Coordination And Control: Mammalian Hormones
14.3 Mammalian Hormones
What Are Hormones?
- Chemical substances, produced by endocrine glands, carried by blood.
- Alter activity of specific target organs.
- Slower but longer-lasting than nervous impulses.
Endocrine Glands And Hormones
| Gland | Hormone | Function |
|---|---|---|
| Adrenal glands | Adrenaline | Prepares body for “fight or flight” (↑ heart rate, ↑ blood glucose) |
| Pancreas | Insulin | Lowers blood glucose (stores glucose as glycogen) |
| Pancreas | Glucagon | Raises blood glucose (breakdown of glycogen) |
| Pituitary gland | FSH | Stimulates egg development and oestrogen secretion |
| Pituitary gland | LH | Stimulates ovulation and progesterone secretion |
| Testes | Testosterone | Male secondary sexual characteristics |
| Ovaries | Oestrogen | Female secondary sexual characteristics |
| Ovaries | Progesterone | Maintains pregnancy, uterine lining |
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Adrenaline Effects
- Increases heart rate and breathing rate.
- Increases blood glucose concentration.
- Diverts blood to muscles.
- Prepares body for emergency situations.
Nervous vs Hormonal Control
| Feature | Nervous Control | Hormonal Control |
|---|---|---|
| Speed | Very fast | Slower |
| Duration | Short-lived | Longer-lasting |
| Transmission | Electrical impulses in neurones | Chemical in blood |
| Example | Reflex action | Adrenaline, insulin |
Written And Compiled By Sir Hunain Zia, World Record Holder With 154 Total A Grades, 7 Distinctions And 11 World Records For Educate A Change O Level And IGCSE Biology Full Scale Course