Somatosensory System Flashcards
What sense is detected in the somatosensory system?
Touch
Choose the best option
The somatosensory system (does/does not) have a single receptor sheet where the somatosensory information is transduced.
Does not
Where can you find Somatosensory receptors?
They can be found throughout the body.
Located on our:
Skin Surfaces
Muscle Joints
Internal Organs
There are several different types of somatosensory receptors which transduce different ________ of somatosensory sensation.
Modalities
What are the three characteristics of the different types of somatosensory receptors?
Different mechanisms of transduction
Different types of axons
carry information to the brain by different pathways
Looking at this figure
Which one(s) of these cells are mechanoreceptors, a sense organ or cell that responds to mechanical stimuli such as touch or sound?
Meissner Corpuscle
Ruffini’s corpuscles
Merkel’s discs
Pacinian corpuscle
True or False: Free Nerve Endings, Somatosensory Receptors, all look the same anatomically but have four different functions.
True
True or False: Free Nerve Endings have different sensitivities due to molecular (not cellular) specializations.
True
What are the two types of Free Nerve Ending Receptors?
Thermoreceptors, transducing changes in temp.
Nociceptors, transducing pain
What are the two types of thermoreceptors Free Nerve Ending Receptors?
Cold Receptors
Hot Receptors
What do Cold receptors respond to?
Respond to sudden decreases in temp. adapted , the cold feeling will go away, over the course of a few seconds
Choose the best option
Cold receptors have (small/large) diameter (unmyelinated/ myelinated) axons. The A.P. travel at medium velocity
Small ; Myelinated
What pathway does the cold information take to send to the brain?
Spinothalamic Pathway
What is the other type of Thermoreceptors?
Hot Receptors
What do Hot Free Nerve Ending receptors respond to?
They respond to sudden increases in temp. adapt over the courses of a few seconds.
Choose the best option
Hot receptors have (small/large) diameter, (myelinated, unmyelinated) axons.
The A.P. travel at a slow velocity
Small ; Unmyelinated
What pathways do the hot receptors send information to the brain?
Spinothalamic Pathway
Nociceptors
What is nociception?
Where does it arise from?
The perception of noxious or damaging stimuli (ex: cut in the skin)
Arises from a combination of direct and indirect action on the peripheral sensors.
This include:
painful heat
Acid
Chemical activators such as ATP and bradykinin released from skin damage
What are the two types of Nociceptors receptors?
Sharp Pain Receptors
Burning Pain Receptors
For Sharp Pain receptors, what stimuli do they respond to?
They respond to stimuli causing a sharing force on the skin such as cuts or bruises.
Choose the best option
Sharp pain receptors have a (small/large) diameter (thinly/heavily) myelinated axons.
The axons fibers are Ad group, meaning that the A.P. travel at medium velocity.
Small ; Thinly
Where do the sharp pain receptors send their information to the brain?
Spinothalamic pathways
For Buring pain receptors, what kind of stimuli does it respond to?
Respond to many painful stimuli including damaging heat, sharp blow, and noxious chemicals.
Choose the best option
Bruning pain receptors have a very (small/large), (myelinated/ unmyelinated) axon.
The axon fibers are C fiber groups.
A.P. travel at a slow velocity
Small; unmyelinated
Where do burning pain receptors send information to the brain?
Thru the spinothalamic pathways
What kind of channel are the hot and cold receptors?
TRP (Transient Receptor Potential) Channels
Temp. changes are transduced by free nerve ending through the activation of TRP ion channels.
What are the structural components of TRP channels?
TRP channels are composed of 6 putative membrane-spanning units and cytoplasmic N- and C- termini
TRPV 1 to TRPV 4 are activated over different _______ ranges.
Warm Temp.
TRPM8 is a Ca2+ permeable channel activated by _________.
Lower temp
TRP can also be activated by _________ stimulations.
TRPV1 is also sensitive to __________
TRPM8 is also sensitive to _________ and ___________.
Non- temp.
Capsaicin
Methol and eucalyptol
True or False: Mechanorecptos have specialized anatomically distinct ending which causes them to transduce different kinds of touch stimuli
True
Mechanoreceptors nerve ending express “______________” ion channels
Stretch-activated
Mechanoreceptors “strecth-activated” ion channels have a ____________.
Receptor (or generator) potential
What is the receptor potentials?
Graded potentials
conducted electronically to the site of V.G Na+ and K+ channel
If receptor potential exceeds the threshold will generate A.P.
True or False:
Piezo protein is named Greek word Pressure.
Piezo is a small protein with 250 aa, weighing 30 kg.
Piezo crosses membranes 30 times.
False:
Piezo is a large protein with 2500 aa, weighing 300 kg
For Close State I of the Piezo protein,
They are built from _____ Piezo Proteins –> each contributing a blade and beam arranged around a central pore.
The channel puckers the membrane in which it sits forming a divot.
3
True or False: There is an open state of the piezo state, in which the curved blades can be flattened to pop open the pore, or a force could move the blades.
False: It is a hypothetical open state, this is just a theory.
What are the slowly adapting mechanoreceptors?
Merkel’s nerve complex, located superficially
and
Ruffini’s end organ
Located deep
What do slow adapting mechanoreceptors respond to?
Respond to changes in skin pressure
Choose the best option
Slowly adapting mechanoreceptors have (small/large), (myelinated/unmyelinated) axons.
