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AQA A-Level Biology 5-8 > 6.1 Detection and Response > Flashcards

6.1 Detection and Response Flashcards

1
Q

What is a stimulus?

A

A change in the environment

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2
Q

What is a receptor?

A

A cell or group of cells that detects the stimulus

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3
Q

What is an effector?

A

The structure that brings about the response to the stimulus change

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4
Q

What are the prefixes indicating the stimulus changes?

A 
Photo - light
Hydro - water
Geo - gravity 
Thermo - heat
Hygro - humidity 
Rheo - water currents
Chemo - chemical 
Anemo - air current
Baro - pressure
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5
Q

What is the stimulus response process?

A 
Stimulus 
Receptor
Coordinator
Effector
Response
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6
Q

What are the three types of response?

A

Taxes
Kineses
Tropisms

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7
Q

If a questions says what type of behaviour is shown - what do you put?

A

Either taxis, kinesis or tropism

Nothing else

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8
Q

What is taxes?

A

Movement in a specific direction that are directed by a stimulus such as light or food

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9
Q

Examples of taxes?

A

Euglena - shows positive phototaxes useful in photosynthesis

Earth worm - responds to water, gravity, light

Some bacteria - move to regions of high glucose concentration = positive chemotaxis

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10
Q

What is kineses? Example?

A

More random movements that are not directed by a stimulus

Eg
Woodlice (prone to desiccation) - move randomly to find dark when in the light
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11
Q

What is tropisms? Example?

A

A growth movement of part of a plant in response to a directional stimulus

Roots - positive hydrotropism
Shoots - initially negative phototropism (as no light in soil)

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12
Q

When should a response be deemed positive or negative?

A

Taxes and tropisms are positive and negative

Whereas kineses can’t be positive or negative as it is random

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13
Q

In kineses when does an organism move more frantically?

A

The more unfavourable the stimulus the more rapidly the organism moves and the more frequently it changes direction

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14
Q

What are auxins?

A

Plant growth factors

NOT hormones

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15
Q

What is the most common auxin?

A

IAA

Indole-3-acetic acid

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16
Q

What is significant about the different parts of a plant?

A

They have different optimum auxin concentrations

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17
Q

What do the concentrations of auxins lead to in the stems and roots?

A

A high concentration of IAA in the stem stimulates growth (the cells don’t replicate but elongate the ones already there)

A high concentration of IAA in the roots inhibits growth

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18
Q

Why can growth be inhibited by too high a concentration of IAA?

A

As IAA is an acid it can denature the enzymes

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19
Q

Describe phototropism in flowering plants?

A

When reacting to sunlight

Cells in the tip of the shoot produce IAA
IAA is distributed evenly down the stem
The light causes the IAA to move to the ‘shaded’ side
A greater concentration of IAA causes cell elongation on the ‘dark’ side
The shades side grows faster so the shoot grows towards the light

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20
Q

How does elongation take place?

A

It activates a protein pump which lowers the pH
This activates an enzyme to break bonds in the cell wall - loosening the cell wall
So the shoot bends to the light

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21
Q

Describe geotropism in flowering plants?

A

When reacting to gravity

Cells in the tip of the root produce IAA
This settles at the bottom, no matter the branch
The greater concentration of IAA at the bottom causes cell elongation on the other side and bends down as a result (as high IAA in roots inhibits growth)

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22
Q

What happens if a tip of the shoot is covered or has been cut off?

A

It will grow normally with no directional response i.e straight up

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23
Q

What happens if a tip of the shoot is exposed with the rest buried in sand?

A

The shoot behaved as normal showing it was definitely the tip that caused the response to light

24
Q

What is the nervous system made up of?

