Sensory Receptors
Sensory receptors are called this because they convert one form of energy (like light or pressure) into electrical signals
transducers
free nerve endings, root hair plexuses, and tactile discs are the three types of these, which lack a protective connective tissue covering
unencapsulated tactile receptors
before odorants can activate olfactory receptor cells, they must first dissolve into this substance covering the olfactory epithelium
nasal mucus (produced by olfactory/Bowman glands)
these are the three tunics (layers) of the eye, from outermost to innermost, each with distinct components
fibrous tunic (sclera + cornea), vascular tunic (choroid, cilliary body, iris), and retina
These three tiny middle ear bones, in order from eardrum to oval window, amplify and transmit sound vibrations to the inner ear
Malleus, incus, stapes
This is the term for the distribution area of a sensory neuron's dendrite endings. Smaller versions allow more precise stimulus localization
receptive field
this phasic encapsulated receptor detects deep pressure and high-frequency vibration. It is wrapped in neurolemmocytes and concerntric layers of CT.
lamellated (Pacinian) corpuscle
olfaction is unique among the senses because its signals project directly to the cortex, hypothalamus, and amygdala WITHOUT passing through this structure
the thalamus
this fluid continuously circulates in the anterior cavity, nourishing the avascular lens and cornea. Drainage failure leads to glaucoma
aqueous humor
The inner ear has two labyrinths. This one is bony and filled with perilymph; the membranous one inside it is filled with this potassium-rich fluid.
bony labyrinth / perilymph; membranous labyrinth / endolymph
Receptors are classified by stimulus origin into these three types: one for external stimuli, one for internal organs, and one for body/limb movement
exteroceptors, interoceptors, and proprioceptors
this tonic encapsulated receptor detects deep pressure and skin distortion (like stretching). it is wrapped in connective tissue in the dermis
Bulbous (Ruffini) corpuscle
for salty and sour tastes, the tastant (a metal ion or acid) depolarizes the gustatory cells directly by this mechanism, unlike sweet/bitter/umami which use G-proteins
the charged ions enter the cell directly through ion channels, depolarizing it without a second messenger
In the dark, rods continuously release this neurotransmitter onto bipolar cells, keeping them hyperpolarized and preventing ganglion cell signals. Light stops this release.
Glutamate
the three main regions of the bony labyrinth, one housing auditory receptors and two for equilibrium
cochlea (hearing), vestibule, and semicircular canals (equilibrium)
stimulus intensity is encoded by this property of action potentials, specifically how many neurons fire and how frequently.
frequency (rate) or nerve signals
referred pain occurs because somatic and visceral sensory neurons share these in the spinal cord, so the brain cannot determine the true source
the same ascending sensory tracts/pathways
taste signals travel via CN VII and IX to the nucleus solitarius in the medulla, then to the thalamus, and finally to the primary gustatory cortex located here
the insular lobe (insula) of the cerebrum
when focusing on nearby objects, cilliary muscles contract, the lens becomes more spherical, and this process increases light refraction. Name it.
Accommodation
middle ear infections commonly spread from the throat through this passage. Yawning or swallowing opens it to equalize air pressure on either side of the eardrum
the auditory (Eustachian) tube
these are the five types of sensory receptors classified by the modality of their stimulus (stimulating agent)
chemoreceptors, thermoreceptors, photoreceptors, mechanoreceptors, and nociceptors
in phantom limb pain, pain is perceived from a missing limb because this part of the sensory pathway is still intact and can still be stimulated
the remaining proximal portion of the sensory neuron pathway
these three cell types are found in both the olfactory epithelium and taste buds, performing parallel roles: detecting stimuli, supporting receptors, and replacing them
receptor cells (olfactory/gustatory), supporting cells, and basal cells
Optic nerve axons converge at the optic chiasm, where medial fibers cross to the opposite side. Most axons then travel to this thalamic nucleus before reaching the occipital cortex.
The lateral geniculate nucleus of the thalamus
these two small muscles contract to dampen ossicle movement during loud sounds, protecting the inner ear. Name both and which bone each attaches to
Tensor tympani (malleus) and stapedius (stapes)