Quiz 2 - Cranial Nerves and Components of the Intracranial Vault Flashcards
Cranial Nerve I
Olfactory, sensory (nose)
Cranial nerve II
Optic, sensory (eye)
Cranial nerve III
Oculomotor, motor (all eye muscles except for those from CN IV and VI)
Cranial nerve IV
trochlear, motor (superior oblique muscles)
Cranial nerve V
Trigeminal, Sensory (face, sinuses, teeth etc.)
Motor: muscles of mastication
Cranial nerve VI
Abducent, motor (external rectus muscle)
Cranial nerve VII
Facial, motor (muscles of the face)
Cranial nerve VIII
Vestibulocochlear, sensory (inner ear
Cranial nerve IX
Glossopharyngeal, motor (pharyngeal/musculature)
Sensory: posterior part of tongue, tonsils, and pharynx
Cranial nerve X
Vagus, motor (heart, lungs, bronchi, GI tract)
sensory: heart, lungs, bronchi, trachea, larynx, pharynx, GI tract, and external ear
Cranial nerve XI
accessory, motor (sternocleidomastoid and trapezius muscles)
Cranial nerve XII
Hypoglossal, motor (muscles of the tongue)
injury to CN VII
from using mask straps
CN VII functions
Innervates the muscles of facial expression (motor)
Innervates the Orbicularis Oculi
Provides sensory and parasympathetic innervation
Frequently monitored during surgery around the face
Parotidectomy, acoustic neuroma, cochlear implant
Cranial Nerve IX functions
Sensory innervation to the baroreceptors of the carotid sinus
Can cause bradycardia and hypotension during CEA
Sensory innervation to the chemoreceptors of the carotid body
Sensory innervation of the posterior oral mucosa (gag reflex)
Motor innervation of the pharynx (swallowing)
Provides parasympathetic innervation to the parotid gland
Cranial Nerve X forms:
Superior Laryngeal Nerve (CN X)
Recurrent Laryngeal Nerve (CN X)
CN X (Heart function)
convey parasympathetic innervation to the sino-atrial and atrio-ventricular nodes of the heart. Vagal stimulation reduces heart rate and is constantly active.
CN X (Lungs function)
Parasympathetic stimulation within the pulmonary plexuses causes vasodilation and bronchoconstriction.
CN X (GI function)
Provides parasympathetic innervation to abdominal organs. Stimulate smooth muscle contraction and glandular secretions in these organs.
Vagal stimulation during GI surgery and endoscopy can lead to significant bradycardia and even asystole.
Recurrent Laryngeal Nerve (L and R locations)
R RLN goes under the subclavian artery and runs posterior
Helps to maintain connection to the larynx
L RLN loops under the aortic arch
RLN injury
Bilateral RLN damage/injury = laryngospasm = stridor/resp distress
unilateral RLN injury (cord goes paramedian) produces abductor vocal cord paralysis = hoarseness
Superior Laryngeal Nerve
Internal branch (sensory)
External Branch (motor)
cricothyroid muscles
SLN injury
The SLN (external branch) innervates the cricothyroid muscle, which tenses and adducts the vocal cords.
Injury to the nerve can produce changes in voice quality, but is generally not dangerous.
Oculocardiac reflex
AKA Aschner phenomenon is a physiological response where the heart rate decreases due to pressure applied to the eye or traction on the extraocular muscles. This reflex is mediated by the trigeminal nerve (cranial nerve V) and the vagus nerve (cranial nerve X).
Components of Intracranial vault
Brain 80-85%
Blood 5-10%
Cerebral spinal fluid 10-15%
Blood supply to the brain
B/L Carotid Arteries
&
B/L Vertebral Arteries
Left carotid artery
originates off of aortic arch
Right carotid artery
originates off of right innominate artery
(Aline in right arm to monitor for injury of innominate artery)
The Internal Carotid Artery
enter the base of the skull.
