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Biology > Homeostasis 1 > Flashcards

Homeostasis 1 Flashcards

Overview, The Nervous system, The eye, Thermoregulation.

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1
Q

Homeostasis

A

The regulation of the internal conditions of a cell or organism to maintain optimum conditions for function in response to internal and external changes.

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2
Q

Why do the internal conditions of your body need to be regulated?

A

To maintain the optimum conditions for cells to function properly and for enzyme action.

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3
Q

What does homeostasis include the control of in the human body?

A

-Blood glucose concentration

-Body temperature

-Water levels

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4
Q

What do automatic control systems do?

A

Regulate your internal environment.

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5
Q

What can automatic control systems involve?

A

-Nervous responses

-Chemical responses

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6
Q

What do all control systems include?

A

-Receptor cells

-Coordination centres

-Effectors

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7
Q

Receptors

A

Cells which detect stimuli

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8
Q

Stimuli

A

Changes in the (internal or external) environment

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9
Q

Give examples of coordination centres in the human body.

A

-Brain

-Spinal Chord

-Pancreas

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10
Q

What do coordination centres do?

A

Receive and process information from receptors.

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11
Q

What two things can effectors be?

A

-Muscles
-Glands

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12
Q

What do effectors do?

A

Bring about responses which restore optimum levels.

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13
Q

Examples of negative feedback

A

-The control of blood glucose concentration

-The control of body temperature

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14
Q

In what order are signals passed along the control system?

A

receptor ➔ coordination centre ➔ effector

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15
Q

What do muscles do when stimulated?

A

Contract

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16
Q

What do glands do when stimulated?

A

Secrete hormones

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17
Q

Why does the endocrine system act more generally across the body?

A

It involves releasing hormones into the blood stream which means they spread throughout the entire body.

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17
Q

Why is the nervous system much faster acting than the endocrine system?

A

It relies on electrical impulses that can travel very quickly.

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18
Q

Homeostasis relies on a system of what?

A

negative feedback

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19
Q

Negative feedback

A

A mechanism which your automatic control systems use to keep your internal environment stable.

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20
Q

How does negative feedback work?

A

Any change in a system causes an action that reverses the change.

Whenever the levels of something get too high they’re brought back down, and whenever the levels of something get too low, they’re brought back up.

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21
Q

What does the nervous system enable humans to do?

A

React with their surroundings and coordinate their behaviour.

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22
Q

What is the CNS?

A

Central nervous system.

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23
Q

What is the central nervous system made of in vertebrates? (animals with backbones)

A

-Brain
-Spinal chord

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24
Q

How does information from receptors pass along neurones? (cells)

A

As electrical impulses

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25
Q

Where does information from receptors go?

A

(As electrical impulses) to the central nervous system (CNS).

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26
Q

What does the CNS coordinate?

A

The response of effectors.

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27
Q

What are sensory neurones?

A

Cells which carry information as electrical impulses from the receptors to the CNS.

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28
Q

What are motor neurones?

A

The neurones that carry electrical impulses from the CNS to effectors.

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29
Q

What are the 4 parts of the nervous system?

A

-Receptors
-Brain
-Spinal chord
-Neurones

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30
Q

Briefly describe what happens in the nervous response.

A

Impulses from receptors pass along sensory neurones to the brain or spinal chord (CNS).

The CNS coordinates a response, and impulses are sent along motor neurones to the effector muscles.

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31
Q

What is the role of the nervous system?

A

To detect and respond to stimuli.

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32
Q

What are the type of receptor?

A

-Light
-Touch
-Temperature
-Pressure
-Pain
-Position
-Sound
-Chemical

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33
Q

What types of receptor are found in the skin?

A

-Touch
-Pain
-Temperature
-Pressure

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34
Q

What type of receptor is found in the eyes?

A

Light

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35
Q

What type of receptor is found in the ears?

A

-Sound
-Pressure

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36
Q

Where are chemical receptors found?

A

-Nose
-Tongue

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37
Q

What is the difference between a neurone and a nerve?

A

A neurone is a specialised cell through which an electrical impulse is sent, whereas a nerve is a bundle of hundreds of thousands of neurones.

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38
Q

What do effectors do?

A

Produces a specific response to a detected stimulus, bringing about a change.

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39
Q

What is the role of a relay neurone?

A

To transfer a signal from a sensory neurone to a motor neurone.

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40
Q

Pathway of a reflex arc?

