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Biology > Stimuli And Responses > Flashcards

Stimuli And Responses Flashcards

1
Q

What is a stimulus?

A

Any change in the internal or external environment

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2
Q

Taxis response is

A

Directional movement in response to a stimulus

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3
Q

Kinesis response is

A

Random, non directional movement in response to a stimulus

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4
Q

The job of sensory neurones

A

Sensory neurones transmit electrical impulses from receptors to the central nervous system

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5
Q

Job of motor neurones

A

Motor neurones transmit electrical impulses from the CNS to the effectors

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6
Q

Job or relay neurones

A

Relay neurones transmit electrical impulses between sensory neurones and motor neurones

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7
Q

Pathway of nervous communication

A 
Stimulus
Receptors
Sensory neurone
CNS
Motor neurone
Effector
Response
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8
Q

Reflex arc pathway

A 
Stimulus
Receptor
Sensory neurone
Relay neurone in spinal cord (skipping conscious part of brain, making it involuntary)
Effector
Response
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9
Q

If there’s a relay neurone involved in the simple reflex arc then it’s possible to override the reflex. True or false?

A

True, the brain can override it

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10
Q

Tropism is

A

The response of a plant to a directional stimulus

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11
Q

Positive tropism is

A

Growth towards the stimulus

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12
Q

Negative tropism is

A

Growth away from the stimulus

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13
Q

Phototropism in shoots

A

Grow and bend towards light

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14
Q

Phototropism in roots

A

Grown and bend away from light

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15
Q

Gravitropism in shoots

A

Grown and bend away from gravity

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16
Q

Gravitropism in roots

A

Grow and bend towards roots

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17
Q

Another name for gravitropism

A

Geotropism

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18
Q

Auxins stimulate growth in shoots but high concentrations inhibit growth in roots

A

Auxins stimulate growth in shoots but high concentrations inhibit growth in roots

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19
Q

What is IAA

A

A type of auxin

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20
Q

What does IAA do in shoots

A

Causes shoot to grow on the side that IAA is on

21
Q

What does IAA do to roots

A

Inhibits growth on the side that IAA is on

22
Q

How do auxins stimulate growth of shoots?

A

By cell elongation

23
Q

What is cell elongation?

A

Cell walls become loose and stretchy so the cell gets longer

24
Q

How do receptors j the nervous system covert the energy of the stimulus into electrical energy used by neurone

A

When a nervous system receptor is in its resting state there’s a difference in charge between the inside and the outside of the cell. The inside of the cell is negative and the outside of the cell is positive. This means there’s a potential difference across the membrane. This is the resting potential.
When a stimulus is detected the cell is excited and becomes more permeable, allowing more ions to move in and out of the cell, altering the potential difference. The inside of the cell becomes positive and the outside of the cell becomes negative. This is called the generator potential.
A bigger stimulus excites the membrane more, causing a bigger movement of ions and a bigger change in potential difference so a bigger generator potential is produced.
If the generator potential is big enough it’ll trigger an action potential. An action potential is only triggered if the generator potential reaches the threshold level

25
Q

How are the strength of action potentials measured?

A

Action potentials are all one size so the strength of the stimulus is measured by the frequency of action potentials

26
Q

Where are pacinian corpuscles found?

A

The skin

27
Q

Which stimuli do pacinian corpuscles detect?

A

Mechanical stimuli (e.g. Pressure and vibrations)

28
Q

What happens when a pacinian corpuscle is stimulated?

A

The lamellae are deformed and press on the sensory nerve ending. This causes the sensory neurones cell membrane to stretch, deforming the stretch mediated sodium ion channels. The channels open and sodium ions diffuse into the cell, creating a generator potential. If the generator potential reaches the threshold it triggers an action potential

29
Q

Describe the structure of pacinian corpuscles

A

Pacinian corpuscles contain the end of a sensory neurone called a sensory nerve ending. The sensory nerve ending is wrapped in loads of layers of connective tissue called lamallae

30
Q

How do parts of the eye work?

