Lecture 7 Flashcards
What is CN I?
Olfactory Nerve
What nerve number is the olfactory nerve?
CN I
What kind of nerve (sensory/motor) is CN I?
The Olfactory Nerve is pure sensory
What is the function of the Olfactory Nerve CN I?
Olfaction
Where does CN I carry inputs?
Olfactory tracts carry axons directly to the primary olfactory cortex, bypassing the thalamus
Why does the olfactory nerve bypass the thalmus?
An evolutionary adaptation
After reaching the primary olfactory cortex, where do CN I nerves go?
Amygdala (emotional response to smell)
Hippocampus (memory of smell)
Hypothalamus (visceral response to smell)
What is the second order neuron in the Olfactory (CN I) pathway?
The Olfactory tract
Where is the primary olfactory cortex found?
In the Uncus or the Parahippocampal Gyrus
What is found in the Uncus or the Parahippocampal Gyrus?
The primary olfactory cortex
Which CN nerves sense taste?
VII - Facial
IX - Glossopharyngeal
What is CN VII?
The facial nerve
What number is the facial nerve?
CN VII
What number is the Glossopharyngeal nerve?
CN IX
What is CN VII?
Facial nerve
What nerve is CN IX?
Glossopharyngeal
What nerve controls movement of the tongue?
Hypoglossal Nerve (XII)
What does Hypoglossal Nerve (XII) do?
Controls the movement of the tongue
Where does the Hypoglossal Nerve (XII) origniate?
The medulla
Where does the Hypoglossal (XII) nerve exit the skull?
Hypoglossal canal
What exits the Hypoglossal (XII) Canal?
The Hypoglossal nerve
What kind of nerve (sensory/motor) Hypoglossal nerve (XII)?
A pure motor
What muscle does the Hypoglossal Nerve (XII) inervate??
Genioglossus muscle
What nerve innervates the Genioglossus muscle?
Hypoglossal Nerve (XII)
What is the main muscle of the tongue?
The Genioglossus muscle
What innervates the Genioglossus muscle?
Hypoglossal Nerve XII
What is the innervation of the tongue like?
It is innervated by the Hypoglossal Nerve XII ipsilaterally. If there is a lesion, the tongue deviates to the same side as the lesion
What number nerve is the Glossopharyngeal nerve?
IX
What is nerve IX?
Glossopharyngeal
What number is the Trigeminal nerve?
CN V
What is cranial nerve V?
Trigeminal Nerve
What supplies touch for posterior 2/3 of the tongue?
CN IX - Glossopharyngeal
What supplies touch for anterior 2/3 of the tongue?
CN V3 - Trigeminal
What supplies the touch of the tongue?
*Glossopharyngeal (CN IX) posterior 2/3
*Trigeminal (CN V) anterior 2/3
What supplies taste to the posterior part of the tongue?
Glossopharyngeal nerve CN IX
What supplies taste to the anterior 2/3 of the tongue?
The Facial Nerve CN VII
What supplies taste to the tongue?
*Glossopharyngeal nerve CN IX - posterior
*Facial nerve CN VII CN VII - anterior
What nerve pushes food to the back of the tongue?
The hypogloassal nerve CN XII
What innervates the posterior 1/3 of the tongue?
The Glossopharyngeal nerve
What part of the Trigeminal nerve CN V supplies touch for the anterior 2/3 of the tongue?
V3 the mandibular branch
Where does the Glossopharyngeal nerve exit?
The Jugular foramen
What exits the Jugular foramen?
*CN Hypoglossal IX
*Vagus X
*Spinal Accessory XI
*The sinuses
What does the whole Trigeminal nerve (V) supply?
The sensory innervation of the entire face and the anterior 2/3 of the tongue
What are the three branches of the Trigeminal Nerve V?
*Ophthalmic nerve (V1)
*Maxillary nerve (V2)
*Mandibular nerve (V3)
Which nerves does the Facial nerve join with when it exits?
The the vestibulocochlear nerve
What exits the Internal Acoustic Meatus?
Facial nerve VII and the Vestibulocochlear nerve VIII
Where does the facial nerve VII exit?
The internal acoustic meatus
What initiates the swallowing reflex?
The sensation of food felt by the Glossopharyngeal nerve (CN IX)
What does the Glossopharyngeal nerve (CN IX) do for the tongue?
Taste and sensation for the anterior 1/3 of the tongue
What is the Chorda Tympani?
The branch of facial nerve VII that supplies taste to the anterior 2/3 of the tongue
How does taste work?
Tastes activate taste buds that are neuroepithelium these in turn activate CN VII (facial) or IX (glossopharyngeal)
What is the pathway of taste?
An action potential sends information along the lingual nerve in the anterior 2/3 of the tongue, where it reaches the geniculate ganglion and goes to the nucleus of the solitary tract in the brainstem. In the posterior 1/3 of the tongue, it will travel along the glossopharyngeal nerve to the inferior ganglion and also reach the nucleus of the solitary tract. Then goes up the spinal cord to the thalamus and synapses at the VPM nucleus of the thalamus and then to the postcentral gyrus
How many neurons are in the taste pathways?
Three neurons
Where do the collateral branches of the taste pathway go?
The amygdala and the hippocampus
What nucleus in the thalamus does the taste pathway synapse on?
The Ventropostermedial (VPM) nucleus of the thalamus
What nerves are involved in hearing and balance?
*CN VIII (Vestibulocochlear nerve)
*CN VII (Facial nerve)
*V (Trigeminal nerve)
How does the Facial nerve VII help with hearing?
Controls the stapedius muscle
How does the Trigeminal nerve help with hearing?
