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45 Cards in this Set
- Front
- Back
Stimulus
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Any change in the environment that causes a response.
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Response
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A change in behaviour or physiology as a result of a change in the environment.
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Homeostasis
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The maintenance of the internal environment in a constant state despite external changes.
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Negative Feedback
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Brings about a reversal of any change in conditions. Ensures an optimum steady state can be maintained, as the internal environment is maintained and returned to its original conditions after any change.
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Positive Feedback
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A process that increases any change detected by receptors. It tends to be harmful and does not lead to homeostasis.
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Ectotherm
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An organism that relies on external sources of heat to regulate its body temperature.
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Endotherm
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An organism that can use internal sources of heat, such as heat generated from metabolism in the liver, to maintain its body temperature.
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Polarised Membrane
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Has a potential difference across it. The resting potential.
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Depolarisation
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The loss of polarisation across the membrane. It refers to the period when sodium ions are entering the cell making the inside less negative with respect to the outside.
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Generator Potential
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A small depolarisation caused by sodium ions entering the cell.
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Action Potential
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When the membrane is depolarised to a value of about +40 mV. An all-or-nothing response. In the event leading up to an action potential, the membrane depolarises and reaches a threshold level, then lots of sodium ions enter the axon and an action potential is reached. Can be transmitted along the axon/dendron plasma membrane.
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Resting Potential
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The potential difference or voltage across the neurone cell membrane while the neurone is at rest. About -60mV inside the cell compared with the outside. Other cells may also maintain a resting potential that might change under certain circumstances.
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Voltage-gated Channels
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Channels in the cell membrane that allow the passage of charged particles or ions. Have a mechanism called a gate which can open and close the channel. In these channels, the gates respond to changes in the potential difference across the membrane.
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Local Currents
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The movements of ions along the neurone. The flow of ions is caused by an increase in concentration at one point, which causes diffusion away from the region or higher concentration.
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Saltatory Conduction
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‘Jumping conduction’. The way that the action potential appears to jump from one node of Ranvier to the next.
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Neurotransmitter
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(Transmitter substance). A chemical that diffuses across the cleft of the synapse to transmit a signal to the postsynaptic neurone.
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Cholinergic Synapses
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Those that use acetylcholine as their transmitter substance.
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Synaptic Knob
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The swelling at the end of the presynaptic neurone.
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Acetylcholinesterase
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An enzyme in the synaptic cleft. Breaks down the transmitter substance acetylcholine.
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All or Nothing
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A neurone either conducts an action potential or does not. All action potentials are of the same magnitude, +40mV
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Summation
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The way that several small potential changes can combine to produce one larger change in potential difference across the membrane.
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Hormones
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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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Endocrine gland
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A gland that secretes hormones directly into the blood. Endocrine glands have no ducts.
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Exocrine gland
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A gland that secretes molecules into a duct that carries the molecules to where they are used.
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Target cells
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Those that possess a specific receptor on their plasma (cell surface) 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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Adenyl cyclase
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An enzyme associated with the receptor for many hormones, including adrenaline. It is found on the inside of the cell surface membrane.
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First Messenger
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The hormone that transmits a signal around the body.
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Second Messenger
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cAMP, which transmits a signal inside the cell.
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Pancreatic Duct
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A tube that collects all secretions from exocrine cells in the pancreas and carries the fluid to the small intestine.
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Islets of Langerhans
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Small patches of tissue in the pancreas that have an endocrine function.
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α cells
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Found in islets of Langerhans. Secrete the hormone glucagon.
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β cells
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Found in islets of Langerhans. Secrete the hormone insulin.
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Insulin
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The hormone, released from the pancreas, which causes blood glucose levels to go down.
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Glucagon
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The hormone that causes blood glucose levels to rise.
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Hepatocytes
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Liver cells specialised to perform a range of metabolic functions.
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Diabetes Mellitus
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A disease in which blood glucose concentrations cannot be controlled effectively.
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Hyperglycaemia
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The blood glucose concentration is too high (hyper = above, glyc = glucose, aemia = blood).
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Hypoglycaemia
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The blood glucose concentration is too low (hypo = under).
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Genetically Engineered Bacteria
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The DNA has been altered.
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Stem Cells
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Unspecialised cells that have the potential to develop into any type of cell.
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Cell Metabolism
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The result of all the chemical reactions taking place in the cytoplasm.
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Myogenic
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Muscle tissue can initiate its own contractions.
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Pacemaker
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Region of tissue in the right atrium that can generate an impulse and initiates the chamber contraction.
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Medulla Oblongata
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Found at the base of the brain. Coordinates the unconscious functions of the body.
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Cardiovascular Centre
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A part of the medulla oblongata that receives sensory inputs about levels of physical activity, blood carbon dioxide concentration and blood pressure. Sends nerve impulses to the SAN in the heart to alter the frequency of excitation waves.
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