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A-Level Biology > Topic 6 - Responding to Changes in the Environment > Flashcards

Topic 6 - Responding to Changes in the Environment Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

What is plant growth controlled by?

A

IAA (indoleactic acid).

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2
Q

What is IAA?

A

It is an auxin produced in the tips and shoots of flowering plants.

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3
Q

What is a tropism?

A

Tropism is a directional growth in plants in response to a stimulus.

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4
Q

What are the three types of tropism?

A

Phototropism, Gravitropism and Thigmotropism.

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5
Q

What is being described when the plant shoots are labelled as positively phototropic?

A

Shoots are growing towards the light.

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6
Q

What is being described when the plant shoots are labelled as negatively phototropic?

A

The roots are growing away from the light.

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7
Q

What does the distribution of IAA control?

A

It controls the tropisms in the plant.

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8
Q

What happens when the auxins are evenly distributed?

A

They move down the shoot tip causing elongation of cells across the zone of elongation.

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9
Q

How does IAA affect gravitropism?

A

It builds up on the lower side of the roots and inhibits growth, causing the root to bend downwards.

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10
Q

What are the 3 main types of neurons?

A

Sensory neurons, relay neurons and motor neurons.

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11
Q

What are the role of sensory neurons?

A

They transmit electrical impulses from the receptor to the central nervous system.

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12
Q

What are the role of relay neurons?

A

They transmit electrical impulses between the sensory and motor neurons.

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13
Q

What are the role of motor neurons?

A

They transmit electrical impulses from the central nervous to effectors.

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14
Q

What is a simple reflex arc?

A

A simple reflex is a rapid, involuntary response to a stimulus.

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15
Q

What is a reflex arc?

A

The pathway of neurons linking receptors in a simple reflex arc.

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16
Q

How are simple reflexes protective?

A

They help organisms to avoid damage to the body because the response happens quickly.

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17
Q

What are receptors?

A

Receptors are cells or proteins that can detect a specific stimulus.

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18
Q

What are the two different receptors and what do they detect?

A

Photoreceptors - Detect change in light.
Mechanoreceptors - Detect mechanical stimuli in the form of pressure and vibrations.

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19
Q

What is an example of a mechanoreceptor?

A

Pacinian Corpuscle.

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20
Q

What does the Pacinian Corpuscle include?

A

A single sensory neuron and the end neuron is wrapped in layers of connective tissues (lamellae).

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21
Q

Where is the Pacinian Corpuscle found?

A

Found deep in the skin and joints.

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22
Q

What does the Pacinian Corpuscle contain?

A

It contains stretch mediated sodium channels in the cell surface membrane.

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23
Q

How does pressure affect the stretch mediated sodium channels?

A
  • When they aren’t under pressure, the channels are closed.
  • Under pressure, the channels become deformed.
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24
Q

What happens when the channels are deformed?

A

They open and allow an influx of sodium ions.

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25
Q

What does an influx of sodium ions result in?

A

As the sodium ions are positively charged, the membrane potential is altered - therefore the membrane is polarised. This results in a generator potential being created which goes on to to create an action potential in the axon.

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26
Q

What happens at the parasympathetic neurone?

A

The SAN decreases the frequency with which it produces waves of electrical activity.

27
Q

What neurotransmitter is present at the parasympathetic neurone?

A

Acetylcholine.

28
Q

What happens at the sympathetic neurone?

A

SAN increases frequency with which it produces waves of electrical activity.

29
Q

What neurotransmitter is present at the sympathetic neurone?

A

Noradrenaline.

30
Q

What are the two receptors found in relation to the heart?

A

Pressure receptors called baroreceptors.
Chemical receptors called chemoreceptors.

31
Q

Where are baroreceptors found and how are they stimulated?

A

They’re found in the aorta and cartoid arteries. They are stimulated by high and low blood pressure.

32
Q

Where are chemorecepotrs found and what is their role in the body?

A

They’re found in the aorta, cartoid arteries and in the medulla. They monitor gas concentration and pH.

33
Q

How do baroreceptors regulate high blood pressure?

A
  • Baroreceptors detect high blood pressure.
  • Impulses are sent along the sensory neurones to the medulla.
  • Impulses are sent along the parasympathetic neurones.
  • Acetylcholine is secreted which binds to the receptors on the SAN.
  • This causes the heart rate to slow down and reduce blood pressure.
34
Q

How do baroreceptors regulate low blood pressure?

A
  • Baroreceptors detect low blood pressure.
  • Impulses are sent along the sensory neurones to the medulla.
  • Impulses are sent along the sympathetic neurones.
  • Noradrenaline is secreted which binds to the receptors on the SAN.
  • This causes the heart rate to quicken and increase blood pressure.
35
Q

How do chemoreceptors regulate high blood oxygen conc., high carbon dioxide conc., high blood pH levels?

