B10- The Human Nervous System

Question 1

3 things that happen to your eyes in dim light

Answer 1

• Circular muscles relax
• Radial muscles contract
• Pupil dilates

Question 2

Describe the nervous system arc in the 3 steps

Answer 2

1) Impulses from receptors pass along sensory neurone to CNS.
2) The brain coordinates the response
3) Impulses are sent along motor neurones from the brain to effector organs

Question 3

Explain how light from an object forms an image on the retina

Answer 3

• Light rays enter the eye through the cornea
• They are bent and refracted
• They travel through the pupil and lens
• They refract further in order to meet on the retina and form an upside down image.

Question 4

Explain why it is difficult to study the brain

Answer 4

The brain is inside the skull and is very delicate and easily damaged.

Question 5

Explain why it is difficult to treat brain disorders

Answer 5

• The brain is very complex so it is difficult to investigate the effect of drugs.
• Drugs are not always able to pass through the membranes which surround the brain.
• It is easy to cause damage during surgery.

Question 6

How else can common eye defects be cured?

Answer 6

1) Hard or soft contact lenses- placed on the surface of the eye , must be kept sterile to prevent eye infection. Some are disposable
2) Laser eye surgery- in myopia it’s used to reduce the thickness of the cornea so it refracts light less strongly. In hyperopia lasers change the curve of the cornea so it refracts light from nearby objects more effectively.
3) Lens replacement- Either a permanent contact lens is inserted with the natural lens in place or an artificial lens replaces the natural one. Risks include possible damage to retina, cataracts in the natural lens, or infections.

Question 7

List the nervous system arc

Answer 7

Stimulus - Receptor - Sensory Neurone - CNS - Motor Neurone - Effector - Response

Question 8

Name the 2 effectors in the human body

Answer 8

Muscles and glands

Question 9

Name 5 different stimuli

Answer 9

Sound, chemicals, temperature changes, touch, pain

Question 10

Name the 3 internal conditions that are controlled in homeostasis

Answer 10

Water content, Body temperature, Blood glucose concentration

Question 11

Name the nerve that contains neurones to and from the eye to the brain

Answer 11

Optic nerve

Question 12

Read out the reflex arc in order

Answer 12

Stimulus - Receptor - Sensory Neurone - CNS - Relay Neurone - Motor Neurone - Effector - Response

Question 13

What are the 3 main parts of the brain?

Answer 13

Cerebral Cortex, Cerebellum, Medulla

Question 14

What are the 3 things that occur to your eyes in bright light?

Answer 14

• Circular muscles contract
• Radial muscles relax
• Pupils constricts

Question 15

What are the two states of the pupil?

Answer 15

• In dim light the pupil is enlarged to let in as much light as possible
• In bright light the iris makes the pupil small to reduce the amount of light entering the eye as too much light could damage the receptor cells in the retina.

Question 16

What do all control systems include and what are their features?

Answer 16

1) Receptors- which detect stimuli (changes in the internal or external environment). They may be apart of the nervous or hormonal control system
2) Coordination centres- CNS, which includes the brain, spinal cord, and organs such as the pancreas.
3) Effectors- muscles or glands that bring about a response to the stimulus.

Question 17

What do receptor cells do?

Answer 17

They detect stimuli (changes in the environment)

Question 18

What do reflex actions do?

Answer 18

They control bodily functions such as breathing and digestion and they also help you to avoid danger.

Question 19

What does homeostasis rely on?

Answer 19

Automatic control systems such as your nervous system, hormones, and body organs.

Question 20

What does the nervous system use to enable you to react quickly to your surroundings?

Answer 20

Electrical Impulses

Question 21

What happens to the eye when you focus on a distant object?

Answer 21

• The ciliary muscles relax
• The suspensory ligaments are pulled tight
• The lens is pulled thin so it only refracts the light rays slightly

Question 22

What happens to the eye when you focus on close objects?

Answer 22

• The ciliary muscles contract
• The suspensory ligaments loosen
• The lens becomes thicker so it can refract light rays strongly

Question 23

What happens when an impulse arrives at a junction between 2 neurones?

Answer 23

When an impulse arrives at a junction between 2 neurones, chemicals are released that cross the synapse and arrive at receptor sites at the next neurone. This starts up a new electrical impulse in the next neurone.

Question 24

What is a reflex action?

Answer 24

A rapid and automatic response to stimuli to avoid danger that does not require the conscious part of the brain

Question 25

What is accommodation?

Answer 25

Accommodation is the process of changing the shape of the lens of the eye to focus on near or distant objects

Question 26

What is between 2 neurones?

Answer 26

At the junction between 2 neurones is a gap called a synapse. Chemicals transmit the impulse across the gap.

Question 27

What is homeostasis?

Answer 27

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

Question 28

What is hyperopia and how can it be cured?

Answer 28

Long sightedness - Affects the ability to see nearby objects, occurs when the light rays surpass the retina and can be cured by using a simple convex lens

Question 29

What is MRI and why is it useful?

Answer 29

MRI (magnetic resonance imaging) is useful for diagnosing brain disorders as unlike surgery it can be done without removing part of the skull, so there is no risk of damaging the brain.

Question 30

What is myopia and how can it be cured?

Answer 30

Short sightedness - Where light rays are just short of the retina which causes distant objects to appear blurred, can be cured by using a simple concave lens

Question 31

What are the parts of the eye and their functions?

Answer 31

Sclera- Tough white outer layer that prevents damage to the eye.
Cornea- The transparent area at front of sclera. It lets light into the eye and the curved surface changes the direction of light rays so they are refracted towards the retina
Iris- Muscles of the iris contract and relax to control the size of the PUPIL (the whole through which light enters the eye)
Lens- Clear disc that is held in place by suspensory ligaments and ciliary muscles. The lens changes direction of light so the image is focused on the retina.
Retina- When light hits retina, the light-sensitive cells are stimulated and send impulses to the brain along sensory neurones in the optic nerve to form an image.

Question 32

What is the cerebellum concerned with?

Answer 32

The cerebellum is concerned mainly with muscular activity

Question 33

What is the cerebral cortex concerned with?

Answer 33

The cerebral cortex is concerned with consciousness, intelligence, memory and language

Question 34

What is the medulla concerned with?

Answer 34

The medulla is concerned with unconscious activities such as breathing and controlling the heartbeat.

Question 35

Which part of the brain regulates body temperature?

Answer 35

Hypothalamus regulates body temperature

Question 36

Why is it important to maintain optimal conditions in a cell or organism?

Answer 36

So enzyme actions and cell functions can be carried out.