The endocrine system consists of glands that produce hormones, chemical messengers released into the bloodstream. Hormones cause slow, long-term, and often irreversible changes related to growth and reproduction. Key glands include the pituitary, thyroid, pancreas, adrenals, ovaries, and testes, each releasing important hormones like growth hormone, thyroxine, insulin, estrogen, progesterone, and testosterone. The endocrine system differs from the nervous system in using chemical signals instead of electrical ones, causing generally slower but often irreversible changes throughout the body.

1. Year 9 Science
Strathcona BGGS

2. The Endocrine System
 Consists of glands that produce
chemicals that act as messengers or
signals. These chemicals are known as
hormones.
 Hormones are released into and carried
by the blood stream.
 Changes produced by hormones are
generally:
 Slow
 Long term
 Irreversible :Growth and Reproduction

3. Parts of the Endocrine System

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5. The Pituitary Gland
 Is sometime called the ‘Master
Gland’ as it regulates most
other endocrine glands.
 Releases hormones including:
 Growth Hormone (GH)
 Thyroid Stimulating
Hormone (TSH)

6. The Thyroid Gland
 Is responsible mainly for the
regulation of metabolic
rate.
 Major hormone:
 Thyroxine

7. The Islets of
Langerhans
 Are groups of cells in the pancreas
 Regulates blood sugar levels
 Releases hormones including:
 Insulin – lowers blood glucose levels
 Glucagon – raises BGL

9. The Adrenals  Located on top of the Kidneys
 Has two layers
 The outer Cortex
 Which releases
aldosterone and cortisol.
 The inner Medulla
 Releases adrenaline and
noradrenaline - key
hormones of the stress
response

10. The Ovaries
 Release the female sex hormones:
 Estrogen (Oestrogen)
 stimulates the development of
female secondary sexual
characteristics
 involved in monthly
preparation for pregnancy
 Progesterone
 stimulates the growth of
mammary glands
 prepares the uterus for
pregnancy

11. The Testes
 Secretes the male sex
Hormone:
 Testosterone
 very important in the
development of a male embryo.
 stimulates the development of
male secondary sexual
characteristics

12. The Nervous System v The Endocrine System
The Nervous System The Endocrine System
 Uses (mostly) Electrical  Uses Chemical Messages
Messages (Hormones)
 Fast Acting  Generally Slow Acting
 Reversible changes  Generally Irreversible changes
 Dedicated signal system  Uses Blood System to spread
(nerves) hormones