Graded potential

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Graded Potentials<ref>http://www.bio.davidson.edu/courses/genomics/chip/chip.html</ref> - occur in [[Dendrites|dendrites]], cell bodies or [[Axon|axon]] terminals. Graded potential refers to the post synaptic electrical impulse. Called ‘graded’ because their size or amplitude is directly proportional to the strength of the triggering event. i.e. a large stimulus leads to the generation of a strong graded response, and a small stimulus leads to the generation of a weak graded response. This graded potentials will lose it strength and consequently, die out within 1-2mm from the their origins. Summation of graded potentials is possible that may generate [[Action potential|action potential]].  
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Graded Potentials<ref>http://www.bio.davidson.edu/courses/genomics/chip/chip.html</ref> - occur in [[Dendrites|dendrites]], cell bodies or [[Axon|axon]] terminals. Graded potential refers to the post synaptic electrical impulse. Called ‘graded’ because their size or amplitude is directly proportional to the strength of the triggering event. i.e. a large stimulus leads to the generation of a strong graded response and a small stimulus leads to the generation of a weak graded response. A graded potential will lose its strength and consequently die out within 1-2mm from the&nbsp;origin. Summation of graded potentials may generate an [[Action potential|action potential]].  
  
Graded potential may be a depolarising one or a [[Hyperpolarisation|hyperpolarising]] one.&nbsp;A depolarising local response will cause the membrane potential to be less negative thus, brings it closer to the treshold value to generate an action potental. This response increases the excitability of the cell. Meanwhile, a hyperpolarising local response has a vice versus effect towards the membrane potential value. It will make the inside of the membrane becomes more negative and therefore, reduce its excitibility&nbsp;<sup><ref>Sukkar M.Y, El-Munshid H.A, Ardawi M.S.M., (2000), Concise Human Physiology, 2nd edition. Page 44-45</ref>.</sup>
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A graded potential may be depolarising or [[Hyperpolarisation|hyperpolarising]].&nbsp;A depolarising local response will cause the membrane potential to be less negative, bringing it closer to the treshold value to generate an action potental. This response increases the excitability of the cell. Meanwhile, a hyperpolarising local response has a vice versa&nbsp;effect towards the membrane potential value. It will make the inside of the membrane become more negative, reducing&nbsp;its excitability.&nbsp;<sup><ref>Sukkar M.Y, El-Munshid H.A, Ardawi M.S.M., (2000), Concise Human Physiology, 2nd edition. Page 44-45</ref>.</sup>  
  
<sup></sup>The depolarising event may occur due to the inwards movement of positively-charged ions, such as [[sodium|sodium]] ions (Na<sup>+</sup>) to the cell, or the outwards movement of negatively-charged ions from the cell. The hyperpolarising local potential can arise due to either the negative [[anions|anions]], such as [[chloride|chloride]] ions (Cl<sup>-</sup>) enter the cell or the positive cations exit from the cell.  
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<sup></sup>The depolarising event may occur due to the inwards movement of positively-charged ions, such as [[Sodium|sodium]] ions (Na<sup>+</sup>) to the cell, or the outwards movement of negatively-charged ions from the cell. The hyperpolarising local potential can arise due to either the negative [[Anions|anions]], such as [[Chloride|chloride]] ions (Cl<sup>-</sup>) entering the cell or the positive cations exiting the cell.  
  
 
A depolarising graded potential is known as an [[Excitatory postsynaptic potential|excitatory postsynaptic potential (EPSP)]].  
 
A depolarising graded potential is known as an [[Excitatory postsynaptic potential|excitatory postsynaptic potential (EPSP)]].  
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A hyperpolarising graded potential is known as an [[Inhibitory postsynaptic potential|inhibitory postsynaptic potential (IPSP)]].  
 
A hyperpolarising graded potential is known as an [[Inhibitory postsynaptic potential|inhibitory postsynaptic potential (IPSP)]].  
  
If graded potentials reaching the axon hillock depolarise the membrane to the threshold voltage, an action potential is initiated.<br>  
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If graded potentials reach the axon hillock and depolarise the membrane to the threshold voltage (-55mV), an action potential is initiated.<br>
  
 
=== Reference  ===
 
=== Reference  ===
  
 
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Revision as of 10:57, 23 November 2017

Graded Potentials[1] - occur in dendrites, cell bodies or axon terminals. Graded potential refers to the post synaptic electrical impulse. Called ‘graded’ because their size or amplitude is directly proportional to the strength of the triggering event. i.e. a large stimulus leads to the generation of a strong graded response and a small stimulus leads to the generation of a weak graded response. A graded potential will lose its strength and consequently die out within 1-2mm from the origin. Summation of graded potentials may generate an action potential.

A graded potential may be depolarising or hyperpolarising. A depolarising local response will cause the membrane potential to be less negative, bringing it closer to the treshold value to generate an action potental. This response increases the excitability of the cell. Meanwhile, a hyperpolarising local response has a vice versa effect towards the membrane potential value. It will make the inside of the membrane become more negative, reducing its excitability. [2].

The depolarising event may occur due to the inwards movement of positively-charged ions, such as sodium ions (Na+) to the cell, or the outwards movement of negatively-charged ions from the cell. The hyperpolarising local potential can arise due to either the negative anions, such as chloride ions (Cl-) entering the cell or the positive cations exiting the cell.

A depolarising graded potential is known as an excitatory postsynaptic potential (EPSP).

A hyperpolarising graded potential is known as an inhibitory postsynaptic potential (IPSP).

If graded potentials reach the axon hillock and depolarise the membrane to the threshold voltage (-55mV), an action potential is initiated.

Reference

  1. http://www.bio.davidson.edu/courses/genomics/chip/chip.html
  2. Sukkar M.Y, El-Munshid H.A, Ardawi M.S.M., (2000), Concise Human Physiology, 2nd edition. Page 44-45
 
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