Introduction to Sensory Systems Flashcards
What is the function of sensory systems?
They allow us to
- Perceive the world around us
- Remain alert
- Control our movements + Behaviour
What do sensory receptors detect in a stimulus?
- Modality
- Location
- Duration
- Intensity
What are the types of receptors?
Mechanoreceptors
Chemoreceptors
Thermoreceptors
Photoreceptors (EM)
What happens to receptor information?
It is conveyed to the brain via discrete neuronal pathways which determine the intensity, spatial and temporal features of the stimuli
How is the complexity of a stimulus detected?
The complex quality of stimuli requires INTEGRATIVE ACTIVITY of the higher processing centres in the brain.
How is sensory information processed?
Sensory information is processed in sequential relay nuclei of the spinal cord, brainstem, thalamus and cerebral cortex. Each of these relay stations transform the information to provide a unique sensory experience.
What does the sensory system consist of?
Sensory receptors
Neural pathways
The brain.
What do sensory receptors detect?
Changes of the internal and external environment.
What are receptors?
Highly specialised endings of afferent neurons that convert stimuli energy into afferent energy signals that convey information about the stimuli to the brain.
Does a receptor detect all stimuli?
No each receptor is specialised to a certain type of stimulus, except that a receptor can be activated by a non-specific stimulus if its intensity is sufficiently high.
What happens to stimulus energy?
It is converted by the receptor into a GRADED RECEPTOR POTENTIAL and this process is called STIMULUS TRANSDUCTION
What is the magnitude of the receptor potential is determined by?
The magnitude of the receptor potential is determined by:
- Stimulus strength
- Summation of receptor potentials
- Receptor sensitivity
What can happen to a receptor with constant stimulation?
Adaptation.
This is when the sensitivity of a receptor is decreased due to prolonged stimulation.
What aspects of a stimulus are coded for?
- Modality
- Intensity
- Location
- Duration
How is modality determined?
Modality is determined by the type of stimulus and the receptor specialised to sensing that stimulus.
Each sensory pathway is specific to a modality
How is modality unique to an afferent neuron?
All receptors of a single afferent neuron are sensitive to the same stimuli (known as RECEPTOR SPECIFICITY) and therefore each afferent pathway is modality specific.
How does intensity influence receptor potential?
Increased stimulus = Large receptor potential, thus increased frequency of action potentials.
What is the effect of strong stimuli on receptor potential?
Stronger stimuli affect a larger area and recruit a larger number of receptors.
What is the lowest level of intensity detection called?
SENSORY THRESHOLD
How is stimulus location coded?
Stimulus location is coded by the site of the stimulated receptor (RECEPTIVE FIELD)
The precision of the location of stimuli encoded by a receptor is called?
ACUITY
What negatively correlates with acuity?
Acuity is negatively correlated with:
- The amount of convergence in ascending pathways
- Size of the receptive field
- Overlap of receptive field with adjacent fields
Where is receptor response highest?
Receptor response is highest in the centre of the receptive field since the receptor density is highest there.
With regards to duration, what do receptors detect?
The onset and offset of stimuli
What are the two types of receptors that act differently with the onset of a stimulus?
Rapid adapting receptors
Slow adapting receptors
How do rapid adapting receptors respond to a stimulus?
They respond rapidly at the onset of a stimulus but slow down or stop firing during the remainder of the stimulus (fast adaptation)
How do slow adapting receptors respond to a stimulus?
They maintain their response at or near the initial level of firing through the duration of the stimulus and are important in signalling slow changes.
What comprises a sensory unit?
A single afferent neutron with associated receptor endings make a SENSORY UNIT
The property of all receptors to detect a stimuli is called?
Receptive field and all receptors have one. - The space in which the receptor transduces stimuli.
Where do afferent neurons connect to?
They enter the CNS and diverge, synapsing upon many interneurons.
What is the name given to the afferent neuron and its CNS connections?
Ascending or sensory pathways.
Are ascending pathways unique?
Yes they each code for a singe type of stimulus (modality)
What is unique about the location of innervation of ascending pathways in the brain?
The innervation is in the contralateral hemisphere of the receptors location in the body.
Specifically the region of brain responsible for processing that information i.e. olfactory cortex etc.
In the brain what processes ascending tract information?
Primary cortical sensory areas. Cortical association areas participate in more complex analysis of incoming information such as computing, memory, language, motivation, emotions etc.
Can different sensory modalities be processed together?
This phenomenon is called MULTISENSORY INTEGRATION and improves the processing of sensory information for better localisation accuracy and reaction time. i.e visual and auditory somatosensory cues.
Is our perception of a stimulus true to its physical properties?
No, Our perceptions differ qualitatively from the physical properties of the stimuli because the nervous system extracts only certain pieces of information from each stimulus while ignoring others.
How are sensory networks organised?
They are organised in a hierarchal manner.
What does a hierarchal manner mean?
Listen to the lecture if available or ask….
What is a an example of impaired sensory function?
Sensory Processing Disorder
What is sensory processing disorder?
Misinterpret everyday sensory information, such as touch, sound, and movement
Who is mainly affected by SPD?
Children
What are the types of SPD?
- Sensory-avoiding children
- Sensory-seeking children
- Motor skills problems
What are the consequences of SPD?
They often suffer from impaired self-esteem, anxiety, depression, or aggression, that affect social engagement.
