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Chapter 16-19

ANAT 100 Chapter Notes - Chapter 16-19: Glossopharyngeal Nerve, Cranial Nerves, Vestibulocochlear Nerve

Anatomy and Cell Biology
Course Code
ANAT 100
Leslie W Mac Kenzie

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Module 6: Nervous System and Special Senses
6.1 Peripheral Nervous System (PNS)
Spinal nerves
Cranial nerves
Two subdivisions:
Sensory (afferent) division:
Somatic (general sensation)
Visceral (organ sensation)
Motor (efferent) division:
Somatic (voluntary)
Autonomic (involuntary)
Spinal Nerves:
31 pairs
Union of thousands of motor and sensory axons
Formed by union of dorsal and ventral roots of the spinal cord
Alphanumeric classification according to spinal levels
Nerve Plexus: network of interweaving anterior rami of spinal nerves
these then split into multiple “named” nerves that innervate various body structures
Dermatome: a specific segment of skin supplied by a single spinal nerve
all spinal nerves except C1 innervate a segment of skin
each of these nerves is associated with a dermatome
Reflex Activity: rapid, automatic, involuntary reactions of muscles or glands to a stimulus
Somatic and/or visceral reflexes
Five components of a reflex arc: always begins at a receptor in the PNS, communicates
with the CNS, and ends at a peripheral effector, such as a muscle or gland cell
1. Stimulus activates receptor
2. Nerve impulse travels through sensory neuron to the CNS
3. Information from nerve impulse is processed in the integration center by interneurons
4. Motor neuron transmits nerve impulse to effector
5. Effector responds to nerve impulse from motor neuron
Cranial Nerves:
12 pairs originating from the brain and brain stem
Numbered using Roman Numerals
Sensory, motor, and mixed nerves
Five general functions:
Special sensory
Somatic sensory
Visceral sensory
Somatic motor
Visceral motor
CN I Olfactory - sensory: Smell/nose
CN II Optic - sensory: Vision
CN III Oculomotor - motor
innervates upper eyelid muscle and four of the six extrinsic eye muscles
Somatic motor function: Eye movement
Parasympathetic: Pupil constriction

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CN IV Trochlear - motor: Eye movement
supplies one extrinsic eye muscle (superior oblique) to move eye inferiorly and laterally
CN V Trigeminal -three divisions (motor and sensory):
Sensory to forehead and eye
Sensory to upper and lower jaw region, anterior two-thirds of tongue
Motor to muscles of mastication
CN VI Abducens -motor:
Eye movement: Innervates one extrinsic eye muscle (lateral rectus) for eye abduction
CN VII Facial - mixed (Motor and sensory):
Motor to muscles of facial expression
Sensory for taste from tongue (anterior 2/3):
■ Parasympathetic
Parasympathetic for submandibular and sublingual salivary glands (except parotid)
CN VIII Vestibulocochlear (auditory or acoustic) -sensory:
Vestibular (equilibrium/balance): Conducts equilibrium and auditory sensations to brain
Cochlear (hearing)
CN IX Glossopharyngeal - mixed (motor and sensory):
Sensory for taste (posterior 1/3 of tongue), pharynx, middle ear
Motor to pharyngeal (throat) muscles
Parasympathetic to parotid gland
CNX Vagus - mixed (motor and sensory):
Motor to muscles of larynx, pharynx and soft palate
Sensory to larynx
Parasympathetic for organs in thoracic and abdominal cavities:visceral smooth muscle,
cardiac muscle, and glands of heart, lungs, pharynx, larynx, trachea, and most abdominal
CN XI Accessory - motor:
Innervates trapezius, sternocleidomastoid, and some pharynx muscles
CN XII Hypoglossal - motor:
innervates intrinsic and extrinsic tongue muscles
Remember these study tips to help you learn the cranial nerves:
On Occasions, Our Trusty Truck Acts Funny - Very Good Vehicle Any How
Oh, Once One Takes The Anatomy Final Very Good Vacations Are Heavenly
6.2 Autonomic Nervous System
includes processes regulated below the conscious level
visceral sensory components include receptors that detect stimuli associated with blood vessels
and internal organs or viscera
autonomic motor, or visceral motor, components initiate and transmit nerve impulses from the
CNS to cardiac muscle, smooth muscle, and glands
function of the ANS is to maintain homeostasis, or a constant internal environment
Motor component of the visceral nervous system:
Visceral motor (smooth muscle, cardiac muscle, glands)
Pathways for motor output:
Two-neuron chain:
Preganglionic neurons with cell bodies in CNS
Postganglionic neurons with cell bodies in ganglia outside CNS
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