Biology - 11 Hormonal Coordination

Endocrine system

hormone system that regulates processes such as growth, reproduction, and metabolism

Hormone

chemical messengers that are produced in one tissue and affect another

How are hormones detected?

target organ has receptors on the cell membranes

Rapid-response hormones [2]:

- insulin
- adrenaline

What gland controls most hormone action?

pituitary gland

What hormones does the pituitary gland release? [3]

- ADH
- FSH
- TSH

Roles of the pituitary gland [4]:

- control growth in children
- stimulates the thyroid to regulate metabolism
- (in women) stimulates ovaries to produce and release eggs and oestrogen
- (in men) stimulates the testes to produce eggs and testosterone

Role of the thyroid gland:

controls the metabolic rate of the body

Role of the pancreas:

controls blood glucose levels

Role of the adrenal gland:

prepare body for stressful situations

Roles of the ovaries [2]:

- controls development of female secondary sex characteristics
- regulates the menstrual cycle

Roles of the testes [2]:

- controls development of the male secondary sex characteristics
- regulates sperm production

What does insulin do? [3]

- allows glucose to pass into the body's cells for respiration
- causes the liver to convert glucose into glycogen
- regulates the storage of glycogen in muscles and liver

When is insulin produced?

when blood sugar is high

Glycogen

insoluble form of glucose, used for storage

What happens to excess glucose?

it is converted into lipids and stored

What does glucagon do?

raises blood sugar levels by making the liver break down glycogen

Negative feedback

a mechanism of homeostasis, where a change in a variable that is being monitored triggers a response that counteracts the change

What causes type 1 diabetes?

when the pancreas does not make enough/any insulin

Effects of untreated type 1 diabetes [5]:

- blood glucose concentration is very high after eating
- kidneys excrete glucose in the urine
- a lot of urine is produced leading to dehydration
- glucose cannot be used for respiration leading to lack of energy
- fat and protein are used instead, so weight is lost

What causes type 2 diabetes?

body cells stop responding to insulin

What causes type 2 diabetes to develop? [4]

- obesity
- lack of exercise
- age
- genetic tendency

How is type 1 diabetes treated?

insulin injections before meals

How could type 1 diabetes be cured? [3]

- pancreatic transplant
- pancreatic cell transplant
- stem cells

What are the issues with a pancreatic transplant? [3]

- not enough donors
- risky operation
- patient must take immunosuppressants

How could stem cells be used to treat type 1 diabetes?

therapeutic cloning and use of the embryonic stem cells to produce insulin-producing cells with no rejection

How is type 2 diabetes treated without medical intervention? [3]

- eating a balanced diet and regulating carbohydrates
- losing weight
- regular exercise

How is type 2 diabetes treated with medical intervention? [4]

- drugs that increase cells' sensitivity to insulin
- drugs that help pancreas produce more insulin
- drugs that reduce the amount of glucose absorbed from the gut
- insulin injections

What is used to produce thyroxine?

iodine

What does thyroxine do? [2]

- regulates the basal metabolic rate
- affects the development of a child's brain

TSH

Thyroid Stimulating Hormone (thyrotropin)

What does TSH do?

stimulates thyroid to produce thyroxine

TRH

Thyrotropin Releasing Hormone

What releases TRH?

the hypothalamus

What releases TSH?

the pituitary gland

What does TRH do?

stimulates pituitary gland to release TSH

Why is adrenaline released?

in response to stressful or scary situations

What are the effects of adrenaline? [5]

- increase in heart rate and breathing rate
- glycogen converted to glucose for respiration
- pupils dilate to let in light
- mental awareness increases
- blood is diverted away from digestion and to limb muscles

How does adrenaline cause effects?

boosts delivery of oxygen and glucose to brain and muscles

Oestrogen

main female reproductive hormone, produced in the ovaries

What does oestrogen do? [2]

- triggers gradual changes of puberty
- involved in menstruation

Ovulation

release of an egg from the ovary

FSH

Follicle Stimulating Hormone

What does FSH do? [2]

- causes eggs to mature
- stimulates oestrogen release

LH

Luteinising Hormone

What does LH do? [2]

- causes ovulation
- forms corpus luteum (empty follicle)

What does oestrogen do in the menstrual cycle? [3]

- thickens uterine lining
- inhibits FSH
- (in high levels) stimulates release of LH

What does progesterone do in the menstrual cycle?

