Hormones and homeostasis
By the end of this chapter you will be able to
- Explain homeostasis and the role of hormones in the endocrine system
- Explain how the body lowers and raises blood glucose
- Compare type 1 and type 2 diabetes, and their treatments
- Describe how the body keeps its temperature constant, and when adrenaline is released
- [H] Name the hormones of the menstrual cycle and their roles, and interpret a blood glucose graph
You should already know
- Nervous system and reflexes (Chapter 11)
- Respiration releases energy (Chapter 10)
- Glucose and starch (Chapter 9)
Where this leads
- Immunity and vaccination (Chapter 14)
- Heredity and sex determination (Chapter 15)
- Plant hormones (Chapter 12 links to growth in Chapter 8)
GCSE Biology. Content follows the GCSE (9-1) subject content for England (Edexcel and AQA). Content references: Describe homeostasis as keeping internal conditions constant, and the endocrine system, Describe how insulin and glucagon control blood glucose, Compare type 1 and type 2 diabetes and their treatments, Describe thermoregulation, and the role of adrenaline, [H] Describe the roles of FSH, LH, oestrogen and progesterone in the menstrual cycle, and hormonal contraception, infertility treatment and ADH.
Exercise P Do you remember?
Method. Multiply 5 by 7.
- Multiply. 5 x 7 = 35.5 x 7 = 35
- Write the answer. 35
Check. 35 divided by 7 is 5. ✓
Method. Recall the gland that makes insulin.
- Recall. Insulin is made in the pancreas.made in the pancreas
- Write the answer. pancreas
Check. The pancreas also makes digestive enzymes. ✓
Method. Recall what sweat is mostly made of.
- Recall. Sweat is mostly water, and it is the water that evaporates.mostly water
- Write the answer. water
Check. Evaporation takes heat from the skin. ✓
Method. Recall the definition.
- Recall. Homeostasis is keeping the internal conditions of the body constant.keeping conditions constant
- Write the answer. keeping internal conditions constant
Check. Homeostasis works with feedback. ✓
Method. Recall the system with impulses.
- Recall. The nervous system carries electrical impulses quickly.electrical impulses
- Write the answer. nervous system
Check. Hormones are the other system. ✓
Homeostasis and the endocrine system
Homeostasis is the maintenance of a constant internal environment, such as body temperature, blood glucose and water content. It works by negative feedback: a change is detected, and a response reverses the change.
The endocrine system is a set of glands that release hormones into the blood. Hormones travel in the blood to a target organ, which has the receptors for them. The pituitary gland is often called the master gland, because it releases hormones that control other glands. The thyroid gland releases thyroxine, which controls the metabolic rate.
Key ideas
- Homeostasis keeps internal conditions constant, by negative feedback.
- Hormones are chemical messengers released into the blood by glands.
- Hormones act on target organs with the right receptors.
- Hormone responses are slower than nerve impulses, but they last longer.
Method. Recall the process.
- Recall. Keeping internal conditions constant is called homeostasis.homeostasis
- Name it. So the word is homeostasis.homeostasis
- Write the answer. homeostasis
Check. It uses negative feedback. ✓
Method. Recall the gland that controls other glands.
- Recall. The pituitary gland releases hormones that control other glands.controls other glands
- Name it. It is called the master gland.pituitary gland
- Write the answer. pituitary gland
Check. The thyroid gland is controlled by the pituitary. ✓
Method. Recall the thyroid hormone.
- Recall. The thyroid gland releases thyroxine.thyroxine
- Name it. Thyroxine controls the metabolic rate.thyroxine
- Write the answer. thyroxine
Check. Thyroxine is an idea for this level. ✓
Watch out
Watch out: hormones are carried in the blood to all parts, but only the target organ responds, because only it has the right receptors.
Exam tip
Exam tip. When you describe homeostasis, say what is kept constant, what detects the change, and what reverses it.
Try it (with your teacher). With your teacher, look at a labelled diagram of the endocrine glands. Name four glands, and write one hormone that each releases.
Exercise 12A Homeostasis and the endocrine system
Method. Recall the process.
- Recall. Homeostasis keeps internal conditions constant.keeps internal conditions constant
- Write the answer. homeostasis
Check. Homeostasis uses feedback. ✓
Method. Recall the messengers.
