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A Level Biology > 6A Stimuli and Response > Flashcards

6A Stimuli and Response Flashcards

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1
Q

Myogenic

A

Contract and relax without receiving signals from nerves

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2
Q

How is the regular heartbeat maintained?

A

Through the pattern of contractions of the heart

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3
Q

SAN

A

Sinoatrial node

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4
Q

Where is the SAN?

A

In the wall of the right atrium

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5
Q

How does the SAN act like a pacemaker?

A

It sends out regular waves of electricity to the atrial walls

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6
Q

What prevents the wave of electricity in the heart from being passed from the artia to the ventricle?

A

Non-conducting collagen tissue

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7
Q

Where are the waves of electrical impulses transferred to from the SAN?

A

The AVN

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8
Q

AVN

A

Atrioventricular node

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9
Q

What does the AVN do?

A

It passes the electrical impulses to the bundle of His

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10
Q

What is the bundle of His?

A

In the heart, a group of muscle fibres that are responsible for conducting waves of electrical impulses between the ventricles to the apex (bottom) of the heart

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11
Q

What does the bundle of His split into?

A

Thinner muscle fibres in the left and right ventricle walls called Purkyne Tissue

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12
Q

What does the Purkne Tissue do?

A

Carries the waves of electrical impulses to the muscular walls of the right and left ventricles, causing them to contract simultaneously from the bottom upwards.

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13
Q

Why is there a slight delay before the AVN reacts?

A

To make sure the atria have emptied before they contract

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14
Q

What part of the brain unconsciously controls the rate at which the SAN fires ?

A

The medulla oblongata

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15
Q

What receptors deal with blood pressure?

A

Baroreceptors

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16
Q

What receptors detect the concentration of oxygen and carbon dioxide in the blood?

A

Chemoreceptors

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17
Q

If a high blood pressure is detected by the baroreceptors, what happens?

A

Impulses are sent to the medulla oblongata. The Medulla sends impulses down the parasympathetic neurones. They secrete acetylcholine (neurotransmitter) which binds to receptors on the SAN

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18
Q

If a low blood pressure is detected by baroreceptors, what happens?

A

Impulses are sent to the medulla, which sends impulses down the sympathetic neurones. These secrete noradrenaline (a neurotransmitter) which binds to receptors on the SAN

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19
Q

What happens if a high concentration of oxygen is detected by chemoreceptors?

A

Impulses are sent to the medulla, which sends impulses through the parasympathetic neurones. These secrete acetylcholine which binds to receptors on the SAN

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20
Q

What happens if a kow concentration of carbon dioxide is detected by the chemoreceptors?

A

Impulses are sent to the medulla, which sends impulses through the parasympathetic neurones. These secrete acetylcholine which binds to receptors on the SAN

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21
Q

What happens if a high pH is detected by the chemoreceptors?

A

Impulses are sent to the medulla, which sends impulses through the parasympathetic neurones. These secrete acetylcholine which binds to receptors on the SAN

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22
Q

What happens if a low concentration of oxygen is detected by the chemoreceptors?

A

Impulses are sent to the medulla, which sends impulses through the sympathetic neurones. These secrete noradrenaline which binds to receptors on the SAN

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23
Q

What happens if a high concentration of carbon dioxide is detected by the chemoreceptors?

A

Impulses are sent to the medulla, which sends impulses through the sympathetic neurones. These secrete noradrenaline which binds to receptors on the SAN

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24
Q

What happens if a low pH is detected by the chemoreceptors?

A

Impulses are sent to the medulla, which sends impulses through the sympathetic neurones. These secrete noradrenaline which binds to receptors on the SAN

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25
Q

Stimulus

A

A change in the environment that can be detected by an organism

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26
Q

Receptor

A

An organ specialised to detect a change in the internal or external environment

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27
Q

Taxis

A

A response that involves movement in a specific direction

28
Q

Positive taxis

A

Movement towards a stimulus

29
Q

Negative taxis

A

Movement away from a stimulus

30
Q

Kinesis

A

Movement in random directions

31
Q

Why is kinesis carried out?

