A2 OCR Biology Key Terms and Definitions Hormones

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Endocrine System
The body organs that secrete hormones.
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Endocrine Gland
An organ that secretes hormones directly into the blood.
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Hormone
A chemical secreted by an endocrine gland, which brings about a response in an organ elsewhere in the body.
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Target Tissue
A group of cells that contain receptors for a particular hormone and are therefore affected by it.
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Secretion
The production and release of a useful substance from a cell.
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Duct
A tube leading from one part of the body to another.
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Adrenaline (Epinephrine)
A catecholamine hormone, secreted by the adrenal glands in times of stress, fear or excitement, and which prepares the body for fight or flight.
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Adrenal Glands
Endocrine glands situated just above the kidneys, which secrete adrenaline.
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G-Protein
A protein inside the plasma membrane of a cell, which is affected by the binding of a signal molecule with a receptor in the plasma membrane.
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Adenylyl Cyclase
An enzyme that produces cAMP in the cytoplasm, in response to the binding of a signal molecule with the plasma membrane.
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Cyclic AMP (cAMP)
A second messenger produced as a result of adrenaline binding with a receptor in the plasma membrane; it is also produced as a result of many other interactions between signal molecules and their receptors.
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Protein Kinase
An enzyme involved in some cell signalling pathways.
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Glycogen Phosphorylase Kinase
An enzyme found in liver cells that activates glycogen phosphorylase.
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Glycogen Phosphorylase
An enzyme found in liver cells that breaks down glycogen to glucose.
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First Messenger
A molecule that binds to a receptor in the plasma membrane and causes changes to happen in the cell; adrenaline is an example of a first messenger.
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Second Messenger
A molecule that is affected by the binding of a first messenger to a receptor; cAMP is an example of a second messenger.
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Pancreatic Juice
A digestive secretion produced by the pancreas; it contains several digestive enzymes that act in the duodenum (part of the small intestine that neutralises your stomach acid).
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Alpha Cells
Cells in the islets of Langerhans that secrete glucagon.
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Beta Cells
Cells in the islets of Langerhans that secrete insulin.
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Islets of Langerhans
Groups of cells in the pancreas that secrete insulin and glucagon.
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Glucagon
A hormone secreted in response to low blood glucose levels, which brings about an increase in the rate of production of glucose from glycogen and other substances in the liver.
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Insulin
A hormone secreted in response to high blood glucose levels, which brings about an increase in the uptake of glucose from the blood and its conversion to glycogen.
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Glucokinase
An enzyme that adds a phosphate group to a glucose molecule.
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Gluconeogenesis
The production of glucose from non-carbohydrate substances, such as amino acids or lipids.
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Type 1 Diabetes
Insulin-dependent diabetes begins at a very early age. The pancreas appears to be incapable of secreting enough insulin, so the blood glucose levels may soar after a carbohydrate-containing meal.
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Type 2 Diabetes
Non-insulin-dependent diabetes typically begins later in life. The pancreas does secrete insulin, but the liver and other target organs do not respond to it adequately.
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Diabetes Mellitus
A condition in which blood glucose levels are not fully controlled; in Type 1, insulin is not secreted, while in Type 2 insulin is secreted but has little effect on the target tissues.
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Hyperglycaemia
Having a blood glucose level that is too high.
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Ketoacidosis
A dangerous condition caused by the presence of ketone bodies in the blood.
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Hypoglycaemia
Having a blood glucose level that is too low.
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GM Insulin
Insulin produced by genetically modified bacteria.
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Stem Cell Therapy
Using stem cells to treat or cure a disease.
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Vagus Nerve
A nerve running from the brain to many internal organs; it is part of the parasympathetic nervous system and slows heart rate when it carries impulses to the SAN.
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Parasympathetic Nerve
A nerve that is part of the parasympathetic system; stimulation of the SAN by the parasympathetic nerve decreases heart rate.
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Sympathetic Nerve
A nerve that is part of the sympathetic system; stimulation of the SAN by the sympathetic nerve impulses heart rate.
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Card 2

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An organ that secretes hormones directly into the blood.

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Endocrine Gland

Card 3

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A chemical secreted by an endocrine gland, which brings about a response in an organ elsewhere in the body.

Back

Preview of the back of card 3

Card 4

Front

A group of cells that contain receptors for a particular hormone and are therefore affected by it.

Back

Preview of the back of card 4

Card 5

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The production and release of a useful substance from a cell.

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