lecture 8: CN VII-CN XII Flashcards by Demond Fleming

Sensory receptors that detect internal chemical stimuli?

internal organ chemoreceptors

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internal organ chemoreceptors: ________ to conscious awareness
Tracking concentrations of _________,_______,_______

Inaccessible
oxygen, glucose, and neuroactive hormones

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Both __________ and ________ senses are responsible for detecting external chemical stimuli

gustatory (taste) and olfactory (smell)

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Gustatory (taste) is a part of the ________ cavity
Olfactory (smell) is a part of the ______ cavity

oral
nasal

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What allows you to sense: heat of chili, coolness of methol (mouth) sting of ammonia (nose/eye)

chemosensitive endings; CN V-trigeminal, through somatosensory

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papillae on the tongue:
-“surrounded by a wall”
-“leaf-like”, lateral tongue
-“mushroom form”

circumvallate papillae
foliate papillae
fungiform papillae

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Circumvallate Papillae
Location:
Number:
Tatse Buds:
Innervation:

Posterior 1/3 of the tongue, near the oropharynx.
8-12 in total
Each papilla has around 250 taste buds
CN IX (Glossopharyngeal nerve) is responsible for both chemical and common somatosensory stimuli

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Foliate Papillae
Location:
Number:
Taste Buds:
Innervation: -chemical & somatosensory

middle to posterior lateral tongue
10 on each side - ea. contains 100-150 taste buds
CN VII/CN V for chemical stimuli
CN V/XI for somatosensory sensation

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Fungiform Papillae
Location:
Number:
Taste Buds:
Innervation:

Anterior 2/3 of tongue, oral cavity
200-300 in total with ea. contains
3-5 taste buds
CN VII/V- chemical stimuli
CN V for somatosensory stimuli

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Why would someone like foods more than others: gourmet

huge variation of total taste buds: >100 folds

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Taste receptor cells
cell type:
number:
lifespan:

specialized spindle-shaped epithelial cells
100 in each taste bud
Lasts 1-2 weeks; renewal via basal cell differentiation.

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Taste receptor cells
properties:
microvilli:
synapses: occur at the base, connecting with dendrites of CN __________, __________, and __________ (4), not with CN __________.

Taste receptor cells have glial properties, not neurons.
Present, with taste pores
on the tip.
CN VII, IX, and X (4), not CN V.

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Taste receptors cell
communication:

Direct communication through gap junctions (5), forming electric synapses.

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Gathering of somata of 1st-order neurons:

Ganglia of CN VII, IX, and X

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Picture these ganglia as social hubs where 1st order neurons mingle and exchange information:
GG: Geniculate ganglia for
IG IX: Inferior ganglion for
IG X: Interior ganglion for

CN VII
CN IX
CN X

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Where are 2nd order neurons conducted?

solitary nuclei

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Chemical molecules transduce taste receptor cells (stimulate the sense of tatse) -

Tastants

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Salty
-Mechanism: ionotropic channels with _____/_____ ions.
-Results: Direct ________ of the taste cell membrane.

sodium/potassium
depolarization

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Sour
-Mechanism: Ionotropic channels with __________ ions.
-Results: Direct ________ of the taste cell membrane.

H+ (hydrogen ion)
depolarization

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Sweet/Umami/Bitter
Mechanism: __________ receptors.

G-protein coupled receptors (GPCRs)

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The following statement is True or False.

Activation of taste receptors results in action potentials?

False: graded potential

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Similar to salty or sour ion channels _______ helps humans detect harmful/toxic foods.

6th taste: ammonium chloride

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Which CN is being described?
-senses light ad responsible for vision
-constricts pupil and controls movement of eyeball

CN II (optic)
CN III (oculomotor)

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Taste projection pathway is ipsilateral or contralateral projection?

ipsilateral

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Taste projection pathway: 1st order neuron 2nd order neuron 3rd order neuron Then project to ________lobe

geniculate/inferior ganglia solitary nucleus VPM of thalamus insular

Which of the following CN is in the somatosensory pathway for chemical sensation?

CN V

Where is the nuclei of CN VII, facial n located?

lateral pontomedullary junction

Cranial nuclei associated with CN VII. Ss: Sm: Vs: Vm:

Ss: spinal Trigeminal nucleus Sm: Facial Motor Nuclei Vs: Solitary Nucleus Vm: Superior Salivatory Nucleus

This nucleus is involved in processing ____________ information related to pain and temperature from the face.

Ss (Spinal Trigeminal Nucleus)

This nucleus refers to the motor nucleus of the facial nerve (CN VII), controlling the muscles of face expression.

Sm (Facial Motor Nuclei)

This nucleus receives sensory information from various cranial nerves, including taste sensations. "Mission completed"

Vs (Solitary Nucleus)

This nucleus associated with CN VII is involved parasympathetic functions

Vm (Superior Salivatory Nucleus):

CN VII pathway: exits the brainstem from pontomeduallry junction through _________ and terminal branches through _______ foramen

internal acoustic meatus stylomastoid

Terminal branches of of CN VII, Sm component:

Temporal Zygomatic Buccal Mandibular Cervical Posterior auricular **Two Zebras Bite My Cookies**

Facial and scalp muscles are ______ for facial expression _______ deep with parotid gland duct piercing through

superficial Buccinator

Facial somatic motor nucleus has dorsal and ventral components: -Dorsal nucleus: projections from __________ to _____ & ______ -Ventral nucleus: projections from __________ except (ACC) to _______

bilateral anterior cingulate cortex (ACC); forehead & scalp contralateral cerebral cortex; lower face

UMN and LMN Injuries - Facial Nerve (CN VII) UMN: LMN:

UMN: can still wrinkle LMN: whole side of face flaccid -Bell's palsy

Can patients with LMN CN VII injury produce facial expressions?

