Sensory Perception Flashcards
Steps to Sensation
- Stimulation
- Transduction
- Conduction
- Perception
Stimulation
Application of stimulus
Sensors most sensitive to one particular
stimulus modality (adequate stimulus)
Transduction
– Induction of an action potential
– If strong enough depolarization, AP results
– ↑ stimulus strength above threshold → ↑ AP firing rate
Conduction
– Relay of information through a sensory pathway to specific region of CNS 1st order neuron
– from stimulation point to CNS 2nd order neuron
– e.g., from entry into CNS to thalamus 3rd order neuron
– e.g., from thalamus to perception site
Perception
– Detection of environmental change by CNS
Receptor Properties
Adequate Stimulus-Sensors most sensitive to one particular stimulus modality
Sensory Adaptation
Phasic receptors
Tonic receptors
Acuity
Sensory Adaptation
Response of sensors to constant stimulation
Phasic Receptors
exhibit sensory adaptationfiring rate of receptor (# AP’s)
Decreases with constant stimulus
Tonic Receptors
Exhibit little adaptation
Maintain constant firing rate as long as stimulus is applied
Sensory System
Touch (Mechanoreceptors)
Temperature (Thermoreceptors)
Pain (Nociceptors)
Body position (Proprioceptors)
Photoreceptors
Osmoreceptors
Chemoreceptors
Touch (Mechanoreceptors)
stretch, tension and indentation
Temperature (Thermoreceptors)
changes in temperature
Pain (Nociceptors)
damaging stimuli – extreme temperature, sudden or severe overdistension, chemicals
Body position (Proprioceptors)
changes in joint and muscle tension and signal body position
Receptors of the skin
Slow adapting or Fast adapting
1. Free nerve ending
2. Merkel’s disk
3. Meissner’s corpuscle
4. Pacinian corpuscle
5. Ruffin’s ending
Slow adapting
Receptor is slow to give a response to a stimuli, and when a stimulus is removed, the response falls slowly
Fast Adapting
Receptor will respond quickly, but will not give a sustained response
Free nerve endings
Variable adapting (slow or fast)
Heat, cold, pain
Merkel’s disk
Slow adapting
Expanded dendritic endings
Meissner’s corpuscle
Fast adapting
Encapsulated endings
Tactile sensory input=light pressure, slow vibration (50 Hz)
Pacinian Corpuscle
Fast adapting
Encapsulated endings
Tactile sensory input=heavy pressure, rapid vibration (300Hz)
Ruffin’s ending
slow adapting
Expanded dendritic endings
Tactile Sensory input
Respond to pressure and movement of skin
Specialized receptors that respond to particular types of inputs
Use mechanically gated ion channels ( pacinian and messiner)
Acuity
- ability to discriminate size, shape of an object in the environment
Determined by size of receptive field
– area of the body that, if stimulated, will cause a response from a sensory neuron - ↑ receptor density, ↓ receptive field size,↑ acuity
– easier to define borders of an object
Receptive Field
The region of the skin in which a stimulus evokes a response in a single sensory neuron
Discrimination depends on the density of receptors
- Fingers 1-4 mm
- Thigh 45 mm
Thermoreception
Respond to non painful temperatures.
warm thermoreceptors
Cold thermoreceptors
Thermosensitive neurons are present in the skin, the hypothalamus and the spinal cord.
Thermoreceptors – respond to non painful temperatures. Extreme temp is detected by nociceptors
