1. The Endocrine System

2. Endocrine vs exocrine glands
Endocrine glands produce and secrete hormones into the bloodstream
eg. the pituitary gland
Exocrine glands secrete through ducts
eg. salivary glands

3. Hormones
Hormones – chemical signals released by specialized cells of the body to exert an effect on cells in other parts of the body
There are 2 classes of hormones:
Steroid hormones
derived from cholesterol
multi-aromatic structure
lipid soluble

4. Steroid hormones Mode of action:
Diffuse through cell membrane of cells (phospholipid soluble)
Combine intercellularly with receptor molecule
Initiates transcription of specific gene(s)
Effect achieved by resulting protein(s)

5. Hormones
Hormones – chemical signals released by specialized cells of the body to exert an effect on cells in other parts of the body
There are 2 classes of hormones:
Protein hormones
made of amino acids
water soluble
Insulin
Parathyroid hormone
Growth hormone

6. Protein hormones Mode of action:
Attach to specific membrane receptors (hormone acts as ‘first messenger’)
Signal transduction results in intercellular molecule activation (molecule is ‘second messenger’)
Molecule up/down regulates protein activity within cell
Effect is achieved by activated proteins

7. Glands of the endocrine system
Pituitary gland
Attached to the hypothalamus
Two-lobed (anterior & posterior)
Each lobe releases different hormones
Posterior pituitary
Stores/release hypothalamus-made hormones eg. antidiuretic hormone, ADH, oxytocin
Anterior pituitary
Makes its own hormones but release is controlled by hypothalamus eg. growth hormone, follicle-stimulating hormone, luteinizing hormone

8. Glands of the endocrine system
Pancreas
Small gland containing endocrine & exocrine cells
Endocrine tissue called islets of Langerhans and contains 2 types of cells:
-cells produce insulin
released when blood sugar is high
causes muscle, liver and other organs to take up glucose (reducing blood sugar)
-cells produce glucagon
released when blood sugar is low
causes glycogen in aforementioned tissues/organs to be converted to glucose (raising blood sugar)

9. Glands of the endocrine system
Adrenal glands
Located above each kidney
Consists of adrenal medulla and adrenal cortex
Medulla
Regulated by nervous system
Makes adrenaline (epinephrine) & noradrenaline (norepinephrine)
Sypathetic nerves cause release of both hormones
Causes conversion of glycogen to glucose & ups heart rate, breathing rate, etc.
Cortex
Produces sex hormones and hormones involved in stress conditions (eg. cortisol) and water reabsorption (eg. aldosterone)

10. Glands of the endocrine system
Thyroid/parathyroid glands
Located in neck
‘Thyroid hormones’ effect growth & specific rates of function within the body (eg. calcitonin regulates bone-calcium homeostasis)
Ovaries
Located in lower abdomen of females
Produce estrogen and progesterone which regulate reproductive health (eg. the menstrual cycle)
Testes
Located in the scrotum of males
Produce testosterone which maintains libido, muscle strength and bone density

11. Nervous + Endocrine = Endocrine pathway
There are 3 main pathways of hormonal control:
Endocrine pathway
Stimulus
Endocrine gland
Blood vessel
Target
Response

12. Nervous + Endocrine = Neurohormone pathway
There are 3 main pathways of hormonal control:
Neurohormone pathway
Stimulus
Hypothalamus
Blood vessel
Target
Response

13. Nervous + Endocrine = Neuroendocrine pathway
There are 3 main pathways of hormonal control:
Neuroendocrine pathway
Stimulus
Hypothalamus
Blood vessel
Endocrine gland
Target
Response

14. Try this…
Read pg. 938 Section 46.5