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A-level Biology > B14 Response To Stimuli > Flashcards

B14 Response To Stimuli Flashcards

1
Q

What are the photoreceptors in the eye called

A

Cone and rod cells

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2
Q

What is a stimuli

A

A detectable change in environment

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3
Q

What are stimuli detected by

A

Receptors

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4
Q

What are the 2 types of nervous systems

A

Peripheral - neurones and receptors

and

central - brain and spine

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5
Q

What does the stimulation of a receptor cell lead to

A

The establishment of a generator potential - can cause a response

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6
Q

What is the stimulus in a pacinian corpuscle?

A

Pressure

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7
Q

What do pacinian corpuscle respond to

A

Pressure changes

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8
Q

Where do pacinian corpuscle occur

A

Deep in skin e.g. fingers and feet

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9
Q

What does a pacinian corpuscle consist of

A

A singles sensory neurone wrapped with layers of tissue separated by gel

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10
Q

What do membranes surrounding sensory neurone have in pacinian corpuscle

A

Stretch mediated sodium channels

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11
Q

What happens to stretch mediated sodium channels in resting state

A

Channels too narrow for sodium ions to diffuse into sensory neurone - resting potential is maintained

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12
Q

What shape are rod cells

A

Rod shaped

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13
Q

What shape are cone cells

A

Cone shaped

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14
Q

What is the pigment in rod cells

A

Rhodopsin

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15
Q

What is the pigment in cone cells

A

Iodopsin

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16
Q

What colour images are formed by rod cells

A

Black and white images

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17
Q

What colour images are produced by cone cells

A

Coloured images

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18
Q

Why can we see even if it’s dark

A

Can see in black and white - survival mechanism

It doesn’t take a lot of light energy to break down rhodospin, so a generator potential can be established

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19
Q

What is visual acuity

A

The accuracy of vision in light intensity’s

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20
Q

What is the distribution if rod and cone cells in the retina

A

It’s uneven

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21
Q

Blind spot

A

Has no rod cells or cone cells, so there are no photoreceptors, no light can be detected at that particular point in the retina

