Animal Coordination, Control and Homeostasis

What are hormones?

Chemical messengers that target organs in the body

How do hormones move throughout the body?

They are secreted and released into the blood until they reach their target organ

What produces hormones?

The endocrine gland

What do hormones cause when they reach their target organ?

• They cause a response by the target organ, for example the organ may release another chemical substance

• Different hormones have different target organs and cause different responses

What is the difference between nerves and hormones?

• Nerves have a short term effect

• Hormones have a long-lived effect

• Nerve impulses move quicker while hormones take longer to work

What is the endocrine system made of?

Pituitary, hypothalamus, thyroid, adrenal, pancreas, testes and ovaries

What hormones does the pituitary gland secrete?

TSH, ADH and LH

What hormone does the thyroid gland secrete?

Thyroxine

What hormones does the pancreas secrete?

Insulin and glucagon

What hormone do the testes secrete?

Testosterone

What hormones does the hypothalamus secrete?

TRH, CRH

What hormones does the adrenal gland secrete?

Adrenaline

What hormones do the ovaries secrete?

Oestrogen and progesterone

How does negative feedback work?

• A factor (such as blood glucose level) will have a level where there is a normal amount of it

• If this factor ever rises or falls bellow this normal level, there is a corrective mechanism

• This corrective mechanism will cause the factor to return to a normal level

What is the target organ for TRH and CRH?

Pituitary gland

What is the target organ for TSH?

Thyroid gland

What is the target organ for ADH?

Kidney

What is the target organ for FSH and LH?

Ovaries

What are the target organs for insulin and glucagon?

Liver, muscles and adipose tissue

What are the target organs for Adrenaline?

Various organs such as the heart, liver and skin

What is the target organ for progesterone?

Uterus

What are the target organs for oestrogen?

Ovaries, uterus, pituitary gland

What are the target organs for testosterone?

Male reproductive organs

What is adrenaline?

• A hormone that is released due to sudden stress

• It brings about the ‘fight or flight response’

What is thyroxine?

• A hormone that controls the metabolic rate- the rate at which cells respire

• It is measured as the rate of energy transfers in the body

How are thyroxine levels in the blood controlled?

1. Low thyroxine levels in the bloodstream stimulate the hypothalamus to release TRH and this causes the pituitary to release TSH so the thyroid releases more thyroxine. So blood levels return to normal.

2. Normal thyroxine levels in the bloodstream inhibit TRH release from the hypothalamus and the production of TSH by the pituitary, so normal blood levels are maintained which prevents them from getting too high

What are the effects of adrenaline?

• Increased heart rate

• Constricts some blood vessels to make blood pressure higher

• Dilates other blood vessels to increase blood flow to muscles

• Causes the liver to convert glycogen to glucose, which is released in the blood

How does adrenaline prepare muscles for fight or flight?

• Increased heart rate causes more oxygen to be carried around the body faster, so respiration in cells happens faster

• Blood glucose concentration also increases making glucose more available in muscle cells

What is the menstrual cycle?

• Happens between puberty and the age of 50

• A cycle that happens about every 28 days

• During the cycle, changes take place in the ovaries and uterus

What happens within the first week of the menstrual cycle?

• Menstruation is the breakdown of the uterus lining

• It begins on day one and usually lasts 5 days

What happens in the fourth week of the menstrual cycle?

• The lining of the uterus is gradually built up and then will falls which restarts the cycle

• If fertilisation occurs, the uterus lining will not fall

What happens on day 14 on the menstrual cycle?

• Ovulation

• This is the release of an egg from an ovary

Which days within the menstrual cycle is fertilisation most likely to take place?

Days 14 to 16

What happens in week 3 and 4 of the menstrual cycle?

The lining of the uterus continues to build up

What happens if the fertilisation of an egg occurs?

The uterus lining is maintained and menstruation does not happen

Why does the uterus lining remain thick after fertilisation?

So the embryo can embed in the lining and obtain the nutrients it needs

What is contraception?

The prevention of fertilisation

How do hormonal contraceptives work?

Hormonal contraceptives- hormone pills, implants or injections and works by releasing hormones to prevent ovulation and thicken mucus at the cervix preventing sperm from passing

How do barrier methods of contraception work?

• Male and female condom, the diaphragm, caps and sponges

• These are physical barriers stopping the sperm from reaching the egg

Which method of contraception is more effective, hormonal or barrier methods?

Hormonal methods

What can barrier methods of contraception do that hormonal contraceptives can’t?

Prevent STDs (sexually transmitted diseases)

What four hormones control the menstrual cycle?

