Biology U4 week 1 0.0 / 5 ? BiologyCellular processesA2/A-levelOCR Created by: heatherbakerCreated on: 07-03-16 18:40 Homeostasis The maintenance of the internal environment despite changes in the external environment. 1 of 16 Negative Feedback Process that brings about reversal of change in internal conditions. Ensures optimum state is maintained. 2 of 16 Positive Feedback Process that increases change in internal conditions. Doesn't lead to homeostasis. 3 of 16 Ectotherm An organism that relies on external sources of heat to regulate its body temperature. 4 of 16 Endotherm An organism that uses internal sources of heat to maintain its body temperature. 5 of 16 Polarised A membrane that has a potential difference across it. This is the resting potential (-60mV). 6 of 16 Depolarisation Loss of polarisation of membrane. When Na+ are entering cell making inside less negative compared to outside. 7 of 16 Generator Potential Small depolarisation of the membrane, caused by Na+ entering the cell. 8 of 16 Action Potential Achieved when membrane is depolarised to +40mV. All or Nothing response. 9 of 16 Threshold Potential -50mV, depolarisation at which an action potential is created. 10 of 16 Voltage-gated Channels Channels in cell membrane that allow passage of ions. Gates can open or close depending on potential difference across membrane. 11 of 16 Local Currents Movements of ions along neurone. Flow is caused by movement of ions from high concentration to low concentration. 12 of 16 Saltatory Conduction 'jumping conduction'. Refers to way action potential appears to jump from one node of Ranvier to the next in a myelinated neurone. 13 of 16 Neurotransmitter Chemical that diffuses across synaptic cleft to transmit signals to postsynaptic neurone. 14 of 16 Cholinergic Synapse A synapse which uses acetylcholine as its neurotransmitter. 15 of 16 Acetylcholinesterase enzyme in synaptic cleft which breaks down acetylcholine. 16 of 16
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