A

stimulus ➔ receptor ➔ sensory neurone ➔ relay neurone ➔ motor neurone ➔ effector ➔ response

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41
Q

Pathway of information to the brain?

A

stimulus → receptor → coordinator → effector → response

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42
Q

Why is it that only large, multicellular organisms have complex nervous systems?

A

For simple (or single-celled) organisms, everything they do is a reflex response.

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43
Q

What is even quicker than neurones transmitting information to the brain, and your brain deciding how to respond to a stimulus?

A

Reflexes

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44
Q

What is a synapse?

A

The connection between two neurones.

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45
Q

How is a nerve/electrical signal transferred across a synapse?

A

When an electrical signal reaches the end of a neuron, this triggers chemicals to diffuse across the synapse (the gap).

These chemicals then set off a new electrical signal in the next neurone.

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46
Q

What are reflexes?

A

Rapid, automatic responses to stimuli that don’t involve the conscious part of the brain.

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47
Q

Why are reflexes important?

A

-They protect you from harm

-They control basic bodily functions

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48
Q

Give an example of a reflex action that protects a person from harm.

A

Your pupils constrict if there’s too much light (e.g. if someone shines a torch in your eye) to protect the retina becoming damaged.

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49
Q

Why is it important that reflexes control basic bodily functions e.g. breathing?

A

So that we don’t have to be alert all of the time.

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50
Q

The passage of information in a reflex (from receptor to effector) is called what?

A

A reflex arc.

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51
Q

Where do we find synapses?

A

-Between a sensory and relay neurone

-Between a relay and motor neurone

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52
Q

What part of the CNS is used in a reflex response?

A

-Spinal chord
-Unconscious part of the brain

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53
Q

Why is the brain not used in reflex responses?

A

Because you don’t have to think about the response which makes it quicker.

54
Q

What happens to receptors?

A

They are stimulated.

55
Q

What does the brain control and coordinate?

A

Complex behaviour.

56
Q

What is the brain made up of?

A

Billions of interconnected neurones.

57
Q

What are the different regions of the brain?

A

-Cerebral cortex

-Cerebellum

-Medulla

-Spinal chord

58
Q

Cerebral cortex

A

-The outer wrinkly bit

-Responsible for consciousness, intelligence, memory, language, and interpreting senses like hearing and vision

59
Q

Cerebellum

A

Responsible for muscle coordination and balance.

60
Q

Medulla

A

-Found in the brain stem

-Controls unconscious activities such as regulating our breathing rate and heart rate

61
Q

What methods can neuroscientists use to study the brain/map regions of the brain?

A

-Studying patients with brain damage

-Electrically stimulating the brain

-MRI scans

62
Q

Studying patients with brain damage

A

-For when a small part of the brain has been damaged

-This will have an effect on the patient

-This tells neuroscientists a lot about what the damaged region of the brain does

63
Q

Studying patients with brain damage example

A

If an area at the back of the brain was damaged by a stroke and the patient went blind, you know that area has something to do with vision.

64
Q

Electrically stimulating the brain

A

-A tiny electrode us pushed into the brain tissue and running a small current through it

-Neuroscientists observe what stimulating different parts of the brain does to obtain an understanding of what those parts do.

65
Q

Electrically stimulating the brain example

A

When a region of the brain known as the motor area is stimulated, it causes muscle contraction and movement.

66
Q

MRI scans

A

-The machine produces a very detailed picture of the brain’s structures

-Scientists use this to find out which areas of the brain are active when people are doing things like listening to music or trying to recall a memory

67
Q

What does MRI stand for?

A

Magnetic resonance imaging (scanner)

68
Q

Knowledge of how the brain works has led to the development of what?

A

Treatments for disorders of the nervous system.

For example, electrical stimulation of the brain can help reduce muscle tremors caused by nervous system disorders such as Parkinson’s disease.

69
Q

Why is investigating and treating brain disorders difficult?

A

Due to the complexity and delicacy of the brain…

70
Q

Risks of investigating/treating the brain.

A

-Physical damage to the brain

-Increased problems with brain function such as difficulties with speech

71
Q

Hypothalamus

A

The thermoregulatory centre is located here.

It regulates our body temperature.

72
Q

What are the 3 main reasons that treating the brain is so difficult?

A

-There is a huge range of things that can go wrong, from mental illness to infection

-It is encased within the skull, so is hard to access

-It is very complicated, so hard to target with medications

73
Q

What is the eye?

