Practice Questions

Group A fibers (like somatic motor fibers and large sensory fibers for touch and position) are the thickest, most heavily myelinated fibers in the body, providing the fastest nerve conduction velocities.

Ependymal cells are ciliated, cuboidal-to-columnar glial cells that line the fluid-filled cavities of the CNS (ventricles and central canal) and help secrete and circulate cerebrospinal fluid.

Irritability (excitability) is the physiological ability of a neuron or muscle cell to respond to a stimulus by generating an electrical signal. Conductivity refers to its ability to transmit that signal.

Hyperkalemia reduces the concentration gradient for K⁺. As a result, less K⁺ leaves the cell through leak channels, leaving more positive charge inside and shifting the resting membrane potential toward depolarization.

In the PNS, a bundle of axons is called a nerve. In contrast, a bundle of axons in the CNS is called a tract. A ganglion is a cluster of cell bodies in the PNS.

Endorphins and enkephalins are endogenous opioids that bind to opioid receptors in the brain and spinal cord, powerfully blocking the transmission and perception of pain signals.

Axoaxonic synapses occur when one axon terminal synapses onto another axon terminal. They regulate (facilitate or inhibit) the amount of calcium that enters the second terminal, modulating neurotransmitter release.

Microglia act as the resident macrophages of the central nervous system, migrating to sites of injury or infection to clear away dead tissue, plaques, and pathogens.

The autonomic (visceral) nervous system controls involuntary physiological functions by regulating the activity of smooth muscles, cardiac muscles, and secretory glands.

Unlike acetylcholine which is destroyed by enzymes, monoamine neurotransmitters (like serotonin, dopamine, and norepinephrine) are primarily cleared by active reuptake transporters bringing them back into the presynaptic knob.