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Histo > Sensory Receptors > Flashcards

Sensory Receptors Flashcards

1
Q

General Mechanism of Sensation

A

Sensory receptors transmit “information” in a series of action potentials

Differential sensitivities of sensory receptors allows for the CNS to “decode” the action potentials into “sensations”

Each receptor is highly sensitive to one type of stimulus (adequate stimulus)

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2
Q

Labeled Line principle

A

Each type of sensation is projected to a specific area of the CNS
Allows electrical impulses to be decoded into perceived sensation

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3
Q

Somatosensory Neuron

A

Cell body resides in the DRG
Peripheral and central processes
Peripheral process is specialized for specific stimuli

AP propagates from the periphery to the central process, then to a synapse with a CNS neuron (spinal cord, brainstem)

The frequency of APs is dependent on the stimulus intensity

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4
Q

Somatosensory Receptors

A

Specialized endings of primary afferent neurons

Send signals from periphery to CNS

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5
Q

Somatosensory Receptors occur where?

A

throughout the body

Skin, viscera, muscles, joints, connective tissue

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6
Q

Somatic sensation includes

A

Touch, pressure, vibration, body position, tickle, temperature, and pain (and itch)

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7
Q

Receptors transform energy into AP by stimulating

A

mechanical, chemical, and/or thermal energy into electrical energy (e.g., action potential)

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8
Q

Mechanoreceptors

A

detect mechanical deformation (compression or stretch)

Touch, pressure (sustained touch), stretch or vibration

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9
Q

Thermoreceptors

A

detect heat and cold

specific receptor for each thermal modality

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10
Q

Nociceptors

A

detect tissue damage (chemical or physical)

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11
Q

Chemoreceptors

A

detect chemical environment of body systems

ex. blood oxygen levels, bodily fluid concentrations

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12
Q

Electromagnetic receptors

A

retinal (light) receptors

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13
Q

Discriminative Touch

A

Discriminate between the quality of touch (soft or coarse) and which area is being touched (2pt discrimination)

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14
Q

Pressure and VIbration

A

Pressure is sustained touch

Vibration – rapidly alternating movements/pressure

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15
Q

Crude Touch

A

(light touch, non-discriminative touch)

Indicates whether or not area is being touched and the strength of the touch

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16
Q

Superficial receptors

A

Meissner’s corpuscles–light touch, vibration
Merkel’s disks-pressure
Hair follicle receptors-hair displacement

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17
Q

Subcutaneous Receptors

A

Pacinian corpuscle-light touch, pressure, vibration
Ruffini’s endings-stretch of skin
Free nerve endings-poorly localized touch, pressure, tickle, itch
Also act as nociceptors

18
Q

Meissner’s Corpuscles

A

Encapsulated, located in the ridges of superficial glaborous skin

Highly concentrated in the finger tips

Sensitive to:
Light touch, vibration and discriminative touch

Rapidly adapting

19
Q

Merkel’s Disks

A

Un-encapsulated; located in the superficial skin (hairy and glaborous)

Groups of 4-6 disks innervated by one fiber

Concentrated in the finger tips

Sensitive to discriminative touch

Slowly Adapting

20
Q

Pacinian Corpuscles

A

Encapsulated; located within:
Dermis, subcutaneous fat, intramuscular connective tissue, and capsules of synovial joints

Detects pressure, vibration, acceleration
Important function as joint motion receptors

Rapidly adapting

21
Q

Rufinni’s Endings

A

Encapsulated, flower-spray neural endings
Dermis, joints, glabrous and hairy skin

Detects light touch
Also warm (thermo) receptors

Slowly Adapting

22
Q

Hair Follicle: Hair end organ

A

Nerve endings embedded in hair follicle, surrounding hair shaft

Deflection of hair deforms follicle, creating a stimulus for the receptor

Light (crude) touch information

Consist of rapidly and slowly adapting types

23
Q

Thermoreceptors

A

Cold and warm receptors are most responsive to sudden changes in temperature:
Thermoreceptors are “sensitive” to the effect of temperature on their cell metabolism

Altered metabolism of the receptor serves as stimulus for it to fire action potentials

Pain receptors also are stimulated by extremes of heat/cold

24
Q

Thermoreceptors for cold

A

Krause’s bulb

slow adapting

25
Q

Thermoreceptors for heat

A

Ruffini’s endings

slow adapting

26
Q

Nociceptors

A

Stimulated by mechanical, thermal or chemical stimuli (if stimulus is related to tissue damage)

27
Q

Chemical substances that stimulate nociceptors

A

Bradykinin, serotonin, histamine, K+ and H+ ions (acids), acetylcholine, other inflammatory molecules

28
Q

What increases sensitivity to pain

A

Prostaglandins and substance P increase sensitivity to pain (sensitize free nerve endings)

Rate and extent of tissue damage is directly correlated with the level of pain perceived

29
Q

Hyperalgesia

A

increased sensitivity to painful stimuli

30
Q

Free Nerve Endings

A

No specialized receptor “ending”

Responsive to mechanical, chemical, and thermal stimuli

Respond to thermal changes, light touch and chemicals related to tissue damage

Slowly Adapting
Some do not adapt at all, continue firing as long as tissue insult remains

31
Q

Common cause of tissue damage

A

Bacterial infection, tissue ischemia, tissue contusion

32
Q

Fast Pain

A

Elicited by mechanical and thermal stimuli
Transmitted on A-delta fibers
Sharp, easily localized pain

33
Q

Slow Pain

A

Elicited by chemical stimuli and persistent thermal and mechanical stimuli
Transmitted by unmyelinated C-fibers; dull aching type pain

34
Q

Receptor potential

A

Stimulus causes a change in the membrane electrical potential of a sensory receptor

They causes a change in ion permeability of the receptor membrane and results in depolarization of receptor, If membrane depolarization reaches threshold, then APs are generated

35
Q

Freq of APs increase

A

as depolarizing current increases
Stronger stimulus results in increased AP frequency
Receptor continues to send action potentials as long as stimulus is present (continued depolarization)

36
Q

Receptor Adaptation

A

Diminishing rate of discharge of a somatosensory neuron occurs with continued stimulation of constant intensity (adaptation)

Adaptation allows the nervous system to focus on new or altered stimuli without the distraction of the constant stimulus

Adaptation takes place over a range of durations

Somatosensory receptors are either slowly-adapting or rapidly-adapting (some do not adapt at all)

37
Q

Adaptation Rate: Rapid

A

Rapidly adapting: (phasic receptors)
Receptor responds transiently at the onset of the stimulus and at the end of or a change in the stimulus

e.g.,Pacinian corpuscles – a type of mechanoreceptor

38
Q

Adaptation Rate: Slow

A

Slowly Adaptating: (tonic receptors)

Continued presence of stimulus is signaled by a persistent response from the receptor

39
Q

Slow adapting examples

A

Examples:
Nociceptors, Merkel’s receptors – a mechanoreceptor
Chemoreceptors of CV system (blood content measures)
Muscle spindles, Golgi tendon organ

40
Q

Influential factors for Adaptation Rate

A

Properties of excitability of the membrane of the sensory neuron

The non-neuronal accessory structure that surrounds the axon

41
Q

Referred Pain

A

Pain felt in part of the body that is remote from the tissue causing the pain
Most frequently occurs with pain (injury) in visceral organs (abdomen/thorax)

42
Q

Visceral Pain fibers and skin pain fibers

A

terminate at the same areas of spinal cord

Thus the CNS perceives the pain as coming from the skin rather than abdominal/thoracic organs

Histo (12 decks)

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