Essentials of Human Physiology for Pharmacy

chapter one: Physiology and the concept of homeostasis 3Two regulatory systems in the body influence the activity of all the otherorgan systems so that homeostasis is ultimately maintained:• Nervous system• Endocrine systemThe nervous system has three functional components (see Figure 1.1):• Sensory division of the peripheral nervous system• Central nervous system• Motor division of the peripheral nervous systemMany different types of sensory receptors are located throughout thebody. These receptors monitor the status of the internal environment or thatof the surroundings. Sensory receptors are sensitive to specific types of stimuliand measure the value of a physiological variable. For example, arterialbaroreceptors measure blood pressure and chemoreceptors measure the oxygenand carbon dioxide content of the blood. The information detected by thesesensors then travels by way of afferent neuronal pathways to the centralnervous system (CNS). The CNS is the integrative portion of the nervous systemand consists of the (1) brain and the (2) spinal cord.The brain receives, processes, and stores sensory input; generatesthoughts; and determines the reactions that the body should perform inCENTRALNERVOUSSYSTEMSENSORYDIVISIONMOTORDIVISIONSensoryreceptorsAfferentneuronEfferentneuronEffectortissueFigure 1.1 Functional components of the nervous system. The sensory division ofthe peripheral nervous system is sensitive to changes in the internal and externalenvironment. The information gathered by this component is transmitted to theCNS where it is processed, integrated, and interpreted. The CNS then determinesthe appropriate response to this input. This response is carried out by the transmissionof nerve impulses in the motor division of the peripheral nervous systemto the effector tissues.