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The Peripheral Nervous System. Chapter 13. Divisions of the Nervous System. By Stimulus Type Mechanoreceptors Thermoreceptors Photoreceptors Chemoreceptors Baroreceptors Nociceptors. By Location Exteroceptors Interoceptors Proprioceptors. Classification of Sensory Receptors.
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The Peripheral Nervous System Chapter 13
By Stimulus Type Mechanoreceptors Thermoreceptors Photoreceptors Chemoreceptors Baroreceptors Nociceptors By Location Exteroceptors Interoceptors Proprioceptors Classification of Sensory Receptors
Types of Nerves • Sensory (afferent) Nerves • Motor (efferent) Nerves • Mixed Nerve (both)
Cranial Nerves • 12 pairs • Classified as sensory, motor or mixed • First two pairs attach to the forebrain • Remaining ten pairs attach to the brainstem
Olfactory Nerve (I) • 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) • 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) • Motor only • Controls 4 of the six eye muscles for eyeball movement and pupil constriction: • Superior rectus • Medial rectus • Inferior rectus • Inferior oblique • External Strabismus=eye rotates laterally
Trochlear Nerve (IV) • 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) • 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) • Motor only • Innervates the lateral rectus muscle of the eye • Moves eyeball laterally • Internal Strabismus=eye rotates medially
Facial Nerve (VII) • 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) • 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) • 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) • 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) • Motor (primarily) • Innervates trapezius and sternocleidomastoid muscle • Damage would result in the inability to shrug the shoulders and turn the head
Hypoglossal Nerve (XII) • Motor (primarily) • Tongue movements: swallowing and speech
Spinal Nerves • 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
Cervical Plexus • 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 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