General Senses

Human Anatomy and Physiology

L|E|C|O|M Mathew J. Bateman, Ph.D., D.H.Ed.

Properties of Receptors

What is a receptor?

What is a sense organ?

Receptors Transmit Information

Modality

Location

– sensory projection

Intensity

Duration

– Phasic receptors

– Tonic receptors

Receptive Fields

Tonic -vs- Phasic Receptors

Classification of Receptors

By modality:– chemo-, thermo-, mechano-, photo-

receptors and nociceptorsBy origin of stimuli

– interoceptors– proprioceptors– exteroceptors

By distribution– general senses – special senses

Unencapsulated Nerve Endings

Encapsulated Nerve Endings

Somesthetic Projection Pathways

1st order neuron 2nd order neuron3rd order neuron

Pain Signal Destinations

Referred Pain

Spinal Gating of Pain Signals

Pharmacology of Pain Management

• Receptor – Anti-inflammatory agents reduce pain stimuli

• Nociceptor transmitter of first order neuron– Substance P stimulates ascending pain neuron– Substance P inhibits inhibitory interneuron– Looking for antagonists now

• Presynaptic inhibition of first order neurons– Normal function of reticulospinal tract– Opiate peptides: enkephalins, endorphins, dynorphins

• Morphine, opium, etc mimic their effects • Sensory transmitter of first order neuron

– Stimulation of inhibitory interneuron– Inhibition (usually) of ascending pain neuron– Site of action of acupuncture, etc.