Anatomy of Cranial Nerves Flashcards
PNS division
-divided functionally into afferent sensory (impulses toward brain) and efferent motor (impulses away from brain)
- both sensory and motor are then divided into somatic (voluntary functions related to outside world) and visceral (involuntary functions related to internal viscera)
Somatic PNS
-voluntary
-both sensory and motor functions related to outside world
-detection of stimuli in skin and tissues and needed for locomotion, behaviour, expressions
Visceral PNS
-both sensory and motor functions related to internal viscera
-regulation of blood pressure, heart rate, glands, digestion, etc.
-motor component of visceral PNS= autonomic nervous system (ANS)
Division of afferent or sensory systems
1.general sensory
2.Special senses
General sensory
-senses of pressure, stretch, temperature, and noxious stimuli from tissues in body and head
-separated in general somatic afferent/sensory (GVA) and general visceral afferent/sensory (GVA)
General somatic afferent/sensory (GSA) receptors
-receptors in the skin informing stimuli from outside and in deeper somatic tissues informing movements of muscles and body parts relative to one another
General somatic afferent/sensory (GSA) nerve distribution
-found in all spinal nerves
-in cranial nerve V
General visceral afferent/sensory (GVA) receptors
-receptors in vessels, glands, and viscera of head and trunk informing stretch and chemical stimuli
General visceral afferent/sensory (GVA) distribution
-found in all spinal nerves
-found in cranial nerves III, V, VII, IX, X
Special senses
- Senses only found in head (vision, audition, taste, smell, and balance)
- Separated into special somatic afferent/sensory (SSA) and special visceral afferent/sensory (SVA)
Special somatic afferent/sensory (SSA)
-more restricted origin within certain special sense organs of head: retina of eye, cochlear, vestibular of inner ear
Nerves of special somatic afferent/sensory (SSA)
-Cranial nerve II
-cranial nerve VIII
Special visceral afferent/sensory (SVA)
-includes special senses of smell and taste
Nerves of special visceral afferent/sensory (SVA)
-found in cranial nerve I for smell
-found in cranial nerve VII and IX for taste
Division of efferent or motor system
-somatic efferent/motor
-visceral efferent/motor (Autonomic nervous system)
Somatic efferent/motor
-supply striated muscles
-in body and limbs and arise from somites
-in head arise from pharyngeal or branchial arches
- found in all spinal nerves and in all cranial nerves except those exclusively sensory nerves (I, II, VIII)
Exclusively sensory cranial nerves
I, II, VIII
Visceral efferent/motor (Autonomic nervous system)
- Supply smooth muscle of blood vessels, viscera, heart muscle, and glands
- Sympathetic and parasympathetic components
- Many ANS fibers travel to target organs by joining other nerves
Sympathetic and parasympathetic fiber locations
-sympathetic fibers leave spinal nerves in thoracolumbar regions of spinal cord
-parasympathetic fibers found in a small group of cranial nerves (III, VII, IX, X) and in spinal nerves in sacral region of spinal cord
Cranial nerves
-12 paris of cranial nerves
-numbered rostrocaudally
Where do cranial nerves originate from?
-originate from different regions of encephalon
>cerebrum I
>diencephalon II
> mesencephalon III, IV
>pons V
>medulla oblongata VI through to XII
Cranial Nerve Names
1.Olfactory
2.optic
3.oculomotor
4.trochlear
5.trigeminal
6.abducent
7.facial
8. vestibulocochlear
9.glossopharyngeal
10. vagus
11.spinal accessory
12.hypoglossal
Spinal nerves
-dorsal root only contains sensory fibers and ventral root only contains motor
-dorsal and ventral roots combine to form a single mixed spinal nerve
Cranial nerves
-dorsal root equivalents also contain some motor fibers
-dorsal and ventral root equivalents remain as separate cranial nerves
Divisions of cranial nerves
-nerves of special senses
-ventral root equivalents
-dorsal root equivalents
Nerves of special senses (cranial nerves)
-exclusively concerned with special senses
-cranial nerve I, II, VIII
Ventral root equivalents
-homologous with ventral spinal roots
-consist almost entirely of motor fibers
-supply striated head muscles of somatic origin
-move eye or tongue
-III, IV, VI, XII
Dorsal root equivalents
-homologous with dorsal spinal roots
-consist primarily of mixed fibers
-supply structures of pharyngeal arch origin
-V, VII, IX, X, XI
Olfactory nerve function
-special sense of smell
Olfactory nerve (I)
-multiple tracts
-nerves covered by meninges
-pass through olfactory foramina in cribriform plate of ethmoid
-also includes vomeronasal nerves (transmit sense of pheromones)
Optic Nerve (II) function
-special sense of vision
Optic nerve (II)
-nerve covered by meninges
-very large
-flexuous course through orbit to reach eye
What artery travels with optic nerve?