A

A sense organ containing receptors sensitive to light intensity and colour.

74
Q

Sclera

A

The tough, white, supporting wall of the eye.

75
Q

Cornea

A

The transparent, dome-shaped tissue covering the front of the eye.

76
Q

Which parts of the eye refract light?

A

-Cornea

-Lens

77
Q

Iris

A

The coloured part of the eye.

It contains muscles which allow it to control the diameter of the pupil and therefore how much light enters the eye.

78
Q

Pupil

A

The gap in the middle of the iris which light passes through to meet the lens.

It changes shape as the amount of light changes.

79
Q

Lens

A

A crystalline structure located just behind the iris.

It focuses light onto the retina.

80
Q

Retina

A

Sensory tissue that lines the back of the eye.

81
Q

What is the shape of the lens controlled by?

A

-Ciliary muscles

-Suspensory ligaments

82
Q

Optic nerve

A

The nerve that transmits electrical impulses from receptors on the retina to the brain.

83
Q

What does the retina contain?

A

Millions of photoreceptors (rods and cones) that convert light rays into electrical impulses.

The impulses are then relayed to the brain via the optic nerve.

84
Q

Vitreous fluid

A

A thick, transparent liquid that fills the centre of the eye.

It is mostly water and gives the eye its form and shape.

85
Q

Suspensory ligaments

A

Hold the lens in place and work with the ciliary muscles to change the shape of the lens.

86
Q

Ciliary muscles

A

Attached to the suspensory ligaments, these work with them to control the shape of the lens.

87
Q

Accommodation

A

The process of changing the shape of the lens to focus on near or distant objects.

(It is a reflex)
(It changes the refractive power of the lens)

88
Q

Which light-sensitive cells in the retina enable you to see in colour?

A

Cone cells

89
Q

Which two stimuli are the receptor cells of the eye sensitive to?

A

-Colour

-Light intensity

90
Q

Which light sensitive cells in the retina enable you to see in the dark?

A

Rod cells.

They are very sensitive, but can only detect the presence or absence of light.

This means they help us see in low light environments like night time, but they can’t see in colour

91
Q

Fovea

A

The point where light focuses on the retina.

This region contains the highest concentration of cone cells and gives the sharpest image.

92
Q

What is the purpose of the iris reflex?

A

To ensure the optimum amount of light enters the eye.

93
Q

What happens to the circular and radial muscles when the pupil constricts?

A

The circular muscle contracts and the radial muscle relaxes.

94
Q

Why does the pupil constrict when it’s bright?

A

Too much light can damage your retina, so in bright light, your pupil will constrict to let less light through.

95
Q

What happens to the circular and radial muscles when the pupil dilates?

A

The circular muscle relaxes and the radial muscle contracts.

This makes the pupil larger to let more light through to the retina.

96
Q

Which muscles are closer to the pupil - circular or radial muscles?

A

Circular

97
Q

How does the eye accommodate to focus on a nearby object?

A
  • the ciliary muscles contract
  • the suspensory ligaments slacken
  • the lens is then thicker and refracts light rays strongly

*Light rays come to a point on the retina

98
Q

How does the eye accommodate to focus on a distant object?

A
  • the ciliary muscles relax
  • the suspensory ligaments are pulled tight
  • the lens is then pulled thin and only slightly refracts light rays

*Light rays come to a point on the retina

99
Q

Name two common defects of the eye

A

-Myopia (short-sightedness)

-Hyperopia (long-sightedness)

100
Q

What causes eye defects?

A

If the lens cannot refract light rays by the right amount.

This means they do not focus on the retina.

101
Q

How are eye defects generally treated?

A

With spectacle lenses which refract light rays so that they do focus on the retina.

102
Q

What do new technologies to treat eye defects include?

A

-Hard and soft contact lenses

-Laser surgery

-Replacement lenses

103
Q

Hyperopia

A

-Occurs either when the lens is the wrong shape and doesn’t refract the light enough, or if the eyeball is too short

-Images of nearby objects are brought into focus behind the retina

104
Q

How can hyperopia be treated?

A

By placing a convex lens (bends outwards each side) in front of the eye.

This is a converging lens which refracts light rays inwards before they enter the eye.

This allows the lens to focus them onto the retina to form a clear image.

105
Q

How can myopia be treated?

A

By placing a concave lens (bends inwards each side) in front of the eye.

