Special senses Flashcards
what are papillae
raised structures on tongue
4 types of papillae
filiform, fungiform, circumvallates, foliate
filiform location and characteristic
Anterior 2/3rds of tongue. no taste buds, just gives tongue friction
fungiform location and characteristic
Anterior 2/3rds of tongue. have taste buds
Circumvallates location and characteristic
V-shape dividing anterior 2/3rds and posterior 1/3rd. there are 7 to 14 of these, have taste buds
foliate location and characteristic
side of tongue. have tastebuds
3 types of cells making up taste buds
supporting cells (specialised epithelium)
gustatory receptor cells
basal cells
gustatory receptor cell characteristics
NOT neurons. have a hair that sticks out of the taste pore
gustatory basal cells
Base of taste buds have basal epithelial cells essentially stem cells. Will become gustatory receptor cells when prompted by chemicals or damage
5 tastes and their sources
i. Sweet (sugars, alcohol, amino acids)
ii. Sour (acids, H+)
iii. Salty (inorganic salts, NaCl—any positive and negative ion together)
iv. Bitter (bases, nicotine, caffeine, toxins/poisons)
v. Umami (delicious, glutamate)
what must be present for taste to work
solution (saliva)
how do gustatory receptor cells activate
i. Two of the gustatory receptor cell types activate directly through Na+ channels (salty) and H+ channels (sour)
ii. Sweet, bitter, umami utilizes G protein gustducin to turn on ion channels
gustatory innervation and pathways
- Anterior 2/3rds of tongue: glossopharyngeal nerve to medulla -> thalamus -> cortex
- Posterior 1/3rd: facial nerve -> medulla -> thalamus -> cortex
- Taste buds on epiglottis: vagus nerve -> medulla -> thalamus -> cortex
where is the gustatory centre
insula
what two additional brain areas play a role in gustation
frontal cortex (quality discrimination) and hypothalamus (ANS control of rest/digest)
4 influences of taste
i. Smell makes up 70-80% of taste
ii. Thermoreceptors
iii. Mechanoreceptors (pressure, texture)
iv. Nociceptors—spicy
olfactory epithelium vs. resporatory epithelium
- Respiratory epithelium is made up of ciliated pseudostratified columnar epithelium and covers our respiratory tract. Present in the nasal conchae and meatuses
- Olfactory epithelium is found at the top of the nasal cavity. Present here are olfactory sensory cells (1st order neurons) with non motile cilia that bind to odorants. They are buried in mucus which acts like flypaper for odorants
olfactory basal cells
olfactory stem cells: become olfactory sensory neurons, replaced every 1-2 months. One of very few areas of nervous system with cell regeneration
olfactory glands
Bowman’s glands/olfactory glands manufactures mucus
how many smells do we smell and how
i. We can smell ≈10,000 different smells, way more than tastes
ii. We have 400-1,000 smell genes which make proteins (olfactory receptors). Each protein can bind to 2-3 types of odorants, and odorants can bind to 2-3 different proteins. The overlap combinations creates lots of different smells.
olfactory transduction
G proteins open up Na+ channels for stimulatory EPSP or open Ca+ channels which cause IPSP and causes adaptation
olfactory pathway
olfactory sensory cells (bipolar 1st order neurons) travel up through tiny holes in the cribriform plate of ethmoid bone, these holes are called olfactory foramina.
• Superior to foramina they synapse with second order neurons called mitral cells. The axons of mitral cells make up the olfactory cranial nerve.
• Processes from olfactory receptor cells and processes from mitral cells come together and form balls called glomeruli. Similar odorants are processed in the same glomerulus.
• Olfactory nerve bypasses the thalamus and goes to olfactory cortex, then to frontal cortex and hypothalamus and amygdala (limbic system)
another word for eyelid
palpebra
fissure
the opening between eyelids when open