Biology

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Stimulus
is any change in the environment that causes a response.
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Response
is a change in behavior or physiology as a result of a change in the environment.
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Homeostasis
is the maintenance of the internal environment in a constant state despite external changes.
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Negative feedback
is a process that brings about a reversal of any change in conditions. It ensures that an optimum steady state can be maintained.
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Positive Feedback
is 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
is an organism that relies on external sources of heat to regulate its body temperature.
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Endotherm
is an organism that can use internal sources of heat, such as heat generated from metabolism in the liver, to maintain its body body temperature.
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Generator potential
is a small depolarisation caused by sodium ions entering the cell.
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Action Potential
is achieved when the membrane is depolarised to a value of about +40mV. It is a all or nothing response.
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Resting potential
is the potential difference or voltage across the neurone cell membrane while the neurone is at rest. It is about -60mV inside the cell compared with the outside.
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Voltage-gated channels
are channels in the cell membrane that allow the passage of charged particles or ions. They have a mechanism called a gate which can open and close the channel.
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Threshold potential
is a potential difference across the membrane of about -50mV. If the depolarisation of the membrane does not reach the threshold potential then no action potential is created.
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Action Potential
is a depolarisation of the cell membrane so that the inside is more positive than the outside, with a potential difference across the membrane of +40mV.
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Local curents
are 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 of higher concentration.
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Saltatory
conduction means jumping conduction. It refers to the way that the action potential appears to jump from one node of Ranvier to the next.
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Neurotransmitter
is a chemical that diffuses across the cleft of the synapse to transmit a signal to the postsynaptic neurone.
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Cholinergic synapses
are those that use acetylcholine as their transmitter substance.
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Synaptic knob
is a swelling at the end of the presynaptic neurone.
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Acetylcholinesterase
is an enzyme in the synaptic cleft. It breaks down the transmitter substance acetylcholine.
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All or nothing
refers to the fact that a neurone either conducts an action potential or it does not. All action potentials are the same magnitude, +40mV.
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Summation
is a term that refers to 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
are molecules that are releases 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
is a gland that secretes hormones directly into the blood. Endocrine glands have no ducts.
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Exocrine gland
is a gland that secretes molecules into a duct that carries the molecules to where they are used.
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Target cells
are those that possess a specific receptor on their plasma membrane. The shape of the hormone molecule. Many similar cells together form a tissue.
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Adenyl cyclase
is 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
is the hormone that transmits a signal around the body.
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Second Messenger
is cAMP, which transmits a signal inside the cell.
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Pancreatic duct
is a tube that collects all the secretions from the exocrine cells int he pancreas and carries the fluid to the small intestine.
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Islets of Langerhans
are small patches of tissue in the pancreas that have an endocrine function.
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Insulin
is the hormone, released from the pancreas, that causes blood glucose levels to go down.
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Glucagon
is the hormone that causes blood glucose levels to rise.
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Hepatocytes
are liver cells. They are specialised to perform a range of metabolic functions.
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Diabetes mellitus
is a disease in which blood glucose concentrations cannot be controlled effectively.
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Hyperglycaemia
is the state in which the blood glucose concentration is too high.
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Hypoglycaemia
is the state in which the blood glucose concentration is too low.
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Genetically engineered
bacteria are those in which 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
are unspecialised cells that have the potential to develop into any type of cell.
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Cell metabolism
is the result of all the chemical reactions taking place in the cytoplasm.
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Myogenic
muscle tissue can initiate its contractions.
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Pacemaker
is a region of tissue in the right atrium wall that can generate an impulse and initiates the contraction of the chambers.
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Medulla oblongata
is found at the base of the brain. It is the region of brain that coordinates that unconscious functions of the body such as breathing rate and heart rate.
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Cardiovascular centre
is a specific region of the medulla oblongata that recieves sensory inputs about levels of physical activity, blood carbon dioxide concentration and blood pressure.
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Other cards in this set

Card 2

Front

is a change in behavior or physiology as a result of a change in the environment.

Back

Response

Card 3

Front

is the maintenance of the internal environment in a constant state despite external changes.

Back

Preview of the back of card 3

Card 4

Front

is a process that brings about a reversal of any change in conditions. It ensures that an optimum steady state can be maintained.

Back

Preview of the back of card 4

Card 5

Front

is a process that increases any change detected by the receptors. It tends to be harmful and does not lead to homeostasis.

Back

Preview of the back of card 5
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