Coordination And Response

Question 1

Function of the iris

Answer 1

Controls the diameter of the pupil and therefor how much light enters the eye

Question 2

Function of the lens

Answer 2

Focuses the light on the retina

Question 3

What is the retina

Answer 3

The light sensitive part of the eye. It is covered in rod and cones which are light receptors

Question 4

What are differences of rods and cones

Answer 4

Roads are more sensitive in dim light but can’t see colour

Comes are sensitive to colours but aren’t so good in dim light

Question 5

Function of the optic nerve

Answer 5

Carries impulses from the receptors to the brain

Question 6

What is the role of the cornea

Answer 6

Refracts light into eye

Transparent has no blood vessels to supply it with oxygen so oxygen diffuses in from the outer surface

Question 7

Explain how the iris reflex works for adjusting to bright light

Answer 7

Bright light triggers a reflex that makes the pupil smaller, allowing less light in
Radial muscles relax, circular muscles contract

Question 8

How does accommodation of the eye work

Answer 8

Looking at distance objects:
Ciliary muscles relax
Suspensory ligaments tort
This makes lens thin 
Nearby objects:
Opposite

Question 9

Why when your older do people often need to wear glasses

Answer 9

As you get older your eyes lens loses flexibility so it can’t easily spring back to a round shape. This means light can’t be focused well for near viewing so older people often have to use reading glasses

Question 10

Define the term hormone

Answer 10

Hormones are chemicals directly real eased into the blood, carried in the plasma. Hormones control things km leg and and cells that need constant adjustment

Question 11

Where is insulin made and what is it s role in the body

Answer 11

Pancreas

Helps control blood sugar level by stimulating the liver to turn glucose into glycogen for storage

Question 12

List three differences between nervous and hormonal responses

Answer 12

Nerves have a v fast message whereas hormones is slower

Nerves act for a short time whereas hormones act for a long time

Nerves act on a very precise area whereas hormones act in a more general way

Question 13

Define homeostasis

Answer 13

Homeostasis invokes balancing body functions to maintain a constant internal environment

Question 14

How is body temperature reduced when you’re too hot

Answer 14

Sweating - transfers heat from you to the environment
Vasodialation - Blood vessels close to the surface of the skin widen to allow more heat into the surroundings
Hairs - lie flat

Question 15

What does your body do when it is it too cold

Answer 15

Very little sweat produces
Vasoconstriction - blood vessels near the surfaces constricted so that less heat can be transferred to surroundings
Shiver - generates heat in muscles
Hairs stand in ends - act as an insulating layer is air which keeps you warm

Question 16

Do larger animals tend to have small or large surface area to volume ratios

Answer 16

Smaller organisms have bigger surface area to volume ratios. This means they can lose body heat easily but also means they’re very vulnerable in cold environments

Question 17

Give two ways plants respond to stimuli

Answer 17

Phototropism

Geotropism

Question 18

What are auxins

Answer 18

Auxins are plant hormones which control growth at the tips of shoots and roots. They move through the plant in solution

Question 19

What is positive phototropism

Answer 19

When shoots are positively phototropism they grow toward the light

1) when shoot tip is exposed to light to accumulate more auxins on the side in the shade.
2) this makes the cells grow (elongate) faster on the shaded side, so the shoot bends towards the light

Question 20

What is positive geotropism

Answer 20

When roots are positively geotropism they grow towards gravity

1) a root growing sideways will also have more auxins on its lower side
2) but in a root the extra auxin inhibits growth. This means the cells non top elongate faster, and the root bends downwards

Question 21

How are auxins responsible for shoots being negatively geotropism

Answer 21

Shoots are negatively geotropism as they grow away from gravity

1) when a shoot is growing sideways, Gravity produces an unequal distribution of auxin in the tip, with more auxin on the lower side
2) this causes the lower side to grow fast bending the shoot upwards