Electro 2

Question 1

define ionic equilibrium potential

Answer 1

for a given ion it is when the concentration gradient is equal, opposite and balanced to the voltage (electrical) gradient. At this potential is ion is at equilibrium with a net flow =0

Question 2

what are the abbreviation and units for charge, resistance, current, voltage and capacitance.

Answer 2

-Q is charge (units:
coulombs)
* I is current (units: amps)
Current is movement of
charge, i.e., I = dQ/dt
* V is voltage (units: volts)
Voltage (potential) is
separation of charge
* R is resistance (units: ohms)
Conductance, g is 1/R
* C is capacitance (units:
farads)
Capacity to store and separate
charge, C = Q/V

Question 3

what is the equation used to calculate the IEP

Answer 3

the nernst equation
IEP is the proportional to the log of the concentration ratio for that ion.

Question 4

what does direction of current flow depend on for a given ion

Answer 4

concentration gradient and electrical gradient.

Question 5

what property of the neurons maintains the concentration gradient

Answer 5

ionic pumps/channels.

Question 6

what is the equation for calculating current

Answer 6

ionic current = g ion x (Vm – Eion)

Question 7

what is driving force

Answer 7

driving force is the force that determine the direction of ion flow for a given ion.

Question 8

Explain the concept of driving force with
respect to specific ionic currents

Answer 8

DF = Vm - Eion

positively charged ions:
negative DF= +ions entering
positive DF= +ions leaving

negtively charged ions:
negative DF= -ions leaving
positive DF= -ions entering

Question 9

Explain the concept of reversal potential of
an ionic current and its significance in
determining the nature (excitation or
inhibition) of synaptic potentials

Answer 9

EPSP - the summed reversal potentials for + charged ions including Na and K result in the EPSP of 0mv which is positive to threshold, allowing for the generation of APs.this increase in firing of AP likelihood is caused by positivel ions flowing into the cell. they are graded potentials such that the sum of greater individual EPSP, increase the likelihood of AP firing via depolarisation.

IPSP- the reversal potentials for - charged ions including Cl result in the IPSP of -90mv which is negative to threshold, generating hyperpolarisation not allowing for the generation of APs as it pulls the membrane potential towards the reversal potential of -90mv. caused by negative ion flow into cell or even greater positive ion outflow

Question 10

what determines whether a PSP is a EPSP or a IPSP

Answer 10

EPSP - is when the reversal potential is positive to threshold
IPSP - is when the reversal potential is negative to threshold.

Question 11

what limits the amplitude of the receptor potential of a given ion

Answer 11

the reversal potential as the membrane potential cannot exceed this level.