Peripheral Nervous System

Neuron

The basic structural and functional unit of the nervous system, consisting of a cell body, dendrites, and an axon.

Dendrite

Branch-like structures of a neuron that receive signals from other neurons and transmit them toward the cell body.

Axon

A long, thin structure that transmits electrical impulses away from the cell body to other neurons or muscles.

Schwann Cell

A type of glial cell in the peripheral nervous system that produces the myelin sheath around neuronal axons.

Myelin Sheath

A fatty layer that insulates axons, speeding up the transmission of electrical impulses.

Nodes of Ranvier

Gaps in the myelin sheath where ion exchange occurs, allowing for faster impulse propagation.

Sensory Neurons

Neurons that carry signals from sensory receptors to the central nervous system.

Interneurons

Neurons that connect sensory and motor neurons within the central nervous system.

Motor Neurons

Neurons that transmit signals from the central nervous system to muscles or glands.

Oligodendrocytes

Glial cells in the central nervous system that produce myelin, supporting and insulating axons.

Membrane Polarization

The creation of a difference in charge across the neuronal membrane, leading to a resting potential.

Action Potential Generation

A rapid rise and fall in membrane potential due to the influx of Na+ ions followed by the efflux of K+ ions.

Resting Membrane Potential

The stable, negative charge inside a neuron while not transmitting signals, usually around -70 mV.

Depolarization

The process of reducing the charge difference across a membrane, making it more positive, primarily through Na+ influx.

Repolarization

The process of restoring the membrane potential to its resting state after depolarization, mainly through K+ efflux.

Na+ and K+ Roles

Na+ leads to depolarization during an action potential, while K+ is responsible for repolarization.

Threshold Potential

The critical level of depolarization required to trigger an action potential.

Hyperpolarization

An increase in the membrane potential making the interior more negative than the resting potential, inhibiting action potentials.

All-or-None Response

The principle that a neuron either fires an action potential completely or does not fire at all.

Impulse Conduction

The process through which electrical signals travel along the axon, facilitated by myelin and nodes of Ranvier.

Neurotransmitter Function

Chemical messengers that transmit signals across the synapse from one neuron to another.

Role of Ca2+

Calcium ions that play a critical role in neurotransmitter release at synapses.

Nerve Classification

Nerves can be classified into sensory nerves (carry sensory information), motor nerves (carry motor commands), and mixed (both sensory and motor fibers).

Nervous System Organization

Divided into central (brain and spinal cord) and peripheral nervous systems; further classified into afferent (sensory) and efferent (motor).

Cranial Nerves vs. Spinal Nerves

Cranial nerves emerge directly from the brain while spinal nerves emerge from the spinal cord, with differing functions.

Parasympathetic vs. Sympathetic Effects

Parasympathetic stimulates 'rest and digest' functions, while sympathetic prepares the body for 'fight or flight' responses.