Touch and Proprioception

A 20-year-old male presented to the neurology clinic with a progressive gait disturbance, limb coordination difficulties, and muscle weakness. His medical history revealed a family history of similar symptoms, suggesting a genetic etiology. Neurological examination demonstrated signs of cerebellar dysfunction, including dysarthria and impaired coordination of voluntary movements. Genetic testing confirmed the diagnosis of Friedreich's ataxia. What is the dysfunctional mechanism of this patient's condition at the cellular level?

• Increased frataxin protein levels causing dysfunction in DNA transcription

• Trinucleotide repeat expansion in the FXN gene resulting in dysfunction of the endoplasmic reticulum

• Reduced frataxin protein levels causing mitochondrial dysfunction

• Upper and lower motor neuron lesions due to autoimmune destruction of neurons

• Improved coordination of voluntary movements due to enhanced frataxin gene expression

Where would the cell body of a sensory neuron that transmits touch information from the cheek to the central nervous system be located?

• Ganglion alongside the brainstem

• Nucleus inside the brainstem

• Ganglion alongside the spinal cord

• Nucleus inside the spinal cord

• Ganglion immediately underneath the skin of the cheek

Afferent fibers that lack specialized receptors at their terminals detect which type of stimuli?

• Touch

• Vibration

• Pressure

• Pain

• Stretch

Which type of somatosensory afferents transmit information from touch mechanoreceptors to the central nervous system?

• Aβ

• Aδ

• C

• D

On which body part would the two-point discrimination threshold be shortest?

• Thigh

• Foot

• Arm

• Thumb

• Ear

A dermatome is an area innervated by:

• fibers of the cells from a single dorsal root ganglion.

• the axon of a single neuron.

• fibers with similar properties.

• fibers of the cells from a single nucleus in the brain stem.

Which afferents have the highest spatial resolution?

• Meissner

• Pacinian

• Merkel

• Ruffini

• Pain

Merkel afferent fibers convey information about which variable(s)?

• Motion detection

• Temperature

• Proprioception

• Shape and texture

• Subtle vibrations

The axons of the medial lemniscus synapse with neurons of the

• primary sensory cortex

• thalamus

• gracile nucleus

• cuneate nucleus

• dorsal root ganglion

Which feature is characteristic of the pseudounipolar neurons of the somatosensory system?

• Central and peripheral components of the fibers are of a similar length

• Thick fibers that enables fast signal transduction

• Fibers with particularly high myelin content

• Continuous fibers, with the cell body attached by a single process

• Multiple dendrites