Part 1: General Senses

General Senses

Receptors that are widely distributed throughout the body

Special senses

Specialized receptors confined to structures in the head

Sensory Receptors

collect information from the environment, and relay it to the CNS on sensory neurons

Exteroceptive senses

Senses associated with body surface, such as touch, pressure, temperature, and pain

-Type of General Sense

Interoceptive (visceroceptive) senses

Senses associated with changes in the viscera, such as blood pressure stretching blood vessels

-Type of General Sense

Proprioceptive senses

 Senses associated with changes in muscles, tendons, and joints, as when changing position or exercising

-Type of General Sense

Chemoreceptors

Respond to changes in chemical concentrations (smell, taste, oxygen concentration)

-Type of Sensory Receptor

Nociceptors

Respond to tissue damage (mechanical, electrical, thermal energy)

-Type of Sensory Receptor

Thermoreceptors

 Respond to moderate changes in temperature

-Type of Sensory Receptor

Mechanoreceptors

Respond to mechanical forces that distort receptor (touch, tension, blood pressure, stretch)

-Type of Sensory Receptor

Photoreceptors

Respond to light (eyes)

-Type of Sensory Receptor

Sensation

A feeling that occurs when brain becomes aware of sensory information

Perception

The way the brain interprets the sensory information

Projection

brain determines the source of sensation

Sensory Adaptation

Ability to ignore unimportant (or continuous) stimuli

Free nerve endings (Merkel’s Disks)

Common in epithelial tissues. Lie between epithelial cells. 

Sense light touch and can create itching sensations

slow-adapting

type of mechanoreceptors

Tactile (Meissner’s) corpuscles:  (light touch)

Abundant in hairless areas of skin, such as lips, fingertips, palms

Detect  fine touch and texture

Distinguish between 2 points on skin

fast-adapting

type of mechanoreceptors

Lamellated (Pacinian) corpuscles: (deep pressure)

Large oval structures

Common in deeper subcutaneous tissues, tendons and ligaments

Detect heavy pressure and vibrations

slow-adapting

type of mechanoreceptors

Warm receptors

Sensitive to 25 - 45^oC (77 - 113^o F)

Cool Receptors

Sensitive to 10 - 20^oC (50 - 68^oF)

Pain receptors

Respond to temperatures below 10^oC; freezing sensation

Respond to temperatures above 45^oC; burning sensation