homeostasis

Homeostasis and Physiological Control Systems

• Cells that can act as effectors in homeostatic reflexes are those that can respond to changes in the body's internal environment.
• Hormones are chemical messengers produced and secreted by glands, which travel through the bloodstream to reach their target cells.
• Hormones are produced and secreted from glands, such as the pancreas, thyroid, and adrenal glands.
• Neurotransmitters act on cells within the body, transmitting signals to regulate various physiological processes.
• A particular chemical messenger can serve multiple functions within the body, depending on the context and target cells.

Dynamic Constancy and Homeostasis

• Dynamic constancy refers to the ability of the body to maintain a relatively constant internal environment despite changes in the external environment.
• In the context of blood glucose levels, dynamic constancy means that the body maintains a stable level of glucose in the blood despite changes in food intake and energy expenditure.

Homeostatic Control Systems

• In the context of the homeostatic control system for body temperature, the correct sequence of events when room temperature decreases is:
  • Detection of temperature decrease by thermoreceptors
  • Transmission of signal to the hypothalamus
  • Activation of effectors (e.g. muscles, sweat glands) to increase heat production
  • Return of body temperature to normal range
• A positive feedback system is one in which the response to a stimulus amplifies the stimulus, leading to a continuous increase in the response.
• An example of a negative feedback system is the regulation of body temperature, where a decrease in temperature triggers a response that increases heat production to return the temperature to normal.
• The structure-function relationship in homeostatic control systems is exemplified by the hypothalamus, which has a specific structure that allows it to regulate body temperature.

Homeostatic Control and Variables

• When a change occurs in the variable being regulated, the negative feedback system responds to return the variable to its normal range.
• The stability of an internal environmental variable is determined by the balance between the rates of net gain and net loss.
• The set point of some variables regulated by homeostatic control systems can change in response to environmental changes or physiological needs.

Biological Rhythms and Homeostasis

• Biological rhythms, such as circadian rhythms, play a role in homeostasis by regulating physiological processes in response to environmental changes.
• The relationship between total-body balance and the rates of net gain and net loss is one of equilibrium, where the rates of gain and loss are balanced to maintain a stable internal environment.

Fluid Compartments and Homeostasis

• The interstitial fluid accounts for approximately 15% of the fluid in the blood and surrounding cells.
• The fluid compartment that accounts for the majority of all fluid in the body is the intracellular fluid.
• Maintaining differences in fluid composition across the cell membrane helps cells regulate their activity by controlling the movement of ions and molecules.

Homeostasis and Physiological Processes

• The main focus of homeostasis is to maintain a stable internal environment in relation to physiological variables such as temperature, pH, and blood glucose levels.
• Homeostasis is considered a dynamic process in that it constantly responds to changes in the internal environment to maintain a stable state.
• Physiological variables such as body temperature, blood glucose levels, and blood pressure are maintained within a predictable range through homeostatic control systems.