09a Transition to cranial nerves and the pathways associated with them See pp in book

What parts of the PNS are most proximal to the CNS? Spinal nerves Spinal nerves Cranial nerves Cranial nerves Groups/ Aggregations /Cluster of neuronal cell bodies (gray matter) Bundles of (myelinated) axons with common origins and destinations (white matter) CNSCortex (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) PNSGanglia (e.g. dorsal root ganglia; trigeminal ganglia) Nerves (e.g., spinal nerves, cranial nerves, and their branches)

Spinal nerves Spinal nerves –Described as mixed nerves: carry both sensory (afferent) and motor (efferent) fibers of trunk and limbs Somatic afferent and efferent Somatic afferent and efferent Autonomic/visceral afferent and efferent Autonomic/visceral afferent and efferent

Spinal peripheral nerves (cont.) Spinal peripheral nerves (cont.) –Sensory: posterior Dorsal root connects to Dorsal root connects to dorsal horn of gray matter dorsal horn of gray matter GSA (general somatic GSA (general somatic afferent) and GVA afferent) and GVA (general visceral afferent) (general visceral afferent) –Motor: anterior Ventral root connects from ventral horn of gray matter: beginning of “final common pathway” of somatic motor system, contains lower motor neurons Ventral root connects from ventral horn of gray matter: beginning of “final common pathway” of somatic motor system, contains lower motor neurons GSE (general somatic efferent) and GVE (general visceral efferent) GSE (general somatic efferent) and GVE (general visceral efferent)

Now, transition to cranial nerves Compare cranial nerves to spinal nerves Compare cranial nerves to spinal nerves –Some cranial nerves are motor only, and some are sensory only. (Only some of the cranial nerves are mixed, like the spinal nerves are) –Some of the cranial nerves do not carry both somatic and autonomic nervous system functions; the spinal nerves carry both somatic and autonomic nervous systems functions

Cranial nerves Cranial nerves –Some are sensory only, some are motor only, and some are mixed. –All have some relation to speech, language, hearing, communication, and/or swallowing –Largely voluntary, but some include autonomic and reflexive pathways –Organized in pairs –Each pair designated by name and Roman numeral

Cranial nerves have associated nuclei, which are organized in clusters and columns Damage to nuclei can mimic damage to the cranial nerves themselves

Focus in on cranial nerves (there are 12 pairs) –Roots connect to CNS brainstem brainstem uppermost spinal cord uppermost spinal cord –Exit brain and pass through skull to reach the sense organs or muscles of head and neck with which they are associated –Relatively unprotected (susceptible to damage) –All twelve relevant to speech, language, communication hearing, &/or swallowing –When cranial nerves or their associated nuclei are damaged, this can be one of the causes of: dysarthria (speech motor disorder) dysarthria (speech motor disorder) dysphagia (swallowing disorder) dysphagia (swallowing disorder)

Steps in learning cranial nerves Find location of cranial nerves Find location of cranial nerves Learn the names associated with each cranial nerve Learn the names associated with each cranial nerve Overview of organization of cranial nerves Overview of organization of cranial nerves Details of each cranial nerve Details of each cranial nerve –Name and location –Function –Clinical tests of function

Cranial Nerves – Ventral view

Cranial Nerves – Dorsal view Dfdf Trochlear Nerve (IV)

Cranial Nerves – Lateral view

Names of the cranial nerves: A friendly mnemonic…

Some cranial nerves sensory, some motor, and some both

Relationship to speech, hearing, facial expression, swallowing…