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Cranial Nerves, Chapter 19 Objectives, Chapter 21 Objectives, Chapter 22…
Cranial Nerves
Cranial nn. (12)
I: Olfactory
what type of nerve is it
sensory
function
Conducts information from nasal chemoreceptors to the olfactory bulb
what happens to the signals from the olfactory bulb (travels to 3 places)
two areas in the medial temporal lobe
travel in the olfactory tract directly to the primary olfactory cortex
where is the primary olfactory cortex
in the insula
insula functions (3)
1 more item...
where are the olfactory cells
in the cribriform plate
where is it located and what does it do
a portion of the ethmoid bone located at the base of the skull, that allow for the passage of the olfactory nerves to the roof of the nasal cavity
what happens to the cells here during s TBI
they often sheer, which causes pts to have anosmia
what is anosmia
inability to sense smell
they are essentially the same thing as what
nasal chemoreceptors
what 3 things can interfere with the function of the olfactory n.
TBI, smoking, excessive nasal mucus
what would occur if there was a lesion to olfactory n.
can result in an inability to detect smells
where is the connection to the brain
inferior frontal lobe
II: Optic
function
allow visual info to be moved from the retina to the occipital lobes
Pathway of visual information from visual receptors (5 steps)
cells in the retina convert light into neural signals
signals are processed within the retina and are conveyed to the retinal output cells that are located at the end of the retina
The retina output cells project their long axons to form the optic nerve, which convey the signals to the thalamus
what area in the thalamus
lateral geniculate nucleus (LGN)
the optic n. synapse with neurons in the lateral geniculate body, and the axons of those neurons then form the optic radiation
what is the optic radiation
aka what other 3 things
1 more item...
bundle of n. fibers (specifically white mater tract) that convey optic info from optic chiasm to visual cortex
the optic radiation neuron then convey the info to the primary visual cortex in occipital lobes
Info goes to 2 places
3 more items...
what other two areas does the visual info go to other than thalamus
superior colliculus
what output occurs once the info gets here (2)
1 more item...
pretectal area
what output occurs once the info gets here
1 more item...
where is this located
1 more item...
info from the right visual fields go where
the left side of the retina and vice versa
info from the nasal half of each retina do what
crosses the midline in the optic chiasm and projects to the contralateral visual cortex
Information from the temporal half of each retina does what
continues ipsilaterally through the optic chiasm and projects to the ipsilateral cortex
where is the connection to the brain
diencephalon
Disruption of visual flow
what occurs with a peripheral optic n. lesion on the right side before the optic chiasm
both visual fields on the right would be out, both visual fields on the left would be fine
what occurs with a lesion at the optic chiasm
the temporal halves of the right and left visual fields would be out, but the nasal halves would be fine
what is this condition called
Bitemporal Hemianopia
what occurs with an optic n. lesion on the right side after the axons crossed in the optic chiasm
there would be loss of vision on both left halves of both eyes
what is this condition called
Homonymous Hemianopia
what occurs with an optic n. lesion on the right side at the optic radiation
there would be loss of vision on both left halves of both eyes
what is this condition called
Homonymous Hemianopia
III: Oculomotor
IV: Trochlear
V: Trigeminal
what type of n. is it (3)
somatosensory
functions (8)
afferents for touch, proprioceptive, nociceptive, and temp from the face, anterior 2/3 of the tongue, sinuses, teeth, and meninges
motor
function (2)
efferents to mm. of mastication and tensor tympani m.
what are the mm. of mastication (4)
temporalis, masseter, medial and lateral pterygoid
what is the tensor tympani m.
middle ear muscle that adjusts the tension of
the eardrum to protect the inner ear
reflex
function
afferent limb corneal reflex
what is the corneal reflex
protective response that causes the eyelids to close involuntarily when the cornea is stimulated
what is the efferent limb of the corneal reflex
1 more item...
which trigeminal branch is responsible for this
1 more item...