Controls the tensor tympani muscle
What is CN VIII?
Vestibulocochlear nerve
What kind of nerve (motor/sensory) is the Vestibular nerve VIII?
Pure sensory
Where are the Vestibular and Cochlear nuclei found?
Between the pons and the medulla
What does the vestibular component allow for?
Us to know where our head is in space
Why is the the facial nerve prone to compression?
During an ear infection the tissue that transverse the acoustic meatus together with the VIIIth nerve, it is prone to compression if there is inner ear infection
What are the divisions of the inner ear?
The cochlea and the semicircular canals
What are the three canals in the cochlea?
*Scala vestibuli
*Scala tympani
*Cochlear duct
What fluid is contained in the Scala vestibuli and tympani?
Perilymph
What fluid is contained in the cochlear duct?
Perilymph
How does hearing work?
- Sound vibrates the tympanic membrane
- It connects to the malleus, incus and stapes
- These connect to the round window and move the fluid in the ducts
- This causes the stereocilia on the organ of corti to rub on the tectorial membrane causing an action potential
What is the ganglion for CN VIII (vestibulocochlear)?
The spiral ganglion
What CN does the Spiral ganglion connect with?
CN VIII Vestibulocochlear
What is the auditory pathway in the brain?
- CN VIII (vestibulocochlear) nerve goes to the spiral ganglion
- They synapse in the brainstem at the cochlear nuclei
- From there both the left and right go up both sides of the brainstem
- It then synapses of the Medial Geniculate nucleus of the thalamus
- And then ends at Heschl’s gyrus (the primary auditory cortex)
Where does the Auditory pathway end?
The Primary Auditory Gyrus (Heschel’s gyrus)
Where does the primary auditory cortex synapse?
*Cochlear nuclei
*Medial Geniculate Nucleus (MGN)
Where in the thalamus does the auditory pathway synapse?
The Medial Geniculate Nucleus
What synapses at the Medial Geniculate Nucleus?
The auditory pathway
Where is hearing understood?
Wernicke’s Area
Describe the hearing reflex?
We turn to face something when we hear it because the auditory nerves pass through the inferior colliculus which innervates the neck muscles
How do we know where a sound is coming from?
Bilateral auditory pathways provide cues to localize sound in space - brain uses interaural time difference as one cue to localize sound in space
What is the pitch mapping of the cochlea?
Hair cells that are closer to the beginning bend at higher sounds
Where do Perception and Comprehension of hearing occur?
*Perception - Primary Auditory Cortex (Heschl’s gyri)
*Comprehension - Wernicke’s sensory speech area
What kind of nerve is the Vestibulocochlear Nerve (VIII)?
It is pure sensory
What nerves dampen sound in the ear?
*Facial Nerve (VII)
*Trigeminal Nerve (V)
How does the facial nerve (VII) dampen sound?
It innervates the stapedius muscle which attaches to the ossicles
How does the Trigeminal (V) nerve dampen sound?
It innervates the tensor tympani muscle which attaches to the ossicles
What are the components of the Vestibular system?
*Saccule
*Utricle
*3 Semicircular canals
Where is the perilymph found in the vestibular apparatus?
In the Bony labyrinth
Where is the endolymph found in the vestibular apparatus?
In the Membranous labyrinth
What are the sensory organs in the Semicircular Canals?
The Cupola
What is the sensory organ in the Utricle and Saccule?
The Maculae
What makes up the vestibule?
The Utricle and the Saccule
What are the Ampulla?
Swellings at the bottom of the semicircular canals
What do the Semicircular canals do?
Know where your head is in space
What allows you to know where your head is in which plane in 3D?
The semicircular canals
What do the Utricle and Saccule do?
They detect the head position relative to gravity and linear acceleration
What detects the head position relative to gravity and linear acceleration?
The Utricle and Saccule
How do the semicircular canals work?
- Base of the semicircular canals have an ampulla
- In the swelling is a fluid filled space filled with endolymph
- In the fluid is neuroepithelial cells called cilia they are surrounded by cupula
- When we turn our head left and right and cupula deflect and cause an action potential
How do the semicircular canals work?
- Base of the semicircular canals have an ampulla
- In the swelling is a fluid filled space filled with endolymph
- In the fluid is neuroepithelial cells called cilia they are surrounded by cupula
- When we turn our head left and right and cupula deflect and cause an action potential
Where is the vestibule located?
Between the cochlea and semicircular canals
What does the Vestibule contain?
The utricle and saccule
What is the sensory organ in the Utricle and Saccule?
The Maculae
How do the Utricle and Saccule detect head position relative to gravity and linear acceleration?
Stereocilia cells in the tectorial membrane brush against otoliths, causing action potentials in the maculae
What are the sensory organs in the semicircular canals?
The swelling of the ampulla
What detects nodding?
The Saccules maculae
What detects linear acceleration?
The utricles’ maculae
What triggers maculae an otoliths?
*Moving the head up and down (nodding yes - saccule)
*Walking forward - Utricle
What triggers the semicircular canals?
Moving your head in any direction
What are the two vestibulospinal tracts?
*Lateral Vestibulospinal tract
*Medial Vestibulospinal tract
What does the lateral vestibulospinal tract act on?
LMN(limbs)
What does the Medial Vestibulospinal tract act on?
LMN (axial muscles)
What does the Medial Vestibulospinal tract do?
Bilateral acts on the core to tighten muscles as the head moves
What does the Lateral Vestibulospinal tract do?
Ipsilateral does unconscious movement ex when you do a bicep curl
What is the Vestibular pathway?
Semicircular canals or the maculae will elicit an action potential and will act the vestibular nuclei in the midbrain
