B2W3 Sensory Transduction Flashcards
Taste Anatomy Breakdown
Papillae > Bud > Pore > Receptor
5 Primary Taste qualities
Salty
Sour
Sweet
Bitter
Umami
Taste Receptor Cells
Modified epithelial cells
- Only detect 1 quality of taste
Salt and Sour Taste Pathway
Ionotropic Increase in Na influx
Salt Pathway
Increase sodium concentration in mouth -> Na moves through always open Na channels to depolarize the cell -> Calcium entry into the cell -> Release of vesicular serotonin
Sour Pathway
H+ ions activate TRPP3 channels to allow the flow of Na into the cell and inhibits K+ channels -> Causes depolarization -> Calcium entry into the cell -> Release of vesicular serotonin
Sweet, Bitter, and Umami Pathway
Metabotropic Mechanism (Gaq) -> Activation of GPCR -> Subunit activates Phospholipase C -> PLC changes PIP2 into DAG and IP3 -> IP3 initiates the release of intracellular Ca from the ER -> Increased concentration of Ca opens Ca dependent Na channels -> Na flows into the cell causing depolarization -> Release of NON VESICULAR ATP
Olfaction Cell Types
Basal Cells
- Stem Cells that replace dying receptor cells
Support Cells
- Produce Mucus
Olfactory Receptors
- Site of transduction
How is odor information determined
Each neuron synapses differently to determine the different smells
Olfactory Pathway
Odorant Molecule binds to GPCR (G Olfactory or Golf protein) -> Alpha subunit activates Adenylate Cyclase -> Adenylate Cyclase changes ATP into cAMP -> cAMP opens CNG ion channels which allows mainly Na and Ca and some K to enter the cell (it is a nonselective channel) -> Increased Ca concentration opens Ca activated Cl channels -> Cl- moves out of the cell -> results in depolarization
Where does most focus happen in vision
Anterior surface of the cornea due to different refractive index
Air 1
Cornea 1.3
Eye Accommodation
Increase focal power to see closer objects
Ciliary muscles contract causing zonal fibers to release tension and the lens to become rounder
Myopia
Nearsightedness
Eye is too long causing images to focus in front of retina
Distant images are blurry but can see close up
Hyperopia
Farsightedness
Eye is too short causing image to focus behind retina
Near images are blurry but can see far away
Astigmatism
Uneven curvature of the eye
Problem focusing everything
Pupillary Light Reflex
Light shone into one eye will cause both irises to constrict
Pathway of Pupillary light reflex
Light activates preganglionic parasympathetic neurons which go through the Edinger-Westphal Nucleus which goes to both eyes and then synapse on ciliary ganglia which activates postganglionic parasympathetic neurons to cause pupil constriction
Yoked pupillary response
Both pupils react
Retina
Area in the eye containing photoreceptors
Types of Photreceptors
Rods and Cones
Rods
Low light black and white slow
Cones
Bright light color vision fast
C for color
Distribution along the retina
Fovea or center of retina
- High resolution high density of cones
- 1 to 1 ratio of photoreceptors to sensory afferent
Periphery
- Higher Density of Rods
- More sensitive to light but low spatial resolution
Phototransduction in the dark
In the dark photoreceptors are depolarized and continuously release glutamate
- Large inward Na current in the outer segment and outward current of K in the inner segment
Phototransduction in Light
Retinal absorbs light and undergoes a confirmational change in opsin to become Metarhodopsin II-> Metarhodopsin II activates transducin (G-Protein) -> Alpha subunit activates phosphodiesterase -> Phosphodiesterase converts cGMP into GMP -> loss of cGMP causes inward sodium channels to close -> hyperpolarizes the cell
Rhodopsin
Opsin (Receptor Protein) and Retinal (Photosensitive component)
What neurotransmitter is released by photoreceptors?
Glutamate
