Somatic and special senses
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Somatic and Special Senses. Chapter 10. Introduction. Sensory Receptors - detect environmental changes and trigger nerve impulses that travel on sensory pathways into the CNS for processing and interpretation.

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  • Sensory Receptors- detect environmental changes and trigger nerve impulses that travel on sensory pathways into the CNS for processing and interpretation

2 large types of sensory receptors
2 large types of sensory receptors

  • 1. Somatic senses: touch, pressure, temperature, and pain

  • 2. Special senses: smell, taste, hearing, equilibrium, and vision

Receptors and sensations
Receptors and Sensations

  • Receptors are distinct to a type of environmental change

  • This selective response distinguishes the senses

  • 5 kinds

1 chemoreceptors
1. Chemoreceptors

  • Stimulated by changes in the chemical concentration of substances

2 pain receptors
2. Pain Receptors

  • Stimulated by tissue damage

3 thermoreceptors
3. Thermoreceptors

  • Stimulated by changes in temperature

4 mechanoreceptors
4. Mechanoreceptors

  • Stimulated by changes in pressure or movement

5 photoreceptors
5. Photoreceptors

  • Stimulated by light energy


  • Sensation-a feeling that occurs when the brain interprets sensory impulses

  • Impulse is read depending on what area of the brain receives it

  • One area may be sound and one area may be touch


  • Projection-process where the cerebral cortex causes a feeling to stem from a source

  • It allows a person to pinpoint the region of stimulation (eyes & ears)

Sensory adaptation
Sensory Adaptation

  • Sensory adaptation-sensory receptors stop sending signals when they are repeatedly stimulated

  • Can only be triggered if stimulus strength changes again

  • Think smell (phasic)

Somatic senses
Somatic Senses

  • 1. Sensory Nerve Fibers

    • Common in epithelial tissues

    • Are associated with touch and pressure

  • 2. Meissner’s Corpuscles

    • Small masses of connective tissue

    • Located in hairless portions of the skin (lips, fingertips, palms, soles, nipples, external genitalia)

    • Interpret light touch

  • 3. Parcinian Corpuslces

    • Large structures of connective tissue

    • Located in deep tissue layers like ligaments and tendons

    • Respond to heavy pressure

Temperature senses
Temperature Senses

  • 1. Warm Receptors - nerve endings that respond to warmer temperatures (sensitive above 77°, unresponsive above 113°F)

  • 2. Cold Receptors - nerve endings that respond to colder temperatures (sensitive between 50°F and 68°F)

Sense of pain
Sense of Pain

  • These protect the body because tissue damage stimulates them

  • Usually unpleasant and signals the person to remove the stimulation

  • Pain is persistent and doesn’t go away

  • Four types

1 visceral pain
1. Visceral Pain

  • Occurs in visceral tissues such as heart, lungs, intestine

2 referred pain
2. Referred Pain

  • Feels as though it is coming from a different part (heart pain may be felt as pain in arm or shoulder)

  • Caused from Nerves passing through the same area

3 acute pain
3. Acute Pain

  • Originates from skin, usually stops when stimulus stops (needle prick)

4 chronic pain
4. Chronic Pain

  • Dull aching sensations

Regulation of pain
Regulation of pain

  • Pain is interpreted by the Cerebral Cortex in the brain.

  • Three types of neuropeptides that inhibit pain: serotonin, enkephalins, endorphins.

  • Natural brain chemicals can be mimicked by drugs such as morphine.


Special senses
Special Senses

  • Smell: olfactory organs

  • Taste: taste buds

  • Hearing equilibrium: Ears

  • Sight: Eyes

Sense of smell
Sense of Smell

  • The sense of smell is associated with complex sensory structures in the upper region of the nasal cavity

Olfactory receptors
Olfactory Receptors

  • Chemoreceptors that are stimulated by chemicals that are dissolved in liquid

  • Aid in food selection because smell and taste are closely related

Olfactory organs
Olfactory Organs

  • Contain the olfactory receptors which are masses that cover the upper parts of the nasal cavity

Olfactory receptor cells
Olfactory Receptor Cells

  • Bipolar neurons surrounded by epithelial cells

  • Covered in cilia which have receptor proteins that the odor chemicals bind to

Olfactory bulbs
Olfactory Bulbs

  • Receive the nerve impulses from the receptor cells (located in the brain)

Olfactory tracts
Olfactory Tracts

  • Located inside the olfactory bulbs and interpret the nerve impulses

Smell Video