Human Touch and Pain Receptors Somatosensory System • Somoesthetic sensations – Sensations associated with skin receptors • Proprioception – Perception and position of the body including limbs 3 Receptor Types • Mechanoreceptors – Pressure, force, vibration • Thermoreceptors – Temperature • Nociceptors – Tissue damaging stimuli Definitions • Modality – Energy form of stimulus • Sensory neurons convert energy from stimulus into another form of energy. • Receptor potentials – Graded responses caused by closing and opening of ion channels. – Number activated and frequency of APs generated correlated to stronger stimulus intensity perceived. Mechanoreceptors • Detect stimuli • Two main forms: – Specialized structure on peripheral end of afferent neuron. – Separate cell that communicates via chemical synapses with associated afferent neuron. Thermoreceptors • Respond to surrounding tissue, not air temp. • Warm receptors – Respond to temps 35-45 °C – Beyond 45 °C APs decrease rapidly – Above 45 °C nociceptors also. Thermoreceptors • Cold receptors – Respond to to temps 20-35 °C – Below 25 °C APs decrease rapidly – Below 10 °C also nociceptors – Also respond to temps above 45 °C • Paradoxical cold receptors Nociceptors • 3 Types – Mechanical – Thermal – Polymodal Wet Receptors? • Brain integrates info from different sensory systems. • Combination of thermoreceptors and mechanoreceptors. Receptor Density Body Part Receptor Density (cm2) Fingertip, palm surface 60 pain, 100 touch Back of finger 100 pain, 9 touch One eye 90,000,000!!!!!!!!! Homework!!!! • Write a methods, results, and introduction. • Answer ALL questions. • This may be done within the results section or introduction. Make sure you include a section with answers to questions that you don’t answer within the intro or results sections. • You do not have to replicate the figures from the pdf for today. Just staple that to your lab report. Introduction • Successfully establishes the physiological concepts of the lab. • Effectively presents the objectives and purpose of the lab. • States hypotheses AND provides logical reasoning for them.