P2 T1: Hormonal Coordination in Humans

What is the name of the body’s coordination system involving hormones?

The endocrine system

What is a hormone?

A chemical messenger secreted by a gland - it travels in the blood to a target organ where it causes a response

What type of organ secretes hormones?

Glands

Which gland controls many other glands in the body?

Pituitary gland

Why is the pituitary gland considered a master gland?

It secretes a wide range of hormones, some of which stimulate other endocrine glands

What is the role of the pituitary gland?

Secretes human growth hormone - controls human growth, stimulates thyroid gland, stimulates ovulation & production of oestrogen, stimulates production of sperm & testosterone

What is the role of the thyroid gland?

Secretes the hormone thyroxine - controls metabolism, heart rate and body temperature

What is the role of the pancreas?

Secretes the hormone insulin - controls blood glucose levels

What is the role of the adrenal gland?

Secretes adrenaline - controls the body’s fight or flight response

What is the role of the ovaries?

Secretes oestrogen - coordinates menstrual cycle & the development of female secondary sexual characteristics

What is the role of the testes?

Secretes testosterone - coordinates the production of sperm & development of male secondary sexual characteristics

Which organ monitors & controls blood glucose concentration?

Pancreas

How does the pancreas respond when blood glucose levels are too high?

The pancreas secretes the hormone insulin - insulin binds to receptors on the liver & muscles, causing excess glucose to be converted into glycogen & stored

How does the pancreas respond when blood glucose levels are too low?

The pancreas secretes glucagon - glucagon binds to liver cells causing glycogen to be converted into glucose & released into the blood

How is blood glucose concentration controlled using negative feedback loop?

When the blood glucose concentration rises or falls below the optimum, a hormone is secreted by the pancreas. The action of either hormone (insulin or glucagon) helps bring back the concentration to the correct level

What is type 1 diabetes?

An autoimmune disorder where the pancreas doesn’t produce enough insulin to control the blood glucose concentration - as a result, blood glucose levels are often high - leading to excessive urination, tiredness & weight loss

How can type 1 diabetes be treated?

Insulin injections - allowing glucose to be converted into glycogen, limiting carbohydrate intake, pancreas and pancreatic cell transplants - investigations into genetic engineering of pancreatic cells

What is type 2 diabetes?

A disorder in which body’s cells stop responding to insulin, leading to an uncontrolled blood glucose concentration - it’s onset is linked with increasing age and obesity

How can type 2 diabetes be treated?

A careful, controlled diet, regular exercise, losing weight, use of drugs which increase insulin production and effectiveness

What is the function of reproductive hormones during puberty in males?

Cause the development of secondary sexual characteristics

What is the function of reproductive hormones during puberty in females?

Cause the development of secondary sexual characteristics & the maturation of eggs

What is the main male reproductive hormone?

Testosterone - produced by the testes & controls sperm production

What is the main female reproductive hormone?

Oestrogen - produced by the ovaries & involved in menstrual cycle

What is the menstrual cycle?

Monthly cycle of changes that occur in females - shedding of uterus lining (menstruation) & ovulation

What are the events of the menstrual cycle?

Uterus lining thickens and egg begins to mature in ovaries, egg is released from ovaries (ovulation), if the egg is fertilised pregnancy may occur, if not both the egg & uterus lining shed

What is ovulation?

The release of a mature egg from the ovaries, which occurs approximately every 28 days

What are the four main hormones involved in the menstrual cycle?

Oestrogen, progesterone, FSH, LH

What is the role of FSH?

Secreted by pituitary gland, controls maturation of eggs within ovaries, triggers production of oestrogen by ovaries

What is the role of oestrogen?

Produced by the ovaries & released due to the action of FSH - it causes regrowth of the uterus lining - it triggers the production of LH & restricts release of more FSH

What is the role of LH?

Produced in the pituitary gland as a result of oestrogen, its release triggers ovulation

What is the role of progesterone?

Thickens uterus lining

How does the contraceptive pill prevent pregnancy?

Inhibits FSH - eggs don’t mature, prevents development of uterus lining so eggs can’t implant, increases thickness of cervical mucus

What is the contraceptive implant?

A small rod inserted under the skin which continuously releases the hormone progesterone - lasts for 3 years

What is the contraceptive injection?

Injection containing progesterone - lasts for approximately 3 months

What is the IUS?

A small plastic device inserted into the uterus - releases progesterone which thickens cervical mucus & prevents build up of uterine lining

What is the IUD?

A small copper-containing device into the uterus which prevents the implantation of embyros

What is a barrier method?

A physical separation between the sperm & egg

Condoms - protects against STIs & pregnancy but can tear/break

Diaphragms - thin cap placed over cervix, prevent entry of sperm

What surgical methods of contraception are available?

Sterilisation - in males the sperm ducts are tied (vasectomy), in females the oviducts are tied

How do fertility drugs increase the chance of pregnancy?

Many contain FSH - which simulates oestrogen production & the maturation of eggs in the ovary - also contain LH which triggers ovulation

What is IVF?

Mother is given FSH & LH - stimulates maturation of eggs & ovulation

Eggs are fertilised using sperm in a lab - develop into embryos

1 or 2 embryos are insterted into the womb

What are the advantages of fertility treatment?

Allows infertile couples to have children, can store a woman’s eggs for later

What are the disadvantages of fertility treatment?

Can be very expensive, low success rate, increases chance of multiple pregnancies which is dangerous for mother & babies, side effects of fertility drugs

What is negative feedback?

A type of control where the body responds to an increase or decrease in a factor by returning it to the optimum level

What is thyroxine?

A hormone released by thyroid gland - release triggered by TSH, controls metabolic rate, growth & development

How is the release of thyroxine controlled by negative feedback?

Levels of blood thyroxine falls - detected by receptors in the brain, pituitary gland releases more TSH, more thyroxine produced & released by thyroid gland, blood thyroxine level returns to normal

What is adrenaline?

A hormone secreted by the adrenal gland in times of stress - responsible for fight or flight response

What are the effects of adrenaline?

Increase in heart & breathing rate - delivers oxygen & glucose to body, stored glycogen converted to glucose, dilation of pupils, increased mental awareness, blood diverted away from digestive system to muscles