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