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Organ Systems lll kt's > Somatosensory Part 2.0 > Flashcards

Somatosensory Part 2.0 Flashcards

1
Q

How many layers are there in the neocortex?

A

six layers

  • receive incoming info and form meaningful spatiotemporal patterns that are projected to other cortical areas, to limbic, brain stem and spinal cord
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2
Q

What are the major input receiving cells called of the neocortex? In what layer?
receive sensory input from?

A

Stellate cells in layer lV

  • receive sensory input from the thalamus
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3
Q

What are the major output cells called of the neocortex? In what layer? to where?

A

Pyramidal Cells in layer V project info to other regions of CNS.

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4
Q

What do interneurons do in the neocortex?

A

generate excitatory and inhibitory patterns of neural activity

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5
Q

What are Brodmann’s areas?

A

area of cortex that have characteristic cells that are histologically distinguishable. Ea area is numbered.

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6
Q

What does fMRI measure?

A

you can see brain activity:

  • hydrogen ions - magnetic gradients form the overall map
  • BOLD - blood oxygen level detection - MEASURES NEURALLY RELATED BLOOD FLOW (increase in neuronal activity increases demand for oxygen -> increase in blood flow)
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7
Q

Thalamus

where?

in what?

axons to where?

A

pair of oval shaped clusters in nuclei in the diencephalon

  • lie on ea side of third ventricle
  • project axons from ea nucleus to all areas of cortex (sensory, motor, or integrated neural info)
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8
Q

Extra Info for Clarification about Thalamus:

A

Thalamus divided into Anterior, Medial, and Lateral
Anterior - Anterior Nucleus
Medial - Medial Dorsal Nucleus and other small midline nuclei
Lateral - Ventral and Dorsal tiers
> Ventral - ventral lateral VL, ventral posterior VP, ventral anterior VA
VP - Ventral Posteromedial, VPM; Ventral Posterolateral, VPL
> Dorsal - Pulvinar, Lateral Posterior LP, Lateral Dorsal LD

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9
Q

VPL (body) and VPM (head) of thalamus project to?

A

Somatosensory Cortex, SS

remember, Anterolateral Pathway’s Neospinothalamic Tract (localization of sensation) projects to lateral thalamus and then somatosensory cortex (part of second to third order neurons)

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10
Q

Where on the cortex is the Sl, primary somatosensory cortex?

A

postcentral gyrus

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11
Q

VPL receives input from?

A

Dorsal Column-lemniscal and Anterolateral Pathways

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12
Q

VPM receives input from?

A

the head via Trigeminal Nerve

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13
Q

What do the Sl and Sll do?

A

elaborate and contextualize sensory info into meaningful experiences

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14
Q

What are Cortical Columns?

A

neurons w similar sensory receptive properties, i.e. modality and receptive fields: clustered together in a column.

  • touch, pain, proprioception project to diff areas of cortex
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15
Q

Somatotopy

A

The topographic association of positional relationships of receptors in the body through respective nerve fibers to their terminal distribution in specific functional areas of the cerebral cortex

> occurs in spinal cord, brain stem, thalamus, cerebral cortex

> reminds me of a microcosm!

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16
Q

Homunculus

A

contiguous areas of the body represented within cortex in proportion to density of sensory receptors in that area of the body - so mouth and tongue look ridiculously huge along with hands

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17
Q

Cortical Plasticity

A

cortical sensory representation changes w experience and learning

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18
Q

Cortical column neurons respond primarily to one specific area of the body, but inputs from neighboring areas of the body surface also project to the same columns WITHOUT eliciting activity. What are these connections called?

A

latent

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19
Q

In the CNS, how are RF’s more finely differentiated in order to localize the stimulus?

A

lateral inhibition

  • inhibition of pathways between different RF’s
20
Q

Lateral Inhibition

A

neural mechanism in cortex, thalamus, and dorsal column nuclei that enhances the difference between somatosensory RF’s.

21
Q

Dorsal Column Nuclei, DCN, neurons are stimulated by sensory neurons from the _____ of a RF.

A

center

therefore, central stimulation of the RF generates a positive response

22
Q

Inhibitory interneurons within the DCN inhibit sensory neurons in the ______ zone of a RF.

A

peripheral

therefore, peripheral stimulation of the RF generates a negative response

LATERAL INHIBITION

23
Q

A single sensory neuron will branch and activate several local DCN neurons, the response ______ the further away from the source of the stimulus one goes.

A

weakening

this is why we need lateral inhibition

24
Q

Inhibitory interneurons, when stimulated, tend to inhibit neighboring DCN neurons. The central region of activation is _____, while the neighboring region is _____.

A

enhanced

inhibited

25
Q

Two Point Discrimination

what is it?

what does it test/measure integrity of?

