Chapter 2. Neurophysiology
A novel drug produced by screening snake venoms was found to kill glial cell tumors in culture. However, initial in vivo studies showed that the drug did not enter the brain of experimental animals and therefore could not access glial cells in the intact brain. Which structure is most responsible for preventing the entry of this drug into the brain?
B Brain capillary endothelium
C Choroid plexus epithelium
B. The blood-brain barrier prevents the free access of most solutes from plasma to the brain extracellular fluid. The blood-brain barrier is formed by the capillary endothelial cells and supporting glial cells. The choroid plexus also contributes, to a lesser extent, by actively regulating cerebrospinal fluid composition.
A 28-year-old woman was prevented from traveling by air to a family wedding due to an acute episode of vertigo. Over the next few months, she experienced several transient, neurologic problems, including blurred vision, sudden muscle weakness in her legs, loss of perineal sensations, and urinary incontinence. What cellular defect is most likely to account for these clinical findings?
A Atrophy of skeletal muscles
B Demyelination of central nervous system (CNS) neurons
C Destruction of preganglionic sympathetic neurons
D Loss of CNS dopaminergic neurons
E Proliferation of Schwann cells
B. The involvement of somatic sensory and motor functions, as well as autonomic functions such as urinary continence, indicates the involvement of many parts of the nervous system. This presentation in a young woman is consistent with a diagnosis of multiple sclerosis, which is caused by the autoimmune destruction of myelin sheaths around neurons in the brain and spinal cord.
In a laboratory experiment, a cortical neuron was electrically stimulated to produce action potentials. The stimulated neuron made synaptic contact with another neuron in which a recording electrode was located. The recording electrode detected a small depolarization following the electrical stimulation of the first neuron. Which neurotransmitter was most likely to be released at the synapse between these neurons?
B. The neurotransmitter produces an excitatory postsynaptic ...