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 DensityBody Part

Fingertip, palm surfaceBack of finger

One eye

Receptor Density (cm2)

60 pain, 100 touch100 pain, 9 touch90,000,000!!!!!!!!!

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.