Chapter 10 The Senses

1. Chapter 10The Senses 10.1-10.5

2. 10.1 Introduction

3. Introduction • Sensory receptors detect environmental changes • trigger nerve impulses • Travel along sensory pathways to CNS • Processed and interpreted

4. 2 Categories of Sensory Receptors • Receptors for somatic senses • Touch, pressure, temperature, and pain • Widely distributed throughout skin and deeper tissues • Structurally simple • Receptors for special senses • Smell, taste, hearing, equilibrium, and vision • Complex

5. 10.2 Receptors, Sensations, and Perceptions

6. Receptors, Sensation, and Perception • Each receptor is sensitive to one distinct type of stimulus • Sensation – raw form in which receptors send info to the brain • Perception – the way our brains interpret this info

7. 5 Types of Receptors • Chemoreceptors– stimulated by changes in chemical concentration of substances • Pain receptors – “ “ by tissue damage • Thermoreceptors – “ “ by changes in temperature • Mechanoreceptors – “ “by changes in pressure or movement • Photoreceptors – “ “ by light energy

8. Sensation and Perception • Sensation – occurs when the brain becomes aware of sensory impulses • All nerve impulses are the same • Perception – occurs when the brain interprets those sensory impulses • Depends on which region of the brain receives the impulse • Projection – brain projects the sensation back to its apparent source • Allows a person to pinpoint the region of stimulation

9. Sensory Adaptation • Your brain prioritizes! (otherwise overwhelmed) • Sensory adaptation – the ability to ignore unimportant stimuli • Peripheral adaptation – receptors become unresponsive • Central adaptation – inhibits pathways to sensory regions of the cerebral cortex

10. 10.3 General Senses

11. Touch and Pressure Senses • 3 receptors that sense mechanical forces that deform or displace tissues • Free nerve endings • Common in epithelial tissues • Responsible for itching • Tactile (Meissner’s) corpuscles • Abundant in hairless portions of skin • Responds to motion of objects that barely touch the skin • Lamellated (Pacinian) corpuscles • Common in deeper dermal and subcutaneous tissue • Respond to heavy pressure

12. Temperature Senses • Warm receptors • Free nerve endings that respond to warmer temps • 77 F-113 F • Cold receptors • Free nerve endings that respond to colder temps • Both adapt rapidly

13. Sense of Pain • Free nerve endings widely distributed throughout skin and internal tissues (NOT in the brain) • Protect the body since tissue damage stimulates them • Adapt poorly

14. Visceral Pain • Only receptors in viscera to produce sensations • Referred pain – visceral pain may feel as if it is coming from some part of the body other than the part being stimulated • Arises from common nerve pathways • Cerebral cortex incorrectly interprets the source of pain

15. Pain Nerve Fibers • Acute pain fibers • Thin and myelinated (conduct impulses rapidly) • Associated with sharp pain • Chronic pain fibers • Thin and unmyelinated (conduct impulses more slowly) • Associated with dull aching sensations • Both fibers are usually stimulated

16. Regulation of Pain Impulses • Awareness of pain in thalamus • Cerebral cortex determines intensity, source, and mediates emotional and motor responses • Enkephalins, seratonin and endorphins are released to block pain signals

17. 10.4 Special Senses

18. Special Senses • Senses whose sensory receptors are within large, complex sensory organs in the head

19. Special Senses Senses Respective Organs • Smell • Taste • Hearing • Equilibrium • Sight • Olfactory Organs • Taste buds • Ears • Ears • Eyes