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a level biology > 3.6 organisms respond to changes in their internal and external stimuli > Flashcards

3.6 organisms respond to changes in their internal and external stimuli Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

what is the effector in a nervous response?

A

muscle

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2
Q

what is the effector in a hormonal response?

A

gland

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3
Q

how does the body coordinate a response (simple)?

A

stimulus, receptor, central nervous system, effector, response

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4
Q

what is meant by stimulus?

A

detectable change in the internal or external environment

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5
Q

what are receptors?

A

any structure able to respond to change

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6
Q

what is the co-ordinator?

A

the switchboards connecting information from the receptor to the appropriate effector

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7
Q

what is the response?

A

the output/change in behaviour, the whole organism or only part of it could move in response, the movement could be directional (positive or negative) or non directional, all enable the organism to be better adapted to its environment

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8
Q

what is kinesis/kinetic response?

A

whole organisms, alteration in the rate of movement, in response to a change in the intensity of a stimulus, non directional

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9
Q

what is a tactic response/taxis?

A

movement of the entire organism or cell, in response to and directed by the stimulus, can be positive taxis (towards) or negative taxis (away)

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10
Q

what is a tropic response/tropism?

A

movement of part of a plant, directed by the stimulus, this is a growth response

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11
Q

what is a phototropism?

A

response to light

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12
Q

what is a hydrotropism?

A

response to water

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13
Q

what is a geotropism?

A

response to gravity

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14
Q

what are plant growth factors (auxins)?

A

effect growth, are made by cells located throughout the plant (not organs), produced in small quantities, effect tissues close by and sometimes tissues they are released from

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15
Q

what is the main plant growth factor?

A

the hormone Indoleacetic Acid (IAA) growth factor causing cell elongation

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16
Q

what was Darwin’s observation on plant growth?

A

grasses grown always tilted towards the window

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17
Q

what was Darwin’s hypothesis?

A

light (stimuli) is detected by the tip of the shoot and leads to tilting response

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18
Q

how did Darwin test his theory?

A

used a control group, grass with the tip removed, grass with tip covered by opaque cap, tip covered by transparent cap, base covered with opaque shield

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19
Q

what did Darwin’s control group show?

A

grew towards the light as expected (positively phototrophic)

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20
Q

what did Darwin’s group with the tip removed show?

A

did not grow towards the light

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21
Q

what happened when the tip was covered by an opaque cap? (Darwin)

A

did not grow towards the light

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22
Q

what happened when the tip was covered by a transparent cap? (Darwin)

A

plant grew towards the light

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23
Q

what happened when the base was covered by an opaque shield (Darwin)

A

grew towards light as it doesn’t cover tip

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24
Q

what conclusion did Darwin make from his experiment?

A

the light is detected by the tip and causes the plant to grow in that direction, if you stop light from getting to the tip it does not bend

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25
Q

what did Boysen-Jenson set to find out?

A

if the reason for the plant bending towards the light was a chemical signal or an electrical signal

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26
Q

what is mica?

A

an electrical conductor that does not allow chemicals to diffuse through it

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27
Q

what is gelatin?

A

conducts chemicals but not electricity

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28
Q

(Boysen-Jensen) what happened when a thin impermeable barrier of mica was inserted in the non-shaded side of the plant?

A

movement of chemical down the shaded side, bends towards the light

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29
Q

(Boysen-Jensen) what happened when mica was inserted in the shaded side of the plant?

A

movement of chemical down the shaded side is prevented by mica, no response

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30
Q

(Boysen-Jensen) what happened when the tip of the plant was removed a gelatin block inserted and tip replaced?

A

movement of chemical down the shaded side, bends towards light

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31
Q

what conclusions can be made from Boysen-Jensons experiment?

A

bending is a chemical factor, chemicals (IAA) is produced in the shoot tip and causes elongation on the shaded side

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32
Q

what are the two main divisions of the nervous system?

A

central nervous system (CNS) and peripheral nervous system (PNS)

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33
Q

what is the central nervous system?

A

the brain and spinal cord

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34
Q

what is the peripheral nervous system?

A

pairs of nerves from the CNS travelling to limbs and organs (sensory neurone and motor neurone), relays messages from the CNS to the effector

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35
Q

what are the two main divisions of the PNS?

