Animal Physiology MechanoreceptionMechanoreceptor Ion Channels-Two types of mechanoreceptor proteins:oENaCs (epithelial sodium channels)oTRP (transient receptor potential channels Stretch activated ion channels with two attachment pointsExtracellular matrix proteinsCytoskeleton-Mechanical forces cause displacement of extracellular anchoring proteins resulting in conformational change-Absence of intracellular cascade (mechanoreceptors are ion channels connected to cytoskeleton)-Similar sensory transduction in inverts and vertebrates-Location and/or peripheral filtering mechanisms determine whether activated by sound, gravity, acceleration, or water currents.-Figure 6.12: Mechanosensory protein complexesoDrosophila touch receptors contain mecahnosensory neurons with TRP-type channels in their membranes.oMechanical stimuli cause the extracellular anchors to move relative to the cytoskeleton, pulling on the channel and causing a conformational change that opens or closes the channel, changing the membrane potential of the cell.Types of mechanoreceptors-Touch and PressureoBaroreceptors (vertebrates)oTactile receptors (vertebrates and inverts)oProprioceptors (verts and inverts)-Equilibrium and Hearing (verts and inverts)oStatocystsoHair cellsoNeuromastsoElectroreceptorsTouch and PressureBaroreceptors (verts)-Detect pressure changes in wall of blood vessels, parts of the heart, digestive, reproductive and urinary tracts-E.g. Carotid sinus baroreceptors: monitor blood pressure to the brain.-When it stretches it sends a message. Found anywhere in the body that needsto know what is going on. -The baroreceptors help our body figure out what is in its pipes.
Tactile Receptors(verts)-Detect touch pressure vibration on the bodyoTonic receptor cells.oDetect light touch and pressure on the skin surface.-Free nerve endingsoSensory neurons with dendrites interspersed among epidermal cellsoReceptor proteins on the dendrites-Merkel’s Disk:oEnlarged epidermal cell (Merkel cells) associated with free nerve endings.oSmall receptive field (fine discrimination)-Phasic receptor cells; detect movement or pressure on skin surface-Root Hair plexus:oNerve endings wrap around base of hair follicles (respond when hair displaced)oPhasic receptorsoDetect changes in movement across the body surface-Pacinian CorpuscleoSensory dendrite surrounded by lamellaeoLocated in skin (deep), muscles, joints, and internal organsoPhasic receptors, detect changes in pressureoLarge receptive field, poor discrimination, especially sensitive to vibration,-Ruffini CorpuscleoDendrite endings with elongated capsuleoLocated in connective tissue of the skin and movement of jointsoHelp detect position of body in space (proprioceptor)Tactile Receptors(inverts)-What do you do when you have a cuticle?