- maintains uterine lining
- inhibits FSH and LH

Testosterone

main male reproductive hormone, produced in the testes

Stage 1 of the menstrual cycle

menstruation

Stage 2 of the menstrual cycle

uterine lining starts to build up

Stage 3 of the menstrual cycle

ovulation

Stage 4 of the menstrual cycle

maintaining the lining of the uterus

How do levels of oestrogen vary throughout the cycle? [2]

- rise until ovulation to develop uterine lining and stimulate release of LH
- fall as lining maintains and menstruation starts

How do levels of progesterone vary throughout the cycle? [2]

- stays constant until rising in stage 4 to maintain lining and inhibit FSH and LH
- falls to begin menstruation

How do levels of FSH vary throughout the cycle? [3]

- raises in stage 1 to cause release of oestrogen
- falls in stage 2 due to oestrogen inhibiting
- low peak at ovulation, when egg matures

How do levels of LH vary throughout the cycle? [2]

- stay constant most of cycle
- peak at stage 3, causing ovulation

Types of hormone-based contraception [3]:

- contraceptive pill
- contraceptive implant
- contraceptive patch

Mixed pill [3]

- contraceptive pill containing oestrogen and progesterone
- inhibit release of FSH and LH to stop eggs maturing
- makes cervical mucus thick

Progesterone-only pill [4]

- contraceptive pill containing only progesterone
- fewer side effects
- must be taken regularly
- inhibits FSH and LH

Contraceptive implant [3]

- inserted under the skin
- slowly releases progesterone
- inhibits FSH and LH

Contraceptive patch [3]

- patch containing oestrogen and progesterone
- replaced once a week
- inhibits FSH and LH

Spermicide [2]

- kills or disables sperm
- not very effective

Barrier methods [2]:

- condom
- diaphragm

Intrauterine device (IUD) [3]

- inserted into the uterus
- last 3-5 years
- can be copper or contain progesterone

Abstinence

not having sex

Surgical methods [2]

- vasectomy (male sterilisation)
- female sterilisation

Vasectomy

sperm ducts are cut and tied

Female sterilisation

oviducts are cut and tied

Treatment for lack of ovulation [2]

- artificial FSH is given to stimulate maturation of an egg
- artificial LH is given to cause ovulation

Why would IVF be used? [3]

- damage to oviducts
- use of donor egg
- no obvious cause for infertility

IVF process [4]:

- artificial FSH and then LH given to cause eggs to mature and come to point of ovulation
- eggs are collected and fertilised with sperm
- fertilised eggs are kept in warm solution to form embryos
- one or two embryos are inserted into the womb

Disadvantages of IVF [6]:

- expensive for society and individuals
- not always successful
- fertility drugs have health risks
- process is stressful for mother
- increases chance of multiple pregnancy
- ethical problems with excess embryos

Tropism

growth response of a plant toward or away from a stimulus

Phototropism

growth response to light

Gravitropism/geotropism

growth response to gravity

Auxin

a plant hormone that promotes root formation and bud growth

How does auxin distribution cause phototropism? [2]

- auxin moves to the shadowed side
- the shadowed side grows causing the plant to bend

How do shoots react to auxin?

shoots grow more with more auxin

How do roots react to auxin?

roots grow less with more auxin

How does auxin distribution cause gravitropism? [3]

- auxin moves downward due to gravity
- roots are inhibited, so they bend downwards
- shoots grow more, so they bend upwards

Rooting powder [3]

- also called IAA
- powder containing auxin
- cuttings are dipped to promote root growth

Auxin weed killer [3]

- auxin causes plants to grow uncontrollably, killing them
- most weeds are broad-leaved, while crops are narrow-leaved
- weeds are killed while crops are spared

Uses of auxins [3]

- promote root growth in cuttings
- weed killer
- cloning plant tissue cultures

Gibberellins [3]

- promote flowering
- promote germination/end seed dormancy
- increase size of fruit

Uses of gibberellins [3]

- in brewing industry to speed up germination for growth of barley for malt
- to promote flowering throughout the year
- to increase the size of fruit (especially seedless)

Ethene

promotes fruit ripening so fruits can be safely transported