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Chapter 18: Autonomic Nervous System: Sympathetic, Parasympathetic, & Enteric

A 58-year-old woman is suffering from hypertension, and the drugs available to her seem to be of little help. Recently, a new drug was approved for distribution, and the patient’s physician recommended that she try it. The specific feature of this drug is that it selectively blocks synaptic transmission in autonomic ganglia in order to control blood pressure. Which of the following best characterizes this drug?

A. Cholinergic antagonist

B. Noradrenergic antagonist

C. Serotonergic antagonist

D. γ-Aminobutyric acid (GABA)-ergic antagonist

E. Peptidergic antagonist

A. The transmitter released from preganglionic endings of both sympathetic and parasympathetic fibers is acetylcholine (ACh). The other transmitters listed are not involved at this synapse. Evidence in support of this view is derived, in part, from studies that demonstrated that drugs that block nicotinic receptors (eg, hexamethonium chloride, curare) also block the output of these systems.

A patient is diagnosed with a hypothalamic tumor that results in significant alteration of autonomic functions, including loss of regulation of blood pressure and heart rate. Such effects upon autonomic functions can be understood in terms of the functional connections of the hypothalamus with a brainstem or spinal cord structure. Which of the following structures normally receives such inputs?

A. Ventrolateral nucleus of the thalamus

B. Nucleus accumbens

C. Solitary nucleus

D. Red nucleus

E. Ventral horn cells at the level of C8 to T12 of the spinal cord

C. The solitary nucleus of the medulla plays a significant role in the neural control of autonomic functions because it receives input from several different regions of the brain that regulate such functions. These inputs include fibers that arise from the hypothalamus, central nucleus of the amygdala, midbrain periaqueductal gray, and sensory processes (ie, visceral afferents) of the glossopharyngeal and vagus nerves. The last signal reflects changes in blood pressure and levels of oxygen and carbon dioxide in the blood. The ventrolateral nucleus of the thalamus, red nucleus of the midbrain, and ventral horn cells of the spinal cord are associated with somatomotor rather than autonomic function. The nucleus accumbens is believed to be associated with motivational processes.

A patient is brought to the emergency department of a local hospital after he experienced orthostatic hypotension following a rapid response to a postural change. Magnetic resonance imaging (MRI) suggests that this change in blood pressure was ...

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