MCAT Social and Behavioral Sciences : Neurons and Neural Physiology
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Example Question #1 : Neurons And Neural Physiology
Which of the following would be characteristic of a somatic efferent neuron?
Stimulate action of a muscle fiber
Inhibit the parasympathetic nervous system
Carry sensory information to the brain
Stimulate the sympathetic nervous system
Carry sensory information to the spinal cord
Stimulate action of a muscle fiber
A generalized reflex arc describes the detection of an environmental signal, interpretation of that signal, and stimulation of a response.
Afferent fibers are generally classified as "sensory afferent" and describe the neural fibers that are excited by an external stimulus. Afferent fibers always carry signals toward to central nervous system. Various interneuron fibers within the central nervous system can then be stimulated to process and integrate the signal. Interneurons then stimulate efferent neurons, which carry signals away from the central nervous system. Somatic efferent neurons interface with muscle fibers and can cause a physical response.
For example, if you place your hand on a hot stove, sensory afferent fibers will carry to signal to your brain, where interneurons will interpret the signal and stimulate somatic efferent fibers to contract your biceps and pull your hand away from the surface.*
*In certain cases, the interneuron will be located in the spinal cord. In monosynaptic reflexes, no interneuron is used. The example presented is only a generalized model and is not meant to be universally applicable.
Example Question #1 : Neurons And Neural Physiology
Glia are non-neuronal cells which have specialized functions for supporting neurons. Which of the following is not a glial cell?
Oligodendrocytes
Schwann cells
Myelin
Astrocytes
Ependymal cells
Myelin
“Myelin” is the insulating sheath wrapped around many axons to increase the speed of conduction of action potentials. It is not a type of glial cell even though glial cells form it.
The remaining answers are all examples of glia. “Schwann cells” (located in the peripheral nervous system) and “oligodendrocytes” (located in the central nervous system) form myelin. “Astrocytes” (located in the central nervous system) are star-shaped glial cells with many roles, including providing metabolic and structural support to neurons. “Microglia” help to remove debris. Last, “ependymal cells” form cerebrospinal fluid (CSF).
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