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Biology Paper 2 > B10 The Human Nervous System > Flashcards

B10 The Human Nervous System Flashcards

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1
Q

What is 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 is homeostasis important?

A

Homeostasis is important for maintaining optimal conditions for enzyme action and all cell functions.

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3
Q

What does homeostasis in the body include (Give examples of homeostasis in action)?

A
  • Control of blood glucose concentration
  • Control of body temperature
  • Control of water levels
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4
Q

Compare receptors, coordination centres, and effectors.

A

Receptors - cells that detect changes in the internal or external environment. These changes are known as stimuli. Receptors may be part of the nervous or hormonal control systems of the body.
Coordination centres - areas that receive and process the information from the receptors. They send out signals and coordinate the response of the body. They include the brain, which acts as a coordination centre for both the nervous system and parts of the hormonal system, the spinal cord, and some organs such as the pancreas.
Effectors - muscles or glands that bring about responses to the stimulus that has been received. These responses restore conditions in the body to the optimum levels

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5
Q

Show how the nervous system works in a flow diagram

A

Stimulus –> Receptor –> Coordinator (CNS) –> Effector –> Response

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6
Q

Describe the main function of the nervous system.

A

Enables humans to react to their surroundings and to coordinate their behaviour

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7
Q

Describe the difference between a sensory neurone and a motor neurone.

A

A sensory neurone carries impulses from sense organs to the central nervous system (CNS). Whereas, a motor neurone carries information from CNS to body’s effector organs (muscles and glands)

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8
Q

Describe how receptors enable you to respond to changes in your surroundings.

A
  • Cells called receptors detect stimuli (changes in the environment).
  • Impulses from receptors pass along sensory neurones to the central nervous system.
  • The CNS coordinates the response of effectors, by sending impulses along motor neurones which arrive at an effector organ, which may be muscles contracting or glands secreting hormones
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9
Q

How do the effectors respond to the arrival of impulses?

A

Muscles - respond to the arrival of impulses by contracting
Glands - respond to the arrival of impulses by releasing (secreting) chemical substances

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10
Q

What are the main stages of a reflex arc?

A

Stimulus –> Receptor –> Sensory neurone –> Relay neurone –> Motor neurone –> Effector –> Response

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11
Q

Why are reflexes important?

A
  • They help you to avoid danger or harm
  • Lots of reflexes take care of basic bodily functions e.g. breathing, moving food through your digestive system
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12
Q

How do reflexes work?

A
  • An electrical impulse passes from the receptor along the sensory neurone to the spinal cord
  • It then passes along a relay neurone in the spinal cord and straight back along the motor neurone.
  • The motor neurone carries nerve impulses to the effector organ
  • The effector organ will be a muscle or gland.
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13
Q

Describe what the main areas of the brain do.

A
  • The cerebral cortex is concerned with consciousness, intelligence, memory, and language.
  • The cerebellum is concerned mainly with coordinating muscle activity and balance.
  • The medulla is concerned with unconscious activities, such as controlling the heartbeat, the movements of the gut, and breathing.
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14
Q

What are receptors?

A

Cells that detect changes in the internal or external environment. These changes are known as stimuli. Receptors may be part of the nervous or hormonal control systems of the body.

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15
Q

What are coordination centres?

A

Areas that receive and process the information from the receptors. They send out signals and coordinate the response of the body. They include the brain, which acts as a coordination centre for both the nervous system and parts of the hormonal system, the spinal cord, and some organs such as the pancreas.

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16
Q

What are effectors?

A

Muscles or glands that bring about responses to the stimulus that has been received. These responses restore conditions in the body to the optimum levels

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17
Q

Sclera

A

Tough, white, protective outer layer of the eye

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18
Q

Cornea

A

The transparent frontal part of the eye that refracts light

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19
Q

Iris

A

Controls the diameter of the pupil and therefore how much light enters the eye.

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20
Q

Lens

A
  • Refracts light
  • Can change it’s shape to control how strongly it refracts light
  • Focuses the light onto the retina
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21
Q

How are neurones adapted to their function?

A

Long axon - allows impulses to be carried long distances
Lots of dendrites - gives connections to many other cells
Myelin sheath - insulates electrical impulses to keep the signal strong
Lots of mitochondria - releases energy required for transmission across synapses

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22
Q

Differences between the nervous and hormonal system

A

Nervous system - triggers a rapid response, short lasting, carries electrical impulses, signals transmitted through neurones
Hormonal system - triggers a slower response, longer lasting, chemical messengers, signals transmitted through the blood

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23
Q

Explain what happens in your nervous system when you see a piece of fruit, pick it up and eat it.

A
  • Light from fruit detected by sensory receptors in eyes
  • Impulse travels along sensory neurone to brain
  • Information processed in brain
  • Impulse sent along motor neurone to muscles of arm and hand
  • So you pick up fruit and put it in mouth
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24
Q

Voluntary vs Reflex responses

A

Voluntary
- requires conscious thought
- takes time

Reflex
- automatic
- fast
- protect the body from harm

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25
Q

What is the name given to chemicals that diffuse across a synapse?

