USMLE Step 1 Qs (10)

50 Questions | Total Attempts: 236

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USMLE Step 1 Qs (10)

Questions from various sources for practicing


Questions and Answers
  • 1. 
    A lesion at which site in the diagram below could produce weakness of muscles that mediate swallowing, chewing, breathing, and speaking?
    • A. 

      D

    • B. 

      E

    • C. 

      F

    • D. 

      G

    • E. 

      H

  • 2. 
    The cerebellum is derived from which of the following?
    • A. 

      Neural crest cells

    • B. 

      Rhombic lips

    • C. 

      Mesencephalon

    • D. 

      Sulcus limitans

    • E. 

      Telencephalon

  • 3. 
    The anterior pituitary is derived from which of the following?
    • A. 

      Neural crest cells

    • B. 

      Rhombic lips

    • C. 

      Myelencephalon

    • D. 

      Floor plate

    • E. 

      Rathke's pouch

  • 4. 
    young child is brought into the hospital emergency room because he has episodes of vomiting, headaches, problems in acquisition of motor skills, cranial nerve dysfunction, and problems in breathing. This combination of syndromes most closely relates to which of the following disorders?
    • A. 

      Cleft palate

    • B. 

      Hydrocephalus

    • C. 

      Anencephaly

    • D. 

      Syringomyelia

    • E. 

      Congenital aneurysm

  • 5. 
    Apoptosis is likely to occur following which of the following events?
    • A. 

      Stimulation of an afferent nerve fiber

    • B. 

      Severing of an afferent nerve fiber

    • C. 

      The beginning of myelin formation

    • D. 

      Elimination of nerve growth factor

    • E. 

      Reduction in brain serotonin levels

  • 6. 
    The methods involving microinjections of Fluoro-Gold or horseradish peroxidase (HRP) have been employed over the past few decades by many investigators. These methods have been used to identify which of the following
    • A. 

      Cell bodies

    • B. 

      Metabolic activity of neurons

    • C. 

      Sensory endings of nerve fibers

    • D. 

      Central nervous system receptors

    • E. 

      Degenerating axons

  • 7. 
    Substances such as tritiated amino acids and phaseolus vulgaris agglutinin microinjected into specific regions of the brain have also been employed by many investigators for the study of the nervous system. These methods are specific in that they label which of the following?
    • A. 

      Cell bodies

    • B. 

      Glial cells

    • C. 

      Sensory receptors

    • D. 

      Motor end plates

    • E. 

      Axons and axon preterminals

  • 8. 
    Which of the following procedures would be utilized in order to show positive staining of groups of serotonin neurons
    • A. 

      Electrical brain stimulation

    • B. 

      Glutamate stimulation of the brain

    • C. 

      HRP staining of neurons

    • D. 

      Immunocytochemical labeling

    • E. 

      Metabolic staining of neurons

  • 9. 
    An individual sustained a severe knife wound, damaging a spinal nerve adjoining its entry to the spinal cord. If one could examine this peripheral nerve and its cell body, which of the following events would he or she most likely observe?
    • A. 

      A displacement of the nucleus toward the periphery of the cell

    • B. 

      A mitotic division of the neuronal cell body

    • C. 

      A more intense staining of the cell body

    • D. 

      Degeneration of processes along the axon proximal but not distal to the lesion

    • E. 

      An initial loss of mitochondria in the axoplasm at Ranvier's node

  • 10. 
    A 65-year-old man is diagnosed with a form of a peripheral neuropathy. This individual will likely display which of the following
    • A. 

      A loss in motor function, but sensory functions will remain largely intact

    • B. 

      A reduction in conduction velocity of the affected nerve

    • C. 

      An increase in the number of Ranvier's nodes

    • D. 

      Degeneration of myelin but the axon will typically remain intact

    • E. 

      Signs of an upper motor neuron (UMN) paralysis

  • 11. 
    During an in vitro experiment, the membrane potential of a nerve cell is hyperpolarized to –120 mV. At that time, a transmitter, known to be inhibitory in function, is applied to the preparation and results in a depolarization of the membrane. Which of the following is the most likely reason for this occurrence?
    • A. 

      Inhibitory transmitters normally depolarize the postsynaptic membrane

    • B. 

      The normal response of the postsynaptic membrane to any transmitter is depolarization

    • C. 

      The inhibitory transmitter activates ligand-gated potassium channels

    • D. 

      Sodium channels become inactivated

    • E. 

      Calcium channels become activated

  • 12. 
    The passive spread of a presynaptic current acorss a gap junction that is activated by changes in voltage, pH, or calcium ion levels is most closely associated with which of the following
    • A. 

      The resting potential

    • B. 

      The action potential

    • C. 

      Electrical presynaptic potentials

    • D. 

      Electrical postsynaptic potentials

    • E. 

