Sensory receptors are structures that detect changes in the environment called stimuli. They are classified by their location, the stimulus they detect, and their structure. The main types are exteroceptors that detect external stimuli, interoceptors that detect internal stimuli, and proprioceptors that detect body position. Receptors are also classified by the stimulus they detect, such as mechanoreceptors for touch, thermoreceptors for temperature, photoreceptors for light, and chemoreceptors for chemicals. Vertebrates have specialized receptors like taste buds that detect the four basic tastes, and olfactory receptors in the nasal cavity that detect smells.

1. SENSORY RECEPTORS

2. What are sensory receptors?
Structures that are specialized to respond
to the changes in the environment
These are called stimuli
Sensory receptors in periphery detects the
stimuli
Sensation and interpretation takes place in
the brain

3. How sensory receptors are
classified?
Location - location of the stimulus
to which they respond
Stimulus type - named by the stimulus
that activates them
Structure - the anatomy of the
receptor

4. Classification according to location
Exteroceptors
- any receptor that responds to stimuli
outside the body such vision, sound, touch, smell,
temperature and smell

6. Interoceptors or visceroceptors
- respond to stimuli arising within the
body such as chemical stimuli, deep
pressure, and many others.

8. Proprioceptors
- respond to muscle or tendon stretch
and help the body monitor body position

9. Classification according to stimulus type
Mechanoreceptors
- respond to a mechanical stimulus:
examples are touch, pressure, stretch,
hearing, balance, position and movement,
vibration, muscle contraction, as well as
press receptors and bar receptors.

11. Thermoreceptors
-respond to temperature change:
example heat and cold.

12. Photoreceptors
-respond to light: example vision

14. Chemoreceptor
-respond to various chemicals such as
glucose, oxygen, carbon dioxide,
hormones and many, many more

15. This pseudostratified columnar epithelium
is composed of olfactory cells,
sustentacular cells and basal cells.
Modified cilia on the surface serve as
olfactory receptors.

16. Nocireceptors
- pain receptors from any noxious
stimulus

18. Classification according to structure
Simple ( large majority )
- similar to modified dendritic endings
- found on skin, mucous membrane,
muscles and connective tissues

19. Location of simple receptors

20. Complex (sense organs)
- localized collection of cells that works
together to perform a specific process
- also known as special senses

21. Vertebrates Sensory Receptors
Chemoreception
-Vertebrates usually accomplish
chemoreception by moving chemically rich
air or water into a canal or sac that
contains the chemical receptors.

22. Specialized receptors of vertebrates
Gustatory receptors
- The receptors for the gustatory nerves are known
as taste buds located on the tongue and the roof of the
mouth. Sweet, sour, bitter, and salty are the four basic
taste sensations resulting from stimulation of the taste
buds and the stimulation of the olfactory receptor. This is
why it is harder to taste when one has a cold. These four
basic tastes may evolutionarily developed to show some
basic food properties. Sweet taste signals foods high in
calories, salty foods signal for food that helps maintain
water balance, sour tastes may help to signal foods that
could be dangerous if eaten in excess, and bitter taste
sensations signal toxic foods.

24. Taste buds

25. Olfactory receptors
- The receptors for the olfactory nerves are located in the
upper part of the nasal cavity. The olfactory sense organ
consists of hair-like cells at the end of a neuron and is
simple compared to the complex visual and auditory
organs. The olfactory receptors are very sensitive to
stimuli; however, they also become very fatigued. This
explains why odors seem to go away after being easily
noticeable. Canals lined with sheets of receptors with the
nasal cavity are called turbinate. Protruding from the end
of the nerve are thin cilia that are covered by mucus.
Molecules are absorbed into the mucous layer and passed
to the cilia where the chemical is detected. Notice the
chemicals must be dissolved in the mucus and absorbed in
order for the olfactory receptors to react. This is a lot
like the gustatory mechanisms.