential of -80 mv)

Question 25

when is equilibrium of a cell reached

Answer 25

when the concentration and chemical gradient are equal and opposite

Question 26

what is the concentration/chemical gradient

Answer 26

measures the amount of each ion

Question 27

what is the electrical gradient

Answer 27

measures the amount of charge (net positivity or negativity) on either side of the membrane

Question 28

Electrical Potential Difference

Answer 28

a difference in potential energy that exists when there is a separation of charges (an electrical gradient, see below). Measured in volts (V) and typical potentials in neurons are measured in millivolts (mV)

Question 29

Resting Potential

Answer 29

the electric potential difference across a cell’s membrane at rest (i.e. not during an action potential or a synaptic potential). A typical neuronal resting potential is about -65 mV, meaning that the inside is more negative than the extracellular fluid

Question 30

Capacitor

Answer 30

an insulator (i.e. cell membrane), separating two conducting materials, that can store charge. In neurons, capacitance determines how quickly the membrane potential can respond to changes in current

Question 31

Contrast ways electricity in the nervous system differs from electricity in wires

Question 32

What is a lipid bilayer composed of and how are these molecules arranged? Why, in the absence of channels, is it so impermeable to ions

Question 33

What are ion selective channels, and briefly describe what they do and what causes their selectivity

Question 34

If a membrane of a cell is permeable to all ions, is there a point when net ion flow across the membrane finally stops

Question 35

Diagram how a cell membrane is like a capacitor