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54 Cards in this Set
- Front
- Back
What are exteroreceptors?
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Resond to stimuli from the outside environment (cutaneous sense, vision, olfaction, hearing)
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What are interoreceptors?
What are some types? (4) |
Respond to stimuli inside body
1. Proprioceptor = respond to movement and body position 2. Visceroreceptor = stretch of internal organ or muscular contraction 3. Chemoreceptor = changes n chemical environment 4. Baroreceptor = changes in pressure |
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What is sensation?
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Conscious or unconscious awareness of external or internal stimuli
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What is perception?
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Conscious awareness and interpretation of a sensation
Allows us to create a perceptual representation of our environment |
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What is modality?
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Specific type of sensation
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What is transduction?
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Conversion of one form of energy to another
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What is conduction?
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Propagation of a signal to a distant site in the nervous system --> APs
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Type A-alpha (I) fibers
a. Morphology b. Sensory modalities c. Conduction |
a. Large, myelinated
b. muscle spindles, motor axons c. fast (50 m/s) |
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Type A-beta (II)
a. Morphology b. Sensory modalities c. Conduction |
a. Large, myelinated
b. Vibration, pressure, touch, stretch c. Fast (50m/s) |
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Type A delta (III)
a. Morphology b. Sensory modalities c. Conduction |
a. Small myelinated
b. Touch, cold, pain c. Moderate (20m/s) |
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Type C (IV)
a. Morphology b. Sensory modalities c. Conduction |
a. Small unmyelinated
b. cold, warm, thermal pain c. Slow (2m/s) |
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Type B
a. Morphology b. Sensory modalities c. Conduction |
a. Small, myelinated
b. Autonomics c. Medium (10 m/s) |
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What are deep tendon reflexes?
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Comprised of large fibers that carry muscle stretch information
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What is the result of a process that affects large, myelinated sensory fibers?
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Absence of deep tendon reflexes
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What happens in tabes dorsalis (damange to large, myelinated fibers)?
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Balance problems due to loss of joint position sense
Pain sensitivity increase |
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What is the implication of the fact that large fibers have a lower activation threshold for clinical treatment?
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Can stimulate large fibers with low, non-painful electrical currents applied to the skin or nerve and suppress painful stimuli
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Where do sensory bodies of sensory neurons lie?
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Outside of the spinal cord in the DRG
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What is the pathway of large fiber sensation (vibration, proprioception, stretch)?
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Enters spinal cord via medial part of dorsal root --> ascend in ipsilateral dorsal column --> nucleus gracilis/fasciculis) ipsilaterally
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What is the pathway for small fiber sensation (pain and temp)?
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Enter lateral division of dorsal root --> ascend dorsal horn --> synapse on secondary neuron in cord and cross to contralateral side --> up anterolateral tract
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Hair receptors
a. Innervation b. adaption speed c. Arrangement d. Consist of what? |
a. A-beta and A-delta
b. fast adapting (respond quickly, recover quickly) c. Arranged parallel to shaft d. Neurites (nerve terminals) sandwiched between two buns of Schwann cell cytoplasm |
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Pacinian corpuscles
a. Fibers b. adaption speed c. Sensitive to...? d. Consist of...? |
a. A-beta
b. fast adapting c. Minimal skin distortion, vibration (up to 500 Hz) d. Laminated corpuscles with central naked axon (can have more than one) |
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WHat are some places to find Pacinian corpuscles (8)?
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Dermis
Subcutaneous tissue Ligaments Joint capsules Pleura Peritoneum Nipples External genitalia |
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How does one test Pacinian corpuscle integrity in the skin?
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Vibratory testing
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Meissner's corpuscles
a. Fibers b. adaptation c. Sensitive to...? d. consist of...? |
a. A-beta
b. fast-adapting c. Low frequency oscillation up to 40 Hz (flutter) d. laminated corpuscle supplied by several nerve fibers that intertwine through the lamellae |
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Where are Meissner's corpuscles located?
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Superficially in dermal papillae of fingers, palmar surface of hands, plantar surface of feet
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What is the difference between flutter and vibration?
