Sensory and Motor Pathways Flashcards
Features common to all sensory systems
- change of a sensory stimuli into a graded change in membrane potential
- change in membrane potential -> change in neuronal firing rate
- Info comes into CNS on “labeled lines” (different distinguishable neurons), combined and further processed to generate output responses
common channels underlying sensory responses?
Cation P-loop channels
CNG Channels - visual
Trp - chemicals and temperature
adaptation
with a sustained stimulus, response will peak, then after a while will decrease (ex: staying out in a dark night then coming into light and saying HOLY SHIT THAT’S FUCKIN BRIGHT…then you get used to it)
What regulates adaptation?
Ca2+
How does adaptation work?
Partial densensitization. Sensitive during weak stimuli and toned down in prolonged strong stimuli, to maintain dynamic range
Why is sensory info segregated? (labeled lines)
labeled lines ensure that the CNS knows what type of info it is receiving
capsaicin
“pepper” channel. activates heat sensitive channel that responds to “burning” temperatures
How do different tastes work?
Different tastes, same transduction…due to the differential expression of receptors leading to distinct info being sent to CNS
receptive field
set of stimuli that affect the firing of a sensory neuron. COntain both positive and negative stimuli
Common organization for receptive fields
center/surround organization with opposing responses in the two areas…
stimuli that are focused on the positive area of the receptive field are detected more strongly than stimuli that are constant across receptive field
Touch receptive fields
Large behind legs, small on finger
Visual receptive fields
large in periphery, small in fovea
Where in brain does sensory info enter?
distinct regions of CORTEX
Area of cortex and sensory info?
area of cortex devoted to info coming in from different locations is related to complexity of receptive field coming from that area
ex: foveal representation in cortex is much larger than the area of visula space being covered. Also, speech processing areas are greatly expanded
How do motor units work?
motor neurons connect to a subset of muscle fibers in a single muscle….fibers are controlled as a unity by motor neuron….each muscle recieves input from a single motor neuron….muscles with finer control have smaller motor units
