Case 19 Questions 41-57

Scroll Down

Enjoy working thorugh the following questions. We hope they aid your learning. If you have any issues or feedback, please email [email protected]

Question 41

Which of the following structures is the origin of the corticobulbar upper motor neurons?

  1. Thalamus
  2. Basal ganglia
  3. Red nucleus/li>
  4. Primary motor cortex
  5. Posterior parietal cortex

The correct answer is option d, Primary motor cortex

Majority of upper motor neurons originate from primary motor cortex. Exceptions are indirect pathway motor neurons that perform special motor functions e.g. reticulospinal, rubrospinal tracts

Question 42

Which of these cerebellar regions are involved in the planning and initiation of movements?

  1. Neocerebellum
  2. Anterior lobe
  3. Flocculonodular lobe
  4. Vestibulo-cerebellum
  5. Spinocerebellum

The correct answer is option a, Neocerebellum

Neocerebellum is involved in initiation and planning of movements

Vestibulocerebellum aka flocculonodular lobe : involved in posture and balance. Spinocerebellum : involved in coordination of ongoing movements. Anterior lobe : unconscious proprioception.

Question 43

Which of the following features point towards a cerebellar lesion?

  1. A high stepping gait
  2. Lid lag
  3. Dysarthria
  4. Resting tremor
  5. Stooped posture

The correct answer is option c, Dysarthria

Remember DANISH to identify cerebellar deficits. Dysarthric pattern of slurred speech is classical for cerebellar dysfunction. While it may contribute towards postural instability as a subset of loss of balance, it is not a key defining feature of cerebellar dysfunction

Question 44

60yo male comes into ED with a burn on their right hand. He says this is from accidentally touching a hot plate from the oven for a prolonged period without realising that it was hot. On examination, he is unable to feel vibratory sensation in his left hand.

Which of the following is most likely to be true for this patient :

  1. Lesion in the dorsal column at the level of C1
  2. Lesion in the precentral gyrus of the left cerebral hemisphere
  3. Lesion on the right side of the spinal cord at the level of C1
  4. Lesion on the left side of the spinal cord at the level of C1
  5. Lesion on the left side of the spinal cord at the level of T6

The correct answer is option d, Lesion on the left side of the spinal cord at the level of C1

Hemisection of spinal cord will result in ipsilateral interference in DCML pathway, and contralateral interference in spinothalamic pathway. This is due to the location of decussation of each of these pathways. Lesion at C1 is above the nerve roots for the hands while T6 wouldnt affect the hands. Precentral gyrus is the primary motor cortex.

Question 45

Which of the following best describe the process of conversion of a sensory stimulus into neural impulses?

  1. Sensory adaption
  2. Sensory perception
  3. Sensory afferent activity
  4. Sensory transduction
  5. Sensation

The correct answer is option d, Sensory transduction

Transduction is the process of converting stimuli to action potential

Question 46

Which of the following respond to changes in fine touch and pressure?

  1. Pacinian corpuscles
  2. Meissner corpuscles
  3. Baroreceptors
  4. Free nerve endings
  5. Krause end bulb

The correct answer is option b, Meissner corpuscles

Meissner corpuscles respond to fine touch and pressure. Rapidly adapting encapsulated neurons which are plentiful in fingertips, along with merkels disks. Pacinian corpuscles respond to deep pressure due to their location in the dermis. Free nerve endings may respond to light touch, however majority of them are comprised of nociceptors

Question 47

A patient comes to the GP and complains of back pain. On examination, there is weakened extension in the big toe. Which of the following statements are true:

  1. L5 nerve root supplies the flexor hallucis longus which is responsible for big toe extension
  2. S1 nerve root supplies the flexor hallucis longus which is responsible for big toe extension
  3. L4 nerve root supplies the extensor hallucis longus which is responsible for big toe extension
  4. S1 nerve root supplies the extensor hallucis longus which is responsible for big toe extension
  5. L5 nerve root supplies the extensor hallucis longus which is responsible for big toe extension

The correct answer is option e, L5 nerve root supplies the extensor hallucis longus which is responsible for big toe extension

The others are false. Remember the Myotome map

Question 48

Which of the following is true in regards to sensory receptors in the skin?

