OCR F214 Hormones

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F214 Module 1: Communication and Homeostasis
4.1.3 Hormones
(a) define the terms:
Endocrine A gland that secretes hormones directly into the blood capillaries running through the gland's
gland tissue. Endocrine glands have no ducts
Exocrine A gland that secretes useful molecules, e.g. saliva from the salivary gland, into a duct that
gland carries the molecules to where they are used.
Hormone Molecules that released by the endocrine glands directly into the blood. They act as
messengers, carrying a signal from the endocrine gland to a specific target organ or tissue.
Target Tissue A group of similar cells that possess the specific receptor on their cell surface membrane. The
shape of the receptor is complementary to the shape of the hormone molecule.
(b) explain the meaning of the terms first messenger and second messenger, with reference to adrenaline and
cyclic AMP (cAMP)
First messenger the hormone that transmits a signal around the body .
Second messenger molecules called cAMP that transmits a signal inside the cell.
Adrenaline:
The adrenaline receptor on the outside of the cell surface membrane has
a shape complementary to the shape of the adrenaline molecule. The
receptor is associated with an enzyme on the inner surface of the cell
surface membrane. The enzyme is called adenyl cyclase .
1. Adrenaline in the blood binds to its specific and complementary
receptor on the cell surface membrane. The adrenaline molecule is the
first messenger .
2. When it binds to the receptor is activates the enzyme adenyl cyclase ,
which converts ATP to cyclic AMP (cAMP a second messenger).
3. The cAMP can then cause an effect inside the cell by activating enzyme
action .
(c) describe the functions of the adrenal glands
The adrenal glands are found lying just above the kidneys one of each side of the body. Each gland can be
divided into a medulla region and a cortex region.
Adrenal Medulla Adrenal Cortex
The medulla is found in the centre of the The cortex uses cholesterol
gland. The cells in the medulla manufacture to produce certain steroid
and release the hormone adrenaline in hormones . These have a
response to stress such as pain or shock. The variety of roles in the body.
effect of adrenaline is to prepare the body The
for activity. This includes: mineralocorticoids
Relax smooth muscle in the (e.g. aldosterone )
bronchioles. help to control the
Increase stroke volume of the heart. concentrations of
Increase heart rate. sodium and
Cause general vasoconstriction to raise potassium in the
blood pressure. blood.
Stimulate conversion of glycogen to The glucocorticoids
glucose. (e.g. cortisol ) help to
Dilate the pupils. control the
Increase mental awareness. metabolism of
Inhibit the action of the gut. carbohydrates and
Cause body hair to erect. proteins in the liver .

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F214 Module 1: Communication and Homeostasis
(d) describe, with the aid of diagrams and photographs, the histology of the pancreas, and outline its role as an
endocrine and exocrine gland
The pancreas is a small organ lying below and behind the stomach. It is an unusual organ in that it has both
exocrine and endocrine functions.
Exocrine Functions Endocrine Functions
The majority of the cells in the pancreas manufacture Certain areas of the pancreas called the islets of
and release digestive enzymes.…read more

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F214 Module 1: Communication and Homeostasis
(e) explain how blood glucose concentration is regulated, with reference to insulin, glucagon and the liver
The cells in the islets of Langerhans monitor the concentration of glucose in the blood. The normal concentration
of glucose is 80120mg per 100cm3 of blood, or 46 mmol dm3 .
Blood glucose too high Blood glucose too low
High levels of blood glucose is a problem because: Low levels of blood glucose is a problem because:
Creates a low of the plasma.…read more

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F214 Module 1: Communication and Homeostasis
(g) compare and contrast the causes of Type 1 (insulindependent) and Type 2 (noninsulindependent) diabetes
mellitus
Diabetes mellitus a disease in which blood glucose concentrations cannot be controlled effectively, by the
body.
Hyperglycaemia the state in which the blood glucose concentration is too high (hyper = above, glyc = gucose,
aenmia = blood).
Hypoglycaemia the state in which the blood glucose concentration is too low (hypo = under).…read more

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F214 Module 1: Communication and Homeostasis
Type II diabetes is treated by careful monitoring and control of the diet. Care is taken to match carbohydrate
intake and use. This may eventually be supplemented by insulin injection or use of other drugs which slow down
the absorption of glucose from the digestive system.
(i) outline the hormonal and nervous mechanisms involved in the control of heart rate in humans
The heart pumps blood around the circulatory system.…read more

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