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Nervous System III Chapter 12.

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Presentation on theme: "Nervous System III Chapter 12."— Presentation transcript:

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


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