lecture sensory

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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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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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


5/23Princip les of Human Anatomy and Physiology, 11e

Alternate Classifications of Sensory Receptors

Structural classification

Type of response to a stimulus

Location of receptors & origin of stimuli

Type of stimuli they detect



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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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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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


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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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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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Itch and Tickle

Itchand ticklereceptors are free nerve endings.

Tickle is the only sensation that you may not elicit onyourself.


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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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Free nerve endings found around follicles, detects

movement of hair

Hair Root Plexus


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Merkels Disc

Flattened dendrites touching cells of stratum basale

Used in discriminative touch (25% of receptors in hands)


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Ruffini Corpuscle

Found deep in dermis of skin

Detect heavy touch, continuous touch, & pressure


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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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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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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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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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lecture sensory

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