Neuro: Sensory Physiology Flashcards
define sensory receptor
neuronal specialization that allows transduction of physical stimuli into neural activity
during transduction, a sensory receptor converts stimulus energy into ____
receptor potential
a receptor potential is which type of potential?
graded
if the the receptor potential reaches threshold for opening gated Na channels, a __ is generated
action potential
information from sensory receptors is relayed to ___ by release and detection of __
interneurons ; neurotransmitters
after the interneuron, information is processed and __ on its way to the __
integrated, cerebral cortex/subcortical area
sensory receptors can be what 2 things?
- peripheral nerve endings of sensory neutron
2. specialized cells that synapse with sensory neutron
t/f encapsulation of nerve ending changes the ability of the nerve ending to sense stimuli
true
mechanoreceptors sense __
changes is stretch and pressure
mechanoreceptors are located ___
skin, muscle, tendons, blood vessels
thermoreceptors sense _
cold/warmth
thermoreceptors are located __
skin
photoreceptors sense __
light
photoreceptors are located _
retina
chemoreceptors are located
tongue and nose
chemoreceptors sense _
certain chemical compounds
nociceptors are located _
throughout the body
nociceptors sense _
stimuli causing tissue damage
what is the most unique class of receptors?
nociceptors
nociceptors are polymodal, meaning __
they respond to a number of different stimuli
t/f each receptor type is particular partial to one stimulus modality, but can be stimulated by other types if the stimulus is strong enough
true
t/f all receptors of the primary sensory neurons respond tp the same stimulus modality
true
define receptive field
area of body surface in which stimulus leads to activation of sensoryneuron
stimulas location can be determined by neurons in the __ based on __
brain; which sensory receptors in the periphery have been activated
there is a ___ organization of sensory afferents in the cerebral cortex
topographical
acuity is based on receptive field __
size
what is acuity?
precision of stimulus location
the __ the size of the receptive field, the greater the acuity
smaller
the receptive field size is often determined by __
density of sensory neurons
what organization of sensory neurons would award the greater acuity?
high density of the same modality
how can acuity be acuity be measured?
2-point discrimination threshold
acuity is ___ by lateral inhibition
increased
what is lateral inhibition>
each sensory neutron can activate local inhibitory interneuron that inhibit nearby sensory neurons
receptive fields of adjacent sensory neurons of the same modality often __
overlap
when receptive fields overlap, a stimulus can activate both sensory neurons, but _
one more strongly than the other
where is the most effective location in a receptive field to apply stimulus?
center
stimulus intensity is encoded by what 2 things?
- frequency of ap
2. # of sensory neurons activated
encoding stimulus intensity by frequency is called __
frequency coding
how can a weak stimulus manage to cause activation?
by landing in the middle of the receptive field
is it easier to find the site of stimulus for a week or string stimulus? why?
weak; because only sensory neutron that was directly applied will activate, weaker requires higher acuity because it can only activate one sensory neutron
what is the concept of adaption?
sensory receptors decrease sensitivity to stimulus of constant strength
in adaption, the frequency of ___ decreases
action potentials
sensory receptors can be either __ or __ adapting
slow/rapidly
rapidly adapting receptors are also called __
phasic receptors
slowly adapting receptors are also called _
tonic receptors
phasic receptors sgnal __
changes in stimulus intensity, either just onset or onset/offset
tonic receptors signal __
continued pressence of stimulus
in polyneuronal pathways, sensory neurons synapse onto __ neurons in the __ or __
second order ; brainstem and spinal cord
most sensory pathways ___
decussate (cross midline of the body)
stimulus on the right side of the body is processed in the __ side of the brain
left
what is converence>
higher order neutron receives inputs from multiple lower order neurons
what is divergence>
lower order neutron gives info to multiple higher order neurons
convergence and divergence allow for sensory ___
processing
what are labeled lines>
pathways dedicated to a specific stimulus modality
labelled lines carry ___ information to the ___ via the___
perceptive; cerebral cortex, thalamus
multimodal pathways oft have targets in the __ and often carry information on __, __ and _
subcortical area; pain, itch, temperature
neurons in the primary sensory cortex project into ___ areas for multimodal processing
associational cortical areas
in multimodal processing dome of the information targets subcortical areas that are responsible for __, __ and __
reflexes, arousal, and attention
what are the 6 types of somatosensory receptors on the body surface?
