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IGCSE Biology > B7. Co-ordination and response > Flashcards

B7. Co-ordination and response Flashcards

1
Q

What is the ‘CNS’?

A

Stands for ‘Central Nervous System’;

Brain and spinal cord, which have role of coordination

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2
Q

What is the ‘PNS’?

A

Stands for ‘Peripheral Nervous System’; nerves, which connect all parts of the body to the CNS

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3
Q

Describe the human nervous system in terms of the central nervous (brain and spinal cord as areas of coordination) and the peripheral nervous system, which together serve to coordinate & regulate body functions.

A

 Sense organs are linked to the PNS; they contain groups of receptor cells;
 When exposed to a stimulus they generate an electrical impulse, which passes along peripheral nerves to the CNS, triggering a response.
 Peripheral nerves contain sensory and motor neurons;
 Sensory neurons transmit nerve impulses from sense organs to the central nervous system;
 Motor neurons transmit nerve impulses from the CNS to effectors (muscles or glands)
 Neurons are covered with a myelin sheath, which insulates them to make transmission of the impulse more efficient;
 Relay neurons pick up messages fromother neurons and pass them on to other neurons.
 The cytoplasm (mainly axon and dendron) is elongated to transmit the impulse for long distances.

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4
Q

Define ‘reflex action’

A

A reflex action is a fast, automatic response to a stimulis.

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5
Q

Describe the sequence of events of then reflex action.

A

Stimulus (sharp pin in finger) -> Receptor (pain receptors in skin) -> Coordination (spinal cord) -> Effector (biceps muscle) -> Response (biceps muscle contracts, hand is withdrawn from pin)

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6
Q

What is ‘blind spot’?

A

Part of the retina in front of the optic nerve that lacks rods or cones.

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7
Q

What is ‘optic nerve’?

A

Transmits electrical impulses from the retina to the brain.

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8
Q

What is ‘sclera’?

A

A tough, white layer that protects the eyeball.

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9
Q

What is ‘choroid’?

A

Produces a black pigment to prevent reflection of light inside the eye.

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10
Q

What is ‘retina’?

A

A light sensitive layer made of rods and cones.

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11
Q

What is ‘cornea’?

A

A transparent layer at the front of the eye that refracts the light entering to help to focus it.

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12
Q

What is ‘iris’?

A

A coloured ring of circular and radial muscle that controls the size of the pupil

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13
Q

What is ‘lens’?

A

A transparent, convex, flexible, jelly-like structure that refracts light to focus it.

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14
Q

What are ‘rods’?

A

Sensitive to dim light, do not respond to colour.

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15
Q

What are ‘cones’?

A

Function when the light is bright, able to distinguish between different colours of light.

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16
Q

What happens in bright light?

A
  • Circular muscles contract
  • Radial muscles relax
  • Pupil constricts
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17
Q

What happens in dim light?

A
  • Circular muscles relax
  • Radial muscles contract
  • Pupil dilates
18
Q

What happens to the eye when looking at a distant object?

A
  • Ciliary muscles relax
  • Lens become thin
  • Suspensory ligaments pulled tight
19
Q

What happens to the eye when looking a near object?

A
  • Ciliary muscles contract
  • Suspensory ligaments slacken
  • Lens get fatter
20
Q

Define ‘hormone’

A

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

21
Q

State the role of the hormone adrenaline in the chemical control of metabolic activity, including increasing the blood glucose concentration and pulse rate.

A
  • Secreted by adrenal glands located above each kidney
  • Helps us to cope with danger by increasing the heart rate
  • Thus supplying oxygen to brain and muscles more quickly, this increase the rate of metabolic activity and gives more energy for fighting or running away
  • The blood vessels in skin and digestive system contract so that they carry very little blood
  • Causes the liver to release glucose into the blood
22
Q

Examples of situations in which adrenaline secretion increases.

A
  • A man holding a gun to your head

- Examination

23
Q

What is ‘stimuli’?

A

Change in environment, detected by receptor cells.

24
Q

What is ‘nerve impulse’?

A

An electrical signal that passes along neurones (nerve cells).

25
Q

What are ‘receptor cells’?