Oestrogen, progesterone, FSH and LH

How does FSH, LH, oestrogen and progesterone control the menstrual cycle?

• FSH is secreted from the pituitary gland causing a follicle in the ovary to mature

• As it matures, it secrets oestrogen which inhibits the production of FSH causing the lining of the uterus to thicken

• A high concentration of oestrogen causes a surge in LH from the pituitary gland which causes ovulation (the egg being released from the follicle)

• The ruptured follicle becomes a corpus luteum that secretes progesterone and some oestrogen which causes the uterus lining to thicken more and be maintained

• Progesterone inhibits LH and FSH- If the egg is not fertilised, the corpus luteum breaks down and progesterone concentration falls

• The fall in progesterone and oestrogen causes the uterus lining to break down and triggers menstruation, progesterone is no longer inhibiting FSH, so it can be secreted from the pituitary gland again

What does the fertility drug clomifene do?

• Causes an increase in the hormones FSH and LH

• The drugs can help women who produce too little FSH by stimulating eggs to mature and then be released

What is IVF (in-vitro fertilisation)?

• Fertilisation outside a woman’s body

• Offered to couples having difficulty conceiving a child

How does IVF work?

1. Fertility drug given to woman to stimulate eggs to mature

2. Eggs are taken from the ovaries

3. The eggs are mixed with sperm in a dish for fertilisation

4. The fertilised eggs develop into embryos

5. When the embryos are tiny balls of cells, one or two of them are place in the mother’s womb to develop

What is homeostasis?

The regulation of all internal conditions in a body to maintain optimum conditions for all functions

What is osmoregulation?

The control of how much water is lost in urine and so, controls the amount of water in the body

Why is osmoregulation important?

It stops animal cells from swelling up or shrinking by osmosis if the water content of the body changes

What does osmoregulation do when your body gains water from food and drink?

• There is too much water in the body

• The brain detects this change and causes more water to be excreted in urine

• The water content in the body returns to normal

What does osmoregulation do when your body loses water when breathing out, sweating and by urinating?

• There is too little water in the body

• The brain detects the change and causes less water to be excreted in urine

• The water content in the body returns to normal

Why does urine sometimes appear as a dark yellow?

If you don’t drink enough water, the body will cause less water to be excreted in urine, so it appears darker

What is thermoregulation?

Keeping core body temperature steady around 37 degrees

What is thermoregulation controlled by?

• The hypothalamus which triggers changes in the skin and muscles

• The thermoregulatory centre in the hypothalamus of the brain monitors and controls core body temperature

What does thermoregulation do when body temperature is too high?

• Hypothalamus in brain detects rise and causes body responses

• Changes triggered in blood flow so more bloody flows near skin surface

• Sweat gland release more sweat onto skin to evaporate

• Sebaceous glands produce oil that helps spread sweat out over skin

• These increase transfer of energy to the surroundings

What does thermoregulation do when body temperature is too low?

• Hypothalamus in brain detects fall and causes body responses

• Less blood flows near skin surface

• Sweat glands stop producing sweat

• Body hairs raised by erector muscles in skin- this traps an insulating layer of air

Why is it important to control body temperature?

Enzymes in the main organs are most active at this temperature

How is the structure of skin important in thermoregulation?

• Sweat glands release sweat when warm to lose heat by evaporation

• Vasoconstriction/vasodilation changes blood flow through surface capillaries depending on temperature

• Hair muscles contract when cold to pull hairs upright, trapping and insulating layer of air. When warm, they lie flat

What is vasoconstriction?

• More blood flows through deep skin blood vessels so less blood flows through surface capillaries

• This keeps warm blood deeper so less heat is transferred to air

• Little heat is lost from skin

What is vasodilation?

• Blood vessel dilate/get larger

• Less blood flows through deep skin blood vessels and more blood flows through surface capillaries

• This increases the flow of warm blood near skin so the heat and easily transfer to air

• More heat is lost from the skin

What hormones is blood glucose regulation controlled by?

The hormones insulin and glucagon

What happens in blood glucose regulation when the concentration of blood glucose rises after a meal?

• Pancreas detects a rise in blood glucose concentration

• Pancreases increases the secretion of insulin and decreases the secretion of glucagon

• Insulin causes muscle and liver cells to remove glucose from the blood and store it as glycogen

• Blood glucose concentration falls until it returns to normal

What happens in blood glucose regulation when the concentration of blood glucose falls after exercise?

• Pancreas detects a fall in blood glucose concentration

• Pancreas decreases secretion of insulin and increases the secretion of glucagon

• Glucagon causes liver cells to convert glycogen into glucose and release it into the blood

• Blood glucose concentration rises until it returns to normal

What is diabetes?

