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IGCSE Biology > Chapter 13: Coordination and response > Flashcards

Chapter 13: Coordination and response Flashcards

1
Q

What is a nerve impulse?

A

is an electrical impulse that passes along nerve cells called neurones

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2
Q

what is a stimulus?

A

It is a change in an organism’s environment that can be detected by a sense organ.

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3
Q

What is a receptor?

A

It is a cell that is able to detect changes in the environment; often part of a sense organ.

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4
Q

What is an effector?

A

Is the part of the body that responds to a stimulus; e.g a muscle or gland.

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5
Q

What is a neuron?

A

a nerve cell; a cell specialized for the rapid transfer of electrical impulses.

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6
Q

what is an axon?

A

a nerve fire that conducts impulses away from the cell body.

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7
Q

what is are nerve impulses?

A

an electrical signal that sweeps along a neuron

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8
Q

Name all the parts of a neuron.

A
  • dendrite
  • axon
  • myelin sheath
  • nucleus that makes the myelin sheath
  • cell cytoplasm
  • cell membrane
  • Node of Ranvier
  • nerve ending
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9
Q

Describe the movement of an impulse through a neuron

A
  • The dendrite picks up the electrical impulse.
  • It passes through the cell body and along an axon
  • The impulse travels through it before passing onto a nerve ending and may pass to another neuron.
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10
Q

what is Myelin?

A

It is a fatty substance surrounding the axons of many neurons, enabling the nerve impulse to travel faster.

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11
Q

what is the central nervous system?

A

is the brain and the spinal chord

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12
Q

Describe the effect of a stimulus on the central nervous system

A
  • The receptor receives the stimulus.
  • Electrical impulse is sent to the brain or spinal cord.
  • Impulse is sent to appropriate nerve fibre.
  • Impulse is sent to the effector.
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13
Q

what is the peripheral nervous system?

A

Includes all the nerves in the body, not including the brain or spinal chord.

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14
Q

Describe a typical reflex arc.

A
  1. A stimulus, such as heat from a flame, is detected by receptors.
  2. The receptor sends an impulse down the sensory neuron to the spinal cord.
  3. The relay neurone in the CNS passes the impulse to the motor neurone.
  4. The impulse travels along the motor neuron to an effector (e.g. a muscle), which reacts
    to remove the organism from the danger.
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15
Q

What is a reflex action?

A

It is a fast, automatic response to a stimulus

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16
Q

What are voluntary actions and involuntary actions?

A

voluntary actions are actions that require a conscious decision.
An Involuntary action are actions carried out automatically, without a conscious thought.

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17
Q

where are the cell bodies of each of these types of neurons:

a. sensory neuron
b. relay neuron
c. motor actions

A

a. in a small swelling, just outside the spinal cord.
b. in the central nervous system - either the brain or the spinal chord
c. in the central nervous system -either the brain or the spinal chord

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18
Q

what is a synaptic cleft?

A

it is a tiny gap between two neurons

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19
Q

what is a synapse?

A

A junction between two nerve cells, consisting of a minute gap across which impulses pass by the diffusion of a neurotransmitter.

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20
Q

what is a vesicle?

A

a very small vacuole.

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21
Q

what is the transmitter substance or neurotransmitter?

A

is a chemical that carries a nerve impulse across a synapse.

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22
Q

Describe what happens to the nerve impulse when it arrives at the synaptic cleft.

A
  • vesicles containing neurotransmitter move to the cell membrane of the sensory neuron
  • the vesicles burst open and empty the neurotransmitter into the synaptic cleft.
  • the neurotransmitter diffuses across the cleft
  • the neurotransmitter molecules slot into their receptors on the membrane of the relay neuron.
  • this sets off s nerve impulse in the relay neuron.
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23
Q

Why can nerve impulses travel in only one direction?

A

Because the neurotransmitter is only present on one side of the synapse.

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24
Q

What is a sense organ?

A

Is a group of cells responding to specific stimuli: light, sound, touch, temperature and chemicals.

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25
Q

What is the retina of the eye?

A

The part of the eye that contains the receptor cells.

26
Q

What is the orbit, when speaking about the eye?

A

Is the bony socket in which the eye is set. It covers most of the eye, but leaves out the very front of it.

27
Q

What is the conjunctiva?

A

-Is the thin transparent membrane that covers the eye which protects the parts behind it.

28
Q

A fluid covers the conjunctiva, what is is it and why is it there?

A
  • It is a fluid made by the tear glands
  • it contains lysozyme which can kill bacteria.
  • It keeps dirt away from the eye when it is washed over the eye.
29
Q

Why do we have eyebrows,eyelashes and eyelids?

A

To help stop dirt from landing on the eye

30
Q

What is the sclera?

A

Is thick, tough coat that surrounds the orbit to protect the eye.

31
Q

What is the blind spot?

A

Is the area where the optic nerve leaves the retina. There are nor receptor cells here.
No impulses will be sent to the brain when light lands on here.