3 branches :red_cross:
Ophthalmic (VI)
what is an important function
it is the afferent limb corneal reflex
Maxillary (V2)
Mandibular (V3)
what will occur if this branch is severed
the jaw will deviate toward the involved side when the mouth is opened
function (2)
contains motor axons to the muscles used in chewing and the
tensor tympani & sensory of lower face (includes part of the ear)
what is the tensor tympani m.
middle ear muscle that adjusts the tension of
the eardrum to protect the inner ear
what part of the ear does it give sensory innervation to
what will occur if a branch is severed
anesthesia of the area supplied by the ophthalmic, maxillary, or mandibular branch
4 nuclei
motor
function
aids in mastication by tensor tympani m.
how does the tensor tympani m. aid in mastication
by reducing the audibility of sounds made while chewing
mesencephalic
function
proprioception
main sensory
function
light touch
pathway (4 steps)
light touch sensation that is detected by trigeminal ganglion
trigeminal ganglian synapses w the main sensory nucleus (1st synapse) & crosses over in pons
1 more item...
spinal
function
nociception
pathway (4 steps)
1.fast nociception sensation that is detected by trigeminal ganglion
trigeminal ganglian synapses w the spinal trigeminal nucleus (1st synapse) & crosses over in lower medulla
1 more item...
where does this nuclei come from
the substantia gelatinosa in the posterior horn of the spinal cord
where is the connection to the brain
lateral pons
what can lesions cause (3)
loss of sensation on the face, impaired chewing, and a reduced corneal reflex
VI: Abducens
VII: Facial
function (5 types)
motor function (2)
innervates the muscles of facial expression and stapedius m.
where is the stapedius m. and what does it do
located in the middle ear and responsible for reducing the vibrations caused by loud noises
Somatosensory function (2)
Afferents for sensation from anterosuperior ear & external ear canal
reflexive function
efferent limb of corneal (blink) reflex
Visceral function
afferents for taste from anterior 2/3 of tongue
Parasympathetic function (3)
efferent to lacrimal, nasal, and all salivary glands
which salivary gland does it not innervate
parotid salivary gland
4 nuclei
Facial nucleus
function
Primarily responsible for controlling facial expressions by innervating the muscles of the face
Cortical control of muscles in the upper face is what
bilateral
this is caused by which tracts
1 more item...
Cortical control of muscles in the lower face is what
contralateral
this is caused by which tracts
1 more item...
so does the right motor cortex influence movements of the right side of the lips
1 more item...
Lesions
Peripheral lesion
what will occur
1 more item...
Central lesion
what will occur (2)
1 more item...
when does this usually occur
1 more item...
Salivatory nucleus
function
Provides parasympathetic innervation to the submandibular and sublingual salivary glands
solitary nucleus
function
Receives taste information from the anterior two-thirds of the tongue
spinal nucleus of CN V
function
Contributes to general sensation of the face, although not exclusively part of the facial nerve
where are they located
where is the connection to the brain
between pons and medulla
what can lesions cause (3)
Bell’s palsy, loss of taste (anterior 2/3 of tongue), and decreased saliva and tear
VIII: Vestibulocochlear
where is the connection to the brain
between pons and medulla
what type of nerve is it
sensory
when there's optimal sensory-motor integration, what 3 optimal coordination patterns result
balance control
eye-tracking
grasping control
when there's sub-optimal sensory-motor integration, what 3 sub-optimal coordination patterns can result
delays in info transmission
delayed rxns
altered synergistic patterns of m. activation & force production
what can all of this lead to (2)
recurring traumatic episodes and MSK injuries
2 branches :red_cross:
Vestibular branch :red_cross:
function :red_cross:
transmits information regarding head position with respect to gravity and head movement
what is vestibular info essential for (2) :red_cross:
postural control and control of eye movements
the axial skeleton is inherently known to be what :red_cross:
2 more items...
how does the vestibular system do this :red_cross:
vestibular appartaus, in inner ear, converts the info into neural signals from vestibular n. to vestibular nuclei
where is the vestibular nuclei :red_cross:
1 more item...
Projections from the vestibular nuclei contribute to what 4 things
:red_cross: :
1 more item...
central vestibular system :red_cross:
what is apart of it :red_cross:
4 vestibular nuclei :red_cross:
where are they located
bilaterally at the junction
of the pons and the medulla, near the fourth ventricle
lateral vestibular nuclei :red_cross:
aka
1 more item...
medial vestibular nuclei
inferior vestibular nuclei :red_cross:
aka
1 more item...
superior vestibular nuclei
what other info does the nuclei rceeive other than vestibular (4) :red_cross:
visual, auditory, proprioceptive, and tactile
1 more item...