A

Light enters the eye through the pupil. The amount of light that entered is controlled by the muscles of the iris. Light rays are focused by the lens onto the retina, which lines the inside of the eye. The retina contains photoreceptor cells - these detect light. The fovea is an area of the retina where there are lots of photoreceptors. Nerve impulses from the photoreceptor cells are carried from the retina to the brain by the optic nerve, which is a bundle of neurones. Where the optic nerve leaves the eye is called the blind spot - there aren’t any photoreceptor cells, so it’s not sensitive to light

31
Q

How do photoreceptors work?

A

Light enters the eye, hits the photoreceptors and is absorbed by light sensitive optical pigments. Light bleached the pigments, causing a chemical change and altering the membrane permeability to sodium ions. A generator potential is created and if it reaches the threshold, a nerve impulse is sent along a bipolar neurones. Bipolar neurones connect photoreceptors to the optic nerve, which takes impulses to the brain

32
Q

Two types of photoreceptors

A

Rods and cones

33
Q

Where are rods located within the eye?

A

Peripheral parts of the retina

34
Q

Where are cones found within the eye?

A

Packed together in the fovea

35
Q

Why are rods and cones sensitive to different wavelengths of light

A

They contains different optical pigments

36
Q

What vision do rods provide

A

Monochromatic vision - only gives information in black and white

37
Q

What vision do cones provide?

A

Trichromatic vision - only gives information in colour. There are three types of cone: red sensitive, green sensitive and blue sensitive. To see different colours they are stimulated in different proportions

38
Q

Why can rods fire action potentials in dim light?

A

They are sensitive to light. Three rods join to one neurone meaning mant weak generator potentials combine to reach the threshold and trigger an action potential

39
Q

Why can’t cones fire action potentials in dim light?

A

Cones are less sensitive to light. One come joins to one neurone so it takes more light to reach the threshold and trigger an action potential

40
Q

Why do rods have a low visual acuity?

A

Rods give a low visual acuity because many rods join the same neurone, which means light from two points close together cannot be told apart

41
Q

Why do cones give a high visual acuity?

A

Cones give a high visual acuity because cones are close together and one come joins one neurone. When light from two points hits two cones two action potentials go to the brain so the points can be distinguished despite being close together

42
Q

The heart is myogenic, what does this mean?

A

It can contract and relax without receiving signals from nerves

43
Q

How does the heart beat?

A

The Soniatrial node sets the rhythm of the heartbeat by sending regular waves of electrical activity to the atrial walls. This causes the right and left atria to contract at the same time. A band of non conducting collagen tissue prevents the waves of electrical activity from being passed directly from the atria to the ventricles. Instead the waves of electrical activity are transferred from the sinoatrial node to the atrioventricular node. There is a slight delay while the atria empty before the atrioventricular node passes the waves of electrical activity on to the bundle of His. The bundle of His conduct the waves of electrical activity between the ventricles and the apex of the heart. The purkyne tissue carry waves of electrical activity into the muscular walls of ventricles causing them to contract simultaneously

44
Q

What controls the sinoatrial node?

A

Medulla oblongata

45
Q

How does the body respond to high blood pressure?

A

The baroreceptors detect high blood pressure. Impulses are sent to the medulla which sends impulses along parasympathetic neurones. These secrete acetylcholine which binds to receptors on the sinoatrial node. This effects the cardiac muscles and the heart rate slows down to reduce blood pressure back to normal

46
Q

How does the body respond to low blood pressure?

A

Baroreceptors detect low blood pressure. Impulses are sent to the medulla which sends impulses along sympathetic neurones. These secrete noradrenaline which binds to receptors on the sinoatrial node. This affects the cardiac muscles. The heart rate speeds up to increase blood pressure back to normal

47
Q

How does the body respond to high pH levels?

A

Chemoreceptors detect chemical changes in the blood. Impulses are sent to the medulla which sends impulses along parasympathetic neurones. These secret acetylcholine which binds to receptors on the sinoatrial node. This affects the cardiac muslces. Heart rates decreases to return pH levels back to normal

48
Q

How does the body respond to low pH levels?

A

Chemoreceptors detect chemical changes in the blood. Impulses are sent to the medulla which sends impulses along sympathetic neurones. These secrete noradrenaline which binds to receptors on the sinoatrial node. This affects the cardiac muscles. The heart rate increase to return pH levels back to normal

49
Q

How does CO2 affect pH levels?

A

High CO2 = low pH

Low CO2 = high pH

Biology (15 decks)

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