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Flashcards in Response to stimuli Deck (20)
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1

tropism

the response of a plant to a directional stimulus

2

2 x Growth factor examples

auxin (IAA) - cell elongation
giberellins - germination and flowering

3

Describe growth factors

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

4

IAA and phototropism in shoots

moves to the shaded side and promotes cell elongation
so the shoot grows towards the light

5

IAA and phototropism in roots

shaded side and inhibits growth
so shoots grow away from light

6

What is the purpose of Kinesis and Taxis?

keeps mobile organisms in favourable conditions

7

Taxes

moves towards or away from a directional stimulus

8

Kinesis

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

9

Reflex

rapid response to a stimulus without conscious control

10

What effector controls blinking?

orbiculosis oculi muscle

11

What are the advantages of reflex action?

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

12

Describe the process of the pacinian corpuscle response?

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

13

How is an action potential created in The Human Eye?

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

14

Describe Rods

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

15

Describe Cones

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

16

Describe the control of heart rate

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

17

Describe the left ventricle

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

18

What nervous system is responsible for changing the Heart Rate?

autonomic

19

slow down heart rate

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

20

speed up heart rate

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