F214 OCR Biology: Hormones

F214 OCR Biology: 

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  • Created on: 15-06-11 11:23
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Hormones Summary
Endocrine ­ product is secreted directly into the blood or lymph
Exocrine ­ product is carried by a duct to it's site of action
Hormone ­ the product of an endocrine gland
Target tissue ­ the tisues in which the hormone has an effect
First and Second Messenger (using adrenaline as an example)
1. The hormone released by the endocrine gland is the first messenger
2. Protein hormones and adrenaline do not enter the target cells
3. This starts a series of reactions within the cell, involving a second messenger
4. The second messenger of adrenaline is cyclic AMP (cAMP)
5. Adrenaline binds to a glycoprotein receptor on the plasma membrane
6. Adenyl cyclase is activated and more cAMP is made
7. cAMP activates an enzyme controlled metabolic pathway
Adrenal Glands
Part of adrenal gland Hormone Target tissue Role
Adrenal cortex Glucocorticoids Liver Stimulates synthesis
of glycogen
Mineralocorticoids Kidney and gut Increased uptake of
Na+ & rise in blood
Adrenal medulla Adrenaline Heart Increased heart rate
Liver Stimulates breakdown
Smooth muscle of gut of glycogen to glucose
Inhibits peristalsis
The control of plasma glucose concentration
1. The concentration of glucose in the blood plasma is closely controlled.
2. The normal range is between 4 ­ 9 mmoll-1
3. The Pancreas is fundamental to controlling plasma glucose concentration
4. Within the Pancreas are patches of endocrine tissue, called Islets of Langerhans
5. These contain two types of cells alpha and beta
6. Alpha cells secrete glucagon
7. Glucagon raises plasma glucose
8. Beta cells secrete insulin
9. Insulin lowers plasma glucose

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What happens when plasma glucose concentration is raised
(eg by eating a meal)
1. Both alpha & beta cells detect the rise in plasma glucose
2. Alpha cells respond by secreting less glucagon
3. Beta cells respond by secreting more insulin
4. Insulin binds to receptors in the plasma membranes of
muscle, fat and liver cells
5. Insulin makes the membranes of these cells more
permeable to glucose
6. Vesicles carry glucose channels to the membranes of
these cells
7.…read more

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Sources of insulin
1. Insulin can be obtained from cows, sheep and pigs
2. An alternative is human-sequence insulin
3. Bacteria are genetically modified
4. By inserting the gene for human insulin into the bacteria
5.…read more


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