NURS 5357 NEUROBIOLOGY EXAM 3
ACTUAL QUESTIONS AND ANSWERS
BUNDLED FULL SOLUTION VIEW AHEAD
●● compare and contrast mechanoreceptors and nociceptors
Answer: mechanoreceptors is for touch and also use sensory
transduction while nociceptors are for pain ad they have free nerve
endings of small myeline and unmyelinated fibers
they both decussate at their second order neurons (cross hemispheres)
for mechanoreceptors, the second order cross to the contralateral
hemisphere at the medulla
for nociceptors, the second order cross hemispheres at the spinal cord
●● describe the ascending pathway that communicates signals of touch
and vibration
Answer: the axons of first order enter spinal cord directly
ascend ipsilaterally (same side) without synapsing in spinal cord
asend in dorsal white matter of cord
synapse with second order cell in brainstem
decussate in the medulla
synapse with third order neurons in thalamus
third order neurons project to somatosensory cortex
,●● describe ascending pathway that communicates signals of pain
Answer: first order in dorsal root ganglia
enter spinal cord directly
synapse immediately with second order in dorsal horn of spinal cord
second order decussate and project to brainstem
synapse with third order in thalamus and reticular formation
ascend in later white matter of cord
project to primary somatosensory cortex
●● what chemical signals are involved in pain sensation
Answer: tissue damaged which leads to release of signaling molecules
(histamines, bradykinin, prostaglandin, serotonin) which leads to
inflammation which leads to nociceptor excitability
nociceptor excitability then leads to the release of substance P (by C
fiber and a delta fibers) which triggers more histamine and serotonin
release which excites nociceptors
overall its a positive feedback loop
●● describe transduction of pressure and vibration at a pacinian
corpuscle
Answer: when pressure is applied, the laminated structure encapsulating
the nerve ending deforms and transmits the force to the axon
this then leads to the mechanically gated ion channels to stretch and
open which leads to Na influx
,this produces a receptor generator potential which is a local change in
membrane potential
if it reaches s threshold, it leads to an action potential towards to CNS
(Afferent)
●● what is a generator receptor potential and what are its characteristics
Answer: it is a local change in membrane potential
graded electoral potential which means that its not all or nothing, can be
lower or higher dpd on stim
action potential can only be reached if its above the threshhold
●● what types of fibers communicate pain signals
Answer: C fibers and a delta fibers
C fibers are small unmyelinated fibers and are relatively slow
A delta fibers are small myelinated fibers and are faster
they both terminate in superficial layers of spinal cord grey matter
C fibers terminate in layer 1 and 2
a delta fiers terminate in layer 1 and 5
both synapse immediately in dorsal horn
there is also A alpha which transmits signals bc they're the fastest
because they're largest and heavily myelinated
, ●● how are pain signals in the spinal cord modulated by the descending
analgesic pathways
Answer: goes from the cortex to the PAG region
in the dorsal horn in spinal cord, enkephalin spinal interneurons (raphe
nuclei) make axo synaptic synapses on presynaptic erm of first order
nociceptor neurons which release SP
leads to no release of SP which leads to no EPSPS in in 2nd order
nociceptor and no Ian signal
the enkephalin blocks Ca channels
●● what is the function of the cornea of the eye
Answer: the cornea is where the light first passes
it has a fixed curvature which refracts the light and forms a reverse
image
●● define accommodation an describe the shape of the lens for close and
far away objects
Answer: accommodation is when the shape of the lens changes shapes
ciliary muscle adjusts the shape of the lens
when the object is far, the lens flattens
if the object is near, the lens curves
●● how is the retina organized
Answer: 3 layers of cels separated by 2 layers of synapses
ACTUAL QUESTIONS AND ANSWERS
BUNDLED FULL SOLUTION VIEW AHEAD
●● compare and contrast mechanoreceptors and nociceptors
Answer: mechanoreceptors is for touch and also use sensory
transduction while nociceptors are for pain ad they have free nerve
endings of small myeline and unmyelinated fibers
they both decussate at their second order neurons (cross hemispheres)
for mechanoreceptors, the second order cross to the contralateral
hemisphere at the medulla
for nociceptors, the second order cross hemispheres at the spinal cord
●● describe the ascending pathway that communicates signals of touch
and vibration
Answer: the axons of first order enter spinal cord directly
ascend ipsilaterally (same side) without synapsing in spinal cord
asend in dorsal white matter of cord
synapse with second order cell in brainstem
decussate in the medulla
synapse with third order neurons in thalamus
third order neurons project to somatosensory cortex
,●● describe ascending pathway that communicates signals of pain
Answer: first order in dorsal root ganglia
enter spinal cord directly
synapse immediately with second order in dorsal horn of spinal cord
second order decussate and project to brainstem
synapse with third order in thalamus and reticular formation
ascend in later white matter of cord
project to primary somatosensory cortex
●● what chemical signals are involved in pain sensation
Answer: tissue damaged which leads to release of signaling molecules
(histamines, bradykinin, prostaglandin, serotonin) which leads to
inflammation which leads to nociceptor excitability
nociceptor excitability then leads to the release of substance P (by C
fiber and a delta fibers) which triggers more histamine and serotonin
release which excites nociceptors
overall its a positive feedback loop
●● describe transduction of pressure and vibration at a pacinian
corpuscle
Answer: when pressure is applied, the laminated structure encapsulating
the nerve ending deforms and transmits the force to the axon
this then leads to the mechanically gated ion channels to stretch and
open which leads to Na influx
,this produces a receptor generator potential which is a local change in
membrane potential
if it reaches s threshold, it leads to an action potential towards to CNS
(Afferent)
●● what is a generator receptor potential and what are its characteristics
Answer: it is a local change in membrane potential
graded electoral potential which means that its not all or nothing, can be
lower or higher dpd on stim
action potential can only be reached if its above the threshhold
●● what types of fibers communicate pain signals
Answer: C fibers and a delta fibers
C fibers are small unmyelinated fibers and are relatively slow
A delta fibers are small myelinated fibers and are faster
they both terminate in superficial layers of spinal cord grey matter
C fibers terminate in layer 1 and 2
a delta fiers terminate in layer 1 and 5
both synapse immediately in dorsal horn
there is also A alpha which transmits signals bc they're the fastest
because they're largest and heavily myelinated
, ●● how are pain signals in the spinal cord modulated by the descending
analgesic pathways
Answer: goes from the cortex to the PAG region
in the dorsal horn in spinal cord, enkephalin spinal interneurons (raphe
nuclei) make axo synaptic synapses on presynaptic erm of first order
nociceptor neurons which release SP
leads to no release of SP which leads to no EPSPS in in 2nd order
nociceptor and no Ian signal
the enkephalin blocks Ca channels
●● what is the function of the cornea of the eye
Answer: the cornea is where the light first passes
it has a fixed curvature which refracts the light and forms a reverse
image
●● define accommodation an describe the shape of the lens for close and
far away objects
Answer: accommodation is when the shape of the lens changes shapes
ciliary muscle adjusts the shape of the lens
when the object is far, the lens flattens
if the object is near, the lens curves
●● how is the retina organized
Answer: 3 layers of cels separated by 2 layers of synapses
