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Biology > THE HUMAN NERVOUS SYSTEM > Flashcards

THE HUMAN NERVOUS SYSTEM Flashcards

1
Q

What is homeostasis?

A

The regulation of the internal conditions of the cells to maintain optimum conditions for functioning, in response to internal and external changes.

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2
Q

What internal conditions are controlled by homeostasis?

A

Body temperature
The water content of the body
Blood glucose concentration.

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3
Q

How does the body detect and respond to changes in the body?

A

Automatic control systems, including nervous responses in your nervous system and chemical responses in your hormone system.

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4
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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5
Q

What are coordination centres?

A

Areas that receive and process the the information from receptors. They send out signals and coordinate the response from 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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6
Q

What are effectors?

A

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

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7
Q

What are sense organs?

A

Eyes and skin are examples.

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8
Q

How does the nervous system works?

A

When a sensory detector detects a stimulus, the information is sent as an electrical impulse that passes along the neurones. These are usually found in bundles of hundreds or thousands of neurones known as nerves.
The impulse travels along the neurone until it reaches the central nervous system. The CNS is made up of the brain and spinal cord.
The cells that carry impulses from your sense organ to your CNS are called sensory neurones.

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9
Q

What are motor neurones?

A

The brain coordinates a response to the information and the motor neurones carry information from the CNS to the rest of your body.

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10
Q

Why are the effectors?

A

They respond to the signals. They may be muscles or glands.

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11
Q

What does the receptor do?

A

Sends an impulse along a sensory neurone, carrying information about a change in the environment to the coordinator (CNS). Once all the incoming information has been processed, the coordinator sends impulses down motor neurones. These motor impulses stimulate the effectors to bring about the response needed in an particular situation.

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12
Q

What are reflexes?

A

Automatic responses. They are rapid and don’t involve the conscious part of your brain.

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13
Q

What are reflexes for?

A

Avoiding danger or harm because they happen so fast.

Take care of your bodies basic functions such as breathing.

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14
Q

How do simple reflex actions work?

A

Involve three types of neurone
Sensory
Motor
Relay -

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15
Q

What are relay neurones?

A

These connect a sensory neurone and a motor neurone, and are found in the CNS.

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16
Q

Explain the pathway of the reflex arc.

A

An electrical impulse passes from the receptor along the sensory neurone to the CNS. It then passes along a relay neurone (usually in the spinal cord) and straight back along the motor neurone. From there, the impulse arrives at the effectors organ. The effector organ will be a muscle or a gland. This pathway is called the reflex arc.

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17
Q

What are synapses?

A

These are junctions between the neurones which form physical gaps between the neurones. The electrical impulses travelling along your neurones have to cross these synapses.

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18
Q

What happens when you touch an object? REFLEX ARC

A

A receptor in your skin is stimulated. An electrical impulse from a receptor passes along a sensory neurone to the CNS. In case the spinal cord.

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19
Q

What happens when an impulse from the sensory neurone arrives at the synapse with a relay neurone? REFLEX ARC

A

A chemical is released. The chemical diffuses across the synapse to the relay neurone where it sets off a new electrical impulse travelling down the motor neurone to the effector.

20
Q

What happens when the impulse reaches the effector organ? REFLEX ARC

A

It is stimulated to respond.

21
Q

What is the coordinator in a reflex action?

A

Relay neurone either in the spinal cord or the unconscious areas of the brain.

An impulse also traveled up the spinal cord to the conscious areas of you brain. You know about the reflex action, but only after it has happened.

22
Q

What is the cerebral cortex?

A

Concerned with consciousness, intelligence, memory and language.

23
Q

What is the cerebellum?

A

Mainly concerned with coordinating muscular activity and balance.

24
Q

What is the medulla?

A

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

25
Q

How can scientists electrically stimulate parts of the brain?

A

If scientists expose the brain by removing the top of the skull, they can stimulate different areas and see what effect this has. As there are no sensory nerve endings in the brain, brain sergers is usually done on conscious patients. People can experience hunger, fear, anger or thirst simply because relevant areas of their brain have been stimulated.

26
Q

How can MRI scans be used on the brain?

A

Taking images of the brain in living people. A magnetic resonance imaging (MRI) scan will show exactly which area of the brain is affected by eg a stroke.
This enables scientists to link loss of a certain function such as speech or control of movement on one side of the body, with damage to a particular region of the body.

The most recent MRI scanners can take images as someone carries out a simple task.

