Hormones

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  • Created by: Leighanne
  • Created on: 25-03-13 12:16
Define the term endocrine gland
A ductless gland that secretes hormones directly into the blood
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Define the term exocrine gland
A gland that secretes molecules into a duct that carries the molecules to where they are used
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What is a first messenger
A molecule such as adrenaline which innitiates the response by activating another cell
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What is a secondary messenger
A chemical inside the cell released in response to a hormone binding to a cell surface membrane e.g. cAMP
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Define where protein and steroid hormones are made
Protein hormones are made in the adrenal medulla, Steroid hormones are made in the adrenal cortex of the adrenal gland.
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What do hormones target?
Target cells
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What is unusual about the pancreas?
It has both exocrine and endocrine functions
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Where are enzymes made in the pancreas secreted?
The pancreatic duct, it carries the fluid containing the enzymes into the first part of the small intestine
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What enzymes does the pancreatic fluid contain?
Amylase, Lipase, tripsinoge (an inactive protease) and sodium hydrocarbonate to neutralise stomach acid
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What are the Islets of Langerhans?
They are a small patch of tissue in the pancreas that have an endocrine function
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What are the two cells found in the Islets of langerhans?
Alpha cells, which secrete glucagon when blood glucose is too low. Beta cells, which secrete insulin when blood glucose levels are too high
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What occurs if blood glucose levels raise too high?
The stages: Glucose is detected by the Beta cells in the islets of langerhans, this secretes insulin (the target cells are brain, muslce and liver/hepatocytes) Insulinis a first messenger which leads to the activation of adenly cyclase
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What affects does insulin have on cells?
1. causes glucose transporter proteins (GLUT4) to be added to the surface membrane, this causes more glucose to enter the cell. 2. Glucose is converted into glycogen (glycogenesis) 3. More glucose is used in respiration and some is converted to fats
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What occurs when blood glucose drops too low?
BVlood glucose concentration is detected by the alpha cells in the islets of langerhans, the targets cells are hepatocytes which posses the specific receptor for glucagon
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what are the effects of glucagon?
1. Conversion of glycogen to glucose (glycogenolysis) 2. More fatty acids are used in respiration 3. Glucose is amde out of amino acids and fats (gluconeogenesis)
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Which membranes do the Beta cells in the Islets of Langerhans contain, and which ones are open?
The beta cells contain calcium ion channels and potassium ion channels, Potassium ion channels are always open (until extra ATP is found in the cell) Calcium channels are normally close but open when potassium ion channels close as the p.d. increases
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What is the potential difference of the beta cell initially?
around -70mV
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What happens when glucose molecules diffuse into the beta cells?
Glucose is quickly used in metabolism to produce ATP, this causes an icnrease in ATP which causes potassium ion channles to close
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How does insulin leave the beta cells?
Calcium diffuses into the beta cells, causing vesicles containing insulin to leave the beta cell via exocytosis
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What is diabetes mellitus?
A disease in which blood glucose concetrations cannot be controlled efficiently
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What is hypoglycaemia
When blood glucose concentrations are too low (usually after exercise or fasting)
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What is hyperglycaemia?
When blood glucose concentrations are too high (after a meal rich in sugars and other carbohydrates)
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What is type 1 diabetes?
Where your body is unable to produce insulin or store glucose as glycogen. It is an autoimmune disease as the body's own immune systems attacks the beta cells
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What age does diabetes type 1 occur and what is the cause?
Diabetes type 1 occurs in childhood, it is said to be herditary, but it has found to be result of bad cases of childhood viral infections such as measels and mumphs
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What is type 2 diabetes?
Known as non insulin dependent diabetes. This where the body doesn't respond to insulin as receptors on the sruface of the liver and muscle cells decline, loosing their ability to respond to insulin Insulin levels secreted by beta cells may also drop
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What age does diabetes type 2 occur and what is the cause?
It normally opccurs in later adulthood, it can be due to obesity, diets high in sugar or fats, being asian or afro carribbean, male, lack of exercise or excessive alcohol.
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Treatment of type 1 diabetes includes:
Insulin injections into the blood (cannot be taken as a tablet as it would be digested)
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Treatment of type 2 diabetes includes:
Careful monitoring of the diet, which may eventually be supplemented with insulin injections
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Source of insulin is from?
Bacteria that have been gentically engineered to produce insulin, there is talk of using stem cells to help create beta cells in pateints with type 1 diabetes
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How is heart rate controlled?
The heart is myogenic, it contains its own pace maker, the SAN in the atrial wall. The heart is connected to the medulla oblongata of the brain via the acceleratore nerve and vagus nerve.The heart also responds to adrenaline
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Where is the frequency of contractions of the heart regulated?
In the cardiovascular centre of the medulla oblongata
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How can movement of limbs affect hear rate?
Movement is detected by stretch receptors in the muslces, these send impulses to the cardivascular centre in the M.O. informing it that more oxygen is required, increasinf heart rate
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How can exercise (production of co2) affect heart rate?
Exercise causes the release of Co2, this reacts with water in the blood plasma to release hydrogen ions which decrease the blood pH. Chemoreceptors detect the acidity of the blood and send impuilses to the brain to increase heart rate
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What happens when we stop exercising?
Concentration of co2 reduce this reduces the activity of the accelerator pathway, therefore heart rate decreases
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What affect does adrenaline have on heart rate
Adrenaline is realeased in response to stress it is released from the adrenal medulla and binds to adrenergic receptors on the cardiac muscle causing heart rate to increase
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How does blood pressure affect heart rate
Stretch recpetorsin the walls of the carotid sinsu sends signals to the cardiovascular centre, if blood pressure is too high heart rate reduces
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Card 2

Front

Define the term exocrine gland

Back

A gland that secretes molecules into a duct that carries the molecules to where they are used

Card 3

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What is a first messenger

Back

Preview of the front of card 3

Card 4

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What is a secondary messenger

Back

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Card 5

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Define where protein and steroid hormones are made

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