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Biology Paper 3 > Nervous and hormonal control (8.1–8.7) > Flashcards

Nervous and hormonal control (8.1–8.7) Flashcards

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1
Q

How do animals increase their chances of survival?

A

By responding to changes in their external environment

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2
Q

Why do animals respond to changes in their internal environment?

A

To ensure they are always optimal for their metabolism.

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3
Q

What is a stimulus?

A

A change in the internal or external environment.

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4
Q

What are receptors?

A

They detect stimuli and can be cells or proteins on cell surface membranes.

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5
Q

What are effectors?

A

Cells that bring about a response to a stimulus to produce an effect. Include muscle cells.

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6
Q

How do receptors communicate with effectors?

A

Via the nervous system or the hormonal system

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7
Q

What are the 3 main types of neurone?

A

Sensory, motor, and relay.

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8
Q

Sensory neurones?

A

Transmit electrical impulses form receptors to the CNS

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9
Q

Motor neurones?

A

Transmit electrical impulses from the CNS to effectors.

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10
Q

Relay neurones?

A

Transmit electrical impulses between sensory neurones and motor neurones.

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11
Q

What is the basic process from a stimulus to an effector?

A
  1. Stimulus is detected by receptor cell and an electrical impulse is sent along a sensory neurone.
  2. When an electrical impulse reaches the end of a neurone chemicals called neurotransmitters take information across to the next neurone which sends an electrical impulse.
  3. CNS processes the information and sends an impulse along motor neurones to effectors.
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12
Q

What happens to your eyes in dim light?

A
  1. Photoreceptors in your eye detect the lack of light.
  2. CNS processes the information
  3. Radial muscles in the iris are stimulated.
  4. Radial muscles contract to dilate your pupils.
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13
Q

What happens to your eyes in bright light?

A
  1. Photoreceptors in your eye detect the bright light.
  2. CNS processes the information
  3. Circular muscles in the iris are stimulated by the motor neurones.
  4. Circular muscles contract to constrict your pupils.
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14
Q

What is a gland?

A

A group of cells that are specialised to secrete a useful substance, such as a hormone.

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15
Q

What are hormones?

A

Chemical messengers. Many are proteins or polypeptides. Some are steroids.

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16
Q

When are hormones secreted?

A

When a gland is stimulated by a change in concentration of a specific substance.

They can also be stimulated by electrical impulses.

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17
Q

How do hormones work?

A

Hormones diffuse directly into the blood. They diffuse out of the blood all over the body but only bind to specific receptors found on target cells.

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18
Q

What is the basic process of hormones? in the example of low glucose levels and the release of glucagon

A
  1. Low glucose level concentration
  2. Receptors on pancreas cells detect the low blood glucose concentration
  3. The pancreas releases the hormone glucagon into the blood
  4. Target cells in the liver detect glucagon and convert glycogen into glucose.
  5. Glucose is released into the blood, so glucose concentration increases.
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19
Q

Compare nervous communication with hormonal communication?

A

Nervous vs Hormonal

Electrical impulses vs chemicals

Faster vs slower

Localised vs widespread response

Short lived vs long lived

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20
Q

What is potential difference?

A

When there is voltage across a membrane

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21
Q

What is meant by receptors being specific?

A

They only detect one particular stimulus.

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22
Q

How do photoreceptors convert light into an electrical impulse?

A
  1. Light enters the eye, hits the photo receptor and is absorbed by light sensitive pigments.
  2. Light bleaches the pigments causing a chemical change.
  3. This triggers a nerve impulse along a bipolar neurone.
  4. Bipolar neurones connect photoreceptors to the optic nerve, which takes impulses to the brain.
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23
Q

What are the two types of receptor?

A

Rods and cones

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24
Q

Where are rods mostly found?

A

In the peripheral parts of the retina

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25
Q

Where are cones found?

A

Packed together in the fovea.

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26
Q

What are the 3 types of cones?

A

Red sensitive, green sensitive and blue sensitive.

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27
Q

What do rod cells give information in?

A

Black and white.

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28
Q

What happens in your rod cells when its dark (not activated)?

