B3.2 The Endocrine System

Question 1

What are hormones?

Answer 1

Hormones are chemical messengers which travel in the blood and control body processes that need constant adjustment

Question 2

What is homeostasis?

Answer 2

The maintenance of a constant internal environment

Question 3

What are endocrine glands?

Answer 3

Glands that produce and secrete a hormone

Question 4

What is the endocrine system

Answer 4

All endocrine glands and the hormones they produce

Question 5

What are target organs?

Answer 5

Organs a hormone has an effect on

Question 6

Differences between nervous impulses and hormones

Answer 6

Nerves travel to specific parts of the body, however hormones travel all around the body but only target organs respond. Nerves communicate very fast but hormones are slower. Nerves are short acting but hormones are long actingm

Question 7

How do hormones work on target cells

Answer 7

Hormones diffuse out of blood to bind specific receptors for that hormone, found on the membranes or in the cytoplasm of target cells. Once bound to their receptors the hormones stimulate the target cells to produce a response.

Question 8

Thyroid gland hormones

Answer 8

Thyroid gland secretes thyroid hormones which control the body’s metabolic rate

Question 9

What is thyroxine

Answer 9

Thyroxine is a hormone produced in the thyroid gland, and it plays a vital role in regulating the body’s metabolic rate - the speed at which the body’s chemical functions proceed,

Question 10

Function of thyroid gland

Answer 10

Secretes thyroid hormones. Takes iodine and convert it into thyroxine by combining it with the amino acid tyrosine

Question 11

What is negative feedback

Answer 11

Negative feedback is a system that detects a change in a condition. The system then acts to return conditions back to the desired level

Question 12

Adrenal glands located

Answer 12

Adrenal glands are located on top of both kidneys

Question 13

Adrenal gland hormones

Answer 13

At times of stress they secrete the hormone adrenaline, which prepares the body for intensive action, also known as ‘fight or flight’ response

Question 14

Effects of adrenaline

Answer 14

Adrenaline increases rate of ATP production, increases rate of breathing, increases heart rate, and diverts blood to muscles.

Question 15

What is the menstrual cycle

Answer 15

the menstrual cycle is the monthly reproductive cycle of female humans which is controlled by reproductive hormones. It prepares the woman’s body for pregnancy.

Question 16

Main stages of menstrual cycle

Answer 16

Menstruation - Day 1 to 5/7
Lining of uterus builds up - Day 5/7 to 14
Egg released - Day 14
Lining maintained - Day 14 to 28
After day 28, breaks down again

Question 17

What reproductive hormones does the pituitary gland secrete, and what are their function?

Answer 17

Pituitary gland secretes luteinising hormone + follicle stimulating hormone. They stimulate the ovaries to produce oestrigen + progesterone.
FSH - causes one fillicle to mature in the ovaries
LH - stimulates ovulation

Question 18

What reproductive hormones does the ovaries secrete, and what are their function?

Answer 18

Oestrogen and progesterone.
Oestrogen - stimulates the lining of the womb to build up for pregnancy.
progesterone - maintains the uterus lining for levels to stay hugh during pregnancy.

Question 19

Hormone interactions order

Answer 19

• FSH is secreted by the pituitary gland. It causes one follicle to mature in the ovaries and stimulates the ovaries to produce oestrogen. Oestrogen stimulates the lining of the uterus to build up for pregnancy. As oestrogen levels rise they inhibit FSH production. Oestrogen rises high enough to cause a surge in LH, which stimulates ovulation. Progesterone maintains the uterus lining, levels stay high during pregnancy.

Question 20

What are contraceptives and what are the types?

Answer 20

Any technique used too prevent pregnancy is known as contraception. They control fertility. You can classify contraception methods into teo groups:
Non hormonal - barrier methods that prevent sperm from contacting the egg or pysical devices that release chemical compounds. These chemicals kill sperm cells or prevent the implantation of fertilised eggs.
Hormonal - these use hormones to distrupt the normal female reproductive cycle

Question 21

Describe what IUD, IUS, combined pill, and progesterone pill do.

