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Biology B5 > Homeostasis > Flashcards

Homeostasis Flashcards

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1
Q

What is Homeostasis?

A

Regulation of internal condition of cells to maintain a stable internal environment in response to both internal and external conditions.

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2
Q

What is Negative Feedback?

A

Negative feedback is an automatic process that counteracts any changes.

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3
Q

How does Negative feedback work?

A

A receptor detects the stimuli, whether something is too high or too low.
Sends it to the co-rd centre which organises a response.
The effector carries our the response.

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4
Q

Name the two CNS (co-rd centre)

A

Spinal chord and Brain.

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5
Q

How does the CNS coordinate a response?

A

Receptor (light receptor in brain) detect stimuli.
The sensory neurone carries this nerve impulse to the CNS.
Where the motor neurone carries the impulse to the effector which carries out the response.

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6
Q

Why are reflexes rapid and automatic?

A

Because they do not involve the conscious part of the brain.

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7
Q

What is a synapse?

A

Synapse connects 2 neurones.

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8
Q

What happens at a synapse?

A

The nerve impulse inside a neurone releases chemicals that diffuse across the synapse to the next neurone where the chemicals set off a new electrical impulse.

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9
Q

What happens in a reflex arc?

A

Stimuli detected by receptor
sensory neurone passes on the nerve impulse to the relay neurone in the CNS (spinal chord) via a synapse.
R-neurone passes impulses to the motor neurone.
M-neurone passes impulse onto the effector (muscle or gland) which carries out response.

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10
Q

Function of the cerebral cortex.

A

Responsible for consciousness, intelligence, memory and language.

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11
Q

Function of cerebellum.

A

Muscle corodination.

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12
Q

Function of Medulla

A

responsible for unconscious activities eg breathing.

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13
Q

Function of Hypothalamus.

A

Controls Body temp.

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14
Q

What is the overall function of the Brain?

A

The Brain is in charge of all our complex behaviours.

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15
Q

Describe the process of accommodation.

A

Accommodation is changing the shape of the lens to focus on near or distant objects.
To focus on a near object:
- Ciliary muscles contract–> slackens suspensory ligaments.
- Lens become fatter
- Increases the amount by which light is refracted.

To focus on a distant object:

  • Ciliary muscles relax—> suspensory ligaments pulled tight.
  • Lens go thin
  • Refract light by a smaller amount.
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16
Q

Explain how the iris reflex helps adjusting for bright/dim light.

A

Light receptors in the eye detect bright light —> reflex makes pupils smaller –> circular muscles contract —> radial muscles relax–> reduces the amount of light that can enter the eye.

Light receptors detect dim light—> reflex makes pupils dilated because radial muscles contract and the circular muscles relax.

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17
Q

Sclera.

A

The white part in the eye, tough, supporting wall of the eye.

18
Q

Cornea.

A

Transparent outer layer, refracts light into the eye.

19
Q

Iris.

A

Controls the size of the pupil and how much light enters the eye.

20
Q

Pupil

A

The hole through which light enters the eye.

21
Q

Lens.

A

Focuses light onto the retina.

22
Q

Retina.

A

Retina contains light receptors called rods and cones that are sensitive to light intensity and colour.

23
Q

Ciliary Muscles and Suspensory ligaments.

A

Control the shape of the lens.

24
Q

Optic Nerve.

A

Carries impulses from the receptors on retina to the brain.

25
Q

Long-sighted people (HYPEROPIA) are unable to focus on?

A

unable to focus on near objects.

26
Q

Short sighted people (Myopia) are unable to focus on?

A

unable to focus on distant objects.

27
Q

How to correct hyperopia?

A

When the lens doesn’t refract the light enough, or eyeball is too short.
Images of near objects are focused behind the retina.
Convex lens refracts the light rays so they focus on the retina.

28
Q

How to correct myopia?

A

When the lens refracts the light too much or the eyeball is too long.
Images of distant objects are focused in front of the retina.
Concave lens refracts light rays so they focus on the retina.

29
Q

Why do older people often have to use reading glasses?

A

As you get older, eyes’ lens lose flexibility,

so they cannot spring back to the round shape too easily, so the light cannot be focused well for near viewing.

30
Q

How do contact lenses work?

A

Contact lenses sit on the surface of the eye and focus the light by the right amount.

  • Hard lens: made of rigid material, last longer, removed overnight and kept sterile.
  • Soft lens: more comfortable, do not last as long.
31
Q

Why do hard lenses need to be kept sterile?

A

To prevent eye infections.

32
Q

Which lenses carry a higher risk of causing eye infection?

A

Soft lenses

33
Q

How does Laser Eye Surgery work?

A

Laser used to vaporise tissue,
Changing the shape of the cornea to change how strongly it refracts light
Slimming it down improves myopia.
Making it more powerful improves hyperopia.

34
Q

How does lens replacement surgery work?

A

Natural lens replaced by artificial lens, made of clear plastic.

35
Q

Complications during lens replacement surgery?

A

higher risk of damage to the retina, could lead to loss of sight.

36
Q

What is the function of the thermoregulatory centre in the brain?

A

Contains receptors that are sensitive to the blood flowing through the brain.
Receives info from temp receptors in skin. about skin temp.

37
Q

What is hyperthermia?

A

When body temp is too high, above 42 degrees, so enzymes denature.

38
Q

What is hypothermia?

A

When body temp is too low, 25 degrees, because there is not enough KE for enzyme reactions to take place.

39
Q

What is vasodilation?

A

too hot:

- Blood vessels near skin dilate (get larger) so more blood flows close to the skin so lots of heat is lost from skin.

40
Q

What is vasoconstriction?

A

too cold:
- Blood vessels supplying capillaries close off so capillaries get smaller as less blood flows through and little heat is lost from skin.

41
Q

What other ways does the body try to cool down when its too hot?

A
  • Removing insulation.
  • Sweat evaporating from skin.
  • hair erector muscle relaxed.
42
Q

What other ways does the body warm up when its too cold?

A
  • Hairs erect to trap insulating air.
  • No sweat.
  • Shivering (muscle contraction) which requires respiration and respiration transfers energy to warm the body.

Biology B5 (3 decks)

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