Action Potentials

Frage	Antworten
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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