A

The peripheral nervous system

The central nervous system

25
What is the central nervous system comprised of?
The brain | The spinal cord
26
What makes up the peripheral nervous system?
Sensory nervous system | Motor nervous system
27
What is involved in the motor nervous system?
Somatic (mostly voluntary) | Autonomic (mostly involuntary)
28
What is the autonomic aspect made up of?
Sympathetic - fight or flight Parasympathetic - rest and digest
29
Go through the reflex arc?
``` Stimulus Receptor Sensory neurone Intermediate neurone Motor neurone Effector Response ```
30
How are neurones drawn?
All neurones go into the grey matter with the intermediate neurone completely in there As a ball at the start then a line There’s a curve as though to fit the ball of the next neurone but not touching to show the synapse
31
When labelling a neurone what must you do?
Write the name and the label MUST be touching the neurone (not just ‘near’ it)
32
Why are reflex arcs important?
They protect the body from harmful stimuli They are fast They are involuntary They don’t involve the conscious part of the brain
33
What are effectors?
A muscle - contacts Or A gland - secretes
34
What is monosynaptic and polysynaptic? Significance?
Mono - only one synapse Poly - many synapses Mono synaptic responses are much quicker
35
What are some factors of sensory receptors?
All are specific to a single type of stimulus All produce a generator potential (start of a nerve impulse) by acting as a transducer
36
What are some examples of sensory receptors?
The pacinian corpuscle | The retina of the human eye
37
How does the pacinian corpuscle transduces the mechanical of a stimulus into a generator potential?
Putting pressure on the capsule all the consequent layers and gel are squished and forced together The pressure on the neurone ending causes the stretch mediated Na+ channels to open This causes an influx of Na+ using facilitated diffusion which changes the charge as there is now a greater positive charge in the neurone ending due to depolarisation Leading to a generator potential
38
What happens if there is a weaker stimulus on the pacinian corpuscle?
A weak stimulus isn’t registered due to not enough pressure therefore not enough stretching of the membrane Therefore no generator potential
39
What is the function of these in the eye? Choroid Fovea Optic nerve Retina
Choroid - absorbs light passed through the retina containing melanin and blood vessels Fovea - high density of cone cells Optic nerve - contains sensory neurones Retina - contains photoreceptors
40
What is the function of these in the eye? Lens Sensory ligaments and ciliary muscles Cornea Iris
Lens - made up of proteins Sensory ligaments and ciliary muscles - change the shape of the lens Cornea - main site of refraction Iris - controls the amount of light entering (using antagonistic muscle action)
41
What is involved in making up the retina?
Rod cells Cone cells Bipolar neurone Ganglion cells
42
Information about cone cells?
High in the fovea Iodopsin is the pigment that is broken down 3 types of iodopsin blue/green/red sensitive Each cone cell is connected to a separate bipolar neurone High visual acuity Low sensitivity in low light
43
Why do cone cells have high visual acuity?
Several stimuli hit each cone cell which is connected to a separate bipolar neurone So many individual impulses can be sent to the brain
44
Information about rod cells?
High in the side of eye Rhodopsin is the pigment that is broken down Many rod cells are connected to a each bipolar neurone Low visual acuity High sensitivity in low light
45
Why do rod cells have a high sensitivity in low light?
Many rod cells are stimulated per bipolar neurone allowing the threshold of neurotransmitter to be reached Therefore nerve impulses are transmitted to the brain along the optic nerve
46
Which of the pigments in rod/cone cells are more easily broken down?
Rhodopsin in rod cells
47
What happens to pigments when they are broken down?
They have lots of mitochondria allowing aerobic respiration to take place forming ATP The energy from ATP will used to resynthesise the pigment
48
What causes vision to be in colour?
Different wavelengths of light
49
Describe the events controlling the cardiac cycle?
Wave of excitation from SA node spreads across both atria so they contract and push blood into the ventricles Wave reaches AV node - along purkinje fibres of bundle of His Atria relax Wave reaches bottom of ventricles + contract from the bottom up - increased pressure causes AV valves to close Forces blood in pulmonary artery + aorta through SL valves Ventricles relax, pressure below aorta, SLV shut - then the cycle repeats
50
What are the sections of the brain we need to know?
Cerebral cortex - consciousnesses, intelligence, memory and language Cerebellum - coordinates movement and balance Medulla - controls automatic actions (heart beat and breathing)
51
How does heart rate increase?
Increased aerobic respiration leads to more CO2 production Carbonic acid in the blood leads to a decrease in pH detected by chemoreceptors in the aorta and carotid arteries A sensory neurone sends an impulse to the cardiac acceleratory centre in the medulla of the brain More impulses are sent down the sympathetic nerve to the SA node The cardiac muscle will contract more often
52
Why would heart rate decrease?
Decreased aerobic respiration leads to less CO2 production Less Carbonic acid in the blood leads to a increase in pH detected by chemoreceptors in the aorta and carotid arteries A sensory neurone sends an impulse to the cardiac inhibitory centre in the medulla of the brain Fewer impulses are sent down the parasympathetic nerve to the SA node The cardiac muscle will contract less often
53
What is the equation for cardiac output?
Cardiac output = stroke volume x heart rate
54
What happens when there is an decrease in blood pressure?
The baroreceptors in the aorta and carotid arteries detect the decrease in pressure A sensory neurone sends an impulse to the cardiac acceleratory centre in the medulla of the brain The impulse goes down the sympathetic nerve to the SA node The cardiac muscle will contract more often Leading to a faster heart beat
55
What happens when there is an increase in blood pressure?
The baroreceptors in the aorta and carotid arteries detect the change in pressure A sensory neurone sends an impulse to the cardiac inhibitory centre in the medulla of the brain The impulse goes down the parasympathetic nerve to the SA node The cardiac muscle will contract less often Leading to a slower heart beat
58
Explain an increase in pressure with more salt in the blood?
More salt = lower water potential So water moves in via osmosis Leading to an increase in volume and therefore increase in pressure

AQA A-Level Biology 5-8 (13 decks)

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