- Recall. Hormones are chemical messengers released into the blood.chemical messengers
- Write the answer. hormones
Check. Nerve impulses are electrical. ✓
Method. Recall the master gland.
- Recall. The pituitary gland controls other glands.controls other glands
- Write the answer. pituitary gland
Check. Its hormones include FSH and LH. ✓
Method. Recall the gland.
- Recall. The thyroid gland releases thyroxine.releases thyroxine
- Write the answer. thyroid gland
Check. Thyroxine controls the metabolic rate. ✓
Method. Think about receptors.
- Think. A hormone only affects the cells that have its receptors.has its receptors
- Conclude. That organ is the target organ, and it responds to the hormone.responds to the hormone
- Write the answer. Accept any sentence that says it is the organ that has the receptors for a particular hormone and responds to it.
Check. Receptors make the target specific. ✓
Method. Recall how hormones move.
- Recall. Hormones are carried in the blood.carried in the blood
- Write the answer. blood
Check. Nerve impulses travel along neurones. ✓
Method. Compare the two systems.
- Compare. Hormones travel in the blood, which is slower than an electrical impulse.slower than an electrical impulse
- Decide. So the response is slower, but it lasts longer.slower
- Write the answer. slower
Check. Hormone effects can last for a long time. ✓
Method. Recall the feedback.
- Recall. Negative feedback reverses a change, so the condition returns to normal.reverses a change
- Write the answer. negative feedback
Check. Positive feedback is not used in homeostasis. ✓
Method. Recall the hormone that lowers glucose.
- Recall. Insulin lowers blood glucose.lowers blood glucose
- Write the answer. insulin
Check. Glucagon raises blood glucose. ✓
Method. Think about the cells.
- Think. Cells need glucose for respiration, but too much or too little is harmful.too much or too little
- Conclude. So blood glucose is kept within a narrow range.narrow range
- Write the answer. Accept any sentence that says cells need a steady supply of glucose and the body must not become too high or too low.
Check. Homeostasis keeps the level in a safe range. ✓
Method. Think about the receptors.
- Think. A hormone acts only where it binds to its specific receptors.specific receptors
- Conclude. If the cells do not have them, the hormone has no effect.no effect
- Write the answer. Accept any sentence that says the target cells do not have the receptors for the hormone.
Check. Receptors make the response specific. ✓
Method. Link the transport to the duration.
- Blood. The hormone circulates in the blood for a time, so it can keep reaching the target.keep reaching
- Effect. It changes the target cells, and the change can continue after the hormone is removed.continues
- Write the answer. Accept any answer that says the hormone stays in the blood for a time and changes the target cells, so the effect continues.
Check. The duration depends on how long the hormone lasts. ✓
Blood glucose, insulin and glucagon
After a meal, glucose is absorbed from the gut into the blood, and blood glucose rises. The pancreas detects this and releases insulin. Insulin acts on the liver and muscle cells, which take up glucose and store it as glycogen. Blood glucose then falls back to normal.
If blood glucose falls too low, the pancreas releases glucagon. Glucagon makes the liver break down glycogen and release glucose into the blood, so blood glucose rises again.
| Time after meal (min) | Blood glucose (mmol/dm3) |
|---|---|
| 0 | 5 |
| 30 | 7 |
| 60 | 9 |
| 90 | 8 |
| 120 | 6 |
| 150 | 5 |
| 180 | 5 |
Key ideas
- Insulin is released when blood glucose is high; it lowers blood glucose.
- Insulin makes liver and muscle cells take up glucose and store it as glycogen.
- Glucagon is released when blood glucose is low; it raises blood glucose.
- Glucagon makes the liver break down glycogen and release glucose.
Method. Recall the gland.
- Recall. Insulin is released from the pancreas.released from the pancreas
- Name it. So the organ is the pancreas.pancreas
- Write the answer. pancreas
Check. Glucagon is released from the same organ. ✓
Method. Find the highest point on the graph.
- Find. The highest value is 9 mmol/dm3.9
- Read the time. It occurs at 60 minutes after the meal.60 minutes
- Write the answer. 9 mmol/dm3 at 60 minutes
Check. The value falls after this. ✓
Method. Subtract the final value from the highest.
- Read. The highest is 9 and the value at 180 minutes is 5.9 and 5
- Subtract. The fall is 9 - 5 = 4 mmol/dm3.9 - 5 = 4
- Write the answer. 4
Check. 5 + 4 = 9. ✓
Watch out
Watch out: insulin lowers blood glucose and glucagon raises it. Do not mix them up; they act in opposite directions.