6 pathways :red_cross:
medial longitudinal fasciculus
provides what connections (4)
1 more item...
vestibulospinal tracts
description
1 more item...
vestibulocolic pathways
where does the info go and what does it influence
1 more item...
2 types
2 more items...
vestibulothalamocortical pathways
what does this provide (3)
1 more item...
vestibulocerebellar pathways
what does this control
1 more item...
where does the info go
1 more item...
vestibuloreticular pathways
what does it influence (2)
1 more item...
where does the info go
1 more item...
vestibulocerebellum :red_cross:
description
section of the cerebellum that receives vestibular information
1 more item...
vestibular cortex :red_cross:
what output occurs once information is given here :red_cross:
concious awarenss of head position and movement
1 more item...
where is it located :red_cross:
parietal cortex within the posterior pan of the lateral fissure
once the head stimuli hits the semicircular canals and/or otolithic organs, what 2 places does the info go
:red_cross:
vestibular nuclei and vestibulocerebellum
what 3 places does the info go after
vesticular cerebral cortex
1 more item...
oculomotor nuclei
1 more item...
spinal cord
1 more item...
which one does the info has to b sent to the thalamus first
1 more item...
Motor control
how does the vestibular system contribute to motor control (2)
gaze stabilization
postural adjustments
Disorders :red_cross:
2 types :red_cross:
Peripheral vestibular disorders :red_cross:
what do they typically cause (3) :red_cross:
recurring periods of vertigo, accompanied by moderate to severe nausea
1 more item...
diminished hearing and/or tinnitus
1 more item...
different types (5) :red_cross:
Benign Paroxysmal Positional Vertigo (BBPV) :red_cross:
3 more items...
vestibular neuritis
Meniere's disease :red_cross:
2 more items...
traumatic injury
perilymph fistula :red_cross:
2 more items...
Central vestibular disorders :red_cross:
these disorders result from
damage to the vestibular
nuclei or their connections within the brain
common causes
ischemia or a tumor in the brainstem/cerebellar region, cerebellar degeneration, MS, or Arnold-Chiari malformation
does they produce worst symptoms than peripheral vestibular disorders
:red_cross:
no, they are usually more mild symptoms
1 more item...
what is a significant difference from peripheral vestibular disorders
1 more item...
Unilateral lesions that interfere with the vestibular nuclei or their cerebellar can produce what disorder :red_cross:
CPPV (central paroxysmal positional vertigo
1 more item...
Rehabilitation
this can be affective for which disorders (3)
BPPV, unilateral vestibular loss or
dysfunction, and bilateral vestibular loss
rehabilitation does not affect which disorders (2)
central dysfunctions of the vestibular system, nor is it effective
for active Menieres disease
describe the visual-vestibular interaction in the cerebral cortex :red_cross:
they are inhibitory
what does this mean
increased visual cortex activity inhibits the vestibular cortex and increased vestibular cortex activity inhibits the visual cortex
Cochlear branch
function
transmits information related to hearing
how does it do that
by transfering mechanical waves to sound
where is it located
in the labirinth
where is this and function :red_cross:
the innermost part of the ear that contains the organs of hearing and balance
which 3 inputs does balance depend on
visual inputs
vestibular inputs
proprioceptive inputs
which input works the fastest
vestibular
which is the slowest
1 more item...
what are the different parts of the labirinth (6)
semicircular canals
description :red_cross:
three hollow rings arranged perpendicular to each
other, w each canal opening at both ends into the utricle
what do the receptors do
detect movement of the
head by sensing the motion of endolymph
what is endolymph
1 more item...
what occurs when the head turns towards the right at the beginning
1 more item...
what does each canal have :red_cross:
a swelling at the end called the ampulla
what does it contain
1 more item...
what are the 3 canals :red_cross:
horizontal :red_cross:
detects what type of movements
1 more item...
when is this canal parallel to the ground :red_cross:
1 more item...
anterior :red_cross:
how is it positioned :red_cross:
1 more item...
detects what type of movements
1 more item...
posterior
how is it positioned
1 more item...
detects what type of movements
1 more item...
