5.3 Hormonal Coordination in Humans

Human endocrine system

The endocrine system is composed of glands which secrete chemicals called hormones directly into the bloodstream

Blood carries hormones to target organs where they produce an effect

Responses carried out by the hormonal system are slower and longer lasting when compared to the nervous system

Pituitary gland

Is the master gland Secretes several hormones into the blood in response to body conditions Hormones from the pituitary gland act on other glands to stimulate other hormones to be

released to bring about effects

You need to be able to identify the position of these 6 glands/ organs on a diagram of the human body:

1. Pituitary gland2. Pancreas3. Thyroid4. Adrenal gland5. Ovary6. Testes.

Triple Science 9-1 Biology Unit 5 Homeostasis and Response Part 2

Endocrine System QUICK QUIZ:

1. What is the function of the endocrine system?2. What are hormones?3. How do hormones travel around the body?4. List two ways in which responses by the endocrine system differ from

responses of the nervous system5. Draw an outline of a person and identify the position of the 6 different

glands/ organs6. How is the function of the pituitary gland different to a normal gland?7. Why are some hormones called secondary messengers?

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Control of blood glucose concentration

Blood glucose concentration is monitored and controlled by the pancreas.

If the blood glucose concentration is too high…

The pancreas produces the hormone insulin that causes glucose to move from the blood into the cells.

In liver and muscle cells excess glucose is converted to glycogen for storage.

If the blood glucose concentration is too low…

The pancreas produces the hormone glucagon This causes glycogen to be converted into glucose and released into the blood.

The two hormones working together is an example of a negative feedback loop

Triple Science 9-1 Biology Unit 5 Homeostasis and Response Part 2

Top tip: Learn the spellings and definitions of the words:

Glycogen Glucose Glucagon

These words look similar and examiners know you might confuse them.

5.3.2 Control of blood glucose concentration QUICK QUIZ:

1. Which organ monitors blood glucose concentration2. Where are insulin and glucagon produced?3. Which two places in the body store glycogen?4. Describe what your endocrine system would if blood glucose levels

were too low 5. Describe what your endocrine system would if blood glucose levels

were too high 6. Describe the role of the liver in maintaining constant blood glucose

concentration

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Maintaining water and nitrogen balance in the body

If body cells lose or gain too much water by osmosis they do not function efficiently.

Water and ions leave the body in a number of ways which are not controlled: Via the lungs during exhalation Water, ions and urea are lost from the skin in sweat..

Excess water, ions and urea are removed via the kidneys in the urine as well but this can be controlled by the body as part of homeostasis

What is urea ?The digestion of protein from the diet results in excess amino acids. In the liver these amino acids are deaminated to form ammonia. Ammonia is toxic and so it is immediately converted to urea for safe excretion

The Kidney

ADH

( is a hormone which acts on the kidney tubules to absorb back more water into the blood)

ADH is released by the pituitary gland when the blood becomes too concentrated. It causes the kidney to reabsorb more water into the blood.

And therefore the urine will become more concentrated.

If the blood is too dilute the pituitary will release less ADH and so more water will leave the kidneys ( the urine will become dilute).

This is an example of negative feedback.

Triple Science 9-1 Biology Unit 5 Homeostasis and Response Part 2

The Kidneys make urine by taking waste products out of your blood. Substances are filtered out of the blood as it passes through the kidneys. This process is called filtration.

Useful substances, including glucose, ions and water are then absorbed back into the blood. This process is called selective reabsorption.

The substances that are removed from the body in urine include urea, excess ions and water.

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People who suffer from kidney failure may be treated by:

Organ transplant

Using kidney dialysis

Kidney transplants are also used for patients with kidney failure, these come with issues of rejection.

Triple Science 9-1 Biology Unit 5 Homeostasis and Response Part 2

In dialysis the partially permeable membrane allows things like ions and waste substances through but not big molecules like proteins.

The dialysis fluid has the same concentration of dissolved ions and glucose as healthy blood. This means useful ions and glucose won’t be lost during the process.

Water and Nitrogen Balance QUICK QUIZ:

1. What is the name of the process in the kidneys where useful substances are absorbed back into the blood?

2. Name two substances which are absorbed back into the blood3. Name three substances which should be present in urine of a healthy person4. List two ways water can be lost from the body5. Describe how ADH controls water levels on the hot day when you are dehydrated6. Explain how a kidney dialysis machine 7. Describe two problems with dialysis and two problems with kidney transplants

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Hormones in Human Reproduction

During puberty reproductive hormones cause secondary sex characteristics to develop.

Oestrogen

The main female reproductive hormone produced in the ovary. At puberty eggs begin to mature and one is released approximately every 28 days. This is

called ovulation.

Testosterone

The main male reproductive hormone produced by the testes Stimulates sperm production.

The menstrual cycle: 4 main hormones control the menstrual cycle

Follicle stimulating hormone (FSH) causes maturation of an egg in the ovary. Luteinising hormone (LH) stimulates the release of the egg. Oestrogen and progesterone are involved in maintaining the uterus lining.

