1. Chapter 9: The Senses

2. Sensory Receptors
Connect our internal and external environments with the nervous system
The general senses are:
Temperature
Pain
Touch
Pressure
Vibration
Proprioception
These receptors are located throughout the body.

3. The Special Senses They are: smell taste vision hearing equilibrium
The receptors are located in specialized areas or in sense organs.

4. A sensory receptor is a specialized cell that , when stimulated sends a sensation to the CNS.
The simplest receptors are free nerve endings
The most complex have specialized accessory structures that isolate the receptors from all but a specific type of stimulus
Each receptor cell monitors a specific receptive field..

5. General sensory receptors
Classified by the type of stimulus that excites them
Nociceptors respond to tissue damage
Fast pain: prickling pain
Slow pain: burning or aching pain
Referred pain: perception of pain in parts of the body not actually stimulated

6. Thermoreceptors: respong to changes in temperature Mechanoreceptors:
Tactile: touch (fine and crude)
Baroreceptors: pressure
Proprioceptors: position of joints and muscles

7. Olfaction: Smell Olfactory receptors respond to chemical stimuli
Olfactory epithelium contains olfactory receptor cells which are neurons sensitive to chemicals dissolved in the mucus

8. A bloodhound can distinguish smells at least 1,000 times better than a human
Their nose has 230 million olfactory cells 40X a human
Human olfactory epithelium is the size of a postage stamp, dogs are the size of a handkerchief
Humans can recognize about 10,000 scents.s
Looking at the genetics: humans have about 350 genes for odorant receptors, by contrast, mice have 1,300 such genes!

10. Gustation: Taste Taste receptors respond to chemical stimuli
Receptors are clustered in taste buds
Each taste buds contains gustatory cells
Taste buds are associated with papillae which are projections on the surface of the tongue.
The primary taste sensations are sweet, salty, sour, bitter, umami, and water.

12. How are your doing? 1. What is adaptation?
2. Receptor A has a circular receptive field with a diameter of 2.5cm. Receptor B has a circular receptive field 7.0cm in diameter. Which provides more precise sensory information?
3. What are the four types of general sensory receptors?

13. Keep going! 4. Define olfaction.
5. How does repeated sniffing help to identify faint odors?
6. Define gustation.
7. If you completely dry the surface of your tongue and then place salt or sugar crystals on it, you cannot taste them. Why not?