6.1 Stimuli

Question 1

7 steps of the response affect (start at stimulus)

Answer 1

1. stimulus
2. receptor
3. sensory neurone
4. intermediate neurone in spinal cord
5. motor neurone
6. effector
7. response

Question 2

what can receptors be

Answer 2

cells or proteins

Question 3

what are the three types of potentials

Answer 3

1. resting potential
2. generator potential
3. action potential

Question 4

what is the pacinain corpuscle

Answer 4

it is specific to mechanical impulses by produces a generator potential by acting as a transducer

Question 5

how does the pacinian corpuscle produce an action potential

Answer 5

1. in its normal (resting) state, the stretch mediated sodium channels of the membrane around the neurone of a pacinian corpuscle are too narrow to allow sodium ions to pass along them. In this state, the neurone of the pacinian corpuscle has a resting state
2. when the pressure is applied to the corpuscle it changes shape and its neurones becomes stretched
3. this stretching widens the sodium channels in the membrane and sodium ions diffuse into the neurone
4. the influx pf sodium ions change the potential of the membrane (depolarised), thereby producing a generator potential
5. The generator potential in turn creates an action potential (nerve impulse) that passes along the neurone and then, via other neurones to the CNS

Question 6

what are the two types of cells in the retina

Answer 6

rod cells and cone cells

Question 7

Rods cells vs cone cells (6 points)

Answer 7

1. Rod cells have one type, cone have green red and blue
2. Greater number of rod than cone
3. Rod cells more frequent in the periphery, more cone in the fovea
4. Rod have poor acuity and cone cells have good acuity
5. rods cells have high sensitivity, cone have low
6. Rod cells have rhodopsin pigment and cone cells have iodopsin pigment

Question 8

what is a taxis response

Answer 8

a directional response moving towards (positive taxis) or away (negative taxis) from the stimulus

Question 9

what is taxis in response to light called

Answer 9

phototaxis

Question 10

what is taxis in response to glucose called

Answer 10

chemotaxis

Question 11

what is kinesis

Answer 11

non-directional response where the more unfavourable the conditions the more rapidly an organism moves and changes direction

Question 12

what is auxins

Answer 12

a group of hormones used by plants for growth

Question 13

what is the most common auxin

Answer 13

IAA

Question 14

4 uses of auxins

Answer 14

• promote stem elongation
• stimulate cell division
• prevent leaf fall
• maintain apical dominance

Question 15

what happens when the plant is illuminated from one side

Answer 15

the auxins move down from the shoot tip towards the shaded side of the shoot. Only those cells on the shaded side elongate bending the shoot towards the light

Question 16

what causes the axons to move

Answer 16

the photoreceptors detect light from one side causing auxin to be transported form cell to cell on the shaded side

Question 17

what do the sympathetic nervous system do

Answer 17

stimulates effectors so speeds up activity

Question 18

what does the parasympathetic nervous system do

Answer 18

inhibits effectors so slows down activity

Question 19

describe the role of receptors when exercise increases heart rate (4)

Answer 19

chemoreceptors detect rise in CO2 and baroreceptors detect rise in blood pressure
send impulses to the cardiac centre in the medulla
more impulses are sent to the SA node by the sympathetic nerve for chemo and parasympathetic for baroreceptors

Question 20

3 steps of atrial systole

Answer 20

1. sinoatrial nodes initiate the impulse at a constant rhythm
2. Impulse travels around the nerves of the atria causing them to contract forcing into the ventricles through the atrioventricular valves
3. impulse arrives at the atrioventricular nodes where there is a short delay to allow blood to filll ventricles

Question 21

3 steps of ventricular systole

Answer 21

4. Atrioventricular nodes initiate impulses
5. Impulse travels down the bundle of his to the apex of the heart
6. Impulses travels around the purkinje fibres causing the ventricles to contract forcing blood up and out via the aorta