Phys Final Study Guide PDF

Chapter 8: Somatosensory Neurotransmission Intro ○ Sensory receptors convert specific forms of energy into action potentials in sensory neurons. ○ Cutaneous mechanoreceptors mediate responses to touch and pressure ○ Proprioceptors in muscles, tendons, and joints relay information about muscle length...

Chapter 8: Somatosensory Neurotransmission Intro ○ Sensory receptors convert specific forms of energy into action potentials in sensory neurons. ○ Cutaneous mechanoreceptors mediate responses to touch and pressure ○ Proprioceptors in muscles, tendons, and joints relay information about muscle length and tension ○ Thermoreceptors detect the sensations of warmth and cold ○ Nociceptos respond to potentially harmful stimuli such as pain, extreme heat, and extreme cold ○ Chemoreceptors are stimulated by change in the chemical composition of the local environment These include receptors for taste and smell as well as visceral receptors that are sensitive to changes in the plasma level of O2, pH and osmolality ○ Photoreceptors in the rods and cones in the retina respond to light Sensory receptors & Cutaneous mechanoreceptors ○ Touch and pressure are sensed by 4 types of mechanoreceptors Meissner corpuscles are dendrites encapsulated in connective tissue beneath the epidermis of glabrous (non hairy) skin and respond to slow vibration Merkel cells are expanded dendritic endings in epidermis of glabrous skin that respond to sustained pressure Ruffini corpuscles are enlarged dendritic endings with elongated capsules in the dermis of glabrous and hairy skin; they respond to stretch and fluttering vibration Pacinian corpuscles are the largest cutaneous mechanoreceptor, 2mm long and about 1 mm in diameter, in the dermis of glabrous and hairy skin They are comprised of nerve ending encapsulated by concentric layers of connective tissue that give it an onion appearance These receptors respond to fast vibration and deep pressure The sensory nerves from cutaneous mechanoreceptors are myelinated Aa and AB fibers whose conduction velocities range from 70-120 to 40-75 m/s respectively Nociceptors ○ Pain and temperature sensations arise from receptors located on unmyelinated dendrites of sensory neurons located throughout the glabrous and hairy skin as well as deep tissue. ○ Mechanical nociceptors respond to strong pressure (from sharp object) ○ Thermal nociceptors are activated by skin temperatures about 45*C or by severe cold (