A

Cells that are sensitive to stimuli.

26
Q

What are ‘effector cells’?

A

Cells that carry out responses to certain stimuli.

27
Q

What is a ‘response’?

A

A reaction of a organism to a specific stimulus.

28
Q

Describe the pathway of nerve impulses of voluntary actions.

A

Stimulus -> Receptor -> Spinal cord -> Brain -> Effector -> Response

29
Q

Describe the pathway of nerve impulses of involuntary actions (reflexes).

A

Stimulus -> Receptor -> Coordinator -> Effector -> Response

30
Q

What is the ‘coordinator’?

A

Part of the CNS that connects information from stimulus to effector.

31
Q

What are ‘sense organs’?

A

Group of receptor cells responding to specific stimuli.

32
Q

Define ‘phototropism’.

A

A response in which a plant grows towards or away from the direction from which light is coming.

33
Q

Define ‘geotropism’

A

A response in which a plant grows towards or away from gravity.

34
Q

What are ‘auxins’?

A

Plant hormones that control growth. Synthetic auxins are used as weedkillers by making the weeds grow too fast.

35
Q

Explain the effect of auxin to a plant’s growth in terms of geotropism.

A
  • If a shoot is placed horizontally in the absence of light, auxins accumulate on the lower side of the shoot, due to gravity;
  • This makes the cells on the lower side grow more quickly than on the upper side, so the shoot bends upwards - negative geotropism;
  • If a shoot is placed horizontally in the absence of light, auxins accumulate on the lower side of the root, due to gravity;
  • Thus the cells on the lower side grow more slowly than those on the upper side, so the root bends downwards - positive geotropism
36
Q

Explain the effect of auxin to a plant’s growth in terms of phototropism.

A
  • When a shoot is exposed to light from one side, auxins produced from the shoot tip towards the shaded side of the shoot;
  • Cells on shaded side stimulated to absorb more water than those on the light side;
  • Thus unequal growth causes the stem to bend towards light; positive phototropism
  • If a root is exposed to light in the absence of gravity, auxins produced by the root tip moves towards the shaded side of the root;
  • Cells on the shaded side are stimulaed to absorb less water than those on the light side;
  • Thus unequal growth causes the root to bend away from the light; negative phototropism
37
Q

Define ‘homeostasis’.

A

The maintenance of a constant internal environment.

38
Q

What happens to the body in cold environment?

A
  • Shivering - muscles in some parts of the body contract and relax very quickly. This produces heat and is called shivering.
  • Metabolism may increase
  • Hair stands up - this produces ‘goose flesh’ and traps a thicker layer of warm air next to the skin, acting as an insulator.
  • Vasoconstriction - the arterioles that supply the skin blood capillaries becomes narrower, thus less blood flows in them and thus less heat is lost to the air by radiation.
39
Q

What happens to the body in hot environment?

A
  • Hair lies flat - no insulation
  • Vasodilation - the arterioles that supply the skin blood capillaries gets dilated, thus more blood flows through them and thus heat is readily lost from the blood into the air by radiation;
  • Sweating - sweat gland secretes sweat on the surface of the skin, which evaporates, taking heat from the skin with it, thus cooling the body
  • Metabolism slows down
40
Q

Explain negative feedback.

A

Acts to ensure that the actual temperature is as close to the pre-set temperature as possile.

41
Q

Describe the role of insulin in controlling blood glucose levels.

A
  • When blood glucose levels are high, then insulin is secreted by pancreas.
  • Insulin passes in the bloodstream then to the liver;
  • Insulin stimulates the liver to absorb glucose;
  • Insulin converts glucose to glycogen;
  • Insulin also increases the rate of respiration; so more blood glucose is absorbed by cells and used up, to reduce blood glucose levels.
42
Q

Describe the role of glucagon in controlling blood glucose levels.

A
  • When blood glucose levels drop below normal, glucagon is secreted by the pancreas;
  • Glucagon passes in the bloodstream and then to the liver;
  • Glucagon converts glycogen to glucose in the liver
  • Glucose is then released into the bloodstream

IGCSE Biology (12 decks)

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