Unit 6

Question 1

define stimulus

Answer 1

detectable change in internal or external environment of an organism

Question 2

define receptors

Answer 2

cells which detect a stimulus

Question 3

what is the importance of being able to respond to stimuli

Answer 3

increases chance of survival and reproduction

Question 4

name the tropism for light in plants

Answer 4

phototropism

Question 5

name the tropism for gravity in plants

Answer 5

gravitropism (geo-)

Question 6

what is IAA (indoleacetic acid)

Answer 6

a type of auxin and growth factor which elongates cells or inhibits it

Question 7

why is phototropism important

Answer 7

required for the light dependant reaction in photosynthesis

Question 8

describe what happens when light is on one side of the shoot

Answer 8

IAA diffuses to the shaded side, theres a greater con. of IAA there. cells elongate and the shoot moves toward the lighter side (positive phototropism)

Question 9

in the roots IAA inhibits cell elongation, describe what happens when light is on one side of the root

Answer 9

IAA diffuses to the shaded side, theres a greater con. of IAA there. cell growth is inhibited and the root turns away from the light (negative phototropism)

Question 10

what is the importance of root moving downwards

Answer 10

plants anchor into the ground and can reach more water sources, needed in the light dependant reaction of photosynthesis

Question 11

describe gravitropism in the shoots

Answer 11

IAA diffuses in the direction of gravity and the lower cells elongate, the shoot moves vertically up

Question 12

if the plant is on its side and the shoots turn upwards this would be called

Answer 12

negative gravitropism

Question 13

if the plant was on its side describe what would happen at the roots

Answer 13

IAA would diffuse downwards with gravity, inhibiting elongation. the upper side of the roots would grow and the shoot would turn downward (positive gravitropism)

Question 14

define reflex

Answer 14

a rapid, automatic response to protect the animal from danger

Question 15

give the three neurones of the reflex arc in order

Answer 15

sensory neurone, relay neurone, motor neurone

Question 16

define taxes

Answer 16

the entire organism moves its whole body away from an unfavourable or toward a favourable stimuli

Question 17

define kinesis

Answer 17

an organism changes the speed of movement or rate it changes direction

Question 18

give three examples of conditions of an environment

Answer 18

light, moisture, chemicals (pH)

Question 19

what is the purpose of kinesis

Answer 19

to move in order to find favourable conditions

Question 20

what kind or receptors a pacinian corpuscles and describe structure

Answer 20

pressure receptors, a sensory neurone ending at the centre of connective tissue (lamellae) in layers separated by gel

Question 21

describe what happens to pacinian corpuscles when pressure is applied

Answer 21

• stretch-mediated sodium channels deform allowing Na+ ions to enter. if enough sodium ions diffuse into the axon an generator potential may be established
• if exceeds threshold an action potential may form

Question 22

name the two photoreceptors in the retina

Answer 22

rods and cones

Question 23

rods allow you to see in black and white in very low light intensity. what pigment do they contain

Answer 23

rhodopsin

Question 24

what happens to rhodopsin in light

Answer 24

the pigment breaks down

Question 25

rod cell provide a low visual acuity. what does this mean

Answer 25

many rod cells are connected to one neurone (spatial summation) so light sources are more difficult to distinguish

Question 26

cones process in colour. what pigment do they have

Answer 26

iodopsin (red green blue)

Question 27

in what conditions is iodopsin broken down

Answer 27

high light intensity

Question 28

what kind of summation do cone cells have

Answer 28

temporal summation - only one cone cell per neurone

Question 29

what kind of visual acuity do cones have

Answer 29

high visual acuity (can distinguish wavelengths)

Question 30

where are rod cells

Answer 30

mainly outside the fovea

Question 31

where are cone cells and why

Answer 31

mainly in the fovea (closes to light, receives higher light intensity)

Question 32

the cardiac muscle (heart) is myogenic. what is meant by that

Answer 32

contracts on its own accord

Question 33

where is the sinoatrial node (SAN) found

Answer 33

the right atrium

Question 34

where is the Atrioventricular node (AVN) found

Answer 34

in the right atrium, near the border of the right and left ventricle

Question 35

where is the bundle of His (conducting tissue) found

Answer 35

runs through the septum of the heart

Question 36

where are the Purkyne fibers found

Answer 36

along the walls of the ventricles

Question 37

describe how the cardiac muscle is pumped

Answer 37

- SAN releases a wave of depolarisation causing the atria to contract - then AVN then releases another wave of depolarisation - this travels down the bundle of His and Purkyne fibers causing the ventricles to contract - cells repolarise and the cardiac muscles relax

Question 38

theres a short delay before the AVN's wave of depolarisation. how is this helpful

Answer 38

allows the atria to fully pump out the blood into the ventricles

Question 39

in which direction to the ventricles contract and why

Answer 39

apex up which forces all of the blood out

Question 40

describe the sympathetic nervous system

Answer 40

activate fight or flight response such as increasing heartrate

Question 41

describe the parasympathetic nervous system

Answer 41

part of your autonomic nervous system, slows heart rate

Question 42

which receptors detect high and low blood pressure

Answer 42

baroreceptors

Question 43

what happens once high blood pressure is detected by baroreceptors

Answer 43

- impulse is sent from the medulla alone the parasympathetic neurones to the SAN - neurotransmitter acetylcholine is released - heart rate slows down and blood pressure decreases

Question 44

what happens once low blood pressure is detected by baroreceptors

Answer 44

- impulse is sent from the medulla alone the sympathetic neurones to the SAN - neurotransmitter noradrenaline is released - heart rate gets faster and blood pressure increases

Question 45

what kind of receptors respond to low/high O2/CO2

Answer 45

chemoreceptors - CO2 + H2O -> carbonic acid and lactic acid from anaerobic respiration effect pH

Question 46

what happens once low O2/ high CO2 (pH) is detected by chemoreceptors

Answer 46

- impulse is sent from the medulla alone the parasympathetic neurones to the SAN - neurotransmitter acetylcholine is released - heart rate slows, CO2 decease and O2 increases

Question 47

what happens once high O2/ low CO2 (pH) is detected by chemoreceptors

Answer 47

- impulse is sent from the medulla alone the sympathetic neurones to the SAN - neurotransmitter noradrenaline is released - heart rate rises, O2 decease and CO2 increases

Question 48

what happens if blood pressure remains too high

Answer 48

damage to the walls of the arteries

Question 49

what happens if blood pressure remains too low

Answer 49

insufficient blood supply to respiring cells: - not enough O2 for aerobic respiration (anarobic + lactic acid bulid up) low pH = denatures enzymes - no removal of waste - CO2 and H2O caused the production of carbonic acid low pH = denatures enzymes

Question 50

describe dendrites

Answer 50

carry action potentials to surrounding cells

Question 51

describe the axon

Answer 51

conductive, long fibre that carries the nervous impulse along the neurone

Question 52

describe the structure of a Schwann cell

Answer 52

cell that wraps around the axon