Sensory Tortora

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    Chapter 16:Sensory, Motor,

    and Integrative Systems

    Copyright 2009, John Wiley & Sons, Inc.

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    Sensation ,Perception & Integration

    Sensationis the detection of stimulus of internal or external receptors. It

    can be either conscious or subconcious

    Components of sensation: Stimulation of the sensory receptor

    transduction of the stimulus (energy-to-graded potential) generation of

    nerve impulses integration of sensory input.

    Perceptionis the awareness and conscious interpretation of sensations. It

    is how the brain makes sense of or assigns meaning to the sensation.

    We not aware of X-rays, ultra high frequency sound waves, UV light

    - We have no sensory receptors for those stimuli

    Integrationof sensory and motor functions occurs at many sites:

    spinal cord brain stem cerebellum basal nuclei cerebral cortex Disruption of sensory, motor, or integrative structures or pathways can

    cause disruptions in homeostasis

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    Classification of Sensory Receptors

    General senses: somatic and visceral.

    Somatic- tactile, thermal, pain, pressure and proprioceptive sensations.

    Visceral- provide information about conditions within internal organs.

    - example: pH. Osmolarity, O2 and CO2 levels

    Special senses- smell, taste, vision, hearing and equilibrium or balance.

    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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    Alternate Classifications of Sensory Receptors

    Structural classification

    Type of response to a stimulus

    Location of receptors & origin of stimuli Type of stimuli they detect

    Principles of Human Anatomy andPhysiology, 11e 4

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    Structural Classification of Receptors

    Free nerve endings

    bare dendrites

    pain, temperature, tickle, itch & light touch

    Encapsulated nerve endings

    dendrites enclosed in connective tissue capsule pressure, vibration & deep touch

    Separate sensory cells

    specialized cells that respond to stimuli

    vision, taste, hearing, balance

    Principles of Human Anatomy andPhysiology, 11e 5

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    Copyright 2009, John Wiley & Sons, Inc.

    Structural Classification of Rec

    eptors

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    skin, bones, internal organs, joints

    Naked nerve endings surrounded

    by one or more layers

    Pacinian corpuscle

    Free nerve endings

    Encapsulated Nerve

    EndingsvsUnencapsulated

    Nerve Endings

    Deeper tissue, muscles

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    free nerve endings

    root hair plexus

    Meissnerscorpuscles

    Paciniancorpuscles

    Ruffini corpuscle

    Merkel disc

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    Classification by Stimuli Detected

    Mechanoreceptors detect pressure or stretch

    touch, pressure, vibration, hearing, proprioception,

    equilibrium & blood pressure

    Thermoreceptorsdetect temperature

    Nociceptorsdetect damage to tissues (pain)

    Photoreceptorsdetect light

    Chemoreceptorsdetect molecules

    taste, smell & changes in body fluid chemistry

    Principles of Human Anatomy andPhysiology, 11e 9

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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

    Principles of Human Anatomy andPhysiology, 11e 10

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    Classification by Response to Stimuli Generator potential

    free nerve endings, encapsulated nerve endings & olfactory receptorsproduce generator potentials

    when large enough, it generates a nerve impulse in a first-order neuron

    Receptor potential

    vision, hearing, equilibrium and taste receptors produce receptorpotentials

    receptor cells release neurotransmitter molecules on first-orderneurons producing postsynaptic potentials

    PSP may trigger a nerve impulse

    Amplitude of potentials vary with stimulus intensity

    Principles of Human Anatomy andPhysiology, 11e 11

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    Table 15.1 pt 1

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    Table 15.1 pt 2

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    Table 15.1 pt 3

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    Adaptation of Sensory Receptors Most sensory receptors exhibit adaptationthe tendency for the generator

    or receptor potential to decrease in amplitude during a maintained constant

    stimulus.

    Receptors may be rapidly or slowly adapting.

    Rapidly adapting receptors: detect pressure, touch and smell.

    - specialized for detecting changes

    Slowly adapting receptors: detect pain, body position, and chemicalcomposition of the blood.

