Case Studies

Case Studies

Case Study 3—Shy Drager Syndrome

1. Functions of nearly all organ systems and bodily functions are controlled by the autonomic nervous system. This is because there is an interplay between the parasympathetic and sympathetic divisions. Since there is a central failure of the autonomic nervous system in the Shy Drager Syndrome, nearly all of the major organ systems of the body are adversely affected such as regulation of blood pressure in the arteries, and the functioning of the bronchioles which is responsible for controlling flow of air in the lungs. Apart from this, various functions of the gastrointestinal tract like absorption, digestion, secretion and motility are also affected adversely. Shy Drager's Syndrome also affects the emptying and filling of the bladder, sexual responses and erectile functions, functioning of the eye muscles, thermoregulatory sweat gland functions, and metabolic activity of adipose and liver tissues.

2. When a healthy person suddenly stands up, arterial blood pressure decreases since blood pools in the legs' veins. The fall in arterial blood pressure is, however, transient since the parasympathetic and sympathetic nervous systems quickly detect and compensate for the idiosyncrasy. This reflex is mainly the result of blood pressure information being relayed to specific stem centers in the brain from baroreceptors present in the carotid sinus. These brain stem centers significantly augment sympathetic outflow to the blood vessels and the heart while also decreasing the parasympathetic outflow to the heart. As a result of sympathetic and parasympathetic functions, there is an increase in the heart rate as well as contractility. This increases cardiac output and constricts, arterioles, thereby increasing the total peripheral resistance. This also leads to vasoconstriction which causes an increase in venous returns to the heart. Although a human would normally be unaware of it, mainly due to the amazing speed at which these bodily responses take place, when combined, these responses help to restore arterial blood pressure back to normal values. However, since parasympathetic and sympathetic nervous systems are seriously damaged in the case of Mr. Garcia, his baroreceptor reflexes are seriously compromised. Hence, when he suddenly stands up, there is orthostatic hypotension and a sudden fall in arterial blood pressure which the weak autonomic reflexes are unable to negotiate. Therefore, Mr. Garcia feels dizzy and faints whenever he stands up suddenly because of the sustained fall in arterial blood pressure and the consequent fall in blood flow to the brain.

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