Introduction to cranial nerves week 1 Flashcards
Cranial nerves provide ____ and ____ innervation to the ____ and ____.
Why are cranial nerves called cranial nerves?
Cranial nerves provide sensory and motor innervation to the head and neck.
Cranial nerves receive their name because they emerge from the cranium as opposed to spinal nerves which emerge from the spinal column.
What are the functional components (fiber types) that may be contained within cranial nerves? Define each.
Like spinal nerves cranial nerves contain:
General Somatic Afferents (GSA): Axons that carry information about perception of touch, pain, temperature, vibration, and proprioception from the periphery to the CNS.
General Somatic Efferents (GSE): Axons that carry motor innervation to skeletal (voluntary) muscles
General Visceral Afferents (GVA): Axons that carry sensory input from viscera (organs, this includes blood vessels) to the CNS.
General Visceral Efferents (GVE): Axons that carry motor innervation to smooth muscle, heart muscle, and smooth muscle in glands.
In addition, cranial nerves also contain:
Special Sensory Afferents (abbreviated SSA, SA, or SVA): Axons that carry information about the special senses of smell, taste, vision, hearing, and balance
Branchial Efferents (abbreviated BE or SVE): Motor innervation to skeletal muscles derived from pharyngeal arch mesoderm. Remember that certain structures of the head, face, and neck arise from pharyngeal arches.
Name and give the number for all of the cranial nerves.
Oh Oh Oh To Touch And Feel A Girls Vagina Ah Heaven
Olfactory CN I
Optic CN II
Oculomotor CN III
Trochlear CN IV
Trigeminal CN V
Abducens CN VI
Facial CN VII
Vestibulocochlear CN VIII (aka Auditory)
Glossopharyngeal CN IX
Vagus CN X
Accessory CN XII
Hypoglossal CN XII
What fiber type(s) are contained within the Olfactory nerve (CN I)?
Bundles of axons pass superiorly through perforations in the ____ _____ of the _____ bone to enter the cranial cavity and synapse on neurons of the ____ ____.
Cranial Nerve I: Olfactory nerve
- The olfactory nerve functions in the special sense of smell, olfaction.
- The olfactory nerve is composed of axons (SSA, SA, or SVA) from receptors in the olfactory epithelium at the superior aspect of each nasal cavity.
- Bundles of axons pass superiorly through perforations in the cribiform plate of the ethmoid bone to enter the cranial cavity and synapse on neurons of the olfactory bulb.
What kind of axons are contained within CN II (Optic nerve)?
What kind and what is the location of the receptors from which the optic nerves returns information to the brain from?
What is the pathway of the Optic nerve?
Cranial Nerve II: Optic nerve
- The optic nerve carries sensory fibers for the special sense of vision. These axons (SSA, SA, or SVA) return information from photoreceptors in the retina back to the brain. This process is quite complex and will be covered extensively in later lectures during this block.
- For now, one should appreciate that the optic nerve enters the cranial cavity through the optic canal, a foramen in the sphenoid bone. Think of this nerve as traveling from the orbit, where it originates at the posterior aspect of the eyeball (globe).
What fiber type(s) are contained within the Oculomotor nerve (CN III)?
What does the oculomotor nerve innervate?
What is the pathway of the the Oculmotor nerve?
Cranial Nerve III: Oculomotor nerve
The oculomotor nerve carries two types of fibers:
1) General Somatic Efferents (GSE fibers) which innervate most, but not all, of the extraocular muscles (the muscles that move the eyeball- you will learn the names in the “Orbital Anatomy” lecture).
2) General Visceral Efferents (GVE Fibers) that are part of the parasympathetic division of the ANS.
a. These GVE fibers innervate the sphincter pupillae muscle, responsible for constriction of the pupil
b. the ciliary muscles, responsible for accommodation of the lens.
The oculomotor nerve leaves the brainstem and travels anteriorly through the lateral wall of the cavernous sinus to eventually leave the cranial cavity to access the eye via the superior orbital fissure in the sphenoid bone.
What fiber type(s) are contained within the Trochlear nerve (CN IV)?
What does the trochlear nerve innervate?
