HOMEOSTASIS Identify homeostasis as the process by which an organism responds to its internal or external environment.

Regulation of an organism’s internal surroundings (environment) involves sensing the internal and external environment and changing physiological activities to keep condition within the range required to survive.

Let’s discuss the things that can effect the way we respond to our environment.

Homeo - sameness Stasis - standing still Homeostasis Homeo - sameness Stasis - standing still Homeostasis - the body’s ability to maintain a relatively constant internal environment despite changes in the external environment.

Homeostasis More a dynamic state in which internal conditions vary within narrow limits.

Virtually every organ system plays a role in maintaining homeostasis.

Homeostatic control mechanisms Communication within body essential for maintenance of homeostasis. Nervous and endocrine systems - major communication systems within the body.

Feedback mechanisms Homeostasis maintained through either: Negative feedback mechanisms opposes response to stimulus Positive feedback mechanisms enhances response to stimulus

Stimulus- something that causes a reaction in a living thing

Response-A reaction, as that of an organism or any of its parts, to a specific stimulus.

Homeostatic imbalance Most diseases and/or disorders result from homeostatic imbalance With aging: body organs and control systems become less efficient internal environment becomes less and less stable greater risk of illness/injury

Animals and plants respond in different ways Animals and plants respond in different ways. Let’s look at the way plants respond to their environment.

A plant’s responses to gravity, moisture, and light are called tropisms. Tropisms can be either negative or positive. Let’s look each one.

Negative tropism- Moving or turning away from a stimulus, such as light:

Positive tropism is when there is movement toward the source of stimulation.