1. Year 13 Biology Homeostasis
Hormonal Control
Year 13 Biology
Homeostasis

2. Hormone Signalling Forms part of the endocrine system
Uses chemicals in the blood to carry signals to the target tissue (organs/glands/cells)
Hormones are secreted by glands (that do not contain a duct) and each gland secretes a specific hormone
Small proteins – insulin
Steroids – testosterone, oestrogen
Amino Acids – thyroxine, adrenaline

3. Examples of glands and the hormones they produce
Pancreatic gland – secretes insulin (controls blood sugar)
Pituitary gland – secretes ADH (anti-diuretic hormone) (controls osmotic balance)
Thyroid gland – secretes thyroxine (controls metabolic rate)
Adrenal glands – secretes adrenalin, noradrenaline and aldosterone (controls blood pressure)

4. The Pituitary gland Known as the ‘Master gland’
It is the size of a pea and is located directly under the brain
Produces its own hormones (ADH) and hormones that control the activity of other endocrine glands
eg FSH (controls prodn of oestrogen and progesterone in ovaries)
TSH (controls prodn of thyroxine by thyroid)

5. The Hypothalamus
Has receptors for monitoring the level of many substances in the blood
Acts as the control centre for many homeostatic functions (eg body temperature, osmotic balance)
The hypothalamus integrates the action of all homeostatic mechanisms

6. Main Glands

7. Receptors For hormones to work
the target cell must have a receptor specific for the hormone on the outside of the cell

8. Nervous System vs. Hormones
Quick acting
Short lived response
Specific part of the body
Slow acting
Long duration responses
Widespread
More than one hormone can influence individual cells
Can work together to regulate the size of the response
Need to break down the hormone on completion