Lecture 1 glossary: Neuron types and autonomic nervous system

Vocabulary flashcards covering neuron types (CNS/PNS), pathways (afferent/efferent), autonomic system components (sympathetic/paraysmpathetic, preganglionic/postganglionic, neurotransmitters), and related concepts (association/interneurons, ganglion vs nucleus, dermatome and myotome).

CNS neuron

A neuron whose cell body is in the brain or spinal cord; the majority of neurons in the nervous system are CNS neurons.

PNS neuron

A neuron whose cell body is outside of the brain and spinal cord; examples include sensory neurons or postganglionic autonomic neurons.

Afferent

A neuron that transmits information from the body to the brain or spinal cord (ascending pathway).

Efferent

A neuron that transmits commands from the brain and spinal cord to the rest of the body (descending pathway).

Motor neuron (somatic motor system)

A neuron that transmits commands from the brain to skeletal muscles to mediate voluntary movement; it always stimulates its target muscle.

Sensory neuron

A neuron that transmits sensory signals from the body to the spinal cord or brain (e.g., pressure, temperature, chemical sensing).

Autonomic neuron

A neuron that transmits commands from the CNS to smooth muscle of an organ/gland or cardiac muscle, mediating involuntary autonomic responses (sympathetic or parasympathetic).

Association neuron

A CNS neuron that relays information from sensory to motor or within the brain; also known as an interneuron; the most abundant neuronal class.

Ganglion

A cluster of neuronal cell bodies outside of the brain and spinal cord (inside the brain/spinal cord is called nucleus).

Nucleus

A cluster of neuronal cell bodies inside the brain or spinal cord.

Sympathetic

A two-neuron chain autonomic system that prepares the body for high activity (fight‑and‑flight). Example: sympathetic neuron from thoracic spinal segment increases heart rate.

Parasympathetic

A two-neuron chain autonomic system that prepares the body for low activity (rest‑and‑digest); example: Vagus nerve slows heart and breathing rate.

Preganglionic

The first neuron in the two-neuron chain of the autonomic circuit; sympathetic preganglionic neurons are short, parasympathetic preganglionic neurons are long.

Postganglionic

The second neuron in the two-neuron chain of the autonomic circuit; sympathetic postganglionic neurons are long, parasympathetic postganglionic neurons are short.

Acetylcholine

A neurotransmitter secreted by preganglionic autonomic neurons (and by parasympathetic postganglionic neurons in many cases); sympathetic preganglionic also secretes acetylcholine.

Norepinephrine

A neurotransmitter secreted by most postganglionic sympathetic neurons.

Dermatome

A skin area innervated by a spinal nerve; a spinal nerve is a mix of sensory, autonomic, and motor neurons.

Myotome

A group of muscles innervated by a spinal nerve.