Neural Pathways

Vocabulary flashcards covering major terms and structures involved in sensory, somatic motor, and autonomic neural pathways.

Neural Pathway

A series of connected neurons that carry messages between the brain, spinal cord, and body.

Reflex Arc

A series of interconnected neurons in the spinal cord

Sensory Pathway

The route by which sensory input (e.g., pain, touch) travels from receptors to the brain.

Motor Pathway

The route that carries motor commands from the CNS to effectors; includes somatic and autonomic divisions.

Pain & Temperature Sensory Pathway

Ascending tract that transmits pain and temperature sensations from the body to the brain.

Components in sensory pathway

Parietal lobe, postcentral gyrus, primary somatosensory cortex

Thalamus

Midbrain

Pons

Medulla oblongata

Spinal cord

Primary Sensory Neuron (1° Neuron)

A unipolar neuron whose cell body lies in the dorsal root ganglion and conveys pain & temperature signals to the dorsal horn.

Secondary Sensory Neuron (2° Neuron)

A multipolar neuron that synapses in the dorsal horn, decussates, and ascends in the lateral spinothalamic tract.

Tertiary Sensory Neuron (3° Neuron)

Multipolar neuron located in the thalamus that projects through the internal capsule and corona radiata to the primary somatosensory cortex.

Decussation

The crossing of axons from one side of the CNS to the other, producing contralateral control.

Lateral Spinothalamic Tract

White-matter pathway in the lateral funiculus that carries pain and temperature signals to the thalamus.

Spinal Nerve Ramus

A branch of a spinal nerve that carries mixed sensory and motor axons.

Posterior (Dorsal) Ramus

Spinal nerve branch that supplies the skin and muscles of the posterior torso.

Anterior (Ventral) Ramus

Spinal nerve branch that supplies the anterior torso and all limbs.

Somatic Motor Pathway

Descending tract that carries voluntary motor commands from the brain to skeletal muscle.

Upper Motor Neuron

Multipolar neuron with its cell body in the primary motor cortex; axon descends to the spinal cord.

Lower Motor Neuron

Multipolar neuron in the ventral horn whose axon exits the ventral root to innervate skeletal muscle.

Interneuron

A multipolar neuron in the spinal cord that relays signals between upper motor neurons and lower motor neurons.

Lateral Corticospinal (Pyramidal) Tract

Major descending pathway in the lateral funiculus that carries voluntary motor signals after decussating in the medulla.

Ventral Root

Motor root of a spinal nerve containing lower motor neurons axons exiting the spinal cord.

Dorsal Root

Sensory root of a spinal nerve containing primary sensory neuron axons entering the spinal cord.

Nerve Plexus

A network of ventral rami that reorganizes axons to form peripheral nerves.

Cervical Plexus

Plexus that serves the neck region and diaphragm.

Brachial Plexus

Plexus that supplies the upper limbs.

Lumbar Plexus

Plexus that innervates the anterior thigh.

Sacral Plexus

Plexus that innervates the leg and posterior thigh; gives rise to the sciatic nerve.

Sympathetic response

Fight or flight

Autonomic Control Centers

Brainstem and spinal cord regions that house autonomic reflex centers regulating visceral functions.

Hypothalamus

Forebrain region that integrates sensory input and higher signals to regulate autonomic output; considered the 'boss' of the ANS.

Preganglionic Neuron

First motor neuron in an autonomic pathway; lightly myelinated axon exits the CNS to synapse in an autonomic ganglion.

Postganglionic Neuron

Second motor neuron of the ANS; unmyelinated axon leaves the ganglion to reach the target organ.

Parasympathetic Pathway

Autonomic route with long preganglionic and short postganglionic fibers; originates in brainstem & sacral cord and produces localized 'rest-digest' effects.

Terminal (Intramural) Ganglion

Parasympathetic ganglion located in or near the target organ.

Sympathetic Pathway

Autonomic route with short preganglionic and long postganglionic fibers; arises from thoracic-lumbar cord and mediates 'fight-flight' responses.

Sympathetic Chain (Trunk) Ganglia

Paired chains of sympathetic ganglia alongside the vertebral column that allow widespread effects.

Communicating Rami

Special branches connecting ventral rami to sympathetic chain ganglia.

White Communicating Ramus

Branch carrying myelinated preganglionic sympathetic axons from a ventral ramus to a chain ganglion (T1–L2 only).

Gray Communicating Ramus

Branch carrying unmyelinated postganglionic sympathetic axons from a chain ganglion back to a ventral ramus (all spinal levels).

Adrenal Medulla

Inner region of the adrenal gland comprised of modified postganglionic sympathetic neurons that release epinephrine and norepinephrine.

Epinephrine

Hormone (adrenaline) released by the adrenal medulla that amplifies sympathetic responses.

Norepinephrine

Hormone and neurotransmitter released by the adrenal medulla and sympathetic neurons, supporting 'fight-flight' effects.