Response To Stimuli

Question 1

What is an effector

Answer 1

A range of different cells, tissue , organs or organ system that carry out a response

Question 2

What is a stimuli

Answer 2

Detectable change in the internal or external environment

Question 3

What is a receptor

Answer 3

Cells or organs that detect specific stimuli

Question 4

What is Kineses

Answer 4

Non directional random response to an unpleasant stimuli
Changes speed of movement and rate of change of direction
More unpleasant the stimuli the more changes of direction

Question 5

What is a coordinator

Answer 5

An intermediary between a receptor and an effector which formulates a suitable response to a stimuli

Question 6

What is taxis

Answer 6

A simple response whose direction is determined by the direction of the stimulus

Question 7

What is taxis

Answer 7

A simple response whose direction is determined by the direction of the stimulus
Move towards stimulus is positive taxis
Move away from stimulus is negative taxis

Question 8

Why do organisms respond to a stimulus

Answer 8

More chance of finding and staying in favourable conditions so increasing chance of survival so greater chance of successful reproduction
So greater chance if beneficial alleles being passed on to the next generation

Question 9

What is a tropisum

Answer 9

Plant growth in response to directional stimulus
Posssitve - towards
Negative - away from stimulus

Question 10

What type of tropisums are involved in plant shoot growth

Answer 10

Positive phototropism - plants grow towards the sun
Negative geotropisum

Question 11

What type of tropisum are involved in plant root growth

Answer 11

Positive geotropisum - to root the plant and stop it falling over
Negative phototropism
Positive hydro tropisum - for water in light dependant reaction

Question 12

What do plant growth factors do

Answer 12

Cause cells to elongate

Question 13

Describe auxin production. Phototropism

Answer 13

Auxins produced in the tip diffuse down the tip
Light causes it to move to the shaded side and concentration is greater on the shaded side
Attaches to receptors on the cell membrane
Releasing H+ions to decrease pH breaking bonds in the micro fibrils in the cellulose wall so they stretch easier
Shaded region grow faster and shoot bends towards the light

Question 14

Describe geotropisum in the root

Answer 14

Auxins produced in the tip diffuse down the root
Gravity causes them to move to the bottom of the root
Concentration is higher at the bottom of the root
They attach to receptors on cell membrane
Lower side grows slower
Top side grows faster and roots bend towards the centre of the earth

Question 15

Why didn’t the shoot grow so much after the tip had been cut off and then replaced

Answer 15

Replacing the cut off tip limits the growth because the phloem is damaged and hormones are unable to flow easily

Question 16

If the was cut off and replaced with agar jelly soaked in the tip why did the shoot still grow

Answer 16

Because chemicals from the tip and moved into the agar jelly
This proves chemicals are responsible for growth

Question 17

If an agar jelly soaked in the tip Is placed in the shoot at an angle why does the shoot still curve in the dark

Answer 17

The part with the agar jelly has a higher concentration of auxins so it elongates faster causing the shoot to bend

Question 18

What is a sensory neuron

Answer 18

Carries nervous impulses from receptor towards CNS

Question 19

What is the voluntary nervous system

Answer 19

Carries nervous impulses to body muscles under concious control

Question 20

What is a motor neuron

Answer 20

Carries nervous impulses away from CNS to effector

Question 21

What is the CNS

Answer 21

Brain and spinal cord

Question 22

What is the autonomic nervous system

Answer 22

Carries nervous impulses to glands , smooth muscles and cardiac muscles

Question 23

What is peripheral nervous system

Answer 23

Made up from pairs of nerves from brain or spine

Question 24

Describe the reflex arc

Answer 24

Stimuli - heat from an object
Receptor- temperature receptor generates nervous impulses
Sensory neuron - passes nerve impulses to spin
Intermediate neuron - links sensory neuron to motor neuron
Motor neuron- carries nerve impulses from spine to arm muscle
Effector - muscle is stimulated and contacts
Response - pulling hand away

Question 25

What are the pacinian corpuscle

Answer 25

Transducers converting pressure energy into electro chemical energy Produces a generator potential which is large enough to make an action potential

Question 26

How do graded responses work in the pacinian corpscule

Answer 26

The greater the pressure the greater the frequency of impulses along the neurone The shape changes causing stretch mediated sodium ion channels to open and sodium ions diffuse down their conc gradient This creates a generator potential which if big enough makes an action potential

Question 27

Describe the structure of the pacinian corpuscle

Answer 27

Sensory neuron covered in myelin sheath for insulation to reduce sensitivity Layers of lamellla

Question 28

What are rods

Answer 28

sensitive to low light intensity and can distinguish between light and dark in dim lights They are so sensitive that they respond with only one photon Rods do not do colour

Question 29

What are cones

Answer 29

Sensitive to different wave lengths so can distinguish colour Human eye had three types cones responding to either red blue or green light

Question 30

Why do rods only let us see in black and white

Answer 30

Multiple rod cells connected to one bipolar cell so threshold is exceeded easier to break down pigment in lower light intensity

Question 31

Why do cones allow us to look at colour but not in low light

Answer 31

Each cone cell has its own bipolar cell so generator doesn’t get high enough as easily so pigments don’t break down as easy If adjacent cones are stimulated at the same time then because they have different bipolar cells they have separate impulses sent to the brain showing the colours

Question 32

Why do cones allow us to look at colour but not in low light

Answer 32

Each cone cell has its own bipolar cell so generator doesn’t get high enough as easily so pigments don’t break down as easy If adjacent cones are stimulated at the same time then because they have different bipolar cells they have separate impulses sent to the brain showing the colours

Question 33

where are cones and rods distributed

Answer 33

cone cells are found at the fovea opposite the pupil because it recieves the most light intensity rod cells are found at the perpheries of the retina where the light intensity is lowest

Question 34

what is the sympathetic nervous system

Answer 34

stimulates effetcors and speeds up activity ( excersie / flight or fight )

Question 35

what is the parasympathetic nervous system

Answer 35

inhibits effectors and slows down activtiy conserve energy and replenish reserves

Question 36

how does the heart beat

Answer 36

electrical waves are generated in and sent out from sinoatrial node across atrium wall atrium wall contracts the atrioventricular septum is non conductivite to prevent it crossing to the ventricle impulses are sent down the bundle of his to the purkinjie fibres they spread from the apex up the ventricular walls

Question 37

why is the delay in the heart beat important

Answer 37

allows the atria to finish contracting before the ventricles start making it more efficiant