UNIT 2: Cranial Nerves Flashcards
ascending pathways are
- afferent (sensory) inputs to higher regions of the CNS
- create cognitive perception of incoming signals
- guide the creation of execution of motor responses to enviro stimuli
3 neurons of the ascending pathways
primary neuron (spinal or cranial nerve), secondary neuron, tertiary neuron
descending pathways are
- efferent (motor) outputs from cortex and brainstem to somatic and visceral motor neurons
- execution of motor activity
2 neurons of the descending pathways are
upper motor neuron (corticospinal or corticobular) and lower motor neuron (spinal or cranial nerve)
describe the primary neuron of the afferent pathway
- “nerve” (outside the brain)
- dendrites innervate end receptor cells
- cell body is typically located at a different location in a ganglion
- axon extends to synapse in the sensory nucleus in the brain stem
describe the secondary neuron of the afferent pathway
- cell body in the brainstem nucleus that is associated w the nerve
- axon extends to the thalamus… the sensory relay station
describe the tertiary neuron of the afferent pathway
- cell body in the thalamus
- axon extends to the primary sensory cortex (most often in the postcentral gyrus of the parietal lobe)
describe the somatic motor pathway of the efferent pathway
- upper motor neuron has a cell body in the motor cortex
- axon extends to the level of the brainstem
- motor nucleus is located in the brainstem
- the lower motor neuron has the cell body in the brainstem nucleus which is associated w a nerve
- axon extends to and innervates muscle fibres an/or glans
describe the visceral motor pathway of the efferent pathway
- for the upper neuron, input comes from other nuclei like the limbic system
- then travels to brainstem to the lower motor neuron
most cranial nerves provide bilateral innervation because
gives some redundancy in especially important areas like the face and throat for example
describe spinal nerves
- contain both afferent and efferent fibres
- project from the spinal cord
cervical spinal nerves correspond to
neck, shoulder, arms
thoracic spinal nerves correspond to
upper trunk
lumbar and sacral spinal nerves correspond to
lower trunk, legs, feet
how many cranial nerves are there
12
the cranial nerves project to and from where? (name exceptions)
brainstem, except for CNI and CNII
how are cranial nerves more complex then spinal nerves
- can be motor, or sensory, or both
- motor and sensory can serve somatic and/or autonomic functions
- can serve general or special end receptors
What part of the embryo develops into our face and airway and which part doesn’t?
- the mesoderm develops into somites which eventually make up most of the sensory and motor tissue… except …
- most of our face and neck do not dev from somites - they dev from branchial arches
describe how a cranial nerve is a functional unit
nerve + brainstem nucleus + peripheral target = functional unit
CN 1
- olfactory nerve
- sensory
- mediates sense of smell
- olfactory sensors in mucous membrane of nasal cavities
CN II
- optic nerve
- sensory
- vision = sensory photoreceptors in retina
CN III
- oculomotor nerve
- motor
- most extrinsic ocular muscles
- light and accommodation reflexes of pupil constriction and focus
- oculomotor nuclei in midbrain
CN III, CN IV, CN VI are all involved in
moving our eyes and controlling pupils and lens
CN IV
- trochlear nerve
- motor
- turning eyes down and in
- trochlear motor nucleus in midbrain
CN VI
- abducens nerve
- motor
- abduct eye (move laterally away from midline)
- abducent motor nucleus in pons
CN V
- trigeminal
- motor and sensory
- somatic sense for the face and oral cavity
- muscles of masstication, tensor veli palatini (soft palate), and tensor tympani (ear drum)
- 3 divisions
3 divisions of CN V
Ophthalmic, maxillary, mandibular
describe the ophthalmic division of CN V
- sensory
- links to the skin of the upper face, forehead, scalp, cornea, iris, conjunctiva, upper eyelid, nasal cavity mucosa, meninges
describe the maxillary division of CN V
- sensory
- links to the lower eyelid, skin of the nose, maxilla, upper teeth and gums, upper lid, buccal mucosa, maxillary sinuses
describe the mandibular division of CN V
- sensory and motor
- links to the mandible, lower teeth and gums, anterior 2/3 of the tongue, lower cheek and chin, temporomandibular joint, external auditory meatus and pinna of the ear, muscles of mastication (prioprioception)
what are the 4 nuclei of CN V
mesencephalic nucleus, principal sensory nucleus, spinal trigeminal nucleus, trigeminal motor nucleus
