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biology > Response To Stimuli > Flashcards

Response To Stimuli Flashcards

1
Q

What is the basic sequence of response

A 
Stimulus
Receptor
Coordinator
Effector
Response
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2
Q

Define stimulus

A

Detectable change to environment

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3
Q

Define Effector

A

Cells that produce response

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4
Q

Define receptors

A

Cells that detect stimulus

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5
Q

What are the types of response in motile organisms

A

Taxis

Kineses

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6
Q

Describe taxis

A

Directional movement
In relation to stimulus
+ve is towards
-ve is away

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7
Q

Examples of taxis

A

+ve phototaxis of algae

+ve chemotaxis of bacteria to glucose

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8
Q

Describe kinesis

A

Changes to speed
Changes to rate of turns
Random and non-directional movement

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9
Q

Explain how kinesis works

A

Once in unfavourable conditions = many turns

Much time in unfavourable conditions= less turns and faster movement

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10
Q

Types of movement in Non-motile organisms

A

Tropism

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11
Q

Examples of tropism

A

Geotropism
Gravitropism
Phototropism

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12
Q

Use of tropism in shoots

A

+ve phototropism = more light for Photosynthesis

-ve geotropism= grows up towards light

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13
Q

Use of tropism in roots

A

+ve geotropism= grows down for support

+ve hydrotropism= water for Photosynthesis

-ve phototropism = grows down towards light

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14
Q

What chemicals are involved in tropism

A

Plant growth factors

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15
Q

What is the difference between plant growth factors and hormones

A

Made by cells throughout plant

May have effect on nearby cells

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16
Q

What does IAA stand for

A

Índoleacetic acid

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17
Q

Give examples of plant growth factors

A

Auxins

IAA

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18
Q

How does IAA work

A

Controls cell elongation in flowering plants

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19
Q

Describe how phototropism occurs in shoots

A 
IAA produced in shot tip
Travels down both sides evenly at first
IAA accumulates on shaded side
Increase IAA conc causes cells to elongate faster than on light side
Shoot grows towards light
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20
Q

What theory explains how IAA works

A

Acid growth hypothesis

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21
Q

Describe the acid growth hypothesis

A

IAA attaches to cell membrane
More H+ are Transported in cell wall
Decreased PH causes microfibrils to be stretched

More plasiticity= elongated

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22
Q

What is the response to touch called

A

Thigmotropism

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23
Q

Describe the effect of IAA on roots

A

Produced in tip
Diffuse down sides evenly
Accumulate on lower side due to gravity
IAA inhibits elongation

Upperside grows quicker than lowerside

Grows down

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24
Q

What is the spinal cord made up of

A

Pairs of motor and sensory neurons entering and leaving

Intermediate neurons within

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25
Q

What is the coordinator in a reflex arc

A

Intermediate neuron

26
Q

Why are reflex arcs important

A

Prevent tissue damage
Allow brain to carry out more complex responses
Very quick
Don’t have to be learnt

27
Q

Why are reflexes so quick

A

Very few neurons involved

28
Q

What are the features of receptors

A

Specific to one stimulus

Transducers (convert energy from one form to another)

29
Q

What must occur for an action potential to be generated

A

Generator potential must exceed threshold

30
Q

What do pacinian corpuscles respond to

A

Mechanical pressure

31
Q

What is a graded response

A

Where increase in stimulus causes increase in generator potential frequency of action potentials

32
Q

Describe the structure of the pacinian corpuscles

A

Neuron end with ending surrounded by layers of connective tissue with viscous gel between layers

33
Q

Describe what occurs what pressure is applied to a pacinian corpuscles

A

Layers of tissue deform
Neuron membrane is stretched causing strech mediated sodium ion channel to open
Na+ Diffuse in
Membrane is de polarised
Generator potential created
If exceeds threshold then action potentials produced

34
Q

What is an action potential

A

Nervous impulse

35
Q

Describe why pacinian corpuscles have a graded response

A

Larger pressure= Larger deformity of membrane = Larger polarisation = Larger generator potential= increase frequency of action potentials

36
Q

What receptors are present in the eye

A

Rods and cones

37
Q

Where are Rod cells found

A

At periphery only

38
Q

Describe and explain the visual acuity of rod cells

A

Low visual acuity due to retinal convergence (multiple rod cells conected to same bipolar neuron and ganglion cell)

39
Q

Describe and explain the sensitivity to low light intensity of rod cells

A

Very sensitive due to summation

Generator potentials added up due to retinal convergence so more likely to surpass threshold

40
Q

Describe and explain visual acuity of cone cells

A

High because each cone cell is attached to one neuron

41
Q

Describe and explain the sensitivity to low intensities of light in cone cells

A

Poor

No retinal convergenc so larger stimulus need to surpass threshold

42
Q

Are Rod or cone cells more abundant

A

Rod

43
Q

How many types of rod cells are there

A

One

44
Q

How many types of cone cells are there

A 
3
Red
Blue
Green
Light detection
45
Q

Where are cone cells found

A

Mainly at fovea some at periphery

46
Q

What parts of the nervous system control heart rate

A

Periphery nervous system
Autonomic
Sympathetic and parasympathetic

47
Q

Define myogenic

A

Initiated within the muscle

48
Q

Describe how a heart beat is started

A

Wave of electrical excitement starts from SAN
Move across atria walls causing contraction
AVseptum prevents waves entering ventricles
After delay wave eminates from AVN down bundle of his and purkinji fibres
Ventricles contract from apex up

49
Q

What does SAN stand for

A

Sino atrial node

50
Q

Where is the SAN

A

Right atrium wall

51
Q

What does AVN stand for

A

Atrioventricular node

52
Q

What is the AV septum

A

Non conductive tissue seperating atrium and ventricles

53
Q

Where is the AVN found

A

Right atrium walls

54
Q

Where are chemo receptors found

A

Carotid artery walls

55
Q

What do chemo receptors respond to

A

Changes in PH

56
Q

Describe how chemo receptors respond to decreased PH

A

Chemo receptors increase frequency of nervous impulses to accelatory centre in medulla oblognata
Increase in waves down Sympathetic nerves
More electrical waves emitted from SAN
Increased heart rate and blood flow
Carbon dioxide concentration decreases
PH increases

57
Q

What is the alternative name for pressure receptors

A

Baro receptors

58
Q

Where are pressure receptors found

A

Carotid artery walls

And aorta

59
Q

What are carotid arteries

A

Arteries leading to brain

60
Q

How do pressure receptors respond to increased blood pressure

A

More impulses to inhibitory centre in medulla oblognata

More pulses via parasympathetic nerves

Less waves from SAN

Reduced heart rate

61
Q

How do barorecptors respond to decreased blood Pa

A

More impulses to accelatory centre in medulla oblognata

More pulses via sympathetic nerves

More waves from SAN

Increased heart rate

biology (28 decks)

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