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 lens
What 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