1. General sensory receptor structure
1.1. Free nerve endings: dendrites interspersed among other cells/tissues (pain, temperature, touch)
1.2. Encapsulated nerve endings: dendrites with special supporting structures (mechanoreceptors and proprioceptors)
2. Classification by Complexity
2.1. Simple receptors
2.1.1. Usually a single modified dendrite
2.1.2. General senses
2.1.2.1. Touch
2.1.2.2. Pressure
2.1.2.3. Pain
2.1.2.4. Vibration
2.1.2.5. Temperature
2.2. Complex receptors
2.2.1. High modified dendrites, organized into complex structures
2.2.2. Eye, ear
2.2.3. Specific senses
2.2.3.1. Vision
2.2.3.2. Hearing
2.2.3.3. Smell
2.2.3.4. Taste
3. Classification by Structure
3.1. Free Nerve Endings
3.1.1. Abundant in epithelia and underlying connective tissue
3.1.2. Respond to pain and temperature
3.1.3. Monitor affective senses
3.1.4. Two specialized types of free nerve endings
3.1.4.1. Merkel discs
3.1.4.1.1. Lie in the epidermis
3.1.4.1.2. Slowly adapting receptors for light, touch
3.1.4.2. Hair follicle receptors
3.1.4.2.1. Wrap around hair follicles
3.1.4.2.2. Rapidly adapting receptors
3.2. Encapsulated Nerve Endings
3.2.1. Consist of one or more end fibers of sensory neurons
3.2.2. Enclosed in connective tissue
3.2.3. Encapsulated nerve endings: dendrites with special supporting structures (mechanoreceptors and proprioceptors)
3.2.4. Include four main types
3.2.4.1. Meissner’s corpuscles
3.2.4.2. Pacinian corpuscles
3.2.4.3. Ruffini’s corpuscles
3.2.4.4. Propioceptors
3.2.4.4.1. Monitor stretch in locomotory organs
3.2.4.4.2. Three types of proprioceptors
4. Classification of Peripheral Sensory Receptors
4.1. Adaptability
4.1.1. Sustained stimulation leads to adaptation – Tonic receptors – Phasic receptors
4.2. Location
4.3. Type of stimulus detected
4.4. Complexity
4.5. Structure
5. • Receptors are specialized nerve cells that transduce energy into neural signals – Receptors lack axons, form synapses with dendrites of other sensory neurons
6. Classification by Adaptability • Sustained stimulation leads to adaptation
6.1. Tonic Receptors • Slow or no adaptation • Continuous signal transmission for duration of stimulus • Monitoring parameters that must be continually evaluated, e.g.: baroreceptors
6.2. Phasic Receptors • Rapid adaptation • Cease firing if strength of a continuous stimulus remains constant • Allow body to ignore constant unimportant information, e.g.: – Smell
7. Classification by Location
7.1. Externoceptors
7.1.1. Located on the body surface and specialized to detect external
7.1.2. Pressure, pain, temp, touch, etc.
7.2. Interoceptors (Visceroceptors)
7.2.1. Located within internal organs, detect internal stimuli
7.2.2. Blood pressure, pain, fullness
7.3. Proprioceptors
7.3.1. Found in the joint, muscles, in the vestibular structures especially in semicircular canals of the inner ear
7.3.2. Body position and movement
8. Classification by Modality
8.1. Mechanoreceptors
8.1.1. Detects stimuli which mechanically deform the receptor
8.1.2. Pressure, vibration, touch, sound
8.2. Thermoreceptors
8.2.1. Detects changes in temperature
8.2.2. Hot or cold
8.3. Photoreceptors
8.3.1. Detect light
8.3.2. Vision, retina of the eye
8.4. Electroreceptors
8.4.1. Detect electric fields
8.5. Chemoreceptors
8.5.1. Detect chemical stimuli
8.5.2. CO2 and O2 in the blood, glucose, smell, taste
8.6. Magnetoreceptors
8.6.1. Detect magnetic fields