how are they positioned relative to each other
at 90 degree angles
utricle
oval window
saccule
cochlea
what is it
Snail shell–shaped auditory organ formed by a spiraling, fluid-filled tube
how many canals does it have
3
what are the type of receptor cells
hair cells
what are the 2 membranes
tectorial membrane
mobile or immobile
1 more item...
basilar membrane
mobile or immobile
1 more item...
what rests on the basilar membrane
1 more item...
vestibulocochlear n.
which are known to be the otolithic organs :red_cross:
saccule
how is the macula orientated
vertical (when does it respond maximally)
1 more item...
what do the otolithic organs do (2) :red_cross:
respond to head position relative to gravity and to linear acceleration and deceleration
examples (3)
1 more item...
how does this occur
1 more item...
what is in each of these sacs
a macula (what does it consist of (3 things))
hair cells enclosed by a gelatinous mass topped by calcium carbonate crystals
1 more item...
utricle
how is the macula orientated
horizontal (when does it respond maximally)
2 more items...
pathway of sound
sound waves strike eardrum
what is the eardrum also called
tympanic membrane
Ossicles move, causing vibration of membrane at opening of the upper chamber
what are ossicles
three small bones in the middle ear that transmit sound vibrations from the eardrum to the inner ear
Fluid moves into upper chamber
Basilar membrane and attached cells vibrate
Hair bend and depolarize
why do the hairs bend
1 more item...
Cochlear n. ending activate
1 more item...
what is the basilar membrane
stiff structural element within the cochlea of the inner ear which separates two liquid-filled tubes
1 more item...
what can lesions cause (3)
hearing and balance, causing vertigo, dizziness, and hearing loss
IX: Glossopharyngeal
where is the connection to the brain
medulla
what type of functions does it have (5)
somatosensory
function (4)
afferents from the pharynx, posterior 1/3 of tongue, middle ear, and area near external ear canal
motor
function
efferent to one m. in the pharynx
which muscle
stylopharyngeus m.
visceral
function (2)
afferents for taste of posterior tongue
BP and chemical info from the carotid artery
parasympathetic
function
efferent to parotid gland
what is the parotid gland
a major salivary gland located in front of and below each ear
reflex
function
afferent limb of the gag and swallowing reflexes
what can lesions cause (4)
Lesions impact swallowing, taste, and saliva production; a reduced gag reflex is also common
X: Vagus
where is the connection to the brain
medulla
what type of functions does it have (5)
Somatosensory
function (3)
afferents from pharynx, larynx, and skin in center of external ear
motor
function (2)
efferents to muscles of the pharynx and larynx
visceral
function (4)
afferents from the pharynx, larynx, thorax, and abdomen
parasympathetic
function (4)
efferents to smooth muscles and glands in the pharynx, larynx, thorax, and abdomen
what are the specific 3 vaga parasympathetic functions
decrease HR, construct bronchi, and stimulate digestion
reflex
function
efferent limb of the gag and swallowing reflexes
it has afferents and efferents for which specific structures (9)
heart, lungs, trachea, bronchi, larynx, pharynx, gastrointestinal system, liver, and pancreas
what type of n. is it (3)
mixed n., consisting of sensory, motor, and autonomic axons
what does it do overall
Activation of all muscles involved in swallowing and vocalization
Phases of swallowing (3 stages)
Oral (5 steps)
1, Found in mouth, lips close
which cranial n. does this
7
Jaw, cheek, and tongue movements manipulate food
Tongue move food to pharynx entrance
which cranial n. does this
12
Larynx closes
which cranial n. does this
1 more item...
Swallow reflex triggered
1 more item...
which cranial n. does this (3)
5,7,12
Pharyngeal/laryngeal (4 steps)
Food moves in pharynx
which cranial n. does this
9
soft palate rises to block food from nasal cavity
which cranial n. does this
10
epiglottis covers trachea to prevent food from entering lungs
which cranial n. does this
10
Peristalsis moves food to entrance of esophagus, sphincter opens, food moves into esophagus
which cranial n. does this
1 more item...
Esophageal (1 step)
Peristalsis moves food into stomach
which cranial n. does this
10
what can lesions cause (4)
Lesions may cause dysphagia, hoarseness, digestive issues, and potential life-threatening effects on heart rate
XI: Accessory
where is the connection to the brain (2)
spinal cord and medulla
what type of n. is it
pure motor
which mm. does it innervate (2)
SCM and traps
where does the n. originate
in the spinal accessory nucleus in the upper cervical cord
where does it go from there
travels upward through the foramen magnum (where does it go after)
leaves the skull through the jugular foramen
where are the cell bodies
in the ventral horn at levels C1 - C4
what can lesions cause (2)
Lesions lead to shoulder droop and weakness in head-turning.
