What types of neurons make up CN 5?
- somatosensory → from skin, muscle, and joint conscious sensory receptors of anterior 2/3 head
- somatomotor → muscles of mastication nad tensor tympani
What are the 3 branches of the trigeminal nerve (CN 5)?
opthalmic
maxillary
mandibular
what region of the head/face is the opthalmic nerve the primary sensory neuron for?
- upper face-forehead
- cornea
- upper eyelid
- dorsum of nose
*cutaneous sensation (touch, pressure, pain and temp) and proprioception
what region of the head/face is the maxillary nerve the primary sensory neuron for?
- middle face-lower lip
- lateral nose
- cheek
- upper jaw/teeth
- palate
- upper lip
what region of the head/face is the mandibular nerve the primamry sensory neuron for?
- lower face-lower lip
- lower jaw/teeth
- tongue
- chin
what is the soma for the 3 somatosensory peripheral axons (opthalamic, maxillary, mandibular) of the trigeminal nerve?
trigeminal (semilunar) ganglion
where is the trigeminal (semilunar) ganglion located?
base of sella turcica
close proximity to the internal carotid
Describe the motor pathway for the Trigeminal Nerve
- R/L precentral gyrus (lateral homonculus) = UMN
- corticobulbar tract
- crossed and uncrossed bilateral input to motor nucleus trigeminal nerve = LMN
- trigeminal nerve
- 3 peripheral branches of trigeminal nerve
what muscles are innervated by the trigeminal nerve?
- muscles of mastication
- mylohyoid
- anterior belly digastric
- tensor tympani
how does the sensation of taste occur?
it is a result of a chemical interaction between molecules in mouth and membrane chemoreceptors on receptor cells in taste buds
Where are taste buds located in the mouth?
in papillae of the:
- tongue
- soft palate (roof of mouth)
- pharynx (throat)
- larynx
T/F: taste buds are the neuronal receptor cells for the sense of taste
FALSE
they are receptor cells but NOT neurons.
dendrites of cranial nerves synapse onto them
receptors in the tip of the tongue are more sensitive to ______
sweet
receptors in the posterior tongue are more sensitive to _______
bitter
receptors in lateral tongue are most sensitive to _________
sour and salty
T/F: we can decrease our sensitivity to particular tast stimuli?
TRUE
if we are continuously exposed
complete adaptation in 1-5 min of continuous stimulation
Describe the initial steps in the gustatory pathway (from molecule to generation of AP)
- bite of food is chewed and dissolved into food molecules
- foot molecules dissolve in saliva
- food molecule binds receptor on gustatory receptor hair cell
- gustatory hair cell releases chemical messenger
- chemical messenger binds chemical gated channel on dendrite of pseudo unipolar taste neuron
- AP generated on peripheral process of pseudounipolar neuron of CN 7, 9, or 10
Describe the general steps in the gustatory pathway from generation of AP to integration of sensation
- AP is generated on peripheral process of pseudounipolar neuron of CN 7, 9, or 10
- travels to sensory ganglia for taste (3 different ganglia)
- then travels into brain stem in the solitary tract
- synapses on secondary neurons in gustatory portion of solitary tract
- Tertiary neuron in VPM of thalamus
- tertiary neuron head to Cerebral cortex an dlimbic system for integration
where in the cerebral cortex does taste differentiation occur?
insula
inferior postcentral gyrus
what is the limbic system’s role within the taste pathway?
emotional response to taste
what are the different sensory ganglia for taste?
- CN 7 → geniculate ganglia
- CN 9 → inferior petrosal ganglia of CN 9
- CN 10 → inferior (no dose) ganglia of CN 10
CN 7 is responsible for carrying sensory info from taste receptors in what areas?
anterior 2/3 of tongue
CN 9 is responsible for carrying sensory info from taste receptors in what areas?
posterior 1/3 of tongue
CN 10 is responsible for carrying sensory info from taste receptors located in what areas?
base of tongue/pharynx
what types of neurons make up CN 7?
- special sensory for taste (pseudo unipolar neuron)
- somatosensory
- somatic motor
- autonomic motor
what is type of info is carried within the somatosensory neurons of CN 7?
proprioception of muscles of facial expression
skin sensation of posterior ear, external auditory meatus
what type of info is carried within somatic motor neurons of CN 7?
motor efferent to muscles of facial expression, stapedius
what type of info is carried within autonomic motor neurons of CN 7?
preganglionic parasympathetic input headed to lacrimal and salivary glands
where is the primary sensory neuron soma located for the CN 7 sensory pathway?
geniculate ganglia within the petrous portion of temporal bone
where is the secondary sensory neuron within the CN 7 sensory pathway?
spinal (trigeminal) nucleus of CN 5
where is the tertiary sensory neuron within the CN 7 sensory pathway?
VPM of thalamus
after synapsing with the tertiary neuron, where does the sensory pathway of CN 7 head?
contralateral postcentral gyrus
Describe the motor pathway for CN 7
- precentral gyrus (UMN)
- corticobulbar tracts
- facial nucleus (LMN at lvl of open medulla/pons)
- CN 7 exits brainstem at junctin of pons and medulla
- CN 7 exits skull at stylomastoid foramen and divides in cutaneous nerves of partoid plexus
what are the branches of the partoid plexus?
- auricular nerve
- temporal branch
- zygomatic branch
- buccal branch
- marginal (mandibular) branch
- cervical branch
How does CN 7 innervate the stapedes muscle?
branch of CN 7 enters petrous portion of temporal bone through internal acoustic meatus and heads to the middle ear
somatomotor to stapedes muscle
what types of neurons is CN 9 comprised of?
- somatosensory from posterior ear
- special sensory for taste
- visceral sensory from carotid sinus and carotid body
- somatomotor to stylopharngeus muscle
- autonomic motor to salivary glands
what types of neurons is CN 10 comprised of?
- somatosensory from posterior ear and external auditory canal
- viscerosensory from thoracic and abdomen organs
- aortic arch baro- and chemoreceptors
- special sensory for taste
- somatomotor to pharyngeal and laryngeal muscles, and palatoglossus of tongue
- autonomic motor to organs of thorax and abdomen
what types of neurons in CN 11?
somatomotor to SCM and trapezius muscle
what types of neurons are in CN 12?
somatomotor to intrinsic and extrinsic muscles of tongue