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