Question

1. the cytoplasmic extensions that, together with the cell body, provide the main receptive surfaces for neurons are a. neurofibrils. b. nissl fibers. c. axons. d. dendrites. 2. masses of myelinated nerve fibers appear a. white. b. gray. c. brown. d. transparent. 3. which of the following is a type of neuroglial cell? a. astrocyte b. oligodendrocyte c. ependymal cell d. all of these are correct. 4. which of the following lists the parts of a reflex arc in the correct sequence? a. receptor, sensory neuron, motor neuron, interneuron, effector b. effector, receptor, sensory neuron, motor neuron, interneuron c. effector, sensory neuron, receptor, interneuron, motor neuron d. receptor, sensory neuron, interneuron, motor neuron, effector 5. when a nerve fiber is polarized, the concentration of a. sodium and potassium ions is higher on the inside of its membrane. b. sodium and potassium ions is higher on the outside of its membrane. c. sodium ions is higher on the inside of its membrane and potassium ions is higher on the outside. d. sodium ions is higher on the outside of its membrane and potassium ions is higher on the inside. 6. saltatory conduction a. occurs only if the myelin sheath is continuous. b. occurs only if nodes of ranvier are lacking. c. is faster than conduction on an unmyelinated fiber. d. is slower than conduction on an unmyelinated fiber. 7. what produces myelin in the brain and spinal cord? a. schwann cells b. astrocytes c. microglia d. oligodendrocytes 8. the most rapid nerve impulses are conducted on fibers that are a. thick and myelinated. b. thick and unmyelinated. c. thin and myelinated. d. thin and unmyelinated.

Explanation:

1. Dendrites are the cytoplasmic extensions that, along with the cell body, provide the main receptive surfaces for neurons.
2. Myelinated nerve fibers appear white.
3. Astrocytes, oligodendrocytes, and ependymal cells are all types of neuroglial cells.
4. The correct sequence of parts of a reflex arc is receptor, sensory neuron, interneuron, motor neuron, effector.
5. When a nerve fiber is polarized, sodium ions are higher on the outside of its membrane and potassium ions are higher on the inside.
6. Saltatory conduction is faster than conduction on an unmyelinated fiber.
7. Oligodendrocytes produce myelin in the brain and spinal cord.
8. The most rapid nerve impulses are conducted on thick and myelinated fibers.

Answer:

1. D. dendrites
2. A. white
3. D. All of these are correct
4. D. receptor, sensory neuron, interneuron, motor neuron, effector
5. D. sodium ions is higher on the outside of its membrane and potassium ions is higher on the inside
6. C. is faster than conduction on an unmyelinated fiber
7. D. oligodendrocytes
8. A. thick and myelinated