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Biology Topic 6A > Receptors > Flashcards

Receptors Flashcards

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1
Q

What do receptors do?

A

They are specific - they only detect one particular stimulus.

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2
Q

What can receptors be?

A
  • Cells (e.g. photoreceptor cells).

* Proteins (e.g. glucose receptors in pancreatic cell membranes).

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3
Q

What do some receptors detect?

A
  • Light
  • Glucose concentration
  • Pressure (e.g. pacinian corpuscle)
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4
Q

What do receptors in the nervous system do?

A

They convert energy of the stimulus into the electrical energy used by neurones.

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5
Q

How do receptors in the nervous system work?

A
  • Resting potential
  • Generator potential
  • Action potential
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6
Q

What is the resting potential of a nervous system receptor?

A

When a nervous system receptor is in its resting state (not being stimulated), there’s a difference in charge between the inside and outside of the cell.

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7
Q

What is the difference in charge in the resting potential of a nervous system receptor?

A

The inside is negatively charged relative to the outside, causing a voltage across the membrane.`

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8
Q

What is voltage also known as?

A

Potential difference

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9
Q

What is the resting potential?

A

The potential difference when a cell is at rest.

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10
Q

How is the resting potential generated?

A

By ion pumps and ion channels.

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11
Q

What does the relative charges either side of a receptor cell membrane at rest look like?

A

image

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12
Q

What is a generator potential?

A

The change in potential difference due to a stimulus.

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13
Q

How does a generator potential arise?

A

When a stimulus is detected, the cell membrane is excited and becomes permeable, allowing more ions to move in and out of the cell, altering the potential difference.

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14
Q

How is a bigger generator potential produced?

A

When a bigger stimulus excites the membrane more, causing a bigger movement of ions and a bigger change in potential difference.

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15
Q

What does a larger generator potential graph look like?

A

image

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16
Q

What happens if the generator potential is big enough?

A

It’ll trigger an action potential

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17
Q

What is an action potential?

A

An electrical impulse along a neurone

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18
Q

How is an action potential triggered?

A

If the generator potential reaches a certain level called the threshold level.

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19
Q

What are action potentials all?

A

One size

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20
Q

What does action potentials being all one size mean?

A

That the strength of the stimulus can be measured by the frequency of action potentials triggered during a certain time period.

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21
Q

Why are action potentials not always generated?

A

If the stimulus is too weak, the generator potential won’t reach the threshold, so there is no action potential.

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22
Q

What type of receptors are pacinian corpuscles?

A

Mechanoreceptors

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23
Q

What are mechanoreceptors?

A

They detect mechanical stimuli e.g. pressure and vibrations.

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24
Q

What does a graph showing generator potential reaching an action potential look like?

A

image

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25
Q

Where are pacinian corpuscles found?

A

In your skin

26
Q

How are pacinian corpuscles connected to the nervous system?

A

They contain a sensory nerve ending (the end of a sensory neurone).

27
Q

What is the sensory nerve ending protected by?

A

It is wrapped in loads of layers of connective tissue called lamellae.

28
Q

What happens when the pacinian corpuscle is stimulated (e.g. by a tap on the arm)?

A
  • The lamellae are deformed and press on the sensory nerve ending.
  • This causes the sensory neurone’s cell membrane to stretch.
  • This deforms the stretch-mediated sodium ion channels.
  • The channels then open and sodium ions diffuse into the cell, creating a generator potential.
  • If the generator potential reaches the threshold, it triggers an action potential.
29
Q

What does the stimulation of a pacinian corpuscle look like?

A

image

30
Q

What happens when there is a bigger stimulus to the pacinian corpuscles?

A
  • More pressure is applied, causing more sodium ion channels to open.
  • This creates a bigger generator potential
  • Meaning the generator potential is more likely to reach the threshold level and cause an action potential.
31
Q

What are photoreceptors?

A

Receptors in your eye that detect light.

32
Q

Where are photoreceptors cells in the eye?

