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AQA A level Biology > Organisms respond to changes in their internal and external environments > Flashcards

Organisms respond to changes in their internal and external environments Flashcards

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1
Q

Nervous communication

A

The response to a stimulus is coordinated by the nervous system

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2
Q

Sequence of events for nervous communication

A

stimulus–+ receptor –+ coordinator –+ effector –+ response

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3
Q

What is simple reflex?

A

Rapid and involuntary response to a stimulus (not involving the brain) providing a protective effect

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4
Q

Tactic response (taxis)

A

A simple directional response whose direction is determined by the direction of the stimulus (deliberate)

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5
Q

Positive taxis

A

Movement towards the stimulus

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6
Q

Negative taxis

A

Movement away from the stimulus

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7
Q

Kinetic response (kinesis)

A

A non directional response in which the organism does not move towards or away from a stimulus (random). Instead, it changes the speed at which it moves and the rate at which it changes direction.

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8
Q

Tropism

A

Response to a part of a plant towards a directional stimulus

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9
Q

Positive tropism

A

Growth towards stimulus

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10
Q

Negative tropism

A

Growth away from stimulus

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11
Q

Plant growth factors

A
  • Produced by cells in plants
  • May also affect growth of tissues that release them not just distant target organ
  • Exert influence by affecting growth
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12
Q

Indoleacetic acid (IAA)

A

Belongs to a group of substances, auxins
-Controls cell elongation in plants
-Produced in the tips of shoots and roots

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13
Q

Responses for plants

A

Light, Gravity, Water

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14
Q

Phototropism (shoots)

A

Initially IAA is evenly distributed throughout regions
- Light intensity changes and auxins move from light side to shaded side of plant
- Causing shaded shoot to elongate
- Shaded shoots bend and grow at a faster rate than lighter side in direction of light
(positive phototropism)

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15
Q

Phototropism (roots)

A

Initially IAA is evenly distributed throughout regions
- Light intensity changes and auxins move from light side to shaded side of plant
- Causing shaded roots to inhibit cell elongation
- Shaded roots bend and grow at a slower rate than lighter side in direction of light
(negative phototropism)

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16
Q

Geotropism (shoots)

A

Initially IAA is evenly distributed throughout regions
- Moves to underside of plant causing elongation
- Lower side grows at a faster rate than upper side
- Moves upwards away from gravity
(negative geotropism)

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17
Q

Geotropism (roots)

A

Initially IAA is evenly distributed throughout regions
- Moves to underside of plant inhibiting elongation
- Lower side grows at a slower rate than upper side
- Moves downwards towards gravity
(positive geotropism)

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18
Q

Hydrotropism (roots)

A

Positive hydrotropism to direction of water

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19
Q

Hydrotropism (shoots)

A

Negative hydrotropism away from water

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20
Q

Thigmotropism

A

Plants able to climb and attach to other things when growing
Positive- move to stimulus
Negative- move away from stimulus

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21
Q

What happens when you remove tips of shoots and roots?

A

It also removes IAA preventing ability to bend in a direction and grow

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22
Q

What are the principles of coordination?

A

Two main forms of coordination in animals - the nervous system and the hormonal system

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23
Q

The nervous system

A

Use of nerve cells to pass electrical impulses along their length. They stimulate their target cells by secreting chemicals, known as neurotransmitters, directly on to them. This results in rapid communication between specific parts of an organism. The responses produced are often short-lived and restricted to a localised region of the body

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24
Q

The hormonal system

A

Produces chemicals (hormones) that are transported in the blood plasma to their target cells. The target cells have specific receptors on their cell-surface membranes and the change in the concentration of hormones stimulates them. This results in a slower, less specific form of communication between parts of an organism. The responses are often long-lasting and widespread.

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25
Q

Neurones

A

Specialised nerve cells that are responsible for conducting electrical impulses (action potential) around the body

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26
Q

Sensory neurones

A

Transmits nerve impulses from a receptor to an relay (intermediate) neurone or directly to a motor neurone.

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27
Q

Relay (intermediate) neurones

A

Transmit impulses between sensory and motor neurones

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28
Q

Motor neurones

A

Transmits nerve impulses from a relay (intermediate) neurone to an effector, such as a gland/muscle

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29
Q

Structure of neurones
- Dendrons

A

Extensions of the cell body which subdivide into smaller branched fibres, called dendrites, that can conduct electrical impulses from multiple neurones at the same and carry to cell body

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30
Q

Structure of neurones
- Axons

A

A single long fibre that carries nerve impulses away from the cell body

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31
Q

Myelinated neurones

A

Contain a myelin sheath which forms a covering to the axon and is made up of the membranes of the Schwann cells. These membranes are rich in lipids known as myelin

32
Q

Schwann cells

A

Surround the axon, protecting it and providing electrical insulation. They also carry out phagocytosis (the removal of cell debris) and play a part in nerve regeneration. They wrap themselves around the axon many times, so that layers of their membranes build up around making up myelin sheath

33
Q

Nodes of Ranvier

A

Constrictions between adjacent Schwann cells where there is no myelin sheath.
The constrictions are 2- 3 μm long and occur every 1- 3 mm in humans

34
Q

Cell body

A

Contains all the usual cell organelles, including a nucleus and large amounts of rough endoplasmic reticulum.
Associated with the production of proteins and neurotransmitters

35
Q

Reflex

A

A response to a stimulus that is rapid, short-lived, localised and
totally involuntary.

