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Somatosensory System 3/4 Flashcards

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1
Q

The somatosensory system

A

Sensory stimuli that reach the conscious level of perception
Specialized cells that monitor specific conditions in the body or external environment
Somatic/General Senses = Somatosensory
Temp, pain, touch, pressure, vibration, proprioception
Simple receptors located anywhere on body

Special Senses: (these are not part of the somatosensory system)
Are located in sense organs such as the eye or ear
Olfaction, vision, gustation, hearing, equilibrium
Complex receptors located in specialized sense organs

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2
Q

from sensation –> perception

-role of receptor

A

Stimulus as physical energy –> sensory receptor

*Receptor acts as a transducer
Translate physical energy to something (convert a physical pressure into a neural signal)

Intracellular signal –> usually change in membrane potential

Stimulus –> threshold –> action potential to CNS

Integration in CNS –> cerebral cortex or acted on subconsciously

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3
Q

Sensory Receptors

  • role/function
  • specific or nah
A

Transduction – conversion of environmental stimulus into action potential by sensory receptor
Receptors specific for particular type of stimulus
Specificity is due to structure of receptor

A stimulus is a change in the environment that is detected by a receptor
Sensation: the awareness of changes in the internal and external environment
Perception: the conscious interpretation of those stimuli

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4
Q

Sensation **

A

Sensation: the awareness of changes in the internal and external environment
Perception: the conscious interpretation of those stimuli

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5
Q

Perception **

A

Perception: the conscious interpretation of those stimuli

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6
Q

Sensory Neurons

  • location of cell bodies and recptors
  • type
A

The cell bodies of the neurons are in the dorsal root ganglia
The receptors are in the periphery

The cells are pseudounipolar
Peripheral and central components are continuous- dendrites sort of merge into the axon

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7
Q

Classification by Location

A

*Exteroceptors
Respond to stimuli arising OUTSIDE the body
Receptors in the skin for touch, pressure, pain, and temperature
Most special sense organs

*Interoceptors (visceroceptors)
Respond to stimuli arising in internal viscera and blood vessels
Sensitive to chemical changes, tissue stretch, and temperature changes

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8
Q

What Must Sensory Cells Do

A

They must be able to convert stimulus energy into an electrical signal

Stimulus changes the permeability cation channels in the nerve ending –> depolarization
This depolarization is known as a receptor potential
Receptor potential proportional to stimulus magnitude
If receptor potential reaches threshold, then action potential are generated in the afferent fiber
Rate of APs proportional to magnitude of depolarization

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9
Q

Sensory Neuron/Fiber Differences

A
  • Axon diameters vary
  • Receptive fields differ
  • Differences in the temporal dynamics of their responses
  • Differences at the nerve ending in the periphery
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10
Q

which is the slowest transmission

A

Pain and temperature neurons-

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11
Q

Axon diameters vary

A

Sensory neurons of muscle- large diameter axons
Sensory afferent Ia fibers
(one-A)
Fastest

Touch neurons- medium diameter axons
Sensory afferent- Aβ fibers

*Pain and temperature neurons- small diameter
Sensory afferent- Aδ and C fibers
Slowest

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12
Q

***Two-Point Discrimination

A

At what distance can you determine two separate points as two separate points

Varies across the body based on receptive fields and innervation amount

density of receptors within the skin determines the sensitivity of the skin, so the fingers have the finest two point discrimination, indicating higher density of mechanoreceptors–and thus more cortical tissue dedicated to these areas

Fingertips: densely innervated by cells with small receptive fields –> only need a small difference to detect as two points

Back: sparsely innervated by cells with large receptive fields –> need much bigger difference to detect as two points

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13
Q

Sensory Neuron/Fiber Differences: Receptive fields differ

A

*Receptive fields differ
What area does it cover- how much of body does it cover

Receptive field- how much area is the receptor cell able to collect information from

Densely innervated areas, like fingertips, have cells with relatively small receptive fields
Areas with less innervation, like the back, have cells with larger receptive fields

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14
Q

Sensory Neuron/Fiber Differences: Differences in the temporal dynamics of their responses - rapidly adapting vs slowly adapting

A

Rapidly adapting: fire rapidly after stimulus onset and then fall quiet as stimulus is maintained
Useful for determining stimulus movement

*Slowly adapting: sustain their firing in response to the stimulus
Useful for spatial attributes of stimulus (size, shape)

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15
Q

Sensory Neuron/Fiber Differences: Differences at the nerve ending in the periphery

A

Encapsulated endings: nerve fiber ending is surrounded by a non-neural component, often connective tissue, that helps with the function

Free nerve ending: just a regular old nerve ending with nothing added on

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16
Q

Encapsulated endings (!)

