B10: The human nervous system

Question 1

What is homeostasis?

Answer 1

The regulation of the internal conditions of a cell/ organism to maintain optimum conditions for function in response to internal and external changes

Question 2

What is an automatic control system?

Answer 2

A nervous responses from the nervous system or chemical responses from the endocrine system

Question 3

What is the pathway of an automatic control system when it detects a change in the environment?

Answer 3

The change (stimulus) is picked up by the receptor cells, which pass it to a coordination centre (like the brain, spinal chord or pancreas), which processes and receives the information, before passing it to an effector (a muscle which contracts or a gland which secretes hormones) which carries out the response

Question 4

Describe the pathway taken by electrical impulses when detecting a stimulus

Answer 4

Electrical impulse picked up by a receptor, then sent down a sensory neurone, to the CNS. At the end, there’s a junction called a synapse where a chemical is released and it diffuses across a relay neurone to the CNS where an electrical impulse is triggered in the motor neurone which passes down the impulse to the effector.

Question 5

RP: Describe how to measure reaction time

Answer 5

One person holds a ruler above another person’s thumb (level with the 0 mark). They then drop the ruler, and the other person has to catch the ruler as quickly as they can. Then, record, the measurement that is level with the top of their thumb. Repeat several times and calculate a mean

Question 6

RP: Independent, Dependent and Control variables

Answer 6

IV: The person whose reaction time is being tested
DV: The measurement of reaction time
CV: Starting distance between thumb and ruler, measure from top of thumb, conditions in the room (noise/ lighting)

Question 7

RP: What other independent variables can be investigated in the experiment?

Answer 7

The effect of practise on reaction time
The hand catching the ruler
The effect on certain chemicals on reaction time

Question 8

What are 3 parts of the brain and what are their functions?

Answer 8

Cerebral cortex - memory, language, consciousness
Cerebellum - movement coordination, balance
Medulla - body temp/ breathing rate maintainence

Question 9

Why is it hard to treat brain damage/ diseases?

Answer 9

Brain surrounded by thick skull - hard to access
Complex structures - we don’t exactly know which parts perform which functions
Brain is delicate and easy to damage

Question 10

How can we study the brain?

Answer 10

Look at patients with brain damage, look at their behaviour and narrow down that part of the brain to its function
Electrically stimulate different parts of the brain, and see changes in behaviour
MRI scans, look at which parts of the brain are most active during certain activities

Question 11

How does the eye focus on near objects?

Answer 11

Ciliary muscle contracts, suspensory ligaments relax, lens is now more curved and thicker

Question 12

What causes short sightedness?

Answer 12

Long eyeball, light focused in front of the retina
Lens is too thick

Question 13

What is accommodation?

Answer 13

Changing the shape of the lens to focus on near or distant objects

Question 14

How does the eye focus on distant objects?

Answer 14

Ciliary muscles relax, suspensory ligaments contract, lens is now thinner and less curved

Question 15

What causes long sightedness?

Answer 15

Short eyeball, light focuses behind the retina
Less elastic lens, cannot bend to focus on near objects

Question 16

How can hyperopia be treated?

Answer 16

Convex lens - focus the light before it enters the eye

Question 17

How can myopia be treated?

Answer 17

Concave lens - partially un focus light before it enters the eye

Question 18

Where is the retina found and what is its function?

Answer 18

Layer of light sensitive cells found at the back of the eye. When light hits it, it stimulates the cells, and sends an impulse to the brain, which interprets the information to form an image.

Question 19

Where is the optic nerve found and what is its function?

Answer 19

Nerve that leaves the eye and goes to the brain. Carries impulses from the retina and to the brain.

Question 20

Where is the sclera found and what is its function?

Answer 20

White outer layer which supports the structures inside the eye - strong to prevent damage.

Question 21

Where is the cornea found and what is its function?

Answer 21

See through layer in front of the eye.
Allows light through and the curved surface bends the light so it focuses on the retina.

Question 22

Where is the iris found and what is its function?

Answer 22

Muscles surrounding the pupil.
Contract and relax to change the size of the pupil.

Question 23

What is the function of the ciliary muscles and suspensory ligaments?

Answer 23

Hold lens in place and control its shape.

Question 24

What are some treatments for eye defects?

Answer 24

Spectacle lenses
Contact lenses
Laser eye surgery - either reduce the thickness of the cornea (myopia) or change its shape (hyperopia).
Replacement lens - risks include retinal damage or risks of cataracts.