Homeostasis and Response

Question 1

what is homeostasis all about?

Answer 1

keeping internal conditions as constant as possible

Question 2

what does homeostasis consist of?

Answer 2

automatic control systems

Question 3

what are the three features of an automatic control system?

Answer 3

1. receptors
2. co-ordination centres
3. effectors

Question 4

what do receptors do?

Answer 4

• detect a change in the environment
• the ‘environment’ could either be the body’s internal conditions or the external conditions

Question 5

what do co-ordination centres do?

Answer 5

• receive and process the information from the receptors

Question 6

what do effectors do? (2)

Answer 6

• carries out the response to the change in environment
• restores optimum levels

Question 7

what is the key role of the nervous system?

Answer 7

enables humans to react to their surroundings and co-ordinate their behaviour

Question 8

what happens when you touch a hot object? (7)

Answer 8

• the stimulus is detected by a receptor
• electrical impulses pass from the receptor along the sensory neurone to the CNS
• at the end of the sensory neurone, there’s a synapse
• at the synapse, a chemical is release which diffuses across to a relay neurone in the CNS where it triggers an electrical impulse
• the electrical impulse passes across the relay neurone
• again, a chemical is released, triggering an electrical impulse in a motor neurone
• the electrical impulse now passes down the motor neurone to the effector, which responds to the change

Question 9

what does the endocrine system do?

Answer 9

controls the body by chemicals called hormones

Question 10

what does the endocrine system consist of?

Answer 10

a number of glands that secrete hormones directly into the bloodstream

Question 11

what are the five specific target organs that the hormones act on?

Answer 11

1. Pituitary Gland
2. Thyroid Gland
3. Pancreas
4. Adrenal Glands
5. Ovaries and Testes

Question 12

Pituitary Gland (3)

Answer 12

- located in the brain
- also known as the ‘MASTER GLAND’

• releases a number of different hormones into the blood depending on the conditions
• pituitary hormones act on other glands and they cause other hormones to be released
• because of this, the pituitary glands can have a range of different effects on the body

Question 13

Thyroid Gland (1)

Answer 13

• releases hormones to do with growth and how rapidly the body’s reactions take place

Question 14

Pancreas (1)

Answer 14

• releases hormones (insulin) to help control the concentration of glucose in the blood

Question 15

Adrenal Glands (1)

Answer 15

• release the hormone adrenaline which is produced during times of fear or stress

Question 16

Ovaries and Testes (1)

Answer 16

• release hormones involved with puberty and reproduction

Question 17

what does insulin do when there is a high concentration of glucose in the blood? (3)

Answer 17

• travels around the body through the blood stream
• triggers the body cells to take up glucose from the blood
• also triggers the liver and muscle cells to store excess glucose as a storage molecule called glycogen

Question 18

define diabetes

Answer 18

where a person’s blood glucose control does not work effectively

Question 19

Type 1 Diabetes (2)

Answer 19

• the pancreas does not produce enough insulin and therefore the body can not return its optimum
• people with type 1 diabetes inject themselves with insulin if their blood glucose levels raise too much

Question 20

Type 2 Diabetes (2)

Answer 20

• the body cells stop responding to the insulin that the pancreas is producing
• people with type 2 diabetes often have a diet containing a controlled level of carbohydrates

Question 21

what happens when the glucose concentration is too low? (3)

Answer 21

• the pancreas releases glucagon into the bloodstream
• glucagon triggers the liver and muscle cells to convert their glycogen stores back into glucose
• this glucose is released into the blood, restoring the normal level of blood glucose concentration

Question 22

which hormone do the testes produce?

Answer 22

testosterone

Question 23

what is the role of testosterone?

Answer 23

stimulates the testes to produce sperm

Question 24

which hormone do the ovaries produce?

Answer 24

oestrogen

Question 25

state the role of the **follicle stimulating hormone (FSH)**

Answer 25

causes an egg to mature in an ovary

Question 26

state the role of the **luteinising hormone (LH)**

Answer 26

causes an egg to be released from an ovary or causes ovulation

Question 27

state the role of **oestrogen** and **progesterone**

Answer 27

maintain the uterus lining in case the egg for that month has been fertilised and needs to implant

Question 28

what are the *four* types of contraception?

Answer 28

1. Oral Contraceptives 2. Hormonal Contraceptives 3. Barrier Method 4. Sterilisation

Question 29

an example of an oral contraceptive...

Answer 29

the pill

Question 30

what does *the pill* do?

Answer 30

- contains hormones that stop FSH from being produced, which prevents an egg from being matured in an ovary

Question 31

advantages (1) and disadvantages (1) of the pill?

Answer 31

ADVANTAGES - highly effective if taken correctly DISADVANTAGES - must be taken every day; if the woman forgets to take it then there's a risk of pregnancy

Question 32

examples of hormonal contraception... (3)

Answer 32

- implant - injection - patch

Question 33

what do the hormonal forms of contraception all do?

Answer 33

- all contain progesterone, which prevents FSH and LH from being released and in turn prevents an egg from both being matured and being released

Question 34

advantages (1) and disadvantages (1) of hormonal contraception?

Answer 34

ADVANTAGES - more convenient than taking a daily pill; implant lasts three years; the injection lasts thirteen weeks; the patch lasts around a week DISADVANTAGES - none of these protect against sexually transmitted diseases

Question 35

examples of the barrier method include... (2)

Answer 35

- condom - diaphragm

Question 36

what do all the forms of the barrier method do?

Answer 36

prevent the sperm from reaching the egg

Question 37

advantages (2) and disadvantages (1) of the barrier methods

Answer 37

ADVANTAGES - don't use hormones so they don't have side effects - can reduce the risk of STIs DISADVANTAGES - [condoms] can break or slip off

Question 38

what does the **coil** do?

Answer 38

prevent an embryo from implanting

Question 39

advantages (1) and disadvantages (1) of the coil?

Answer 39

ADVANTAGES - highly effective and can prevent pregnancy for up to 10 years DISADVANTAGES - does not protect against STIs

Question 40

what is **sterilisation** in females?

Answer 40

prevents the egg from reaching the uterus

Question 41

what is **sterilisation** in males?

Answer 41

prevents the sperm from leaving the penis

Question 42

advantages (1) and disadvantages (2) of sterilisation?

Answer 42

ADVANTAGES - very effective in both genders DISADVANTAGES - very difficult for them to be reversed - do not protect against STIs

Question 43

two treatments for **infertility**

Answer 43

1. women are given both FSH and LH *("a fertility drug")* which causes a woman to ovulate more than usual 2. *in-vitro fertilisation* (IVF) where the fertilisation takes place outside of the body

Question 44

what are the *three* possible problems with IVF

Answer 44

1. success rates are not high 2. emotionally very stressful for both parents 3. can lead to multiple births