Passive properties and excitability of the membrane

Question 1

what’s the equivalent circuit model?

Answer 1

representing ion channels impact in terms of electrical behaviour

Question 2

what’s the symbol for battery/ion pump?

Answer 2

https://www.google.com/search?q=battery+circuit+symbol&safe=active&rlz=1C1CHBF_en-gbGB767GB767&sxsrf=ACYBGNTXpxpx5zSUsRdRIFpPI4V57wOWlA:1579437266082&source=lnms&tbm=isch&sa=X&ved=2ahUKEwjB7sGp1o_nAhUYThUIHfqxBokQ_AUoAXoECA8QAw&biw=1280&bih=616#imgrc=rCiZiuvofV6iFM:

Question 3

what does the ion channel/ battery generate?

Answer 3

voltage

Question 4

what is voltage also known as?

Answer 4

electromotive force

Question 5

what does the voltage determine?

Answer 5

current flow

Question 6

for each set of ion channels, what does EMFion equal?

Answer 6

Eion for each set of ion channels

Question 7

what is driving force?

Answer 7

difference between membrane and equilibrium potential

Question 8

in the membrane what does conductance represent?

Answer 8

ion channel permeability

Question 9

what is conductance?

Answer 9

how readily a current will pass through a material

Question 10

how are conductance and resistance related?

Answer 10

inversely proportional (opposites)

Question 11

what is resistance?

Answer 11

how much a material opposes the flow of current

Question 12

what are the 2 assigned units for conductance?

Answer 12

Siemens (S) or Ohms-1 (Ω-1)

Question 13

in the membrane is conductance constant or variable?

Answer 13

variable

Question 14

what does conductance determine in membrane?

Answer 14

current at a particular membrane potential

Question 15

what is ohms law?

Answer 15

the relationship between voltage and current

Question 16

what equation represents the relationship between membrane potential, equilibrium potential, voltage and conductance?

Answer 16

(Vm- Eion)= Iion/ Gion

(membrane potential- equilibrium potential) = voltage/ conductance

Question 17

if Vm=Eion is there current?

Answer 17

no

Question 18

draw the symbol for capacitance

Answer 18

https://www.google.com/search?safe=active&rlz=1C1CHBF_en-gbGB767GB767&biw=1280&bih=616&tbm=isch&sxsrf=ACYBGNTnNiCP2mSg0C0qGFQny1V7D9n2Tw%3A1579437270517&sa=1&ei=1kwkXoWKH_zTgwep_oD4Ag&q=capacitance&oq=capacitance&gs_l=img.3…459116.460592..460868…0.0..0.0.0…….0….1..gws-wiz-img.vRUdKOzR7Zc&ved=0ahUKEwiFzdCr1o_nAhX86eAKHSk_AC8Q4dUDCAc&uact=5#imgrc=EPmf5l-w2v0LUM:

Question 19

what do capacitors do?

Answer 19

store charge

Question 20

what is a capacitor?

Answer 20

2 conductors separating by non-conductive material

Question 21

what, biologically acts as a capacitor?

Answer 21

membrane

Question 22

what are the units of capacitance?

Answer 22

Farad (F)

Question 23

give the equation to calculate capacitance

Answer 23

Capacitance (C)= Stored charge (Q)/ Voltage (V)

Question 24

if there’s capacitance what happens as potential difference (voltage) increases, what happens to stored charge?

Answer 24

it also increases

Question 25

if there's capacitance and potential difference reduces, what happens to stored charge?

Answer 25

it also reduces

Question 26

what occurs due to charge being moved on and off a capacitor?

Answer 26

capacitive current

Question 27

does capacitive currents affect IC conc/ ion gradients?

Answer 27

no- as long as the voltage change is <100 mV (+ or -)- as only a relatively small number of ions are required for capacitance

Question 28

what membrane factor determines total capacitance?

Answer 28

surface area of membrane

Question 29

if you simplify the equivalent circuit model, what 3 components are important?

Answer 29

- conductance - equilibrium potential - capacitance

Question 30

how is total conductance calculated?

Answer 30

sum of all conductances

Question 31

how is total current calculated?

Answer 31

sum of all currents

Question 32

how is passive and active membrane behaviour recorded?

Answer 32

2 electrodes- one applies current to one part, another records current in another part

Question 33

if a negative current is applied, what happens to membrane?

Answer 33

hyperpolarisation

Question 34

if a positive current is applied, what happens to membrane?

Answer 34

depolarisation

Question 35

what's different between current injected and current recorded?

Answer 35

current injected is seen as square | current recorded has lag

Question 36

if current was affected by conductance only, how would the current recorded look?

Answer 36

also a square

Question 37

what is causing the lag?

Answer 37

capacitance- must obey capacative law

Question 38

what is tau?

Answer 38

time constant

Question 39

what is time constant?

Answer 39

time taken to achieve a 63% change in voltage

Question 40

how is voltage calculated by rearranging capacitance equation?

Answer 40

V= Q/C

Question 41

how does increased capacitance affect rate of change?

Answer 41

reduces it

Question 42

how does decreased capacitance affect rate of change?

Answer 42

increases it

Question 43

how is Tau (t) calculated? (2 ways)

Answer 43

``` t= C x R time constant = capacitance x resistance or t= C/G time constant = capacitance/ conductance ```

Question 44

is capacitance usually constant or variable in a cell membrane and why?

Answer 44

constant as cell membrane SA doesn't change

Question 45

if the duration of a stimulus is short, what must the intensity be to reach threshold?

Answer 45

high

Question 46

if the duration of a stimulus is long does the intensity need to be long to reach threshold?

Answer 46

no

Question 47

what are the 2 affects of conductance on membrane?

Answer 47

higher conductance , lower response lower conductance, higher voltage higher conductance, reduced Tau- reaches threshold quicker

Question 48

how is conductance related to neuromodulation?

Answer 48

inhibitory neurotransmitters increase conductance e.g. GABA | excitatory neurotransmitters reduce conductance e.g. glutamate

Question 49

is an elongated structure leaky?

Answer 49

yes

Question 50

the further away from source of current, how does current change?

Answer 50

gets lower- due to leakiness