Membrane Potentials And Excitability

Question 1

Membrane Functions

Answer 1

cellular structure, provides fluidity, selectively permeable (different mixes in and out of cell) eg ions, proteins and substrates

Question 2

Passive Transport Def.

Answer 2

Solute moves from high to low conc. and positive particles move to negative areas. 2 Types

Question 3

2 Types of Diffusion

Answer 3

Free (across membrane) and protein mediated/facilitated diffusion

Question 4

Ion Leak Channels

Answer 4

Always open, for specific ions. The number of channels for a specific ion determines hoe permeable the membrane is for that ion

Question 5

2 Types of Gated Ion Channels

Answer 5

Ligand-gated (ligand binds to receptors) and voltage gated (change in membrane potential is measured by voltage-sensor). Both undergo conformational changes when stimulated

Question 6

Example of Active transport

Answer 6

ATPase pushing 3 sodium ions out of cell and 2 potassium ions into cell using ATP

Question 7

2 Types of Vesicular Transport

Answer 7

Endocytosis (absorbing into cell) and exocytosis (pushing out of cell)

Question 8

2 Gradients across membrane

Answer 8

concentration (chemical) and charge (electrical)

Question 9

Why are stable ion gradients importany

Answer 9

Normal physiology

Question 10

Resting Membrane Potential (RMP) Def.

Answer 10

Difference in electrical charge across plasma membrane when cell is at rest. Cell works to actively maintain it. Is negative value when inside is more negative then outside

Question 11

Resting membrane potential in neurons

Answer 11

-70 mV (ranging from -60 to -100)

Question 12

Membrane Potential Function

Answer 12

Transports substances across membrane (eg ions)

Question 13

Electrochemical Gradient Def.

Answer 13

Combination of charge and concentration gradient

Question 14

Electrochemical Gradient At Equilibrium

Answer 14

Concentration gradient balances out charge gradient. No net ion flow

Question 15

Equilibrium (/Electrical) Potential Def. (mV)

Answer 15

Charge gradient that balances out chemical. Calculated by Nernst Equation

Question 16

How do K+ ions move normally at equilibrium

Answer 16

Out of cell (efflux). As K+ is positive and cell wants to move from -70 mV (RMP) to -90 mV (K+ equilibrium potential)

Question 17

How do Na+ ions tend to move

Answer 17

Into cell (influx). As Na+ is positive and cell wants to move from -70 mV (RMP) to +60 mV (Na+ equilibrium potential)

Question 18

Excitable Cells DEf.

Answer 18

Actively induce change in their membrane potentials. Eg neurons

Question 19

Depolarisation/ Excitatory Post-Synaptic Potential (out;ine

Answer 19

Positive ion influx causes excitation of cells. Action potential is formed

Question 20

Hyperpolarisation/ Inhibitory Post Synaptic Potential Outline

Answer 20

efflux of positive ions or influx of negative ions. Cell inhibition

Question 21

Threshold Voltage for action potential

Answer 21

-55 mV

Question 22

Action Potential Outline

Answer 22

Change in membrane potential (potential reverses) generating long distance

Question 23

Development of action potential

Answer 23

Resting potential (-70mV), Threshold Frquencey (-55mV, Na+ voltage gate opens, influx begins), depolarisation, action potential (55mV, Na+ closes, K+ opens), hyperpolarisation, mV decreases past Resting (K= closes)

Question 24

Refractory Period

Answer 24

Period where further stimulus won’t trigger action potential (~1ms). Reason impulse only travels down axon