A
  1. Sodium ions are pumped out of the cell using active transport.
  2. Sodium ions diffuse back in to the cell through open sodium channels.
  3. This makes the inside of the cell only slightly negative compared to the outside. The membrane is depolarised.
  4. This triggers the release of neurotransmitters.
  5. The neurotransmitters inhibit the bipolar neurone so the bipolar neurone cannot fire an action potential so no information goes into the brain.
29
Q

What happens when your rod cells are stimulated (in the light)?

A
  1. Light energy causes rhodopsin to break apart into retinal and opsin. (bleaching)
  2. Bleaching of rhodopsin causes the sodium ion channels to close.
  3. So sodium ions are actively transported out of the cell, but they cant diffuse back in.
  4. Sodium ions build up on the outside of the cell, making the inside of the membrane much more negative than the outside, the cell membrane in hyperpolarised.
  5. When the rod cell is hyperpolarised it stops releasing neurotransmitters. So there is no inhibition of the bipolar neurone.
  6. Because the bipolar neurone is no longer inhibited it depolarises. If the change in the potential difference reaches the threshold, an action potential is transmitted to the brain via the optic nerve.
30
Q

What do all neurones have?

A

A cell body with a nucleus. Plus cytoplasm and all other organelles you usually get in a cell.

31
Q

Draw and describe a motor neurone

A

Many short dendrites and One long axon

32
Q

Describe the function of a motor neurone?

A

Carries nerve impulses from the CNS to effector cells.

33
Q

Draw and describe a sensory neurone?

A

One long dendron carries nerve impulses from receptor cells to the cell body which is in the middle of the neurone.

One shot axon carries nerve impulses from the cell body to the CNS.

34
Q

What is the function of sensory neurones?

A

Carrying impulses from receptor cells to the CNS.

35
Q

Draw and describe a relay neurone?

A

Many short dendrites carry nerve impulses from sensory neurones to the cell body.

An axon carries nerve impulses from the cell body to motor neurones.

36
Q

Describe a neurone cell membrane at rest

A
  1. The outside of the membrane is positively charged compared to the inside.
  2. As there are more positive ions outside the cell than inside.
  3. So the membrane is polarised and the resting potential is -70mV.
37
Q

How is a resting potential created and maintained in a neurone membrane?

A

Sodium and potassium pumps and potassium ion channels.

  • The sodium-potassium pump uses active transport to move 3 Na+ out for for every 2 K+ in. ATP is needed to do this.

This creates a sodium electrochemical gradient because there are more positive sodium ions outside the cell than inside.

  • The potassium ion channel allows the movement of K+ down the concentration gradient out of the cell.

this makes the outside of the cell positively charged compared to the inside.

38
Q

Describe the process of cell membrane becoming depolarised when they’re stimulated.

A
  1. Stimulus- Sodium ion channels open. Sodium ions diffuse into the neurone down the sodium ion electrochemical gradient. This makes the inside of the neurone less negative.
  2. Depolarisation- If the PD reaches -55mV more sodium channels open and more sodium ions diffuse into the neurone.
  3. Repolarisation- At PD of +30mV the sodium ion channels open. The membrane is more permeable to potassium so potassium ions diffuse out of the neurone down the potassium ion concentration gradient.
  4. Hyperpolarisation- Potassium ion channels are slow to close so too many potassium ions diffuse out of the neurone. The PD becomes more negative than the resting potential.
  5. Resting potential- Ion channels are reset. Sodium potassium pump returns the membrane to its resting potential.
39
Q

What is the refractory period?

A

When the ion channels are recovering and cant be made to open so the cell membrane cannot be excited.

40
Q

How does action potential move along the neurone?

A

When action potential happens some of the sodium ions that enter the neurone diffuse sideways.

This causes the sodium ion channel in the next region of the neurone to open and sodium ions diffuse into that part.

That causes a wave of depolarisation to travel along the neurone.

The wave moves away from the parts of the membrane in refractory period because these parts cannot fire an action potential.

41
Q

What are the benefits of the refractory period?

A

Acts as a time delay making sure that action potentials don’t overlap but pass along as discrete impulses.

Ensures action potential is unidirectional

42
Q

What happens to action potential if its a bigger stimulus?

A

Wont cause a bigger action potential but will cause them to fire more frequently.

43
Q

How do local anesthetics work?

A

They bind to sodium ion channels in the membrane.

