Cranial Nerves Flashcards
What is the function of the cranial nerves?
To exchange information between the peripheral nervous system and the central nervous system
What are the 4 functions of the cranial nerves?
- Transmit somatosensory information from the skin, muscles of the face, and the TMJ
- Transmit special sensory information related to visual, auditory, vestibular, gustatory, olfactory, and visceral sensations
- Supply motor innervation to the muscles of the face, eyes, tongue, jaw, and two neck muscles
- Provide parasympathetic regulation of pupil size, curvature of the lens of the eye, HR, BP, breathing, and digestion
Which cranial nerves arise on the midbrain?
III, IV, V, and VII
Which cranial nerves arise on the pons?
V, VI, VII, IX, and X
Which cranial nerves arise on the medulla?
V, VII, IX, X, XI, and XII
Which cranial nerves arise on both the pons and medulla?
VII, VIII, IX, and X
What is the function of cranial nerve I?
Olfactory: Sense of smell
Olfactory nerve transmits information from where to where?
nasal chemoreceptors to the olfactory bulb
What is the function of cranial nerve II?
Optic: Vision
Optic nerve transmits information from where to where?
The retina to the lateral geniculate body of the thalamus, then to the visual cortex, and finally to nuclei in the midbrain
What is the function of cranial nerve III?
Oculomotor:
Moves eyes up, down, and medially
Raises upper eyelid
Constricts pupil
Adjusts the shape of the lensWhat is the function of cranial nerve IV?
Trochlear:
Moves eye medially and down
What is the function of cranial nerve V?
Trigeminal:
Facial sensation, chewing, sensation from the TMJ
Cranial nerve V mediates reflex actions by providing afferent limb for what reflex?
The corneal (blink) reflex
What are the 3 branches of CN V?
- Ophthalmic
- Maxillary
- Mandibular
What is the function of cranial nerve VI?
Abducens: Abducts the eye
Which CNs innervate the 6 extraocular muscles that move the eye?
III, IV, and VI
Describe the synergistic action of the eye muscles when looking at a pen that moves toward you
There must be activation of both the right medial rectus and the left medial rectus
Besides control of voluntary movement, CN III controls what?
reflexive constriction of the pupil and contraction of the muscles controlling the lens of the eye via parasympathetic neurons
What happens when objects are viewed closer than 20 cm? What is this action called?
The ciliary muscle contracts, which increases the curvature of the lens. This is called accommodation.
What is the purpose of accommodation?
It increases refraction of light rays to ensure that the focal point will be maintained on the retina
The pupillary, consensual, and accommodation reflexes involve which cranial nerves?
The optic and oculomotor
*optic provides the sensory (afferent) limb and the oculomotor provides the motor (efferent) limb
What is the pupillary reflex
The constriction of the pupil in the eye directly stimulated by the bright light
What is the consensual reflex
The constriction of the pupil in the other eye stimulated by the bright light
What 3 adjustments occur during the accommodation reflex?
- The pupils constrict
- The eyes converge
- The lens becomes more convex
The _____ nerve provides afferent limb and the ______ nerve provides the efferent limb of the corneal reflex
trigeminal
facial
What is the function of cranial nerve VII?
Facial:
facial expressions, closes eye, tears, salivation, and taste from the anterior tongue
Where are signals to and from the facial nerve processed?
in the nuclei located in the pons, medulla, and upper spinal cord
What is the function of cranial nerve VIII?
Vestibulocochlear:
sensation of head position relative to gravity and head movement, also functions in hearing
What are the 2 distinct branches of the vestibulocochlear nerve? What type of information does each transmit?
- Vestibular branch transmits information related to head position and head movement
- Cochlear branch transmits information related to hearing
Where are the peripheral receptors that transmit information to the vestibulocochlear nerve found?
In the inner ear in a structure called the labyrinth
What 2 things does the labyrinth consist of?
- the vestibular apparatus
- the cochlea
What divides the cochlea into upper and lower chambers?
the basilar membrane
The upper chamber of the cochlea is called the ____ _____.
The lower chamber of the cochlea is called the ____ _____.
scala vestibuli
scala tympani
Within the cochlear duct, resting on the basilar membrane, is the organ of ____.
Corti
Describe the process of converting sound into a neural signal
1) sound enters the external ear
2) vibration moves the ossicles
3) the ossicles vibrate the membrane at the opening of the upper chamber
4) this vibration moves the fluid contained within the scala vestibule
5) this movement causes disruption of the basilar membrane and its attached hair cells
6) the hair cells bend and the hair becomes depolarized
7) the cochlear nerve endings are activated
What are the 3 auditory functions in the CNS?
- Increases the activity level throughout the CNS
- Orients the head and eyes toward sounds
- Provides conscious awareness and recognition of sounds
Once the cochlear nuclei are activated, auditory information is transmitted to what 3 structures?
- Reticular formation
- Inferior colliculus
- Medial geniculate body
What do reticular formation connections account for?
the activating effect of sounds on the CNS
For example: loud sounds can rouse a sleeping person
The inferior colliculus integrates auditory information from where to do what?
from both ears to detect the location of sounds
What does the medial geniculate body serve as?
A thalamic relay station for auditory information to the primary auditory cortex
What are the 3 cortical areas that are dedicated to processing auditory information?
- Primary auditory cortex
- Secondary auditory cortex
- Wernicke’s area
The primary auditory cortex is the site of what?
conscious awareness of the intensity of sounds
What does the secondary auditory cortex do?
It compares sounds with memories of other sounds, then categorizes the sounds as language, music, or noise
What happens in Wernicke’s area?
It is where comprehension of spoken language occurs
What is the function of cranial nerve IX?
Glossopharyngeal:
swallowing, salivation, and taste in the posterior tongue
Glossopharyngeal sensory fibers contribute the afferent limb of which reflexes?
the gag and swallowing reflexes
What is the function of cranial nerve X?
Vagus:
regulates viscera, swallowing, speech, and taste
The far reaching connections of the vagus nerve allow it to do what 4 things?
- decrease HR
- constrict the bronchi
- affect speech production
- increase digestive activity
Vagus motor fibers contribute the efferent limb of which reflexes?
the gag and swallowing reflexes
What is the function of cranial nerve XI?
Accessory:
Elevates the shoulders and turns the head
What muscles does the accessory nerve innervate?
The trapezius and sternocleidomastoid muscles
What is the function of cranial nerve XII?
Hypoglossal:
Moves the tongue
Activity of the hypoglossal nerve is controlled by what neural circuits?
both voluntary and reflexive
What are the 3 stages of swallowing?
- Oral
- Pharyngeal and laryngeal
- Esophageal
Which cranial nerves are involved in the oral stage of swallowing?
V VII IX X XII
Which cranial nerves are involved in the pharyngeal and laryngeal stage of swallowing?
IX and X
Which cranial nerve is involved in the esophageal stage of swallowing?
X
At the CN level, sounds generated by the larynx (CN __) are articulated by the soft palate (CN __), lips (CN __), jaws (CN __), and tongue (CN __)
X X VII V XII
What cranial nerves contain motor neuron fibers?
III - VII and IX - XII
Cranial nerve efferents receive descending regulation via what?
- corticobrainstem tracts (voluntary)
- limbic system (emotional)
Speaking is mostly ______.
voluntary
