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The resting membrane potential is established by constant regeneration and maintenance of potential energy within the cell by three essential mechanisms:
- Potassium leak channels: Allow potassium ions (K ext{+}) to move out of the cell.
- Sodium leak channels: Permit sodium ions (Na ext{+}) to leak into the cell.
- Sodium-potassium pump (Na+/K+ pump): For every three Na ext{+} ions that leak into the cell, two K ext{+} ions are pumped back into the cell. This results in higher concentrations of K ext{+} inside the cell and Na ext{+} outside the cell, leading to an overall negative charge inside the cell.
In neurons, this creates a resting membrane potential of approximately -70 millivolts (mV).
- The specific resting membrane potential may vary between different types of cells, but it consistently indicates that the inside of the cell is more negative compared to the outside.

When the cell is ready to use the stored potential energy:
- Chemically gated cation channels open, allowing Na ext{+} to enter and raise the membrane potential from -70 mV to -55 mV (threshold potential).
- At this threshold, voltage-gated sodium channels open, triggering a cascade of depolarization where more Na ext{+} enters, leading to the propagation of the action potential along the neuron.
After depolarization:
- Voltage-gated calcium channels open at the transmissive segment, which is crucial for neurotransmitter release.

Neurons are the primary functional cells in the nervous system but are supported by glial cells (or neuroglial cells), which perform various important functions:
- Protect and support neurons.
- Maintain homeostasis in the neuronal environment.
Analogy: Neurons are likened to quarterbacks in football, who need support from a team (glial cells) to complete tasks effectively, such as transmitting information to muscles or glands.
- Question posed: Do glial cells send nerve impulses? No, only neurons perform that function.

The ratio of glial cells to neurons varies:
- Older studies suggested as much as 10 times more glial cells than neurons, but more recent findings indicate a one-to-one ratio overall.
- In some regions such as the brainstem or spinal cord, glial cells can outnumber neurons by ratios such as 5:1 or 8:1.

Peripheral Nervous System (PNS):
- Glial cells in the PNS include:
- Satellite cells: Surround neuron cell bodies and regulate their environment.
- Schwann cells (or neurolemocytes): Myelinate axons and support peripheral axons.
Central Nervous System (CNS): In the brain and spinal cord, the focus is on understanding the roles of different glial cells.

Neurons typically have:
- A big cell body containing a nucleus.
- Extensions (dendrites or axons) that may be classified as unipolar or pseudounipolar.
- Pseudounipolar neurons function as sensory neurons in the PNS.
**Glial Cell Functions:
- Protect neuron cell bodies.
- Regulate communication and nutrient exchange.
- Insulation of electrically active regions to prevent unwanted signal propagation.

Neurological Repair: Neurons have limited ability to repair themselves due to their non-mitotic nature. For successful repair, certain conditions must be met:
- Cell body must remain intact: It contains essential machinery (DNA, ribosomes, mitochondria).
- Neurolemma must remain intact: The plasma membrane of the neuron (crucial for neural repair).
- Endoneurium must be intact: A connective tissue covering that guides the regrowth of axons.
The process of repair can be hindered if the axon or its support structures are damaged, leading to dysfunctional connections.
Wallerian degeneration: A repair process primarily noted in the PNS, involving the dying-back of axons and subsequent regrowth toward their target tissues.

Astrocytes: A type of glial cell that wraps around blood vessels and aids in forming the blood-brain barrier (BBB), regulating what substances can enter the brain and maintaining homeostasis.
- Their star-shaped bodies with foot processes facilitate intercellular communication and supportive functions in the CNS.