L5 & L6 - Neurons

Question 1

Hodgkin and Huxley

Answer 1

1940

giant squid axon experiments which showed mechanism of action potential

Question 2

Homogenizing forces

Answer 2

forces that act to evenly distribute ions equally throughout intracellular and extracellular fluid

1. random motion and conc grad
2. electrostatic pressure1

Question 3

What forces counteract the homogenising forces?

Answer 3

~ different permeability of ions

~ sodium-potassium pump

Question 4

Levels on ions inside the cell at resting potential.

Answer 4

~ low Na+ and Cl-
~ high K+
(outside cell is opposite)

Question 5

What is the membranes resting potential?

Answer 5

-70mV

Question 6

Why is the refractory period important?

Answer 6

~ AP only travel in one direction
~ rate of firing relative to intensity of stimulus
~ 1-2ms

Question 7

Saltatory conduction

Answer 7

conduction of AP hops between nodes of Ranvier

Question 8

How is acetylchloline made?

Answer 8

choline + acetyle CoA = acetylcholine

choline acetyltransferase needed

Question 9

Presynaptic transporters

Answer 9

inactivation of neurotransmitters by reuptake

Question 10

How is acetylcholine removed from receptors?

Answer 10

Actylecholinesterase breaks down ACh to acetate and choline

Question 11

What affects can neurotransmitters have on neurones?

Answer 11

Depolaisation - increase likely hood of firing

Hyperpolaristion - decrease likelihood of firing

Question 12

Temporal summation

Answer 12

several impulses from one neurone over time

Question 13

Spatial summation

Answer 13

several impulses from different neurons at the same time

Question 14

How can drugs affect synapses? (5)

Answer 14

1. increase no. of impulses
2. release NT from vesicles with or w/o impulse
3. block reuptake/receptors
4. produce more/less NT
5. prevent vesicles from releasing NT

Question 15

Agonistic drug

Answer 15

facilitates normal postsynaptic effect of NT

Question 16

Antagonistic drug

Answer 16

blocks/inhibits normal postsynaptic effects of NT

Question 17

Which three drugs affect NTs?

Answer 17

Methamphetamine
Nicotine
Alcohol

Question 18

Methamphetamine

Answer 18

~ enters dopamine vesicles causing release of NT
~ blocks dopamine transporters from pumping dopamine back into the transmitting neuron
= more dopamine in synaptic cleft = euphoric feeling

Question 19

Problems with taking methamphetamine.

Answer 19

~ euphoric feeling ‘crashes’ and won’t return until the drug is taken
~ long term use can cause cons to die

Question 20

Cocaine

Answer 20

blocks dopamine and works in a similar manner to methamphetamine

Question 21

Nicotine

Answer 21

similar to dopamine release into synapse like methamphetamine
~ BUT binds to receptors on postsynaptic neuron (diff. mechanism)

Question 22

Alcohol

Answer 22

~ alters neurone membranes, ion channels, enzymes and receptors
~ binds directly to receptors for acetylcholine, serotonin, GABA and glutamate

Question 23

GABA

Answer 23

~ inhibitory neurotransmitter
~ binding allows Cl- ions to pass into neurone
~ causes hyperpolarisation of neurone = inhibits impulse transmission

Question 24

GABA + Alcholol

Answer 24

~ alcohol binds to GABA receptors = increased hyperpolarisation of neurone
~ neurone activity diminished
~ responsible for sedative effects

Question 25

Threshold level

Answer 25

-55mV

neurone will only send impulse if signal reaches this level of depolarisation