Autonomic Nerves

Epineurium

The outermost layer that surrounds the entire peripheral nerve.

Perineurium

The middle layer that surrounds groups of nerve fibers, forming fascicles within a peripheral nerve.

Endoneurium

The innermost layer that surrounds individual nerve fibers within a fascicle.

Somatic Nerves

Responsible for voluntary functions, controlling skeletal muscle movement and transmitting sensations from body walls (skin, mucous membranes). Their pathway is a single continuous nerve from the CNS to the target effector.

Autonomic Nerves

Control involuntary body functions, activate organs, and transmit sensations from organs and glands. Their pathway involves two nerves linked by a synapse between the CNS and the target.

Dendrites

Projections from the neuron that receive signals.

Cell Body (Neuron)

Contains the nucleus and organelles of the neuron.

Efferent (Motor) Nerves

Carry instructions from the brain or spinal cord to peripheral axon terminals, leading to an effector organ or postsynaptic neuron.

Afferent (Sensory) Nerves

Carry information from body receptors to the Central Nervous System (CNS).

Myelin Sheath

Insulates axons and increases the speed of nerve impulse conduction.

Synapses

Electrochemical communication junctions between nerve cells, involving a presynaptic neuron, synaptic cleft, and postsynaptic neuron.

Synaptic Cleft

The gap between the pre-synaptic and post-synaptic neurons where neurotransmitters are released.

Sympathetic Nervous System

Prepares the body for "fight or flight" emergencies, stress, and activities. Neurons typically synapse in the sympathetic trunk or prevertebral ganglia.

Parasympathetic Nervous System

Manages "rest and digest" activities and conserves energy. Neurons synapse in or near the walls of target tissues and organs.

Referred Pain

Sensation of pain from a visceral organ perceived at a different, often superficial, location on the body.

Celiac Ganglion

A key sympathetic ganglion serving abdominal organs.