What is the Difference Between Resting Potential and Action Potential

The main difference between resting potential and action potential is that resting potential is the resting voltage or the membrane potential of a non-excited nerve cell at rest, whereas action potential is the membrane potential of an excited nerve cell during the transmission of a nerve impulse. Furthermore, resting potential is -70 mV while action potential is +40 mV. 

Resting potential and action potential are two types of membrane potentials that occur on the axon membrane of nerve cells. Resting potential is relatively static while action potential is a rapid rise and fall when considering a particular location on the membrane. 

Key Areas Covered 

1. What is the Resting Potential
     – Definition, Features, Importance
2. What is an Action Potential
     – Definition, Features, Importance
3. What are the Similarities Between Resting and Action Potential
     – Outline of Common Features
4. What is the Difference Between Resting and Action Potential
     – Comparison of Key Differences

Key Terms 

Action Potential, Depolarization, Hyperpolarization, Potassium Channels, Resting Potential, Sodium Channels

What is the Resting Potential 

Resting potential is the membrane potential of an excitable cell, mainly a neuron at rest. Generally, neurons have a negative inside due to the differential distribution of ions inside and outside of the cell membrane. Basically, the inside of the cell membrane is -70 mV when compared to the outside. Here, the sodium ion concentration is high outside, which is 145 mM. Moreover, the extracellular concentration of chloride ions is high, which is 120 mM. On the other hand, the intracellular potassium concentration (155 mM) and intracellular concentration of organic ions  (100mM) are also high.

Figure 1: Membrane Potential

Furthermore, at the resting potential, both voltage-gated sodium and voltage-gated potassium ion channels are closed. But, the sodium/potassium transporter always pumps potassium ions into the cell and sodium ions out of the cell to maintain the resting potential. Therefore, the resting potential is relatively a static value. 

What is an Action Potential 

The action potential is the membrane potential of an excitable cell during the transmission of nerve impulses. However, the main characteristic feature of the action potential is that it only occurs locally on the cell membrane, and it persists for a short period of time. Generally, an action potential fires when the membrane potential could reach into the threshold, which is -55 mV. After that, the cell membrane undergoes depolarization, increasing the membrane potential up to +40 mV.

Figure 2: Propagation of an Action Potential

Moreover, depolarization occurs through a rapid sodium influx. In response to the threshold, all the sodium channels open and allow the movement of sodium ions inside the cell membrane. However, at the peak, the sodium ions close up while opening the potassium ions. That, in turn, allows the movement of potassium ions outside the cell membrane. And, this process of depolarization is known as hyperpolarization. 

Similarities Between Resting and Action Potential 

• Resting and action potential are two types of membrane potentials that occur on the axon of a neuron. 
• Both are important for the transmission of nerve impulses. 
• They are maintained through the regulation of ion movement across the cell membrane. 

Difference Between Resting and Action Potential 

Definition 

Resting potential refers to the electrical potential of a neuron or other excitable cell relative to its surroundings when not stimulated or involved in the passage of an impulse, while the action potential refers to the change in electrical potential associated with the passage of an impulse along the membrane of a muscle cell or nerve cell. Thus, this explains the main difference between resting and action potential.

Significance 

Resting potential is the membrane potential of a neuron at rest, while action potential is the membrane potential of an excited neuron. 

Value 

While resting potential is -70 mV, an action potential is +40 mV.  

Nature 

Moreover, the resting potential is relatively static, while action potential is a rapid rise and fall when considering a particular location on the membrane. 

Voltage-Gated Ion Channels 

Both voltage-gated sodium and voltage-gated potassium ion channels are closed at the resting potential, while voltage-gated sodium channels open up, and voltage-gated potassium channels are closed at the action potential. 

Movement of Ions 

At resting potential, a high sodium ion concentration occurs in the outside, and a high potassium ion concentration occurs in the inside while, at the action potential, a huge influx of sodium ions occurs to the inside. Hence, this is another difference between resting and action potential.

Importance 

Resting potential does not allow the transmission of nerve impulses at rest, while action potential allows the transmission of nerve impulses through the membrane. 

Followed by 

Furthermore, resting potential can be either followed by an action potential or graded potentials, while action potential is followed by hyperpolarization of the membrane. 

Conclusion 

Resting potential is the membrane potential of neurons at rest. Generally, it is -70 mV. Moreover, a high sodium ion concentration occurs outside of the membrane while a high potassium ion concentration occurs inside of the membrane at the resting potential. On the other hand, the action potential is the membrane potential of neurons during the transmission of a nerve impulse. Generally, it is +40 mV. It is generated by a high sodium ion influx. However, the action potential just raises and falls, but does not persist on the membrane as the resting potential. Therefore, the main difference between resting and action potential is the value of membrane potential and their importance. 

References:

1. “Resting Membrane Potential.” Biology for Majors II, Lumen Learning, Available Here.

Image Courtesy:

1. “Action potential” By Original by en:User:Chris 73, updated by en:User:Diberri, converted to SVG by tiZom – Own work (CC BY-SA 3.0) via Commons Wikimedia   
2. “Blausen 0011 ActionPotential Nerve” By BruceBlaus. “Medical gallery of Blausen Medical 2014”. WikiJournal of Medicine 1 (2). DOI:10.15347/wjm/2014.010. ISSN 2002-4436. – Own work (CC BY 3.0) via Commons Wikimedia