Topic 8

Question 1

How does the action potential pass between synapses

Answer 1

1. Action potential arrives
2. Calcium ions channels open
3. Calcium ions trigger vesicles to fuse with the membrane
4. neurotransmitter diffuses across the gap
5. neurotransmitter binds to receptors
6. triggering potassium ion channels to open
7. neurotransmitters are broken down.

Question 2

Depolarisation

Answer 2

1. Neurone is stimulated
2. Depolarisation occurs if it reached -55mV an this alter the shape of the voltage dependant sodium ion channels
3. As sodium ions flow along the concentration gradient depolarisation increase opening more gates (positive action feedback)
4. At some point all gates are open flipping the potential across the membrane from -70mV to +40mV

Question 3

Repolarisation

Answer 3

1. The voltage gate Na+ channels close and the voltage gated K+ channels open
2. K+ ion flow out of the cell along both the chemical and electrical gradient until the outside
3. As a result the action potential will fall too far back (hyperpolarisation)

Question 4

restoring the resting potential

Answer 4

1. Due to open K+ channels the membrane is more permeable to K+ ions than usual
2. As a result more K+ moves out of the neurons than during a resting potential, making the potential difference more negative than normal (hyperpolarisation)
3. Closing the K+ channels allows the resting potential to be established through the difference

Question 5

What is the potential difference of the resting potential

Answer 5

-70ms

Question 6

Excitatory synapses

Answer 6

Synapses that give a signal

Question 7

Inhibitory synapses

Answer 7

Synapses that stop a signal

Question 8

label an eye diagram

Answer 8

–

Question 9

Rod Cells

Answer 9

• Work well in low-light conditions
• Provide monochrome (black & white) vision
• Contain a pigment called rhodopsin, in membrane bound vesicles.
  Distributed throughout the retina but there are none at the fovea and none at the blind spot.

Question 10

Cone Cells

Answer 10

• Only work in bright light to provide colour vision
• Contain a pigment called iodopsin, in membrane bound vesicles.
  Three types, sensitive to different wavelengths of light. Often referred to as red, green, and blue. Each contain a different form of iodopsin. Colour seen depends on the relative degree of stimulation of the different types of cone cell.

Question 11

What happens to rod cells in the dark?

Answer 11

1. Na+ diffuses in through non-specific cation channels
2. Na diffuses down the concentration gradient
3. Na+ is pumped out causing the membrane to be slightly depolarized
4. Triggering the release of the neurotransmitter glutamate

Question 12

What happen to rod cells in the light?

Answer 12

1. Rhodopsin absorbs light, breaking it down into opsin and retinal
2. Opsin binds to the cell surface, causing a cascade of reactions, closing the non-specific cation channels
3. Na+ is continually getting pumped out causing the cell to become hyperpolarized, meaning no neurotransmitter is released

Question 13

How do plants grow towards the light?

Answer 13

1. IAA is produced at the tip of the plant
2. IAA diffuses down the cell, naturally becoming more concentrated on the side without a light source
3. IAA causes growth (elongation) in cells

Question 14

Name 2 photoreceptors

Answer 14

phytochrome red Pr
Phytochrome far red Pfr

Question 15

How do long day plants know when to flower?

Answer 15

1. During the night Pfr id converted to Pr
2. During the short, summer nights not all of the Pfr is turned back into pr
3. Long-day plants needs Pfr to stimulate flowering
4. Long-day plants will only flower once the day length exceeds their critical value (typically less than 12 of darkness)

Question 16

How do short day plants know when to flower?

Answer 16

1. During the night Pfr id converted to Pr
2. During the long, winter nights all of the 3. Pfr is turned back into Pr
3. Pfr inhibits flowering
4. Short day plants will only flower when the night length exceeds the critical value (typically more than 12 hours of darkness)

Question 17

label the sections of the brain, with what each part does

Question 18

Label different parts of the brain, with what each bit does

Question 19

How does habituation work?

Answer 19

1. This depolarisation triggers the opening of Calcium (Ca2+) ion channels, allowing Calcium (Ca2+) ions to enter the neurone by diffusion.
2. Calcium (Ca2+) ions cause synaptic vesicles containing neurotransmitter to fuse with the presynaptic membrane (an example of exocytosis)
   3.