Test 2 - Lecture 3 (Transmission of Sensory Information) Flashcards
nerve endings contain stimulus-gated ion channels -> generator potentials
receptive field
high density of voltage gated Na+ channels -> threshold to trigger action potentials
trigger zone
action potentials propagate along -> transmission to first synapse in the dorsal horn
primary afferent fibers
neurotransmission of nervous information occurs via
synaptic relays
somatosensory information is transmitted from the periphery to the primary sensory cortices via
multi-synaptic relay
presynaptic release of neurotransmitter in response to inputs
decoding
postsynaptic response to the released neurotransmitter
recoding
the response of each relay neuron is determined from the summation of multiple inputs
integration
strengthening or lessening the response of each relay neuron to its inputs via other signals that MODULATE the presynaptic release of neurotransmitter, and the post synaptic response to the neurotransmitter
processing
excitatory interneuron __________ synaptic transmission
amplifies
inhibitory interneuron _________ synaptic transmission
diminishes
________ interneurons provide a structure to “focus attention” upon the central point at which the stimulus intensity is greatest
inhibitory
feedforward inhibition and feedback inhibition function to…
allow the brain to more accurately focus attention upon the location and nature of the stronger stimulus
hierarchical processing of ascending information through synaptic relays… the peripheral receptors are NOT affected
modulation of non-nociceptive somatosensory information
allow specific regions of the cortex to “selectively focus attention” upon one particular source of ascending sensory input, suppressing other “background signals” that would be interpreted as “interfering noise”
descending inhibition
ascending signals
dampen out inputs arising from receptive fields that are only weakly stimulated
descending signals
allow higher centers within the brainstem and brain to modulate the incoming flow of peripheral somatosensory information
hyperalgesia
increased sensitivity to the stimulus
analgesia
reduced sensitivity to the stimulus
nociceptive A(gamma) and C fibers project to second order neurons located within
lamina I and lamina V of the dorsal horn
lamina ____ neurons will receive input from visceral nociceptors in addition to receiving both noxious and non-noxious mechanoreceptors
V
C fiber activity determines the activity of the inhibitory interneuron by
uninhibited transmission of the nociceptive input
A(beta) fibers determines the activity of the inhibitory interneuron by
inhibiting transmission of the nociceptive input through the relay neuron
nociceptive input _____ the gate-control inhibitory interneuron
restrains
non-nociceptive mechanoreceptor input _______ the activity of the gate-control inhibitory interneuron
strengthens
the extent of interneuronal gating is dependent upon the balance between
nociceptive and non-nociceptive inputs
afferent sensory fibers may branch extensively once they enter the spinal cord, to synapse upon numerous interneurons located within the gray matter, to modulate the activity of neurons they synapse upon
theory of analgesia
two primary descending pathways originate from
periaqueductal gray matter (serotonergic: serotonin)and locus ceruleus (noradrenergic: norepinephrine)
analgesia produced by stimulation of the periaqueductal grey matter of
the midbrain
_____ opiods enkephalins, endorphins, and dynorphins activate to produce analgesia
endogenous
_______ opiod morphine activates to produce analgesia
exogenous
receptors on the presynaptic terminal of the primary afferent nociceptive fiber (stimulating the enkephalin receptor will hyperpolarize the membrane)
presynaptic inhibition (fewer Ca channels will open, these will remain open for shorter time = reduced or blocked NT release
receptors on the postsynaptic membrane (stimulating these opiod receptors will hyperpolarize the resting potential of the postsynaptic membrane)
postsynaptic inhibition (EPSP will be less likely to reach a threshold for stimulating an action potential from the postsynaptic neuron)
