Sensor Flashcards
What is a receptor cell?
specific sensitive cell that receives the stimulus and converts it into receptor potential (electric potential).
Receptor cells of sensory organs are sensitive specifically for ___
one type of physical or chemical stimulus
Receptor cells of sensory organs are sensitive specifically for one type of physical or chemical stimulus (e.g., light, sound, etc.).
→ This stimulus causes a change in the ___, resulting in the generation of the __
- resting potential
- receptor potential.
What is receptor potential?
local (non-propagating) change of membrane potential of the receptor cell.
→ Its amplitude depends on the stimulus intensity.
What is dynamic compression?
In the case of weak stimuli, the relative change of the receptor potential is greater than in case of strong stimuli.
→ Sensitivity of the receptor cell depends on the strength of the stimulus (this usually follows a power function).
Sensitivity of the receptor cell depends on the __
strength of the stimulus (this usually follows a power function).
What is ACTION POTENTIAL (AP)?
a short electric voltage pulse (~ ms) of constant amplitude (~ 0.1V) which propagates rapidly along the neural axon.
→ Its main variables are the activation threshold and the repetition frequency.
What is sensory nerve?
nerve bundle that converts the receptor potential exceeding a threshold level into action potential (AP), and transfers the frequency-coded information (series of AP) from the receptor cell to the CNS.
The sensory nerve cell, which is connected to the receptor cell, converts the ___ into the train of uniform electric pulses called action potentials
receptor potential (above a threshold)
In most cases, what is the relationship between The frequency of the action potential and the receptor potential amplitude?
The frequency of the action potential is proportional to the receptor potential amplitude in most cases.
Why can the coded information arrive unchanged and undamped to the respective sensory center of the brain?
Because the amplitude of the action potential does not change during its propagation along the nerve
Because the amplitude of the action potential does not change during its propagation along the nerve, the coded information arrives unchanged and undamped to the respective ___
sensory center of the brain,
What is sensory center of the brain?
where sensation is generated as a result of complex processes.
→ The strength of sensation corresponds to the frequency of the action potential.
For reading only
The lower part of Fig. 1 represents the block diagram of one possible electronic model of the sensory system, which we will use during the measurement.
What are receptor cells of the retina?
rods and cones.
The model of the photoreceptor shown here corresponds to the ___
cones that are responsible for daylight vision.
THE LIGHT SENSOR MODEL
The instrument in our measurement is a model of the (1)____, thus the physical signal energy is represented by (2)___ (Fig. 1, lower part).
→ The electronic amplifier subsequent to the photoreceptor (transducer) amplifies and compresses the electronic signal corresponding to the light stimulus.
- retina
- light
THE LIGHT SENSOR MODEL
The instrument in our measurement is a model of the retina, thus the physical signal energy is represented by light (Fig. 1, lower part)
→ The electronic amplifier subsequent to the ___ (transducer) amplifies and compresses the electronic signal corresponding to the light stimulus.
photoreceptor
THE LIGHT SENSOR MODEL
The instrument in our measurement is a model of the retina, thus the physical signal energy is represented by light (Fig. 1, lower part)
→ What is the role of The electronic amplifier subsequent to the photoreceptor (transducer)?
It amplifies and compresses the electronic signal corresponding to the light stimulus.
THE LIGHT SENSOR MODEL
The instrument in our measurement is a model of the retina, thus the physical signal energy is represented by light (Fig. 1, lower part).
→ The electronic amplifier subsequent to the photoreceptor (transducer) amplifies and compresses the electronic signal corresponding to the light stimulus.
→ Here we can measure the signal corresponding to the ___
receptor potential.
THE LIGHT SENSOR MODEL
The instrument in our measurement is a model of the retina, thus the physical signal energy is represented by light (Fig. 1, lower part).
→ The electronic amplifier subsequent to the photoreceptor (transducer) amplifies and compresses the electronic signal corresponding to the light stimulus.
→ Here we can measure the ___ corresponding to the receptor potential.
signal
THE LIGHT SENSOR MODEL
The instrument in our measurement is a model of the retina, thus the physical signal energy is represented by light (Fig. 1, lower part).
→ The electronic amplifier subsequent to the photoreceptor (transducer) amplifies and compresses the electronic signal corresponding to the light stimulus.
→ Here we can measure the signal corresponding to the receptor potential.
→ The subsequent voltage-to- frequency converter generates the ___, which can be displayed on an oscilloscope.
pulse train similar to the action potential
HOW THE SENSOR MODEL WORKS
Structure of the light sensor of the model equipment
The light sensor of the model equipment is a silicon photodiode located behind the input aperture (center of the iris) inside the box
HOW THE SENSOR MODEL WORKS
In the first phase of signal processing, the electric signal of the photodiode is (1)___ and (2)____ by a special amplifier
→ Direct current of the (3)___ can be measured at this stage.
- amplified
- compressed
- RECEPTOR POTENTIAL
HOW THE SENSOR MODEL WORKS
In the second part of the signal processing, the receptor potential is converted into a train of (1)___ by a so-called (2)___.
The pulse frequency is proportional to the (3)___ at any time.
- square pulses
- voltage-to- frequency converter
- receptor potential
HOW THE SENSOR MODEL WORKS
In the first phase of signal processing
→ 2nd phase of signal processing
→ Finally, a shape-forming circuit generates a signal similar to the real ___, that can be visualized on the screen of the oscilloscope.
ACTION POTENTIAL
HOW THE SENSOR MODEL WORKS
In the first phase of signal processing
→ 2nd phase of signal processing
→ Finally, a shape-forming circuit generates a signal similar to the real ACTION POTENTIAL, that can be visualized on the screen of the oscilloscope.
oscilloscope
What is WEBER-FECHNER’S LAW?
logarithmic relationship between sensation and relative stimulus which became obsolete with the more accurate Stevens’ power law.
What is STEVENS’ POWER LAW?
relationship between sensation ( ) and relative stimulus ( /0) in a form of power function as = const ( /0) n, where the exponent n is characteristic for the modality of sensation. For example, for loudness n = 0.3, and for light sensation n = 0.5.
PLAN OF THE MEASUREMENT
make a note of the measured value of illuminance
→ Remove the luxmeter and place the sensor model box under the glass fiber bundle so that the center of the aperture falls exactly in the same position where the luxmeter aperture was before.
→ Read and make note of the___ from the voltmeter in Volt units.
→ Measure the time period in ms (millisecond) units between the action potentials on the oscilloscope screen
receptor potential (voltage)
PLAN OF THE MEASUREMENT
make a note of the measured value of illuminance
→ Remove the luxmeter and place the sensor model box under the glass fiber bundle so that the center of the aperture falls exactly in the same position where the luxmeter aperture was before.
→ Read and make note of the___ from the voltmeter in Volt units.
→ Measure the (1)____between the (2)___ on the oscilloscope screen
- time period in ms (millisecond) units
- action potentials
As the action-potential frequency is proportional to the strength of light sensation, which law is valid? Describe it
The psychophysical law, called Stevens’ power law
Principle of LOUDNESS MEASUREMENT
We will measure the relationship between the objective sound intensity and the subjective psychophysical loudness.
In the loudness versus sound intensity graph (Fig. 7 bottom panel) the theoretical Stevens’ power law of loudness scaled in ___ units,
Sone
In ___ graph (Fig. 7 bottom panel) the theoretical Stevens’ power law of loudness scaled in Sone units,
the loudness versus sound intensity
the Weber-Fechner type of loudness level
→ Scaled in ___ unit
Phon
In the loudness versus sound intensity graph (Fig. 7 bottom panel) the theoretical ___ scaled in Phone units,
the Weber-Fechner type of loudness level
Classification of receptors cell according to stimulus
- Photoreceptor
- Chemoreceptor
- Thermoreceptor
- Mechanoreceptor
- Baroreceptor
Classification of receptors cell according to location
- Interoreceptor
- Exteroreceptor
- Proprioreceptor
Classification of receptors cell according to complexity
What are 5 modalities?
Vision, hearing, touch, taste, smell
What is Information coding by the receptor potential?
Amplitude coding, where the intensity of the stimulus corresponds to the receptor potential.
When the stimulus exceeds a given threshold, an action potential will be generated.
What is Information coding by the action potential?
Frequency coding, where the increase in the voltage of the receptor potential will lead to higher frequency of the AP of nerve.
gives information about:
- modality (type) (depends of which nerve does the AP)
- intensity (strength) frequency coding
- duration
- localization
What is adaptation?
A negative feedback in which almost all sensory organs respond by a decreasing sensation to constant stimuli
What is Absolute threshold stimulus
It is determined by using idealized circumstances of sensation
What is relative threshold stimulus?
It is distinguished in the presence of background noise of a given intensity.
→ The difference between a background intensity and a different intensity that can barely be distinguished from it → relative threshold stimulus
Describe compressive sensing?
- According to Steven’s Power law, sensation is a power function of the stimulus strength
- The exponent ‘n’ is a constant specific type of sensation and Oo is the absolute threshold stimulus
→ If n < 1, the function is called compressive
Describe expansive sensing
- According to Steven’s Power law, sensation is a power function of the stimulus strength
- The exponent ‘n’ is a constant specific type of sensation and Oo is the absolute threshold stimulus
→ If n > 1, the function is called expansive
