Cell Signalling 2

Question 1

Define membrane potential and what it typically is

Answer 1

The membrane potential is the voltage difference between the interior and exterior of a cell
This is typically around -70mV (but it varies )

Question 2

How does the membrane potential arise- at rest

Answer 2

At rest the membrane potential is determined by the concentration of K+ ions - this gives arises to an ion gradient from in to out and a electrical gradient from outside to inside

Question 3

Define equilibrium potential( ion movement gives rise to what gradients )

Answer 3

The equilibrium constant is the potential when a given ion’s movement gives both an ion gradient and electrical gradient.. this is when the rate of the ion going in and out is at an equillibrium

Question 4

The Nernst equation allows you to calculate the eq potential for a given ion
What is this equation

Answer 4

V= RT/zF * ln [OUTSIDE]/[INSIDE]

R= gas constant ( 2 cal/mol/K)
T= absolute temperature (K) = 273.13 + C
F= faraday’s constant (2.3 * 10^4 cal/V/mol)
z= valence charge of ion

Question 5

The RESTING membrane potential arises primarily due to K+ imbalance
What equation can be used to calculate the membrane potential

Answer 5

The Goldman-Hodgkin-Katz equation
other ions are negligible so only [K+] At rest is used
Vrest= RT/F *ln (K OUT)/ (K IN)

Question 6

How do action potentials arise? What ion channels facilitate this ?

Answer 6

Action potentials arise through the concerted action of voltage Na+ and K+ channels

Question 7

How is the action potential propagated along the axon ?

Answer 7

Small depolarization activates the volatge gated ion channels- allows sodium ( positive ) to depolarize the negatively charged inside of the axon

Question 8

What is the GHK equation for an active membrane ?

Answer 8

Vactive = RT/F* ln Na( out) / Na (in)

Question 9

How is the membrane repolarized ?

Answer 9

Voltage gated K+ channels allow potassum in - which makes the membrane potential negative again

Question 10

What causes the release of neurotransmitters at nerve terminals ? ( what gated channels are involved - what ion do they conduct )

Answer 10

Opening of Ca2+ voltage gated channels causes the release of neurotransmitters

Question 11

How are ligand gated channels activated ?

Answer 11

Ligand gated ion channels are activated by synaptically-released neurotransmitters

Question 12

Describe what IGluRs( ionotropic glutamate receptors )- what ions do they conduct and where are they found

Answer 12

IGluRs conduct Na+/Ca2+ and are found at excitatory synapses

Question 13

Describe GABA A receptors (how many subunits , what do they conduct and where are they found )

Answer 13

GABA A receptors are pentamers that conduct Cl- and are found at inhibitory synapses

Question 14

what do Nicotinic Acetyl choline receptors do ( what ion do they conduct, where are they found )

Answer 14

nAchRs conduct Na+ ions and are found at excitatory synapses and the NMJ

Question 15

What happens when the muscles are depolarised- mention ion involved

Answer 15

Depolarization of muscle cells induces Ca2+ dependent contraction