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A-level Biology > Chapter 14 > Flashcards

Chapter 14 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
Q

What’s the peripheral nervous

A

Receptors

Sensory and motor neurones

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26
Q

What’s the central nervous system

A

Coordination centres

E.g. brain + spine

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27
Q

How can a response be triggered

A

Each re

each receptor respond only to
specific Stimuli. Stimulation of receptor cells leads to establishment of generator potential → can cause response.

28
Q

What do pacinian corpuscle respond to

A

Pressure changes

29
Q

What is the stimulus of a pacinian corpuscle

A

Pressure

30
Q

Where do pacinian corpuscle occur

A

Deep in skin (e.g. fingers and feet)

31
Q

What do pacinian corpuscle consist of

A

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
Q

What do the membranes surrounding sensory neurones in pacinian corpuscle

A

Stretch mediated Na channels

33
Q

What do stretch-mediated Na channels do in pacinian corpuscle

A

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
Q

Why can’t Na+ be diffused into the Na+ channels in the pacinian corpuscle when no pressure is applied

A

In resting state, Na+ channels too narrow for Na+ to diffuse into sensory neurone only- resting potentials maintained.

35
Q

What happens when pressure is applied to pacinian corpuscle

A

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
Q

What stimulus do rod + cone cells respond to

A

Light

37
Q

Where are rod and cone cells found

A

On the human retina

38
Q

Why do rod cells produce black and white images

A

They cannot distinguish between different wavelengths of light

39
Q

Why can rod cells detect light at low light intensities

A

Because many rod cells connect to one sensory neurone wrapped- retinal convergence

40
Q

What must happen in rod cells to generate an action potential

A

Rod cell absorb light (if light intensity , Pigment rhodopsin broken down by light energy

There’s enough light energy from low-intensity light to cause the breakdown.

It’ll breakdown rhodopsin, enough pigment must be broken down for the threshold in bi polar cell to trigger an action potential

41
Q

What’s a bipolar cell

A

Cells that link rod cell to sensory neurone

42
Q

Why can the threshold in a sensory neuron needed trigger an action potential be reached even in low light intensities.

A

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
Q

Why are we able to see in black and white in the dark

A

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
Q

Disadvantage of rod cells

A

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
Q

How many different types of Cone cells are there

A

3 - each differing but the colour pigment they have (red, green, blue)

All absorb different wavelengths of light

46
Q

Why can we see more than the 3 colours of the 3 types of cone cells

A

Depending on proportion of each cone cell that’s stimulated we perceive colour images

47
Q

Why can we only see in colours when it’s bright

A

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
Q

In cone cells why is there no spacial summation or retinal convergence

A

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
Q

Advantage of cone cells

A

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
Q

What is the name of where light is focused by the lens on the retina

A

Fovea

51
Q

Why does the fovea receive the high test intensity of light

A

As light is focused by lens on part of retina opposite pupil, which is the fovea

52
Q

What is the explanation for the uneven distribution of rod and cone cells on the fovea

A

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
Q

At the fovea, what is the name of the highest number of photoreceptor cells

A

Cone cells

54
Q

How quickly the SAN releases the wave of depolarisation is controlled by what system

A

The nervous system

55
Q

What does SAN stand fro

A

Sino atrial node

56
Q

Where is the SAN located and what is it also known as

A

Right atrium

Pace maker

57
Q

Where are the purkyne fibres located

A

In the walls of the ventricles

58
Q

Where does the bundle of HIS run through

A

Through the septum

59
Q

Where is the AVN located

A

Located near the border of right + left ventricle within the atria still

60
Q

What does AVN stand for

A

Atrio ventricular node

61
Q

What is the rate of contraction controlled by

A

The wave of electrical activity

62
Q

Why is the cardiac muscle described as myogenic

A

It contracts on its own accord

63
Q

Where is the medulla oblongata located

A

In the brain

64
Q

What does the medulla oblongata do and how does it do it

A

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
Q

How does the heart control + coordinate the regular contraction of atria and ventricles

A

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
Q

How CO2 conc is restored to normal in the blood

A

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 (15 decks)

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