The uneven distribution of ions inside and outside the cell, as well as the cell membrane’s varying permeability to various ions, influences the resting membrane potential (RMP). In this article, let us discuss the RMP of skeletal muscle and RMP of cardiac muscle.
Table of Contents
- What is Resting Membrane Potential?
- RMP of Skeletal Muscle
- RMP of Cardiac Muscle
- Frequently Asked Questions
What is Resting Membrane Potential?
The electrical potential difference across the cell membrane (between the outside and inside of the cell) under resting conditions is known as the resting membrane potential. It is also known as membrane potential, transmembrane potential and transmembrane potential gradient.
Membrane voltage of the majority of excitable cells such as muscles, neurons and some secretory cells can also alter in response to external or intracellular stimuli. The varied membrane permeabilities bring about the resting potential for sodium, potassium, chloride and calcium ions, which in turn come from the functional activity of many ion channels, ion transporters, and exchangers.
RMP of Skeletal Muscle
The movement of ions creates an ionic imbalance across the cell membrane, which is necessary for the development and maintenance of the resting membrane potential in a muscle fibre or a neuron. This ionic imbalance can result from two things:
- Sodium-potassium pump
- Selective cell membrane permeability
Due to these two factors, more positivity develops outside the cell and more negativity develops inside. This continuous potential difference is known as resting membrane potential.
A polarised state refers to the state of the muscle during resting membrane potential. The membrane potential at rest in human skeletal muscle is -90 mV. The resting membrane potential (RMP) of skeletal muscle is mostly a result of the K+ concentration ratio across the sarcolemma membrane. This is because there are more K+ channels than Na+ channels, and all cell membranes are more permeable to K+ than to Na+.
Skeletal muscle has a resting membrane potential of -90 mV and it is measured as a straight baseline.
Also see: Difference between Skeletal Muscle Action Potential and Cardiac Muscle Action Potential
RMP of Cardiac Muscle
Similar to skeletal muscles, cardiac muscles also have a resting membrane potential of about -90 millivolts (mV; 1 mV = 0.001 V), meaning that the inside of the membrane is more negative than the outside. While potassium (K+) predominates inside the cell, sodium (Na+) and chloride (Cl) are the primary ions present outside the cell while it is at rest.
Work cells and pacemaker cells are two different categories of cardiac myocytes. The work cells exhibit a prolonged action potential with a plateau phase and have a substantial, stable resting membrane potential. The intrinsic electrical activity of the heart is produced by the pacemaker cells because they have smaller, more unstable resting potentials and spontaneously depolarise. The resting membrane potential of a healthy cardiac cell is approximately -90 mV.
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