Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

PNB 2XB3 (Neuroanatomy) > Lecture 4 + Assignment 4 > Flashcards

Lecture 4 + Assignment 4 Flashcards

1
Q

Spinal segment order

A

Cervical

Thoracic

Lumbar

Sacral

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What do the spinal segments control

SLTC on the diagram

A

Trigeminal nerve
= front of head

Cervical
= behind ear/headband area to fingertips

Thoracic
= chest and underside of arms

Lumbar
= above hips down

Sacral
= butt and bits, the back of legs

look at pic of person touching the floor without bending their knees

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Spinal cord slice components + how is thoracic different

Grey and white matter

A

White matter = myelinated axons

Gray matter = cell bodies and dendrites

Gray matter makes a butterfly with dorsal horns

Thoracic = smaller butterfly so less motor control

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

From fingertip to CNS pathway

DCML and STT

A
  1. Receptor endings

2.a) Abeta mechanosensory afferent fiber
b) Adelta or C axons pain and temperature afferent fibers

  1. Dorsal root ganglion (neuron cluster)

4.a) Abeta to dorsal column
b) Adelta/C CROSSES OVER to ventral spinothalamic tract
=anterolateral

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Three types of somatosensory axons - facts + examples

A
  1. A Beta
    Mechanoreceptive
    touch
    merkel, meissner, pacinian, and ruffini cells
  2. A Delta
    Thermo/nociceptive
    pain, temp.
    free nerve endings
  3. C
    Thermo/nociceptive
    pain, temp., ITCH
    unmyelinated free nerve endings
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Three types of somatosensory axons - speeds + diameters

A

A beta
- 35-75 m/s
- 6-12 nm

A delta
- 5-30 m/s
- 1-5 nm

C
- 0.5-2 m/s
- 0.2-1.5 nm

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

First and second pain

A
  1. touch sensation through Abeta axons
  2. first pain through Adelta axons
  3. second pain through c axons
  • fastest to slowest axon conductance speeds
  • due to myelination and diameter
  • we become aware of sensations when APs reach the cortex
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Why does second pain last much longer

A
  • there is a range of velocities
  • all different “racers”
  • large diameter racers in a “team” (axon type) move faster
  • keep feeling the sensation until all team members have passed the finish line
  • difference between fastest and slowest Adelta speeds still much smaller than for the C axons
  • also gap until first of second pain racers gets there
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Somatosensory tracts

A

DCML
- A beta
- decussates in the caudal medulla (in brain)
- after synapse 1/3 at the dorsal column nuclei

STT
- A delta and C axons
- decussates immediately

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Somatosensory tracts - topography

A

DCML
- more caudal entry = more medial
(longest in the middle)

STT
- more caudal entry = more lateral
(longest on the side)
SWITCH TO OPPOSITE SIDE

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Somatosensory tracts - diagrams

A

Dorsal
(A betas)
- stays on the same side
CTLS SLTC
TLS SLT
LS SL
S S

Ventral
(A deltas and Cs)
- swaps sides immediately
SLTC CTLS
SLT TLS
SL LS
S S

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Picking lesion locations

A
  1. Touch or pain/temperature
    touch = DCML (dorsal)
    p/t = STT (ventral)
  2. Right or left
    DCML: injury right = feel on right
    ipsilateral
    STT: injury right = feel on left
    contralateral
  3. Dermatome location
    CTLSSLTC dorsal

SLTCCTLS ventral

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Central cord syndrome / syringomyelia

A

no pain/temp in bolero region

C4-T1

single lesion in center of spinal cord

  • prevents decussating of second order neurons
  • affects both sides
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Brown-sequard syndrome

A

Lower thoracic injury

Ipsilateral loss of touch sensation

Contralateral loss of pain and temperature sensation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Sensory cell pathway - touch

A

All A beta

  1. Meissner corpuscle
  2. Merkel-cell neurite complex
  3. Ruffini ending
  4. Pacinian corpuscle
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Different sensory cells - mechanoreceptors

receptive field size + respond best to

A

Meissner
- small
- low frequency vibrations (2-50)

Merkel
- small
- static indentation

Ruffini
- large
- skin stretch (dynamic)

Pacinian
- large
- high frequency vibrations (50+ Hz)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Benefit of vibration sensation

A
  • lets us feel textures, slippage, and light vibration of tools
  • low frequency = feeling texture
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Stimulus-response graphs

  • adaption types
A

Slowly adapting
- merkel and ruffini
- first fast dynamic phase, then static phase
|||| | | | | | |

Rapidly adapting
- meissner and pacinian
||||
- only respond initially

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Ellen Lumpkin - merkel mechanotransduction

A

Merkel cells
- mechanically-gated piezo cation channels sensitive to pressure
- cation nonspecific, allow any in once they feel pressure

  • merkel cells release neurotransmitters to Abeta axon
  • similar to neurons bc have channels (piezo and Ca) + release neurotransmitters
20
Q

Ardem Patapoutain

A
  • Nobel prize in physiology or medicine in 2011
  • piezo mechanically gated ion channels
21
Q

Merkel cell mechanotransduction overview

A
  1. Piezos in Abeta open and let in ions
  2. Causes dynamic phase action potentials
  3. Piezos in Merkel open and let in ions
  4. Depolarizes Merkel = opens voltage-gated Ca channels
  5. Neurotransmitter (norepinephrine) released onto Abeta terminal
  6. Causes static phase action potentials
22
Q

Two-point discrimination

A

If points have a faster spike rate in the single middle circle (b) than in the two side circles (a/c):

AP will be felt as one point

23
Q

Two-point discrimination - best and worst spots

A

Best (most accurate)
- shoulder + arm
- torso + leg

Worst (least accurate)
- toes + fingers
- cheek + nose + lip + forehead

24
Q

Goldreich two-point discrimination experiment

A

2POD: two-point orientation discrimination

  • instead of 2v1 points = tactile spatial acuity..

