A report comes back indicating that muscular atrophy has occurred. This involves a decrease in muscle cell

A. myelogram: A myelogram is an imaging study in which contrast is injected into the subarachnoid space to visualize the spinal canal on x-ray/CT - it is primarily imaging, not the laboratory analysis of CSF.
B. BUN: Blood urea nitrogen is a blood chemistry test (kidney function) and does not analyze cerebrospinal fluid.
C. lumbar puncture: A lumbar puncture (spinal tap) is the procedure used to collect cerebrospinal fluid for laboratory analysis (cells, glucose, protein, culture, etc.).
D. IVP: An intravenous pyelogram (IVP) is an imaging study of the urinary tract using contrast - unrelated to CSF.

A. increase in number: Cardiac myocytes in the adult are largely terminally differentiated, so they do not appreciably multiply (hyperplasia) in response to increased workload.
B. increase in excitability: Increased workload causes structural and functional adaptation (hypertrophy) rather than a primary increase in membrane excitability; excitability changes are more a feature of pathological electrical remodeling.
C. decrease in length: Cells do not shorten as an adaptive response to increased workload; they grow (change in size/shape) rather than decrease in length.
D. increase in size: Cardiac muscle responds to increased workload by hypertrophy (an increase in cell size) to generate greater contractile force.