A

somatic (conscious) and autonomic (subconscious)

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36
Q

what are reflexes?

A

involuntary responses to a stimuli

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37
Q

what are the five main reasons why reflexes are important?

A

immediate, innate, automatic, protective response, do not involve the conscious part of the brain

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38
Q

explain why reflexes are important (3 marks)

A

reduces damage to tissue, which would decrease the chance of survival as it could prevent the organism from obtaining food or escape from predators

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39
Q

what are receptors?

A

any structure able to respond to change, receive information and pass it to CNS, are specific in what they detect, two main components for receiving information

40
Q

what are transducers?

A

sensory information must be converted into information that the body understands, sensory information it’s converted to nerve impulses (action potential) e.g. pacinian corpuscle (skin) and rod and come cells (eye)

41
Q

what is the pacinian corpuscle?

A

found in the skin (fingers, soles of feet) responds to the stimuli or pressure, gathers this information and transducers it

42
Q

what is the structure of the pacinian corpuscle?

A

consists of a sensory neurone ending surrounded by layers of connective tissue and viscous gel (blood capillary, capsule, sensory neurone, viscous gel, neurone ending, layers of connective tissue)

43
Q

what is resting potential?

A

nerve membrane at rest

44
Q

what is action potential?

A

message travelling through the nerve

45
Q

describe the sequence of events by which pressure on a pacinian corpuscle results in the creation of a generator potential (6 marks)

A

when pressure is applied to the pacinian corpuscle in the skin, pressure is applied to the lamellar which become deformed and put pressure on the membrane of the sensory neurone. This causes the neurone to become stretches which widens the stretch mediated sodium channels, causing the channels to open, allowing sodium ions to move into the neurone via facilitated diffusion. The influx of sodium ions depolarises the membrane (from negative to positive) and creates a generator potential. If the generator potential reaches the threshold it trigger an action potential

46
Q

why might the pathway shown in a diagram be considered a simple reflex arc?

A

it is the result of three neurones transferring the message

47
Q

suggest two advantages of simple reflexes

A

the brain can focus on complex behaviours, rapid, protection, innate

48
Q

why is a kinetic response advantageous to a louse?

A

stays in favourable conditions for longer, associates with a food source

49
Q

explain in terms of pressure why the semilunar valve opens

A

higher pressure below the valve forces it to open

50
Q

explain the importance of the short delay before the new wave leaves the AVN?

A

allows all of the blood to leave the atrium to the ventricle before it is pumped out of the heart

51
Q

how do you calculate stroke volume?

A

cardiac output / heart rate

52
Q

describe how the heart controls and coordinates the regular contraction of the atria and ventricles?

A

the SAN sends an electrical impulse across the atria causing the atria to contract increasing the pressure which forces the atrioventricular valve to open. This impulse is detected by the AVN which sends a signal down the bundle of His into the Purkinjie fibres to reach the apex as the septum is made of non conductive tissue. This causes the ventricle to contract from the apex, after a delay to ensure all blood has entered the ventricle, forcing the semi lunar valve to open so blood is forced out of the heart to the lungs and body/respiring tissues

53
Q

explain how increased intensity of activity leads to an increased heart rate?

A

Increase CO2 concentration detected by chemoreceptors, sends message to medulla oblongata, increased impulse to SAN via sympathetic nervous system

54
Q

what are receptors?

A

they detect stimuli, they can be cells or proteins on cell surface membranes, different types of receptors detect different stimuli

55
Q

what are effectors?

A

cells that bring about a response to the stimulus, to produce an effect include muscle cells and cells found in glands such as the pancreas

56
Q

what are receptors?

A

communicate with effectors via the nervous system or the hormonal system or both

57
Q

what are the three main neurones?

A

sensory neurones, motor neurones and relay neurones

58
Q

what are sensory neurones?

A

transmit electrical impulses from receptors to the central nervous system (CNS) - the brain and spinal cord

59
Q

what are motor neurones?

A

transmit electrical impulses from the CNS to effectors

60
Q

what are relay neurones? (intermediate neurones)

A

transmit electrical impulses between sensory neurones and motor neurones

61
Q

what is the order of the nervous system?

A

stimulus, receptors, CNS, effectors, response

62
Q

what is the sympathetic nervous system?

A

gets the body ready for action, fight or flight system

63
Q

what is the parasympathetic nervous system?

