Biology U4 week 1

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Homeostasis
The maintenance of the internal environment despite changes in the external environment.
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Negative Feedback
Process that brings about reversal of change in internal conditions. Ensures optimum state is maintained.
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Positive Feedback
Process that increases change in internal conditions. Doesn't lead to homeostasis.
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Ectotherm
An organism that relies on external sources of heat to regulate its body temperature.
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Endotherm
An organism that uses internal sources of heat to maintain its body temperature.
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Polarised
A membrane that has a potential difference across it. This is the resting potential (-60mV).
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Depolarisation
Loss of polarisation of membrane. When Na+ are entering cell making inside less negative compared to outside.
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Generator Potential
Small depolarisation of the membrane, caused by Na+ entering the cell.
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Action Potential
Achieved when membrane is depolarised to +40mV. All or Nothing response.
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Threshold Potential
-50mV, depolarisation at which an action potential is created.
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Voltage-gated Channels
Channels in cell membrane that allow passage of ions. Gates can open or close depending on potential difference across membrane.
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Local Currents
Movements of ions along neurone. Flow is caused by movement of ions from high concentration to low concentration.
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Saltatory Conduction
'jumping conduction'. Refers to way action potential appears to jump from one node of Ranvier to the next in a myelinated neurone.
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Neurotransmitter
Chemical that diffuses across synaptic cleft to transmit signals to postsynaptic neurone.
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Cholinergic Synapse
A synapse which uses acetylcholine as its neurotransmitter.
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Acetylcholinesterase
enzyme in synaptic cleft which breaks down acetylcholine.
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Other cards in this set

Card 2

Front

Process that brings about reversal of change in internal conditions. Ensures optimum state is maintained.

Back

Negative Feedback

Card 3

Front

Process that increases change in internal conditions. Doesn't lead to homeostasis.

Back

Preview of the back of card 3

Card 4

Front

An organism that relies on external sources of heat to regulate its body temperature.

Back

Preview of the back of card 4

Card 5

Front

An organism that uses internal sources of heat to maintain its body temperature.

Back

Preview of the back of card 5
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