Threshold potential

As the threshold potential is referred to in connection with the signal transmission in nerve and muscle fibers that potential difference at which an action potential is triggered. Values ​​of the membrane potentials below the threshold potential is called " subliminal " about such " above threshold ".

During the resting membrane potential ( approximately -70 mV) is a much more specific by potassium membrane potential and therefore also close to the value for the potassium equilibrium potential ( about -90 mV) is the responsible for an action potential fast voltage-gated sodium channels have an activation threshold of approximately -50 mV.

To open these ion channels for sodium, so the cell membrane must be depolarized at least on this threshold. This is done depending on the cell type and conditions either by the action of neurotransmitters that cause postsynaptic a local depolarization ( EPSP), or by a generator potential ( receptor potential in sensory cells ), or elektrotonisch the axon hillock or by a continuous -led action potential at the axon.

The threshold potential in each case has a value characteristic for the excitable cell and is determined by the specific molecular weight or properties of the channel type of the ion channel proteins.

• Neurobiology
• Neurophysiological potential