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Flutter = feeling of repetitive movement
Vibration = diffuse and penetrating, like humming |
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What special sensory function are Meissner's corpuscles important for?
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two-point discrimination
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Merkel's Disc
a. Fibers b. Adaptation c. sensitive to...? d. mode of signaling |
a. A-beta
b. slow-adapting c. Light static pressure for discrimination of shapes, edges, and textures d. Rapid initial burst, followed by a sustained rate of discharge proportional to the degree of skin indentation (steady state) |
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Where are Merkel cells found? (4)
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Hairless skin such as fingertips, lips, external genitalia, hair follicles
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What is the role of proprioceptors?
Where are they found? |
Provide information about static limb position, sense of movement
Located in muscle, tendons, joint capsules, and ligaments |
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What do large diameter type Ia sensory fibers innervate?
What are the role of the structures that these innervate? |
Coil around and innervate muscle spindles
Muscle spindles provide information about muscle stretch |
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What do type 1b fibers innervate?
What is the role of the organs they innervate? |
Golgi tendon organ receptors
Golgi tendon organs inform the CNS of the degree of muscle tension |
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What do afferents from muscle spindles connect with? (2)
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1. Excitatory monosynaptic connections with alpha motor neurons innervating the respective muscle --> deep tendon reflex
2. Inhibitory polysynaptic contact with motor neurons innervating muscle antagonists |
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What do afferents from the Golgi tendon organ synapse with? (2)
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1. Interneurons in spinal cord --> inhibit motor neurons innervating muscle of origin
2. Excitatory connections with motor neurons of antagonistic muscles |
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How do thermoreceptors sense temperature?
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Warming of the skin --> activate warm fibers, silence cold fibers
Cooling of the skin --> activate cool fibers, silence warm fibers |
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What type of adaptation speed do warm and cold fibers have?
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Slow adapting = sustained discharge related to skin temperature
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What are cold fibers?
Warm fibers? |
Cold = A-delta, C
Warm = C |
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What is fast pain?
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Short latency, short duration, well-localized pain conducted through A delta fibers
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What is slow pain?
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More diffuse, longer-duration, burning sensation conducted by slower C fibers
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What is the structure of all pain receptors?
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Free nerve endings with terminal specializations
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What are mechanical nociceptors?
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Respond to pinch or pressure
NOT to light touch or temp |
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What are polymodal nociceptors?
Type of fibers? |
Respond to chemicals, high intensity mechanical and thermal stimulation
C fibers |
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What senses visceral pain?
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Nocireceptors sensitive to stretch or distension of visceral organs
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How do pain fibers show traits of slow and fast adaptation?
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Recover slowly after a stimulus
BUT do not discharge continuously |
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What is sensitization?
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Repeated stimulations are increasingly effective in generating a response in some pain fibers eg. polymodal nociceptors
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What do chemoreceptors detect?
What is the pathway? |
Detect chemical stimulus
GPCR --> adenylate cyclase --> cAMP --> increase channel conductance --> depolarize receptor membrane |
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What do mechanoreceptors sense?
What is the pathway? |
Stretch or tension
Stimulus pulls carbohydrate chains anchored in EC space/membrane cytoskeleton --> stress on conformation of channel proteins --> increased conductance |
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What are 4 examples of mechanoreceptors?
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Pacinian corpuscles
Meissner's corpuscles Free nerve endings Proprioceptors |
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What happens with increased intensity of stimulus?
With increased duration of stimulus? |
Increased intensity --> greater number and frequency of APs
Longer stimulus duration --> longer the train of APs generated |
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What is sensory adaptation?
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Decline in generator potential with time
Slow and fast |
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What are 2 examples of slow adaptation?
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Merkel's cells
thermal receptors |
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What are 3 examples of fast adaptation?
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hair receptors
Pacinian corpuscles Meissner's corpuscles |
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What is a receptive field?
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Region of skin within which a tactile stimulus evokes a sensory response
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What are 2 features of sensation over the fingers?
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1. Finer two-point discrimination
2. Smaller receptive fields |