A

calms the body down, rest and digest systems

64
Q

what are reflexes?

A

where the body responds to a stimulus without making a conscious decision for rapid protection

65
Q

what does a simple reflex arc involve?

A

receptor, sensory neurone, relay neurone (in spinal cord), motor neurone, effector

66
Q

what can happen if a relay (intermediate) neurone is involved in a simple reflex arc?

A

your brain could override the reflex

67
Q

what is generator potential?

A

more ions move in and out of the cell as the membrane is excited by a stimulus and becomes permeable, changing the potential difference

68
Q

how is an action potential triggered?

A

the generator potential reaches the threshold level

69
Q

how does light enter the eye?

A

through the pupil

70
Q

how is the amount of light entering the eye controlled?

A

by the muscles in the iris

71
Q

where is light focused in the eye?

A

by the lens onto the retina that contains photoreceptor cells

72
Q

what is the fovea?

A

an area of the retina where there are lots of photoreceptors

73
Q

how are nerve impulses from the eye sent to the brain?

A

nerve impulses from the photoreceptor cells are carried from the retina to the brain by the optic nerve which is a bundle of neurones

74
Q

what is the blind spot?

A

where the optic nerve leaves the eye there are no photoreceptors so it is not sensitive to light

75
Q

how to photoreceptors send impulses to the brain?

A

light enters the eye, 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 it reaches the threshold a nerve impulse is sent along a bipolar neurone, bipolar neurones connect photoreceptors to the optic nerve, which takes impulses to the brain

76
Q

what are the two types of photoreceptor cells?

A

rod cells and cone cells

77
Q

what is the quantity of rod cells?

A

most numerous

78
Q

what is the pigment present in rod cells?

A

rhodopsin

79
Q

what type of image do rod cells produce?

A

black and white

80
Q

where are rod cells most numerous?

A

everywhere but the fovea

81
Q

what light intensities are required to break down rhodopsin?

A

low light intensity

82
Q

what is the visual acuity of rod cells?

A

low visual acuity

83
Q

what are neural connections like in rod cells?

A

multiple cells attached to one sensory neurone - retinal convergence, threshold value must be exceeded, additive effect of each means a lower light intensity is needed to create generator potential

84
Q

what is the quantity of cone cells

A

lower frequencies

85
Q

what is the pigment present in cone cells?

A

iodopsin

86
Q

what type of image do cone cells produce?

A

coloured

87
Q

where are cone cells most numerous?

A

back of the fovea

88
Q

what is the light intensity required to break down iodopsin?

A

high light intensity

89
Q

what are the neural connections like in cone cells?

A

one connection per cell to distinguish colour from the three different types of iodopsin

90
Q

what is the SAN?

A

the sinoatrial node, found in the right atrium, the natural pacemaker

91
Q

what is the AVN?

A

the atrioventricular node

92
Q

heart rate changes, explain why?

A

varying oxygen demands e.g. exercise, heart rate speeds up the flow of blood, more glucose and oxygen, more respiration, more energy

93
Q

what is the medulla oblongata?

A

a cone shaped neuronal mass, responsible for involuntary functions, contains the cardiac, respiratory and vomiting centres, controls breathing, heart rate and blood pressure

94
Q

what are the two types of receptors for the medulla?

A

chemoreceptors in the carotid artery for chemical changes in the blood and baroreceptors in the carotid artery and aorta for changes in blood pressure

95
Q

what happens when blood pressure is high?

A

baroreceptors send nervous impulse to the centre in the medulla, the centre sends an impulse via the parasympathetic NS to the SAN, decreases the rate at which the heart beats

96
Q

what happens when blood pressure is low?

A

baroreceptors send nervous impulse to the centre in the medulla, the centre sends an impulse via the sympathetic NS to the SAN, increases the rate at which the heart beats

97
Q

Explain the role of the medulla oblongata in controlling blood pH (six marks)

A

A higher respiratory rate increases the concentration of carbon dioxide is in the blood which lowers the pH, this decreased PH is detected by chemo receptors in the carotid artery, nervous impulses is sent to the cardiac centre in the medulla, the centre sends an impulse via the sympathetic nervous system to the SAN which increases the electrical impulse across the atria, this increases the heart rate to increase the blood oxygen concentration to increase the pH

a level biology (21 decks)

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