Chapter Thirteen: Touch Flashcards
Somatosensation
nociception(pain) + proprioception (determining position of body) + kinesthesis (where our muscles are moving) + sensing temp changes + pressure/vibrations
Transduction
One form of energy to another
Receptors
Cells that transduce
Touch receptors
Embedded in epidermis, also in dermis. Three attributes:
1) Type of stimulation receptor responds to (pressure, vibration, temp change).
2) size of receptive field
3) Rate of adaptation - Fast vs. slow
Mechanoreceptors
respond to mechanical stimulation or pressure
Tactile Receptors in Hairless Skin (palms)
4 Types:
•Meissner corpuscles - FA1, small receptive fields, epidermis
•Merkel cell neutrite complexes - SA1, small RF, epidermis
•Pacinian corpuscles - FA2, large RF, dermis
•Ruffini endings - FA, large RF, dermis
Table in notes: learn
Terminal to dorsal root of spinal chord, very long.
Kinesthetic Receptors
play role in sensing where limbs are, what kinds of movements are made
Spindles
convey rate at which muscle fibers are changing in length. Receptors in tendons provide signals about tension in muscles attached to tendons. Receptors in joints come into play when joint is bent to extreme angle.
Ian Waterman
Cutaneous nerves connecting kinesthetic mechanoreceptors to brain is severed in viral infection. Lacked kinesthetic sense, relied on vision to move muscles.
Thermoreceptors
Sensory receptors that signal information about changes in skin temperature. Two distinct populations of thermoreceptors: warmth fibers, cold fibers. Body is consistently regulating internal
temperature. Thermoreceptors kick into gear when you make contact with object warmer or colder than your skin.
Spatial Localization of Heat is Poor
Cain focuses radiant heat on torso, unable to locate heat. Only sensitive to change.
Nociceptors
Sensory receptors that transmit information
about noxious stimulation that causes damage or potential damage to the skin. Two groups of nociceptors: A-delta fibers - respond to strong pressure/ heat and are myelinated, conduct signal rapidly. C-fibers - unmyelinated, respond to intense stimulation. Both small compared to A-beta.
Miss C
Born with insensitivity to pain, could not protect herself.
Touch signals travel as far as 2 meters to get from skin and muscles of feet to brain!
Info must pass thru spinal chord. Axons of various tactile receptors combine into single nerve trunks. Several nerve trunks from different areas of body. Once in spinal chord two major pathways: spinothalmic (slower, carries info from thermo/noci. More synapses but provides mechanism to inhibit pain), dorsal-column-medial-lemniscal (faster, less synapses, carries info from muscles, tendons, joints).
Thalamus
Two parallel pathways for somatosensory signals. Thalamus is sensory relay station.
