Porth's Essentials of Pathophysiology, 4e

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Nervous System

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TABLE 34-1 The Segmental Nerves andTheir Components (Continued ) Segment and Nerve Component Innervation

Function

5. Caudal Pons

CNVIII: Vestibular cochlear (vestibulocochlear) CNVII: Facial nerve intermedius portion

SSA

Vestibular end organs Organ of Corti

Reflexes, sense of head position Reflexes, hearing

GSA GVA SVA GVE

External auditory meatus Nasopharynx Taste buds of anterior ⅔ of tongue Nasopharynx Lacrimal, sublingual, submandibular glands Muscles: facial expression, stapedius

Somesthesia Gag reflex: sensation

Reflexes: gustation (taste) Mucus secretion, reflexes Lacrimation, salivation Facial expression Protects ear from loud sounds

Facial nerve

PE

CNVI: Abducens

GSE

Extrinsic eye muscle

Lateral eye deviation

6. Middle Medulla CN IX:

SSA

Stylopharyngeus muscle

Proprioception

Glossopharyngeal

GSA SVA GVA GVE

Posterior external ear

Somesthesia

Taste buds of posterior ⅓ of tongue

Gustation (taste)

Oral pharynx

Gag reflex: sensation

Parotid gland; pharyngeal mucosa

Salivary reflex: mucus secretion

PE

Stylopharyngeus muscle

Assists swallowing

7, 8, 9, 10. Caudal Medulla CN X: Vagus

SSA GSA SVA GVA

Muscles: pharynx, larynx Posterior external ear Taste buds, pharynx, larynx

Proprioception Somesthesia

Reflexes, gustation Reflexes, sensation

Visceral organs (esophagus to midtransverse colon, liver, pancreas, heart, lungs)

GVE

Visceral organs as above Muscles: pharynx, larynx

Parasympathetic efferent

PE

Swallowing, phonation, emesis Tongue movement, reflexes

CN XII: Hypoglossal Spinal Segments C1–C4 Upper Cervical

GSE

Muscles of tongue

PE

Muscles: sternocleidomastoid, trapezius

Head, shoulder movement

CN XI: accessory nerve Spinal nerves

SSA GSA GSE SSA GSA GSE SSA GSA GVA GVE GSE SSA GSA GSE SSA GSA GVA GVE SSA GSA GSE

Muscles of neck Neck, back of head

Proprioception, DTRs

Somesthesia

Neck muscles

Head, shoulder movement Proprioception, DTRs Reflexes, somesthesia Movement, posture

C5–C8 Lower Cervical

Upper limb muscles

Upper limbs

Upper limb muscles

T1–L2Thoracic, Upper Lumbar

Muscles: trunk, abdominal wall

Proprioception

Trunk, abdominal wall

Reflexes, somesthesia Reflexes and sensation

All of viscera All of viscera

Sympathetic reflexes, vasomotor control, sweating, piloerection Movement, posture, respiration

Muscles: trunk, abdominal wall, back

L2–S1 Lower Lumbar, Upper Sacral

Lower limb muscles Lower trunk, limbs, back

Proprioception, DTRs Reflexes, somesthesia Movement, posture

Muscles: trunk, lower limbs, back

S2–S4 Lower Sacral

Muscles: pelvis, perineum

Proprioception

Pelvis, genitalia

Reflexes, somesthesia Reflexes, sensation

Hindgut, bladder, uterus Hindgut, visceral organs

Visceral reflexes, defecation, urination, erection

S5–Co2 Lower Sacral, Coccygeal

Perineal muscles Lower sacrum, anus Perineal muscles

Proprioception Reflexes, somesthesia

Reflexes, posture

Afferent (sensory) components: SSA, special somatic afferent; GSA, general somatic afferent; SVA, special visceral afferent; GVA, general visceral afferent. Efferent (motor) components: GVE, general visceral efferent (autonomic nervous system); PE, pharyngeal efferent; GSE, general somatic efferent; DTRs, deep tendon reflexes.