Exam tip
Exam tip. Name the hormone, the gland, the target organ and what it does, in that order.
Try it (with your teacher). With your teacher, plot the blood glucose graph on squared paper. Mark the times when insulin would be released, and when glucagon would be released.
Exercise 12B Blood glucose, insulin and glucagon
Method. Recall the hormone.
- Recall. Insulin lowers blood glucose.lowers blood glucose
- Write the answer. insulin
Check. Glucagon raises it. ✓
Method. Recall the hormone.
- Recall. Glucagon raises blood glucose.raises blood glucose
- Write the answer. glucagon
Check. Insulin lowers it. ✓
Method. Recall the storage form.
- Recall. Glucose is stored as glycogen in the liver and muscles.stored as glycogen
- Write the answer. glycogen
Check. Glycogen is broken down by glucagon. ✓
Method. Recall the organ.
- Recall. Glucagon makes the liver break down glycogen.break down glycogen
- Write the answer. liver
Check. The liver also stores glycogen. ✓
Method. Recall the hormone for low glucose.
- Recall. When blood glucose is too low, the pancreas releases glucagon.too low
- Write the answer. glucagon
Check. Insulin is for high glucose. ✓
Method. Read the graph.
- Read. The value is 7 mmol/dm3 at 30 minutes.30 minutes
- Write the answer. 30
Check. Glucose is rising at this time. ✓
Method. Read the graph.
- Read. The value at 120 minutes is 6.6
- Write the answer. 6
Check. It is falling towards normal. ✓
Method. Subtract the start from the peak.
- Read. The value is 5 at 0 minutes and 9 at 60 minutes.5 and 9
- Subtract. The rise is 9 - 5 = 4 mmol/dm3.9 - 5 = 4
- Write the answer. 4
Check. 5 + 4 = 9. ✓
Method. Think about the hormone.
- Think. After the peak, insulin is released in response to the high glucose.in response to the high glucose
- Conclude. Insulin makes the liver and muscle cells take up glucose, so it falls.take up glucose
- Write the answer. Accept any sentence that says insulin is released and makes the liver and muscle cells take up glucose.
Check. Negative feedback brings the level back. ✓
Method. Think about the low glucose.
- Think. After a long fast the stored glucose is used up, so blood glucose falls.falls
- Conclude. Glucagon makes the liver release glucose from glycogen to raise the level.release glucose
- Write the answer. Accept any sentence that says the liver releases glucose from glycogen when blood glucose is low.
Check. Glucagon is the second half of the control. ✓
Method. Describe the two hormones as a pair.
- Insulin. Insulin lowers the blood glucose when it is too high.lowers
- Glucagon. Glucagon raises it when it is too low.raises
- Conclude. Together they keep the level within a narrow range.narrow range
- Write the answer. Accept any answer that says insulin lowers high blood glucose, and glucagon raises low blood glucose, so the level stays in a narrow range.
Check. A pair of opposing hormones is a typical homeostatic pattern. ✓
Diabetes
Diabetes is a condition in which blood glucose is not controlled properly. In type 1 diabetes the pancreas makes little or no insulin, so blood glucose rises after meals. It is treated with insulin injections, with the dose matched to food. Type 2 diabetes is when the body cells do not respond well to insulin, or not enough insulin is made. It is linked to diet, obesity and inactivity, and it is treated with diet, exercise and sometimes medicine.
| Feature | Type 1 | Type 2 |
|---|---|---|
| cause | the pancreas makes little or no insulin (often autoimmune) | the body cells respond poorly to insulin, or too little is made |
| usual onset | often in childhood or young adults | often in adults; linked to diet, obesity and inactivity |
| treatment | insulin injections, carefully timed with diet | diet, exercise and sometimes medicine |
Key ideas
- Type 1: the pancreas makes little or no insulin; treated with insulin injections.
- Type 2: the cells respond poorly to insulin; linked to diet and inactivity.
- Both types cause blood glucose to stay high after meals.
- Diet and exercise help to manage type 2.
Method. Recall the treatment for type 1.
- Recall. Type 1 diabetes is treated with insulin injections.insulin injections
- Name it. So the hormone is insulin.insulin
- Write the answer. insulin
Check. Insulin is the hormone the pancreas does not make enough of. ✓
Method. Recall the risk factors.