27
Q

Why is it difficult to investigate the brain?

A

Many different neurones in different areas.

Range of different chemicals released in the synapses in the brain.

28
Q

What is the eye?

A

A sense organ containing many receptors that are sensitive to light.

29
Q

Where are the light sensitive cells found in the eye?

A

Arranged together inside the back of the eye in a special light sensitive layer known as the retina.

30
Q

What is the sclera?

A

White outer layer of the eye. Relatively strong so the eyeball is not easy to damage.

31
Q

What is the cornea?

A

Transparent area at the front of the eyeball. This lets light into the eye. The curved surface of the cornea is important for changing the direction of the light rays coming into the eye, making sure that as they enter the eye they are focussed on the retina.

32
Q

What is the iris?

A

Muscular and it controls the size of the pupil. It is a hole through which light enters the eye.
It is made of muscles that contract and relax to change the size of the pupil and do control the amount of light reaching the retina.

33
Q

What happens to the iris in dim light?

A

Enlarged the pupil so as much light as possible can be let in.

CIRCULAR MUSCLES RELAX
RADIAL MUSCLES CONTRACT
PUPIL DILATES.

34
Q

What happens to the iris in bright light?

A

The iris makes the pupil very small. The prevents too much light from damaging the delicate, light sensitive cells.

CIRCULAR MUSCLES CONTRACT
RADIAL MUSCLES RELAX
PUPIL CONSTRICTS

35
Q

What is the lens?

A

Once through the pupil, might passes through a clear disc - the lens. It ‘fine tunes’ the focussing of the light rays, changing their direction to produce a clear image on the retina.

36
Q

What holds the lens in place?

A

Suspensory ligaments and the ciliary muscles.

37
Q

How is the image sent to the brain from the eye?

A

When light hits the retina, the light-sensitive cells are stimulated. They send impulses to the brain along sensory neurones in the optic nerve. When the brain receives these messages it interprets them as a visual image.

38
Q

How does the eye focus the light?

A

The light gets focussed by the process of refraction, where light changes direction as it passes through the eye.

The cornea and the jelly in the eyeball change the direction of the light rays onto the retina, but they also refract it the same amount.

The shape of the lens can be changed by contraction or relaxation of the ciliary muscles. This changes the amount the lens refracts the light.

39
Q

What happens to they eye when focussing on distant objects?

A 
Lens less convex (flatter)
Ciliary muscles relax
Suspensory ligaments pulled tight
lens 'flat' and relatively thin
Only refracts light slightly so they are focussed on the retina. This is because the light that reaches your eyes from distant objects is travelling in almost parallel rays.
40
Q

What happens to they eye when focussing on a nearby object?

A 
Lens more convex (rounded)
Ciliary muscles contract
Suspensory ligaments slack. 
Lens more rounded and relatively thick.
The lens is thicker and curved so it refracts light rays more strongly so that they are focussed on the retina.
41
Q

What is accommodation?

A

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

42
Q

What is myopia?

A

Short sightedness

You can see close objects in clear focus, but distant objects look blurred.
This is because the light is focussed in front of the retina.
May be due to a lens that is too curved or a long eyeball.

43
Q

How is myopia treated?

A

Wear glasses with a concave lens that spread out the light from distant object before it reaches the eye. This means that the thicker lens can bring it into perfect focus on the retina.

44
Q

What is hyperopia?

A

Long sightedness

You can focus clearly on distant objects but close objects appear blurred. This may be dur to a lens that is too flat and thin, or due to a particularly short eyeball.
As a result the lens cannot refract the rays strongly enough and the light is focussed behind the retina.

45
Q

How is hyperopia corrected?

A

Convex lens. They bring the rays together more before they reach the eye itself. So, the rays are brought into perfect focus.

46
Q

What is laser eye surgery?

A

Used to treat myopia by reducing the thickness of the cornea so it refracts less strongly. This means that the lens now focusses distant light on the retina instead of in front of it.

To treat hyperopia lasers are used to change the curve of the cornea so it refracts light from close objects more effectively.

Can only be done on adults whose eyes have become stable.

47
Q

What are replacement lenses?

A

Add another lens inside the eye to correct the visual defect permanently.
Two techniques;
the permanent contact lens is implanted into the eye and the natural lens left in place.
Or, the faulty lens is replaced by an artificial lens.

Risks - damage to the retina, cataracts developing if the natural lens remains in place, and infections.

Biology (47 decks)

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