determine orientation

25
Q

Why receptive fields smaller on finger than forearm

A

1 A-beta axon:3-5 merkel cells

Merkel cells more densely packed on fingers

Smaller receptive field contains the same # of cells

26
Q

Thalamus

contains what

A

VPL
- ventral posterior lateral nucleus receives signals from the body axons
- from the dorsal column nuclei

LGN
- lateral geniculate nucleus info from the retina

  • different parts of the nucleus receive info from different parts
27
Q

Primary somatosensory cortex (S1)
+ subdivisions

A

More caudal than central sulcus

In order:
3a - proprioceptive (movement, action, location)

3b - light touch, small receptive fields

1 - light touch, large multi-digit rfs

2 - proprioceptive and light touch

shape: ^
3a/3b by central sulcus
1 at top
2 by posterior parietal complex

28
Q

Homunculus

A
  • coronal slice

most lateral
- tongue
- face
- arm
- trunk
- leg
- foot
- toes
- genitalia

29
Q

Ratunculus

A
  • vibrissae / whiskers
  • barrels in cortex level IV respond to specific whiskers
30
Q

Owl monkey amputation

A
  • somatic sensory cortex
  • third finger amputated
  • second and fourth finger representations take up the brain space after 2 months

= somatosensory plasticity from deafferentiation

31
Q

Phantom limb

A
  • nerve endings still send pain signals although limb is gone
  • feel like the limb is still there
  • especially first few years after amputation
  • phantom limb shrinks over time
32
Q

Sensory cell pathway - temp and pain

A
  1. Free nerve endings
  2. Axons
33
Q

STT pathway

A
  1. Nociceptors and thermoreceptors
  2. Adelta and C axons
  3. Spinothalamic tract
  4. Thalamus / VPL nucleus
  5. Thalamocortical axons
  6. Parietal cortex (S1)
34
Q

Hot vs. cold receptors

A
  • some Abeta heat receptors, some cold
  • both slowly adapt
  • fire more when first made hot (heat receptors)
  • fire more when first made cold (cold receptors)
  • both fire less over time

= adaptation in thermoreceptors

35
Q

How heat receptors work

A
  • ion channels open in response to heat

“transient receptor potential channels”

  • open in response to heat = heat-gated
  • TRPV1 permeable to Na and Ca cations in
  • causes depolarizations and APs
  • allows us to know were getting warm
36
Q

Capsaicin - david julius

A

TRPV1 also responds to capsaicin in spicy peppers

  • lipophilic
  • goes straight through bilayer
  • binds to INTRAcellular TRPV1 channel
  • opens channel and makes us feel heat
37
Q

Menthol - Julius and Payapoutain

A
  • menthol/mint opens cold channels

TRPM8
- also permeable to Na and Ca

38
Q

Referred pain

A
  • you feel pain from an internal organ somewhere else in your skin
  • skin and organ afferent nerves converge onto a single dorsal horn neuron
  • brain infers pain from the place pain is more often felt = skin
39
Q

Gate hypothesis - rub stubbed toe to get rid of pain

A
  • Abeta mechanoreceptor and C fiber nociceptor neurons converge onto dorsal horn projection neuron (second order)
  • between Abeta and dorsal horn is an inhibitory interneuron/local circuit neuron
  • releases GABA or glycine = open Cl channels
  • when mechano activated, inhibits neuron that nociceptor also touches
  • makes slightly less pain bc reduces # of APs
40
Q

Extracellular recording

A

oscilloscope measures voltage changes

audio amplifiers hear APs

  • electrode oustide neuron bc brain inflates and deflates with heartbeats
    = hard to get inside brain that’s bouncing

extracellular graph kinda like upside down graph of AP
- smaller amplitude bc more ions not in a confined space
- Na enters cell so leaves extracellular space and makes it more negative

41
Q

Microelectrode mapping - vernon mountcastle

A
  • mapped different hand segments to parts of the brain

cortical columns
- same receptive field
- vertical

different receptive fields horizontally

42
Q

Cortical columns - order

A

2 mm thick in all mammals

  1. pyramidal cell
  2. local axon collateral
  3. stellate cell
  4. dendrites
  5. descending axon -> output
43
Q

Pyramidal vs. stellate cells

A

Pyramidal cells
- projection neuron axons travel far
- excitatory (glutamate)
- 70% of cortical neurons

Stellate cells
- non-pyramidal
- interneuron
- aka local circuit neuron
- excitatory (glutamate) or inhibitory (GABA)
- 30% of cortical neurons

44
Q

Cortical column inputs and outputs

A
  1. no cell bodies, yes axons and dendrites
    2/3. sends axons to and receives axons from other cortical areas (including the opposite hemisphere)
  2. receives axons from thalamus
  3. sends axons to brainstem and spinal cord
  4. sends axons to thalamus
45
Q

Enkephalinergic inhibitory local circuit interneuron

A

Enkephalin = peptide neurotransmitter

  • synapses axon terminal to axon terminal (instead of to dendrites) of C-fiber

= axo-axonic synapse

  • blocks voltage-gated Ca channels and opens K channels
  • reduces the release of neurotransmitters from the C-fiber onto the dorsal horn projection neuron
46
Q

Pain is personal

A

two ppl might feel the same amounts of pain differently
ex. placebo effect

pain -> amygdala -> raphe nuclei -> brain stem enkephalinergic interneuron APs

  • bc linked to amygdala activity activating enkephalin
  • goes to raphe nucleus

no enkephalin = no placebo

PNB 2XB3 (Neuroanatomy) (5 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions