- local responses that occur at a sensory receptor and in regions of the membrane that ghave only ligand gated channels - graded in amplitude and duration - proportional to the amplitude and duration of the stimulus

- same stimulus - repeated close together in time (high frequency)

Exam Two - Somatosensory Physiology Receptors Flashcards by Catherine McDowell

What are sensations?

virtual reality, how the nervous system transduces energy into perception

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What is feature extraction?

what our sensory receptors do, these receptors extract different features of a given stimulus and send it to CNS

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What is a general problem for all sensory systems?

representing multidimensional stimula with a single language - frequency of action potentials

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best stimulus for a specific receptor?

adequate stimulus
- sensory receptors are activated by a specific stimuli

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transduction

conversion of specific aspects of stimulus energy into membrane conductance change, that leads to a graded potential

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generator potentials can lead to an…

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GP are membrane potential changes, that…

may be summated
degraded over time and distance
are not sustained

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What are two types of GP?

1 - receptor potentials
2 - synaptic potentials

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Receptor potentials

local responses that occur at a sensory receptor and in regions of the membrane that ghave only ligand gated channels
graded in amplitude and duration
proportional to the amplitude and duration of the stimulus

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Where do synaptic potentials occur?

postsynaptic membrane of dendrites, soma, or axon terminals.
similar to receptor potentials

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________ must reach a portion of the axon that contains voltage gated channels for generation an __________

receptor potentials, AP

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The portion of the AXON. that is in contact with RECEPTOR does not have “voltage gates” channels, therefore the change in membrane potential is __________ and __________ of the applied stimulus

directly proportional with the intensity, duration

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What are two types of graded potentials at the synapse?

EPSP, IPSP

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depolarizing membrane potential = ________, hyperpolarizing membrane potential = _____________.

EPSP, IPSP

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EPSP is…

local
depolarzing
graded
slow
electronic (passive spread and decremental)

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__________ have common features with EPSP, both are graded, local, dissipate if AP is not generated.

receptor potentials

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At the ___ or _________, generator potentials may be summated to the point where the threshold level for an AP is reached.

axon hillock, adjacent to sensory receptor (“trigger zone”)

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Where is threshold voltage?

-55

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what are the two types of graded potential summation?

temporal and spatial summation

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temporal summation

same stimulus
repeated close together in time (high frequency)

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spatial summation

location of synaptic input

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What are the 4 basic dimensions of a stimulus/sensation

1 - modality
2 - intensity
3 - location
4 - timing

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modality

what the sensation type is
ex - vision, taste, smell, touch, etc…

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submodality

quality of stimulus
- color vision
- touch vibration

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intensity

how much of sensation

What is intensity coded by?

frequency code

What is intensity limited by?

absolute refractory period

neural mass

number of axons activated

location

where the sensation originated

receptive field

portion of the sensory space that can evoke neuronal responses upon stimulation

precise location

overlap of RFs increases ability to discriminate location

_______ increase likelihood of discrimination

small RFs

___________ improves discrimination

overlap of RFs

Size of RF varies with location, distal to proximal (increase/decrease)?

increase

size of RF varies with the density of innervation, distal to proximal (increase/decrease)?

decrease

Size of RF varies with stimulus intensity until_________

maximum size is reached

timing

when the stimulus starts and stops

adaptation rate

how long receptors continue to generate AP when the probe is in the RF and motionless

RA stands for?

rapidly adapting receptors

RA receptors

respond to dynamic aspects of the stimulus (movement: velocity and acceleration)

SA stands for?

slowly adapting receptors

SA receptors

respond to static (and dynamic) aspects of the stimulus, respond if the stimulus is there even if its not moving

temporal pattern of coding

receptors respond to the stimulus onset, duration, offset

Absolute threshold

feel it or not - signmoid curve - 50% of the time patients say they feel stimulation

why is using AT problematic?

AT changes with emotion state, mood, and distractions

differential threshold (JND)

minimus difference in stimululation that a person can detect 50% of the time

T or F? Differentiating is linear

False! It's not! It is better at lower intensity, as we go higher, the difference must be much bigger for perception of the difference

3 factors for differential threshold: point localization

1 - varies with location 2 - best on face and hands 3 - related to RF size

Two point threshold is related to....

1 - RF size 2 - innervation density 3 - RF overlap

How are somatosensory receptors classified? and what are the classifications?

classified by what part of the world they perceive - exteroceptive - proprioceptive - interoceptive

cutaneous and subcutaneous mechanoreceptors

pacinian corpuscle meissners corpuscle ruffini ending merkel cell

pacinian corp chart

ra, AB, contact vibration

meissners corp chart

RA AB contact flutter

ruffini ending chart

SA AB pressure, skin stretch

merkel cell chart

SA AB pressure, texture

muscle, deep mechanoreceptors

muscle spindle golgi tendon organ joint capsule-mechanoreceptor stretch-sensitive free endings

muscle spindle chart

SA Aa muscle length and change in length

golgi tendon organ chart

SA Aa muscle tension, change in tension

joint capsule mechanoreceptors chart

SA AB joint angle and rate of change

stretch-sensitive free endings chart

SA A delta excess stretch or force

thermoreceptors and nociceptors

cool receptors warm receptors mechanical nociceptor thermal nociceptor (2 types) polymodal nociceptor

cool receptors

SA Adelta skin cooling

warm receptors

SA C skin warming

mechanical nociceptor

SA Adelta sharp pain (fast pain)

thermal nociceptor (2types)

RA Adelta burning pain RA C freezing pain

polymodal nociceptor

RA C aching, burning pain (slow pain)

What are the receptors in glabrous (hairless) skin?

meissners corpuscle merkels disks pacinian corpuscle

what are the receptors in hairy skin?

hair-follicle receptor tactile disk ruffini ending

What stimulus does the pacinian corpuscle respond to?

vibration detector responds to acceleration/deceleration points in skin indentation

why is the RF of pacinian corpuscle large?

because vibration travels easily through body tissues

what is the adaptation rate of pacinian corpuscle?

RA rapidly adapting

What is the receptive field size of pacinian corpuscle?

large

What type of fibers are pacinian corpuscles?

what stimulus does meissner corpuscle respond to?

velocity change (ramps of skin movement) can respond to slow vibrations called "flutter"

What type of fibers are meissners corpuscle?

What is the adaptation rate of meissners corpuscle?

What is the receptive field size of meissner corpsucle?

small!!

2 facts about meissner corpuscle you need to remember?

- may contribute to high spatial resolution of fingertips, lips, etc. - capsule consists of flattened epithelial cells

Ruffini ending respond to what kind of stimulus?

responds to velocity ramp (dynamic phase) and the plateau (static phase) of skin indentation encodes intensity (pressure) really well

describe the AP distribution of ruffini endings

AP during plateau are evenly spaced but frequency of AP increases with intensity

What is the receptive field size of ruffini endings?

large! large, stretch sensitive receptive field

What is the adaptation rate of ruffini endings?

What type of fibers are ruffini endings?

AB fiber

What is special about merkel cells?

an epithelial cell that has a synapse with the neuron obviously the receptor cannot produce APs

describe the AP distribution of merkel cells?

characteristic irregular discharge pattern during plateau phase

What is the receptive field size of merkel cells?

very small, punctate receptive field

What type of stimulus do merkel cells read?

a good intensity response, known as a "pressure receptor"

What is the adaptation rate of merkel cells

What type of fibers are merkel cells?

AB fibers

______ receptors respond to a given simulus

All!! Each receptor extracts a different type of information from the stimulus

Describe the pathway from the skin receptor to the brain

receptors read stimulus, send it up the the nucleus cuneatus, then to VPL nuclei of the thalamus, and from there to the somatosensory cortex