Unit 1, Module 1 - Communication and Homeostasis Definitions

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Stimulus
Any change in the environment that causes a response.
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Response
A change in behaviour or physiology as a result of a change in the environment.
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Homeostasis
The maintenance of a constant internal environment, despite external changes.
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Negative feedback
A process that brings about a reversal of any change in conditions, ensuring an optimum steady state is maintained. It is essential for homeostasis.
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Positive feedback
A process that increases any change detected by the receptors. It tends to be harmful and does not lead to homeostasis.
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Ectotherm
An organism that relies on external sources of heat in order to regulate its body temperature.
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Endotherm
An organism that can use internal sources of heat in order to maintain its body temperature. Eg, heat generated from metabolism in the liver.
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Neurotransmitter
A chemical that diffuses across the cleft of the synapse to transmit a signal to the postsynaptic neurone.
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Cholinergic synapses
Those that use acetylcholine as their neurotransmitter substance.
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All or nothing
Refers to the fact that a neurone conducts an action potential or it does not. All action potentials are of the magnitude +40mV, an a threshold potential has to be reached for the action potential to be transmitted.
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Hormone
Molecules that are released by endocrine glands directly into the blood. They act as messengers, carrying a signal from the endocrine gland to a specific target organ or tissue.
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Endocrine gland
A gland that secretes molecules directly into the blood. Endocrine glands have no ducts.
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Exocrine gland
A gland that secretes molecules into a duct that carries the molecules to where they are used.
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Target tissue
Possess a specific receptor on their plasma membrane. The shape of the receptor is complementary to the shape of the hormone molecule. Many similar cells together form a tissue.
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1st messenger
The hormone that transmits a signal around the body.
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2nd messenger
Is cAMP, which transmits a signal inside the cell.
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Diabetes mellitus
A disease in which blood glucose concentrations cannot be controlled effectively.
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Hypoglycaemia
The state in which the blood glucose concentration is too low. (Hypo = under)
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Hyperglycaemia
The state in which the blood glucose concentration is too high. (Hyper = above)
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Stem cells
Unspecialised cells that have the potential to develop into any type of cell.
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Genetically engineered bacteria
Bacteria which has had it's DNA altered.
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Cell metabolism
The result of all the chemical reactions taking place in the cell cytoplasm.
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Myogenic
Muscle tissue that can initiate its own contractions.
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Medulla oblongata
Found at the base of the brain, it is the region that coordinates the unconcious functions of the body such s]a
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Other cards in this set

Card 2

Front

Response

Back

A change in behaviour or physiology as a result of a change in the environment.

Card 3

Front

Homeostasis

Back

Preview of the front of card 3

Card 4

Front

Negative feedback

Back

Preview of the front of card 4

Card 5

Front

Positive feedback

Back

Preview of the front of card 5
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