A

To increase the chance of reaching different conditions more quickly. E.g Increasing speed and direction changes will increase the speed of a woodlouse finding a damp and dark region

32
Q

What is an auxin?

A

A plant hormone

33
Q

What is the auxin called that controls tropisms- (growth responses)

A

IAA

34
Q

How does IAA effect parts of the plant?

A

Elongates the plant cells on the shoots so the shoot can bend or grow. Inhibits growth of the root cells

35
Q

What is the reflex arc?

A

Stimulus, Receptor, Sensory Neurone, Intermediate Neurone, Motor Neurone, Effector, Response

36
Q

What is the name for the pressure receptor in your skin?

A

Pacinian Corpuscle

37
Q

What happens when a receptor is in its resting state?

A

There’s a voltage across the membrane (potential difference) as there is a difference in charge between the inside and the outside of the cell

38
Q

Resting potential

A

When a receptor is at its resting state

39
Q

What happens when a stimulus is detected by the receptor?

A

The membrane of the cell becomes more permeable and ions can move in or out of the cell (change in potential difference)

40
Q

Generator potential

A

The change in potential difference of a cell due to a stimulus

41
Q

Action potential

A

If the generator potential is big enough, an action potential is triggered, and sends an electrical impulse down the sensory neurone

42
Q

How is the strength of the stimulus detected?

A

Action potentials are all one size, so it is the frequency of the action potentials that determine the strength

43
Q

What type of receptors is the Pacinian Corpuscle?

A

Mechanoreceptors

44
Q

Describe the structure of the Pacinian Corpuscle

A

Sensory nerve ending wrapped in lots of layers of connective tissue called lamellae

45
Q

What happens when the Pacinian Corpuscle is stimulated?

A

The lamellae are deformed and press on the sensory nerve ending. This causes the sensory neurone’s cell membrane to stretch, deforming the stretch-mediated sodium ion channels. The channels open, and sodium ions can diffuse into the cell, creating a generator potential

46
Q

How does light enter the eye?

A

Through the pupil. The amount of light is controlled by the iris

47
Q

How are light rays focused onto the retina in the eye?

A

By the lens

48
Q

Where are photoreceptors in the cell?

A

The retina, but mostly concentrated on the fovea

49
Q

How are nerve impulses carried from the retina to the brain?

A

By the optic nerve

50
Q

Where is the blind spot in the eye?

A

Where the optic nerve leave the eye because there are no photoreceptors present

51
Q

How do photoreceptors convert light into electrical impulses?

A

Light hits the photoreceptors and is absorbed by light sensitive optical pigments. Light bleaches the pigments, causing a chemical change, and altering the membrane permeability to sodium ions. A generator potential is created, and if the threshold is reached, an impulse is sent along a bipolar neurone

52
Q

Bipolar neurone

A

Connects photoreceptors to the optic nerve

53
Q

What are the two types of photoreceptors in the eye?

A

Rods and Cones

54
Q

Where are the rods found?

A

In the peripheral parts of the retina

55
Q

Where are the cones found?

A

Packed together in the fovea

56
Q

What colours can rods detect?

A

Only black and white (monochromatic)

57
Q

What colours can cones detect?

A

Colour (trichromatic)

58
Q

How many types of cone cells are there and what do the detect?

A

3 (trichromatic). One of each type- red sensitive, blue-sensitive, green-sensitive

59
Q

How do you see different colours?

A

When the three different optical pigments in the cone cells are stimulated in different amounts

60
Q

Why are rods more sensitive to light?

A

Many rods are attached to one neurone, so many weak generator potentials can combine into one to make the threshold and create an action potential

61
Q

Why are cones less sensitive to light?

A

Only one cone is joined to one neurone, so more light is needed to generate a big enough generator potential and reach the threshold to make an action potential

62
Q

Why do rods give a low visual accuracy?

A

Many rods are joined to the same neurone, so light from two points close together can’t be told apart

63
Q

Why do cones give high visual accuracy?

A

Cones are close together and one cone joins to one neurone, so light from two points will trigger two action potentials

64
Q

Somatic nervous system

A

Voluntary nervous system

65
Q

Autonomic nervous system

A

Involuntary nervous system

A Level Biology (10 decks)

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