A

ability to discriminate between separate but simultaneous pin-pricks to the skin.

measures integrity of the dorsal column-lemniscal system

  • density of sensory receptors
  • lateral inhibition in CNS
26
Q

Syphilis reduces 2 point discrimination. why?

A

dorsal column degeneration

27
Q

During tactile exploration, afferent input from upper limb is modulated by Sl and the motor cortex (above to below).

This is an example of?

What’s the point?

A

Cortical regulation of lateral inhibition in dorsal column nuclei.

  • select certain inputs relevant to the movements
  • provide input to assure adequate frequency and duration discrimination for tactile and proprioceptive info.
28
Q

Somatosensory perception depends on ______.

A

MOVEMENT!

  • required for discrimination of texture complex spatiotemporal patterns.
  • altho, there isn’t loss of absolute sense of touch
29
Q

VPL receives input from Dorsal Column-Lemniscal and Anterolateral Pathways, then projects to several regions of _____. What Brodmann areas encode for Proprioception? for SA and RA cutaneous receptors?

A

Sl, primary somatosensory cortex

Proprioception: Area 3a

SA and RA cutaneous receptors: Area 3b

30
Q

Tactile perception of object size and shape requires what kind of info?

A

cutaneous and proprioceptive from joints, muscles, and skin stretch.

31
Q

Information from two systems to thalamus (VPL), then to 3a & 3b of Sl, then to areas 1 & 2 (of Sl) where things get more abstract! THEN, to where?

A

Area 5! (dorsal stream) OR S2! (ventral stream)

  • area 5 is no longer in the postcentral gyrus, but now the postcentral sulcus.
  • area 5: somatosensory + visual inputs
32
Q

3b –> area 1 —> area 2 —> area 5

What happens to RF’s along the way?

A

RF’s enlarge w ea step up the cortical hierarchy.

Larger areas are then integrated into meaningful wholes.

33
Q

Ventral Stream: Sl projects to?

What does it do?

A

Sll, Secondary Somatosensory Cortex bilaterally

> form processing “what is it?” develops internal 3D picture

34
Q

Dorsal Stream: Sl projects to?

What does it do?

A

Posterior Parietal Cortex, PPC (areas 5,7)

> multisensory integration, directing attention and interacting w motor cortex in frontal lobe

“where? how? do I get these 57 cupcakes on the top of my head (dorsal)?!”

“oh no! I am a big cupcake!”

  • ego-centric space integrating touch, proprioception, & vision
35
Q

Sl -> Sll
aka
Ventral Stream

Sll responses depend on what?

A

behavioral context or motivational state

> Sll conveys info to and from hippocampus and amygdala of limbic system —- forms memories

36
Q

Sl -> PPC
aka
Dorsal Stream (5,7)

Receives info directly via? indirectly via?

A

directly via arcuate fibers

indirectly via thalamus

37
Q

Astereognosis

A

Dysfunction in Association Cortex

inability to identify an object by touch

38
Q

Neglect Syndrome

A

Dysfunction in Association Cortex

lesions in Right inferior parietal lobe - a cortical region which integrates somatosensory, visual, and auditory info -
> loss of the left side of the body and visual fields

39
Q

Somatosensory Summary: Bottom Up input

A

Sl neurons receive input from sensory receptors. PPC receives integrated info from Sl, Sll, plus visual and auditory association cortices.

40
Q

Somatosensory Summary: Top Down input

A

Sl neurons receive feedback from not only posterior parietal neurons (forms a backdrop to “make sense”) that respond to both somatosensory and visual info, but also from motor cortices.

41
Q

How is short term memory formed in Sl?

A

Sl neural activity persists after sensory stimulus has stopped - a very short period of time where we are aware of something.

42
Q

Remember the 3 levels of integration associated with Sl and Sll?

Somatic Sensation
Somatic Perception
Somatic Representation

What is a Phantom Limb?

Caused by?

A

Dissociation of somatorepresentation (one knows abstractly that their limb is gone) and somatoperception (but limb still feels present).

> denervation of limb cortex unmasks latent sensory pathways from contiguous areas of body

43
Q

Phantom Limb pain. How?

A

Efferent pathways from hand area of sensory and motor cortex maintains perception of hand, especially in contracted postures

44
Q

What does the Rubber Hand Illusion test?

A

Tests body ownership. matching of multisensory processing.

  • sense of self involves both a sense of agency and body-ownership
  • synchronous stimulation of unseen real and seen rubber hand causes rubber hand to be attributed to ne’s own body.
45
Q

What is Delusional Parasitosis?

A

delusion of being infested w bugs or parasites.

tactile hallucinations.

Organ Systems lll kt's (5 decks)

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