Hormones

The endocrine system

Endocrine glands

Blood glucose regulation

Contents

Summary quiz

What exactly are hormones?

What effect do hormones have on the body?

Hormones and the endocrine system

To understand hormones you need to know about the endocrine system and how it works.

The endocrine system co-ordinates the body’s organs so they work together.

The endocrine system is based on the production of chemical messengers called hormones.

Hormones are produced by glands (endocrine glands) in different parts of the body. These chemical messengers produced in very small quantities and transported in the blood.

The endocrine system

Hormones control body processes that require several organs of the body to interact for a combined effect.

What do hormones do?

Hormones travel slower than nervous impulses but cause longer lasting effects.

Over or under activity of some endocrine glands can cause functional disorders such as diabetes.

They are delivered to all parts of the body but can have local effects.

Hormones are used to stabilise the body’s internal environment through homeostasis and also co-ordinate longer term processes such as growth and sexual development.

Which body system?

The endocrine system

Contents

Endocrine glands

Blood glucose regulation

Hormones

Summary quiz

Produces the hormone thyroxine:

Regulates rate of metabolism.

Excess causes hyperactivity.

Deficiency causes overweight and sluggishness.

Endocrine glands – thyroid

thyroid

Endocrine glands – adrenal glands

adrenal glands

Produce the hormone adrenaline.

Adrenaline causes the ‘fight or flight’ response resulting in:

Increased heart rate and breathing rate.

Blood diverted to the muscles.

Increased respiration to increase the amount of glucose in the blood.

ovaries

Endocrine glands – reproductive organs

In females, ovaries produce several hormones:

oestrogen Controls the development of female

secondary sexual characteristics.

Regulates menstrual cycle,

progesterone Thickens uterine wall.

Prevents contractions until a baby is being born.

testes

Endocrine glands – reproductive organs

In males, testes produce the hormone testosterone:

Promotes the development of male secondary sexual characteristics.

Endocrine glands – pancreas

pancreas

Produces the hormone insulin:

Controls the conversion of blood glucose to insoluble glycogen, which is stored in the liver.

Increases metabolic rate by stimulating cellular glucose uptake.

Increases protein synthesis in some cells.

Deficiency causes the condition “sugar diabetes”, where the blood sugar level is unregulated.

Produces the hormone glucagon:

Controls the conversion of insoluble glycogen to glucose in the liver.

Endocrine glands – pancreas

pancreas

pituitary gland

Produces several hormones:

growth hormone Promotes bone and muscular

growth.

antidiuretic hormone (ADH) Controls reabsorption of water into

the blood by kidneys.

thyroid stimulating hormone (TSH) Controls the endocrine function of

the thyroid gland.

Endocrine glands – pituitary gland

pituitary gland

Produces several specific hormones in females:

follicle stimulating hormone (FSH) Causes the follicle in the ovary to

develop and secrete oestrogen.

leutenising hormone (LH) With FSH and other hormones

causes ovulation.

Endocrine glands – pituitary gland

Name that gland

Match hormones to glands

The endocrine system

Contents

Endocrine glands

Blood glucose regulation

Hormones

Summary quiz

Some hormones affect only one target organ, but most affect more than one.

When the hormone has had the desired effect, further production of the hormone needs to be controlled.

Hormone production is controlled by a process called negative feedback.

The regulation of blood glucose level is an example of negative feedback.

Negative feedback

and the liver are all involved in regulating blood glucose.The brain, the pancreas

Negative feedback – blood glucose

Which of these parts of the body are involved in the negative feedback process that regulates blood glucose?

Negative feedback – high blood glucose

The brain detects the level of glucose in the blood.

When the level of blood glucose increases above normal, what hormone does the pancreas release?

increased blood glucose

Negative feedback – high blood glucose

The pancreas is stimulated to release insulin. What effect does this have?

The insulin stimulates the liver to take glucose from the blood and convert into glycogen, which is stored in the liver.

insulinincreased blood glucose

The level of glucose in the blood decreases, causing the pancreas to stop producing insulin.

What would happen if the pancreas kept on producing insulin?

blood glucose returns to normal

Negative feedback – high blood glucose

increased blood glucose insulin

Negative feedback also occurs when the blood glucose level decreases below normal.

This time the brain detects and the pancreas is stimulated to release which hormone?

Negative feedback – low blood glucose

decreased blood glucose

The pancreas produces the hormone glucagon.

Glucagon stimulates the liver to convert glycogen back to glucose and release this glucose into the bloodstream.

Negative feedback – low blood glucose

decreased blood glucose glucagon

The level of glucose in the blood increases, causing the pancreas to stop producing glucagon.

What would happen if the pancreas kept on producing glucagon?

Negative feedback – low blood glucose

decreased blood glucose

blood glucose returns to normal

glucagon

Blood glucose activity

When hormones go wrong – Diabetes

What happens if the pancreas is unable to produce the hormone insulin?

After a person with diabetes has eaten, their blood glucose level increases. What happens to this glucose?

The absence of insulin means that glucose is not converted to glycogen and stored in the liver, so the blood of a

Lack of insulin production means that the blood glucose level is unregulated and causes the condition known as “sugar diabetes”.

diabetic contains extra glucose.

When hormones go wrong – Diabetes

Glucose is essential for the body so why is excess glucose a danger for people with diabetes?

When the glucose is used up, coma and convulsions may occur. So how is diabetes controlled?

Regular insulin injections and a careful diet can control the condition.

The ability of the kidneys to absorb glucose is also exceeded, so the excess is excreted in urine.

The endocrine system

Contents

Endocrine glands

Blood glucose regulation

Hormones

Summary quiz

Multiple-choice quiz