A

Encapsulated endings: nerve fiber ending is surrounded by a non-neural component, often connective tissue, that helps with the function

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17
Q

Free nerve ending

-process/used for:

A

Free nerve ending: just a regular old nerve ending with nothing added on

process pain and temperature

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18
Q

Four Types of General Sensory Receptors

A

Pain: nociceptor (more about these next time)
Temperature: thermoreceptor (mostly ignored by Ch 9)
Physical: mechanoreceptor
Chemicals: chemoreceptors

All can be found in both somatic (exteroceptors) and visceral (interoceptors) locations except:
Proprioceptors (a mechanoreceptor) are somatic only

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19
Q

mechanoreceptor

A

Detect membrane distortion

  • Three receptor types:
  • Tactile Receptors
  • Proprioceptors
  • Baroreceptors
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20
Q

Mechanoreceptors- Tactile Receptors

6 functions

A

Detect membrane distortion
Detect touch, pressure and vibration on skin
Detect hair movement
Detect fine touch
Detect deep pressure
Respond to itch (respond among other to histamine) and light touch (detect changes in shape like bending)

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21
Q

Merkel Cells and Afferents

A

*Merkel cells are epithelial cells
Associated with sensory nerve endings to form a Merkel cell-neurite complex
The complex essentially functions as the receptor
Slowly adapting
*25% of the mechanosensory afferents in the hand
-Especially enriched in the fingertips
Only mechanoreceptor type to sample from epidermis
Express the mechanotransduction channel Piezo2
Both the Merkel cell and the fiber

*respond best to static stimuli, small receptive fields
• 25% of the mechanosensory afferents in the hand
• Especially enriched in the fingertips
• Only mechanoreceptor type to sample from epidermis
• Express the mechanotransduction channel Piezo2
• Both the Merkel cell and the fiber
• Ability to recognize the stimulus
• Merkel cell: signals static aspects of touch stimulus, like pressure
• The associated nerve fiber signals the dynamic aspects of the touch stimulus
• Have the highest spatial resolution of all the mechanosensory afferents
• Very sensitive to points, edges, and curvature
• Braile reading : Only slowly adapting Merkel cell afferents (top panel) provide a high-fidelity representation of the Braille pattern—that is, the individual Braille dots can be distinguished only in the pattern of Merkel afferent neural activity.

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22
Q

Meissner Afferents and Corpuscles

  • slow vs rapid
  • location
  • shape
A

Rapidly adapting
Fire on an offset
(comparing to merkel)
About 40% of the mechanosensory afferents from the hand
Meissner corpuscles are in dermal papillae, close to the skin surface
The weird shape is due to connective tissue that forms a capsule
Encapsulating

Capsule contains flattened laminar cells and nerve terminals
The center of the capsule contained endings of 2-6 nerve fibers
When skin is indented, it changes the tension on the collagen fibers that deforms the corpuscle  action potentials in afferent fiber
Larger receptive field than Merkel afferents, so lower spatial resolution
Can also detect low frequency vibration
Ex: when textured objects are moved against the skin

May be important for grip
Can detect slippage between your hand and an object

slide 25/26

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23
Q

Pacinian Afferents and Corpuscles

A

Rapidly adapting, more so than Meissner’s corpuscles
Also have a lower response threshold
Super rapidly adapting
Fire, but do not keep firing
About 10-15% of the mechanosensory afferents from the hand
Located: deep within the dermis (the deepest)
Look like cross-sections of tree trunks or onions
Concentric circular layers: Layers act as a filter, permitting only
Receptive fields are large
Well-suited to detect vibrations transmitted by objects
Hitting the hand, leaving the hand
Believed to be super important for tool use and writing

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24
Q

Ruffini Afferents and Corpuscles

-good at detecting : ?

