Response to stimuli

Question 1

tropism

Answer 1

the response of a plant to a directional stimulus

Question 2

2 x Growth factor examples

Answer 2

auxin (IAA) - cell elongation

giberellins - germination and flowering

Question 3

Describe growth factors

Answer 3

made in the growing regions
move short distances by diffusion and AT
long distances via the phloem

Question 4

IAA and phototropism in shoots

Answer 4

moves to the shaded side and promotes cell elongation

so the shoot grows towards the light

Question 5

IAA and phototropism in roots

Answer 5

shaded side and inhibits growth

so shoots grow away from light

Question 6

What is the purpose of Kinesis and Taxis?

Answer 6

keeps mobile organisms in favourable conditions

Question 7

Taxes

Answer 7

moves towards or away from a directional stimulus

Question 8

Kinesis

Answer 8

no directional stimulus - turns moves more to find more favourable area

Question 9

Reflex

Answer 9

rapid response to a stimulus without conscious control

Question 10

What effector controls blinking?

Answer 10

orbiculosis oculi muscle

Question 11

What are the advantages of reflex action?

Answer 11

get away from danger
fast
prevent harm
do not have to be learned

Question 12

Describe the process of the pacinian corpuscle response?

Answer 12

detects stimulus
pressure causes lamellae to deform
stretch mediated sodium ion channels ope
Na + diffuses into the neurone
greater the pressure the more ions open
depolarisation
if threshold is reached an action potential is initiated

Question 13

How is an action potential created in The Human Eye?

Answer 13

light is focused onto the retina by the lens
light is absorbed by pigments on the photo receptor
causes some sodium ion channels to open
if threshold is met then an action potential is generated

Question 14

Describe Rods

Answer 14

monochromatic
more sensitive to low light
low visual acuity
mostly in the peripheral of the retina

Question 15

Describe Cones

Answer 15

trichromatic
less sensitive to low light
higher visual acuity
each cone has it’s own bipolar neuron

Question 16

Describe the control of heart rate

Answer 16

SAN initiates the heartbeat
sends impulses across the atria, causing them to contract
non conductive tissue prevents the impulse from reaching the ventricles
AVN delays the impulse
AVN then sends the impulse down the Bundle of His to the Purkinje fibres
this causes ventricles to contract from the base up

Question 17

Describe the left ventricle

Answer 17

highest blood pressure
most cardiac muscle = greatest force
pumps blood to whole body

Question 18

What nervous system is responsible for changing the Heart Rate?

Answer 18

autonomic

Question 19

slow down heart rate

Answer 19

chemo/bororeceptors detect
send impulses medulla oblongata in the brain
parasympathetic neurones secrete acetylcholine
heart rate slows

Question 20

speed up heart rate

Answer 20

chemo/bororeceptors detect change 
impulses to the medulla oblongata 
impulses along sympathetic 
sympathetic neurones secrete noradrenaline 
heart rate speeds up