  1. Merkel receptors are rapid-adapting mechanoreceptors that fire to continuous stretch
  2. Merkel receptors are slow-adapting mechanoreceptors that fire to continuous stretch
  3. Ruffini corpuscles are slow-adapting mechanoreceptors that fire to vibration
  4. Pacinian corpuscles are rapid-adapting mechanoreceptors that fire to vibration
  5. Pacinian corpuscles are slow-adapting mechanoreceptors that fire to vibration

The correct answer is option d, Pacinian corpuscles are rapid-adapting mechanoreceptors that fire to vibration

option a -> Correct would be: Merkel receptors are SLOW-adapting mechanoreceptors that fire to touch- PRESSURE.
option b -> Correct would be: Merkel receptors are slow-adapting mechanoreceptors that fire to touch- PRESSURE.
option c -> Correct would be: Ruffini corpuscles are slow-adapting mechanoreceptors that fire to STRETCH.
option d -> Correct would be: Pacinian corpuscles are RAPID-adapting mechanoreceptors that fire to vibration.

Question 49

A 32 year-old man is stabbed in the back. On examination you note a complete loss of sensation at the level of the nipple. Which dermatome is responsible for this?

  1. T1
  2. T2
  3. T3
  4. T4
  5. T5

The correct answer is option d, T4

Options A, B, C, E are incorrect

Question 50

The dorsal column-medial lemniscus pathway transmits which sensory modality?

  1. Temperature
  2. Pain
  3. Crude touch
  4. Proprioception
  5. None of the above

The correct answer is option c, Proprioception

Proprioception -> Dorsal column-medial lemniscus pathway
Temperature -> Anterior Spinothalamic pathway
Pain -> Anterior Spinothalamic pathway
Crude touch -> Lateral spinothalamic pathway
None of the above -> Distractor

Question 51

A 20-year-old man was involved in a car accident where he sustained a hemisection of the left side of the spinal cord at the level of T2.

Select the set of symptoms that would be produced from such injury:

  1. Weakness, loss of pain and loss of light touch sensation on the left side
  2. Weakness on the right side and loss of light touch sensation and pain on the left side
  3. Weakness and loss of pain on the left side and loss of light touch sensation on the right side
  4. Weakness and loss of light touch sensation on the left side and loss of pain on the right side
  5. Weakness, loss of pain and loss of light touch sensation on the right side

The correct answer is option d, Weakness and loss of light touch sensation on the left side and loss of pain on the right side

A hemisection of the spinal cord causes Brown-Sequard syndrome. Since the hemisection is on the left side it produces weakness and loss of light touch sensation on the LEFT side AND loss of pain on the right side

Question 52

Which tract carries subconscious proprioceptive information?

  1. Dorsal-column medial lemniscus
  2. Spinocerebellar tracts
  3. Anterior spinothalamic tract
  4. Lateral spinothalamic tract
  5. None of the above

The correct answer is option b, Spinocerebellar tracts

Dorsal-column medial lemniscus -> Transmits touch (tactile sensation), vibration and proprioception
Anterior spinothalamic tract -> Crude touch and pressure
Lateral spinothalamic tract -> Pain and temperature
None of the above -> Distractor

Question 53

Out of the choices below, make the best match between the cortical functional area and the cortical anatomical area for the Primary somatosensory cortex

  1. Insula
  2. Postcentral gyrus
  3. Precentral gyrus
  4. Posterior parietal lobe
  5. Cingulate gyrus

The correct answer is option b, Postcentral gyrus

Postcentral gyrus -> It’s the location of the primary somatosensory cortex (the main sensory receptive area for sense of touch). It also contains the sensory homunculus.
Insula -> A region in the cerebral cortex found deep within the lateral sulcus
Precentral gyrus -> Site of the primary motor cortex
Posterior parietal lobe -> Thought to be an area involved with integration of sensory information
Cingulate gyrus -> Part of the limbic system, involved in processing of emotions and behavior regulation. Also involved in regulating autonomic motor function.

