24 Cardiac output needs to vary greatly in order to meet the varying physiological demands for oxygen at cellular level. It is necessary, however, for BP to be maintained at a level that does not cause organ damage; such as a stroke through hypertension, or acute kidney injury through hypotension. Patients at risk of deterioration often display subtle changes clinically as a result of alterations in cardiac output and blood flow. Understanding the normal regulation of BP and cardiac output is helpful as it enables the nurse to interpret clinical assessment findings, relating them to the regulatory systems attempting to restore homeostasis. Regulation of BP occurs automatically via a number of control mechanisms, predominantly the autonomic nervous system and hormonal regulation. The autonomic nervous system is a branch of the central nervous system, which contributes to maintaining homeostasis. This autoregulatory system is controlled by centres within the brain stem and hypothalamus and works independently of conscious thought. It is subdivided into the sympathetic nervous system (SNS) and parasympathetic nervous system (PNS). Neural mechanisms lie within the medulla of the brain (Figure 24.1) in the cardiovascular centre (CVC). The CVC receives information from sensors, such as the baroreceptors
Circulatory physiology 3: control of circulation
Neurohormonal mechanisms of blood pressure control
Autonomic nervous system
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