- Recall. Type 2 diabetes is linked to diet, obesity and inactivity.diet, obesity and inactivity
- Choose one. Any one of these is a correct answer.any one
- Write the answer. Accept any one: diet, obesity, or inactivity.
Check. Type 2 can often be managed without insulin. ✓
Method. Think about the glucose from the food.
- Think. Food adds glucose to the blood after a meal.adds glucose
- Conclude. The insulin dose must match the glucose so that the level does not stay high.does not stay high
- Write the answer. The food adds glucose to the blood, so the insulin dose must match it to stop the level staying high.
Check. The body cannot make enough insulin to do this alone. ✓
Watch out
Watch out: type 1 and type 2 are not the same disease with a different cause. Type 1 is a shortage of insulin; type 2 is mainly a poor response to it.
Exam tip
Exam tip. When you compare the types, give the cause, the usual onset and the treatment for each.
Try it (with your teacher). With your teacher, look at a labelled chart of the causes and treatments of diabetes. Choose one piece of evidence that shows why diet matters for type 2, and write one sentence about it.
Exercise 12C Diabetes
Method. Recall the treatment.
- Recall. Type 1 diabetes is treated with insulin injections.insulin injections
- Write the answer. type 1
Check. Type 2 is treated with diet and exercise. ✓
Method. Recall the link.
- Recall. Type 2 diabetes is linked to diet, obesity and inactivity.linked to diet
- Write the answer. type 2
Check. Type 1 is not mainly linked to diet. ✓
Method. Recall the cause of type 1.
- Recall. Type 1 diabetes is caused by little or no insulin being made.little or no insulin
- Write the answer. So yes.yes
- Write the answer. yes
Check. Type 2 is mainly a poor response to insulin. ✓
Method. Recall the treatments.
- Recall. Type 2 is managed with diet, exercise and sometimes medicine.diet, exercise
- Choose one. Any one of these is correct.any one
- Write the answer. Accept any one: diet, exercise, or medicine.
Check. Insulin is also used in some cases. ✓
Method. Recall the hormone.
- Recall. The pancreas makes little or no insulin in type 1 diabetes.little or no insulin
- Write the answer. insulin
Check. Glucagon is not the missing hormone. ✓
Method. Recall the gland.
- Recall. The pancreas makes too little insulin in type 1 diabetes.makes too little
- Write the answer. pancreas
Check. The pancreas is the gland that makes insulin. ✓
Method. Think about the control.
- Think. In type 2 the cells do not respond well to insulin, so the glucose is not removed.not removed
- Conclude. So the blood glucose stays high after a meal.stays high
- Write the answer. So yes.yes
- Write the answer. yes
Check. Both types can leave glucose high after a meal. ✓
Method. Think about the muscles.
- Think. Exercise uses glucose in the muscles.uses glucose
- Conclude. It also helps the cells respond better to insulin.respond better
- Write the answer. Accept any sentence that says exercise uses up glucose and helps the cells respond to insulin.
Check. Exercise has more than one benefit. ✓
Method. Link the cause to the treatment.
- Cause. In type 2 the cells respond poorly to insulin.respond poorly
- Effect. So extra insulin has less effect than it would in type 1.less effect
- Write the answer. Accept any answer that says the cells respond poorly to insulin, so extra insulin has less effect.
Check. The cause decides the treatment. ✓
Thermoregulation and adrenaline
Thermoregulation keeps the core body temperature constant at about 37 degrees C. The brain detects the temperature of the blood, and it triggers responses that reverse any change.
When the body is too hot, sweat is released and evaporates, taking heat from the skin, and the blood vessels near the skin widen (vasodilation), so more heat is lost. When the body is too cold, the muscles shiver, releasing heat, and the vessels near the skin narrow (vasoconstriction), so less heat is lost.
Adrenaline is released from the adrenal glands in times of danger or excitement. It prepares the body for “fight or flight”: it raises the heart rate and breathing rate, and it raises blood glucose.
| Too hot | Too cold |
|---|---|
| sweating (evaporation takes heat away) | shivering (muscle contraction releases heat) |
| vasodilation (blood vessels near the skin widen) | vasoconstriction (vessels near the skin narrow) |
| hairs lie flat | hairs stand up (goosebumps) |
Key ideas
- Thermoregulation keeps the core temperature at about 37 degrees C.
