5.2 Nervous system (Triple)

Question 1

What is the function of the nervous system?

Answer 1

The nervous system allows the body to react to its surroundings and coordinate an appropriate response

Question 2

How does a stimulus lead to a response being carried out in the body?

Answer 2

1. Stimulus is converted into an electrical impulse by the receptors
2. The electrical impulse passes along sensory neurones to the central nervous system
3. The central nervous system coordinates an appropriate response and an electrical impulse is sent along motor neurones to the effector, which carries out a response

Question 3

What sequence of events describes how the nervous system works?

Answer 3

Stimulus → Receptor → Coordinator → Effector → Response

Question 4

What is a reflex action?

Answer 4

A reflex action is an automatic and rapid response which does not involve any conscious input from the brain

Question 5

Why are reflex actions important?

Answer 5

Reflex actions aid survival by preventing harm to the body

Question 6

Describe how a reflex action occurs via a reflex arc

Answer 6

1. The stimulus is detected by a receptor
2. An electrical impulse passes along a sensory neurone to the spinal cord (part of the CNS)
3. At a synapse, between a sensory neurone and a relay neurone, a chemical diffuses across the gap and stimulates a new impulse which passes along the relay neurone
4. The same process occurs at a synapse between a relay neurone and a motor neurone
5. At the effector, an appropriate response is carried out

Question 7

What is the difference between a reflex pathway and a conscious pathway?

Answer 7

Within a reflex pathway, the coordination centre is a relay neurone found in the spinal cord/unconscious parts of the brain.

In a conscious pathway, the coordination pathway is in a conscious part of the brain.

Question 8

What is the function of the cerebral cortex? (Triple)

Answer 8

Controls consciousness, intelligence, memory, and language

Question 9

What is the function of the cerebellum? (Triple)

Answer 9

Controls muscular coordination

Question 10

What is the function of the medulla oblongata? (Triple)

Answer 10

Controls unconscious activities e.g. breathing, heart rate

Question 11

Why is the investigation and treatment of the brain difficult? (Triple, Higher)

Answer 11

The brain is a complex and delicate organ which is easily damaged and destroyed.

Certain membranes prevent drugs from reaching the brain. The exact function of each part of the brain is unknown.

Question 12

What methods are used by scientists to determine brain function? (Triple, Higher)

Answer 12

● Studying patients with brain damage

● Electrical simulation of the
brain

● MRI scans

Question 13

What stimuli are the receptors of the eye sensitive to? (Triple)

Answer 13

Light intensity and colour

Question 14

What are the two main functions of structures found within the eye? (Triple)

Answer 14

● Focusing on near or distant objects - accommodation

● Adaption to dim light

Question 15

Describe the structure and function of the retina. (Triple)

Answer 15

The retina is a light sensitive layer found at the back of the eye. Light stimulates the retinal cells, resulting in impulses being sent to the brain.

Question 16

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

Answer 16

The optic nerve connects the eye and the brain. It carries impulses to the brain so that an image can be visualised

Question 17

Describe the structure and function of the sclera. (Triple)

Answer 17

The sclera is the tough outer layer of the eye which protects its internal structures

Question 18

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

Answer 18

The cornea is the curved transparent layer at the front of the eye. It lets light into the eye and allows light to be focused onto the retina.

Question 19

Describe the strong structure and function of the iris. (Triple)

Answer 19

The iris is a muscle which controls the size of the pupil by contracting or relaxing. This allows the eye to adjust to bright and dim lighting.

Question 20

Describe the structure and function of the ciliary muscles and suspensory ligaments. (Triple)

Answer 20

The ciliary muscles and suspensory ligaments hold the lens in place and control its shape

Question 21

Describe how the iris alters the size of the people in both bright and dim light. (Triple)

Answer 21

In bright light, the circular muscles contract and radial muscles relax which makes the pupil smaller to avoid retinal damage.

In dim light, the circular muscles relax and radial muscles contract which makes the pupil larger so more light can enter the eye.

Question 22

What is accommodation? (Triple)

Answer 22

Accommodation is the alteration of the lens’ shape in order to focus on near or distant objects.

Question 23

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

Answer 23

1. Ciliary muscles contract
2. Suspensory ligaments loosen
3. Lens becomes thicker and more curved - light rays are refracted strongly.

Question 24

How does the eye focus on a distant object? (Triple)

Answer 24

1. Ciliary muscles relax
2. Suspensory ligaments tighten
3. Lens becomes thinner -light rays are refracted weakly

Question 25

What is myopia? (Triple)

Answer 25

Myopia (short-sightedness) usually occurs when the lens of the eye is too curved. As a result, light is focused in front of the retina so images appear blurry.

Question 26

How can myopia be treated? (Triple)

Answer 26

Myopia can be treated using glasses with a concave lens, which spreads out light rays so they can be focused on the retina.

Question 27

What is hyperopia? (Triple)

Answer 27

Hyperopia (long-sightedness) usually occurs when the lens of the eye is too flat. As a result, light is focused behind the retina so images appear out of focus.

Question 28

How can hyperopia be treated? (Triple)

Answer 28

Hyperopia can be treated using glasses with a convex lens, which brings the light rays together so they can be focused on the retina.

Question 29

What are the two types of contact lenses? (Triple)

Answer 29

Contact lenses are lenses that are placed on the eye. There are two types: ● Hard: rigid material, lasts for a long time, must be kept sterile ● Soft: flexible material, lasts for a shorter time, more comfortable

Question 30

What is laser eye surgery? (Triple)

Answer 30

Laser eye surgery is the use of lasers to fix visual defects in adults. To treat myopia, lasers reduce the thickness of the cornea so light is refracted less strongly. To treat hyperopia, lasers alter the curvature of the cornea so that light is refracted correctly.

Question 31

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

Answer 31

A replacement lens can be either implanted into the eye (along with the natural lens) or it may replace the natural lens altogether.

Question 32

What are the risks of lens replacement? (Triple)

Answer 32

Risks of lens replacement include retinal damage, cataracts and infections.

Question 33

Where is body temperature controlled in the body?

Answer 33

Body temperature is controlled by the thermoregulatory centre in the hypothalamus which is located in the brain

Question 34

How is temperature monitored by the body?

Answer 34

The thermoregulatory centre has receptors that are sensitive to blood temperature. The skin has receptors that are sensitive to skin temperature - sends impulses to the thermoregulatory centre

Question 35

What physiological changes occur when the body temperature is too high? (Triple)

Answer 35

Vasodilation: blood vessels near the surface of the skin dilate so more heat is radiated away Sweating: evaporation of water takes away heat energy from the surface of the skin

Question 36

What physiological changes occur when the body temperature is too low? (Triple)

Answer 36

Vasoconstriction: blood vessels near the surface of the skin constrict so less heat is radiated away Shivering: respiration allows muscles to contract. It's an exothermic process, so heat energy is released Sweating stops