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Biology > Response To Stimuli (chapter 14) > Flashcards

Response To Stimuli (chapter 14) Flashcards

1
Q

What is a stimulus?

A

Detectable change in the internal or external environment of an organism that leads to a response in the organism.

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2
Q

List the order of response (5)

A

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

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3
Q

What is a taxis?

A

Direction determined by the direction of the stimulus moving either towards or away from a stimulus.

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4
Q

What is a positive taxis?

A

Towards the stimulus

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5
Q

What is a negative taxis?

A

Away from a stimulus

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6
Q

Give one example of positive taxis

A

Single celled algae move toward the light for photosynthesis (positive phototaxis)

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7
Q

Give one example of negative taxes

A

Earthworms move away from light (negative phototaxis)

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8
Q

What is kinesis?

A

Organism changes speed at which it moves and the rate at which it changes direction. Ie non directional response.

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9
Q

Give one example of kinesis

A

Woodlice looses H2O in dry. So move faster and change direction more when dry to hopefully end back up in wet.

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10
Q

What is a tropism?

A

Growth response towards or away from a stimulus

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11
Q

Explain light on plants

A

Shoots grow towards light (+ phototropic) for photosynthesis.

Roots (- phototropic)

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12
Q

Explain water on plants

A

Roots grow towards water (+ hydrotropism)

Stem (- hydro tropic)

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13
Q

Explain gravity on plants

A

Roots (+ gravitropism) to get anchored

Stem (- gravitropism)

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14
Q

What is auxins also known as?

A

IAA

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15
Q

What is IAA?

A

It is not a hormone

It is a plant growth factor (effect on near cells)

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16
Q

Explain a phototropic response on shoots

A

IAA accumulates on the shaded side of the plant.

This stimulates cell elongation on shaded side.

Results in bending of shoot towards the light as cells on the light side are not as elongated.

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17
Q

Explain the phototropic response on roots

A

High IAA concentration inhibits cell elongation causing a negative phototropic response.

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18
Q

Explain the gravitropism response on shoots

A

High IAA concentration stimulates cell elongation causing a negative gravitropic response. (Grow upwards)

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19
Q

Explain the gravitropism response on the roots

A

High IAA concentration inhibits cell elongation causing a positive gravitropism response. (Grow downwards)

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20
Q

Explain plasticity on plant cell walls.

ACID GROWTH HYPOTHESES

A

IAA increases the plasticity (ability to stretch) on cell walls. Only on young cell walls, where cells are able to elongate. As cells mature develop greater rigidity. (Older parts wont respond)

(acid growth hypothesis)

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21
Q

Summarise the acid growth hypothesis

A

Hydrogen ions actively transported into the cell wall. Allowing the cell to become more plastic allowing elongation by expansion.

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22
Q

What is the central nervous system made up of?

(CNS)

A

Brain and spinal cord

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23
Q

What is the peripheral nervous system made up of?

(PNS)

A

Pairs of nerves that originate from the brain or spinal cord

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24
Q

What is the peripheral nervous system divided into?

A

Sensory neurones (receptors —> CNS)

Motor neurones (CNS —> effectors)

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25
Q

What is the motor nervous system broken down into?

A

Voluntary nervous system (conscious control)

Automatic nervous system (subconscious)

26
Q

List the order of a reflex arch (7)

A

Stimulus
Receptor
Sensory neurone (enters on dorsal (upper) side)
Coordinator
Motor neurone
Effector
Response

Synapse between

27
Q

What are reflexes (3 things)

A

Fast automatic universal

28
Q

What do Pacinian corpuscles do?

A

Respond to changes in mechanical pressure

Produce a generator potential by acting as a transducer.

29
Q

Where are Pacinian corpuscles found?

A

Deep in the skin

Fingers, soles of feet, external genitalia, joints, ligaments and tendons

30
Q

What is the structure of a Pacinian corpuscle?

Outwards in

A

Capsule
Blood capillary
Layers of connective tissue with viscous gel
Neurone ending (and neurone)

Stretch mediated sodium ion channels

31
Q

Describe how stimulation of a Pacinian corpuscle produces a generator potential (4)

A

Pressure distorts corpuscle opening channels

Na+ ions flood in creating generator potential

Increased pressure opens channels more increasing size of generator potential

If GP above threshold level action potential/ impulse to the brain

32
Q

What shape are rod and cone cells?

