OCR A2 Biology: The Hormonal System

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A-Level Biology Karteikarten am OCR A2 Biology: The Hormonal System, erstellt von hannawin98 am 16/05/2016.
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What is the Hormonal System? The system in which information is sent via chemicals
What are endocrine glands? Groups of cells that are specialised to secrete hormones directly in the blood
What are hormones? 1. "Chemical messengers" 2. usually proteins, e.g insulin, or steroids, e.g progesterone
When are hormones secreted? When an endocrine gland is stimulated, either by the change in concentration of a specific substance or by electrical impulses
Outline hormonal communication 1. Hormones diffuse into the blood 2. They bind to specific receptors on target cells 3. This triggers a response in the target cells.
What are exocrine glands? Groups of sepcialised cells that secrete chemicals through ducts into cavities or onto the surface of the body
What is a first messenger? A chemical involved in cell signalling that binds to a receptor in a cell membrane and triggers activity inside the cell.
What is a second messenger? A chemical produced inside a cell in response to a signal outside the cell. The chemical relays the signal to the inside of the cell
What happens when a hormone binds to a receptor on the target cell? An enzyme is activated in the cell membrane. This enzyme catalyses the production of the second messenger which activates a cascade of reactions inside the cell.
What is adrenaline? A hormone that is secreted from the adrenal glands. It is secreted when there's a low glucose concentration in your blood when you are stressed or exercising.
What does adrenaline do? Makes your body ready for action by making more glucose available for muscles to respire, e.g by activating glycogenolysis
What happens when adrenaline binds to it's target cell? An enzyme called Adenylate cyclase is activated. This catalyses the production of Cyclic AMP (cAMP) which causes a cascade of reactions that make glucose more available to the cell.
What are the adrenal glands? Endocrine glands that are found above the kidney. They have an outer part called the cortex and the inner part called the medulla.
What does the cortex do? Secretes steroid hormones when you're stressed e.g glucocorticoids
What does the medulla do? Secretes catecholamine hormones (modified amino acids) when you're stressed e.g adrenaline
What is the Pancreas? An endocrine and exocrine gland found below the stomach
What are Islets of Langerhans? Endocrine tissue in the pancreas. They're found in clusters by blood capillaries and are made up of Alpha and beta cells.
What do alpha cells do? They secrete glucagon to raise blood glucose concentration levels
What do beta cells do? They secrete insulin to lower blood glucose concentration levels
What are acinar cells? Exocrine cells in the pancreas. They're found in clusters by the pancreatic duct. They secrete digestive enzymes into the small intestine via the pancreatic duct.
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