Anatomy Homeostasis

I. Homeostasis and Disease is the maintenance of a relatively constant internal environment. The ability to maintain the balance depends on two factors The status of the physiological systems involved. The nature of the stress that’s imposed.

Homeostasis is a “balancing act” that must adapt to sudden or gradual changes in our environment, arrival of pathogens, injuries… Homeostasis is the ability to maintain a relatively stable internal environment in an ever-changing outside world The internal environment of the body is in a dynamic state of equilibrium Chemical, thermal, and neural factors interact to maintain homeostasis

What contributes to or effects this balancing act? Age, health, and genetics affect our ability to maintain homeostasis. If the physio-logical values go outside the normal range it can affect other systems and can be fatal.

Disease is the failure to maintain homeostatic conditions Disease is the failure to maintain homeostatic conditions. It can start in a specific cell/tissue and continue throughout the body. The body often overcomes some diseases, for example the flu.

II. Homeostatic Regulation and Control Mechanisms Homeostasis regulation is the adjustment of physiological systems to preserve balance/to keep the internal environment within desired limits (simply put… it is the communication within the body to maintain homeostasis) Two homeostatic pathways are involved: (stop see if students have read pg. 9-11)

1. Afferent pathway- carrying to or toward a center (receptor carries to the control center). Efferent pathway –carrying away or away from (the control center sends a message to the effector).

B. Control Mechanisms Variable produces a change in the body Receptor monitors the environments and responds to changes (stimuli)- sends to the control center. Control center determines the set point at which the variable is maintained (decides what message to send to the effector) Effector provides the means to respond to the stimulus. It is a cell or organ that responds to the command of the control center. The response then “feeds back” to influence the stimulus (variable).

Case study A Spill at Parsenn Bowl: Knee injury and Recovery

Figure 1.4

Negative Feedback In negative feedback systems, the output shuts off the original stimulus Example: Regulation of blood glucose levels Figure 1.5

Positive Feedback In positive feedback systems, the output enhances or exaggerates the original stimulus Example: Regulation of blood clotting Figure 1.6

Review: Feedback mechanisms regulate biological systems Feedback mechanisms allow biological processes to self-regulate Negative feedback means that as more of a product accumulates, the process that creates it slows and less of the product is produced Positive feedback means that as more of a product accumulates, the process that creates it speeds up and more of the product is produced

Figure 1.13 Regulation by feedback mechanisms Negative feedback  Enzyme 1 B D Enzyme 2 Excess D blocks a step D D C Enzyme 3 D (a) Negative feedback W Enzyme 4 Figure 1.13 Regulation by feedback mechanisms X Positive feedback + Enzyme 5 Excess Z stimulates a step Z Y Z Z Enzyme 6 Z (b) Positive feedback

Homeostatic Imbalance: is a disturbance of homeostasis or the body’s normal equilibrium. overwhelms the usual negative feedback mechanisms allowing destructive positive feedback mechanisms to take over.