PSYCHOBIOLOGY - neuroelectrical activity

Question 1

what is meant by an electrochemical gradient?

Answer 1

• neurons exist in a chemical soup of negative & positive electrically charged particles
• the inside of the neuron is negatively charged relative to its environment

Question 2

what is the resting potential?

Answer 2

-70mV

Question 3

what would happen if membranes were non permeable?

Answer 3

electrical potential would remain static - nothing would enter or leave so nothing would change

Question 4

what would happen if membrane channels were passive holes?

Answer 4

membrane would depolarise & electrical potential would disappear

Question 5

what is the role of the sodium potassium pump?

Answer 5

active channel which pumps out 3 Na+ ions for every 2 K+ that come in

Question 6

what is meant by an ion gradient?

Answer 6

ion concentrations differ between the inside & outside of the cell

Question 7

how is a negative resting potential maintained?

Answer 7

more positive ions (Na+) are pumped out of the membrane than are allowed in

Question 8

what is an ion specific channel?

Answer 8

gates which open by chance or stimulation

Question 9

what is electronic transmission?

Answer 9

electrical & concentration gradients sweeping ions along the membrane
- initial magnitude depends on how many ions enter membrane
- some ions get lost so signal decays -> graded
- passive - no energy required

Question 10

what is action potential?

Answer 10

electrical & concentration gradients pushing / pulling ions across the membrane
- active - requires energy
- not graded - self replicating with constant magnitude so no decay

Question 11

describe how voltage gated membrane channels work

Answer 11

• Na+ channels open or close in response to electrical changes at the membrane
• membrane is depolarised to -50mV
• some Na+ channels open and ions enter
• membrane further depolarises to threshold
• all Na+ channels open

Question 12

what happens if the membrane potential at the axon hillock remains below -50mV?

Answer 12

the resting potential returns

Question 13

what happens if the membrane potential at the axon hillock depolarises beyond -50mV

Answer 13

all Na+ channels open and an action potential is generated

Question 14

what is meant by complete depolarisation?

Answer 14

so many Na+ ions enter the cell that the inside of the membrane is more positive than the outside

Question 15

describe the process of repolarisation

Answer 15

after depolarisation, Na+ channels close and K+ channels open so that K+ ions leave

Question 16

describe the process of hyperpolarisation

Answer 16

K+ channels close when resting potential is stored, fewer K+ ions are inside than outside so membrane charge becomes more negative than resting potential

Question 17

describe 4 properties of the axon potential

Answer 17

• does not decay during transmission: always strong enough to depolarise the next area of membrane
• all or nothing: no different intensities
• discontinuous: minimal time between subsequent action potentials is 2-5ms
• very fast: 1-10m/s

Question 18

describe saltatory conduction

Answer 18

• myelinated axons = faster transmission
• myelin prevents inflow & outflow of ions
• myelin interrupted by gaps called nodes of ranvier
• action potential jumps between nodes
• speeds up transmission rate