A disease where someone cannot control their blood glucose concentration properly

What is the cause of type 1 diabetes and how is it controlled?

• Type 1 diabetes occurs in childhood

• Cause: The immune system has damaged the person’s insulin-secreting pancreatic cells, so the person does not produce insulin

• Control: They have to inject insulin into the fat below the skin. They have to work out the right amount of insulin to inject so that the blood glucose concentration is kept within safe limits

What is the cause of type 2 diabetes and how is it controlled?

• This usually happens in older people who have lived unhealthy lives

• Cause: The person does produce insulin but their liver and muscle cells have become resistant to it

• Control: Most people can control their blood glucose concentration by eating foods that contain less sugar, exercising and using medication if needed

How do you calculate BMI?

BMI= Weight (kg)/Height² (m)

What does the urinary system do?

• Maintains water balance

• Removes excess substances absorbed from food

• Removes waste products from metabolism such as urea from the breakdown of proteins

Where is urea produced and why is it important to remove it?

• Produced from the breakdown of excess amino acids in the liver

• It can be toxic in excess

What do the renal veins do in the urinary system?

They carry cleaned blood back to the body

What do the ureters do in the urinary system?

Carries urine from the kidneys to the bladder

What does the renal arteries do in the urinary system?

Carries blood from the body to the kidneys

What do the kidneys do in the urinary system?

Removes substances including urea from the blood and makes urine

What does the bladder do in the urinary system?

• The bladder stores urine

• A muscle keeps the exit from the bladder closed until we decide to urinate

What does the urethra do in the urinary system?

Urine flows through the urethra to the outside of the body

What do kidneys contain about a million of and what do they do?

• Each kidney contains around 1 million tiny tubes called nephrons

• They make urine

How is urine made in the kidney?

• In the bowman’s capsule, small molecules are filtered from blood in the glomerulus (capillary knot) into the tubule containing water, glucose, salts and urea

• Selective reabsorption of glucose from tubule goes back into the blood by active transport

• Water that the body needs is reabsorbed into the blood from the tubule

• Urine containing urea and excess water leaves the kidney through the collecting duct and goes to the ureter

Why can’t large molecules like protein filter into a nephron?

They are too large so they stay in the blood

What does ADH control?

The amount of water reabsorbed from the nephrons. This regulates the water content of the blood.

How does ADH control the water content of the body when there is not enough water in the blood?

• The brain senses there is not enough water in the blood

• Pituitary gland releases more ADH

• More ADH make the collecting ducts in nephrons in the kidney more permeable

• More water is reabsorbed from the kidney tubule back into the blood

• A small volume of concentrated urine is produced

How does ADH control the water content of the body when there is too much water in the blood?

• The brain senses there is too much water in the blood

• Pituitary gland releases less ADH

• More ADH make the collecting ducts less permeable

• Less water is reabsorbed from the kidney tubule back into the blood

• A large volume of dilute urine is produced

What does ADH cause?

It increases the permeability of the cell membranes in the collecting ducts of the nephron so more water is reabsorbed from the urine by osmosis

What is kidney failure and why is it dangerous?

• When the kidney stops working properly

• Excess water, mineral ions and urea build up in the body which can be toxic

How can people with kidney failure be treated?

With dialysis or a kidney transplant

What does dialysis do?

It removes waste products from the blood such as urea so they don’t build up as toxins

How does dialysis work?

• It must be carried out every 2 or 3 days, usually in a hospital but it can be done at home

• The patient is connected to a machine containing dialysis fluid and are connected with a tube where their blood will flow into the machine, through it and back out again and into their body

• The dialysis fluid contains the same concentration of useful substances as blood so glucose and useful mineral ions are not lost

• The dialysis tubing is partially permeable which allows urea to diffuse out of the blood and into the dialysis fluid

• Useful substances from the dialysis fluid diffuse into the blood and restores the normal concentration of dissolved substances in the blood

• The cleaned blood then goes back into the patient

How does a kidney transplant work?

A healthy kidney is connected to the blood circulation, to do the work of the diseased kidneys

What is the problem with kidney transplants?

• The antigens on the transplanted kidney cells are different from antigens on cells in the patients body

• Antibodies in the patient’s immune system attack the transplanted kidney and reject it

How can rejection of a transplanted kidney be avoided?

• The antigens on the transplanted kidney and the patient’s tissues must be as similar in type as possible

• The patient must be treated for life with drugs to reduce the effects of the immune system- this means the patient may get more infections than normal