Topic 2 - Cells and Control

Question 1

Explain how the difficulties of accessing brain tissue inside the skull can be overcome by a using CT scan (1/2)

Answer 1

CT SCANNER
• uses X-rays to produce a 3D brain image
• CT scan shows main structures in brain (not functions)
• shows a diseased/damaged brain structure, e.g. patient lost vision
• NOT recommended for children/pregnant women because it exposes patient to higher doses of radiation.

Question 2

Explain how the difficulties of accessing brain tissue inside the skull can be overcome by using a PET scanner to investigate brain function (2/2)

Answer 2

PET SCANNER measures activity of the brain
• a radioactive tracer is injected into patients blood before the scan
• this is used to investigate structure + function of the brain
• useful for identifying cancerous tumours

Question 3

Describe why a brain tumour is difficult to treat

Answer 3

• risk of damaging the brain
• nerves don’t repair themselves
• skull protects your brain so it makes it harder to get through

Question 4

Explain the structure & function of the eye as a sensory receptor including the role of:
a) the cornea and lens
b) the iris
c) rod and cone cells in the retina

Answer 4

a) Cornea - Structure —> curved, transparent front section of the eye. Function —> refracts (bends) light into the eye & focuses light onto retina.
Lens - focuses light onto the retina.

b) Iris - made up of muscles that can control the size of your pupil. + it controls how much light enters pupil .

c) Retina - Structure —> layer of tissue at the back of the eye that contains light receptor cells (rods & cones).
Rod cells are sensitive in dim light & they can’t sense colour.
Cone cells detects colour & it is sensitive to different colours.

Optic nerve - carries electrical impulses from receptors to the brain.

Question 5

Describe defects of the eye including cataracts, long-sightedness, short-sightedness and colour blindness

Answer 5

CATARACTS occurs when there is:
• a cloudy patch on lens. This stops light from entering the eye normally
• blurred vision

LONG-SIGHTEDNESS occurs when:
• lens is wrong shape & it doesn’t bend enough light / eyeball is short
• light from near objects focuses behind retina

SHORT-SIGHTEDNESS occurs when:
• lens is wrong shape because it bends too much light / eyeball is long
• light from distant objects focuses in front of retina

COLOUR-BLINDNESS occurs when:
• red or green cones in retina aren’t working properly

Question 6

Explain how cataracts, long-sightedness, short-sightedness can be corrected (fixed)

Answer 6

CATARACTS
• replace lens with an artificial one

LONG-SIGHTEDNESS
• wear glasses / contact lenses with a convex lens

SHORT-SIGHTEDNESS
• wear glasses / contact lenses with a concave lens

COLOUR BLINDNESS
• no cure for this because cone cells can’t be replaced

Question 7

Describe the structures & functions of the brain including the cerebrum, cerebellum, cerebral hemispheres and medulla oblongata

Answer 7

Cerebrum - largest section of the brain. Divided into two halves called cerebral hemispheres. Right side controls muscles on the left side of the body.
Functions: movement, intelligence, memory, language, vision.

Cerebellum - a large “lump-like” structure found at the bottom of the brain.
Functions: responsible for muscle coordination & balance.

Medulla oblongata - a small, elongated structure found in the brainstem.
Functions: controls unconscious activities such as breathing, heart rate, blood pressure, facial movements & vomiting.