32
Q

What is the Choroid?

A

Is a black layer behind the retina that absorbs all the light once its been through the retina so that it does not scatter around inside the eye

33
Q

What are the two types of receptor cells in the retina?

A

rod and cone.

34
Q

What is a rod cell?

A

Is a light sensitive cell in the retina, that responds to dim light.

35
Q

What are cone cells?

A

is a light sensitive cell in the retina that responds to light of a specific colour.

36
Q

What is the most common receptor cell in the fovea?

A

cones.

37
Q

Explain why some images are less detailed than others?

A

Cone cells are tightly packed in the fovea. These produce a detailed image when we look directly at it.
Rods are found further out on the retina and are less tightly packed, and so produce a less detailed image.

38
Q

What is the iris?

A

It is the coloured part of the eye, which controls the amount of allowed through to the lens and retina.

39
Q

Describe what happens to the pupils at low light intensities

A

The pupil dilates to allow more light to

enter the eye by contracting the circular muscles.

40
Q

Describe what happens to the pupil at higher light intensities.

A

The pupil constricts to limit the amount of light entering the eye by the radial muscles contracting. This is to prevent the eye being damaged by the bright light.

41
Q

What is meant by the accommodation of light eye?

A

The change in shape of the lens, in order to focus on objects at different distances.

42
Q

Describe how and what happens during the accommodation of the eye.

A

The shape of the lens is changed,This is controlled by ciliary muscles and suspensory ligaments. These work
antagonistically.
The shape of the lens, as well as its curvature, is altered to change the way
light is refracted onto the retina, focusing the image.

43
Q

What is suspensory ligaments?

A

Are rings of ligaments linking ciliary muscles to the lens.

44
Q

What is ciliary muscle?

A

Are rings of muscle around the lens which change shape.

45
Q

How does the eye focus on nearby objects?

A

The ciliary muscles contract whilst the suspensory ligaments relax,
making the lens bulge,where it is fatter an curved.

46
Q

How does the eye focus on distant muscles?

A

The ciliary muscles relax whilst

the suspensory ligaments pull tight, making the lens thinner and less curved.

47
Q

What is meant by a hormone?

A

A chemical substance produced by a gland, carried by the blood, which alters the activity of one or more specific target organs.

48
Q

What is the endocrine system?

A

Is the system in the body that produces and secretes hormones.

49
Q

What are endocrine glands?

A

The ductless glands that secrete hormones into the blood and together make up the endocrine system

50
Q

Identify specific endocrine glands and their

secretions

A

adrenal glands and adrenaline
pancreas and insulin
testes and testosterone
ovaries and oestrogen

51
Q

Describe adrenaline

A

the hormone secreted in ‘fight or flight’ situations

52
Q

Describe the effects of adrenaline on the body

A
  • increased breathing and pulse rate
  • widened pupils
  • secretion of glucose from the liver into the blood for energy in muscle contraction.
53
Q

Give examples of situations in which adrenaline

secretion increases

A
  • writing an exam
  • being left alone in a horror house
  • riding a roller coaster
  • realising that you wore your trousers backwards halfway through the school day.
54
Q

Compare nervous and hormonal control systems

in terms of speed and longevity of action

A
  • Hormones travel slower than electrical impulses as they travel to their target organs while electrical impulses travel along nerve fibres.
  • Hormones act for longer as they remain in the blood while impulses act for only an instant in time.
55
Q

State the functions of insulin, oestrogen and

testosterone

A
  • Insulin: causes liver to reduce concentration of glucose in the blood.
  • Testosterone: produces male secondary sexual characteristics.
  • Oestrogen: Produces female secondary sexual characteristics; helps to regulate menstrual cycle.
56
Q

Define geotropism.

A

response in which parts of a plant grow towards or away from gravity

57
Q

Define phototropism

A

a response in which parts of a plant grow towards or away from the direction from which light is coming

58
Q

Investigate gravitropism in shoots and roots

A
  • If a plant is laid on its side, the auxin gathers in the lower half o the stem and root.
  • Auxin slows growth to the root, so the root curves downwards.
  • Auxin stimulates growth in the shoot so it causes it to grow upward.
59
Q

Explain the role of auxin in controlling shoot

growth

A

– auxin made in shoot tip (only)
– auxin spreads through the plant from the
shoot tip
– auxin is unequally distributed in response to
light and gravity
– auxin stimulates cell elongation

60
Q

Describe the use in weedkillers of the synthetic

plant hormone 2,4-D

A

It disrupts the weed’s growth and kills them

61
Q

Describe the use in weedkillers of the synthetic

plant hormone 2,4-D

A

It disrupts the weed’s growth and kills them

62
Q

Investigate phototropism in shoots and roots.

A
  • Auxin spreads equally, down both sides of the plant.

- Auxin collects of the shady side

IGCSE Biology (23 decks)

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