senses

receptors

Sensory input originates from

transduction

stimulus energy is converted into an electrical signal called a receptor potential

Mechanoreceptors

respond to touch, pressure, vibration, and stretch

Thermoreceptors

sensitive to changes in temperature

Photoreceptors

respond to light energy (e.g., retina)

Chemoreceptors

respond to chemicals (e.g., smell,

taste, changes in blood chemistry)

Nociceptors

sensitive to pain-causing stimuli (e.g.,

extreme heat or cold, excessive pressure, inflammatory

chemicals)

Exteroceptors

respond to stimuli arising outside the body;

located at or near body surface

• Receptors in the skin for touch, pressure, pain, and temperature

• Most special sense organs

Interoceptors

respond to stimuli arising

within the body (internal viscera and blood vessels)

• Sensitive to chemical changes, tissue stretch, and temperature

changes

Proprioceptors

respond to stretch in skeletal muscles,

tendons, joints, ligaments, and connective tissue coverings

of bones and muscles

• Inform the brain of one’s movements

Complex receptors

special sense organs

• Localized collection of cells

associated with special

senses

• Vision, hearing, equilibrium,

smell (olfaction), and taste

(gustation

Simple receptors

General senses:

• Most receptors are this

• Tiny; distributed throughout the body

• Tactile sensations (touch, pressure,

stretch, vibration), temperature, pain,

and muscle sense

• Cutaneous (skin) sensations

Unencapsulated

• Free nerve endings- pain,

temperature (heat &

cold)

• Hair follicle receptors-

hair movement

Encapsulated

• Tactile (Meissners) corpuscles-

light, discriminative touch

• Lamellar (Pacinian) corpuscles-

deep pressure, stretch &

vibration

• Bulbous corpuscle- deep

pressure & stretch

tactile Corpuscles

papillary layer of dermis is an example

lamellar Corpuscles

reticular layer of dermis is an example

Sensation

awareness of the stimulus

perception

conscious interpretation of the stimulus

Two- point threshold

smallest distance at which 2 points of contact can be felt

Smaller distance= higher density of receptors in

receptive field (more discriminative)

Tactile Localization

Brain’s ability to determine the area of the skin

being touched

Adaptation of receptors

When a stimulus is applied for a prolonged period

of time without moving, the rate of receptor

discharge slows, and conscious awareness of the

stimulus declines/is lost until stimulus change

occurs

Tonic Receptors

limited adaptation to a constant stimulus;

sensitivity to stimulus remains with continued exposure

Phasic Receptors

Rapid adaptation to a constant stimulus;

rate of discharge slows when a stimulus is applied for a long

period of time; generate

Referred Pain

Pain perceived in one area of the body when the

stimulus occurs in another area

• Free nerve endings are being stimulated for this

activity