General senses Flashcards

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1
Q

Sensory receptors

A
  • adaptation: magnitude of response decreases over time in response to continuous stimulus
  • perception: remaining aware of sensation over time and interpreting what that sensation means in larger context
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2
Q

General senses

A

Microscopic receptors widely distributed in the skin, mucosa, connective tissues, mm, tendons, joints, and viscera
- somatic and visceral senses

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3
Q

Special senses

A

Localized receptors for

  • smell
  • taste
  • vision
  • hearing/equilibrium
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4
Q

Stimulation of the sensory receptor

A

Selectivity: a given receptor responds vigorously to one particular kind of stimulus (weakly or not at all to other stimuli) in its receptive field

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5
Q

Transduction of the stimulus

A

Converts energy in stimulus into graded potential

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6
Q

Generation of nerve impulses

A

Graded potential reaches threshold and triggers propagation toward CNS

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7
Q

Integration of sensory input

A

Regions of CNS and post central gyrus receive and integrate impulses

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8
Q

Classification of receptors

A
  1. Location
    - exteroceptors - visceroceptors (interceptors) - proprioceptors
  2. Stimulus
    - mechanoreceptors - chemoreceptors - thermoreceptors - nociceptors - photoreceptors - osmoreceptors
  3. Structure
    - free nerve endings - encapsulated nerve endings
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9
Q

Exteroceptors

A
  • located on or very near the body surface
  • respond most frequently to stimuli that arise external to the body itself
  • sometimes called cutaneous receptors (detect pressure, touch, pain, and temperature)
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10
Q

Visceroeptors (interoceptors)

A

Located internally

  • primarily in blood vessels and viscera
  • provide info regarding internal environment (usually not consciously perceived, if stimuli is strong may be perceived as pain or pressure)
  • activated by pressure, stretching, and chemical changes
  • involved in mediating sensations such as hunger, thirst, BP, full bladder
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11
Q

Proprioceptors

A
  1. Special type of visceroceptor
    - less numerous and more specialized than other visceroceptors
  2. Located in skeletal mm, joint capsules, and tendons
  3. Provide information regarding
    - body movement
    - orientation in space
    - mm stretch

Two types:

  1. Tonic: provides information while the body is at rest, non-adapting
  2. Phasic: provides information during movement. Rapidly adapting and triggered only when there is a change in position
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12
Q

Mechanoreceptors

A
  • detect mechanical stimuli that deform or change position of the receptor
  • ex: pressure to skin, blood vessels, that results in stretch or pressure in mm, tendon, or lung tissue
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13
Q

Chemoreceptors

A
  • detect chemicals in the mouth, nose, and body fluids
  • activated by either the amount or the changing concentration of certain chemicals
  • ex: sense of taste, smell, pH homeostasis
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14
Q

Thermoreceptors

A

Activated by changes in temperature

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15
Q

Nociceptors

A
  1. activated by intense stimulu that could result in tissue damage
    - chemical
    - intense light
    - sound
    - pressure
    - heat
  2. The sensation produced is pain
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16
Q

Photoreceptors

A
  • found only in the eyes

- detect light that strikes the retina

17
Q

Osmoreceptors

A
  • concentrated in the hypothalamus
  • sense levels of osmotic pressure in body fluids
  • activated by changes in concentration of electrolytes in extracellular fluids
  • stimulate the hypothalamic thirst center
18
Q

Free nerve endings

A
  • bare dendrites
  • the simplest, most common, and most widely distributed sensory receptors
  • include both exteroceptors and interoceptors
19
Q

Encapsulated nerve endings

A

have some type of connective tissue capsule that surrounds the terminal end or dendritic end

  • usually mechanoreceptors (activated by mechanical or deforming stimulus)
  • major types:
    1. Tactile/meissners corpuscle
    2. Lamellar/pacinian corpuscle
    3. Bulbous/ruffini cells
    4. Bulboid/Krause corpuscle
20
Q

Pic

A

Pic

21
Q

Sense of pain

A

Nociceptors-FREE nerve endings

  • primary sensory receptors for pain
  • 2 types: acute/fast pain and chronic/slow pain
22
Q

Pain A delta fibers

A
  • concentrated in the skin, mucous membranes, and other superficial areas
  • sharp, intense, localized fast/somatic pain
  • “fast pain” travels over myelinated fibers (250 ft/sec)
  • associated with superficial injury or trauma
23
Q

Pain C delta fibers

A
  • originates in deeper/visceral regions (thoracic and abdominal regions)
  • intense or less sever, but persistent, dull aching pain
  • develops more slowly over time
  • “slow pain” travels over unmyelinated fibers (3.5 ft/sec)
24
Q

Sense of temperature

A
  1. FREE nerve endings
    - mediate sense of heat and cold
    - called thermoreceptors
  2. Warm receptors
    - located in dermis
    - activated in temperature range of 77-114 degree F
    - >118 degrees = burning
  3. Cold receptors
    - located in deepest layer of epidermis
    - activated in temperature range of 50-104 degrees F
    - <50 dramatic decrease in firing rate but activates nociceptors (freezing pain)
25
Q

Sense of touch

A
  1. Types of touch sensations
    - skin movement
    - itch
    - tickles
    - light touch
    - deep touch
  2. Free and encapsulated endings
26
Q

Touch-skin movement

A

Root hair plexuses - FREE nerve endings

  • activated with very slight movement on or in the skin
  • bends or deforms a hair follicle or shaft
27
Q

Touch - Itch

A

Free nerve endings

  • activated by chemical irritation
  • inflammatory chemicals (bradykinin or histamine)
28
Q

Touch - Tickle

A

Free nerve endings

  • activated by touch from an outside source
  • involves both thalamus and cerebellum before reaching the cerebral cortex
29
Q

Light/discriminative touch

A

Mediated by a variation of a FREE nerve ending

  • tactile or nerves disk: transmits compression of the outer layer of skin to the tactile disk neuron (mechanoreceptors)
  • detects discriminative touch and surface form and contours
30
Q

Deep touch

A

Encapsulated nerve endings

  1. tactile/meissner corpuscles
    - enmeshed in connective tissue
    - located close to the dermal papillae in hairless skin areas like fingertips, lips, nipples, and genitals
  2. Mediate light touch, textural sensations, and low frequency vibration
31
Q

Anatomical variants of meissner corpuscles

A
  1. Bulboid/Krause corpuscle
    - more numerous in mucous membranes
  2. Bulbous/ruffini corpuscle
    - crude, heavy, and persistnat touch
  3. Lamellar/Pacini corpuscles
    - deep pressure, high frequency vibration, and stretch
32
Q

Sense of proprioception

A
  • tells us level of contraction and stretch in each of our skeletal muscles
  • proprioceptors (muscle spindles and Golgi tendon receptors)
33
Q

Muscle spindles

A

Encapsulated nerve endings

  • discrete grouping of 5-10 modified mm fibers called intrafusal fibers surrounded by sensory nerve fibers
  • respond to mm stretch (stretch reflex and subconscious postural adjustments)
34
Q

Golgi tendon organ

A

Encapsulated nerve endings

  • located at the junction between mm tissue and tendon
  • stimulated by excessive stretch of a tendon (when pulling too great a load for the muscles to bear—tension)
  • protects mm from tearing