Chapter 7 Sensory Physiology Flashcards
specialized cells that generate graded potentials called receptor potentials in response to a stimulus
Can be a specialized endings of the primary afferent neurons or
Separate receptor cells that signal the primary afferent neurons using neurotransmitters
Sensory Receptors
five major divisions of these sensory receptors based on stimuli that they respond to:
- Mechanoreceptors
- Thermoreceptors
- Photoreceptors
- Chemoreceptors
- Nociceptors
the process of converting sensory information into electrochemical signals that are sent to the brain.
Primary Sensory Coding
is the conversion of a stimulus into a signal that is conveyed to the central nervous system.
Coding
is conveyed by both the frequency and the amplitude of the resulting signals.
Information
A decrease in receptor sensitivity, results in a decrease in action potential frequency in an afferent neuron despite a stimulus of constant strength
Adaptation
- Increased by increasing frequency of action potentials in a single afferent neuron
- As the strength of a local stimulus increases, receptors on adjacent branches of an afferent neuron are activated
Stimulus Intensity
- Coded by the site of a stimulated receptor
- Action potentials from each receptor travel along unique pathways to a specific region of the CNS
Stimulus Location
one stimulus location can be discerned from an adjacent one depends upon the amount of convergence of neuronal input in the specific ascending pathway
Acuity
how does Overlapping Receptive Fields happen
- When receptor endings of different afferent neurons overlap, a stimulus will trigger activity in more than one sensory unit
A high action potential frequency in one neuron but low in the others provide more accurate localization of the stimulus
- enables the localization of a stimulus site
- information from afferent neurons whose receptors are at the edge of a stimulus is strongly inhibited
- enhances the contrast between stimulated region
Lateral Inhibition
- Exact localization with __________ is possible because it removes the information from the peripheral regions
Lateral Inhibition
____________ are subject to extensive modification before they reach higher levels of the CNS.
Sensory signals
Modification can come from
- inhibition from collaterals from other ascending neurons (lateral inhibition)
- pathways descending from the brain
- by synapses on the axon terminals of the afferent neurons (example of presynaptic inhibition)
- indirectly via interneurons that affect other neurons in the sensory pathways.
a chain of three or more neurons that form an ascending pathway to the CNS
Neural Pathways in Sensory Systems
what are the chain of three or more neurons that form an ascending pathway to the CNS
- First order neuron
- Second order neuron
- Third order neuron
what happens when afferent neurons enter the CNS and synapse with the interneurons
- The process may diverge to terminate on several interneurons
or - Many afferent neurons terminate upon a single interneuron
Processing of afferent information happens in:
- primary cortical receiving areas
- association areas in the cerebral cortex where complex integration occurs
- relies upon various association areas of the cortex to properly process sensory information
Primary somatosensory cortex
perceptual processing involves arousal, attention, learning, memory, language, and emotions
true
Perception of sensory information is dependent upon numerous factors
true
- Sensation from the skin, muscles, bones, tendons and joints, or somatic sensation
- initiated by a variety of sensory receptors
Somatic Sensation
Factors that Affect Perception
- Receptor adaptation and afferent processing
- Emotions and experiences
- Not all stimuli give rise to a conscious sensation
- Ex: stretch receptors monitor blood pressure - Lack of receptors for certain stimuli
- Ex: radio waves - Damaged neural pathways
- Drugs
general principles of sensory
stimulus organization
- Specific sensory receptor types are sensitive to certain modalities and submodalities.
- A specific sensory pathway codes for a particular modality or submodality.
- The specific ascending pathways are crossed so that sensory information is generally processed by the side of the brain opposite the stimulated side of the body.
- In addition to other synaptic relay points, most specific ascending pathways synapse in the thalamus on their way to the cortex.
- Information is organized such that initial cortical processing of the various modalities occurs in different parts of the brain.
- Specific ascending pathways are subject to descending controls.
Somatic Sensation receptors respond to:
- Touch and pressure
- Sense of posture and movement
- Temperature
- Pain
slowly adapting mechanoreceptor, touch and pressure
Merkle’s corpuscle
-rapidly adapting mechanoreceptor, touch and pressure
Meissner’s corpuscle
slowly adapting, some are nociceptors, some are thermoreceptors, and some are mechanoreceptors
Free nerve ending
slowly adapting mechanoreceptor, skin stretch
Ruffini corpuscle
apidly adapting mechanoreceptor, vibration and deep pressure
Pacinian corpuscles-
Differs from the other somatosensory modalities
* After transduction of the first noxious stimuli into action potentials, changes occur in the pain pathway that alter response to subsequent stimuli.
* can be altered by past experiences, suggestion, emotions, and the simultaneous activation of other sensory modalities
Pain
an increased sensitivity to painful stimuli
Hyperalgesia
is the selective suppression of pain without effects on consciousness or other sensations.
Analgesia
Some mechanisms to achieve pain relief:
Electrical stimulation of the CNS
- Drugs: NSAIDs and Morphine (opioids)
- neurons in the inhibitory pathways that release morphine-like endogenous opioids
- Acupuncture
- Transcutaneous Electrical Stimulation (TEMS)
- Massage
The brain is “confused” and you feel pain from an internal organ as another area of the body.
Referred Pain
Distinguish between a sensation and a perception
A sensation is the raw, immediate sensory input received by the body from the environment through the senses, like feeling the warmth of a cup or seeing a bright light, while a perception is the brain’s interpretation and organization of that sensory information, which gives meaning to the sensation, like recognizing the warmth as a hot cup of coffee or identifying the bright light as a car headlight.
How does the nervous system distinguish between stimuli of different types?
The nervous system distinguishes between different types of stimuli by using specialized sensory receptors that are designed to detect specific stimuli, sending signals along dedicated neural pathways to specific regions of the brain, essentially acting like “labeled lines” where the identity of the stimulus is preserved throughout the transmission process; this means different types of stimuli activate different sets of neurons, allowing the brain to interpret the information accordingly.