36
Q

Reflex arc

A

The stimulus
A receptor
A coordinator
A motor neurone
An effector
The response

37
Q

Central nervous system

A

CNS
- Made up of the brain and spinal cord

38
Q

Peripheral nervous system

A

PNS
- Made up of pairs of nerves that originate from either the brain or the spinal cord.

39
Q

Structure of Pacinian corpuscle

A
  • Occur deep in the skin, most abundant in fingers, soles of feet and external genitalia
  • Sensory ending at the end of receptor has a stretch- mediated sodium channel
40
Q

Function of Pacinian corpuscle

A

At resting potential, sodium channels are too narrow for sodium ions to pass. When pressure is applied it becomes deformed and membrane around neurone stretches so sodium ions diffuse into it. Influx of sodium ions depolarises membrane producing generator potential.

41
Q

Receptors of the eye

A

Sensitive to light and colour

42
Q

What is the nervous system split into?

A
  • Central nervous system
  • Peripheral nervous system
43
Q

What is the peripheral nervous system split into?

A
  • Somatic nervous system
  • Autonomic nervous system
44
Q

Somatic nervous system

A

Controls our conscious activity (walking, talking etc)

45
Q

Autonomic nervous system

A

Controls our unconscious activity (breathing, digestion etc).

46
Q

What is the autonomic nervous system split into?

A
  • Sympathetic nervous system
  • Parasympathetic nervous system
47
Q

Sympathetic nervous system

A

Provides the “fight or flight” response and prepares us for action.
- stimulates effectors and so speeds up any activity

48
Q

Parasympathetic nervous system

A

Provides the “rest and digest” response and calms the body down.
- inhibits effectors and so slows down any activity, controlling activities under normal resting conditions. It is concerned with conserving energy and replenishing the body’s reserves.

49
Q

Spatial summation

A

A number of different presynaptic neurones together release enough of the neurotransmitter to exceed the threshold value of the postsynaptic neurone. Together they trigger a new action potential.

50
Q

Temporal summation

A

A single presynaptic neurone releases the neurotransmitter many times over a very short period. If the concentration of the neurotransmitter exceeds the threshold value of the postsynaptic neurone, then a new action potential is triggered.

51
Q

Neuromuscular junction

A

Type of cholinergic junction between motor neurone and muscles that uses ACh

52
Q

Neuromuscular junction characteristics

A
  • Postsynaptic membrane folded to form clefts which store AChE
  • Has more ACh receptors
  • ACh is always excitatory
53
Q

Example of an inhibitory neurotransmitter

A

GABA

54
Q

Example of an excitatory neurotransmitter

A

ACh

55
Q

ACh

A

Acetylcholine
- an excitatory neurotransmitter, a chemical that carries messages from your brain to your body through nerve cells

56
Q

AChE

A

Acetylcholinesterase
- an enzyme

57
Q

What is a synapse?

A

The junction between two or more neurones/ neurones and effectors

58
Q

Synaptic cleft

A

Gap between neurones

59
Q

Refractory period purposes

A
  • limits the number of action potentials
  • It produces discrete impulses
  • It ensures that action potentials are propagated in one direction only
60
Q

What is homeostasis?

A

The maintenance of the stable internal environment within restricted limits, regardless of changes to the external environment.

61
Q

Negative feedback

A

The change produced by the control system which leads to a change in the stimulus detected by the receptor and turns the system off

62
Q

Positive feedback

A

Occurs when a deviation from an optimum causes changes that result in an even greater deviation from the normal

63
Q

What are hormones?

A

Chemical messengers, that are produced in organs called glands. They are released directly in the bloodstream where they are carried around body to target cells.

64
Q

Characteristics of hormones

A

They are effective in low concentrations, but often have long lasting and wide spread effects.

65
Q

Hormones controlling blood glucose concentration

A
  • Glucagon
    Produced by cells in pancreas known as islets of Langerhans.
66
Q

What cells do islets of Langerhans consist of ?

A

α- cells
β- cells

67
Q

What do α- cells secrete?

A

Alpha (α) cells, which are larger, manufacture
and secrete the hormone glucagon.

68
Q

What do β- cells secrete?

A

Beta (β) cells, which are smaller, manufacture and secrete the hormone insulin.

69
Q

Role of liver in regulating blood sugar

A
  • Glycogenesis
  • Glycogenolysis
  • Gluconeogenesis
70
Q

Glycogenesis

A

The conversion of glucose into glycogen.
- When blood glucose concentration is higher than normal the liver removes glucose from the blood and converts it to glycogen.

71
Q

Glycogenolysis

A

The breakdown of glycogen to glucose.
- When blood glucose concentration is lower than normal, the liver can convert stored glycogen back into glucose which diffuses into the blood to restore the normal blood glucose concentration.

72
Q

Gluconeogenesis

A

The production of glucose from sources other than carbohydrate.
- When its supply of glycogen is exhausted, the liver can product glucose from non-carbohydrate sources such as glycerol and amino acids.

73
Q

Normal blood glucose concentration

A

approximately 5 mmol/dm³

74
Q

What is adrenaline?

A

A hormone produced in the adrenal glands.

75
Q

Function of adrenaline in blood glucose concentration

A

In times of excitement or stress, it increases the blood glucose concentration by binding to specific protein receptors on the cell surface membrane of the target cells, activating enzymes that cause the breakdown of glycogen into glucose in the liver cells.

76
Q
A

AQA A level Biology (7 decks)

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