UNIT 4: Homeostasis
Chapter 9: Homeostasis: A Fine Balance
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9.1: Maintaining an Internal Balance
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Homeostasis – is the physiological state of the body in which internal
physical and chemical conditions are kept within a range that is suitable for
life processes.
The maintenance of the body’s internal conditions is homeostasis. It is the
maintaining of physical and chemical conditions within tolerable ranges.
Homeostasis is a dynamic process that is continuously adjusted in response
to changes in the internal or external environment.
Fluids and conditions needed to be monitored and adjusted for proper
functioning of the body. These include internal temperature, hormone levels,
pressures, pH, flow and concentration of glucose, and other solutes in the
blood.
The Internal Environment
Internal environment – is the extracellular fluid, which consists of the fluid
that surrounds the cells and tissues in the body and the plasma portion of the
blood.
Interstitial fluid – is the fluid that surrounds the body cells.
The internal environment must be maintained within tolerable chemical and
physical conditions for the cell to function properly. The internal
environment consists of the interstitial fluid found between the cells and
tissues, and the plasma portion of blood. An adult has approximately
15 L. of extracellular fluid, which makes up about 20% of the body’s mass.
The extracellular fluid acts medium for delivering energy, transport
chemicals, and eliminating wastes, into and out of the cells.
Physical activity, other extreme conditions, and infections can tip the
balance that is maintained in the extracellular fluid, which can be dramatic
and often negative to cellular functions. The body must maintained and
regulate its internal conditions.
Organ Systems Involved in Homeostasis
Homeostatic mechanism – is a system that monitors internal and external
conditions and changes bodily functions to maintain homeostasis.
Figure 2: this diagram shows some of the organ systems in the human body. All of the
organ systems play a role in maintaining homeostasis in the internal environment.
- Nervous system receives sensory information from the external
environment and informs the body of these conditions to regulate
homeostasis.
- Excretory system is responsible for removing liquid waste and
maintain water balance.
- Endocrine system regulates levels of hormones essential to life.
- Circulatory system carries hormones, oxygen and nutrients to all the
cells of the body and removes wastes.
- Digestive system breaks down nutrients need for cellular function.
- Integumentary (skin) system is responsible to maintain body
temperature.
The cells, tissues and organs are responsible for carrying out the basic
metabolic activities that support the function of the organ system. All organ
systems coordinate to carry out the tasks necessary for the survival of the
organism.
These tasks are:
a) Take in nutrients and other required chemicals from the environment,
process and transported throughout the body, along with the removal of
metabolic wastes.
b) Synthesize proteins, fats, carbohydrates and other molecules essential for
life.
c) Sense and respond to changes in the external environment.
d) Protect the body from injury and infection by viruses, bacteria and other
pathogens.
e) Reproduce, protect and feed offspring.
These tasks maintain homeostasis within the body.
The Endocrine and nervous system are the most important systems in
maintaining homeostasis.
When homeostatic mechanisms respond to internal and external conditions,
it is described as detection – correction or feedback systems.