- Hot: sweating and vasodilation; cold: shivering and vasoconstriction.
- Adrenaline is released in danger or excitement, and prepares the body to act.
- Adrenaline raises heart rate, breathing rate and blood glucose.
Method. Recall the cooling response.
- Recall. Sweating takes heat from the skin as the sweat evaporates.takes heat
- Name it. So the response is sweating.sweating
- Write the answer. sweating
Check. Shivering is the response to cold. ✓
Method. Recall the warming response.
- Recall. Shivering is muscle contraction that releases heat.releases heat
- Name it. So the response is shivering.shivering
- Write the answer. shivering
Check. Shivering is a quick way to warm up. ✓
Method. Recall the fight-or-flight hormone.
- Recall. Adrenaline is released in danger and raises the heart rate.raises the heart rate
- Name it. So the hormone is adrenaline.adrenaline
- Write the answer. adrenaline
Check. Adrenaline is from the adrenal glands. ✓
Watch out
Watch out: vasodilation and vasoconstriction act on the blood vessels near the skin, not on the heart. Do not say that the heart widens.
Exam tip
Exam tip. Name the response, then say whether it increases or decreases heat loss and why.
Try it (with your teacher). With your teacher, take your pulse at rest, then after one minute of brisk walking. Describe what happens to your breathing and heart rate, and link it to adrenaline or to muscle activity.
Exercise 12D Thermoregulation and adrenaline
Method. Recall the core temperature.
- Recall. The core body temperature is about 37 degrees C.37
- Write the answer. 37
Check. Thermoregulation keeps this constant. ✓
Method. Recall the cooling response.
- Recall. Sweating cools the body as the sweat evaporates.cools the body
- Write the answer. sweating
Check. Evaporation takes heat from the skin. ✓
Method. Recall the response.
- Recall. Vasodilation is the widening of blood vessels near the skin, so more heat is lost.widening
- Write the answer. vasodilation
Check. Vasoconstriction is the opposite. ✓
Method. Recall the response.
- Recall. Vasoconstriction narrows blood vessels near the skin, so less heat is lost.narrows
- Write the answer. vasoconstriction
Check. Vasodilation is the opposite. ✓
Method. Recall the cold response.
- Recall. In the cold, vasoconstriction narrows the vessels, so less heat is lost.less heat is lost
- Write the answer. narrow
Check. Less blood at the surface keeps the heat in. ✓
Method. Recall the gland.
- Recall. Adrenaline is released from the adrenal glands.released from the adrenal glands
- Write the answer. adrenal glands
Check. The adrenal glands sit on top of the kidneys. ✓
Method. Recall the effect.
- Recall. Adrenaline raises the heart rate.raises the heart rate
- Choose one. Either of these answers the question.either
- Write the answer. Accept any one: it raises the heart rate, or it makes the heart beat faster.
Check. It also raises the breathing rate. ✓
Method. Think about the energy in the muscles.
- Think. Muscle contraction uses energy from respiration.uses energy from respiration
- Conclude. Some of that energy is released as heat, which warms the body.released as heat
- Write the answer. Accept any sentence that says muscle contraction needs respiration, which releases heat.
Check. Respiration releases energy, some as heat. ✓
Method. Think about the body response.
- Think. The body can respond to a sudden cold stimulus by narrowing vessels.narrowing vessels
- Conclude. This keeps heat in, which is not what a hot body needs.not what a hot body needs
- Write the answer. Accept any sentence that says it may cause the body to shiver or narrow vessels, which keeps heat in.
Check. The aim is a steady core temperature. ✓
Method. Think about the muscles.
- Think. In danger the muscles need energy quickly.need energy quickly
- Conclude. More glucose supplies respiration in the muscles, so they can act.more glucose
- Write the answer. Accept any sentence that says more glucose is available for respiration in the muscles.
Check. Adrenaline prepares the body to act. ✓
Method. Link the effects to the response.
- Effects. Adrenaline raises the heart rate, breathing rate and blood glucose.raises
- Response. These prepare the body to fight or to run away quickly.fight or to run
- Write the answer. Accept any answer that says it prepares the body for quick action in danger, by raising heart rate and blood glucose.