A

Slowly adapting (respond the entire time the stimulus is there)
About 20% of the mechanosensory afferents from the hand
Located deep in the skin- But not as deep as the pacinian
*Also found in ligaments and tendons
Elongated spindle-shape
Long axis usually parallel stretch lines of skin
Thus they are really good at pereciving stretch of the skin… can tell if fingers are moving past eachother
Makes them sensitive to skin stretching due to moving fingers

They are probably also important for helping to convey information about the position and placement of the hands and fingers
This would overlay onto proprioception

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25
Reading Braille
Only slowly adapting Merkel cell afferents (top panel) provide a high-fidelity representation of the Braille pattern—that is, the individual Braille dots can be distinguished only in the pattern of Merkel afferent neural activity.
26
Mechanoreceptors- Proprioceptors
Provide information about the placement of the body and its parts by reading information about mechanical forces Mostly low threshold Integrate their information with the vestibular system Examples: muscle spindles, Golgi tendon organs, and join receptors -Detect positions of joints and muscles *Muscle spindles Modified skeletal muscle cell Monitor skeletal muscle length *Golgi tendon organs Dendrites around collagen fibers at the muscle-tendon junction Monitor skeletal muscle tension J*oint capsule receptors Monitor pressure, tension and movement in the joint
27
Anatomy of the Muscle
Striated muscles are made of muscle fibers that have two parts, outer and inner: Outer fiber = extrafusal fiber (does the work) Inner fiber = intrafusal fiber
28
Muscle Spindles
collection of 6-8 specialized muscle fibers that are located within the muscle mass - do not contribute significantly to the force generated by the muscle. - are specialized receptors that signal (a) the length and (b) the rate of change of length (velocity) of the muscle. * Modified skeletal muscle cell * Monitor skeletal muscle length
29
Golgi Tendon Organ
A proprioceptor, sensory organ that receives information from the tendon, that senses TENSION. Lift weights --> the golgi tendon organ tells you how much tension the muscle is exerting. Too much muscle tension  the golgi tendon organ inhibits the muscle from creating any force (via a reflex arc), thus protecting the you from injuring itself. Decreases activity of alpha motor neuron Because alpha motor neurons do all the “work”
30
2 Pathways We Cover for Tactile Information
* Dorsal column-medial lemniscal pathway: Tactile information from body * Trigeminothalamic System: Tactile information from the face
31
Dorsal Column-Medial Lemniscal System
Transmits TACTILE information from the BODY to the CNS Axons of mechanosensory afferents enter through the dorsal roots Axons branch into ascending and descending branches Synapse on projection neurons located deep in the spinal cord and on neurons further up in the brainstem Spinal cord targets are in deep layers III, IV, V * Leads to parallel columns* - Dorsal column= ascending axons from sensory neurons - Postsynaptic dorsal column projection= axons from projection neurons in spinal cord *Dorsal columns are topographically organized -Lower limbs more medial Fasciculus gracilis or Gracile tract -Upper limbs more lateral Facsciculus cuneatus or Cuneate tract SLIDE 54
32
Dorsal Column-Medial Lemniscal System: Dorsal columns are ____ organized
Dorsal columns are topographically organized Lower limbs more medial: Fasciculus gracilis or Gracile tract Upper limbs more lateral: Facsciculus cuneatus or Cuneate tract
33
Trigeminothalamic System
Tactile information from the face The cell bodies of the mechanosensory neurons reside in the trigeminal ganglion 3 subdivisions to innervate specific areas of head and face- ophthalamic, maxillary, and mandibular Axons continue enter the brainstem at the level of the pons Synapse on the neurons in the principal nucleus of the trigeminal complex Trigeminal complex has two major parts: principal nucleus and the spinal nucleus Most of the afferents conveying low-threshold cutaneous information synapse in the principal nucleus The spinal nucleus has multiple subnuclei and each receive collaterals from the mechanoreceptors, but also receive pain/temperature/non-discriminative touch information Axons from the trigeminal complex cross the midline and ascend to the ventral posterior medial nucleus of the thalamus (VPM) VPM sends axons through internal capsule to primary and secondary somatosensory cortices
34
Proprioceptive Information from the Body - cell bodies - axons - lower limb information -->? - upper limbs information -->?
