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8/10/2019 Lecture Sensory
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8/10/2019 Lecture Sensory
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Princip les of Human Anatomy and Physiology, 11e
Is Sensation Different from Perception?
Sensationis a conscious or unconscious awareness of
external or internal stimuli.
Sensation is any stimuli the body is aware of
Chemoreceptors, thermoreceptors, nociceptors,baroreceptors
Perception is the conscious awareness & interpretation of
a sensation.
precisely localization & identification memories of our perceptions are stored in the cortex
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Princip les of Human Anatomy and Physiology, 11e
Sensory Modalities
Sensory Modalityis the property by which one sensation is
distinguished from another.
Different types of sensations
touch, pain, temperature, vibration, hearing, vision
Generally, each type of sensory neuron can respond to
only one type of stimulus.
Two classes of sensory modalities
The general sensesinclude both somatic and visceral
senses, which provide information about conditions
within internal organs.
The special sensesinclude the modalities of smell,
taste, vision, hearing, and equilibrium.
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Princip les of Human Anatomy and Physiology, 11e
Sensory Receptors
Receptor Structure may be simple or complex
General Sensory Receptors (Somatic Receptors) no structural specializations in free nerve endings tha
provide us with pain, tickle, itch, temperatures
some structural specializations in receptors for touch
pressure & vibration Special Sensory Receptors (Special Sense Receptors)
very complex structures---vision, hearing, taste, & sm
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Alternate Classifications of Sensory Receptors
Structural classification
Type of response to a stimulus
Location of receptors & origin of stimuli
Type of stimuli they detect
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Structural Classification of Receptors
Free nerve endings
-pain,
temperature,
tickle, itch & ligh
touch
Encapsulated nerve
endings-pressure, vibration &
deep touch
Separate sensory cells
-vision, taste, hearing,
balance
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8/10/2019 Lecture Sensory
8/23Princip les of Human Anatomy and Physiology, 11e
Classification by Response to Stimuli
Generator potential
free nerve endings, encapsulated nerve endings & olfactory
receptors produce generator potentials Receptor potential
vision, hearing, equilibrium and taste receptors producereceptor potentials
Amplitude of potentials vary with stimulus intensity
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Princip les of Human Anatomy and Physiology, 11e
Classification by Location
Exteroceptors
near surface of body receive external stimuli
hearing, vision, smell, taste, touch, pressure, pain,vibration & temperature
Interoceptors
monitors internal environment (BV or viscera)
not conscious except for pain or pressure
Proprioceptors
muscle, tendon, joint & internal ear
senses body position & movement
8/10/2019 Lecture Sensory
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Princip les of Human Anatomy and Physiology, 11e
SOMATIC SENSATIONS
Tactile Sensations
Tactile sensationsare touch, pressure, and vibration plus itchand tickle.
receptors include
corpuscles of touch (Meissners corpuscles),
hair root plexuses,
type I (Merkels discs)
type II cutaneous (Ruffinis corpuscles)
mechanoreceptors,
lamellated (Pacinian) corpuscles,
free nerve endings
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Princip les of Human Anatomy and Physiology, 11e
Touch
Crude touchrefers to the ability to perceive that something has
simply touched the skin Discriminative touch (finetouch)provides specific information
about a touch sensation such as location, shape, size, and
texture of the source of stimulation.
Receptors for touch include corpuscles of touch(Meissners
corpuscles) and hair root plexuses; these are rapidly adapting
receptors.
Type I cutaneous mechanoreceptors (tactile or Merkel discs)and type II cutaneous mechanoreceptors (end organs of
Ruffini) are slowly adapting receptors for touch.
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8/10/2019 Lecture Sensory
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Princip les of Human Anatomy and Physiology, 11e
Itch and Tickle
Itchand ticklereceptors are free nerve endings.
Tickle is the only sensation that you may not elicit onyourself.
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Princip les of Human Anatomy and Physiology, 11e
Meissners Corpuscle
Dendrites enclosed in CT in dermal papillae of hairless skin
Discriminative touch & vibration-- rapidly adapting
Generate impulses mainly at onset of a touch
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Princip les of Human Anatomy and Physiology, 11e
Free nerve endings found around follicles, detects
movement of hair
Hair Root Plexus
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Princip les of Human Anatomy and Physiology, 11e
Merkels Disc
Flattened dendrites touching cells of stratum basale
Used in discriminative touch (25% of receptors in hands)
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Princip les of Human Anatomy and Physiology, 11e
Ruffini Corpuscle
Found deep in dermis of skin
Detect heavy touch, continuous touch, & pressure
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Princip les of Human Anatomy and Physiology, 11e
Pacinian Corpuscle
Onion-like connective tissue capsule enclosing a dendrite
Found in subcutaneous tissues & certain viscera
Sensations of pressure or high-frequency vibration
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Princip les of Human Anatomy and Physiology, 11e
Somatic Tactile Sensations - Summary
Touch
crude touch is ability to perceive something has touched thskin
discriminative touch provides location and texture of source
Pressure is sustained sensation over a large area
Vibration is rapidly repetitive sensory signals
Itching is chemical stimulation of free nerve endings
Tickle is stimulation of free nerve endings only by someone els
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Princip les of Human Anatomy and Physiology, 11e
Pain Sensations
Pain receptors(nociceptors) are free endings that are
located in nearly every body tissue
Free nerve endings found in every tissue of body
except the brain
adaptation is slight if it occurs at all.
Stimulated by excessive distension, muscle spasm, &
inadequate blood flow
Tissue injury releases chemicals such as K+, kinins or
prostaglandins that stimulate nociceptors
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Princip les of Human Anatomy and Physiology, 11e
Proprioceptive Sensations
Receptors located in skeletal muscles, in tendons, in and
around joints, and in the internal ear convey nerve impulsesrelated to muscle tone, movement of body parts, and body
position. This awareness of the activities of muscles, tendons,
and joints and of balance or equilibrium is provided by the
proprioceptiveor kinesthetic sense.
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