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Graded Potential

Graded potential -- also referred to as receptor potentials -- are brief occurrences of depolarization or hyper-polarization of a specific arena of the membrane. Read on to know some more potent information on this subject.
Azmin Taraporewala
Last Updated: Dec 26, 2018
The graded potential of a neuron with regards to stimulation, can occur in many different ways. Mechanical stimulation, for instance pain receptors, chemicals in the brain for stimulation, such as neurotransmitters and light stimulation are certain methods through which the act of stimulation can occur.
Due to these short and transitory changes the distance between the ions, that are in constant motion plummet. These ions belong to the specific membrane area having a characteristic flow or movement.
The extent of the graded potential is directly proportional to the intensity of the stimulus or a condition that arouses action. The more the intensity of the stimulus, an increasing number of ion channels are opened. The ions, namely sodium and potassium ions are present inside and outside the membrane.
When these ion channels open hyper-polarization or depolarization occurs, where the sodium ions flow inwards and the potassium ions flow in the outward direction and the current that is the movement of the ions becomes rapid in nature. 
The ions gather very close in proximity to each other where the stimulation has taken place. The potassium ions that flow out of the membrane polarize the neighboring membranes. This polarization redirecting itself from one membrane to the other, move with a rippling effect.
These waves culminate into polarized membranes reverting back to the resting membrane potential. There could be two probabilities in this condition. The wave across the membrane may either add up or decline with other polarization waves or may simply die out and lose its potential intensity. 
Graded potential system is suitable to act as a reactive signal for short-lived polarization activity. The waves plummet and gradually die out because of the leakage channels in the membrane of nervous system. The primary function is to operate and shift the axon hillock on the potential threshold membrane. This is where the action potential will take place.
Graded Potential and Action Potential
Having explicated the graded potential definition, let's shift our focus on the concept of action potential and the relation between the graded potential and action potential. As described earlier the main aim of graded potential is to shift the axon hillock on the potential threshold membrane and it is here that the action potential will generate itself. 
With regards to the sensory region neurons, the action potential comes into being through the axonal process, also called the peripheral process, that is situated very close to the receptor potentials. The receptor region in the sensory neuron is termed as the trigger region. The threshold that the axon hillock reaches is a potential membrane. 
The membrane situated in the trigger region escalates up to -55mV. The depolarization occurs at about 15mV. When the action potential touches this point, it garners the capacity to trigger the adjoining action potentials. This is how action potential generation takes place. Action potentials, therefore, are self-regulating or self-propagating.
  • Difference No. 1 - The intensity of the graded potential will decrease, while the intensity of the action potential will be a complete to no response. The intensity of the graded potential is directly proportional to the intensity or the strength of the stimulus, whereas the strength of the action potential remains the same throughout.
  • Difference No. 2 - Graded potentials occur when the intensity of the potential stimulus increases, whereas the action potential is directed by the frequency at which the process of depolarization takes place. Thus, the graded potential is amplitude modulated and action potential is said to be frequency modulated.
  • Difference No. 3 - As long as the stimulus and its intensity exists, the graded potential will exist. Action potential will persist only for 0.15ms.
  • Difference No. 4 - To generate action potential, a huge amount of dynamism in the potential is needed (around 15mV). Graded potential demands very large/no charge to generate itself. So, it has no threshold.
  • Difference No. 5 - In the graded potential, the wave is increasing or accumulative in nature. On the other hand, the action potential has a set time period where no other reaction in terms of action potential generation, will occur in the particular domain of the membrane.
Thus, the neurons in the graded potentials and the action potential communicate through nerve impulses. Apart from the neurons being generators of the action potential, muscle cells also propagate action potential. Hope this helps you to comprehend the role graded potential plays in the human body system and the nitty-gritty of the same. Wish you good luck!