Nervous System III Chapter 12

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

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

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

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

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

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

Hypokalemic sensory overstimulation

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)

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

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

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

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

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

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

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

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

http://www.youtube.com/watch?v=FKxyJfE831Q http://topdocumentaryfilms.com/the-man-who-lost-his-body/