Cell bodies live in dorsal root ganglia Axons sent into spinal cord and branch into ascending and descending tracts.. And branch some more too Branches extended to the ventral horn, where motor neurons live, to help mediate reflex arcs Information from lower limbs synapses in Clarke’s nucleus, which is a region in the medial portion of the dorsal horn of the spinal cord Enter around sacral region- travel with dorsal column to a higher level of the spinal cord, and then synapses here Axons from Clarke’s nucleus ascend as the dorsal spinocerebellar tract Axons sent to cerebellum Axon collaterals will also be sent neurons near the gracile nucleus Synapse on these proprioceptive neurons of the dorsal column nuclei Information joins the medial lemniscus Axons carrying information about the upper limbs enters the spinal cord and then travels via the dorsal column (cuneate tract) to the medulla Synapse on proprioceptive neurons in the dorsal column nuclei, including in the external cuneate nucleus Axons from these neurons go two places Ipsilateral axons ascend to cerebellum Other axons cross midline to join the medial lemniscus and go on to the VPL
35
Proprioceptive Information from the Face | -cell bodies
Also conveyed through the trigeminal nerve, but the cell bodies are not located in the trigeminal ganglion Cell bodies are located in the mesencephalic trigeminal nucleus Near the periaqueductal gray and midbrain Details are fuzzy, but the information eventually reaches the thalamus and somatosensory cortices
36
Somatosensory Thalamus- VPL and VPM
Ventral Posterior Complex= VPL and VPM Information arrives and synapses in the thalamus in a somatotopic manner Medial lemniscus brings info from body and posterior head to VPL Trigeminothalamic tracts bring info from the face to the VPM Organized by where it is coming from in the body and head Different types of mechanosensory input also remain separate and synapse on separate cells of the thalamus
37
Processing at the Perceptual Level
Interpretation of sensory input occurs in the cerebral cortex The ability to identify the sensation depends on the specific location of the target neurons in the sensory cortex not on the nature of the message (all messages are action potentials)
38
Main Aspects of Sensory Perception
Perceptual detection – detecting that a stimulus has occurred and requires summation Magnitude estimation – the ability to detect how intense the stimulus is Spatial discrimination – identifying the site or pattern of the stimulus *Feature abstraction – used to identify a substance that has specific texture or shape *Quality discrimination – the ability to identify submodalities of a sensation (e.g., sweet or sour tastes) *Pattern recognition – ability to recognize patterns in stimuli (e.g., melody, familiar face)
39
Somatosensation Perception
The specific sensation depends on the 2nd and 3rd order neurons The ability to localize the specific location of a stimulus depends on the stimulation of a specific area in the primary somatosensory cortex A sensory “homunculus” is a functional map of the primary somatosensory cortex
40
Somatosensation Perception
The specific sensation depends on the 2nd and 3rd order neurons The ability to localize the specific location of a stimulus depends on the stimulation of a specific area in the primary somatosensory cortex A sensory “homunculus” is a functional map of the primary somatosensory cortex
41
Activation of Pacinian Corpuscle | -shape
* Pacinian Afferents and Corpuscles * Rapidly adapting, more so than Meissner’s corpuscles * Also have a lower response threshold * Super rapidly adapting * Fire, but do not keep firing * About 10-15% of the mechanosensory afferents from the hand * Located deep within the dermis * Look like cross-sections of tree trunks or onions * Concentric circular layers * Layers act as a filter, permitting only transient disturbances at high frequencies * Rings of connective tissue => gives it the special abilities – acting like a filter * Thus can detect a rapid stimulus I think * Receptive fields are large * Well-suited to detect vibrations transmitted by objects * Hitting the hand, leaving the hand * Because of the rings * Believed to be super important for tool use and writing
42
Muscle spindles
slide 42 and before Muscle spindles: stretch receptors that detect changes in the length of the muscle (how much it is stretched) Involved in the sensation of position and movement of the body (proprioception)  Stretch and Speed of Stretch -a type of Proprioceptor (which are mechanoreceptors)
43
Golgi Tendon Organ
A proprioceptor, sensory organ that receives information from the tendon, that senses TENSION. Lift weights --> the golgi tendon organ tells you how much tension the muscle is exerting. *Too much muscle tension --> the golgi tendon organ inhibits the muscle from creating any force (via a reflex arc), thus protecting the you from injuring itself. Decreases activity of alpha motor neuron Because alpha motor neurons do all the “work”
