Sensory Physiology Flashcards
What makes up the Sensory System?
3
Sensory receptor +
neural pathway to brain/spinal cord +
area of the brain that process this information
What is Sensation?
sensory information brought to our conscious awareness
What is Perception?
understanding of sensation
What is Sensory Processing?
What does it lead to?
- Transduction of stimulus energy (i.e., pressure, sound, light, smell, temperature, etc.) into graded potentials and then action potentials
- Processing in the CNS may lead to efferent reflexes, perception, storage, comparison to memories and assignment of emotional significance to the sensory information
What are Sensory Receptors?
(2 classes)
Specialized endings of primary afferent neurons
Receptor Cell: (release NT’s)
What are the Classes of Sensory Receptors?
5
Mechanoreceptor: mechanical stimuli (pressure and stretch)
Thermoreceptor: changes in temperature
Photoreceptors: light wavelengths
Chemoreceptors: binding of chemicals to receptor membrane
Nociceptors: threatening/painful stimuli
Classes of Sensory Receptors
What are Exteroreceptors?
monitor the external environment
Classes of Sensory Receptors
What are Interoreceptors?
monitor visceral organs
Classes of Sensory Receptors
What are Proprioreceptors?
monitor position of skeletal muscles and joints
(posture)
What are General Senses?
4
- Pain
- Temperature
- Touch
- Proprioception
What are Special Senses?
5
- Smell
- Sight
- Hearing
- Taste
- Balance
Tend to be more complex, and found in specific sense organs
What is the The Receptor Potential?
What is Sensory Transduction?
- graded potential that can initiate an action potential
- Sensory transduction: process by which a sensory stimulus is transformed into an electrical response (graded or action potential)
How does Transduction of the stimulus into a receptor (graded) potential of an afferent neuron work?
Where does the AP Initiate?
- The stimulus causes ion channels to open -> change in the receptor potential due to influx of positive ions
- If threshold potential is achieved, an action potential will be initiated
- The first node of Ranvier is usually the site of action potential initiation, due to the presence of voltage-gated ion channels
What does a greater frequency of action potential lead to?
If threshold potential is reached
greater frequency of action potential leads to greater frequency of neurtransmitter release
Graded potentials – can increase in size in response to the size of the stimulus
Action potentials increase in frequency in response to the size of the stimulus
What is an Adaptation?
- A reduction in receptor sensitivity which leads to reduced action potential firing frequency (despite continuous signaling)
- Receptors can be slow or fast adapting
What are Slow Adapting Receptors (Tonic)?
- Persistent/slow decaying receptor potential
- Found where sensory information is needed to be constantly monitored (i.e., muscles that control posture)
What are Rapid Adapting Receptors (Phasic)?
- Quickly cease responding in response to continued stimuli
- Monitor sensory information that persists but does not need to be monitored closely (i.e., the pressure of a chair when you first sit down)
What is Primary Sensory Coding?
Conversion of stimulus energy into a signal that can be interpreted by the CNS.
Primary Sensory Coding
What is a Sensory unit?
single afferent neuron with all its receptor endings… sound familiar?
Primary Sensory Coding
What is a Receptive Field?
area of the body that, when stimulated, leads to activity in an afferent neuron. Receptive fields of neighboring afferent neurons usually overlap, allowing one area to stimulate several sensory units.
How is Primary Sensory Coding Achieved?
3
Achieved by:
1. Stimulus type (modality)
2. Stimulus strength
3. Stimulus location
How is Primary Sensory Coding Achieved?
What are Stimulus Types/Modalities?
3
- A given receptor is particularly sensitive to one modality – the adequate stimulus
- All receptors of a single afferent neuron are preferentially sensitive to the same modality
- Adjacent neurons do not always have the same adequate stimulus
Same Adequate Stimulus: Inside
Different Adequate Stimulus: Outside
How is Primary Sensory Coding Achieved?
What is Stimulus Intensity?
- As adjacent receptors of the same neuron are activated (due to an increase in pressure), their local signals are summated, resulting in greater action potential firing frequency.
- Perceived stimulus intensity can also increase if additional afferent neurons are recruited.
How is Primary Sensory Coding Achieved?
What are Stimulus Location?
- APs travel along unique pathways to a specific region of the CNS associated with only that modality and body location
Acuity in which we can discriminate stimulus location depends on what?
3
- Convergence of neuronal input
- Size of receptive field covered by a single sensory unit
- Density of sensory units
