459871
Description
Flashcards by Morgan Morgan, updated more than 1 year ago
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Created by Morgan Morgan
almost 12 years ago
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| Question | Answer |
| Action potentials are produced when | the membrane depolarises in excitable cells. |
| Positive feedback is switched off when the membrane voltage reaches what level? | +30mv |
| Only when the stimulus strength is at a certain level is an action potential generated. This level is called the? | Threshold. |
| The threshold voltage is | -55mv. |
| Once APs are generated they are always of the same size, even though the stimulus strength might increase. This is... | The all or none law of action potentials. |
| Action potentials can code? | information |
| Information is coded by sequences or trains of APs. Information can be coded in the .... | frequency of APs the duration of the AP train |
| Only when two stimuli are separated by a sufficient time interval will a.....AP be generated after the first. | second |
| The time interval is about | 10 milliseconds. |
| This period is known as the | Refractory period. |
| Action potentials move from one end of the nerve axon to the other. This is called.... | Propagation |
| In some nerves the axon is surrounded by a sheath of fatty material called... | Myelin |
| Myelin is produced by | Schwann cells |
| Myelin acts as an | electrical insulator. |
| The myelin sheath is interrupted by gaps called the .... | nodes of ranvier. |
| Action potentials are therefore ONLY generated at the ......in a myelinated nerve. | nodes of ranvier |
| Aps appear to jump from one node to the next. This is known as | Saltatory conduction. |
| The larger the diameter of the nerve axon.... | the faster the conduction velocity. |
| The fastest nerves are | large diameter, myelinated nerves. Up to 100m/sec. |
| The slowest nerves are | small diameter, non-myelinated nerves.0.5-2m/sec |
| What happens when the AP reaches the axon terminals? | AP depolarises the terminal region. Causes small vesicles in the terminal to fuse with the terminal membrane. These vesicles contain neurotransmitters. |
| Examples of neurotransmitters? | Noradrenaline. acetylcholine. dopamine histamine 5-hydroxytryptamine |
| A nerve junction is called a | synapse. |
| A muscle junction is called a | neuromuscular junction. |
| Absolute refractory period | Cannot generate an AP no matter how big the stimulus is. |
| Relative refractory period | AP can be generated but only if a bigger stimulus is used. |
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