The External Carotid artery
remain superficial to the skull
Internal Carotid arteries
Arterial supply to the Circle of Willis
Arterial supply of the eye via the ophthalmic artery
Ultimately bifurcates into the anterior and middle cerebral arteries
Blood flow through circle of Willis
Very Big Posterior Polyps Invaded My Aching Ass
vertebral, basilar, posterior, posterior communicating, internal carotid, middle, anterior, anterior communicating
Vertebral Artery
branch off the innominate artery (r) and the left subclavian artery and enter via the foramen magnum
branches off to supply the anterior spinal artery
Become the basilar artery which bifurcates to become the posterior cerebral arteries
The posterior cerebral arteries communicate with the middle cerebral arteries via the posterior communication artery
Venous System
Venous blood drains into the venous sinuses which lie between the layers of the dura mater and drain into the internal jugular vein
Sinuses are valveless
Blood can flow back and forth
Pressure within them is negative (air embolism)
Little influence by the autonomic nervous system
meninges
Covers the brain and spinal cord and consists of:
Dura mater
Arachnoid Mater
Pia mater
Pia mater
innermost layer - Anchored to the brain by astrocytes which form the blood-brain barrier
Pia Mater Transport
small molecules (H2O, O2, CO2)
lipophilic molecules (EtOH, heroin)
passive transport of glucose
active transport of amino acids/NT precursors
Prevents: large molecules (dopamine) and charged (ionized molecules)
Arachnoid Mater
midsection - lacelike structure below which is the subarachnoid space
CSF circulates in the subarachnoid space (between arachnoid and pia mater)
The Arachnoid Mater contains the blood supply to the brain.
Dura mater
outer layer - nonelastic dura has an endosteal layer connected to the periosteum
meningeal layer - between these two layers is the epidural space. potential spaces under the dura or the subdural space have a lot of vascularity with little supporting structure and may bleed with injury.
Drains CSF
Meningioma
Type of Tumor: Forms in the meninges (membranes around the brain and spinal cord).
Nature: Mostly benign (non-cancerous) and slow-growing.
Symptoms: Can include headaches, vision problems, hearing loss, memory loss, weakness, seizures, and speech difficulties.
Epidural vs. subural hematoma
EPIDURAL IS TYPICALLY MORE RAPID ONSET AND DANGEROUS
d
Subarachnoid hemorrhage
neurological emergency
in subarachnoid space
less common, but important cause of strokes
Goal - stop bleed
Epidural hematoma
Bleeding between the skull and dura mater
Usual arterial in origin (meningeal arteries)
Subdural Hematoma
Bleeding between the dura and arachnoid mater
Usually resulting from tears inbridging veins
Subarachnoid hemorrhage (bleeding site)
Bleeding between the arachnoid membrane and the pia mater
Usually from a rupturedcerebral aneurysm.
Ventricles of the brain
Lateral Ventricles: There are two lateral ventricles, one in each hemisphere of the brain. They are the largest ventricles and are C-shaped.
Third Ventricle: Located in the midline of the brain, between the two halves of the thalamus.
Fourth Ventricle: Situated between the brainstem and the cerebellum, it connects to the central canal of the spinal cord.
Lateral ventricles
within the cerebral hemispheres and communicate with the third ventricle through the foramen of Monroe
third ventricle
inside the substance of the thalamus, dividing it to 2 lateral parts. The floor of this ventricle is the optic chiasm
fourth ventricle
communicates with the third ventricle via the aqueduct of sylvius, lies anterior to the cerebellum and has a connection to the subarachnoid space through the median foramen of Magendie and 2 lateral foramen of Luschka
Brain ventricles
Lined by ependymal cells which help to form the choroid plexus
There are two lateral ventricles in the cerebral hemispheres
Third ventricle is located in the diencephalon
Fourth ventricle is located between the pons and the cerebellum
Cerebrospinal Fluid (CSF)
Produced by the Choroid Plexus in the cerebral ventricles
Surrounds the brain and spinal cord
10 - 15% of intracranial volume
Approximately 500cc are produced per 24hrs
The total volume of CSF is roughly 150cc
function of CSF
maintains a milieu in which the brain can function by regulating pH and electrolytes, carrying away waste products, and delivering nutrients
flow of CSF
through ventricles, to arachnoid space, to dural sinuses (back to circulation)
VP Shunt
Most common area for VP shunt to drain to the gut/abd cavity
