Ch. 3 Flashcards
Transductino
Environmental Energy > Electrical Impulses (Sensory receptors)
General properties of sensory receptors and afferent pathways
adequate stimulation
intensity coding
sensory adaption
Adequate stimulation
sensory receptors inform the CNS that a particular event has occurred in the environment
sensory receptors respond to specific stimuli
Receptors are activated when an event raised the receptors resting level high enough to generate sensory impulses
Intensity Coding
Allows identifying the intensity of a particular sensory event
The intensity of a stimulus can be conveyed by two mechanisms
-Spatial summation: Increase stimulus = increase number of different sensory receptors that fire
-Temoral Summation: increase stimulus = increase frequency receptors fire
Spatial Summation
Intensity Coding
increase number of different sensory receptors that fire
Temporal Summation
Intensity Coding
increase stimulus = increase frequency receptors fire
Sensory Adaption
Allows blocking out a irrelevant sensory information
-shortly after a sensory receptor registers a stimulus, the firing rate is reduced
Different sensory receptors adapt at different rates
-touch/pressure receptors (fast) v. pain receptors (slow)
Different adaption rates of receptors determines the nature of the information
Transmission and Integration
Afferent pathways
First stage of integration occurs at the thalamus
-sensory relay center
-gating out irrelevant information
-emotional response (via the limbic system)
Kinesthesis
Conscious awareness
Dorsal Column System
fine touch, touch, skin vibration, and limb position
fast transmission
Spinothalamic
pain, temperature
slow transmission
Transmission and Integration- Info goes to?
Information goes to the cortex
Results in conscious awareness of sensations
Final perception and interpretation
Memory assisted
“Subconscious” Awareness
Spinocerebellar tract
Information goes to cerebellum
leads to a subconscious perception of limb position
Somatosensation
bodily sensation of touch, pain, temperature, and limb position
Primary receptors (mechanoreceptors) Cutaneous receptors Proprioceptors -Muscle spindles -GTO -Joint receptors
Cutaneous Receptors
In your skin Disproportionate distribution -Lips and fingers v. legs and trunk -Greater densities in areas of the body required to perform fine movements ex. hands, face (lips)
Four types of Cutaneous Receptors
Sensory Nerve Fibers
Meissner’s Corpuscles
Merkel’s Disks
Pacinian Corpuscles
Sensory Nerve Fibers
Cutaneous Receptors
Epithelial tissue/touch & pressure
Meissner’s Corpuscles
Cutaneous Receptors
Connective tissue sheaths & hairless portions of skin/light touch
Merkel’s Disks
Cutaneous Receptors
Near Meissner’s corpuscles/constant contact
Pacinian Corpuscles
Cutaneous Receptors
Deep tissue, tendons, ligaments/deep pressure
Cutaneous Cues
Direct the leaner’s attention to the appropriate cutaneous information
“feel your wight on your back foot”
“lightly squeeze the trigger”
Proprioceptors
Mechanoreceptors in muscles, tendons, ligaments, joints and the vestibular apparatus (inner ear)
Includes: muscles spindles(most important for kinesthesis), golgi tendon organs, joint receptors
Muscle Spindles
The most important source of kinesthesis
Serve both sensory (awareness) and motor function (control of fine movements)
Higher number of spindles are located involved in fine movements (hands, etc) *does not lead to higher acuity
Extrafusal
produce muscular contraction
alpha motor neurons
no sensory afferent pathway
Intrafusal
muscle fiber comprising the spindle
gamma motor neurons
primary (la) sensory neuron (length and velocity)
secondary (ll) sensory neuron (length)
Neuronal control of spindle
Alpha - to extrafusal
Gamma - to intrafusal
Afferent - sensory neurons moving away from the spindle
– la (length and velocity) and ll (length)
Muscle Spindles (2)
Gather information about muscle length
- signal absolute muscle length
- signal the rate of change in muscle length
Contribute to the regulation of muscle length
Golgi Tendon Organs
Located at myotendinous junctions Detect muscle tension -Rate and absolute amount -Activated with active contraction or passive lengthening -Theshold: 1 gram
Golgi Tendon Organs (2)
Tend to be inhibitory in nature
- produce muscle relaxation
- protective mechanism
Joint Receptors
Located in joint capsules and ligaments
Provide info about: static position of a joint in space, endpoint positions of joints during active movement
Small contributor to conscious awareness
Perception of Muscular Force or Effort
GTO’S: first source of muscular force or effort
Corollary discharge: copy of descending motor commands being sent to the higher-order sensory centers