44
is equilibrium part of the somatosensory system
no
45
T/F you can have perception without sensation
FALSE! but, you can have sensation without perception
46
Four Types of Tactile Mechanoreceptors
Merkel, Meissner, Pacinian, Ruffini
47
All of the Tactile Mechanoreceptors have an axon diameter of _______ and conduction of ______, except for ______ which has an axon diameter of _____ and conduction of ______
All of the Tactile Mechanoreceptors have an axon diameter of 6-12um and conduction of 35-70 m/s, except for Merkel Cells which have an axon diameter of 7-11 um and conduction of 40-65 m/s
48
which tactile mechanoreceptors have small receptor fields?
Merkel, Meissner
49
which tactile mechanoreceptors have large receptor fields?
Pacinian, Ruffini
50
Exteroceptors
Respond to stimuli arising OUTSIDE the body Receptors in the skin for touch, pressure, pain, and temperature Most special sense organs
51
can mechanoreceptor be found in visceral locations?
yes ( think), however, proprioceptors (a mechanoreceptor) are found in somatic only
52
T/F the rate of action potentials are proportional to magnitude of depolarization
TRUE
53
** are rapidly adapting or slowly adapting useful for determining stimulus movement
rapidly
54
slowly adapting: def? useful for? ***
sustain their firing in response to the stimulus | • Useful for spatial attributes of stimulus (size, shape)
55
***4 types of general somatosensory receptors
nociceptor, thermoreceptor, mechanoreceptor, chemoreceptors
56
Three types of mechanoreceptors:
Three types of mechanoreceptors: Tactile Receptors, Proprioceptors,and Baroreceptor
57
***Tactile receptors- what to they detect
* Detect membrane distortion * Detect touch, pressure and vibration on skin * Detect hair movement * Detect fine touch * Detect deep pressure * Respond to itch (respond among other to histamine) and light touch (detect changes in shape like bending)
58
which of the tactile mechanoreceptors are slowly adapting
Merkel Cells and Ruffini
59
• Have the highest spatial resolution of all the mechanosensory afferents
Merkel Cells -thus can use for braille reading
60
which of the tactile mechanoreceptors are rapidly adapting
Pacinian Afferents and Meissner Afferents | -Pacinian are MORE rapidly adapting
61
proprioception - receptor type - afferent axon type: - axon diameter: - conduction velocity:
- receptor type: muscle spindle - afferent axon type: 1a,11 - axon diameter: 13-20 um - conduction velocity: 80 -120 m/s
62
proprioception afferent axon type
la,ll
63
***What type of neurons are carrying the information and where are their cell bodies
* The cells are pseudounipolar * The cell bodies of the neurons are in the dorsal root ganglia * The receptors are in the periphery
64
where can the receptors be located for somatosensory?
anywhere on the body
65
which neuron has the smallest axon diameter ?
Pain and temperature neurons- small diameter Sensory afferent- Aδ and C fibers C fibers are the slowest -the unmylenated free nerve enedings = the slowest
66
back vs fingertip receptive fields
Fingertips: densely innervated by cells with small receptive fields --> only need a small difference to detect as two points Back: sparsely innervated by cells with large receptive fields --> need much bigger difference to detect as two points
67
is pain a somatosensory (general sensory sense)?
yes
68
which mechanoreceptor responds to itch?
tactile | Respond to itch (respond among other to histamine) and light touch (detect changes in shape like bending)
69
which of the tactile receptors are located the deepest in the skin?
the pacinian
70
most of the somatosensory receptors are Interoceptors (visceroceptors) T/F
True... I THINK NOT SURE Interoceptors (visceroceptors) Respond to stimuli arising in internal viscera and blood vessels Sensitive to chemical changes, tissue stretch, and temperature changes
71
the collumns of the DCML system
* Leads to parallel columns* - Dorsal column= ascending axons from sensory neurons - Postsynaptic dorsal column projection= axons from projection neurons in spinal cord -synpase in the medulla
72
in the DCML system second order neurons:
• Second-order* neurons in the medulla send their axons towards the somatosensory thalamus
73
where does info for the Trigeminothalamic System cross
• Trigeminothalamic facial fibers decussate within the pons and ascend the brainstem, medially, to the thalamus.
74
decussate
means to cross
75
Somatosensation Perception: specific sensation depends _____ The ability to localize the specific location of a stimulus depends on the stimulation of a specific area in the ____
Somatosensation Perception: specific sensation depends on the 2nd and 3rd order neurons The ability to localize the specific location of a stimulus depends on the stimulation of a specific area in the primary somatosensory cortex
