sensory physiology Flashcards
what are the two schemes peripheral nerves are classified
- by contribution to a compound action potential (A, B,
C waves) - based on fiber diameter, myelin thickness,
conduction velocity (class I, II, III, IV)
what is receptor adaptation
when a stimulus persists unchanged for a period of time without a change in position or amplitude, the neural response diminishes or is lost
what kind of stimulation do slow adapting receptors respond to
prolonged and constant
what kind of stimulation do fast (rapid) adapting receptors respond to
the beginning or end of a stimulus – only active when the stimulus intensity increases or decreases
meissner corpuscle
adaption rate
sensation
receptive field
rapid adapting
tap, flutter
small
Pacinian corpuscle
adaptation rate
sensation
receptive field
rapid adapting
vibration
large
merkel disk
adaptation rate
sensation
receptive field
slow adapting
touch, pressure
small
ruffini corpuscle
adaptation rate
sensation
receptive field
slow adapting
skin stretch
large
Pre-synaptic inhibition
more powerful form of inhibitory control in all primary afferent fibers
improves brain’s ability to localize signal
actually a diminished excitatory signal:
Gaba-nergic associated influx of Cl
hyperpolarization
decreased Ca influx
less NT release
what improves the brain’s ability to localize signal
receptive fields
pre-synaptic inhibition
steps to cortical processing
initial processing of the signal
integration of the initial processing into larger schemes
emotional response to the processing
which cortex layers are enlarged in primary sensory cortex
III and IV (main site of termination of axons from the thalamus)
main output neurons
pyramidal cells (cortex layer V)
Columns (sensory cortex)
extend
modality
differences with surrounding cells
extend through all 6 layers
neurons stacked are fundamentally similar; neurons side
by side are significantly different
columns side by side receive sensory input from same
part of body, but different modalities
S1
location
areas
involved in?
post central gyrus
brodman areas 3,1,2
first stop for most cutaneous senses
involved in the integration of information for position
sense, size and shape discriminationS2
location
input
involved in?
wall of the sylvian fissure
input from S1
involved in comparison between objects, different
tactile sensatoins, and dtermining whether
something becomes a memory
Parieto-temporal-occipital association complex (PTO)
High level interpretation of sensory inputs
naming objects
analyzes spacial coordinates of self in environment
doesn’t physically exist, more of a physiological combo
what permits focusing activities
S1 sending projections back down to subcortical structures (most often thalamus)
descending corticothalamic axons > ascending
thalamocortical axons
what links the primary and association areas of the sensory cortex and allows for simultaneous processing of multiple sensations
cortico-cortical projections (parallel paths of sensation)
can be ipsi or contra
what are corticofugal signals and what do they do
transmitted back from cortex to lower relay stations (thalamus, medulla, SC)
controls intensity of sensory sensitivity
typically inhibitory and suppresses sensory input
doctrine of specific nerve energies
no matter where along the afferent pathway is stimulated, sensation felt is determined by receptor the pathway is for
law of projections
no matter where along the afferent pathway is stimulated, perceived sensation is from origin of sensation
silent nociceptors
related to phenotype switching – rarely stimulated sensory receptors can undergo phenotype switching to become another modality receptor?)
nociceptor axons
slowly conducting unmyelinated (C fibers)
thinly myelinated (Abeta fibers)
w/ free endings
