5.2 The human nervous system

Question 1

What is the function of the nervous system?

Answer 1

Enable humans to react to their surroundings and coordinate their behaviour.

Question 2

Describe how a stimulus leads to a body response? (2)

Answer 2

1. Information from receptors passes along [sensory] neurones as electrical impulses to the central nervous system (CNS)
2. The CNS coordinates the effector’s response [by sending electrical impulses along motor neurones] (may be muscle contracting or glands secreting hormones).

Question 3

What is the CNS? (2)

Answer 3

The brain and spinal cord.

Question 4

What is the sequence to show how the nervous system works? (5)

Answer 4

Stimulus -> receptor -> coordinator -> effector -> response

Question 5

What is a reflex action? (1)

Answer 5

An automatic and rapid response which does not involve the conscious part of the brain.

Question 6

Describe how the reflex arc works. (4)

Answer 6

1. Stimulus detected by receptors which passes information along sensory neurones to the spinal cord.
2. Synapse between sensory and relay neurone, in spine, stimulates new impulse which passes along relay neurone.
3. The same process occurs at the synapse between the relay and motor neurone.
4. Motor neurone sends electrical impulses to an effector causing a response to occur.

Question 7

Why are reflect actions important? (1)

Answer 7

Aid survival by preventing harm to body.

Question 8

What is the difference between a reflex pathway and a conscious pathway? (1)

Answer 8

• A reflex pathway uses relay neurones which are located in the spinal cord/unconscious part of brain.
• A conscious pathway has coordination centres located in the conscious part of the brain.

Question 9

What is the brain? (1)

Answer 9

An organ with different regions for specific functions, made up of billions of interconnected neurones.

Question 10

What does the brain do? (1)

Answer 10

Control complex behaviour

Question 11

What is the function of the cerebral cortex?

Answer 11

Large top - to control consciousness, intelligence, language and memory.

Question 12

What is the function of the cerebellum? (1)

Answer 12

Smaller ball - to control muscular coordination.

Question 13

What is the function of the medulla? (1)

Answer 13

Tube - to control unconscious activities (e.g. breathing, heart rate)

Question 14

Why is the function and investigation of the brain difficult? (4)

Answer 14

• Complex and delicate organ.
• Easily damaged and destroyed.
• Some membranes do not let drugs go to the brain.
• Exact function of each part of brain still not known.

Question 15

What is a neuroscientist?

Answer 15

Scientists who map and study the brain.

Question 16

What methods are used by neuroscientists to determine brain function? (3)

Answer 16

• MRI scans.
• Studying patients with brain damage.
• Electrical stimulation of the brain.

Question 17

What is the eye? (1)

Answer 17

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

Question 18

What are the main functions of the structures in the eye?

Answer 18

• Adaptation to dim light
• Accommodation - focussing on near and distant objects

Question 19

Describe the structure and function of the retina? (2)

Answer 19

Light-sensitive layer found at back of eye.

• Cells stimulated by light resulting in impulses being sent to brain.

Question 20

Describe the structure and function of the optic nerve. (2)

Answer 20

Nerve connecting eye and brain.

• Carries impulses to brain so image can be visualised.

Question 21

Describe structure and function of sclera. (1)

Answer 21

Tough outer layer of eye which protects internal structure.

Question 22

Describe the structure and function of the cornea. (2)

Answer 22

Curved transparent layer at front of eye.

• Allows light to pass through/into eye and be focussed onto the retina.

Question 23

Describe the structure and function of the iris. (2)

Answer 23

Muscle which controls size of pupil by contracting and relaxing.

• Enables eye adjustment to bright and dim lighting

Question 24

What is the structure and function of the ciliary muscles and the suspensory ligaments.

Answer 24

Holds the lens in place and controls its shape.

Question 25

Describe how the eye adapts in both types of lighting. (2)

Answer 25

- Bright: circular muscle contracts, radial muscle relaxes - smaller pupil to avoid retinal damage. - Dim: circular muscle relaxes, radial muscle contracts - larger pupil to let more light enter.

Question 26

What is accommodation? (1)

Answer 26

The alteration of the lens’ shape to focus on near or distant objects.

Question 27

How does the eye focus on a nearby object? (3)

Answer 27

- Ciliary muscle contracts - Suspensory ligaments relax - Lens becomes thicker - light rays refracted strongly

Question 28

How does the eye focus on distant objects? (3)

Answer 28

- Ciliary muscle relaxes - Suspensory ligaments contract - Lens pulled thinner - light rays refracted weakly.

Question 29

What is myopia?

Answer 29

Short-sightedness - lens too curved so light is focussed in-front of retina making images blurry.

Question 30

How can myopia treated?

Answer 30

Spectactles with concave lenses - spread out light rays to be focussed onto retina.

Question 31

What is hyperopia?

Answer 31

Long-sightedness - lens too flat so light focussed behind retina making images appear out of focus.

Question 32

How can hyperopia be treated?

Answer 32

Spectacles with convex lenses - brings light rays closer together to be focussed onto retina.

Question 33

What are contact lenses? (1)

Answer 33

Lenses that are placed on eye.

Question 34

What are the two types of contact lenses?

Answer 34

- Hard lenses: rigid material, last longer time, must be sterilised - Soft lenses: flexible material, lasts for shorter time, more comfortable

Question 35

What is laser eye surgery? (1)

Answer 35

Using lasers to fix visual defects.

Question 36

How is laser eye surgery used to fix short sightedness? (1)

Answer 36

Myopia: reduce thickness of cornea so light refracted less strongly.

Question 37

How is laser eye surgery used to fix long sightedness? (1)

Answer 37

Hyperopia: reduced curvature of cornea so light refracted correctly.

Question 38

How can replacement lenses be used to treat visual defects? (2)

Answer 38

- Lenses implanted on top of natural lenses. - Lenses completely replace natural lenses.

Question 39

What are the risk of lens replacement? (3)

Answer 39

- Cataracts - Retinal damage - Infections

Question 40

What are examples of new eye technologies? (3)

Answer 40

- Hard and soft contact lenses - Laser eye surgery - Lens replacement

Question 41

What monitors and controls body temperature? (1)

Answer 41

The thermoregulatory part of the hypothalamus.

Question 42

How is body temperature regulated? (2)

Answer 42

- Skin has receptors sensitive to skin temperature - sends electrical impulses to thermoregulatory centre. - Thermoregulatory centre consists of receptors sensitive to blood temperature.

Question 43

What physiological changes occurs when your body temperature gets too hot? (2)

Answer 43

- Vasodilation: blood vessels near skin surface dilate - more thermal energy radiated away. - Sweating: more water on surface of skin evaporates to transfer thermal energy away.

Question 44

What physiological changes occur when your body temperature gets too low? (3)

Answer 44

- Vasoconstriction: blood vessels near skin surface constrict - less heat energy radiated. - Shivering: muscles enabled to contract due to respiration - heat lost. - Sweating stops.