T7.1: Somatosensory Flashcards
A patient comes into the clinic he has lost feeling from his umbilicus to this toes. After examination it is also found that he has no sense of pain in his contralateral side from his lost sense of touch about two levels below the lost sensation of touch. Why is the lost of pain lower than his lost of touch?
A. Antero Lateral tract
B. Spinothalamic tract
C. Medial Lemniscus tract
D. Lissauer’s Tract
RFA
Ans. D Lissauer’s Tract- is the secondary pain pathway and crosses over at the level of the spinal cord but is also able to rise up to two spinal segments before it desiccates.
A & B are both names for the primary pain pathway
C is a touch pathway
Large receptive field that is fast adapting is what? A. Pacinian Corpuscle B. Meisner’s Corpuscle C. Merkle’s disk D. Ruffni endings
RFA
Ans. A
B- Small, fast
C. Small,Slow
D. Large, Slow
The fibers of touch are? A. IA B. AB C. AG D. C
ANS:B AB fibers are the fiber of touch
IA are the large fibers and sensory afferent fibers of muscles
AG and C are the smallest fibers are associated with pain and temp
Which of the following combinations is correct?
A. A-Delta Fibers: 39 m/s B. A-Beta Fibers: 39 m/s C. A-Alpha Fibers: 70 m/s D. C Fibers: 3 m/s E. A-Delta Fibers: 3 m/s
FA
B. A-Beta Fibers range from 36-72m/s are used in proprioception, touch, and vibration
A-Alpha run from 72m/s to 120m/s
A-Delta run from 4m/s to 36/ms
C-Fibers run from 0.4 m/s to 2m/s
A man who has developed brown-sqaudward syndrome with localization of the lesion at the T1 Spinal level. At what dermatome level will be the first to sense crude touch contra laterally above the area of parathesia?
A. C8 B. T1 C. T2 D. T3 E. T4
FA
C. T2, because the anterolateral tract crosses at an angle, it only begins to be effected at 2 spinal levels below the lesion.
On the OSCE exam, you are handed a 256 Hz tuning fork to perform Rinne and Weber’s tests. Unfortunately, you read the prompt wrong and begin testing the patient for vibration sensation. Which receptors are being stimulated as you touch the vibrating fork to the patients hand? (MG)
A. Ruffini’s
B. Pacinian
C. Merkel’s
D. Meissner
B. Pacinian corpuscles are optimized for vibrations between 200-300 Hz
A patient presents with a right half hemisection lesion of the spinal cord. Describe his contralateral pain and temperature sensation BELOW the lesion. (mm)
A hemisection lesion is a brown sequard lesion. The pt will feel pain and temp contralateral up to two levels below the lesion because of Lissauers tract. After two levels below the pain and temp on the contralateral side will be lost.
You anal(yzed) your patients MRI and discovered a fluid filled cyst blocking the anterior white commissure. Touch/vibration will be _________ ipsilaterally and pain/temp will be Lost _________. (mm)
You anal(yzed) your patients MRI and discovered a fluid filled cyst blocking the anterior white commissure. Touch/vibration will be PRESERVED ipsilaterally (and contra) and pain/temp will be Lost BILATERALLY
Pt has syringomyelia
A weird brown guy named Ahmed likes S&M … mostly the M part. When his master Ryan spanks him his brain activates a descending analgesic pathway. This pathway received the input from which part of the brain? (mm)
A) Internal Capsule B) Reticular Formation C) Amygdala D) Medulla E) Spinothalamic Tract
Answer = B
When pain travels to the cortex via the internal capsule there are collateral pathways leading to the reticular formation which sends input to the descending analgesic pathways and for emotive pain.
Ryan and Adam were engaged in gay sex, when suddenly they accidentally crossed swords. Just like in Ghostbusters™, resulted in a large explosion. The surrounding area became completely obliterated and both boys became completely blind. They had to learn braille, a tactile writing system used by people who are visually impaired. Which cutaneous mechanoreceptor would be involved in reading braille with their fingers?
A. Merkels disks and Meissners corpuscles B/ Pacinian corpuscles C. Ruffini's endings D. Hair follicle receptor E. Meissners corpuscles F. Thermoreceptors G. Nociceptors
AA
CORRECT ANSWER = A. Merkel’s disks and Meissner’s corpuscles. These two receptors are used in conjunction for fine, discriminatory touch.
Pacinian corpuscles are used for deep pressure sensations. Senses high vibration frequencies around ~200-300 Hz
Ruffini’s endings are used for skin stretch.
(Protip: think RUFF SEX –> stretches things out, for Ruffini’s endings.
Meissner’s corpuscle alone senses vibration at lower frequencys ~50 Hz
Thermoreceptors are used for temperature.
Nociceptors are used for pain.
What is the correct order of cutaneous mechanoreceptor receptive field from smallest to largest?
A. Ruffini’s endings -> Pacinian corpuscle -> Meissner’s corpuscle -> Merkel’s disc
B. Merkel’s disc -> Pacinian corpuscle -> Meissner’s corpuscle -> Ruffini’s ending
C. Merkel’s disc -> Meissner’s corpuscle -> Pacinian corpuscle -> Ruffini’s ending
D. Ruffini’s endings -> Meissner’s corpuscle -> Pacinian corpuscle -> Merkel’s disc
AA
CORRECT ANSWER = C. Merkel’s disc -> Meissner’s corpuscle -> Pacinian corpuscle -> Ruffini’s ending
Remember, smaller receptive field means higher spatial resolution. So it makes sense that Merkel’s disc and Meissner’s corpuscle would have the smallest receptive field.
Answer choice B is largest to smallest.
Cutaneous mechanoreceptors change their response to repeated presentation of a stimulus by either rapidly adapting or slowly adapting. Which of the following options is paired correctly?
A. Meissner’s corpuscle: small receptive field size and rapidly adapting.
B. Pacinian corpuscle: large receptive field and slowly adapting.
C. Merkel’s disk: large receptive field and slowly adapting.
D. Ruffini’s ending: large receptive field and rapidly adapting.
E. Ruffini’s ending: small receptive field and slowly adapting.
AA.
ANSWER = A. Meissner’s corpuscle: small receptive field size and rapidly adapting.
Meissner’s corpuscle and Merkel’s disk should be both small receptive field, as they are for fine touch which requires high spatial resolution.
So automatically you should be able to throw away option C.
Pacinian corpuscle and Ruffini’s endings both have large receptive fields. So option E is incorrect.
However Pacinian corpuscle is RAPIDLY adapting, while Ruffini’s ending is SLOWLY adapting. So options B and D are both incorrect.
You diagnose your patient with Brown Sequard. At the level of the lesion, which of the following are lost? (Choose all that apply) (MG)
A. Ipsilateral touch, vibration, proprioception
B. Ipsilateral pain, temperature
C. Contralateral touch, vibration, proprioception
D. Contralateral pain, temperature
A. Ipsilateral touch, vibration, proprioception
B. Ipsilateral pain, temperature
The lissauer’s tract deals with crude touch and pain through which fibers (choose all that apply)?
A. A-beta
B. A-delta
C. Gamma fibers
D. C-fibers
B. A-delta
D. C-fibers