Question 54

By comparing the two-point thresholds of different parts of the body you can measure tactile acuity. For the following areas of the body, which has the highest tactile acuity?

  1. Forearm
  2. Upper lip
  3. Sole of the foot
  4. Thumb
  5. All parts of the body have an equal measurement of tactile acuity

The correct answer is option b, the upper lip

Two point threshold is the distance between points at which a person recognizes they are being touched by two objects rather than one. It’s a spatial measure.

Upper lip -> Two-point threshold is about 10 mm
Forearm -> Two-point threshold is almost 40 mm
Sole of the foot -> Two-point threshold is about 20 mm
Thumb -> Two-point threshold is about 5 mm
option e is incorect.

Question 55

What’s the process where an application of a stimulus to the center of the receptive field would excite a neuron, but a stimulus applied near the edge inhibits it.

  1. Convergence
  2. Divergence
  3. Lateral inhibition
  4. All of the above
  5. None of the above

The correct answer is option c, Lateral inhibition

Lateral inhibition -> This process allows for better sensory acuity by increasing contrast in excitation and inhibition between neurons.
Convergence -> This is when multiple first order neurons converge to one second neuron which results in reduced acuity.
Divergence -> This is when one first order neuron stimulates several second order neurons. This allows for more precise perception by amplifying the signal from a single receptor/area
All of the above -> Not the best answer as the question is asking about a specific physiologic mechanism.
option e is incorrect and is a distractor

Question 56

A young woman presents with right sided loss of fine-touch and vibration sensation. She also presents with ipsilateral loss of proprioception. Which anatomical structure has likely been damaged?

  1. Right dorsal column
  2. Left spinothalamic tract
  3. Left dorsal column
  4. Right spinocerebellar tract
  5. Right spinothalamic tract

The correct answer is option

Left dorsal column -> Left dorsal column transmits information from the left side of the body.
Right dorsal column -> the dorsal column is responsible for fine-touch, vibration and proprioception. This dorsal column innervates the same side of the body. Therefore if there is a defect on the right side -> right dorsal column
Left spinothalamic tract -> Transmit information for temperature and pain.
Right spinocerebellar tract -> Unconscious proprioceptive information
Right spinothalamic tract -> Transmit information for temperature and pain.

Question 56

The primary motor cortex sends most of its output fibres into the _____ whereas the basal ganglia sends most of its output into the_____

  1. Reticulospinal tract, rubrospinal tract
  2. Rubrospinal tract, reticulospinal tract
  3. Extrapyramidal system, corticospinal tract
  4. Corticospinal tract, Extrapyramidal system
  5. None of the above

The correct answer is option c, Corticospinal tract, Extrapyramidal system

Reticulospinal tract, rubrospinal tract -> Both of these tracts form part of the extrapyramidal system. Also, they don’t receive major projects from the primary motor cortex.
Rubrospinal tract, reticulospinal tract -> Both of these tracts form part of the extrapyramidal system. Also, they don’t receive major projects from the primary motor cortex.
Extrapyramidal system, corticospinal tract -> Primary motor cortex sends its main output fibres into the corticospinal tract. The basal ganglia is a major portion of the extrapyramidal system. This system receives inputs from the cerebral cortex into the basal ganglia and then the basal ganglia sends out to the thalamus, to the cortex and brainstem.
None of the above -> Distractor

Credits

  • 41-49 (K. Thejasvin, 3rd year)
  • 50-57 (Rayan Alfuhaid, 3rd year)