Check. The effects all support fast action. ✓
The menstrual cycle, contraception and ADH [H]
[H] Higher tier only. This section is higher-tier content. It covers the menstrual cycle, hormonal contraception, infertility treatment and ADH.
[H] The menstrual cycle lasts about 28 days. FSH from the pituitary makes an egg mature in the ovary, and stimulates oestrogen production. Oestrogen builds up the lining of the uterus, and it stimulates a surge of LH. The LH surge triggers ovulation, when the egg is released. After ovulation, progesterone maintains the lining of the uterus. If there is no fertilised egg, the lining breaks down and is shed as menstruation.
[H] Hormonal contraception uses hormones such as oestrogen and progesterone, which inhibit FSH and LH, so no egg matures and no ovulation happens. Fertility treatment can use FSH and LH to stimulate the ovaries to release eggs.
[H] ADH is released by the pituitary when the blood is too concentrated (dehydration). It makes the kidney tubules more permeable to water, so more water is reabsorbed and the urine is more concentrated.
| Hormone (source) | Job in the menstrual cycle |
|---|---|
| FSH (pituitary) | makes an egg mature in the ovary; stimulates oestrogen production |
| oestrogen (ovary) | builds up the lining of the uterus; stops FSH and triggers LH |
| LH (pituitary) | surge triggers ovulation (the egg is released) |
| progesterone (ovary, after ovulation) | maintains the lining of the uterus |
Key ideas
- [H] FSH matures the egg and stimulates oestrogen.
- [H] Oestrogen builds the lining and triggers the LH surge.
- [H] LH triggers ovulation; progesterone maintains the lining.
- [H] ADH makes the kidneys reabsorb more water when the blood is concentrated.
Method. Recall the hormone that triggers the egg release.
- Recall. The LH surge triggers ovulation.LH surge
- Name it. So the hormone is LH.LH
- Write the answer. LH
Check. FSH matures the egg. ✓
Method. Recall the water hormone.
- Recall. When the blood is too concentrated, the pituitary releases ADH.releases ADH
- Name it. So the hormone is ADH.ADH
- Write the answer. ADH
Check. ADH makes the kidneys keep more water. ✓
Method. Think about the hormones.
- Think. The pill contains hormones that inhibit FSH and LH.inhibit FSH and LH
- Conclude. So no egg matures and no ovulation happens.no ovulation
- Write the answer. Accept any sentence that says the hormones stop FSH and LH, so no egg matures and no ovulation happens.
Check. No egg means no fertilisation. ✓
Watch out
Watch out: FSH and LH come from the pituitary; oestrogen and progesterone come from the ovaries. Do not swap the sources.
Exam tip
Exam tip. [H] For the menstrual cycle, name the hormone, its source and its job in one line each.
Try it (with your teacher). With your teacher, make a timeline of the menstrual cycle on a sheet of paper, placing FSH, oestrogen, LH and progesterone at the right points. Check the order with your teacher.
Exercise 12E [H] The menstrual cycle, contraception and ADH
Method. Recall the hormone that matures the egg.
- Recall. FSH makes an egg mature in the ovary.makes an egg mature
- Write the answer. FSH
Check. LH triggers ovulation later. ✓
Method. Recall the trigger.
- Recall. The LH surge causes the egg to be released.causes the egg to be released
- Write the answer. LH
Check. FSH matures the egg. ✓
Method. Recall the uterus lining hormone.
- Recall. Oestrogen builds up the lining of the uterus.builds up the lining
- Write the answer. oestrogen
Check. Progesterone maintains the lining after ovulation. ✓
Method. Recall the hormone after ovulation.
- Recall. After ovulation, progesterone maintains the uterus lining.maintains the uterus lining
- Write the answer. progesterone
Check. Oestrogen builds the lining before ovulation. ✓
Method. Recall the gland.
- Recall. ADH is released by the pituitary gland.released by the pituitary
- Write the answer. pituitary gland
Check. ADH acts on the kidneys. ✓
Method. Recall the effect of ADH.
- Recall. ADH makes the kidney tubules more permeable to water.more permeable to water
- Result. So more water is reabsorbed into the blood.more water reabsorbed
- Write the answer. makes them more permeable to water
Check. The urine becomes more concentrated. ✓
Method. Think about dehydration.
- Think. When the blood is too concentrated, the body needs to keep more water.keep more water
- Conclude. So more ADH is released.more ADH
- Write the answer. more
Check. Less ADH is released when the blood is dilute. ✓
Method. Recall the hormones in the pill.
