Chapter 13 Flashcards
PNS
outside Brain/Spinal cord
PNS: Include Sensory receptors
– Peripheral nerves
– Associated ganglia
– Motor endings
PNS
Provides links to/from the external environment
Classification of Sensory Receptor: Location
Exteroceptors – near or at body surface; touch, pain,
pressure, temperature receptors in skin
– Interoceptors – visceral receptors, monitor chemical, tissue, and temperature stimuli
– Proprioceptors – constantly “advise” the brain and cerebellum of movements
Sensory Receptor: Classified by stimulus:
Thermoreceptors, chemoreceptors, mechanoreceptors, nociceptors, photoreceptors
Classified by structural complexity:
Simple (unencapsulated or encapsulated)
– Complex – special senses
Sensory Receptors: monitor your world!
Structures specialized to respond to stimuli
* Activation of receptors = Depolarizations that trigger impulses to the CNS
* Sensory Integration: From Sensation to Perception
Sensation
(you become aware of-Thalamus) to
Perception
(Interpretation/understanding-Cortex)
Sensation to Perception:
Survival
Sensation
Perception
Sensation to Perception: Survival
Depends upon Sensation/Perception
Sensation to Perception: Sensation
awareness of changes in the internal and external environment
Sensation to Perception: Perception
conscious interpretation of those stimuli occurring in Cortex
3 main levels of neural integration in the somatosensory system are
Receptor level – Sensory receptors
– Circuit level – Ascending pathways (“wiring” pathway)
– Perceptual level – Neuronal circuits in the Cerebral cortex
Specificity
Receptor for that particular stimulus energy
Receptive field
must be stimulated (the smaller the field = more accurate localization)
converted
Stimulus energy converted into graded potential
Tonic Receptors
(Equilibrium): always on, alterations in frequency
Phasic Receptors:
normally “off” (Touch)/Report a change
Adaptation
occurs when sensory receptors are subjected to an unchanging stimulus
Adaptation
Receptor membranes become less responsive
– Receptor potentials decline in frequency/stop
– Pain receptors DO NOT adapt
– Slowly adapt/Not at all: Merkel’s discs, Ruffini’s
corpuscles, and Interoceptors that respond to chemical levels in the blood
Adapt Quickly: Pressure/Touch/Smell adapt quickly
Thalamus projects fibers to
–Somatosensory cortex
– Sensory association areas
Processing at the Perceptual Level
Brain interprets the activity of a specific receptor ALWAYS the same based on where it went (occipital lobe interprets visual signals)
* The result is an internal, conscious image of the
stimulus
Projection:
brain refers sensations to their usual point of stimulation
Main Aspects of Sensory Perception
- Perceptual detection – detecting that a stimulus has occurred
- Magnitude estimation – how intense a stimulus is (frequency of APs)
- Spatial discrimination –identifying the site or pattern of the stimulus
– 2 Point discriminations
test
– Varies depending on site
(Tongue- 5mm/Back -
50mm)
Feature abstraction
used to identify a substance that has specific texture or shape
Quality discrimination
the ability to identify submodalities of a sensation (e.g., sweet or sour tastes)
Pattern recognition
ability to recognize patterns in stimuli (e.g., melody, familiar face)
Regeneration of Nerve Fibers: Steps
1.The axon becomes fragmented at the injury site
2.Macrophages cleanse out the dead axon distal to the injury
3.Axon sprouts or grow through the regeneration tube
4.The axon regenerates and new myelin sheath
