4.1.3 HORMONES

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What is a hormone?
a molecule released into the blood which acts as a chemical messenger
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what is an endocrine gland?
a gland that secrets hormones directly into the blood// has no ducts
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What is an exocrine gland?
a gland that secretes hormones/molecules into a duct that carries the molecules to where they are needed
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what is a target tissue?
a group of cells that have receptors embedded in their plasma membrane that have complementary shapes to specific hormone molecules // only these cells will respond to the specific hormone
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What is meant by the first messenger?
the hormone that transmits the message around the body
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What is meant by the second messenger?
transmits a signal within a cell
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Describe the function of adrenaline as a first messenger
interacts with receptors on cell surface mem of target cells// unable to enter cells as it is an amino acid derivative
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What happens when adrenaline binds to target cells?
activates enzyme Adenyl Cyclase - converts ATP into cyclic AMP (cAMP) // cAMP is the secondary messenger// cAMP causes multiple of enzyme controlled reactions within the cell which produces the wanted responses which the 1st messenger wanted
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Where are the Adrenal glands found?
just above the kidneys
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What is the adrenal medulla?
central part of gland that releases adrenaline
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What responses does adrenaline cause?
relaxes smooth muscle // increases stroke vol and heart rate// vasoconstriction to raise blood pressure // stimulates conversion of glycogen to glucose // dilates pupil so more can be seen // increased mental awareness// inhibits action of the gut
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What is the adrenal cortex?
uses cholesterol to produce steroid hormones// hormones that regulate aspects of the metabolism and ion uptake in the kidney// help control conc of Na and K in the blood // help control metabolism of carbs and proteins in the lover (cortisol)
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Where is the pancreas?
lies below the stomach
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what is the function of the pancreas?
acts as both an exo and endocrine gland
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Describe the exocrine function of the pancreas
secrete digestive enzymes into the pancreatic duct which empties into the duodenum // amylase etc. // also contains sodium hydrogen carbonate to ensure contents from stomach are alkaline when in intestine
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Describe the endocrine function of the pancreas
called the islets of langerhans // alpha secrete glucagon (raises blood glucose) // beta secrete insulin (lowers blood glucose) // well supplied with blood capillaries
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What happens when the blood glucose concentration drops too low?
detected by Islets of Langerhans alpha cells // inhibits insulin production // glycogenolysis and gluconeogeniesis
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What is glycogenolysis?
conversion of glycogen to glucose
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What is gluconeogenesis?
more fatty acids used is respiration// glucose produced by conversion of amino acids and fats
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What happens when blood glucose rises too high?
beta cells detect // inhibit glucagon // secrete insulin into blood // insulin binds to hepatocytes in liver // activates adenyl cyclase in cell // converts ATP to cAMP -
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what is the role of cAMP in blood glucose concentration control?
secondary messenger to insulin in liver cells/ causes a series of enzyme catalysed reactions - more glucose channels in cell surface mem/ more glucose enters the cells // glycogenesis // more glucose converse into fat// more glucose used in respirayi
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what is glycogenesis?
conversion of glucose to glycogen
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Describe the control of insulin secretion
...
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what is diabetes mellitus?
disease in which the homeostatic control of blood glucose fails
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what is hyperglycaemia?
conc of blood glucose too high
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what is hypoglycaemia?
conc of blood glucose too low
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Describe type 1 diabetes
insulin dependent, onset // result of autoimmune response when bodys immune system attacks beta cells// insulin injections
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Describe type 2 diabetes
non insulin dependent// insulin can still be produced but body loses its responsiveness to insulin as receptors in liver declines
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What factors affect type 2 diabetes?
obesity levels// diet in high refined sugars// family history // being asian or afro caribbean
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How is type 2 diabetes treated?
monitor glucose levels and diet
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How can insulin be produced for diabetics?
genetically modified bacteria// animal insulin // stem cell treatment
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describe the production of insulin from genetically modified bacteria
exact copy of human insulin, fast acting and effective // less chance of developing a tolerance// less chance of rejection// cheaper// less likely to have moral objections
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describe the production of insulin from animal cells
cheapest // less pure // ethical problems
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how can stem cells be used in the treatment of insulin?
produce new beta cells // stem cells from the pancreas of adult mice // rejection by immune system could be a problem
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why must insulin be injected?
if taken by mouth - as it is a protein it would be digested
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How is the heart rate controlled by nervous mechanisms?
action potentials are sent down the accelerator nerve to the heart, from the cardiovascular centre in the medulla oblongata
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Why would the heart rate need to be increased by the nervous mechanism?
movement of limbs detected by stretch receptors in muscles// drop in pH detected by chemoreceptors in the carotid arteries aorta and brain
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Why would the heart rate need to be decreased by the nervous mechanism?
increase in blood pressure when conc of CO2 falls reduces activity of accelerator nerve
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How is the pH of the blood reduced?
during exercise // CO2 + H2O ---> H2CO3 dissociates into H+ ions
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Outline the hormonal mechanism that controls the heart rate
adrenaline secreted as a response to stress // stress can be threat, anticipation, excitement // adrenaline binds to specific complementary receptors on the heart
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Card 2

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what is an endocrine gland?

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a gland that secrets hormones directly into the blood// has no ducts

Card 3

Front

What is an exocrine gland?

Back

Preview of the front of card 3

Card 4

Front

what is a target tissue?

Back

Preview of the front of card 4

Card 5

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What is meant by the first messenger?

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