2. Homeostasis Pt6

Question 1

What forms can contraceptives come in?

Answer 1

-pills
-implant
-patch
(Hormonal or non-hormonal)

Question 2

How do oral contraceptives work?

Answer 2

• they prevent women from becoming pregnant
• most contained oestrogen &/or progesterone as they inhibit FSH production and so stop an egg from maturing in the ovaries
• they also thicken cervical mucus to prevent stern from getting through
• some side effects include: high blood pressure & headaches, some new pills contain only progesterone

Question 3

What are barrier methods and give 2 examples?

Answer 3

• barrier methods prevent the sperm from reaching the egg

- condoms and diaphragms

Question 4

How do condoms work?

Answer 4

• they cover the penis to collect semen (unless they’re damaged)
• they also protect against sexually transmitted infections

Question 5

How do diaphragms work?

Answer 5

• they cover the cervix to stop sperm (must be positioned correctly)
• they work best with a chemical spermicide to kill sperm
• they don’t prevent STIs

Question 6

How do intrauterine devices work?

Answer 6

• IUDs (aka the coil) are inserted into the uterus by a doctor to prevent embryos from implanting o
• some also release progesterone
• they usually last for 3-5 years, but may cause infections or period problems

Question 7

What’s a surgical contraception?

Answer 7

• in men a vasectomy is where the sperm ducts are cut and tied to prevent any sperm getting into the semen
• in women the oviducts can be cut and tied to prevent eggs reaching the uterus or sperm reaching the egg
• requires general anaesthetic

Question 8

What’s abstinence of sex?

Answer 8

• abstaining from sex around ovulation when the eggs is in the oviduct may prevent pregnancy but is very unreliable
• hormone levels can be tested to indicate when ovulation occurs to improve its effectiveness

Question 9

What’s an easy way to get pregnant if you can’t conceive?

Answer 9

• Use fertility drugs

- some women can’t conceive because they don’t produce enough of the right hormones

Question 10

How do fertility drugs work?

Answer 10

• artificially FSH can be taken to stimulate the eggs in the ovary and trigger oestrogen production
• or LH

Question 11

Other than the fertility pill what other way can you get pregnant?

Answer 11

• in vitro fertilisation (IVF)
• fertilisation usually occurs in the oviducts (Fallopian tubes) which carry the egg from the ovaries to the uterus
• if these are damaged then eggs canning reach the uterus and the woman can’t get pregnant

Question 12

Explain how in vitro fertilisation (IVF) is carried out?

Answer 12

1. The women is first treated with FSH and LH to stimulate the maturity of several eggs at once
2. The eggs are collected and placed in a Petri dish
3. Sperm from the father is mixed in with the eggs to fertilise them
4. embryos start to develop and are checked to ensure they’re healthy
5. When they’re small balls of cells 1 or 2 embryos are inserted into the woman’s uterus

Question 13

What releases adrenaline?

Answer 13

Adrenal glands

Located on top of each kidney

Question 14

When is adrenaline produced?

Answer 14

• it’s released into during stressful, scary or exciting times
• it triggers a fight or flight response
• it boosts the oxygen and glucose supply to the brain and muscles to increase respiration to prepare the body for intense activity

Question 15

What are the responses to adrenaline?

Answer 15

1. Increased heart rate and breathing rate
2. Glycogen in the liver is converted to glucose for respiration
3. Mental awareness increases
4. Blood is diverted from your digestive system to your muscles
5. Pupils dilate to let in more light

Question 16

Is the release of adrenaline a negative feedback?

Answer 16

No

Question 17

Where and how is thyroxine produced?

Answer 17

• it’s produced by the thyroid gland (in your neck)

- using small amounts if iodine from your diet (and amino acids)

Question 18

What does thyroxine control?

Answer 18

the basal metabolic rate of the body (the speed at which chemical reactions in the body take place) such as:
-the rate of respiration, using oxygen to break down substances such as sugars
-the growth and development of a child’s brain
Adults are relatively stable

Question 19

Explain how thyroxine is controlled by a negative feedback loop?

Answer 19

• if the blood thyroxine levels fall, the brain detects the drop and signals the pituitary gland to release Thyroid stimulating hormone (TSH)
• this stimulates the thyroid gland to release more thyroxine
• if blood thyroxine levels rise, the brain signals the pituitary gland to stop releasing TSH

Question 20

Why is it important that you control your body temperature?

Answer 20

• it’s important your core body temperature remains at 37 C

- so enzymes work at their optimum rate

Question 21

What detects a change in your body temperature?

Answer 21

• your thermoregulatory centre in your hypothalamus contains receptors to detect changes to the temperature of the blood flow
• temperature receptors in the skin also detect changes in the external temperature and send information to the thermoregulatory centre
• these changes trigger negative feedback mechanism
• some responses are behavioural eg. Standing in the shade

Question 22

What does your body do when it’s too cold?

Answer 22

1. blood vessels (small arteries) supplying the skin constrict, reducing blood flow to the capillaries near the surface
   - called vasoconstriction, it reduces heat loss by radiation
2. sweat production decreases, reducing heat loss by evaporation
3. skeletal muscles rapidly contract and relax producing shivering. This generates more heat energy from increased respiration (exothermic reaction)

Question 23

What does your body do when it’s too hot?

Answer 23

(Hypothalamus receptor detect increase in temperature)
1. Vasodilation dilate the blood vessels to the skin, allowing more blood to flow to capillaries at the surface, increases heat loss by radiation
2. Sweat production increases, which increases heat loss by evaporation
Both causing energy transfer from the skin to the environment

Question 24

Why would sweating help in humid weather?

Answer 24

-because humid slows evaporation, making it difficult to remain cool (the sweat isn’t evaporating)

Question 25

What auxin?

Answer 25

-a plant hormone that allows plants to selectively grow parts of the plant to move in certain directions

Question 26

What’s gravitotropism?

Answer 26

-it’s a response to gravity
-it ensures that shoots grow up and roots grow down
(Irrelevant to light)

Question 27

What’s phototropism?

Answer 27

• it’s the response to light

- it ensures the the stem bends towards the light to maximise the absorption of light by the leaves for photosynthesis

Question 28

How can you use auxin?

Answer 28

1. rooting powders: it encourages the stem to develop roots to grow a new plant from a cutting
2. weed killers: it encourages uncontrolled growth in broad leaved plants (weeds) which kills them
   - some can selectively kill weeds but not other plants (eg. Crops)
   - this reduces competition for water, light and nutrients increasing crop yield
3. Promoting growth in tissue culture

Question 29

How can you use gibberellins?

Answer 29

(It causes the stem to make a flower instead of a leaf)

• promoting flowing: throughout the year for florists
• increasing fruit size: or triggering fruit development
• end seed dormancy

Question 30

How can you use ethene with plants?

Answer 30

• it’s used in the food industry to control ripening of fruit during storage and transport
• then ripened to the perfect stage ready for sale