76
trigeminal ganglion: 3 subdivisions
trigeminal ganglion: 3 subdivisions to innervate specific areas of head and face- ophthalamic, maxillary, and mandibular
77
touch neurons: axons and fiber type
Touch neurons- medium diameter axons | Sensory afferent- Aβ fibers
78
what type of receptor mediates touch?
mechanoreceptors
79
what areas of the skin mediate discriminative touch?
those with lots of receptors
80
what is proprioception/what is its main purpose?
mainly in the joints and muscles, tells us where our body is -- muscle stretch and strain
81
how does sensory info come in from the skin?
comes into the spinal cord through the dorsal root ganglia; arrives dorsally and travels up the spinal cord to the dorsal column nuclei
82
what is a unique aspect of sensory cells?
what is a unique aspect of sensory cells? | they are pseudounipolar, so peripheral and central afferent components are continuous
83
how does pain and temp info travel?
how does pain and temp info travel? | synapses more ventrally and then the axons cross, traveling contralaterally
84
labeling the "butterfly" of the spinal cord
-label dorsal vs ventral (drosal = the top = the small part of the butterfly, ventral = the bigger)
85
labeling the "butterfly" of the spinal cord
-label dorsal vs ventral (drosal = the top = the small part of the butterfly, ventral = the bigger)
86
how does mechano/proprio information travel in the spinal cord?
ipsilaterally
87
slow adapting receptor
continues to fire after initial burst of stimulus--constant pressure, and static stimuli
88
where two point discrimination is best developed
Meissner: | -important for efficient control of grip
89
what is observed with distribution of receptors in skin based on size?
what is observed with distribution of receptors in skin based on size? large = fewer per skin area; small = more per skin area
90
how is hairy skin innervated?
by merkel cell afferents and free nerve endings; senses movement of the hairs
91
what is the purpose of deeper touch receptors?
less about sending touch info and more about movement and muscular stretch
92
what leads to transduction?
- mechanosensitive cation channels - disturbance in the layers opens the channels, allows for influx of ions - larger receptor potential with increasing stimulus strength - strong stimulus leads to spike to central nervous system
93
what is the significance of attended stimuli?
what is the significance of attended stimuli? | at the cortex level, attended stimuli are perceived more strongly
94
what differs in the 4 types of axons?
what differs in the 4 types of axons? | different diameters and different myelination
95
what are the A-alpha axons?
what are the A-alpha axons? | fatty, very myelinated, and large; proprioceptors of the skeletal muscle
96
what are the A-beta fibers?
what are the A-beta fibers? | mechanoreceptors of the skin
97
what are the A-delta fibers? | pain, temperature, spinal reflex leads to initial reaction (not super myelinated)
what are the A-delta fibers? | pain, temperature, spinal reflex leads to initial reaction (not super myelinated)
98
what are the C fibers?
temperature, pain, itch; essentially not myelinated, very small; sends info slower
99
what is the path of proprio/mechano info? | alpha and beta fibers enter and travel up the dorsal columns of the spinal cord -- the dorsal-columnar path
what is the path of proprio/mechano info? | alpha and beta fibers enter and travel up the dorsal columns of the spinal cord -- the dorsal-columnar path
100
what is observed with the info as you go up the spinal cord? | *
what is observed with the info as you go up the spinal cord? info from the lower part of the body comes in and situates medially; information from lower extremities arrives medially via the Gracile fascicle, and information from the upper extremities comes in laterally via the cuneate fascicle
101
what happens with info in the lower medulla?
what happens with info in the lower medulla? info synapses here--in the gracile nucleus for lower info, and cuneate nucleus for upper info; info crosses here to the contralateral side, in the brainstem via the medial lemniscus
102
where do axons of the gracile and cuneate nucleus travel?
where do axons of the gracile and cuneate nucleus travel? | to the thalamus
103
what nucleus of the thalamus does the body info go to? the face info?
ventral posterolateral nucleus; ventral posteromedial nucleus
104
where do the tertiary nuclei of the thalamus go to?
somatosensory cortex
105
how does info from the face come in to the thalamus?
via the trigeminal nerve -- synapses in the nucleus of the trigeminal complex, principally on the mesenphalic nucleus and spinal tract nucleus -- synapses, crosses, and then goes to thalamus
106
where do the delta and c fibers come in? what is their path?
