1. Nervous System III
Chapter 12

2. Introduction General senses Special senses
Receptors widely distributed
Skin, organs, etc.
Special senses
Receptors generally confined to head structures
Eyes, ears, nose, mouth

3. Sensory receptors
Specialized nervous cells that collect info from environment
Sends info along sensory (afferent) nerves to the brain

4. Types of sensory receptors
Pain via chemicals released during tissue damage
Nociceptors

5. Transferring info to the brain
Stimulation of receptor- chemical changes
Electrical current generated
Can cause action potential, if stimuli is large enough
Peripheral nerves transmit impulses to CNS
Analyzed and interpreted in CNS

6. Sensation and Perception
Sensation- brain becomes aware of sensory event
Perception- brain’s interpretation of the sensory event
Pain vs. realization of what caused the pain

7. Sensory Adaptation Ability to ignore unimportant stimuli
Decreased sensory impulses
Can refocus attention

8. Hypokalemic sensory overstimulation

9. General Senses
Receptors located all over body- skin, muscles, joints, etc.
Three groups
Exteroceptive senses
Associated with body surface (touch, pressure, temp, pain)
Visceroceptive senses
Associated with changes in organs (blood pressure stretch, stomach receptors)
Proprioceptive senses
Associated with changes in muscles, tendons (body position, movement)

10. Exterioceptors Free nerve endings Common in epithelial tissues
Simplest receptors
Sense itching
Tactile (Meissners) corpuscles
Abundant in hairless portions of skin and lips
Detect fine touch and texture
Lamellated (Pacinian) corpuscles
Common in deeper subcutaneous tissues, tendons and ligaments
Detect heavy pressure and vibrations

11. Epidermis
Dermis
(a)
(b)
(c)
Section of
skin
Free nerve
endings
Epithelial
cells
Sensory (afferent)
nerve fiber
Tactile
(Meissners)
corpuscle
(touch receptor)
Lamellated
(Pacinian)
(pressure receptor)
Connective tissue

12. Nociceptors Pain receptors Free nerve endings
Widely distributed (exterio and viscero)
Stimulated by tissue damage, chemical release
Brain tissue

13. Pain receptors Only visceroreceptors that produce a sensation
Brain doesn’t do a good job localizing
Referred pain

14. Referred Pain Appendix Ureter Lung and diaphragm Heart Stomach
Pancreas
Colon
Kidney
Urinary bladder
Liver and
gallbladder
Small
intestine
Ovary
(female)

15. Visceroceptors Receptors in internal organs
Conveys info such as fullness, gas, pain originating from internal organs

16. Proprioception Mechanoreceptors (stretch receptors)
Sends info to CNS about body position and length, tension of muscles

17. Stretch receptors Sensory (afferent) nerve fiber nerve endings
Muscle spindle
Sensory
(afferent)
nerve fiber
nerve endings
Connective
tissue sheath
Intrafusal
fiber
Skeletal muscle