What is the pathway of the Trochlear nerve?
Cranial Nerve IV: Trochlear nerve
- The trochlear nerve carries GSE fibers to innervate one extraocular muscle.
- The trochlear nerve leaves the brainstem and travels anteriorly through the lateral wall of the cavernous sinus to eventually leave the cranial cavity to access the eye via the superior orbital fissure in the sphenoid bone.
- While this nerve innervates only one muscle, its function is extremely important. The trochlear nerve is long and thin and is susceptible to injury in its course through the cranial cavity. (More on this in the Orbital Anatomy Lecture.)
What fiber type(s) are contained within CN V (Trigeminal nerve)?
What does the Trigeminal nerve innervate?
What is the trigeminal ganglion?
What are the divisions of the trigeminal nerve?
Cranial Nerve V: Trigeminal nerve
- The trigeminal nerve is the main general sensory innervation for the head. GSA fibers within this nerve carry sensory information pertaining to perception of touch, pain, temperature, vibration, and/or proprioception from areas such as the skin of the face, dura mater in the anterior and middle cranial fossae, the cornea, the nasal cavities, the tongue, the teeth, the lips, the mucosa of the mouth, and the temporomandibular joints of the jaw.
- The trigeminal nerve also carries branchial efferent fibers (BE fibers) which provide motor innervation to the muscles that move the jaw (muscles of mastication) as well as other muscles derived from the 1st pharyngeal arch.
- In the middle cranial fossa the sensory root of the trigeminal nerve expands into the trigeminal (semilunar) ganglion (which contains cell bodies of sensory neurons in the trigeminal nerve and is analogous to a dorsal root ganglion).
- The trigeminal nerve is subdivided into three divisions:
- The Ophthalmic nerve (V1)
- The Maxillary nerve (V2)
- The Mandibular nerve (V3)
Explain how each division of the trigeminal nerve exit the cranial cavity.
Which division is the only one to contain a motor component?
Divisions of CN V exit: Standing Room Only
- The ophthalmic nerve (V1) exits the cranial cavity to access the orbit via the superior orbital fissure in the sphenoid bone.
- The maxillary nerve (V2) exits the cranial cavity through the foramen rotundum in the sphenoid bone and enters the pterygopalatine fossa.
- The mandibular nerve (V3) exits the cranial cavity through the foramen ovale in the sphenoid bone and enters the infratemporal region. ***The motor fibers (BE fibers) of the trigeminal nerve unite with this division and thus the mandibular nerve is the only division of the trigeminal nerve to contain a motor component.
What fiber type(s) are contained within the Abducent nerve (CN VI)?
Explain the pathway of the Abducent nerve.
Cranial Nerve VI: Abducens (Abducent) Nerve
- The abducent nerve carries GSE fibers to provide motor innervation to the one extraocular muscle in the orbit.
- This nerve also enters and crosses the cavernous sinus and gains access to the orbit via the superior orbital fissure in the sphenoid bone.
What fiber type(s) are contained within the Facial nerve (CNVII)?
What does the facial nerve innervate?
What is the pathway of the Facial nerve?
Cranial Nerve VII: The Facial Nerve
The facial nerve contains:
- GSA fibers which convey sensory information from a small portion of skin around the ear
- SSA (SA or SVA) fibers which carry taste information from the anterior two-thirds of the tongue
- GVE fibers which are part of the parasympathetic division of the ANS and stimulate secretions of the lacrimal, submandibular, and sublingual glands as well as mucosa of the nasal cavity. One should appreciate that these fibers are preganglionic and synapse on postganglionic neurons in parasympathetic ganglia (to be named later).
- BE fibers which innervate muscles of facial expression as well as other muscles of the head and neck derived from the 2nd pharyngeal arch.
- GVA fibers which innervate portions of the nasal cavity and soft palate (this is a small contribution)
- The facial nerve will branch within the skull and finally exit the cranium via the stylomastoid foramen
What are the named branches of the facial nerve?
What is the relationship of the facial nerve to the parotid gland?