This stops sodium ions from moving into the neurones so their membranes will not depolarise.

This prevents action potentials from being conducted along the neurones and stops information about pain reaching the brain.

44
Q

What is the structure of a myelinated neurone?

A

Myelin sheath made of Schwann cell. Tiny patches of bare membrane called the nodes of Ranvier.

45
Q

What is saltatory conduction?

A

In myelinated neurone depolarisation only happens at the nodes of Ranvier as sodium ion channels are concentrated there.

The neurone (Schwann cell) cytoplasm conducts enough electrical charge to depolarise the next node so the impulse jumps from node to node.

Its very fast.

46
Q

What is the speed at which an impulse moves along a neurone called?

A

The conduction velocity. Higher = quicker.

47
Q

What is the role of acetylcholine?

A

A neurotransmitter involved in muscle contraction and the control of heart rate.

48
Q

How do neurotransmitters transmit nerve impulses between neurones? (short)

A
  1. An action potential triggers calcium influx
  2. Calcium influx causes neurotransmitter release.
  3. The neurotransmitter triggers an action potential in the post synaptic neurone.
49
Q

What happens for an action potential to trigger a calcium influx?

A
  1. Action potential arrives at the synaptic knob of the presynaptic neurone.
  2. The action potential stimulates voltage gated calcium ion channels in the presynaptic neurone to open.
  3. Calcium ions diffuse into the synaptic knob.
50
Q

What happens to cause the calcium influx to cause neurotransmitter release?

A
  1. Influx of calcium ions into the synaptic knob causes the synaptic vesicle to move to the presynaptic membrane. They then fuse with the presynaptic membrane.
  2. The vesicle release the neurotransmitter into the synaptic cleft (exocytosis)
51
Q

What causes the neurotransmitter to trigger an action potential in the postsynaptic neurone?

A
  1. Neurotransmitters diffuse across the synaptic cleft and binds to specific receptors on the post synaptic membrane.
  2. Causing sodium ion channels in the post synaptic neurone to open.
  3. The influx of sodium ions into the post synaptic membrane causes depolarisation. An action potential on the post synaptic membrane causes depolarisation. An action potential on the post synaptic membrane is generated if the threshold is reached.
  4. The neurotransmitter is removed from the synaptic cleft so the response doesn’t keep happening.
52
Q

What is synaptic divergence

A

When one neurone connects to many different neurones information can be dispersed to different parts of the body.

53
Q

What is synaptic convergence?

A

When many neurones connect to one neurone information can be amplified.

54
Q

What is summation?

A

Where the effect of neurotransmitters released from many neurones is added together.

55
Q

What is tropism?

A

The response of a plant to a directional stimulus

56
Q

What is positve tropism?

A

Growth towards the stimulus

57
Q

What is negative tropism?

A

Growth away from the stimulus.

58
Q

What is phototrophism?

A

Growth of a plant in response to light.

59
Q

What is geotrophism?

A

The growth of plants in response to gravity.

60
Q

What is IAA?

A

It is an auxin that’s produced in the tips of shoots in flowing plants. When it enters the nucleus of a cell, its able to regulate the transcription of genes related to cell elongation and growth.

61
Q

How does IAA move around plants?

A

Moves by diffusion and active transport over short distances and via the phloem over longer distances.

62
Q

What does uneven distribution of IAA mean?

A

There’s uneven distribution of IAA there will be uneven growth in the plant.

63
Q

How do plants detect light?

A

Using phytochromes (photoreceptors)

64
Q

What are the two states of phytochromes?

A

Red light and far red light

65
Q

What are the different states phytochromes are converted to and from when exposed to light?

A

Red light phytochrome is converted to Far red light phytochrome when exposed to red light.

Far red light phytochrome is converted to red light phytochrome when exposed to far red light

66
Q

What is converted in darkness?

A

Far red light is converted slowly into red light in darkness.

67
Q

What does daylight contain more of?

A

Red light (not far red light)

68
Q

How do phytochromes influence growth in plants?

A

The amount of FRL and RL changes depending of the amount of light eg day or night, summer or winter.

So differing amounts of RL and FRL control the responses to light by regulating the transcription of genes involved in these responses.

Biology Paper 3 (9 decks)

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