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BIOLOGY A LEVEL > TOPIC 6A > Flashcards

TOPIC 6A Flashcards

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1
Q

Define a stimulus

A

Any change in the internal or external environment.

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2
Q

What is a receptor?

A

Receptors are specific - they only detect one particular stimulus, e.g. light, pressure or glucose concentration.

There are loads of different types of receptors that detect different stimuli.

Some receptors are cells, e.g. photoreceptors are receptor cells that are connected to the nervous system.

Some receptors are proteins on cell surface membranes , e.g. glucose receptors are proteins on cell surface membrane sand some pancreatic cells.

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3
Q

What is an effector?

A

Cells that bring about a response to a stimulus, to produce an effect. Effectors include muscle cells and cells found in glands, e.g. the pancreas.

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4
Q

What are the 3 main types of neurones?

A
  • Sensory neurones
  • Motor neurones
  • Relay neurones
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5
Q

What do sensory neurones do?

A

Sensory neurones transmit electrical impulses from receptors to the CNS.

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6
Q

What is the Central Nervous System (CNS) made up of?

A
  • Brain

- Spinal cord

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7
Q

What do motor neurones do?

A

Motor neurones transmit electrical impulses from the CNS to effectors.

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8
Q

What do relay neurones do?

A

Relay neurones transmit electrical impulses between sensory neurones and motor neurones.

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9
Q

Describe the process of how a stimulus turns into a response in an organism.

A
  • A stimulus is detected by receptor cells and an electrical impulse is sent along a sensory neurone.
  • When an electrical impulse reaches the end of a neurone, chemicals called neurotransmitters take the information across to the next neurone, which then send an electrical impulse.
  • The CNS (the coordinator) processes the information and sends impulses along motor neurones to an effector.

(see page 128 in the revision guide)

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10
Q

What is the peripheral nervous system made up of?

A

The neurones that connect the CNS to the rest of the body.

It also has two different systems:

  • The somatic nervous system
  • The autonomic nervous system
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11
Q

What is the somatic nervous systemic control of?

A

Controls the conscious activities, e.g. running and playing video games.

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12
Q

What is the autonomic nervous system in control of?

A

Controls the unconscious activities, e.g. digestion.

Its got 2 divisions that have opposite effects on the body:

  • The sympathetic nervous system
  • The parasympathetic nervous system
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13
Q

What does the sympathetic nervous system do?

A

Gets the body ready for action.

The ‘fight or flight’ system.

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14
Q

What does the parasympathetic nervous system do?

A

Calms the body down.

The ‘rest and digest’ system.

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15
Q

Define a reflex.

A

A reflex is where the body responds to a stimulus without making a conscious decision to respond.

They are rapid, automatic responses to stimuli.

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16
Q

How do simple reflexes protect an organisms body?

A

Simple reflexes help organisms to protect the body because they’re rapid.

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17
Q

What is a reflex arc?

A

The pathway of neurones linking receptors to effectors in a reflex is called a reflex arc.

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18
Q

Describe the reflex arc that occurs when a hand touches a hot pan.

How could the person withstand the heat and keep their hand there?

A

(see green box on page 129 in the revision guide)

If there is a relay neurone involved in the simple reflex arc then its possible to override the reflex.

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19
Q

How is the nervous system:

  • localised
  • short-lived
  • rapid
A

(see page 129 in the revision guide)

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20
Q

Give 3 examples of how some plants can increase their chance of survival by responding to changes in their environment.

A

(see page 130 in the revision guide)

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21
Q

Define a tropism of a plant

A

A tropism is a response of a plant to a directional stimulus.

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22
Q

What is a positive and negative tropism?

A

Plants respond to stimuli by regulating their growth.

POSITIVE TROPISM
Growth towards the stimulus

NEGATIVE TROPISM
Growth away from the stimulus

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23
Q

What is phototropism in a plant?

A

Phototropism is the growth of a plant in response to light.

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24
Q

Are the shoots of a plant negatively or positively phototropic?

A

Shoots are positively phototropic and grow towards light.

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25
Q

Are the roots of a plant negatively or positively phototropic?

A

Roots are negatively phototropic and grow away from light.

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26
Q

What is gravitropism in a plant?

A

Gravitropism is the growth of a plant in response to gravity.

27
Q

Are the shoots of a plant negatively or positively gravitropic?

A

Shoots are negatively gravitropic and grow upwards.

28
Q

Are the roots of a plant negatively or positively gravitropic?

A

Roots are positively gravitropic and grow downwards.

29
Q

What are growth factors in plants?

A

Plant respond to directional stimuli using specific growth factors - these are hormone like chemicals that speed up or slow down plant growth.

30
Q

Where are growth factors produced in a plant?

A

Growth factors are produced in the growing regions of the plant (e.g. shoot tips and leaves) and they more to where they’re needed in other parts of the plant.

31
Q

What are auxins?

A

Growth factors called auxins stimulate the growth of shoots by cell elongation - this is where cell walls become loose and stretchy, so the cell gets longer.

High concentrations of auxins inhibit growth in roots, though.

32
Q

Where is indoleacetic acid (IAA) produced in plants?

A

Indoleacetic acid (IAA) is an important auxin that is produced in the tips of shoots flowering plants.