    -nerve impulses continue as long as the stimulus persists

    Pain is not easily ignored.

    Change in sensitivity to long-lasting stimuli decrease in responsiveness of a

    receptor

    bad smells disappear

    very hot water starts to feel only warm

    potential amplitudes decrease during a maintained, constant stimulus

    Copyright 2009, John Wiley & Sons, Inc.

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    Somatic Sensations

    Sensory receptors in the skin (cutaneous

    sensations), muscles, tendons and joints and

    in the inner ear.

    Uneven distribution of receptors. (tongue,lips, fingertips)

    Four modalities: tactile, thermal, pain and

    proprioceptive.

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    Sensory Receptors in the Skin

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    Tactile Sensations

    Include touch, pressure, vibration, itch and

    tickle.

    Tactile receptors in the skin are Meissner

    corpuscles, hair root plexuses, Merkel discs,Ruffini corpuscles, pacinian corpuscles, and

    free nerve endings.

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    Meissner Corpuscles or Corpuscles of

    Touch Egg-shaped mass of dendrites enclosed by a

    capsule of connective tissue.

    Rapidly adapting receptors.

    Found in the dermal papillae of hairless skin

    such as in the fingertips, hands, eyelids, tip of

    the tongue, lips, nipples, soles, clitoris, and

    tip of the penis.

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    Hair Root Plexuses

    Rapidly adapting touch receptors found in the

    hairy skin.

    Free nerve endings wrapped around hair

    follicles.

    Detect movements on the skin surface that

    disturb hairs.

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    Merkel Discs or Tactile Discs

    Also known as type I cutaneous

    mechanoreceptors.

    Slowly adapting touch receptors.

    Saucer-shaped, flattened free nerve endings.

    Found in the fingertips, hands, lips, and

    external genitalia.

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    Ruffini Corpuscles

    Also called as type II cutaneous

    mechanoreceptors.

    Elongated, encapsulated receptors.

    Located deep in the dermis and in ligaments

    and tendons.

    Found in the hands, and soles.

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    Pacinian or Lamellated Corpuscles

    Large oval structure composed of a

    multilayered connective tissue capsule that

    encloses a dendrite.

    Fast adapting receptors.

    Found around joints, tendons, and muscles;

    in the periosteum, mammary glands, external

    genitalia, pancreas and urinary bladder.

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    Thermal Sensations

    Thermoreceptors are free nerve endings.

    Two distinct thermal sensations:

    cold receptors-

    warm receptors-

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    Pain Sensations

    Protective.

    Sensory receptors are nociceptors .

    Free nerve endings.

    Two types of pain: fast and slow.

    Fast pain: acute, sharp or pricking pain.

    Slow pain: chronic, burning, aching or

    throbbing pain.

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    Referred Pain

    Pain is felt in or just deep to the skin that

    overlies the stimulated organ or in a surface

    area far from the stimulated organ.

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    Distribution of Referred Pain

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    Muscle Spindles

    Interspersed among most skeletal muscle

    fibers and aligned parallel to them.

    Measure muscle stretching.

    Consists of intrafusal muscle fibers-

    specialized muscle fibers with sensory nerve

    endings and motor neurons called gamma

    motor neurons. Extrafusal muscle fibers- surrounding muscle

    fibers supplied by alpha motor neurons.

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    A Muscle

    Spindle and a

    Tendon

    Organ

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    Tendon Organs

    Located at the junction of a tendon and a

    muscle.

    Protect tendons and their associated muscles

    from damage due to excessive tension.

    Consists of a thin capsule of connective

    tissue that encloses a few tendon fascicles.

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    Joint Kinesthetic Receptors

    Found within or around the articular capsules

    of synovial joints.

    Free nerve endings and Ruffini corpuscles in

    the capsules of joints respond to pressure.

    Pacinian corpuscles respond to acceleration

    and deceleration of joints during movement.

    Copyright 2009 John Wiley & Sons Inc