Neuroanatomy

What makes up the PNS?

Cranial nerves, spinal nerves, ganglia; derived from neural crest cells.

What are ganglia?

Clusters of neuronal cell bodies in the PNS; can be sensory or autonomic.

What is gray matter?

Areas with dense neuronal cell bodies; cortex in brain, central butterfly in spinal cord. CELL BODIES

What is white matter?

Myelinated axon bundles; internal brain structures and external spinal cord. AXONS

How do gray and white matter differ in brain vs. spinal cord?

Brain: gray = outer; cell bodies; white = inner,axons. They swap. Spinal cord: gray = inner,axons; white = outer,cell bodies.

What is a first-order neuron?

The initial sensory neuron that detects and sends input.

What is a second-order neuron?

A relay neuron that receives signal from the first-order neuron.

What defines gross features of brain?

Lobes, sulci, gyri, cortical landmarks, ventricles.

Sulci vs Gyri

Sulci= invaginations

Gyri= surface grooves (think of gyro they look good on the surface)

Precentral gyrus in frontal lobe function (think TMS)

primary motor cortex

Postcentral gyrus in parietal lobe

somatosensory cortex

Calcarine fissure function (in occipital lobe)

primary visual cortex

Superior temporal gyrus

auditory/hearing

Broca’s area

speech production

Wernicke’s area

language comprehension

Dorsal Root Ganglion Neuron type

sensory(afferent)

Ventral root ganglion neuron type

motor(efferent)

What is a dermatome?

Skin region innervated by one spinal nerve and corresponding spinal segment.

Somatic=

body wall

Visceral=

smooth muscle (autonomic)

How is a spinal nerve anatomically arranged?

Dorsal root (sensory), ventral root (motor) → join to form spinal nerve → branch into dorsal/ventral rami.

What are the four fiber types in a spinal nerve? (hint they all start with “general”

GSA: general somatic afferent; GVA: general visceral afferent; GVE: general visceral efferent; GSE: general somatic efferent.

How do spinal nerves transmit info between PNS and CNS?

Afferent fibers send sensory input to CNS via dorsal root; efferent fibers send motor output from CNS via ventral root to muscles/organs.

What distinguishes the dorsal and ventral rami?

Dorsal rami → back of body; Ventral rami → front of body; both carry sensory and motor axons.

What are tracts and nerves?

Tracts: CNS axon bundles; Nerves: PNS axon bundles.

What does afferent vs. efferent mean?

Afferent = toward CNS (sensory); Efferent = away from CNS (motor).

Upper motor neuron

in the motor cortex, sends commands down axons in the CNS

Lower motor neuron

relays the command from the CNS to the skeleltal muscle; located in ventral horn of spinal cord