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Home > Lecture notes on Physiology > Physiology of the Nervous system > Physiology of Neurons > Neuronal action Potential > Graded Potentials versus action Potentials
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There are vital differences in between graded potentials and activity potentials the neurons (see development to this lecture). Table 1 list the main differences between graded potentials and action potentials. As debated in this lecture and also upcoming lectures, most of these distinctions are due to the truth that graded potentials result from the passive electrical property of the neuronal membrane, whereas action potentials result from an orchestrated response to depolarizing stimuli, and involve a coordinated task of voltage-gated ion channels. Graded potentials must happen to depolarize the neuron come threshold before activity potentials have the right to occur. Relying on the cell and form and the nature that stimulus, graded potentials that lead to activity potentials are dubbed synaptic potentials (i.e., post-synaptic potential transforms in neurons), generator potentials or receptor potentials (graded potentials in sensory cells reasons by enough stimuli), or end-plate potentials (i.e., synaptic potentials in skeleton muscle cells). These graded potentials will be disputed in later lectures. In the following lecture, us will take into consideration the propagation that neuronal activity potentials and we will view that additional neuronal adaptations allow activity potentials to travel over long distances without losing any strength (i.e., amplitude). In yet one more later lecture, we will see exactly how summation the graded potentials is responsible for much of information processing at specialized contact regions in between neurons (synapses).
Graded potentials Action potentials
Depending ~ above the stimulus, graded potentials can be depolarizing or hyperpolarizing. Action potentials always lead to depolarization that membrane and also reversal that the membrane potential.
Amplitude is proportional to the strength of the stimulus. Amplitude is all-or-none; strength of the stimulus is coded in the frequency of all-or-none action potentials generated.
Amplitude is generally little (a few mV to tens of mV). Large amplitude that ~100 mV.
Duration the graded potentials may be a few milliseconds come seconds. Action potential term is relatively short; 3-5 ms.
Ion networks responsible because that graded potentials might be ligand-gated (extracellular ligands such together neurotransmitters), mechanosensitive, or temperature perceptible channels, or may be networks that space gated by cytoplasmic signaling molecules. Voltage-gated Na+ and also voltage-gated K+ channels are responsible because that the neuronal action potential.
The ions involved are typically Na+, K+, or Cl−. The ions associated are Na+ and also K+ (for neuronal action potentials).
No refractory period is associated with graded potentials. Absolute and also relative refractory durations are important facets of action potentials.
Graded potentials deserve to be summed in time (temporal summation) and also across an are (spatial summation). Summation is not possible with action potentials (due come the all-or-none nature, and also the visibility of refractory periods).
Graded potentials travel by passive spread (electrotonic spread) to neighboring membrane regions. Action potential propagation to surrounding membrane regions is characterized by rejuvenation of a brand-new action potential at every suggest along the way.
Amplitude diminishes as graded potentials travel away native the initial site (decremental). Amplitude does no diminish as activity potentials propagate along neuronal projections (non-decremental).
Graded potentials room brought around by exterior stimuli (in sensory neurons) or by neurotransmitters released in synapses, where they cause graded potentials in the post-synaptic cell. Action potentials are triggered by membrane depolarization to threshold. Graded potentials are responsible because that the early membrane depolarization to threshold.
In principle, graded potentials can occur in any an ar of the cell plasma membrane, however, in neurons, graded potentials happen in dedicated regions that synaptic call with other cells (post-synaptic plasma membrane in dendrites or soma), or membrane regions affiliated in receiving sensory stimuli. Occur in plasma membrane areas where voltage-gated Na+ and also K+ channels are very concentrated.

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Note: The details of action potentials listed here describe those the neuronal activity potentials. Together we will watch throughout our study of physiology, other activity potentials (for example, in skeletal, cardiac, and also smooth myocytes, and in part endocrine cells) exhibit various features 보다 those pointed out here.
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