HBF L7 Membrane potential and excitability

Memebrane funcitons

Cellular structure
Fluidity of membrane
Physical barrier that prevents free passage of substance

Passive transport

Seeks to establish equilibrium between intracellular and extracellular compartments

Voltage gated ion channels

Voltage sensor in ion channel protein
Changes in membrane potential induce conformational change to open or close the channel

Active transport

Maintains the Na+ and K= gradients across plasma membrane

RMP

Difference in electrical charge across the plasma membrane when the cell is 'at rest'

What happens in response to a stimuli

ion channels open and move towards equilibrium potential

Excitable cells

Actively induce changes in their membrane potential

Depolarization

Influx of positively charged ions

influx of positively charged ions

Excitary post synaptic potential

Hyperpolarisation

Efflux of positively charged ions
Influx of negatively charged ions

What is the influx and efflux that occurs in hyerpolarisation known as

Inhibitory post synaptic potential

Action potential

Brief rapid change in membrane potential during which the potential reverses

What pushes the membrane potential across the action potential threshold?

Depolarisation

What type of channels open when the voltage reaches a peak during an action potential?

Voltage gated K+ channels

refactory period

Further stimulus will not trigger another action potential

Summation

Neuron is brought to action potential threshold at the axon hillock

What is all-or - none in action potentials

Strong stimulus produce an action the same amplitude as a weak stimulus

Active transport

Consumes ATP to transport molecules against a concentration gradient

Leak channels are

always open
Specific

Ligan gated ion channel

Receptor embedded in the channel
Binding induces conformational changes to open or close

electrochemical gradient

Charge gradient + concentration gradient

Calculate the equilibrium potential

Using Nernst eqn

What opens as a result of reduced voltage during an action potential?

Voltage gated Na+ channels