XII: Hypoglossal
where is the connection to the brain
medulla
what type of n. is it
motor
what mm. does it innervate
intrinsic and extrinsic muscles of the tongue
ipsilateral or contralateral tongue
ipsilateral
where are the cell bodies
hypoglossal nucleus
where is that
in the medulla
what can lesions cause (2)
Lesions cause tongue deviation to the affected side and difficulty with speech and swallowing
which 3 nn. control the mm. that move the eye :red_cross:
The oculomotor (CN-III)
this n. also has which 2 functions
controls reflexive constriction of the pupil and adjusts the lens of the eye
is oculomotor nerve the efferent or afferent limb for pupil restriction
efferent (whats the afferent limb)
optic n.
does the optic n. and oculomotor n. cause the reflex ipsilaterally or contralaterally
they both do both (ipsilaterally and contralaterally)
what nucleus allows these functions to occur
parasympathetic nucleus of the ocularmotor nerve
function (2)
innervates the ciliary muscles
what do they do
1 more item...
constricts the pupil by innervating the smooth muscle (sphincter pupillae) near the pupil
Pathway of the pupillary light reflex
2 more items...
Innervated which 4 mm.
superior rectus, inferior rectus, medial rectus, inferior obique
where is the connection to the brain
anterior midbrain
Eye Movements
Vestibulo-ocular reflex
abbreviation
VOR
description
stabilize visual images during head movements
where are the vestibular receptors for the VOR reflex
semicircular canals
which canal is stimulated when face tilts down
anterior
1 more item...
how many canals are there
3
which canal is stimulated when face tilts up
posterior
1 more item...
which canal is stimulated when face turns left or right
horizontal
1 more item...
Optokinetic Nystagmus
description
adjusts eye position in order to keep an
image stable on the retina during slow, sustained head movements
when can this also occur
when the head is stable
and the environment is moving
what does optokinetic mean
the reflex. is elicited by moving visual stimuli (usually large)
what does nystagmus involve
involuntary oscillating movement of the eyes
what is Physiologic nystagmus
normal response that can be elicited
in an intact nervous system
what 3 things can trigger this response
when does pathological nystagmus occur
with disorders of the eye movement system, so sign of a nervous system abnormality
what do you usually see
1 more item...
Saccades
description
eyes quickly shift the gaze from one object to another
example
person is reading and someone comes into the room, a saccadic
eye movement shifts the reader's gaze from the text to the person
Smooth pursuit eye movements
description
eyes follow a moving
object (usually small)
Vergence
what occurs
the eyes align on a near or far target
what type of movement is this
voluntary disconjugate
1 more item...
all of these eye movements are conjugate except for which one
vergence
what does conjugate mean
both eyes move in the same direction
Autonomic innervation to the eye
where are the cell bodies of a 3-neuron path to innervate the upper eyelid and iris (3 places)
lateral hypothalamus
T1 spinal segment
superior cervical ganglion
what type of innervation is it
sympathetic
which smooth m. innervates the upper eyelid
superior tarsal m.
what does it do
Weakly assists levator palpebrae superioris in raising the upper eyelid
2 more items...
which smooth m. innervates the iris
dilator m.
what does it do
dilates the pupil
what type of nn. are they
primarily motor
which mm. do they innervate (6)
Inferior rectus
Innervated by
Oculomotor (CN-III)
function
Moves the eye downward, or depresses it
Superior rectus
Innervated by
Oculomotor (CN-III)
function
Moves the eye upward, or elevates it
Medial Rectus
Innervated by
Oculomotor (CN-III)
function
Moves the eye inward, or toward the nose
Inferior oblique
Innervated by
Oculomotor (CN-III)
function
Rotates the top of the eye away from the nose, or extorts it
Lateral rectus
Innervated by
Abducens (CN-VI)
function
Moves the eye outward, or away from the nose
Superior oblique
Innervated by
Trochlear (CN-IV)
function
Rotates the top of the eye toward the nose, or intorts it
what are these mm. called
extraocular mm.
