Chapter 10, part A Sensory Physiology

About this Chapter What are the senses How sensory systems work Body sensors and homeostatic maintenance Sensing the external environment Mechanisms and pathways to perception

General Properties of Sensory Systems Stimulus Internal External Energy source Receptors Sense organs Transducer Afferent pathway CNS integration

General Properties of Sensory Systems Figure 10-4: Sensory pathways

Sensory Receptor Types Structural types: Simple receptors Complex neural Special senses Types according to the nature of stimulus Chemoreceptors Mechanoreceptors Thermoreceptors Photoreceptors

Sensory Receptor Types Figure 10-1: Sensory receptors

Special Senses – External Stimuli Vision Hearing Taste Smell Equilibrium

Special Senses – External Stimuli Figure 10-4: Sensory pathways

Somatic Senses – Internal Stimuli Touch Temperature Pain Itch Proprioception Pathway Figure 10-10: The somatosensory cortex

Somatic Pathways Receptor Threshold Action potential Sensory neurons Primary – medulla Secondary – thalamus Tertiary – cortex Integration Receptive field Multiple levels

Somatic Pathways Figure 10-9: Sensory pathways cross the body’s midline

Sensory Modality Location Lateral inhibition Receptive field Intensity Duration Tonic receptors Phasic receptors Adaptation

Figure 10-3: Two-point discrimination Sensory Modality Figure 10-3: Two-point discrimination

Sensory Modality Figure 10-6: Lateral inhibition

Touch (pressure) Mechanoreceptors Free nerve endings Pacinian corpuscles Ruffini corpuscles Merkel receptors Meisaner's corpuscles Barroreceptors

Touch (pressure) Figure 10-11: Touch-pressure receptors

Temperature Free nerve endings Cold receptors Warm receptors Pain receptors Sensory coding: Intensity Duration

Temperature Figure 10-7: Sensory coding for stimulus intensity and duration

Pain and Itching Nociceptors Reflexive path Itch Fast pain Slow pain

Pain and Itching Figure 10-12: The gate control theory of pain modulation

Referred Pain Figure 10-13: Referred pain