Answer 21

IUD (non hormonal) - inserted into the uterus. releases copper which prevents sperm surviving in the uterus and fallopian tubes. Can also prevent implantation of a fertalised ovum.
Combined pill (hormonal) - Prevents ovulation. Thickens mucus from the cervix to stop sperm reaching an ovum. Prevents implantation of a fertalised egg.
Progesterone pill (hormonal) - thickens mucus from the cervix to stop sperm reaching an ovum. Also thins lining of the uterus preventing implantation, and can prevent ovulation.
IUS - (hormonal) inserted into the uterus. Has the same effect on the body as progesterone pill.

Question 22

Describe some causes of infertility

Answer 22

• blocked sperm ducts
• not enough sperm being produced in the testes
• a lack of mature eggs produced in the ovaries
• a failure of the ovaries to release an egg

Question 23

describe how FSH and LH can be used as artificial fertility drugs

Answer 23

FSH stimulates eggs in the ovaries to mature, and also triggers oestrogen production.
LH triggers ovulation.

Question 24

Outline how IVF works (invitro fertalisation)

Answer 24

IVF involves doctors collecting eggs from the ovary of the mother and fertalising them with the sperm of the father outisde the body in the lab. FSH and LH are given to the mother to ensure that as many eggs as possible mature in her ovaries.

Question 25

Disadvantages of IVF

Answer 25

Unsuccessful attempts to have a baby can be highly physically and emotionally stressful to the parents. Increases the likelihood of multiple births. Very expensive but does not guarantee pregnancy. Relatively low success rates.

Question 26

What is the function of plant hormones?

Answer 26

Plant hormones enable a plant to coordinate and control changes in growth and development in response to changes in the enviroment.

Question 27

What is a tropism?

Answer 27

A tropism is a growth movement in response to a particular type of stimulus. If a part of a plant grows towards a stimulus, this is a positive tropism. If it grows away from the stimulus, it is a negative tropism.

Question 28

What is phototropism and gravitropism?

Answer 28

Phototropism means growing towards the light. It is a growth response to the stimulus of light. When a stem grows towards the light, the plant can photosynthesise more. This means that more food is produced for the plant, so it can grow faster. This increases the plants chances of survival. Gravitropism means growing in the same direction of gravity. It is a growth response to the stimulus of gravity. It is important for the roots to grow downwards, as growing deeper into the soil helps to provide anchorage. It normally takes the roots nearer to water.

Question 29

What is auxin?

Answer 29

Auxin is a plant hormone that enables a plant to grow towards or away from a stimulus. Auxin is made in cells near the tips of plant shoots or roots. The response to a stimulus occurs because of an uneven distribution of auxin. This causes an unequal growth rate, which results in the shoot or root bending. Auxin stimulates shoot cells to grow more, but inhibits the growth of root cells.

Question 30

Explain how plants respond to light

Answer 30

When light hits one side of a shoot tip, the auxin moves to the other side of the shoot, causing the concentration of auxin to build up in the unlit side. The cells then respond by elongating, increasing the length of this side of the shoot, so the shoot bends towards the light. When light falls evenly on the shoot the level of auxin is evenly distributed throughout the tip. All the cells in the tip grow at the same rate so the shoot grows straight.

Question 31

Explain how plants respond to gravity

Answer 31

Auxin is gathered on the lower side of both the roots and shoots. The root grows more on the side with the least auxin, making it bend and grow down towards the force of gravity. The shoot grows more on the side with the most auxin, making it bend and grow up away from the force of gravity.

Question 32

Main function of Auxins

Answer 32

Stimulate growth by causing cell elongation. They also help to regulate fruit development. Without auxins, fruits are often too small.

Question 33

Main function of Ethene

Answer 33

Causes plant fruits to ripen by stimulating the conversion of starch into sugar. It is the only plant hormone that exists in a gas.

Question 34

Main function of Gibberellins

Answer 34

promote growth, particularly stem elongation. Can also end the dormancy period of seeds and buds which leads to shoots and flowers opening.

Question 35

How are thyroxine levels controlled?

Answer 35

When the body requires more energy, the hypothalamus causes the pituitary gland to release thyroid stimulating hormone. TSH stimulates the thyroid gland to release thyroxine. This increases the metabolic rate, allowing cells to transfer additional energy. When cells have the required amount of energy, the hypothalamus inhibits the production of TSH. The thyroid gland therefore stops releasing thyroxine.