B1.2 Responses To A Changing Environment

Question 1

What is homeostasis?

Answer 1

Keeping a constant internal environment.

Question 2

What is thermoregulation?

Answer 2

Maintaining a constant internal body temperature.

Question 3

What is osmoregulation?

Answer 3

The maintenance of water content in the body.

Question 4

What part of the brain monitors body heat?

Answer 4

The hypothalamus.

Question 5

What methods does the body use to cool you down?

Answer 5

Sweating
Relaxing the erector muscle so that body hair lies flat.
Making blood flow through blood vessels closer to the surface.

Question 6

What methods does your body use to warm you up?

Answer 6

Moving your muscles

Making your blood flow through deeper blood vessels.

Question 7

What is vasoconstriction?

Answer 7

When the body narrows the blood vessels closest to the surface.

Question 8

What is vasodilation?

Answer 8

When the body narrows the blood vessels furthest from the surface.

Question 9

What is negative feedback?

Answer 9

When one thing happens, it is made to go the opposite way eg thermoregulation.

Question 10

What is a stimulus?

Answer 10

Something that the body can detect?

Question 11

What detects a stimulus?

Answer 11

Receptor cells.

Question 12

What is an electrical impulse?

Answer 12

An electrical signal sends messages around the body.

Question 13

What is a hormone?

Answer 13

Chemical messengers which travel in the blood to activate target cells.

Question 14

What features does a neurone have to help the electrical impulse travel quickly?

Answer 14

It is very long- the impulse travels fastest in a neurone

It has a myelin sheath- this is a fatty insulator that speeds it up.

Question 15

What is a synapse?

Answer 15

A gap between two neurones. They impulse releases a chemical which diffuses across the gap to set off a new electrical impulse.

Question 16

What are the differences between hormones and nerves?

Answer 16

Hormones: 
Slow message 
Act for a long time
Act in a general way
Chemical message

Impulses:
Very fast message
Act for a very short time
Act on a very precise area
Electrical message.

Question 17

What are dendrons?

Answer 17

Branched endings of neurones so that they can connect to lots of other neurones.

Question 18

What are the five receptor organs and what receptors do they contain?

Answer 18

Eyes- contains light receptors
Ears- sound and balance receptors
Nose- smell receptors- sensitive to chemical stimuli
Tongue- taste receptors
Skin- pressure and temperature change receptors.ŵ

Question 19

What are sensory neurones?

Answer 19

Long dendrons and short axons that carry impulses from the receptor cells to the CNS.

Question 20

What are relay neurones?

Answer 20

They carry nerve impulses from the sensory neurones to the motor neurone. They are short dendrons and axons.

Question 21

What are motor neurones?

Answer 21

They are many short dendrons and one long axon that carry nerve impulses from the CNS to the effectors.

Question 22

What are effectors?

Answer 22

Things that carry out the effect eg muscles or glands.

Question 23

How does the CNS coordinate a response, from start to finish?

Answer 23

1. A stimulus is detected by receptors, and the information is sent as an impulse along a sensory neurone to the CNS.
2. The CNS coordinates the response (decides what to do about it and tells something what to do).
3. The CNS sends information to an effectors along a motor neurone.
   The effector acts accordingly.

Question 24

What is a reflex?

Answer 24

An automatic response to certain stimuli that help reduce the chances of injury.

Question 25

How does a reflex arc work, from start to finish?

Answer 25

1. Stimulus is detected by receptor cells. The information is passed along a sensory neurone as an impulse. 2. A relay neurone relays it to the motor neurone which takes it to the effector.

Question 26

Why are reflexes quicker than normal responses?

Answer 26

They do not go through the CNS so the brain doesn't think about it as the thinking takes time.

Question 27

How are glucose, glycogen and glucagon all linked to blood glucose levels?

Answer 27

When blood glucose levels are too high, the pancreas secretes insulin, which causes the liver to turn glucose into glycogen. When blood glucose levels are too low, the pancreas secretes glucagon, which causes the liver to turn glycogen into glucose.

Question 28

What is type 1 diabetes and how is it treated?

Answer 28

Type 1 diabetes is caused by the pancreas not secreting enough insulin. Treatments include: Limiting the intake of foods rich in simple carbohydrates Insulin therapy where insulin is injected.

Question 29

What is type 2 diabetes and how is it treated?

Answer 29

It is cause by the body becoming resistant to insulin and where the body doesn't respond. Treatments include: Eating a healthy diet Getting regular excersise Losing weight (if needed)

Question 30

What is a tropism?

Answer 30

A plants response to stimuli eg light, gravity or moisture.

Question 31

What is phototropism?

Answer 31

The growth of a plant is response to light. Shoots are positively phototropic- they grow towards light.

Question 32

What is gravitropism (or geotropism)?

Answer 32

The growth of a plant in response to gravity. Roots are positively gravitropic- they grow downwards.

Question 33

What is auxin?

Answer 33

A plant hormone that controls growth at the tips of shoots and roots.

Question 34

How does auxin promote growth in the shoot of a plant?

Answer 34

When a shoot tip is exposed to light, more auxin accumulates on the shady side. This makes the cells elongate faster on the shady side, so the shoot bends towards the light.

Question 35

How does auxin promote geotropic growth in a root?

Answer 35

When a root is growing sideways, gravity produces an unequal distribution of auxin. The auxin inhibits growth so the cells on top elongate faster, so the root bends downwards.

Question 36

What is gibberellin?

Answer 36

A plant growth hormone that stimulates seed germination, stem growth and flowering.

Question 37

What are the commercial uses of plant hormones?

Answer 37

Selective weedkillers Growing from cuttings Controlling the ripening of fruit Producing seedless fruit

Question 38

How are plant growth hormones used as selective weedkillers?

Answer 38

Only broad leaved plants are affected by the weedkiller (like weeds). The weedkiller disrupts their normal growth patterns, which kills them.

Question 39

How is rooting powder used to grow plants from cuttings?

Answer 39

Rooting powder contains a plant growth hormone which makes it produce roots rapidly.

Question 40

How are hormones used in controlling the ripening of fruit?

Answer 40

Ripening hormone is added to picked fruit, making it ripe once it reaches the supermarket.

Question 41

How is seedless fruit produced?

Answer 41

If plant growth hormones are added to fruit, the fruit grows whilst seeds don't.