Trochlear (CN-IV)
innervates which m.
Superior oblique
where is the connection to the brain
posterior midbrain
Abducens (CN-VI)
innervates which m.
Lateral rectus
where is the connection to the brain
between pons and medulla
Coordination
eye coordination requires what
connections among the cranial nerve nuclei that control eye movements.
what has to happen to look towards the right (3 steps)
the right abducens nerve activates the lateral rectus to move the right eye laterally
a brainstem tract then conveys a signal from the right abducens nucleus to the left oculomotor nucleus
what is this brainstem tract called
the medial longitudinal fasciculus (MLF)
Signals conveyed by the MLF do what
1 more item...
left oculomotor nerve then activates the medial rectus to move the left eye to the right
does the R or L cortex create the signal to the R abducens n.
Right cerebral cortex
Only which 4 nn. contain autonomic axons
3, 7, 9, 10
Innervation of external ear
anterosuperior and anterior auditory canal
what n. innervates
5
center
what n. innervates
10
posteriorinferior
what n. innervates
spinal n. C2
posterior auditory canal
what n. innervates (3)
7,9,10
prominence anterior and the auditory canal
what n. innervates (2)
10 and spinal n. C2
which cranial n. is the only one that signals do not go thru the thalamus
1 (olfactory)
why
because it bypasses the thalamus and transmits information directly to the olfactory cortex in the brain
Fundamental Info
are cranial nn. apart of PNS or CNS
PNS
Functions (4)
Supply motor innervation to muscles of the face, eyes, tongue, jaw, and the two superficial neck muscles (SCM and traps)
Transmit somatosensory information from the skin and muscles of the face and the temporomandibular joint.
Transmit special sensory information related to visual, auditory, vestibular, gustatory, olfactory, and visceral sensations
Provide parasympathetic regulation of pupil size, curvature of the lens of the eye, heart rate, blood pressure, breathing, and digestion
Chapter 19 Objectives
List the four functions ofthe cranial nerves.
2.1dentify each cranial nerve by number, name, function(s), reflex activity (if any), and connection to the brain.
3.1dentify the deficits associated with lesions to CNs 1, 5, and 7 to 1 2.
4.1dentify the cranial nerve that can transmit information directly to the cortex, bypassing the thalamus.
Describe the pathways for transmitting sensory information from the face.
Describe Bell's palsy.
Distinguish between the effects of cortical or motor tract lesion on facial muscles and the effects of facial nerve
lesions.
Describe the process of converting mechanical waves into sound.
List the stimulus, receptor, afferent limb, efferent limb, and response for the corneal reflex and fur the gag reflex.
Chapter 21 Objectives
Identify major structures involved in capturing, transmitting and interpreting visual images
Identify the cranial nerves (CNs) 2, 3, 4, and 6 by name, function(s), reflex activity, and connection to the brain.
Describe the visual pathway conveying signals from the retina to the thalamus and cortex.
Describe the locations of lesions causing bitemporal hemianopia, homonymous hemianopia, monocular blindness, and cortical blindness.
List the six extraocular muscles, their innervations, and their actions.
Describe the stimulus, receptor, afferent limb, synapse(s), efferent limb, and response for the pupillary and accommodation reflexes.
Describe the vestibulo-ocular reflex and the optokinetic response and their purposes.
Compare physiologic with pathologic nystagmus.
Define saccades and give an example.
Compare conjugate with vergence eye movements.
Describe the autonomic innervation of the eye and eyelid.
Chapter 22 Objectives
Identify the four functions of the vestibular nuclei.
Describe the anatomic arrangement of the three semicircular canals and their relationship to the horizontal plane.
Describe the two otolithic organs.
List the movements detected by the semicircular canals and otolithic organs.
List the structures constituting the peripheral and central vestibular systems.
Explain the role of the vestibular system in motor control.
Compare peripheral and central vestibular disorders and give examples of each.
Describe the inhibitory visual-vestibular interaction in the cerebral cortex.
Explain how to differentiate between vestibular, cerebellar, and sensory ataxia.
Describe the indications and associated procedures for caloric testing, rotatory chair testing, and electronystagmography.
Describe the effectiveness of rehabilitation for various vestibular pathologies.