B1 Topic 2 Responding To Change

Question 1

What is osmoregulation?

Answer 1

Osmoregulation is the regulation of water content.

Question 2

What is thermoregulation?

Answer 2

It is regulating body temperature.

Question 3

How does blood glucose regulation need to be kept?

Answer 3

It needs to be regulated at a steady level.

Question 4

What is negative feedback?

Answer 4

Negative feedback is a mechanism that keeps osmoregulation, thermoregulation and blood glucose levels steady.

Question 5

What does negative feedback do?

Answer 5

Changes in the environment trigger a response that counteracts the changes. This means the internal environment stays around a norm so the cells work at their best. This only works within certain limits.

Question 6

What is homeostasis?

Answer 6

Homeostasis is maintaining a stable internal environment.

Question 7

What happens to the skin when the body is too hot?

Answer 7

The nerve endings detect this. In the dermis: Sweat glands secrete sweat onto the surface of the skin, this evaporates lowering body temperature. Sebaceous gland excretions emulsify sweat preventing it being lost as droplets. Hairs on the skin lay flat and erector muscles relax to increase heat loss. Blood vessels dilate increasing the flow of blood to the surface of the skin where heat can be lost to the air.

Question 8

What happens to the skin when the body is too cold?

Answer 8

Erector muscles contract, hairs stand on end trapping air that acts as insulation. Blood vessels constrict, reducing the flow of blood to the surface hence reducing heat loss.

Question 9

What is the role of the hypothalamus?

Answer 9

This monitors the temperature of the blood, sending signals to the blood vessels in the dermis in response. Therefore, regulating blood temperature.

Question 10

What is vasodilation?

Answer 10

Vasodilation results in a widening of the blood vessels, this increases blood flow and heat loss

Question 11

What is vasoconstriction?

Answer 11

Vasoconstriction narrows the blood vessel, reducing blood flow / heat loss.

Question 12

Why is negative feedback needed in terms of thermoregulation?

Answer 12

Negative Feedback is needed to prevent temperature change from
running away and to keep the body at an optimum 37°C.

Question 13

What is the role of the endocrine glands?

Answer 13

Endocrine glands produce hormones which can be transported by the blood to their target organs.

Question 14

What happens in the body when blood glucose levels are too high?

Answer 14

Insulin is secreted from the pancreas. This insulin goes to the liver which converts the excess glucose to glycogen. Blood glucose levels have been reduced and insulin stops being secreted.

Question 15

What happens to the body when blood glucose levels are too low?

Answer 15

Glucagon is secreted from the pancreas. The glucagon makes the liver turn glycogen into glucose. Glucose is added by the liver to the blood and glucose levels increase. Glucagon stops being secreted.

Question 16

What causes type 1 diabetes and how is it controlled?

Answer 16

Type 1 diabetes is caused by a lack of insulin. It can be controlled by injections of insulin and, because the body cannot lower blood sugar levels, both diet and exercise.

Question 17

What causes type 2 diabetes and how is it controlled?

Answer 17

Type 2 diabetes occurs when the body becomes resistant to insulin. Can be controlled by exercise and diet. Strong links to obesity.

Question 18

What is phototropism?

Answer 18

The growth of a plant in response to light. Shoots are positively phototrophic - they grow towards the light.

Question 19

How does phototropism occur?

Answer 19

In light, auxin is concentrated on the shaded side of the stem. Auxin causes cell elongation so the stem will grow towards the light.

Question 20

What is gravitropism?

Answer 20

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

Question 21

How does gravitropism occur?

Answer 21

Gravitropism is caused by the plant hormone auxin. Auxin slows the growth of cells in the root and stimulates growth in stems. As a result stems grow up and roots grow down.

Question 22

How is seedless fruit produced?

Answer 22

Auxin applied to unpollinated plants will produce seedless fruit.

Question 23

How do selective weed killers work?

Answer 23

Kill some plants but not others. Growth hormones are absorbed by specific plants, this causes the plants to grow too rapidly and then die. Useful for removing dandylions from lawns or thistles from wheat crops.

Question 24

What is the role of rooting powder?

Answer 24

Rooting powders contain growth hormones that make stems quickly develop roots.

Question 25

How is fruit ripening controlled? Why is it useful?

Answer 25

Hormones can be used to speed up or slow down fruit ripening. This can be useful if fruit has a long way to travel or will be on display for some time.

Question 26

What does the C.N.S consist of?

Answer 26

The brain and spinal chord, linked to sense organs by nerves.

Question 27

What is the role of the dendron?

Answer 27

To collect electrical signals.

Question 28

What is the role of the myelin sheath?

Answer 28

Signals pass down the dendrons and axons which are protected and insulated by a myelin sheath. It speeds up the impulse and stops it getting lost.

Question 29

What is the role of the axon?

Answer 29

Axons pass the electrical signals onto other dendrites

Question 30

What do receptors do in the C.N.S?

Answer 30

Receptors are specialised cells, usually in the sense organs, that detect changes in the environment. Stimuli such as touch, pressure, pain, chemicals, temperature or sound are turned into electrical impulses which pass along neurones to the CNS and the brain.

Question 31

What is the role of the relay neurone?

Answer 31

It’s within the CNS and passes on electrical impulses generated by the stimuli.

Question 32

What is the role of the motor neurone?

Answer 32

To transmit signals from the CNS to muscles elsewhere in the body.

Question 33

What is the role of the sensory neurone?

Answer 33

To transmit impulses inwards from sensors.

Question 34

How does the reflex arc work?

Answer 34

When a stimulus is detected by receptors an impulse travels along the sensory neurone. The message is passed along the relay neurone which is in the spine.This then travels to the motor neurone which takes the message to a muscle (effector). The muscle contracts, moving it to avoid injury.

Question 35

How do neurones transmit information around the body?

Answer 35

Neurones transmit information as electrical impulses around the body. Neurones have branched endings called dendrons that connect with lots of others. This impulse is passed along the axon and protected by the myelin sheath. As neurones are long it speeds up the impulse. The connection between two neurones is the synapse. The impulse is transmitted by neurotransmitters which diffuse it across the gap.

Question 36

Characteristics of nerves?

Answer 36

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

Question 37

Characteristics of hormones?

Answer 37

Slower message
Act for a long time
Act in a more general way
Chemical message.

Question 38

What is the role of auxin?

Answer 38

It stimulates plants to grow (in the tips, shoots and roots). Auxin is produced in the tips and diffuses backwards to stimulate the cells just behind the tips to elongate. If the tip is removed it stops growing. It promotes the growth in the shoots but high concentrations inhibit growth in the root.

Question 39

What is gibberellin?

Answer 39

Stimulates plant stems to grow. It stimulates seed germination, stem growth and flowering. It stimulates the stems of the plants to grow by stem elongation. This helps them to grow tall. Gibberellin and auxin can work together to make plants grow very tall.