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PNB 2XB3 Midterm 2 Review Questions and Answers | Latest Update 2024/2025 $12.49   Add to cart

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PNB 2XB3 Midterm 2 Review Questions and Answers | Latest Update 2024/2025

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  • Course
  • PNB 2XB3
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  • PNB 2XB3

4 Sections of the spinal cord ~~> 1. Cervical 2. Thoracic 3. Lumbar 4. Sacral A beta Fibers ~~> Large sensory fibers involved in rapidly transmitting sensation. Responds to touch (around 50 m/s) A delta Fibers ~~> Slower fiber that responds to sharp pain ( around 10m/s) C ...

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  • September 20, 2024
  • 33
  • 2024/2025
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  • PNB 2XB3
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1 | P a g e | © copyright 2024/2025 | Grade A+


PNB 2XB3 Midterm 2 Review Questions
and Answers | Latest Update
2024/2025
4 Sections of the spinal cord

✓ ~~> 1. Cervical

✓ 2. Thoracic

✓ 3. Lumbar

✓ 4. Sacral



A beta Fibers

✓ ~~> Large sensory fibers involved in rapidly transmitting sensation.

Responds to touch

(around 50 m/s)



A delta Fibers

✓ ~~> Slower fiber that responds to sharp pain ( around 10m/s)



C fibers

✓ ~~> Slow fiber that is associated with dull pain (around 1m/2s)



Dorsal Column Medial Lemniscus Pathway




Master01 | September, 2024/2025 | Latest update

, 2 | P a g e | © copyright 2024/2025 | Grade A+

✓ ~~> Pathway that responds to light touch

A delta axons go up lumbar and cervical spinal cord, then the dorsal column

nuclei, then medial lemniscus in the caudal medulla (base of brain).

From there to pons, midbrain, thalamus and eventually parietal cortex using

thalamocortical axons.

Decussates at caudal medulla.



Spinothalamic Tract

✓ ~~> Pathway that responds to painful touch. (A delta and C axons)

Travels in ventral matter of the spinal cord. Decussates immediately.



Brown-Sequard Syndrome

✓ ~~> Damage to half of the spinal cord.

Results in loss of touch on the ipsilateral side, and on the contralateral side, no

pain sensations.

Upper body still has normal sensation.



4 Types of Touch Receptors

✓ ~~> Meissner corpuscle, Merkel cell-neurite complex, Ruffini ending,

Pacinian corpuscle.



Meissner Receptors




Master01 | September, 2024/2025 | Latest update

, 3 | P a g e | © copyright 2024/2025 | Grade A+

✓ ~~> Small receptive field size

Responds best to low frequency vibration (2 to 50Hz)

Located near surface (around 1mm deep into the skin)



Merkel Receptors

✓ ~~> Small receptive field size.

Responds best to static indentation (pressure

Located near surface (around 1mm deep into the skin)



Ruffini Receptors

✓ ~~> Large receptive field size

Responds best to skin stretch

Located deeper in skin



Pacinian Receptors

✓ ~~> Large receptive field size

Responds best to high frequency vibrations

(greater than 50Hz)



What does the sensation of vibrations help us do?




Master01 | September, 2024/2025 | Latest update

, 4 | P a g e | © copyright 2024/2025 | Grade A+

✓ ~~> Allows us to perceive the texture of materials, the "slippage"

between the skin and grasped object and the small vibrations of tools.

EX Detecting change in amplitude when you're running you fingers across an

etched design.



Stimulus Response Spike Train

✓ ~~> Merkel and Ruffini cells have an onset response (dynamic phase)

and an ongoing response (static phase)

Meissner and Pacinian cells respond to the first part of the stimulus



Merkel Cells and Mechanotransduction

✓ ~~> When skin is presed:

1) Mechanically-gated ion channels in the A beta membrane open, letting in

ions (Na)

2) This causes the first ("dynamic phase") action potential

3) Mechanically-gated ion channels in the Merkel cell membrane also open,

letting in ions (Na)

4) This depolarizes the Merkel cell and results in the opening of voltage gated

Ca channels

5) As a result, a neurotransmitter (norepinephrine) is released onto the A beta

axon terminal, which contains transmitter receptors

6) This causes the second ("static") action potentials




Master01 | September, 2024/2025 | Latest update

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