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chemical senses .
gustatory, visceral afferents, and olfactory system
Taste is mediated by 3 differ cn
- VII - facial
- IX - glossapharyngeal
- X - vagus
visceral afferent system uses what common cn?
IX and X
Receptor cells in the gustatory system are?
taste buds that are separate from primary afferent fibers
primary afferent fibers from boht systems collect where
collect in solitary tract in rostral medulla and terminate in solitary nucleus
taste receptors are
modified epithelial cell present in taste buds locats on tongue, roof of mouth and pharynx
Ascending Gustatory pathway
- gustatory fibers ascend ipsilaterally in central tegmental tract. to medial port of VPN, to primary cortex (frontal operculum and anterior insular cortex)
- -mediates discriminative aspects of taste
what are the four primary types of taste receptors
sour, salt, sweet and bitter (new one: umami)
binding of receptor to taste molecule...
triggers entry of calcium in cell; release of neurotransmitter in synapse with neuron
taste impulses travel thru nerves VII, IX, and X to gustatory nucleus in medulla oblongata, to thalamus, to gustatory cortex located in parietal lobe in mouth area
Ascending Visceral Afferent system
- ascending projections synapse in parabrachial nucleus of pons, to VPM, to amygdala and hypothalamus
- -regulating visceral and food intake (assign emotion to food eaten)
- -regulate hunger
taste buds contain receptors
these receptor cells transduce soluble chemical stimuli into neural signal; have synaptic contacct with primary afferent fibers
on the tongue, we have...
what cn covers the tongue, plate, epiglottis, larynx, and pharynx?
- anterior 2/3 - VII
- posterior 1/3 IX
- palate - VII
- epiglottis, larynx - X
- pharynx -IX
IX, X have branches which serve arterial bp receptors in carotid sinus, aortic arch
x - repiratory structures, GIT, pseudounipolar neurons
Gustatory and visceral afferent systems come together where?
in the ganglion, just outside the brainstem
Olfactory system - cn?
- cranial nerve I
- -info goes to primary cortex with thalamic relay
- -primary olfactory cortex = phylogenetically older allocortex
- -projections to 5 separate cortical regions, rather than to just to 1 (all allocortex) [less developed in humans]
inability to smell
olfactory neurons in nasal mucosa is where and contains what?
in superior nasal conca contains bipolar neurons, which are chemosensitive, to small fasciculus, to cribiform plate of ethmoid bone, to olfactory nerve
- -surrounded by glial sheath
- -limits the spread of neurotransmitters, neurons, mitral, and tufted cells (olfactory tract)
other neurons receiving input
- periglomular cells (indirectly from olfactory nerve) and granule cells (from mitral cells
- -are inhibitory interneurons, provide feedback
anterior olfactory nucleus
modulates info processing in olfactory bulb
amygdala, in ant. temporal lobe
for self-regulation of various behaviors; via hypothalamus
role in regulating emotion
piriform +periamygdaloid cortices -
ant. temporal lobe, olfactory perception in: input in internal processing of odors, and projects frontal neocortical areas for olfactory discrimination (thru thalamus)
rostral entorhinal cortex
- -on parahippocampal gyrus
- -project to hippocampus
- -modulates associ. of odors with long-term memories
olfactory cortex constitutes 5 differ brain areas.
anterior olfactory nucleus, amygdala, olfactory tubercle, piriform/periamygdaloid cortices, entorhinal cortex
what binds to odorant molecules and what happens?
cilia binds to the molecules, binding triggers AP which is transmitted to olfactory area of olfactory bulb, to olfactory cortexx (lower front area and imbic system of the brain)