No.(LMN) injuries, such as Bell's Palsy affecting CN VII, there is often a loss of voluntary control over facial muscles on the affected side, resulting in an inability to produce facial expressions.

In UMN CN VII injury, can patients still express emotions like responding to humor?

Yes. When hearing a humor, patients with (UMN) injuries affecting CN VII may still be able to express emotions in the upper part of the face. However, voluntary control over the lower part of the face, including smiling on command, may be compromised.

Collect and conduct sound wave through air - Sound wave to vibration (both are mechanic waves) -

external ear middle ear

What separates the external ear from the middle ear?

Tympanic Membrane (Eardrum)

Name the three ossicles in the middle ear.

Malleus, Incus, Stapes

Which cranial nerve innervates the Tensor Tympani muscle?

CN V - Trigeminal Nerve

What is the function of the Stapedius muscle in the middle ear? Increased sensitivity to normal environmental sounds ______

Controls the movement of the stapes, decrease vibrations and protecting the inner ear. hyperacusis due to functional loss

What shape is the cochlea, and its function? What important structure within the cochlea transduces sound vibrations into electrical signals?

snail-shaped; vestibular system Organ of Corti

Which cranial nerve conducts "spicy" taste?

CN V - chemical sensation

3 main structural components of the Cochlea:

scala vestibuli scala media scala tympani

Scala vestibule - starts at the _____ window and continuous to ______.

oval vestibule

Scala media: houses the ________ membrane and _______ receptors/cells. Contains _______ fluid and high concentration of _____ and low concentration of _____

basilar membrane; hearing hair endolymph high: K+ , low: Na+

Scala tympani- extends from apex to ________ window. Unidirectional flow of ________

round; perilymph

Once damaged or lost, ___________ do not regenerate as effectively as some other types of cells, such as the photoreceptor cells (rods and cones) in the retina.

hair cells

Where is the body of hair cells located?

basilar membrane

The _________, which are tiny hair-like projections on the surface of hair cells, are in direct contact with the ________ the fluid within the Scala Media.

cilia; endolymph

Hair cells have multiple ______ which are hair-like projections. Hair cells typically lack true _______ Hair cells are arranged in rows of increasing height, and they are mechanically linked together by structures called ______

stereocilia; kinocilium; tip links

Inner Hair Cells (IHCs): Arrangement: Function:

1 line/row of inner hair cells. auditory function

Outer Hair Cells (OHCs): Arrangement: Function:

3 line/rows of outer hair cells. modulatory function, changing shape and size

Stapes pushed flow of ______ when sound waves enter the ear. The pressure waves generated by the stapes cause the fluid in the ________ and to move/expand.

perilymph scala vestibuli; scala tympani

The cochlea returns to its ______ state when external sound waves stop.

baseline

When sound waves cause the basilar membrane to vibrate, the stereocilia (hair-like projections) on the hair cells are __________ which causes tension on the tip links. This leads to the release of ________ stereocilia tilt to taller ones: stereocilia tilt away the taller ones:

displaced; neurotransmitters increase depolarization decrease depolarization

Hair cells in the inner ear do not generate _________ like neurons do. They produce _______ in response to mechanical stimuli

action potentials; graded potentials

The released neurotransmitters activate the ________ fibers (auditory nerve fibers) connected to the hair cells. The activation leads to the transmission of electrical signals along the ______ nerve pathway to the brain.

cochlear nerve; auditory

Frequency tuning - spatial agreement (tonotopy) is _______ all the way to A1. base of cochlea: more responsive to _______ frequency sounds apex of the cochlea: more responsive to _______ frequency sounds

maintained higher lower

For natural sound, spectrum of frequencies must be ________

decomposed

Auditory pathway: Projections are unilateral or bilateral? Projection are single and multiple? CNS injury to auditory pathway will always lead to deafness?

bilateral; multiple projections NO; may or may not

Auditory pathway: Conscious perceptions of sound need at least ________ neuron.

List the 4 neurons of the auditory pathway: 1st Order Neuron: 2nd Order Neuron: 3rd Order Neuron: 4th Order Neuron:

1: Spiral ganglion 2: Cochlear nuclei 3: Inferior colliculus 4: Medial geniculate nucleus (MGN) of the thalamus

Primary auditory cortex is located in Brodmann area _______ lateral to medial: anterior to posterior:

41 low to high frequencies (what) organization from low to high frequencies (where)

Why is Two Ears are Necessary for Sound Localization if sound waves arrive at both ears?

Interaural Time & Intensity Difference

Ears: Interaural Time- -The difference in the _______ it takes for a sound wave to reach each ear. -One ear detects the sound slightly _______ than the other, due to better detection of _________

time earlier; low freq. sound

Ears: Interaural Intensity- -The head will _______/_____ some sound wave. -High freq sound carry higher ________.

block/absorb energy

The brain computes differences in sound arrival ______ and ______ to locate the origin of the sound. OWLS: Two ears located on _______ levels, to __________ their ability to compute interaural differences and accurately locate the origin of sounds.

time & intensity different; enhance