NBME 13 with complete solutions

NBME 13progressive weakness, dec strength, hand muscle atrophy, diffuse hyperreflexia and fasciculations on hands and arms, normal sensory exam; - correct answer amyotrophic lateral sclerosis (ALS) --death of both upper and lower motor neurons in the motor cortex of the brain, the brain stem, and the spinal cord --Stephen Hawking disease --*UMN and LMN signs* --rapidly progressive weakness with fasciculations eventually leading to muscle atrophy, spasticity, dysarthria, dysphagia, respiratory compromise, death from respiratory failure UMN vs LMN weakness - correct answer --UMN weakness (brain to spinal cord) manifests in hyperreflexia and rigid muscle tone, positive Babinski sign --LMN weakness (anterior horn to muscle) manifests in muscle atrophy, decreased reflexes, fasciculations, and flaccid muscle tone history of numbness of fingers on left hand, loss of touch graphesthesia, loss of two point discrimination in left hand - correct answer --lesion in somatosensory cortex on contralateral side (right hemisphere) --graphesthesia is the ability to sense what is being drawn or written via touch on their hand --the postcentral gyrus is a prominent structure in the parietal lobe of the human brain; it is the location of the primary somatosensory cortex, the main sensory receptive area for the sense of touch missense mutation of tyrosine kinase domain of TrkA gene disrupts what process? - correct answer phosphorylation of downstream molecules in response to nerve growth factor --A tyrosine kinase is an enzyme that can transfer a phosphate group from ATP to a protein in a cell. It functions as an "on" or "off" switch in many cellular functions. Tyrosine kinases are a subclass of protein kinase. --The presence of this kinase leads to cell differentiation and may play a role in specifying sensory neuron subtypes. Mutations in this gene have been associated with congenital insensitivity to pain with anhidrosis, self-mutilating behavior, mental retardation and cancer this part of the brain is affected most in chronic alcoholics - correct answer --anterior vermis