1. neurones

Question 1

resting potential

Answer 1

outside positive relative to inside
membrane polarised (difference in charge - potential difference / voltage)
-70mV

Question 2

resting potential created and maintained

Answer 2

sodium potassium pumps (ATP needed) and potassium ion channels in neurone membrane
move 3 sodium ions out (membrane impermeable to sodium cant get back in) = electrochemical gradient
move 2 potassium ions in (membrane permeable. facilitated diffusion back out through potassium ion channels)

OUTSIDE POSITIVE RELATIVE TO INSIDE

Question 3

action potential

Answer 3

1. stimulus excites neurone cell membrane
   sodium ion channels open (permeable)
   sodium ions diffuse in
   inside less negative
2. depolarisation - potential difference reach threshold (-55mv) more sodium ion channels open
   diffuse in rapidly
3. repolarisation - +30mv sodium ion channels close
   potassium ion channels open
   potassium ions diffuse out

4. hyperpolarisation - potassium ion channels too slow to close 
slight overshoot (more negative than RP less than -70mv)

5. resting potential - ion channels reser
   sodium potassium pump returns membrane to RP

Question 4

refractory period

Answer 4

after AP cant be excited straight away
ion channels recovering cant be made to open
sodium ion channels closed repolarisation
potassium ion channels closed hyperpolarisation

Question 5

move along neurone in wave of depolarisation

Answer 5

action potenial
some sodum ions diffuse sideways
sodium ion channels in next region open
refractory period - can only go in one direction

Question 6

refractory period acts as time delay ensures

Answer 6

AP dont overlap - discrete impulses
limit to frequency
AP are unidirectional

Question 7

all or nothing

Answer 7

threshold reached AP always fire with same change in voltage
not reached AP wont fire
bigger stimulus wont cause bigger AP but AP fired more frequently

Question 8

myelination / myelin sheath

Answer 8

electrical insulator
made of Schwann cells
between Schwann cells bare membrane called nodes of ranvier (sodium ion channels concentrated here)
deploarisation only at nodes
neurones cytoplasm conducts electircal charge to depolarise next node
AP jumps from node to node -saltatory conduction - fast

Question 9

non myelinated neurone

Answer 9

impulse travels as wave along whole length of axon membrane

slower

Question 10

axon diametre

bigger

Answer 10

quicker
less resistance to flow of ions in cytoplasm
depolarisation quicker

Question 11

temperature

high temperatyre

Answer 11

quicker
ions diffuse faster
increases up to 40C after this denatures