A

Neurotransmitters

26
Q

Synapses

A
  • The gap between two neurones
  • Rely on diffusion of neurotransmitters
  • Therefore much slower than electrical impulses
  • Reflex only has 2 synapses, synapses between the sensory and relay neurones, and between the relay and motor neurones
  • Therefore it is very fast
27
Q

Relay neurones

A
  • Found inside the CNS
  • Connects motor and sensory neurones
28
Q

What happens when you step on a pin?

A
  • Pain/pressure receptors in foot detect the stimulus
  • Electrical impulse sent along sensory neurone
  • When it reaches the synapse, neurotransmitters released and diffuse across synapse to relay neurone
  • Triggers the relay neurone to start an electrical impulse which is carried along to the next synapse
  • Again neurotransmitters would be released and diffuse across the synapse to motor neurone
  • Motor neurone carries electrical impulse to an effector, the muscles in the leg
  • Muscles in leg contract, moving the foot away from the pin, giving the response
29
Q

Optic nerve

A

Transmits visual information, in the form of electrical impulses, from the retina to the brain

30
Q

Ciliary muscles

A

Controls the thickness of the lens to allow focusing

31
Q

Suspensory ligaments

A

Attach the ciliary muscles to the lens

32
Q

Pupil

A

The gap through which light passes to reach the lens

33
Q

Retina

A

Full of receptor cells, which are sensitive to both the brightness (light intensity) and the colour of light

34
Q

Why are images upside down on the retina?

A

As light is refracted by the cornea and the lens, light entering the top part of the eye is refracted to the bottom part of the retina whereas light entering the bottom of the eye is refracted to the top part of the retina.

35
Q

Why is the blink reflex important?

A

Protects the eye from damage

36
Q

Describe how a light ray that enters the eye from a nearby object is focussed and translated into a visual image in the brain

A
  • Light enters through the cornea, cornea always refracts the same amount of light
  • Ciliary muscles contract
  • Suspensory ligaments relax
  • Lens is thick so refracts more light
  • Light is focussed on the retina
  • Image is upside down
  • Receptor cells in the retina detect the light
  • Impulses sent along sensory neurones in the optic nerve to the brain
  • Brain interprets the visual image
37
Q

Myopia

A
  • Short sightedness
  • Can see near objects in focus but not distant objects
  • Light is focussed in front of the retina
  • Can be due to lens that is too curved or a long eyeball
  • Treatment: glasses/contact lenses with concave lens
38
Q

Hyperopia

A
  • Long sightedness
  • Can focus on distant objects but not near objects
  • Lens cannot refract light enough. Light is focussed behind the retina
  • Can be due to a lens that is too flat or a short eyeball
  • Treatment: glasses/contact lenses with convex lens
39
Q

What is a contact lens?

A

Small lenses that are placed directly onto the surface of the cornea

40
Q

Cerebral cortex

A

Concerned with consciousness, intelligence, memory and language

41
Q

Cerebellum

A

Concerned mainly with coordinating muscle activity and balance

42
Q

Medulla

A

Concerned with unconscious activities, such as controlling the heartbeat, breathing, and the movements of the gut

43
Q

Define a reflex action

A

An unconscious response that allows a person to respond to a dangerous situation automatically and rapidly via a reflex arc.

44
Q

Rod cells

A

Only detect black and white, but function in lower light intensities

45
Q

Cone cells

A

Detect colour, but require high light intensities

46
Q

Define accommodation

A

Process of changing the shape of the lens to focus on near or distant objects

47
Q

Describe the changes of the eye when focusing on a distant object

A
  • Ciliary muscles relax
  • Suspensory ligaments are pulled tight
  • Lens pulled ‘flat’ and thin
  • Only refracts light slightly
48
Q

Describe the changes of the eye when focusing on a nearby object

A
  • Ciliary muscles contract
  • Suspensory ligaments loosen
  • Lens more rounded and thick
  • Refract light strongly
49
Q

Studying patients with brain damage

A

If a small part of the brain has been damaged, the effect this has on the patient can tell us a lot about what the damaged part of the brain does.

49
Q

Electrical stimulation

A
  • The brain can be stimulated electrically by pushing a tiny electrode into the tissue and producing a small zap of electricity
  • By observing what stimulating different parts of the brain does, its possible to get an idea of what those parts do
50
Q

MRI Scans

A
  • A magnetic resonance imaging (MRI) scanner is a large, tube-like machine that can produce a very detailed picture of the brain’s structures.
  • Scientists use it to find out what areas of the brain are active when people are performing different actions
51
Q

Eye - bright light

A
  • Circular muscles contract
  • Radial muscles relax
  • Pupil constricts
  • Allows less light through
52
Q

Eye - dim light

A
  • Circular muscles relax
  • Radial muscles contract
  • Pupil dilates
  • Allows more light through
53
Q

Function of receptors

A

Detect stimuli

54
Q

Function of coordination centres

A

Receive and process the information from receptors

55
Q

Examples of coordination centres

A
  • Brain
  • Spinal cord
  • Pancreas
56
Q

Function of effectors

A

Bring about responses which restore optimum levels

57
Q

What are the two types of effectors?

A

Muscles and glands

58
Q

What are the three main reasons 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 it is hard to access
  • It is very complicated, so hard to target with medications
59
Q

Which two muscles make up the iris?

A

Circular and radial muscles

Biology Paper 2 (10 decks)

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