Chapter 10: Sensory Physiology Flashcards
Free dendritic endings
Sense pain and temperature
Encapsulated dendritic endings
sense touch and pressure
- non-neural components (modified epithelial cells like hairs in inner ear and taste buds)
Chemoreceptors
sense chemicals (taste and smell) or blood
Photoreceptors
sense light
Thermoreceptors
sense temperature
Mechanorecpetors
stimulated by mechanical deformation (touch or hearing)
Nocireceptors
Pain receptors that depolarize when tissues are damaged
Proprioreceptors
in muscles, tendons, and joints
- sense body position and fine muscle control
Cutaneous receptors
sense touch, pressure, heat, cold, and pain
Tonic receptors
high firing rate maintain as long as the stimulus is applied
Phasic receptors
respond with a burst of activity when stimuli is first applied, but quickly adapt to stimulus by lessening responses
Generator Potential
local graded changes in membrane potential due to stimulation of receptors
Pacinian corpuscle
light touch = small generator potential
- increased pressure = higher generator potential magnitude until threshold is met and action potential occurs
- “graded potential”
Ruffini corpuscles
dermis for skin stretch
Meissner’s corpuscles
dermal papillae for movement across the skin
Merkel’s discs
stratum basal of epidermis for skin indentation
Receptive Fields
Size of the field depends on the density of receptors in that region of skin
- large in the back and legs
- small in the fingertips
Lateral inhibition
Receptors that are very strongly stimulated inhibit those around them
- allows us to perceive well-defined sensations at a single location instead of “fuzzy” borders
Papillae
Taste buds, bumps on the tongue
Fungiform
papillae on the anterior surface of the tongue
- info travels via facial nerve
Circumvallate
papillae on the posterior surface of the tongue
- info travels via glossopharyngeal nerve
Foliate
papillae on the sides of the tongue
- info travels via glossopharyngeal nerve
Sensing Salt
Na+ enters taste cell and depolarizes it
Sensing Sour
H+ enters the cell and depolarizes it
Sensing Sweet/Unami
sugar/glutamate binds to receptor and activates G-protein or 2nd messengers to close K+ channels
Sensing bitter
Quinine binds to receptor actives G-protein or 2nd messenger to release Ca2+ into the cell
Olfactory Apparatus
receptors are located in the olfactory epithelium of the nasal cavity
- made of bipolar olfactory sensory neurons, supporting cells, and basal stem cells
How smell works (steps)
- G-protein couples
- Odor-binding activates adenylate cyclase to make cAMP and PPi (pyrophosphate)
- cAMP opens Na+ and Ca2+ channels
- Produces a graded depolarization which stimulates the action potential
Pathway of Light
- through the cornea and into the anterior chamber of the eye
- through the pupil
- through the lens
- through the posterior chamber and the vitreous body
- hits the retina and photoreceptors
Glaucoma
damage to the optic nerve
- loss of retinal ganglion cell axons, cannot regain vision
Lens Accomodation
Ability of the lens to keep an object focused on the retina as the distance between the eye and object moves
Contraction (Lens)
of ciliary muscles allow suspensory ligaments to relax and lens to thicken/round
- good for close vision
Relaxation (Lens)
of ciliary muscles pulls suspensory ligaments and lens thins/flattens
- good for distant vision
Visual Acuity
sharpness of vision
- measured with Snellen eye chart
Myopia
Nearsightedness
- Point of focus is in front of retina
- elongated eyeball
- corrected by concave lens
Hyperopia
Farsightedness
- point of focus is behind the retina
- short eyeball
- corrected by convex lens
Astigmatism
Asymmetry of the cornea and/or lens curvature = several points of focus
- corrected by cylindrical lenses
Retina
has an epithelial and neural layer
Optic Disc
Blind spot
- neural axons in the retina are gathered at a point
Rods
allows for black-and-white vision at low light
Rhodopsin
purple pigment that absorbs green light the best
- absorption dissociates it into retinaldehyde and opsin
Cones
allows for color vision and high visual acuity, sensitive to light
S cones
short wavelengths
BLUE
M cones
medium wavelengths
GREEN
L cones
large wavelengths
RED
Color blindness
lack of one or more types of cones
- more common in men (genes are on the X chromosome)
- commonly red-green colorblindness (involving L or M cones)