where do the delta and c fibers come in? what is their path? | come in and synapse in the dorsal horn, crossing to travel contralaterally; anterolateral/spinothalamic system
107
what is the dorsal horn?
hat is the dorsal horn? it is a region at the rear of the spinal cord that receives inputs from receptors in the skin. The dorsal horn contains interneurons that perform computations that may provide the sense of touch with its rich canvas of effects, from caresses to pokes.
108
how does proprioceptive info come in?
how does proprioceptive info come in? | travels up the spinal cord via the spinocerebellar tract
109
what is the postcentral gyrus?
primary somatosensory cortex; divides into areas
110
what does the posterior parietal cortex process?
what does the posterior parietal cortex process? | somatosensory info
111
what areas of the cortex process somatosensory info? | postcentral gyrus and posterior parietal cortex
postcentral gyrus and posterior parietal cortex
112
what is area 1 of the postcentral gyrus?
cutaneous stimuli/texture
113
what is area 2 of the postcentral gyrus?
size and shape/proprioceptive
114
what is area 3a and 3b of the postcentral gyrus?
proprioceptive and cutaneous obligatory stimuli
115
what is cortical map plasticity?
what is cortical map plasticity? | representation of other fingers will take over cortical area for a lost finger, for example
116
where do motor neurons live?
the ventral horn-- to help mediate reflex arcs
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Impulses generated by the olfactory receptors in the nasal mucosa a. Pass through the substantia nigra b. Pass through the internal capsule c. Are relayed to the olfactory cortex via the hypothalamus d. Pass to the mitral cells and from there directly to the cerebral cortex e. Pass to the mitral cells and from there to the amygdala and then to the cerebral cortex Pass to the mitral cells and from there directly to the cerebral cortex
Impulses generated by the olfactory receptors in the nasal mucosa: Pass to the mitral cells and from there directly to the cerebral cortex
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Damage to which of the following cranial nerves would account for complaints of dizziness, vomiting, and nausea over the past 10 days? The patient also reports that the room appears to be spinning, and has difficulty getting on and off the examination table. a. Optic nerve b. Spinal accessory nerve c. Facial nerve d. Trigeminal nerve e. Vagus nerve f. Vestibulococlear nerve g. Glossopharyngeal nerve
Damage to which of the following cranial nerves would account for complaints of dizziness, vomiting, and nausea over the past 10 days? The patient also reports that the room appears to be spinning, and has difficulty getting on and off the examination table. Vestibulococlear nerve
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15. In addition to projecting to the vestibular nuclei, the vestibular portion of Cranial Nerve VIII projects to the a. Lateral hypothalamus b. Hippocampus c. Flocculonodular lobe of the cerebellum d. Caudal portion of the Nucleus of the Solitary Tract
15. In addition to projecting to the vestibular nuclei, the vestibular portion of Cranial Nerve VIII projects to the Flocculonodular lobe of the cerebellum
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In the cupula, if the stereocilia bend towards the kinocilium a. The hair cell depolarizes b. The hair cell hyperpolarizes c. The amacrine cell inhibits neighboring hair cells d. The tufted cell increases its firing rate
In the cupula, if the stereocilia bend towards the kinocilium The hair cell depolarizes
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Hair follicle receptor
is both rapidly adapting and slowly adapting
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A 70-year-old woman with a recent upper respiratory infection and sinusitis presents with headache, right eye proptosis, diplopia on right lateral gaze, diminished right facial sensation to pinprick, and right eye ptosis and miosis. Where is the most likely lesion? a. Pons b. Medulla c. Midbrain d. Cavernous sinus e. Hypothalamus
A 70-year-old woman with a recent upper respiratory infection and sinusitis presents with headache, right eye proptosis, diplopia on right lateral gaze, diminished right facial sensation to pinprick, and right eye ptosis and miosis. Where is the most likely lesion? Cavernous sinus
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Which type of mechanoreceptor responds best to low-frequency stimuli such as flutter? a. Meissner's corpuscles b. Pacinian corpuscles c. Merkel's disks d. Hair follicle receptors e. Ruffini's corpuscles
Which type of mechanoreceptor responds best to low-frequency stimuli such as flutter? Meissner's corpuscles