the mesencephalic nucleus of CN V is in the ____ and has ____ inputs from the _____ muscles
- midbrain
- proprioceptive
- mandibular
the principal sensory nucleus of CN V is in the ____ and has ____ inputs, critical for ____
- pons
- cutaneous and tactile
- speech dev
the spinal trigeminal nucleus of CN V is in the ____ and has ____ inputs
- medulla
- aka nucleus of the spinal tract
- noxious and thermal inputs
the trigeminal nucleus of CN V is in the ____
pons
CN VII
- Facial nerve
- sensory and motor
- facial muscles + stapedius muscle (middle ear) and suprahyoid muscles
- lacrimal gland, submandibular and sublingual salivary glands, mucous membranes of nose and palate
- taste from 2/3 of the tongue
- sensation from the external auditory meatus, external surface of the tympanic membrane, skin behind the ear
facial motor nucleus of CN VII is in the
pons
superior salivatory nucleus of CN VII is in the
pons
Nucleus of the spinal tract of CN VII is in the
medulla
solitary tract nucleus of CN VII is in the
medulla
CN VIII
- vestibulocochlear
- sensory
- hearing and vestibular sense
- organs of hearing and vestibular sensation in the inner ear
cochlear and vestibular nuclei of CN VIII is located at
pontomedullary junction (where pons and medulla come together)
CN IX
- Glossopharyngeal
- sensory and motor
- taste from posterior 1/3 of tongue and soft palate
- touch, pain, temp from posterior 1/3 of tongue, faucial pillars, upper pharynx, middle ear
- barosensation and chemosensation in internal carotid artery (blood press and oxygenation)
- pain and temp from skin of the ear
- stylopharyngeus muscle
- parotid gland (salivary flow)
the solitary tract nucleus of CN IX is in the
medulla
the nucleus of the spinal tract for CN IX is in the
medulla
the nucleus ambiguus of CN IX is in the
medulla
the inferior salivatory nucleus of CN IX is in the
medulla
CN X
- Vagus
- sensory and motor
- extensive nervous supply thru head, neck, trunk
- pain, touch, temp from tympanic membrane, pinna, and external auditory meatus
- pain, touch and temp from pharynx, larynx, thoracic, and abdominal viscera, esophagus, and bronchi
- barosentation and chemosensation from aorta
- taste from epiglottis
- parasymp innervation of intestines, pancreas, stomach, esophagus, trachea, bronchial smooth muscle and mucosal glads, kidney, liver, heart
- soft palate, pharynx, and larynx
the nucleus of the spinal tract of CN X is in the
medulla
the nucleus of the solitary tract nucleus of CN X is in the
medulla
the nucleus of the dorsal motor nucleus of vagus of CN X is in the
medulla
the nucleus of the ambiguus of CN X is in the
medulla
CN XI
- accessory
- motor
- sternocleidmastoid and trapezius
- neck and shoulder movements
nucleus ambiguus of CN XI is in the
medulla
CN XII
- Hypoglossal
- motor
- all muscles of the tongue except 1
hypoglossal nucleus of CN XI is in the
medulla
MRI
- magnetic resonance imaging
- shows change in soft tissue
- costly, not first step
fMRI
- functional magnetic resonance imaging
- looking for change in blood flow - more used in research
DTI
Diffusion tensor imaging
- look at communication - aka association and commissural fibres
CT
computed tomography
- cheaper cousin of MRI
- radiation
can show a stoke usually via disruption of blood, some bone changes, and used to show tumours
PET
- Positron emission tomography
- like a CT but w radioactive traser to see blood flow
hemorrhages w/i arterial or venous systems causes
a vascular pathology, blood to pool w/i neural tissue, causing a disruption of blood supply beyond the point of hemorrhage
ischemic stroke is
a vascular pathology, disruption of blood supply leading to ischemia (dec oxygen), and evetually an infarct (dead brain tissue)
- thrombus = blockage in a vessel
- embolus - travelling clot or fragment of thrombus
Aneurysms are
a vascular pathology, balloon like distension of arterial wall, risk for rupture and hemorrhage
arteriovenous malformation (AVM) is
a vascular pathology, congenital tangles of arteries and veins, risk for growth and rupture
amyotrophic lateral sclerosis is
a degenerative condition, disease of motor neurons - cell bodies in spinal cord and CN nuclei and precentral pyrus can be affected
multiple sclerosis is
a degenerative condition, degeneration of myelin sheath on axons; both sensory and motor
parkinsons disease is
a degenerative condition, disease of basal ganglia, degeneration of dopamine producing neurons in substantia nigra
neoplasms/tumors are
a degenerative condition, abnormal proliferation of cells, typically in myelin or glial cells