A
  • In the retina.

* Lots of photoreceptors are in the fovea.

34
Q

What happens to the light detected by photoreceptors in the eye?

A

Nerve impulses from the photoreceptors cells are carried from the retina to the brain by the optic nerve.

35
Q

What is the optic nerve in the eye?

A

A bundle of neurones.

36
Q

What happens at the optic nerve in the eye?

A

Where the optic nerve leaves the eye is called the blind spot.

37
Q

Why is where the optic nerve leaves the eye called the blind spot?

A

Because there aren’t any photoreceptor cells (it is not sensitive to light).

38
Q

What does the cross-section of an eye look like?

A

image

39
Q

How do photoreceptors work in the eye?

A
  • Light enters the eye and hits the photoreceptors.
  • Light is absorbed by light-sensitive optical pigments.
  • Light bleaches the pigments, causing a chemical change, altering the membrane permeability to sodium ions.
40
Q

What happens in photoreceptors in the eye (like all other receptors) after the membranes permeability to sodium is altered?

A
  • A generator potential is created.

* If it reaches the threshold level, a nerve impulse is sent along a bipolar neurone.

41
Q

What is a bipolar neurone after a photoreceptor in the eye?

A

They connect photoreceptors to the optic nerve, which takes the impulses to the brain.

42
Q

What does nervous communication in the eye look like?

A

image

43
Q

What are the two types of photoreceptors in the eye?

A
  • Rods

* Cones

44
Q

Where are rods photoreceptors found in the eye?

A

In the peripheral parts of the retina.

45
Q

Where are cones photoreceptors found in the eye?

A

Packed together in the fovea.

46
Q

Why are rods and cones photoreceptors different?

A

They contain different optical pigments, making them sensitive to different wavelengths of light.

47
Q

What information do rods photoreceptors give?

A

Information in black and white (monochromatic vision).

48
Q

What information do cones photoreceptors give?

A

Information in colour (trichromatic vision).

49
Q

What are the three types of cones photoreceptors?

A
  • Sensitive to red optical pigments.
  • Sensitive to green optical pigments.
  • Sensitive to blue optical pigments.
50
Q

What happens when the different cones cells are stimulated?

A

If they’re stimulated in different proportions, you see different colours.

51
Q

What does the location of rods and cones photoreceptors in the eye look like?

A

image

52
Q

How does light reach the photoreceptors in the eye?

A
  • Light enters the eye through the pupil.
  • The amount of light that enters is controlled by the muscles of the iris.
  • Light rays are focused by the lens onto the retina (inside the eye).
53
Q

What is the difference between rods and cones towards light?

A

Rods are very sensitive to light and cones are less sensitive.

54
Q

What happens because rods photoreceptors are more sensitive to light?

A

They fire action potentials in dim light.

55
Q

How do rods photoreceptors fire action potentials in dim light?

A

Because many rods join one bipolar neurone, so many weak generator potentials combine to reach the threshold level and trigger an action potential.

56
Q

What happens because cones photoreceptors are less sensitive to light?

A

They only fire action potentials in bright light.

57
Q

How do cones photoreceptors only fire action potentials in bright light?

A

Because one cones joins one bipolar neurone, so it takes more light to reach the threshold level and trigger an action potential.

58
Q

What is visual activity?

A

The ability to tell apart points that are close together.

59
Q

What is the difference in visual activity between rods and cones?

A
  • Rods give low visual activity

* Cones give high visual activity

60
Q

Why do rods photoreceptors give low visual activity?

A

Because many rods join the same bipolar neurone, meaning light from two points close together can’t be told apart.

61
Q

Why do cones photoreceptors give high visual activity?

A

Because cones are close together and one cone joins one bipolar neurone.

62
Q

Why does cones being close together give high visual activity?

A

When light from two points hits two cones, two action potentials go to the brain (one from each), so you can distinguish them apart as two separate points.

Biology Topic 6A (5 decks)

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