- Recall. The pill contains hormones such as oestrogen and progesterone.oestrogen and progesterone
- Effect. These inhibit FSH and LH, so no egg is released.no egg is released
- Write the answer. Accept oestrogen and progesterone.
Check. The effect is to stop ovulation. ✓
Method. Think about what the couple need.
- Think. A woman who does not ovulate needs eggs to be released.eggs to be released
- Conclude. FSH and LH can stimulate the ovaries to release eggs.stimulate the ovaries
- Write the answer. Accept any sentence that says they stimulate the ovaries to release eggs.
Check. The treatment supports ovulation. ✓
Method. Link the water intake to ADH.
- Blood. With little water intake, the blood becomes more concentrated.more concentrated
- ADH. More ADH is released, making the kidneys reabsorb more water.reabsorb more water
- Conclude. So less water is lost, and the urine is more concentrated.more concentrated urine
- Write the answer. Accept any answer that says the blood becomes more concentrated, so ADH is released and the kidneys reabsorb more water.
Check. ADH is a negative feedback control. ✓
Chapter summary
| Skill | Method |
|---|---|
| Homeostasis | Keeping internal conditions constant, by negative feedback. |
| Endocrine system | Glands release hormones into the blood; the target organ has the receptors. |
| Blood glucose | Insulin (pancreas) lowers it; glucagon (pancreas) raises it, via the liver. |
| Diabetes | Type 1: little or no insulin, treated with injections. Type 2: cells respond poorly; diet and exercise. |
| Thermoregulation | Hot: sweating and vasodilation. Cold: shivering and vasoconstriction. |
| Adrenaline | Released in danger; raises heart rate, breathing rate and blood glucose. |
| [H] Menstrual cycle | FSH matures the egg; oestrogen builds the lining; LH triggers ovulation; progesterone maintains the lining. |
| [H] ADH | Released when blood is concentrated; kidney tubules reabsorb more water. |
Can you…?
- I can explain homeostasis and the role of hormones in the endocrine system
- I can explain how insulin and glucagon control blood glucose
- I can compare type 1 and type 2 diabetes and their treatments
- I can describe thermoregulation and the role of adrenaline
- [H] I can name the hormones of the menstrual cycle and explain ADH
Key terms
- homeostasis
- keeping the internal conditions of the body constant
- hormone
- a chemical messenger released into the blood by a gland
- target organ
- an organ with receptors for a particular hormone
- insulin
- a hormone that lowers blood glucose
- glucagon
- a hormone that raises blood glucose
- glycogen
- the storage form of glucose in the liver and muscles
- diabetes
- a condition in which blood glucose is not controlled properly
- vasodilation
- the widening of blood vessels near the skin
- adrenaline
- a hormone released in danger that prepares the body to act
- [H] ADH
- antidiuretic hormone, which makes the kidneys reabsorb more water
Exercise 12Z Check-up
Method. Recall the process.
- Recall. Keeping internal conditions constant is homeostasis.homeostasis
- Write the answer. homeostasis
Check. It uses negative feedback. ✓
Method. Recall the hormone.
- Recall. Insulin lowers blood glucose.lowers blood glucose
- Write the answer. insulin
Check. Glucagon raises it. ✓
Method. Recall the hormone.
- Recall. Glucagon makes the liver release glucose.release glucose
- Write the answer. glucagon
Check. Insulin does the opposite. ✓
Method. Recall the treatment.
- Recall. Type 1 diabetes is treated with insulin injections.insulin injections
- Write the answer. type 1
Check. Type 2 is treated with diet and exercise. ✓
Method. Recall the response.
- Recall. Shivering releases heat from the muscles.releases heat
- Write the answer. shivering
Check. Sweating is the response to heat. ✓
Method. Recall the hormone.
- Recall. Adrenaline raises the heart rate in danger.raises the heart rate
- Write the answer. adrenaline
Check. It is released from the adrenal glands. ✓
Method. Read the graph at 180 minutes.
- Read. The value at 180 minutes is 5.5
- Write the answer. 5
Check. It has returned to the start value. ✓
Method. Recall the gland.
- Recall. The thyroid gland releases thyroxine.releases thyroxine
- Write the answer. thyroid gland
Check. Thyroxine controls the metabolic rate. ✓
Method. Think about heat loss.