Hormones in Human Reproduction QUICK QUIZ:

Triple Science 9-1 Biology Unit 5 Homeostasis and Response Part 2 5

1. What is the role of testosterone during puberty?2. What is the role of oestrogen during puberty?3. What are secondary sex characteristics?4. Which 4 hormones are involved in the control of the menstrual cycle5. Describe the function of each hormone involved in the menstrual cycle6. Why does the uterus lining thicken between days 4 18?7. Which day is the egg released during the menstrual cycle?

Contraception

Fertility can be controlled by a variety of hormonal and non-hormonal methods of contraception.

Oral contraceptives that contain hormones to inhibit FSH production so that no eggs mature

Injection, implant or skin patch of slow release progesterone to inhibit the maturation and release of eggs for a number of months or years

Barrier methods such as condoms and diaphragms which prevent the sperm reaching an egg

Intrauterine devices which prevent the implantation of an embryo or release a hormone Spermicidal agents which kill or disable sperm Abstaining from intercourse when an egg may be in the oviduct Surgical methods of male and female sterilisation.

When considering contraceptives people consider and compare different factors including:

Efficacy- How much it decreases the chance of pregnancy Personal- Does it need to be taken every day/ does it cause discomfort/ does it require

surgery e.c.t. Different people may have different preferences Economic- How much does it cost? Do you need to pay every time? Environmental-Does the method impact the environment? Religious- Does a religious text or leader ban their use? Social- How might reducing the number of pregnancies/ unwanted pregnancies affect

society as a whole?

The use of hormones to treat infertility

Triple Science 9-1 Biology Unit 5 Homeostasis and Response Part 2

Contraception QUICK QUIZ:

1. How do surgical methods prevent pregnancy?2. Name two barrier methods and explain how they prevent pregnancy3. Name all of the methods which use hormones to prevent pregnancy4. Explain how oral contraceptives prevent pregnancy5. What does efficacy of a contraceptive refer to?

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If someone is infertile they cannot conceive naturally. Luckily modern reproductive technologies can be used to treat infertility.

This normally includes giving FSH and LH in a ‘fertility drug’ to a woman. She may then become pregnant in the normal way. If this does not work, a couple may decide to try IVF

In Vitro Fertilisation (IVF) treatment

IVF involves giving a mother FSH and LH to stimulate the maturation and release of several eggs

The eggs are collected from the mother and fertilised by sperm from the father in the laboratory

The fertilised eggs develop into embryos At the stage when they are tiny balls of cells, one or two embryos are inserted into the

mother’s uterus (womb)

IVF is only possible because of development in microscopy which allow eggs to be fertilised ‘in vitro’ (‘outside of a living organism’)

Although fertility treatment gives a woman the chance to have a baby of her own:

It is very emotionally and physically stressful The success rates are not high It can lead to multiple births which are a risk to both the babies and the mother.

Negative FeedbackTriple Science 9-1 Biology Unit 5 Homeostasis and Response Part 2

Hormones to treat infertility QUICK QUIZ:

1. What does it mean if someone is infertile?2. Which two hormones are present in the ‘fertility drug’?3. How does the fertility drug increase the chance of conception?4. Describe the process of IVF in 4-5 steps5. List two advantages and three disadvantages of using IVF6. Why is microscopy needed for IVF?

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Negative feedback loops enable the body to maintain internal conditions (homeostasis).

Thyroxine is an example of a hormone which has an important role in growth and development because it increases the basal metabolic rate. Its levels are controlled by negative feedback:

Adrenaline:

Adrenaline is produced by the adrenal glands in times of fear or stress It increases the heart rate and boosts the delivery of oxygen and glucose to the brain and

muscles Preparing the body for flight or fight Its levels are controlled by negative feedback

Plant Hormones

Triple Science 9-1 Biology Unit 5 Homeostasis and Response Part 2

5.3.7 Negative feedback QUICK QUIZ:

1. Name two hormones whose concentrations are controlled via negative feedback

2. Why does the body use negative feedback?3. What is the function of thyroxine?4. What is the function of adrenaline?5. Which two glands can detect the level of thyroxine in the body?6. How does your body respond to thyroxine levels being too high?7. How does your body respond to thyroxine levels being too low?

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Use of plant hormones

Plant growth hormones are used in agriculture and horticulture.

Auxins are used:•As weed killers•As rooting powders•For promoting growth in tissue culture

Ethene is used in the food industry to control ripening of fruit during storage and transport.

Gibberellins can be used to:•End seed dormancy•Promote floweringIncrease fruit size

Triple Science 9-1 Biology Unit 5 Homeostasis and Response Part 2

Plants are sensitive to light, moisture and gravity. Plants produce hormones to coordinate and control:

Growth Responses to light (phototropism) - their shoots grow towards light and against the force

of gravity Responses to gravity (gravitropism) - their roots grow towards moisture and in the

direction of the force of gravity

Unequal distributions of auxin cause unequal growth rates in plant roots and shoots.

Gibberellins are important in initiating seed germination Ethene controls cell division and ripening of fruits.

Plant Hormones QUICK QUIZ

1. Name a plant hormone. 2. How does this hormone assist plant shoots to grow towards light? 3. What is this response called?

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Triple Science 9-1 Biology Unit 5 Homeostasis and Response Part 2

Plant Hormones QUICK QUIZ

1. Name a plant hormone. 2. How does this hormone assist plant shoots to grow towards light? 3. What is this response called?

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