Sensory Receptors Classified based on stimulus type location

Sensory Receptors Classified based on: stimulus type, location & complexity Ø General senses: • touch, pressure, temperature, pain & body position Ø Special senses: • taste, smell, hearing, sight & equilibrium

Thermal Receptors Ø Warm receptors • sensitive to temperatures above 25 o. C (77 o F) • unresponsive to temperature above 45 o. C (113 o. F) Ø Cold receptors • sensitive to temperature b/t 10 o. C (50 o. F) & 20 o. C (68 o. F) Ø Pain receptors • respond to temperatures below 10 o. C • respond to temperatures above 45 o. C

Pain Receptors (Nociceptors) • Free Nerve Endings widely distributed in skin & Visceral pain receptors are the only receptors in viscera whose stimulation produces sensations • Stimulated by: tissue damage, chemical, mechanical forces, or extremes in temperature -- adapt very little, if at all • Referred Pain: pain feels as if coming from some other part of the body (projection)

Referred pain: may occur due to sensory impulses from two regions following a common nerve pathway to brain

Proprioceptors • Mechanoreceptors: send info to spinal cord & CNS about body position, length and tension of muscles • Three principal types: (1) Pacinian corpuscles – joints (2) Muscle spindles – skeletal muscles (3) Golgi tendon organs – tendons

Stimulus Reflex Arc: RACE-E Skin 1 Receptor Interneuron 2 Sensory neuron 3 Integration center 4 Motor neuron 5 Effector Spinal cord (in cross section)

Knee-jerk (Stretch) Reflex Monosynaptic reflex & Reciprocal inhibition

Withdrawal Reflex prevents or limits tissue damage

Crossed-Extensor Reflex Polysynaptic reflex