APR Nervous System

Cauda equina
Location: vertebral canal inferior to L2 vertebral level

Description:

• large bundle of dorsal & ventral roots for nerves below L2

• Latin for “horse tail”

Conus medullaris

Location: upper lumbar vertebral canal

Description: tapered inferior end of spinal cord (spinal cord w nerves ends at L2)

Dorsal root ganglion (spinal ganglion)

Location: intervertebral foramen

Description: contains afferent/sensory neurons

Dura mater
Location: surrounds brain and spinal cord (protection)

Description: tough, dense, irregular connective tissue

• Cranial dura mater has periosteal (outer) and meningeal (inner) parts

• Cranial dura mater has dural venous sinuses

Spinal cord

Location: vertebral canal

Description: ends at L2 in adults

• Composed of inner gray matter and outer white matter

• Divided into cervical, thoracic, lumbar, sacral, and coccygeal regions

Comments:

• Continuous w/ brain at foramen magnum

• 31 pairs of spinal nerves

Ventral ramus

Location: lateral to vertebral foramen

• Cervical VR enters cervical

• Lumbar VR enters branchial

• Sacral VR enters lumbosacral plexuses

• Thoracic VR becomes intercostal and thoracoabdominal nerves

Description: motor and sensory components

• Distributed primarily to skin, limb muscles, anterolateral trunk and neck

• Comment: all VR receives gray ramus communicans from sympathetic trunk

• VRs from T1 to L2 receives white ramus communicans from sympathetic trunk

Dorsal root of Cervical region

Dorsal root ganglion of Cervical region

Dura mater of Cervical region

Ventral ramus of Cervical region

Ventral root of Cervical region

Dorsal root ganglion of Thoracic region

Dura mater of Thoracic region

Ventral ramus of Thoracic region

Cauda equina of Lumbar region

Conus medullaris of Lumbar region

Dorsal root ganglion of Lumbar region

Dura mater of Lumbar region

Ventral ramus of Lumbar region

Dorsal root of Spinal Nerve

Dorsal root ganglion of Spinal Nerve

Dura mater of Spinal Nerve

Epidural space of Spinal Nerve

Location: space external to dura mater

Description:

• Contains loose connective tissues, fat, and venous plexus in spine

• In cranial, potential space

Gray matter

Description: unmyelinated nervous tissue shaped like letter “H”

• Ventral horns house motor neurons

• Dorsal horns house sensory neurons

Spinal cord

Ventral ramus of Spinal Nerve

Ventral root of Spinal Nerve

White matter

Description: ascending and descending tracts of myelinated axons

Accessory n. (CN XI)

Location: vertebral canal, posterior cranial fossa, neck

Motor

• Cranial: joins vagus nerve (CN X) to distribute to palate muscles, pharynx, and larynx

• Spinal: trapezius and sternocleidoomastoid

CNS Connection

• Cranial: medulla oblongata

• Spinal: ventral horn of C1-C4

Cranial foramina

• foramen magnum in spinal root

• jugular foramen

Comments

• Cranial and spinal roots unite in jugular foramen to form accessory nerve

Hypoglossal n. (CN XII)

Location: posterior cranial fossa, neck, oral cavity

Motor: genioglossus, hyoglossus, styloglossus, intrinsic muscles of tongue

CNS Connection: medulla oblongata

Cranial foramina: hypoglossal canal

Comment:

• Hypoglossal nerve innervates all tongue muscles except palatoglossus (vagus nerve)

• Intrinsic tongue muscles originate and insert within tongue

Vagus n. (CN X)

Location: posterior cranial fossa, head, neck, thorax, abdomen

Composition: Motor, general sensation, special sensation, parasympathetic

Motor: muscles of palate, pharynx, and larynx

General sensation:

• Thoracic and abdominal viscera

• Epiglottis and laryngopharynx

• External acoustic meatus

Special sensation: taste from epiglottis and surrounding region

Parasympathetic:

• Mucous glands and smooth muscles of respiratory and digestive systems in neck (larynx and pharynx), thorax, and abdomen

• Cardiac muscle

CNS Connection: all medulla oblongata

• Motor: nucleus ambiguus

• General: spinal nucleus of trigeminal nerve

• Special: nucleus of solitary tract

• Parasympathetic: dorsal nucleus of vagus nerve

Cranial foramina: Jugular foramen

Comment:

• General sensation from thoracic and abdominal viscera only involves stretch

• General sensation from epiglottis and laryngopharynx involves pain, touch, and temperature

• Vagus nerve is the only cranial nerve that extends beyond head and neck

Brainstem

Location: caudal portion of brain

Description: midbrain, pons, and medulla oblongata

Cerebellum

Location: dorsal to brainstem

Description:

• Many lobes with highly folded cortex

• Attached to pons via cerebellar peduncles

Functions:

• Coordinates complex movements

• Monitor muscles to ensure fluid movements

Comment:

• cerebellar cortex has folds called folia

• White matter resembles branching trees and is called arbor vitae

• Influence motor function through thalamus and motor cortex

Cerebrum

Location: rostral portion of brain (towards the nose)

Description:

• 2 cerebral hemispheres separated by longitudinal fissure

• Hemispheres are connected by corpus callosum

• Cerebral cortex is the gray matter

• Each hemisphere has a core of white matter

• Gray matter can include basal nuclei

Corpus Callosum

• Forms floor of longitudinal fissure

Frontal Lobe

Location: anterior portion of cerebral hemisphere

Description:

• Extends from anterior pole of brain to central sulcus

• Contains precentral gyrus

Function:

• Controls voluntary motor activity

• Higher mental processing

• Emotional behavior

• Speech output (Broca’s area in left hemisphere)

Hippocampus

Location: deep in temporal lobe

Description:

• Major output via fornix

• Part of limbic system

Function:

• Learning and memory processing

• Emotional behavior

Insular Lobe

Location: Deep in each lateral sulcus

Description: Cerebral lobe

Function:

• Understanding spoken language

• Perception of taste and smell

• Integrates information from visceral receptors