A

Rods- rod shaped lol

Cones- cone shaped lol

33
Q

Are there a greater number of cone cells or rod cells in the eyes?

A

More rod cells than cone cells

34
Q

Where are rod cells found?

A

Periphery of the retina

Absent at fovea

35
Q

Where are cone cells found?

A

Few at the periphery of retina

Concentrated at fovea

36
Q

Which (rod or cone) give good visual acuity? (Sharp image)

A

Cone cells

37
Q

Which (rod or cone) are sensitive to low intensity light?

38
Q

How many types of rod cells?

39
Q

How many types of cone cell?

A

Three

Each for different wavelength of light

40
Q

Why can rod cells only see in black and white?

A

Cannot distinguish between wavelengths of light.

41
Q

How is a generator potential created in rod cells?

A

Pigment in rod cells (rhodopsin) must be broken down.

there is enough energy from low light energy to cause this breakdown

This is why rod cells respond to low intensity light

42
Q

What is the consequence of many rod cells linking to a singular bipolar cell.

A

Light received by the rod cells sharing the same neurone will only generate a single impulse travelling to the brain regardless of how many neurones are stimulated.

Therefore low visual acuity

43
Q

How do cone cells allow us to see in colours?

A

Different cone cells respond to different wavelength of light.

44
Q

Why do cone cells only respond to high intensity light?

A

A stimulation of a number of cone cells cannot be combined to exceed threshold value to create a generator potential.

As separate bipolar cell

45
Q

What is the pigment in a cone cell?

46
Q

What are the two divisions of the autonomic nervous system?

A

The sympathetic nervous system

The parasympathetic nervous system

47
Q

Briefly explain the sympathetic nervous system

A

Stimulates effectors and speeds up activity.

Helps us cope with stressful situations by heightening awareness and preparing for activity (fight to flight)

48
Q

Briefly explain the parasympathetic nervous system

A

Inhibits effectors and slows down any activity.

Controls activities under resting conditions. Conserves energy and replenishing body’s reserves.

49
Q

What is a word that describes how parasympathetic and sympathetic work together?

A

They are antagonistic, oppose one another

50
Q

As the heart can innate its own contraction what is it referred as?

51
Q

What is found in the wall of the right atrium in the heart?

A

A group of cells known as sinoatrial node (SAN)

52
Q

Why is the SAN referred to as the pacemaker?

A

It has a basic rhythms of stimulation that determines beat of the heart.

53
Q

What are the events that control the basic heart rate? (3/ breif)

A

A wave of electrical activity spreads our from sinoatrial node (SAN)

Wave spreads across both atria causing them to contract and reach atrioventricular node (AVN)

AVN conveys wave of electrical activity between the ventricles along bundle of His and releases it at the apex, causing ventricles to contract.

54
Q

What is the typical resting heart rate of an adult human?

55
Q

Where are changes in heart rate controlled?

A

Medulla oblongata (in brain)

56
Q

What are the two centres of the medulla oblongata that are concerned with heart rate?

A

Increasing heart rate = sinoatrial node by sympathetic NS

Decreasing heart rate = sinoatrial node by parasympathetic NS

57
Q

Where are chemoreceptors found?

A

in the wall of the carotid arteries

58
Q

What are chemoreceptors sensitive to?

A

Changes in pH of blood resulting form changes in CO2 concentration

(CO2 lowers blood concentration)

59
Q

Explain the effects exercise on cardiac output

A

Increases metabolic activity

More CO2 produced from respiration

Blood pH lowered

Chemical receptors in carotid arteries increase frequency of impulses to the medulla oblongata

Centre in the medulla oblongata that speeds heart rate increases frequency of impulses to SA node via sympathetic NS

SN node increases heart rate

Increased blood flow removes CO2 faster

CO2 conc back to normal

60
Q

How do pressure receptors in walls of carotid arteries and aorta reduce the blood pressure?

(Too high)

A

Pressure receptors transmit more nervous impulses to center in medulla oblongata which decreases heart rate. Sends impulses via parasympathetic to SN leading to a decrease in rate at which heart beats

61
Q

How do pressure receptors increase blood pressure?

(Too low)

A

Pressure receptors transmit more nervous impulses to the centre in the medulla oblongata that increases heart rate. Send impulse via sympathetic to SN which increases rate at which heart beats at

Biology (13 decks)

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