LAB 10 GENERAL AND SPECIAL SENSES Last Lab Agenda Quiz General Senses Exercise 23 Touch Pain Temperature Pressure Propioception Special Senses Exercise 24 Vision Hearing Smell Taste Equilibrium Preceptor Presentation Cow Eye Dissection Practical Information Reminder TCEs Link is live now on d2l Remember if 80 students complete survey free question on the practical General vs Special Senses General Somatic and Visceral Somatic tactile touch pressure itch ect pain and proprioceptive sensations Visceral sensations coming from internal organs Sensory receptors are located throughout the body surface dermal layers Special Modified receptors that function to perceive a specific stimulus Sensory receptors are typically localized to a specific functional area e g retina Cutaneous Receptors Nociceptors Pain Receptors free nerve endings in the epidermis Detect chemical or physical damage Merkel Discs Touch receptors free nerve endings in stratum basale Meissner s Corpuscle Touch receptors encapsulated rapidly adapting and responsive to onset of touch Ruffini Corpuscle Touch strech receptors encapsulated deep in dermis Sensative to strech e g of limbs digits Hair Root Plexus Touch receptors free nerve endings detect movement on skin that moves hair follicles Pacinian Corpuscle Pressure receptor encapsulated rapidly adapting Free nerve endings dendrites First order sensory neuron with free nerve endings Cold stimulus Axon Triggers Propagate into CNS Nerve impulses Generator potential Axon First order sensory neuron with encapsulated nerve endings Pressure stimulus Encapsulated nerve ending Dendrite Gustatory taste receptor Sensory receptor synapses with first order sensory neuron Sugar molecule Synaptic vesicle Neurotransmitter Axon Dendrite Triggers Receptor potential Triggers Release of neurotransmitter from sensory receptor Propagate into CNS Nerve impulses Nociceptor pain receptor Epidermis Soma c Sensory Receptors Merkel tactile disc type I cutaneous mechanoreceptor Meissner corpuscle corpuscle of touch Dermis Ruffini corpuscle type II cutaneous mechanoreceptor Hair root plexus Pacinian lamellated corpuscle Subcutaneous layer Other Sensory Receptors Proprioception Muscle Spindle Detect muscle stretch activated in patellar and Achilles tendon reflexes Golgi Tendon Organ Detect force in the muscle found in the tendons of skeletal muscle Joint Kinesthetic Receptors Detect pressure in the capsules of joints responsive to acceleration and deceleration of joints during movement Proprioceptors Muscle Spindle Golgi Tendon Organ Phenomenon of Somatic Sensation Itch Stimulation of free nerve endings Typically caused by certain chemicals often resulting in local inflammation bradykinin Vibration Result of rapid and repetitive sensory signals Meissner corpuscle detect low frequency while Pacinian corpuscle detech high frequency Tickle Free nerve ending stimulation Can t tickle yourself due to cerebellar input Nociception Painful stimuli are carried to the CNS via nociceptive afferent fibers A fibers myelinated and C fibers unmyelinated A fibers carry fast pain and C fibers carry slow pain Fast Acute sharp or pricking Slow Chronic burning aching or throbbing Referred Pain Results from nociceptive activation in the visceral organs Typically feel pain elsewhere than from where the stimulus actually arises e g cardiac pain felt in left upper limb Visceral organ involved and area to which the pain is referred are served by same segment of spinal cord Soma c Sensa on Tests Review Heart Liver and gallbladder Lung and diaphragm Liver and gallbladder Stomach Heart Liver and gallbladder Gallbladder Pancreas Small intestine Stomach Ovary Ovary Kidney Urinary bladder Kidney Ureter a Anterior view b Posterior view Testing General Senses Density and Location of Touch Temperature Receptors Adaptation of Touch Adaptation of Temperature Two Point Discrimination Tactile Localization Referred Pain Density and Location of Touch and Temperature Receptors Only testing touch receptors Follow instructions What happened More tactile receptors than thermoreceptors in the the skin More cold than hot receptors in the skin Sensitivity of cold receptors vs hot receptors Adaption of Touch Receptors Not Tested Touch receptors adapt to constant stimulus by decreasing the number of action potentials they send over time Adaption of Temperature Receptors Follow instructions What happened Temperature receptors adapt to a constant stimulus by decreasing the number of action potentials they send over time Hand in hot bath adapts faster than cold because it is closer to body temperature Temperature receptors only adapt if temperature is not extreme Too hot or too cold nociceptors activated Past as certain range nociceptors will become active C fibers Temperature Receptors Two Point Discrimination Follow instructions What happened Areas with smaller receptive field have a greater receptor density and are better able to discriminate between two points These areas are more highly represented in primary somatosensory cortex homunculus Why would you be able to feel two close points on an area like the back low receptor density Tactile Localization Follow instructions What happened Test involves sensory and motor components Being able to match the same spot requires integration and proprioception The receptive field receptor density concept is the same as the two point discrimination Referred pain Follow instructions What happened Initially sensation of cold at the elbow but eventually digits IV and V begin to hurt The ulnar nerves serves that part of the hand so pain is referred to the hand even though damage is at elbow Soma c Sensa on Tests Review 1 Density and location of touch and temp receptors More tactile receptors than thermoreceptors More cold receptors than hot receptors 2 Adaptation of touch receptors Touch receptors adapt to a constant stimulus by decreasing the number of action potentials the send over time 3 Adaptation of temperature receptors Temperature receptors adapt by decreasing in number of action potentials the send over time Only adapt if the temperature is not extreme If temperature is extreme then Nociceptors are activated Soma c Sensa on Tests Review 4 Two point discrimination test we can discriminate two points in some areas of our body better than others the areas with smaller receptive fields Areas with higher receptor density are more highly represented on the primary somatosensory cortex 5 Tactile localization