- meissner’s corpuscles
- hair plexus
- merkel’s disks
- Ruffini’s corpuscles
- pacinian corpuscles
- free nerve endings
what is the modality of mess. corpuscles?
tough and dynamic pressure
where are mess corpuscles located?
glabrous skin (without hair)
what is the threshold for activation of mess corpuscles?
low
what is the modality of hair plexus?
touch dynamic pressure,
where are hair plexus located.
associated with hair follicles
what is the threshold for hair plexus?
low
what is the adaption type for mess corpuscles?
rapid
mess corpuscles are encapsulated by __ and located where in the skin
collagenous matrix; upper layer of the debris
how to hair plexi associate with hair follicles?
wrapping around them
ruffinis corpuscles are often located above __
joints
mechanoreceptors contain mechanically gated ion channels that mostly conduct __ and __ions
ca and na
deformation of ___ causes ion channel oping in mechanioreceprors
plasma membrane
how does encapsulation connective tissue influence adaption>
capsule elastically rebounds despite sustained stimulus, closing ion channels
thermoreceptors are what receptor type?
free nerve ending
thermoreceptors respond to temperature between __ and __
10 and 45
thermoreceptors contain __ channels that allow influx of ca and na
transient receptor potential
cold receptors can also be activated by what chemical compounds>
menthol
heat receptors can also be activated by what chemical compund>
camphor
what are the 3 types of nocireceptors?
- mechanical
- temp
- polymodal
mechanical nocireceptor respond to
intense mechanical stimuli
thermal nocireceptors respond to __
temperature outside of 0-45 range
polymodal nocireceptors respond to _
intense mechanical and thermal stimuli, as well as chemicals released in tissues, such as histamine, prostaglandins, bradykinin and H+
mechanical and thermal nocireceptors are __ conducting via ___ fibres
fast; myelinated A sigma
polymodal nocireceptors are ___ conducting via __ fibres
slow; unmyelinated C
what is capsaicin?
chemical in chilli peppers that activates thermal nocireceptors
what causes referred pain?
projections of nocireceptors in skin and skeletal muscles and internal organs often converge onto the same second order neurons, causing somatic and visceral pain to be indistinguishable
give an example of referred pain
a myocardial infarction is felt as pain in left arm
what is hyperalgesia?
increased sensitivity of nocireceptors to pain
what causes hyperalgesia?
inflammation caused by the immune system
hyperalgesia is usually due to ___ sensitization
peripheral
what types of drugs can act as analgesics by preventing sensitization of nocireceptors?
anti-inflammatory, such as COX inhibitors
what is allodynia?
after an injury, perception of mechanical stimuli as painful
allodynia is due to __ sensitization
central
the central sensitization of allodynia is caused by
increased excitability of second-order neurons in the spinal cord
what is the endogenous analgesic system?
activation of certain brain centres (periductl grey, raphe Magnus) leading to suppression of pain
how does the endogenous analgesic system work?
descending pathways (midbrain to local inhibitory interneurons) suppress synaptic transmission from nocireceptors
what does the endogenous analgesic system release ?
opioids
opioid receptors are expressed on __ and __
nocireceptors and second-order nocioreceptive neurons
what is the premise of gate control of pain?
mechanical / temperature stimuli applied to a body area experiencing nocireceptive stimulus can reduce pain sensations
what is the proposed mechanism of gate control of pain?
mechanoreceptors and thermoreceptors activate local inhibitory interneurons that prevents release of NT (glutamate) that would cause pain sensation
the dorsal column pathway is a ___ pathway type
labelled line
the dorsal column pathway is also called the __
medial lemniscus
the dorsal column pathway conveys information of __, __, __ and ___
touch, pressure, vibration, and proprioception
what is proprioception?
sensory information from muscles, tendons and joints
describe the steps of the dorsal column pathways
primary sensory neuron to second order sensory neutron in brainstem to third order in thalamus to neurons in the primary sensory cortex
the dorsal column pathway decussates at the level of the __
brain stem (medulla)
the anterolateral pathway is also called the ___
spinothalamic pathway
the anterolateral pathway conveys information of ___, __ and __
temperature, pain, itch
describe the steps of the anterlateral pathway
primary sensory neuron to second order spinal cord neutron to third order thalamus neuron to primary sensory cortex
the anterolateral pathway decussates at the level of the
spinal cord
describe divergence in the anterolateral pathway
second order neutron also synapses onto neurons in the reticular formation(brain stem)
what is the impact of divergence in the anterolateral pathway?
alertness and arousal
t/f the anterolateral and dorsal pathways use the same thalamic neurons
fasle
