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

B ody Part Receptor Density (cm 2 )

Fingertip, palm surface Back of finger One eye 60 pain, 100 touch 100 pain, 9 touch 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.