Neuronal Membrane & Action Potential
Description of Neuronal Membrane
In general, the structure of neurons is composed of cell bodies, dendrites, nuclei, Ranvier nodes, Schwann cells, myelin sheaths, and axon ends. And the neuronal membrane is composed of lipids, proteins-fats, and chains of amino acids. The basic structure is a bilayer or sandwich of phospholipids and the organization is such that the non-polar regions face inward and the polar regions face outward. The neuronal membrane is an important site that triggers most of the processes involved in the preservation and function of neurons. These functions require the participation of membrane-related molecular and protein/lipid to initiate molecular processing as well as signal transduction. There are also receptors on the external face of the neuronal membrane to provide a kind of “attachment port” for external molecules. For each external molecular, there is a special receptor to function on membranes and inside cells. When the neuron cell is in a resting state, there is a voltage across its membrane called the resting membrane potential.
Fig.1 Schematic of a neuronal membrane. The membrane consists of a lipid bilayer and the voltage-gated sodium and potassium channels are transmembrane pores. (Verma, 2019)
Functions of Neuronal Membrane
- Control the entry and exit of ions and small molecules
- Catalyze enzymatic reactions
- Generate an electrical potential inside the cell
- Conduct an impulse
- Sensitive to particular neurotransmitters and modulators
Introduction of Action Potential
As the fundamental units for neurons communication, action potentials are defined as sudden, rapid, short-lived and propagating changes in the resting membrane potential generated in neurons, muscle cells, endocrine cells, and some plant cells. In neurons, action potentials play an important role in cell-to-cell communication with the functions to transmit and encode information and initiate multiple cellular events. The small electrical current flow between the regions of different polarities will depolarize the resting region of the cell membrane. What’s more, the action potentials conduction velocity varies along with excitable cells and can be influenced by multiple factors, such as fiber diameter, myelination, temperature, pressure, hypoxia, and ion channel number.
Fig.2 Ion movement during an action potential.
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- Verma, P.; et al. Using bifurcation theory for exploring pain. Industrial & Engineering Chemistry Research. 2019, 59(6): 2524-2535.