09a09aTransition to Transition to cranial nervescranial nerves

and the pathways and the pathways associated with themassociated with them

See pp. 360-370 in bookSee pp. 360-370 in book

What parts of the PNS are most What parts of the PNS are most proximal to the CNS?proximal to the CNS?

•Spinal nervesSpinal nerves

•Cranial nervesCranial nerves

Groups/ Aggregations /Cluster of neuronal cell bodies(gray matter)

Bundles of (myelinated) axons with common origins and destinations(white matter)

CNS Cortex (e.g. cortex of cerebrum, cortex of cerebellum)

Nuclei (e.g. nucleus gracilis, nuclei that make up the thalamus and basal ganglia)

Central gray matter of spinal cord

Nerve tract, tract, nerve pathway, pathway (e.g. spino-cerebellar tract)

Fasciculi (e.g. fasciculus gracilis)

PNS Ganglia (e.g. dorsal root ganglia; trigeminal ganglia)

Nerves (e.g., spinal nerves, cranial nerves, and their branches)

• Spinal nervesSpinal nerves– Described as Described as mixed mixed

nervesnerves: carry both : carry both sensory (afferent) sensory (afferent) and motor and motor (efferent) fibers of (efferent) fibers of trunk and limbstrunk and limbs•Somatic afferent Somatic afferent

and efferentand efferent

•Autonomic/visceral Autonomic/visceral afferent and afferent and efferentefferent

• Spinal peripheral nerves (cont.)Spinal peripheral nerves (cont.)– Sensory: posteriorSensory: posterior

•Dorsal root connects to Dorsal root connects to

dorsal horn of gray matterdorsal horn of gray matter

•GSA (general somatic GSA (general somatic

afferent) and GVA afferent) and GVA

(general visceral afferent)(general visceral afferent)

– Motor: anteriorMotor: anterior•Ventral root connects from ventral horn of gray Ventral root connects from ventral horn of gray

matter: beginning of “final common pathway” matter: beginning of “final common pathway” of somatic motor system, contains lower motor of somatic motor system, contains lower motor neuronsneurons

•GSE (general somatic efferent) and GVE GSE (general somatic efferent) and GVE (general visceral efferent)(general visceral efferent)

Now, transition to cranial Now, transition to cranial nervesnerves• Compare cranial nerves to spinal nervesCompare cranial nerves to spinal nerves

– Some cranial nerves are motor only, and Some cranial nerves are motor only, and some are sensory only. (Only some of the some are sensory only. (Only some of the cranial nerves are mixed, like the spinal cranial nerves are mixed, like the spinal nerves are)nerves are)

– Some of the cranial nerves do not carry both Some of the cranial nerves do not carry both somatic and autonomic nervous system somatic and autonomic nervous system functions; the spinal nerves carry both functions; the spinal nerves carry both somatic and autonomic nervous systems somatic and autonomic nervous systems functionsfunctions

• Cranial nervesCranial nerves– Some are sensory only, Some are sensory only,

some are motor only, some are motor only, and some are mixed. and some are mixed.

– All have some relation All have some relation to speech, language, to speech, language, hearing, hearing, communication, and/or communication, and/or swallowingswallowing

– Largely voluntary, but Largely voluntary, but some include autonomic some include autonomic and reflexive pathwaysand reflexive pathways

– Organized in pairsOrganized in pairs– Each pair designated by Each pair designated by

name and Roman name and Roman numeralnumeral

Cranial Cranial nerves nerves have have associated associated nuclei, nuclei, which are which are organized organized in clusters in clusters and and columnscolumnsDamage to nuclei can mimic damage to

the cranial nerves themselves

Focus in on cranial nerves (there are 12 pairs)Focus in on cranial nerves (there are 12 pairs)– Roots connect to CNSRoots connect to CNS

•brainstem brainstem

•uppermost spinal corduppermost spinal cord– Exit brain and pass through skull to reach the sense Exit brain and pass through skull to reach the sense

organs or muscles of head and neck with which they organs or muscles of head and neck with which they are associatedare associated

– Relatively unprotected (susceptible to damage)Relatively unprotected (susceptible to damage)– All twelve relevant to speech, language, All twelve relevant to speech, language,

communication hearing, &/or swallowing communication hearing, &/or swallowing – When cranial nerves or their associated nuclei are When cranial nerves or their associated nuclei are

damaged, this can be one of the causes of:damaged, this can be one of the causes of:•dysarthriadysarthria (speech motor disorder) (speech motor disorder)

•dysphagia dysphagia (swallowing disorder)(swallowing disorder)

Steps in learning cranial Steps in learning cranial nervesnerves• Find location of cranial nervesFind location of cranial nerves

• Learn the names associated with each Learn the names associated with each cranial nerve cranial nerve

• Overview of organization of cranial nervesOverview of organization of cranial nerves

• Details of each cranial nerveDetails of each cranial nerve– Name and locationName and location– FunctionFunction– Clinical tests of functionClinical tests of function

Cranial Cranial Nerves – Nerves – Ventral Ventral viewview

Cranial Cranial Nerves – Nerves – Dorsal Dorsal viewview

Dfdf

Trochlear Nerve (IV)

Cranial Cranial Nerves – Nerves – Lateral Lateral viewview

Names of the cranial Names of the cranial nerves: A friendly nerves: A friendly mnemonic…mnemonic…

Some Some cranial cranial nerves nerves sensorsensory, y, some some motor, motor, and and some some bothboth

Relationship Relationship to speech, to speech,

hearing, hearing, facial facial

expression, expression, swallowing…swallowing…