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Which of the following best describes an expanded tip tactile receptor found in the dermis of hairy skin that is specialized to detect continuously applied touch sensation? a. Free nerve endings b. Merkel disc c. Pacinian corpuscle d. Ruffini endings
Merkel disc
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The release of neurotransmitter at a chemical synapse in the central nervous system is dependent upon which of the following? a. Synthesis of acetylcholinesterase b. Hyperpolarization of the synaptic terminal c. Opening of ligand-gated ion calcium channels d. Influx of calcium into the presynaptic terminal
Influx of calcium into the presynaptic terminal
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Which of the following is best described as an elongated, encapsulated receptor found in the dermal pegs of glabrous skin that is especially abundant on lips and fingertips? a. Merkel disc b. Free nerve endings c. Meissner corpuscle d. Ruffini endings
Which of the following is best described as an elongated, encapsulated receptor found in the dermal pegs of glabrous skin that is especially abundant on lips and fingertips? Meissner corpuscle
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Which system transmits somatosensory information with the highest degree of temporal and spatial fidelity? a. Anterolateral system b. Dorsal column-medial lemniscal system c. Corticospinal system d. Spinocerebellar system
Dorsal column-medial lemniscal system
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A 10-year-old boy cuts his finger with a pocketknife and immediately applies pressure to the damaged area with his other hand to partially alleviate the pain. Inhibition of pain signals by tactile stimulation of the skin is mediated by which type of afferent neurons from mechanoreceptors? a. a-type A b. ß-type A c. d-type A d. Type C
ß-type A
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Which of these is the primary route for the transmission of signals from nociceptors and thermoreceptors? a. Cuneate fascicle b. Gracile fascicle c. Spinoreticular tract d. Spinothalamic tract
Which of these is the primary route for the transmission of signals from nociceptors and thermoreceptors? Spinothalamic tract
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Which of these types of nerve fibers are found in the motor vagus nucleus? a. Somatic afferent b. Somatic efferent c. Visceral afferent d. Visceral efferent
Visceral efferent
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Your 54-year-old female patient is referred for neurologic consultation because of tongue paralysis. On physical examination, her tongue deviates to the left when she attempts to extend it. The surface on the left side appears wrinkled. A lesion of which of these cranial nerves is most likely to explain these findings? a. Trigeminal (V) b. Hypoglossal (XII) c. Glossopharyngeal (IX) d. Vagus (X)
Glossopharyngeal (IX)
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• The somatosensory system consists of primary, secondary, and tertiary neurons. Sensory receptors housed in the ________ project to secondary neurons of the ______ that decussate and project to the ___ or _____. Tertiary neurons project to the _____ of the ____ lobe, forming a ___XYZ___• A XYZ maps sub-regions of the cortical postcentral gyrus to certain parts of the body.
* The somatosensory system consists of primary, secondary, and tertiary neurons. * Sensory receptors housed in the dorsal root ganglia project to secondary neurons of the spinal cord that decussate and project to the thalamus or cerebellum. * Tertiary neurons project to the postcentral gyrus of the parietal lobe, forming a sensory homunculus. * A sensory homunculus maps sub-regions of the cortical postcentral gyrus to certain parts of the body.
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which part of the primary somatosensory cortex receives the bulk of input from the ventral posterior complex of thalamus?
3b receives bulk of input and serves as a first step in cortical processing
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Somatosensory Association Cortex
5&7 Located posterior to the primary somatosensory cortex and has connection with it Integrates sensory information like temperature and pressure coming from the primary somatosensory cortex. Forms understanding of the stimulus like size, texture, and relationship of parts Ex: putting the hand in the pocket and feeling something. The center integrates previous information to identify objects without seeing them When just using tactile information (cannot see it) Helping to decide whether need to explore an object more to identify it Connected to premotor and motor cortex

Systems Neuroscience (24 decks)

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