Two Zebras Bit My Coccyx
Temporal branch of the Facial nerve
Zygomatic branch of the Facial nerve
Buccal branch of the Facial nerve
Mandibular branch of the Facial nerve
Cervical branch of the Facial nerve
The Facial nerve is deep to the parotid gland.
What fiber type(s) does the Vestibulocochlear nerve (CN VIII, aka auditory nerve) contain?
What is innervated by this nerve?
What is the pathway of CN VIII?
Cranial Nerve VIII
The Vestibulocochlear Nerve The vestibulocochlear nerve contains SSA (SA or SVA) fibers for hearing and balance from specialized structures of the inner ear back to the CNS. This nerve will be covered in more detail later in this block). It passes through the internal acoustic meatus of the temporal bone.
CNs IX, X, and XI exit the cranium via the ___ ___ in the ____ ____.
CNs IX, X, and XI exit the cranium via the jugular foramen in the temporal bone.
What fiber type(s) does the glossopharyngeal nerve (CN IX) contain?
What is innervated by CN IX?
What is the pathway of this nerve?
Cranial Nerve IX: The Glossopharyngeal Nerve
The glossopharyngeal nerve contains:
- GVA fibers carrying sensory information from the carotid body and carotid sinus, mucus membranes of the middle ear, pharynx, and tongue
- GSA fibers carrying sensory information from the posterior one-third of the tongue, the palatine tonsils, and the pharynx as well as the skin of the outer ear
- SSA (SA or SVA) fibers carrying taste information from the posterior one-third of the tongue
- GVE fibers which are part of the parasympathetic division of the ANS and stimulate sercretory activity of the parotid gland. One should appreciate that these fibers are preganglionic and synapse on postganglionic neurons in parasympathetic ganglia (to be named later).
- BE fibers innervating the one muscle derived from the 3rd pharyngeal arch.
- Cranial nerve IX exits the cranium via the jugular foramen in the temporal bone.
What fiber type(s) does the Vagus nerve (CN X) contain?
What does the Vagus nerve innervate?
What is the pathway of this nerve?
Cranial Nerve X: The Vagus Nerve
The vagus nerve contains:
- GSA fibers that carry sensory information from a small amount of skin around the ear and the dura mater of the posterior cranial fossa back to the CNS as well as sensory information from the mucous membranes of the pharynx, esophagus, and larynx.
- GVA fibers that carry sensory information from chemoreceptors in the aortic body and baroreceptors (pressure receptors) in the aortic arch as well as the mucous membranes of the esophagus, bronchi, lungs, heart, and abdominal viscera in the foregut and midgut.
- SSA (SA or SVA) fibers conveying taste from the epiglottis and pharynx.
- GVE fibers which are part of the parasympathetic division of the ANS and stimulate smooth muscle and glands in the pharynx, larynx, thoracic and abdominal viscera of the foregut and midgut.
- BE fibers that innervate muscles derived from the 4th through 6th pharyngeal arches (pharyngeal and laryngeal muscles).
- CN X exits the jugular formen of the temporal bone.
What fiber type(s) are contained within the Accessory nerve (CN XI)?
What does the Accessory nerve innerate?
What is the pathway of this nerve?
Cranial Nerve XI: The Accessory Nerve
The accessory nerve contains:
- BE and GSE fibers that innervate the trapezius and sternocleidomastoid muscles.
- This nerve is also referred to as the spinal accessory nerve. Ever wonder why? This is because there are both spinal and brainstem “cranial” origins of the neurons in this nerve.
- CN XI exits the cranium via the jugular foramen of the temporal bone.
What fiber type(s) does CN XII (Hypoglossal nerve) contain?
What does the hypoglossal nerve innervate?
What is the pathway of hypoglossal nerve?
Cranial Nerve XII: The Hypoglossal Nerve
- The hypoglossal nerve contains GSE fibers which innervate all the intrinsic muscles of the tongue and all but one of the extrinsic muscles of the tongue (the exception being the palatoglossus muscle which is innervated by the vagus nerve).
- The hypoglossal nerve exits the skull via the hypoglossal canal in the occipital bone.
What are the 4 parasympathetic ganglion in the head? What nerves synapse on these ganglia? What is the CN origin of these preganglionic fibers?
from pg 62 of notes