33
Q

Describe how indoleacetic acid (IAA) works on shoots and roots of a plant for phototropism and gravitropism.

A

(see page 130 in the revision guide)

34
Q

What is a tactic response (taxes) in organisms?

A

The organism moves towards or away from a directional stimulus, e.g. light.

(see page 131 in the revision guide for an example)

35
Q

What is kinetic response (kinesis) in organisms?

A

The organism’s movement is affected by a non-directional stimulus, e.g. humidity.

(see page 131 in the revision guide for an example)

36
Q

How would you investigate animal responses in choice chambers? (experiment)

A

(see page 131 in the revision guide)

37
Q

Describe how receptor cells communicate information via the nervous system, (potential differences kinda stuff)

A

(see page 132 in the revision guide)

38
Q

What are pacinian corpuscles and where are they found?

Draw and label one.

A

Pacinian corpuscles are mechanoreceptors (pressure receptors) - they detect mechanical stimuli, e.g. pressure vibrations. They’re are found in your skin.

39
Q

Describe what happens in a pacinian corpuscle when it is stimulated.

A

(see page 132 in the revision guide)

40
Q

In the eye, what is a fovea?

A

The fovea is an area of the retina where there are lots of photoreceptors.

41
Q

Draw and label an eye.

A

(see page 132 in the revision guide)

42
Q

Where do nerve impulses go from the eye?

A

(see page 132 in the revision guide)

43
Q

Where in the eye are rods found?

A

Rods are mainly found in the peripheral parts of the retina

44
Q

Where in the eye are cones found?

A

Cones are found packed together in the fovea.

45
Q

What are the differences between rods and cones in the eye?

A

Rods:
- Give information in black and white (monochromatic vision)

Cones:
- Give information in colour (trichromatic vision)

Rods and cones contain different optical pigments making them sensitive to different wavelengths of light.

46
Q

What 2 types of photoreceptors are found in the eye?

A

Rods

Cones

47
Q

What are the 3 types of cones in the eye?

A

There are 3 types of cones each containing a different optical pigment:

  • red-sensitive
  • green-sensitive
  • blue-sensitive

When they are stimulated in different proportions you see different colours.

48
Q

Draw the pathway of how light reaches photoreceptors from the eye.

A

(see page 133 in the revision guide)

49
Q

Which is the more sensitive photoreceptor:

rods
cones

why?

A

Rods

see page 133 in the revision guide

50
Q

Which has more visual acuity (the ability to tell apart points that are close together):

rods
cones

why?

A

cones

see page 133 in the revision guide

51
Q

The cardiac (heart) muscle is myogenic, what does this mean?

A

It can contract and relax without receiving signals from nerves.

This pattern of contractions controls the regular heart beat.

52
Q

Where in the heart its the sinoatrial node (SAN) found?

A

The wall of the right atrium.

53
Q

What in the heart does the sinoatrial node (SAN) do?

A

The SAN is like a pacemaker - It sets the rhythm of the. heartbeat by sending out regular waves of electrical activity to the atrial walls.

It generates electrical impulses which cause the cardiac muscles to contract.

54
Q

What in the heart is the atrioventricular node (AVN) responsible for?

A

The AVN is responsible for passing the waves of electrical activity onto the bundle of His.

55
Q

What are the bundle of HIS in the heart?

A

The bundle of His is a group of muscle fibres responsible for conducting the waves of electrical activity between the ventricles to the apex (bottom) of the heart.

The bundle splits into finer muscle fibres in the right and left ventricle walls, called the purkyne tissue.

56
Q

In the heart what does the purkyne tissue do?

A

The purkyne tissue carries the waves of electrical activity into the muscular walls of the right and left ventricles, causing them to contract simultaneously, from the bottom up.

57
Q

Describe the process of how the nodes and muscles in the heart regulate the rhythm of heartbeat.

A

(see page 134 in the revision guide)

58
Q

What is the role of the medulla oblongata?

A

The rate at which the SAN fires (i.e. heart rate) is unconsciously controlled by part of the brain called the medulla oblongata.

Animals need to alter their heart rate to respond to internal stimuli, e.g. to prevent fainting due to low blood pressure or to make sure the heart rate is high enough to supply the blood with enough oxygen.

59
Q

What receptors are stimulated by high and low blood pressure?

A

There are pressure receptors called baroreceptors in the aorta and the carotid arteries (major arteries in the neck).

60
Q

What receptors monitor oxygen levels in the blood and also carbon dioxide and pH (which are indicators of O2 level)

A

There are chemical receptors called chemoreceptors in the aorta, the carotid arteries and in the medulla.

61
Q

Describe the process and pathway of when high blood pressure is detected and how to gets to a response.

A

(see page 135 in the revision guide)

62
Q

Describe the process and pathway of when high blood O2, low CO2 or high pH levels is detected and how to gets to a response.

A

(see page 136 in the revision guide)

63
Q

Describe the process and pathway of when low blood O2, high CO2 or low pH levels is detected and how to gets to a response.

A

(see page 136 in the revision guide)

64
Q

Describe the process and pathway of when low blood pressure is detected and how to gets to a response.

A

(see page 136 in the revision guide)

BIOLOGY A LEVEL (19 decks)

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