A
  • Chemoreceptors detect chemical changes in the blood
  • Impulses are sent along the sensory neurones to the medulla.
  • Impulses are sent along the parasympathetic neurones.
  • Acetylcholine is secreted which binds to the receptors on the SAN.
  • This causes the heart rate to slow down.
36
Q

How do chemoreceptors regulate low blood oxygen conc., high carbon dioxide conc., high blood pH levels?

A
  • Chemreceptors detect chemical changes in the blood.
  • Impulses are sent along the sensory neurones to the medulla.
  • Impulses are sent along the sympathetic neurones.
  • Noradrenaline is secreted which binds to the receptors on the SAN.
  • This causes the heart rate to quicken.
37
Q

What is the structure of myelinated motor neurone?

A
  • Myelin is made up of lipid rich membranes from specialised cells which wrap themselves around the axon and act as an electrical insulator.
  • Between the Schwann cells are patches of the bare neurones membrane called the nodes of Ranvier. The Na+ channels are cocnentrated there.
38
Q

Where does depolarisation occur in a myelinated neurone?

A

At the nodes of Ranvier.

39
Q

How does impulses travel along a myelinated neurone?

A

Through saltatory conduction.

40
Q

What is saltatory conduction?

A

Na+ ions diffuse through the cytoplasm and depolarise the membrane at the next node as the impulse jumps from node to node.

41
Q

How quick is the process of saltatory conduction?

A

It is very fast.

42
Q

How does impulses travel in a non-myelinated neurone and how fast is this process?

A

The impulse has to travel as a wave along the whole length of the axon, this is slower than saltatory conduction.

43
Q

What other factors affect the speed of conduction?

A

Axon diameter and temperature.

44
Q

How does axon diameter affect the speed of conduction?

A

Axons with larger diameter action potentials travel faster as there is less resistance to the flow of ions in the cytoplasm than in narrower axons.

45
Q

How does temperature affect the speed of the conduction?

A

At high temperatures ions diffuse faster so speed of conduction is increased up until around 40 degrees celsius when the protein channels start to denature. When they’re denatured this will then decrease the speed of transmission.

46
Q

What is the structure of the synapse?

A
47
Q

What are the 5 steps in synaptic transmission? (1,2,3)

A
  1. An action potential arrives at the end of the parasynaptic neurone.
  2. This depolarises the membrane and stimulates voltage-gated calcium ions channels to open an influx of Ca2+ ions into the synaptic knob.
  3. The influx of Ca2+ ions causes vesicles containing ACh to fuse to the presynaptic membrane releasing ACh into the cleft through exocytosis.
48
Q

What are the 5 steps in synaptic transmission? (4,5)

A
  1. ACh diffuses across the cleft and binds to the specific receptors on the postsynaptic membrane, this causes a slight delay in impulse.
  2. The neurotransmitter binds to the Na+ ion channels open and an influx of sodium ions depolarises the postsynaptic neurone.
49
Q

What happens at inhibitory synapses?

A

Neurotransmitters hyperpolarises the membrane by binding to chloride ions channel on the postsynaptic neurone causing them to open and causes the K+ ions channels to open.

50
Q

Why is it important that the postsynaptic neurone is negative?

A

An impulse is less likely to be created.

51
Q

What is summation?

A

Where the effect of a stimulus can be added together.

52
Q

What is the importance of summation?

A

It allows synapses to accurately process information and fine tune a response.

53
Q

What is spatial summation?

A

Two or more presynaptic neurones release neurotransmitters at the same time onto the same presynaptic neurone.

54
Q

How does spatial summation occur?

A

A combination of small amounts of neurotransmitters can be released from each can be enough to reach the threshold and trigger an action potential in the postsynaptic neurone.

55
Q

What is temporal summation?

A

Two or more nerve impulses in quick succession from the presynaptic neurone.
(The greater the stimulus the greater the frequency of impulses.)

56
Q

How does temporal summation occur?

A

The combination of small amounts of neurotransmitter released from each is enough to reach the threshold and trigger an action potential in the postsynaptic neurone.

57
Q

Where does the neuromuscular junction occur?

A

Between a motor neurone and effector muscle cell.

58
Q

Transmission along a neuromuscular junction? (1)

A
  1. Action potential reaches the synaptic knob.
  2. Calcium channels open and calcium ions rush into the pre-synaptic neurone.
  3. Synaptic vesicles fuse with the pre-synaptic membrane.
59
Q

Transmission across a neuromuscular junction? (2)

A
  1. Acetylcholine is released and diffuses across the synaptic cleft.
  2. Acetylcholine binds with nicotinic cholinergic receptors on the muscle cell membrane.
  3. Na+ channels opens which causes depolarisation, leading to muscle contraction.
60
Q

Can drugs affect the neuromuscular Junction?

A

Certain drugs can affect the neuromuscular junction by altering the levels or activity of acetylcholine.

61
Q

What is a skeletal muscle?

A

A muscle connected to the skeleton, which is used to create movement.

62
Q

What is a skeletal muscle made up of?

A

Long cells called muscle fibres.

63
Q
A

A-Level Biology (7 decks)

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