Unit 1, Module 1 - Communication and Homeostasis Definitions

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Any change in the environment that causes a response.
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A change in behaviour or physiology as a result of a change in the environment.
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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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An organism that relies on external sources of heat to regulate its body temperature.
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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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Exergonic reaction
When energy is released in the form of heat due to the result of the reaction.
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A chemical that diffuses across the cleft of the synapse to transmit a signal to the postsynaptic neurone
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Cholinergic synapses
Synapses that use acetylcholine as their transmitter substance.
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All or nothing
A neurone either conducts an action potential or it does not. All action potentials are of the same magnitude, +40mV.
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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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An endocrine gland
A gland that secretes hormones directly into the blood. Endocrine glands have no ducts.
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An exocrine gland
A gland that secretes molecules into a duct that carries the molecules to where they are used.
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The target cells
Cells that 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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The 1st messenger
The hormone that transmits a signal around the body.
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The 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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The state in which the blood glucose concentration is too high. (hyper=above, glyc=glucose, aemia=blood)
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The state in which the blood glucose concentration is too low. (hypo=under)
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Genetically engineered bacteria
Bacteria where the DNA has been altered. In this case a gene coding for human insulin has been inserted into the DNA of the bacteria.
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Stem cells
unspecialised cells that have the potential to develop into any type of cell.
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Cell metabolism
The result of all the chemical reaction taking place in the cytoplasm.
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Muscle tissue that can initiate its own contractions.
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The medulla oblongata
Found at the base of the brain, it is the region that coordinates the unconscious functions of the body such as breathing rate and heart rate.
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The cardiovascular centre
A specific region of the medulla oblongata that receives sensory inputs about the levels of physical activity, blood carbon dioxide conc. and blood pressure. It sends nerve impulses to the SAN in the heart to alter the frequency of excitation waves.
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A change in behaviour or physiology as a result of a change in the environment.

Card 3




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Card 4


Negative Feedback


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Card 5


Positive Feedback


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