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FIS3701 – EXAM NOTES ALL QUESTIONS ARE ANSWERED FROM PAST EXAMS
QUESTION 1
1.1 A 28-year-old man was seen by a neurologist because he had experienced prolonged episodes of tingling and
numbness in his right arm. He underwent a neurologic exam to evaluate the integrity of his sensory nervous system,
including a measure of the ability to discern that two-pointed objects touching the skin are indeed two distinct points.
What does this two-point discrimination test measure and what central nervous system pathway is being evaluated?
(3)
A. Nociceptive sensitivity and the spinothalamic pathway
B. Stereognosis and medial lemniscal pathway
C. Stereognosis and spinoreticular pathway
D. Tactile acuity and the dorsal column pathway
E. Tactile acuity and the spinothalamic pathway
ANSWER
• Option " D"
• Tactile acuity and the dorsal column pathway
• Two Point Discrimination Test
- It is ability to discern that 2 nearby objects touching the skin are truly two distinct points
- Ask patient to close eyes. Clinician touches at two different point at same time or alternatively like arms, legs, fingers
toes . Results were noted
- After stimulus with help of Tactile receptors sensation carries to the dorsal column nucleus by primary afferent fibers
and then to Thalamus
- Then processing occurs at somatosensory cortex of left hemisphere of brain
- Motor sensation send to Effectors
1.2 A resident in internal medicine is asked to give a presentation on referred pain to second year physiology students.
What is the definition of referred pain and what is a potential basis for it? (3)
A. Referred pain is pain that originates within a visceral organ but is sensed as pain arising from a somatic structure.
It may be due to the convergence of somatic and visceral nociceptive fibers on the same neurons in the dorsal
horn that project to the thalamus and then to the somatosensory cortex.
B. Referred pain is pain that is referred to a body part that has been removed. It may result from the reorganization
of the somatosensory cortex after the sensory input is cut off.
C. Referred pain is poorly localized pain from a visceral structure that is relayed to the central nervous system by
branches of sensory neurons from the nearby skin or skeletal muscle. It may occur because the same nociceptive
fiber transmits information from visceral and somatic structures to the spinal cord dorsal horn.
D. Referred pain resembles “fast pain” produced by noxious stimulation of the skin since it also originates from
unmyelinated C fibers. It may result from the activation of sympathetic nerves to the visceral organ causing the
release of chemicals into the circulation that sensitize nociceptors in the skin and skeletal muscle.
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ANSWER
Option A
Referred pain is pain that originates within a visceral organ but is sensed as pain arising from a somatic structure. It may
be due to the convergence of somatic and visceral nociceptive fibers on the same neurons in the dorsal horn that project
to the thalamus and then to the somatosensory cortex
1.3 A 50-year-old woman with uncontrolled diabetes was undergoing vibratory sensibility testing by applying a vibrating
(128-Hz) tuning fork to the skin on the fingertip, tip of the toe, and bony prominences of the toes. What kind of receptors
are activated by this stimulus? (3)
A. Meissner corpuscles
B. Merkel cells
C. Pacinian corpuscles
D. Ruffini corpuscles
E. Mechanical nociceptors
ANSWER
• Option C
• Majorly Pacinian corpuscles are activated first. Pacinian Corpuscles are found in the muscle and joint (deep dermis)
and their function is to detect gross pressure and high frequency vibration from 50-1000hz.
• Meissner corpuscles are responsible for detecting low frequency vibration from 10hz to 50hz. They are found in
the upper dermis and fingertip
• While Merkel cells detect only light touch.
• Ruffini corpuscles detect stretch, deformation with joint and warmth and high frequency vibration
• Mechanical nociceptors respond to excess pressure or mechanical deformation only not to vibrations.
• In this patient considering uncontrolled diabetes majorly Pacinian corpuscles will be activated as it can detect
128hz frequency
1.4 A medical student is working in a laboratory that studies modulation of transmission in nociceptive pathways. She
is particularly interested in studying neurons in the brainstem that project to the spinal cord and release
neurotransmitters that inhibit nociceptive transmission in the dorsal horn. What medullary regions is she likely to study
and what neurotransmitters do they release in the dorsal horn? (3)
A. Periaqueductal gray (endorphin) and rostral ventromedial medulla (serotonin)
B. Nucleus raphe magnus (serotonin) and rostral ventromedial medulla (norepinephrine)
C. Periaqueductal gray (enkephalin) and nucleus raphe magnus (serotonin)
D. Locus coeruleus(endorphin) and rostral ventromedial medulla (serotonin)
E. Periaqueductal gray (dynorphin) and rostral ventromedial medulla (norepinephrine)
ANSWER
• Given option c is the correct answer. This is because the medullary regions which are associated with pain
modulation are known as the periaqueductal grey (PAG) and nucleus raphe magnus region. Also, the
neurotransmitter associated with the inhibition of the nociceptive transmission is enkephalin released by the
PAG area, and serotonin released by the raphe magnus.
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• Therefore, it can be concluded that the given option c is the correct answer.
• The explanation for the incorrect answers:
• Given option a is the incorrect answer. This is because the endorphin is not released by the PAG area rather the
PAG area is stimulated by the endorphin.
• Given option b is the incorrect answer. This is because the rostral ventromedial medulla (RVM) does not release
norepinephrine in the dorsal horn, rather nor epinephrine is released by the locus coeruleus.
• Given option d is the incorrect answer. This is because the pituitary gland releases the neurotransmitter
endorphin and not the locus coeruleus.
• Given option e is the incorrect answer. This is because the neurotransmitter norepinephrine is released by the
locus coeruleus and not by the RVM area
1.5 A 62-year-old man had a gunshot wound to the left side of his head that damaged the top portion of the lateral
postcentral gyrus very close to the midline of the brain (posterior portion of the paracentral lobule). What sensory
modalities will likely be compromised by his injury? (3)
A. He will lose the sense of touch and the discriminative aspect of pain over his left hand and wrist.
B. He will lose the sense of touch, pressure, and vibration over his right forearm.
C. He will lose the sense of touch and the discriminative aspect of pain over his right leg and hip.
D. He will lose the sense of touch over his left leg and the discriminative aspect of pain over his right leg.
E. He will lose the sense of touch, pressure, and vibration but maintain the discriminative aspect of pain over his
right leg.
ANSWER
• C. He will lose the sense of touch and the discriminative aspect of pain over his right leg and hip.
• Postcentral gyrus is the main sensory receptive area for the sensation of touch. Proprioception, vibration, touch and two- point
discrimination are included in the functions of post central gyrus. So, when a person got an injury at this area, we will observe
loss of proprioception, vibration, touch and two-point discrimination. Here in this case this person got an injury over left side so,
this person will have sensory impairments to the trunk and extremities of his right side.
QUESTION 2
2.1 Briefly describe the term modality. (5)
A modality is the way or mode in which something exists or is done. You might often see it used with reference to
diagnostic modality, which is the way in which a disease or illness is diagnosed by a doctor.
Modality shares its root with the word mode, meaning "the way in which something happens or is experienced." A
sensory modality is a way of sensing, like vision or hearing. Modality in someone's voice gives a sense of the person's
mood. In logic, modality has to do with whether a proposition is necessary, possible, or impossible. In general, a
modality is a particular way in which something exists.
Modality is the type of behavior, expression or way of life that belongs to a particular person or group of people. An
example of modality is the type of behavior a doctor uses to treat a very ill patient
a particular mode in which something exists or is experienced or expressed.
2.2 Knowing the impact of acidosis and alkalosis on synaptic transmission, critically analyze the following statement:
“Hyperventilation may lead to seizures in epileptic patients. (5)
