Cranial Nerves Part 2 Flashcards
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
