grey matter

Question 1

What is the bipolar membrane responsible for?

Answer 1

Connects photoreceptors to the optic nerve.

Question 2

Where are rods found?

Answer 2

Retina

Question 3

Where are cones found?

Answer 3

The fovea

Question 4

What is the light sensitive pigment that is found in rods?

Answer 4

Rhodopsin

Question 5

What is rhodopsin made from?

Answer 5

Retinal and opsin

Question 6

What prevents information reaching the brain when the rods are unstimulated?

Answer 6

• open sodium channels causes depolarisation
• neurotransmitters released
• these inhibit the bipolar neurone

Question 7

What is bleaching?

Answer 7

When light energy causes rhodopsin to break into retinal and opsin

Question 8

What phase is the membrane in when rod cells are stimulated?
Why does this allow information to reach the brain?

Answer 8

Hyperpolarisation

-it prevents the release of more neurotransmitters, uninhibiting the bipolar neurone

Question 9

What happens to the impulses when there is a bigger stimulus?

Answer 9

Action potentials fire more frequently, not more often

Question 10

Outline the course of events which cause the action potential to move down the neurone

Answer 10

• some of the Na+ ions diffuse sideways
• this causes sodium channels in the next region of the neurone to open, and Na+ ions to diffuse into it
• this causes a wave of depolarisation to spread down the neurone

Question 11

Why are impulses discrete?

Answer 11

• during the refractory period, ion channels can’t be opened
• this prevents action potentials from overlapping.

Question 12

Why do impulses move down myelinated neurones faster?

Answer 12

• myelin is an electrical insulator
• depolarisation can only occur at the nodes of ranvier
• the cytoplasm conducts enough charge to depolarise the next node, the impulse jumps

Question 13

What is it called when the impulse jumps down the nodes of ranvier?

Answer 13

Salutatory conduction

Question 14

what do the sodium potassium pump and potassium ion channels regulate?

Answer 14

-resting potential

Question 15

what does ‘resting potential’ refer to?

Answer 15

the polarisation of the membrane, there are more positive ions outside the cell than inside

Question 16

how do the sodium potassium pump + potassium channels work?

Answer 16

• Na/K pumps sodium ions out of the cell via active transport, they cant diffuse back into the cell
• this creates an electrochemical gradient because there are more Na ions outside the cell
• K ions are moved back in, but the membrane is permeable to K, so they diffuse back out
• this makes the outside of the cell positively charged

Question 17

why does the membrane become depolarised when a stimulus arrives?

Answer 17

Na+ channels open, Na+ ions diffuse into the neurone making the inside less negative

Question 18

why does repolarisation occur?

Answer 18

Na+ channels close and K+ channels open, K+ diffuses out of the neurone

Question 19

why does hyperpolarisation occur?

Answer 19

K+ channels are slow to close, too many leave

Question 20

what is meant by ‘refractory period’?

Answer 20

ion channels are recovering and cannot be forced to open

Question 21

what affect does habituation have on the amount of calcium ions in the pre-synaptic membrane?

Answer 21

decreases the number of Ca2+ ions which enter the pre-synaptic membrane, causing less neurotransmitter to be released from vesicles into the pre-synaptic cleft

Question 22

what does the visual cortex do?

Answer 22

recieves and processes visual information

Question 23

what happens when a stimulus is provided during the critical period?

Answer 23

synapses that receive visual stimulation and pass nerve impulses to the visual cortex are retained

Question 24

what is a dopamine agonist?

Answer 24

something that mimics dopamine, binding to dopamine receptors in the brain and triggering an action potential

Question 25

how does fMRI work?

Answer 25

oxyhaemoglobin produces a weaker response to magnetic fields.
this means that more active parts of the brain produce a weaker signal due to increased oxygen uptake

Question 26

what are the roles of glycolysis?

Answer 26

• phosphorylation of hexoses

- production of ATP, reduced coenzyme, pyruvate and lactate

Question 27

how are drugs made using genetically modified microorganisms?

Answer 27

• gene is isolated using restriction endonucleases
• gene copied using PCR
• copies inserted into plasmids
• microorganisms grown and produce protein which can be purified

Question 28

what does the sarcoplasmic reticulum do?

Answer 28

stores and releases Ca2+

Question 29

name two benefits of habituation

Answer 29

• dont waste energy

- more energy can be used for food

Question 30

how does the level of activity of the enzymes in a metabolic pathway ensure that optimum level of product is produced?

Answer 30

• compound cant be broken down faster than it is made
• activity of enzyme that makes the product must be similar to the activity of the enzyme that breaks it down
• one enzyme is rate limiting