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U N I T 1 0
Nervous System
TABLE 34-1
The Segmental Nerves andTheir Components (Continued )
Segment and Nerve Component Innervation
Function
5. Caudal Pons
CNVIII: Vestibular
cochlear
(vestibulocochlear)
SSA
Vestibular end organs
Organ of Corti
Reflexes, sense of head position
Reflexes, hearing
CNVII: Facial nerve
intermedius portion
GSA
GVA
SVA
GVE
External auditory meatus
Nasopharynx
Taste buds of anterior
⅔
of tongue
Nasopharynx
Lacrimal, sublingual, submandibular glands
Somesthesia
Gag reflex: sensation
Reflexes: gustation (taste)
Mucus secretion, reflexes
Lacrimation, salivation
Facial nerve
PE
Muscles: facial expression, stapedius
Facial expression
Protects ear from loud sounds
CNVI: Abducens
GSE
Extrinsic eye muscle
Lateral eye deviation
6. Middle Medulla
CN IX:
Glossopharyngeal
SSA
Stylopharyngeus muscle
Proprioception
GSA
Posterior external ear
Somesthesia
SVA
Taste buds of posterior
⅓
of tongue
Gustation (taste)
GVA
Oral pharynx
Gag reflex: sensation
GVE
Parotid gland; pharyngeal mucosa
Salivary reflex: mucus secretion
PE
Stylopharyngeus muscle
Assists swallowing
7, 8, 9, 10. Caudal Medulla
CN X: Vagus
SSA
Muscles: pharynx, larynx
Proprioception
GSA
Posterior external ear
Somesthesia
SVA
Taste buds, pharynx, larynx
Reflexes, gustation
GVA
Visceral organs (esophagus to midtransverse
colon, liver, pancreas, heart, lungs)
Reflexes, sensation
GVE
Visceral organs as above
Parasympathetic efferent
PE
Muscles: pharynx, larynx
Swallowing, phonation, emesis
CN XII: Hypoglossal
GSE
Muscles of tongue
Tongue movement, reflexes
Spinal Segments
C1–C4 Upper Cervical
PE
Muscles: sternocleidomastoid, trapezius
Head, shoulder movement
CN XI: accessory nerve
Spinal nerves
SSA
Muscles of neck
Proprioception, DTRs
GSA
Neck, back of head
Somesthesia
GSE
Neck muscles
Head, shoulder movement
C5–C8 Lower Cervical
SSA
Upper limb muscles
Proprioception, DTRs
GSA
Upper limbs
Reflexes, somesthesia
GSE
Upper limb muscles
Movement, posture
T1–L2Thoracic, Upper
Lumbar
SSA
Muscles: trunk, abdominal wall
Proprioception
GSA
Trunk, abdominal wall
Reflexes, somesthesia
GVA
All of viscera
Reflexes and sensation
GVE
All of viscera
Sympathetic reflexes,
vasomotor control, sweating,
piloerection
GSE
Muscles: trunk, abdominal wall, back
Movement, posture, respiration
L2–S1 Lower Lumbar,
Upper Sacral
SSA
GSA
Lower limb muscles
Lower trunk, limbs, back
Proprioception, DTRs
Reflexes, somesthesia
GSE
Muscles: trunk, lower limbs, back
Movement, posture
S2–S4 Lower Sacral
SSA
Muscles: pelvis, perineum
Proprioception
GSA
Pelvis, genitalia
Reflexes, somesthesia
GVA
Hindgut, bladder, uterus
Reflexes, sensation
GVE
Hindgut, visceral organs
Visceral reflexes, defecation,
urination, erection
S5–Co2 Lower Sacral,
Coccygeal
SSA
GSA
Perineal muscles
Lower sacrum, anus
Proprioception
Reflexes, somesthesia
GSE
Perineal muscles
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.
