Chapter 15: Sensory Pathways
Sensory Receptors : specialized structures designed to respond to changes in their environment (outside or inside)

Overstimulation of any receptor is perceived as painful
A. Special Senses

(vision, hearing, equilibrium, smell, taste) receptors located in sense organs
B. General Senses (simple in structure)

Tactile sensations (touch, pressure, vibration), Temperature regulation, Pain

Majority of receptors have modified dendritic endings
1. Sensation –
2. Perception
–
3. Transduction -

If transduction does not occur, as far as you know, the stimulus did not occur
Detection of stimulus

Receptor specificity a. Free nerve endings (simple). No accessory structures

Receptor field a. Take many forms

Receptor potential a. pushes threshold, if large enough it produces a generator potential (AP)
Tonic Receptors
Phasic Receptors
Adaptation

Fast-adapting receptors

Slow-adapting receptors
Receptors are classified by location, type of stimulus they detect, and by the relative complexity of their structure
1. 3 classes according to Location a. Exteroreceptors i. near or at body surface include:

b. Interoreceptors i. Monitor c. Proprioceptors i. respond to changes in length, located only in skeletal muscles and joints
2. According to Stimulus Type Detected a. Nociceptors i. Fast pain ii. Slow pain b. Thermoreceptors c. Mechanoreceptors i. Tactile Receptors (touch, pressure, vibration)
1. Fine vs Crude touch
2. Free nerve endings
3. root hair plexus
4. Tactile discs (Merkel discs)
5. Tactile corpuscles (Meissner’s)
6. Lamellated corpuscles
7. Ruffini corpuscles ii. Baroreceptors d. Proprioceptors i. Muscle spindles ii. Golgi Tendon Organs iii. Joint kinesthetic receptors e. Chemoreceptors i. Carotid or Aortic bodies
Pathways
1 st order
2nd order
3 rd order
Somatic sensory
A. Posterior column pathway a. Decussation
B. Anterolateral Pathway

C. Spinocerebral a. Posterior b. Anterior
Visceral Sensory