The Peripheral Nervous System
Chapter 13
Divisions of the Nervous System
Classification of Sensory Receptors
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By Location
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Exteroceptors
Interoceptors
Proprioceptors
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By Stimulus Type
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Mechanoreceptors
Thermoreceptors
Photoreceptors
Chemoreceptors
Baroreceptors
Nociceptors
Unencapsulated Nerves
Encapsulated Nerves
Encapsulated Nerves
Connective Tissues of a Nerve
Types of Nerves
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Sensory (afferent) Nerves
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Motor (efferent) Nerves
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Mixed Nerve (both)
Regeneration of an Injured Nerve
Cranial Nerves
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12 pairs
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Classified as sensory, motor or mixed
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First two pairs attach to the forebrain
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Remaining ten pairs attach to the brainstem
Cranial Nerves
Cranial Nerves
Olfactory Nerve (I)
Olfactory Nerve (I)
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Sensory only
Sense of smell
Olfactory bulbs that terminate into filaments
piercing the cribriform plate of the ethmoid
bone.
Anosmia: loss of smell
Optic Nerve (II)
Optic Nerve (II)
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Sensory only
Vision
Begins at the retina, converges at the optic
chiasma, partial crossing over of the fibers
to enter the thalamus. Optic radiations take
impulse to the visual cortex in the occipital
lobe.
Anopsias= loss of vision
Oculomotor Nerve (III)
Oculomotor Nerve (III)
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Motor only
Controls 4 of the six eye muscles for eyeball
movement and pupil constriction:
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Superior rectus
Medial rectus
Inferior rectus
Inferior oblique
External Strabismus=eye rotates laterally
Oculomotor Nerve (III)
Trochlear Nerve (IV)
Trochlear Nerve (IV)
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Motor only
Movement of one eye muscle: superior
oblique muscle
Downward and lateral movement of the
eyeball.
Damage to this nerve can cause double
vision and the inability to rotate the eye
inferolaterally
Trigeminal Nerve (V)
Trigeminal Nerve (V)
Trigeminal Nerve (V)
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Mixed nerve
Largest cranial nerve
Sensory=somatic sensations of the face
Motor=controls muscles of mastication
Three divisions: V1- Ophthalmic division
V2- Maxillary division
V3- Mandibular division
Tic douloureux=inflammation of the
trigeminal nerve
Abducens Nerve (VI)
Abducens Nerve (VI)
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Motor only
Innervates the lateral rectus muscle of the
eye
Moves eyeball laterally
Internal Strabismus=eye rotates medially
Abducens Nerve (VI)
Facial Nerve (VII)
Facial Nerve (VII)
Facial Nerve (VII)
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Mixed nerve
Motor=Controls muscles of facial expression
Motor=Controls lacrimal and two of the three
types of salivary glands (sublingual and
submandibular glands)
Sensory=Taste of anterior 2/3 of tongue
Bell’s palsy=unilateral facial paralysis
Vestibulocochlear Nerve (VIII)
Vestibulocochlear Nerve (VIII)
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Sensory only
Vestibulo branch: equilibrium
Cochlear branch: hearing
Travels through the internal acoustic meatus
Nerve deafness caused by damage to the
cochlear branch while dizziness and vertigo
are caused by damage to the vestibular
branch
Glossopharyngeal Nerve (IX)
Glossopharyngeal Nerve (IX)
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Mixed nerve
Motor=muscle innervations to part of the
tongue and pharynx
Sensory=Taste for bitter on the posterior 1/3
of the tongue
Swallowing and gag reflex
Vagus Nerve (X)
Vagus Nerve (X)
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Mixed nerve
Motor=heart rate, breathing, and digestive
function, muscles of the voicebox.
Sensory=taste from the posterior portions of
the tongue and pharynx (taste), abdominal
and thoracic viscera
Destruction of the vagus nerve is
incompatible with life
Accessory Nerve (XI)
Accessory Nerve (XI)
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Motor (primarily)
Innervates trapezius and
sternocleidomastoid muscle
Damage would result in the inability to shrug
the shoulders and turn the head
Hypoglossal Nerve (XII)
Hypoglossal Nerve (XII)
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Motor (primarily)
Tongue movements: swallowing and speech
Spinal Nerves
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Mixed nerves
31 pairs of spinal nerves total
(8) Cervical - cervical and brachial plexus
(12) Thoracic - intercostal nerves and
cervical and lumbosacral enlargement
(5) Lumbar - lumbar plexus
(5) Sacral - sacral plexus
(1) Coccygeal
Distribution of Spinal Nerves
Formation of Spinal Nerves
Formation of Spinal Nerves
Cervical Plexus
Cervical Plexus
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Most branches are cutaneous nerves that
supply sensory impulses from the skin of the
neck, ear, back of the head and shoulders
Other branches innervate the muscles of the
anterior neck
Phrenic nerve = sole motor nerve supply to
the diaphragm for breathing
Brachial Plexus
Brachial Plexus
Median nerve: Flexor muscles of the anterior
forearm and intrinsic muscles in palm;
pronates the forearm, flex the wrist and
fingers, and oppose the thumb
Radial nerve: largest branch; posterior
muscles of the arm and forearm; innervates
all the extensor muscles for elbow, wrist, and
finger extension, forearm supination, and
thumb abduction
Brachial Plexus
Ulnar nerve: produces wrist and finger flexion
and adduction as well as abduction of the
medial fingers
Suprascapular nerve: innervates the
supraspinatus and infraspinatus muscles for
movement of the shoulder
Brachial Plexus
Thoracic Nerves
Lumbar Plexus
Lumbar Plexus
Femoral nerve: the largest terminal nerve of
this plexus and innervates the anterior muscles
of the thigh (thigh flexors and knee extensors).
Branches to form the saphenous nerve on the
medial thigh and knee.
Obturator nerve: innervates the adductor
muscles of the leg.
Lumbar Plexus
Sacral Plexus
Sacral Plexus
Sciatic nerve: which supplies the entire lower
limb (leg) except the anteromedial thigh.
The sciatic nerve is also the thickest and
longest nerve in the body and branches to form
the 1- tibial nerve (which further branches to
form the sural nerve and plantar nerves) and
the 2- common fibular nerve
Reflexes
Reflex Activity
Reflex Activity
Types of Reflexes
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Somatic Reflexes
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Stretch reflexes
Golgi tendon reflexes
Flexor reflexes (withdrawal)
Crossed extensor reflexes
Superficial reflexes
Autonomic Reflexes
Stretch Reflex
Golgi Tendon Organ
Flexor reflex and Crossed
Extensor Reflex
Superficial Reflex