- Think. Wider vessels bring more blood close to the skin.more blood close
- Conclude. So more heat leaves the blood through the skin.more heat leaves
- Write the answer. Accept any sentence that says it lets more heat leave the blood through the skin.
Check. Vasodilation increases heat loss. ✓
Method. Recall the risk factors.
- Recall. Type 2 is linked to diet, obesity and inactivity.diet, obesity and inactivity
- Choose one. Any one of these is correct.any one
- Write the answer. Accept any one: diet, obesity, or inactivity.
Check. These are linked to the disease. ✓
Total 23 marks. Allow about 23 minutes.
Exercise 12X Exam-style questions
Method. Recall the hormone.
- Recall. Insulin is released when blood glucose is too high.too high
- Write the answer. insulin
Check. Glucagon is for low glucose. ✓
Method. Recall the gland.
- Recall. Adrenaline is released from the adrenal glands.adrenal glands
- Write the answer. adrenal glands
Check. They sit on the kidneys. ✓
Method. Recall the system.
- Recall. Hormones are released into the blood by glands, which is the endocrine system.endocrine system
- Write the answer. Accept endocrine.
Check. The nervous system is the other control system. ✓
Method. Follow the sequence of events.
- Rise. Blood glucose rises after a meal.rises
- Release. The pancreas releases insulin.releases insulin
- Effect. Insulin acts on the liver and muscles, which take up glucose and store it as glycogen.store it as glycogen
- Write the answer. Accept any three of: blood glucose rises; the pancreas releases insulin; insulin acts on the liver and muscles; they take up glucose and store it as glycogen.
Check. Glucose is removed from the blood. ✓
Method. Give two differences.
- Cause. Type 1 is little or no insulin being made; type 2 is cells responding poorly to insulin.little or no insulin
- Treatment. Type 1 is treated with insulin injections; type 2 with diet and exercise.insulin injections
- Write the answer. Accept any two correct differences, for example type 1 has little insulin and is treated with injections, and type 2 cells respond poorly and is treated with diet and exercise.
Check. Cause and treatment are linked. ✓
Method. List the cold responses.
- Shiver. The muscles shiver, which releases heat.shiver
- Narrow. The vessels near the skin narrow, so less heat is lost.narrow
- Hairs. In animals, the hairs stand up to trap warm air.hairs stand up
- Write the answer. Accept any three of: shivering releases heat; vasoconstriction narrows the vessels near the skin; less heat is lost; hairs stand up in animals.
Check. All three responses reduce heat loss or add heat. ✓
Method. Give the reason and the effects.
- Reason. Adrenaline is released in danger or excitement.in danger
- Effects. It raises the heart rate, breathing rate and blood glucose, preparing the body to act.preparing the body
- Write the answer. Accept any answer that says it prepares the body for fight or flight, raising heart rate, breathing rate and blood glucose.
Check. The effects all prepare the body to act. ✓
Method. Subtract, then name the hormone.
- Rise. The rise is 9 - 5 = 4 mmol/dm3.9 - 5 = 4
- Hormone. The high blood glucose causes the pancreas to release insulin.release insulin
- Write the answer. Accept 4 mmol/dm3, and insulin.
Check. 5 + 4 = 9. ✓
Method. Name each hormone with its job.
- FSH. FSH makes an egg mature in the ovary.FSH matures the egg
- Oestrogen. Oestrogen builds up the lining of the uterus.oestrogen builds
- LH. LH triggers ovulation.LH triggers ovulation
- Progesterone. Progesterone maintains the lining after ovulation.progesterone maintains
- Write the answer. Accept any four correct points, for example FSH matures the egg; oestrogen builds the lining; LH triggers ovulation; progesterone maintains the lining.
Check. Each hormone has one main job in the cycle. ✓
Method. Follow ADH from the blood to the urine.
- Trigger. When the blood is concentrated, the pituitary releases ADH.concentrated
- Action. ADH makes the kidney tubules more permeable to water.kidney tubules
- Result. So more water is reabsorbed into the blood.reabsorbed
- Urine. The urine becomes more concentrated.more concentrated
- Write the answer. Accept any answer that says ADH is released when blood is concentrated, makes kidney tubules more permeable, so more water is reabsorbed and urine is more concentrated.
Check. ADH is a negative feedback loop. ✓