The A.P. travel very fast
Large ; Myelinated
Where do slowly adapted mechanoreceptors send information to the brain?
Lemniscal pathway
What are the rapidly adapting mechanoreceptors?
Meissner corpuscles, located superficially
and
Pacinian corpuscle, located deep
What does rapidly adapting mechanoreceptors respond to?
Respond to vibrations or very rapid changes in skin pressure.
Choose the best option
Rapidly adapting mechanoreceptors have (small/large), (unmyelinated/myelinated) axons.
A.P. travels fast.
Large ; myelinated
What pathways do the rapidly adapting mechanoreceptors use to send information using to the brain?
Lemniscal pathway
Which mechanoreceptors have a phasic response?
Meissner and Pacinian (fast adapting)
Which mechanoreceptors have a tonic response?
Markel’s and Ruffini (slow adapting for long term contact)
True or False: The Pacinian corpuscle is a rapidly adapting mechanoreceptor whose sensory is enclosed in an onion-like capsule.
True
True or False: Pressure applied slowly to the capsule produced a response; rapidly applied pressure produces no A.P.
False: Pressure applied slowly to the capsule produced no response at all
True or False: Pacinian Corpuscle is very sensitive to vibration up to frequencies of 1000/sec.
True
The mechanism of Adaption in the Pacinian corpuscle is due to the ____________________.
Dynamic mechanics of the capsule.
The figure below shows the Pacinian corpuscle.
When a pressure step is applied to the capsule, it produces a ___________________, as a result of a transient wave of deformation that travels thru the capsule to the nerve terminal.
A _______ response occurs on the removal of the stimulation.
Rapidly adapting receptor potential
Similar
When Capsule is removed, the pressure applied to the nerve terminal produces a receptor potential that lasts for ___________________.
the duration of the entire stimulation
Summary of Mechanoreceptor afferent and their properties
Modality: __________ (Hint: the same for each receptor)
Receptor:
As seen from the free nerve ending receptors and the mechanoreceptors what are the two somatosensory pathways that these receptors travel information to the brain?
Hint: Free Nerve ending receptors use ______________
Mechanoreceptors use _____________
Spinothalamic Pathways (Pain and Temp)
Lemiscal pathways (Touch and Vibration)
True or False: Cell bodies of the Themoreceptors and the Nociceptive Receptors are in the Dorsal Root Ganglion just outside of the spinal cord.
True
True or False: Axons enter the cord and synapse contralateral ( on the opposite side) with the spinal cord neurons.
False: Axons enter the cord and synapse ipsilateral (on the same side) with spinal cord neurons.
True or False: These neurons have axons that immediately crossover to the contralateral (opposite side) of the spinal cord and ascend to the brain via the spinothalamic tract.
True
True or False: These neurons synapse onto neurons in the thalamus, and the thalamic neurons project up to the primary somatosensory cortex.
True
True or False: The Cell bodies of the mechanoreceptors are in the dorsal root ganglion
True
True or False: Axons enter the spinal cord and synapse there; then the second neuron will continue up the spinal cord ipsilateral to the medulla where they synapse onto cells in the dorsal column nuclei.
False
Axons enter the cord but do not synapse in the spinal cord ; instead, they continue up the spinal cord ipsilateral to the medulla where they synapse onto cells in the dorsal column nuclei.
True or False: The dorsal column nuclei neurons send axons that cross the midline in the medulla and ascend to the contralateral thalamus.
True
True or False: The thalamic neurons project to the primary somatosensory cortex.
True
The somatosensory system has ________ pathways carry different __________ of information.
Parallel ; Modalities
The fact that such ______ pathways differ anatomically may have important _________.
Parallel ; Clinical significance
If a patient received a knife wound cutting through the left half of the spinal cord anywhere above where the nerves serving the door enter the cord, what sensory deficits would s/he have in his/her left foot?
Lack of touch and vibration sensation
What deficits would s/he have in his/her right foot?
Lack of Pain and temp. sensation
A striking feature of connections of the sensory system is its _______________.
Topographic organziation
Certain areas of the somatosensory map are ___________. That is, there are proportionally more cells in the somatosensory cortex that respond to stimuli on areas of your body like your fingers or your lips than there are to areas like your arms or your back.
Magnified
This magnification has perceptual consequences as can be seen in a ____________
Two-point discrimination task
True or False: Generally the areas of a sensory map that are magnified correspond to areas that are behaviorally important to an animal.
True
Ex:
Our hands need to be sensitive because we use them to manipulate and explore objects
Which animal has similar magnified areas in the sensory map to us humans?
Hint: Look at the figure
Monkeys
Cats have a very magnified representation of the _________, _________, and _________.
Rabbit representation is very magnified for _______, _________, _________.
Cats: Whiskers, face, and paws
Rabbit: Nose, whiskers and jaw
Cortical somatosensory maps are _______ that is they can be modified by experience.
Plastic
In addition to having maps of the receptor sheet across the cortical surface, Sensory cortical areas tend to also have the cells arranged in ______ with cells within a ________________.
Hint: look at the image
Columns; a given column having similar response properties.
In any given region of somatosensory cortex there are ________ of cells within the ____________ but with different modalities.
Columns ; the same receptive field
Cortical columns are _________ columns. There are no discernible anatomical differences between columns.
Functional