      Receptor potentials

  • 13. 
    Which of the following characterizes a principal feature of axosomatic synapses
    • A. 

      It is referred to as a type I synapse

    • B. 

      They have an electrical continuity linking the pre- and postsynaptic cells

    • C. 

      They are typically inhibitory

    • D. 

      Synaptic transmission is mediated by glutamate

    • E. 

      They form the predominant synapse of cortical projections to the neostriatum

  • 14. 
    Which of the following is a second messenger system directly activated by the binding of norepinephrine to a beta-adrenergic receptor
    • A. 

      Inositol 1,4,5-triphosphate (IP3)

    • B. 

      Adenosine 3',5'-cyclic phosphate (cAMP)

    • C. 

      Diacylglycerol (DAG)

    • D. 

      Arachidonic acid

    • E. 

      Prostaglandins

  • 15. 
    Hyperpolarization of the neuron is governed by which of the following
    • A. 

      Chloride and sodium

    • B. 

      Chloride and potassium

    • C. 

      Potassium and sodium

    • D. 

      Sodium and calcium

    • E. 

      Sodium only

  • 16. 
    The release of the transmitter is directly governed by which of the following
    • A. 

      Sodium influx

    • B. 

      Sodium efflux

    • C. 

      Potassium influx

    • D. 

      Potassium efflux

    • E. 

      Calcium influx

  • 17. 
    N-methyl-D-aspartate (NMDA), kainate, and quisqualate all act on which of the following receptors
    • A. 

      GABA receptors

    • B. 

      Excitatory amino acid receptors

    • C. 

      Adrenergic receptors

    • D. 

      Opioid receptors

    • E. 

      Dopamine receptors

  • 18. 
    In the biosynthesis of dopamine, which of the following is the immediate precursor of dopamine?
    • A. 

      Tyrosine

    • B. 

      Tyrosine hydroxylase

    • C. 

      Tryptophan

    • D. 

      L-Dihydroxyphenylalanine (L-DOPA)

    • E. 

      Dopamine beta-hydroxylase

  • 19. 
    A baby is born with an inherited autosomal recessive trait in which there is a delay in development, resulting in the occurrence of seizures and mental retardation. The child was diagnosed as having phenylketonuria (PKU). Which of the following is the likely neurochemical locus of this genetic defect?
    • A. 

      Tyrosine

    • B. 

      Tryptophan

    • C. 

      Tryptophan hydroxylase

    • D. 

      Dopamine

    • E. 

      Phenylalanine (Phe) hydroxylase

  • 20. 
    After an individual is admitted to the hospital, it is determined that he displays a variable weakness of cranial nerve and limb muscles but shows no clinical signs of denervation from tests, which include electromyogram (EMG) recordings. This disorder was partially reversed by the administration of drugs that inhibit acetylcholinesterase. Which of the following is the likely basis for this disorder?
    • A. 

      The production of excessive quantities of acetylcholine (ACh)

    • B. 

      The production of antibodies that act against nicotinic ACh receptors

    • C. 

      A minor stroke involving the motor strip of the cerebral cortex

    • D. 

      A vitamin B deficiency

    • E. 

      Viral encephalitis

  • 21. 
    The neurotoxin, -bungarotoxin, has been utilized as a valuable experimental tool because it binds to which of the following?
    • A. 

      GABAA receptor

    • B. 

      GABAB receptor

    • C. 

      Nicotinic receptor

    • D. 

      NMDA receptor

    • E. 

      Histamine receptor

  • 22. 
    A 60-year-old male has high blood pressure and the diagnosis indicates that it is due in part to retention of water. Which of the following compounds would most likely relate to this process
    • A. 

      Oxytocin

    • B. 

      Serotonin

    • C. 

      Histamine

    • D. 

      Vasopressin

    • E. 

      Somatostatin

  • 23. 
    A 65-year-old man has been experiencing considerable pain due to a chronic back problem. If the patient is administered morphine to alleviate the problem, which of the following is a possible mechanism by which morphine would provide effective action
    • A. 

      Release of somatostatin

    • B. 

      Release of histamine

    • C. 

      Release of vasopressin

    • D. 

      Release of ACh

    • E. 

      Release of substance P

  • 24. 
    Which of the following receptors requires the simultaneous binding of two different agonists for activation?
    • A. 

      L-AP4 receptor

    • B. 

      Kainate receptor

    • C. 

      NMDA receptor

    • D. 

      AMPA receptor

    • E. 

      GABAA receptor

  • 25. 
    A 16-year-old boy takes phencyclidine (PCP). The deleterious effects of the drug are due in part to which of the following
    • A. 

      Blockade of NMDA receptors

    • B. 

      Blockade of AMPA receptors

    • C. 

      Blockade of cholinergic receptors

    • D. 

      Blockade of GABAA receptors

    • E. 

      Blockade of GABAB receptors

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