Organization & Cells of the Nervous System
Chapter 1: Organization & Cells of the Nervous System
Following an injury in the workplace that affected a patient’s right arm, causing loss of movement of that limb, it was determined that the injury had disrupted axoplasmic transport in the sensory and motor nerves of that limb. Which of the following statements accurately reflects a fundamental property of axonal transport?
A. Large membranous organelles are transported by slow axonal transport.
B. Cytosolic proteins are transported by fast axonal transport.
C. Retrograde transport is generally limited to a fixed rate of movement of particles.
D. Anterograde transport is dependent on microtubules.
E. The motor protein kinesin specifically governs slow axonal transport.
D. The vast majority of axonal proteins are synthesized in the cell soma. Axonal transport includes fast and slow axonal transport from the cell soma along the axon to the presynaptic terminus. Fast axonal transport is for transport of large organelles and vesicles and depends on microtubules and microtubule motors (kinesins for anterograde transport and dyneins for retrograde transport). Slow axonal transport is for cytosolic and cytoskeletal proteins. (Recent studies suggest that slow transport may also involve microtubules, but the cytosolic and cytoskeletal cargoes may stop more along the way.)
Which of the following best describes the characteristic of white matter?
A. White matter contains neuronal cell bodies, dendrites, and synapses.
B. White matter contains myelinated axons, astrocytes, and oligodendrocytes.
C. White matter contains pericytes and ependymal cells.
D. White matter contains all neurons and glia in the central nervous system (CNS).
E. White matter includes all tracts and nerves in the CNS and peripheral nervous system (PNS).
B. White matter is found in only the CNS (not the PNS) and contains myelinated axons, white matter astrocytes, and the myelinating oligodendrocytes. Pericytes line the brain capillaries (and white matter does have capillaries), but ependymal cells are located only in the ventricles.
Which of the following best describes the functions of astrocytes?
A. Astrocytes form cerebral blood vessels and the blood–brain barrier.
B. Astrocytes line the brain ventricles and form the brain capillaries.
C. Astrocytes provide energy substrates for neurons and can regulate blood flow.