neurons

Question 1

neuron dendrites function

Answer 1

receive electrical input

Question 2

neuron cell body function

Answer 2

passively conducts electrical signals

Question 3

neuron axon hillock/initial segment/trigger zone function

Answer 3

initiates action potentials

Question 4

neuron axon function

Answer 4

propagates action potentials

Question 5

neuron axon terminal function

Answer 5

releases chemical signals across synapse

Question 6

how much more negative are neuron cytosol compared to extracellular fluid

Answer 6

50 to 70mV more negative

Question 7

how are intracellular potentials measured today?

Answer 7

1.)microelectrode recording technique

2.) patch clamp technique

Question 8

what affects Resting Membrane Potential (RMP)

Answer 8

1.) unequal concentrations of ions inside and outside of cell resulting in electrochemical gradient

2.) unequal membrane permeability to these ions

Question 9

two main types of ion channels in neurons

Answer 9

leak channels - open at rest (many K+, fewer Na+ leak channels)
gated channels - closed at rest, (voltage, mechanical, ligand stimuli)

Question 10

1:40 is the ratio of….

Answer 10

ratio of sodium to potassium leak channels/ratio of membrane permeability of sodium to potassium ions

Question 11

nernst equation calculates…

Answer 11

-equilibrium potential for one type of ion

-considers only concentration of ion inside and outside of cell

Question 12

equilibrium potential for K+ and Na+

Answer 12

K+ = -80mV

Na+ = +60mV

Question 13

nernst equation application to neurons and glial cells

Answer 13

-only applies when membrane is permeable only to one ion

-applicable to glial cells because they’re only permeable to K+ so RMP is -80mV

-NOT applicable to neurons as they’re permeable to more than one ion type

Question 14

goldmans equation calculates…

Answer 14

resting membrane potential (-65mV)

considers concentration gradient AND relative permeability of resting membrane to K+ and Na+ ions

Question 15

factors in nernst equation

Answer 15

ion concentration extracellular and intracellular

faradays

gas constant

temperature

valence of ion

Question 16

threshold value required to generate AP

Answer 16

approx -55mV

Question 17

4 phases of action potentials

Answer 17

stimulus, fast depolarisation, repolarisation, after hyperpolarisation

Question 18

absolute vs relative refractory period

Answer 18

absolute during fast depolarisation and repolarisation - no stimulus can cause another AP

relative during the end of repolarisation and after hyperpolarisation - stimulus can only cause another AP if larger than the original threshold

Question 19

fast depolarisation caused by

Answer 19

stimulus reaching threshold activates voltage-gated Na+ channels letting sodium into the cell (relative permeability of Na+ to K+ now 20:1 so more permeable to Na+)

Question 20

repolarisation caused by

Answer 20

quick inactivation of Na+ voltage gated channels and activation of voltage gated K+ channels

Question 21

after hyperpolarisation caused by

Answer 21

membrane permeability of K+ to Na+ really large 100:1

Question 22

Na+ voltage gated channel mechanism during repolarisation and after hyperpolarisation

Answer 22

repolarisation when Na+ gated channel INACTIVATES due to inactivation gate shuts (ball and chain)

after hyperpolarisation (back at RMP) when Na+ gated channel AT REST due to activation gate shut and inactivation gate open

Question 23

what causes passive current to dissipate

Answer 23

leak channels

Question 24

receptor potential

Answer 24

graded depolarisation

Question 25

end plate/neuromuscular junction

Answer 25

motorneuron with axon forming synpase on muscle fibre

Question 26

end plate potential is always

Answer 26

suprathreshold meaning an action potential is always triggered

Question 27

factors determining synaptic action

Answer 27

1.) type of neurotransmitter/ neuromodulator 2.) type 3.) and amount of receptor

Question 28

long term potentiation vs long term depression

Answer 28

LTP = stimulating multiple times leads to more receptors expressed LTD = stimulating multiple times leads to less receptors expressed

Question 29

why can only neurons and muscle fibres SUDDENLY change their membrane potential

Answer 29

because of voltage gated ion channels allowing them to be excitatory