This is a diverging lens which refracts light rays outwards before they enter the eye.

This allows the lens to focus them onto the retina to form a clear image.

106
Q

Myopia

A

-Occurs either when the lens is the wrong shape and refracts the light too much, or if the eyeball is too long

-Images of distant objects are brought into focus in front of the retina.

107
Q

Contact lenses

A

Tin lenses that sit on the surface of the eye.

They are shaped to compensate for the fault in focusing.

108
Q

Why are contact lenses popular?

A

They are lightweight and almost invisible.

They are more convenient than glasses for sporting activities

109
Q

Soft vs hard contact lenses

A

Soft lenses are generally more comfortable, but carry a higher risk of eye infections than hard lenses.

110
Q

What happens in laser eye surgery?

A

A laser is used to vaporise tissue, changing the shape of the cornea (and so changing how strongly it refracts light into the eye).

The surgeon can precisely control how much tissue the laser takes off, completely correcting the vision.

111
Q

What does slimming an eye’s lens down in laser surgery do?

A

Make the lens less powerful, which can improve short sightedness.

112
Q

What does changing the shape of an eye’s lens to make it more powerful do?

A

Improve long sightedness.

113
Q

What are the risks of laser surgery?

A

Complications such as eye infection, or the eye reacting in a way that makes your vision worse than before.

114
Q

What happens in replacement lens surgery?

A

The natural lens of the eye is removed and an artificial lens made of clear plastic is inserted in its place.

115
Q

Why does replacement lens surgery carry higher risks than laser eye surgery?

A

It involves work inside the eye.

The retina could be damaged, leading to a potential loss of sight.

116
Q

What is the optimum temperature for enzyme action in the human body?

A

37°C

117
Q

What is core body temperature?

A

The temperature inside your body, where your internal organs are.

118
Q

How is body temperature monitored and controlled?

A

By the thermoregulatory centre in the brain.

119
Q

What does the thermoregulatory centre contain?

A

Receptors sensitive to the temperature of the blood flowing through the brain.

120
Q

Where do the nervous impulses received by the thermoregulatory centre come from?

A

Temperature receptors in the skin.

They give information about skin temperature.

121
Q

Briefly describe what happens if body temperature becomes too high.

A

If the body temperature is too high, blood vessels dilate (vasodilation) and sweat is produced from the sweat glands.

Both of these mechanisms cause a transfer of energy from the skin to the environment.

122
Q

Briefly describe what happens if body temperature becomes too low.

A

If the body temperature is too low, blood vessels constrict (vasoconstriction), sweating stops and skeletal muscles contract (shiver).

123
Q

Reflex action for a too high temperature.

A

Temperature receptors detect that core body temperature is too high.

The thermoregulatory centre acts as a coordination centre - it receives information from the temperature receptors and triggers the effectors automatically.

Effectors e.g. sweat glands, produce a response and counteract the change.

124
Q

Reflex action for a too high temperature.

A

Temperature receptors detect that core body temperature is too low.

The thermoregulatory centre acts as a coordination centre - it receives information from the temperature receptors and triggers the effectors automatically.

Effectors e.g. muscles, produce a response and counteract the change.

125
Q

What does it mean to say that some effectors work antagonistically? (thermoregulatory system)

A

One effector heats and another cools at the same time, to achieve a very precise temperature.

This mechanism allows a more sensitive response.

126
Q

Sweat

A

-Produced by sweat glands

-Evaporates from skin

-This transfers energy to the environment

127
Q

Vasodilation

A

-The blood vessels supplying the skin dilate

-More blood flows close to the surface of the skin (in the skin capillaries)

-This helps transfer energy from the skin to the environment

128
Q

Why do hairs stand on end when we are cold?

A

-To minimise heat loss

-We contract erector muscles in the skin, which raises our hairs.

-This traps a layer of insulating air and so means that less heat energy is lost.

129
Q

Vasoconstriction

A

-Blood vessels supplying skin capillaries constrict to close off the skin’s blood supply

130
Q

How does shivering warm up the body?

A

-Shivering is the automatic contraction of your skeletal muscles.

-This contraction requires energy from respiration which transfers some energy as waste to warm the body.

131
Q

What type of feedback is involved in thermoregulation?

A

Negative feedback

132
Q

Where are the two main places that temperature receptors are found?

A

-Skin

-Blood vessels

Biology (18 decks)

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