-internal ophthalmic artery travels with optic nerve
Oculomotor nerve (III)
-orbital fissure in dogs and horses/ orbitorotundum foramen in ruminants and pigs
-ventral root equivalent
Oculomotor nerve motor to:
-dorsal, ventral, medial recti
-ventral oblique
-levator of upper eyelid
-parts of retractor bulbi
Oculomotor nerve acts as Autonomic nervous system to:
-ciliary body to regulate lens
-iris to constrict pupil
Fissure of trochlear nerve (IV)
-orbital fissure in dogs and horses
-orbitorotundum foramen in ruminants and pigs
Trochlear nerve (IV)
-ventral root equivalent
-smallest cranial nerve
-motor to:
1.dorsal oblique
Trigeminal nerve (V) holes
-comes through orbital fissure (V1), round foramen (V2), and oval foramen (V3)
-technically comes out of round foramen but can only see it coming from rostral alar foramen
Trigeminal nerve (V)
-dorsal root equivalent
-largest cranial nerve
-3 main divisions
3 main divisions of trigeminal nerve (V)
1.opthalmic (V1)
2. Maxillary (V2)
3.Mandibular (V3)
Function of trigeminal nerve (V)
-V1 and V2 are sensory, V3 is mixed
-main sensory of head, including the rostral 2/3rd of tongue, and the sinuses
-motor to masticatory muscles
Masticatory muscles
-masseter
-temporalis
-pterygoids
-rostral belly of digastricus
Sensory of Ophthalmic branch of trigeminal nerve
-sensory to skin of forehead and most of the nasal cavity
Branches of ophthalmic nerve
-lacrimal nerve
-frontal nerve
-nasociliary nerve
Lacrimal nerve
-to the lacrimal glands and other deeper orbital structures, skin lateral to eye
Frontal nerve
-to the skin of upper eyelid, forehead, mucosa of frontal sinus, and provides alternative innervation of horns
Nasociliary nerve branches
-branches to long ciliary nerve, infratrochlear nerve, and ethmoidal nerve
Long ciliary nerve
-branches to cornea
Infratrochlear nerve
-to the medial angle of the eye, part of frontal sinus
Ethmoidal nerve
-re enters cranial cavity (via ethmoidal foramen), goes to nasal cavity (via cribiform plate) to medial and lateral walls of nasal cavity
Sensory of maxillary branch of trigeminal nerve
-sensory to skin of muzzle, face, mucosa of oral cavity, parts of nasal cavity and upper teeth
Branches of the maxillary branch of trigeminal nerve
-zygomatic nerve
-palatine nerve
-caudal nasal nerve
-cranial nasal nerve
-maxillary alveolar nerve
-infraorbital nerve
Zygomatic nerve
-to lower eyelid and adjacent skin
-gives rise to other branches including cornual nerve which is the main nerve for horns in cattle
Palatine nerve
-consisting of lesser palatine nerve to soft palate and greater palatine nerve to hard palate, and the floor of nasal cavity
Caudal nasal nerve
-via pterygopalatine foramen
- to the ventral nasal cavity and maxillary sinus
Cranial nasal nerve
-to ventral part of nasal cavity
Maxillary alveolar nerve
-to all teeth of upper jaw
Infraorbital nerve
-into maxillary foramen and out of infraorbital foramen
-Towards the muzzle
Sensory of the mandibular branch of the trigeminal nerve
-sensory to parts of face and motor to muscles of mastication
Sensory branches of the mandibular nerve (of trigeminal nerve)
-buccinator nerve
-mandibular alveolar nerve
-mental nerve
-lingual nerve
-auriculotemporal nerve
Buccinator nerve
-also called buccal nerve
-sensory to buccal mucosa and facial skin
Mandibular alveolar nerve
-innervates lower teeth
Mental nerve
-is terminal part of mandibular alveolar nerve exiting mental foramen, to the chin and lower face skin
Lingual nerve
-relays general sensation (not taste) of rostral 2/3rds of tongue
Auriculotemporal nerve
-innervates the ear and temporal region, and areas extending to corner of mouth
Motor regions of the mandibular branch of trigeminal
-goes to masseter, temporal, pterygoid muscles, cranial belly of digastricus and other branches of the mylohyoideus
Nerve blocks of trigeminal in horse
1.target infraorbital nerve (
2. target inferior alveolar nerve
3. target mental nerve
Abducent nerve (VI)
-ventral root equivalent
-motor to lateral rectus, and retractor bulbi
Facial nerve (VII)
-dorsal root equivalent
-motor to muscles of facial expression
-sensory from skin inside ear
-taste from palate and rostral 2/3rd of tongue
Facial nerve and Autonomic nervous system
-facial nerve linked to lacrimal glands, and sublingual and mandibular salivary glands
Vestibulocochlear nerve (VIII)
-special senses of hearing and balance
-entirely within bones of the skull
Cranial nerves IX, X, XI
-pass through jugular foramen
> but visible external opening in dog is tympano-occipital fissure
> jugular foramen is continuous with the foramen lacernum in horse and pig
Glossopharyngeal nerve (IX)- sensory, motor, ANS?
-dorsal root equivalent
-Sensory from primary nerve for sensation from pharynx, and caudal 1/3rd of tongue
-Taste from caudal 1/3rd of tongue
-Motor to stylopharyngeus
-Autonomic nervous system to parotid and buccal salivary glands, and carotid sinus and body
Vagus nerve (X)- sensory, motor, ANS?
-dorsal root equivalent
-sensory from pharynx, larynx, parts of external ear, most viscera
-motor to pharyngeal muscles, laryngeal muscles
-Autonomic nervous system to most viscera
Accessory nerve (XI)
-dorsal root equivalent
-motor to brachiocephalicus, omotransversarius, trapezius, sternocephalicus
Hypoglossal nerve (XII)
-comes through hypoglossal canal
- ventral root equivalent
-motor to intrinsic and extrinsic muscles of the tongue
