Action Potentials
Action potentials are rapid electrical signals propagating along nerve cell membranes that enable information transmission in the nervous system.
Action Potentials
Action potentials are the fundamental units of neural communication, representing brief but powerful electrical impulses that propagate along neurons to transmit information throughout the nervous system.
Mechanism
The process occurs in several distinct phases:
-
Resting State
- Neurons maintain a negative resting membrane potential through ion channels and the sodium-potassium pump
- Typical resting potential is around -70 mV
-
Depolarization
- Triggered when stimulus reaches threshold potential
- Voltage-gated sodium channels open rapidly
- sodium ions rush into the cell
- Membrane potential becomes temporarily positive
-
Repolarization
- Voltage-gated potassium channels open
- potassium ions flow out of the cell
- Membrane potential returns toward resting state
-
Hyperpolarization
- Brief period where membrane potential is more negative than resting state
- Creates refractory period preventing backward signal propagation
Propagation
Action potentials travel along axons through a process of sequential activation:
- Signal moves unidirectionally
- myelin sheath increases transmission speed through saltatory conduction
- Maintains signal strength without degradation
Significance in Neural Function
Action potentials serve multiple critical roles:
- Enable rapid information transmission
- Form the basis of neural coding
- Drive neurotransmitter release at synapses
- Support muscle contraction and sensory processing
Clinical Relevance
Disruption of action potentials can lead to various neurological conditions:
- multiple sclerosis (demyelination)
- epilepsy (excessive synchronous firing)
- peripheral neuropathy (impaired conduction)
Research Applications
Understanding action potentials has enabled development of:
- neural interfaces
- electrophysiology techniques
- neuropharmacology treatments
- brain-computer interfaces
Action potentials represent a remarkable example of how complex biological systems can encode and transmit information through relatively simple electrical mechanisms, forming the foundation for neural communication and brain function.