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22
Q

What’s the steps in the reflex arc

A

Stimulus —> receptor —> coordinator —> effector —> response

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23
Q

What’s the advantage of responding to stimuli

A

Increase survival chances

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24
Q

What are the 2 types of nervous systems

A

Peripheral nervous system and central nervous system

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25
What’s the peripheral nervous
Receptors Sensory and motor neurones
26
What’s the central nervous system
Coordination centres E.g. brain + spine
27
How can a response be triggered
each receptor respond only to specific Stimuli. Stimulation of receptor cells leads to establishment of generator potential → can cause response.
28
What do pacinian corpuscle respond to
Pressure changes
29
What is the stimulus of a pacinian corpuscle
Pressure
30
Where do pacinian corpuscle occur
Deep in skin (e.g. fingers and feet)
31
What do pacinian corpuscle consist of
Single sensory neurone wrapped with layers of tissue separated by gel Has special channel proteins in its plasma membrane, containing channel proteins that allow ion transportation
32
What do the membranes surrounding sensory neurones in pacinian corpuscle
Stretch mediated Na channels
33
What do stretch-mediated Na channels do in pacinian corpuscle
Open + allow Na+ to enter sensory neurone only when they’re stretched and deformed. ( pressure must be applied) Are closed unless they’re stretched/pushed on to pull/stretch open the Na+ channels to allow Na+ to diffuse in
34
Why can’t Na+ be diffused into the Na+ channels in the pacinian corpuscle when no pressure is applied
In resting state, Na+ channels too narrow for Na+ to diffuse into sensory neurone only- resting potentials maintained.
35
What happens when pressure is applied to pacinian corpuscle
Pressure applied, deforms and stretches sensory neurone plasma membrane + widens Na+ channels, so Na+ diffuses in leading to establishment of a generator potential. Enough Na+ diffuse in, so can exceed the threshold + a response can occur as it has generated an action potential.
36
What stimulus do rod + cone cells respond to
Light
37
Where are rod and cone cells found
On the human retina
38
Why do rod cells produce black and white images
They cannot distinguish between different wavelengths of light
39
Why can rod cells detect light at low light intensities
Because many rod cells connect to one sensory neurone wrapped- retinal convergence
40
What must happen in rod cells to generate an action potential
Rod cell absorb light There’s enough light energy from low-intensity light to cause the breakdown. enough pigment must be broken down for threshold in bi-polar cell to trigger action potential
41
What’s a bipolar cell
Cells that link rod cell to sensory neurone
42
Why can the threshold in a sensory neuron needed trigger an action potential be reached even in low light intensities.
Many rod cells are connected to a single bipolar cell - spatial summation Also it doesn’t take a lot of light energy to break down rhodopsin
43
Why are we able to see in black and white in the dark
Survival mechanism Retinal convergence - have multiple rod cells connecting to one bipolar cell Advantage is special summation = each of rod cells in low light intensity, rhodopsin will be broken down + collectively, all broken down pigment will result in big enough stimulus to trigger and action potential.
44
Disadvantage of rod cells
Low visual acuity - don’t have very accurate vision in lower light intensities. And because of Retinal convergence the brain cannot distinguish between the separate light sources that stimulate it
45
How many different types of Cone cells are there
3 - each differing but the colour pigment they have (red, green, blue) All absorb different wavelengths of light
46
Why can we see more than the 3 colours of the 3 types of cone cells
Depending on proportion of each cone cell that’s stimulated we perceive colour images
47
Why can we only see in colours when it’s bright
Because iodopsin only broken down if theres high light intensity, so they require more light energy to break down the pigment so action potentials can only be generated with enough light
48
In cone cells why is there no spacial summation or retinal convergence
Only 1 cone cell connects to a bipolar cell, no spacial summation occurs + cones can only respond to high light intensity, which is why we can’t see colour in the dark.
49
Advantage of cone cells
each cone cell is connected to 1 bipolar cell, so the brain can’t distinguish between separate sourced of light detected. So cone cells have high visual acuity
50
What is the name of where light is focused by the lens on the retina
Fovea
51
Why does the fovea receive the high test intensity of light
As light is focused by lens on part of retina opposite pupil, which is the fovea
52
What is the explanation for the uneven distribution of rod and cone cells on the fovea
Most cone cells near fovea as they only respond to high light intensities Rod cells further away as these can respond to low light intensities
53
At the fovea, what is the name of the highest number of photoreceptor cells
Cone cells
54
How quickly the SAN releases the wave of depolarisation is controlled by what system
The nervous system
55
What does SAN stand fro
Sino atrial node
56
Where is the SAN located and what is it also known as
Right atrium Pace maker
57
Where are the purkyne fibres located
In the walls of the ventricles
58
Where does the bundle of HIS run through
Through the septum
59
Where is the AVN located
Located near the border of right + left ventricle within the atria still
60
What does AVN stand for
Atrio ventricular node
61
What is the rate of contraction controlled by
The wave of electrical activity
62
Why is the cardiac muscle described as myogenic
It contracts on its own accord
63
Where is the medulla oblongata located
In the brain
64
What does the medulla oblongata do and how does it do it
Controls the HR Via autonomic nervous system Sympathetic nervous system linked to SAN that increases HR Parasympathetic nervous system that is linked to the SAN decreases HR
65
How does the heart control + coordinate the regular contraction of atria and ventricles
SAN releases wave of depolarisation (WOD) across the atria, causing atria to contract (atrial systole). AVN will release another WOD when 1st WOD reaches it . There’s a non-conductive layer between atria and ventricles which prevents WOD travelling down to ventricles. Instead bundle of HIS running through the septum can conduct and pass a WOD down septum + purkyne fibres in walls of ventricles. As result, apex + walls of ventricles contract. There’s a shirt delay before this happens whilst the AVN transmits the 2nd WOD. This allows enough time for atria to pump all blood into ventricles. Finally, cells repolarise and cardiac muscle relaxes.
66
How CO2 conc is restored to normal in the blood
Increased exercise, causes increase in respiration More CO2 produced by respiring tissues Increased CO2 in blood Blood pH decreases Chemoreceptors in carotid arteries increases frequency of impulses that it sends to the medulla oblongata. The centre in the medulla oblongata that increases HR increases freq that it sends impulses to SAN via sympathetic nervous system. SAN increases HR, so there’s increased blood flow to lungs More CO2 is removed faster Normal conc of CO2 in blood returns to normal.

A-level Biology (21 decks)

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