Characteristics of Living Things:2.) Homeostasis:
What makes living things so special is not just that they’re so complex and highly organized, but that they
maintain their complexity and organization. This process, in which living things maintain themselves in the face of a Universe which often seems quite hostile to complexity and to organization, is known as
homeostasis. Homeostasis refers to the fact that living beings actively maintain a more or less stable internal environment. The proper term for an organism that is no longer capable of homeostasis is “dead.”
For the most part, homeostasis is maintained through some sort of
feedback mechanism. There is “feedback” in a system if some portion of the product of the system re-enters the system as input, and subsequently affects the system’s output. That is, the system responds to any perturbation. This feedback can be either positive or negative.
Within the body, feedback mechanisms maintain homeostasis in a 5-step process. Whenever any sort of imbalance occurs, because some body condition has deviated from its normal range of values, this will act as a
stimulus. A stimulus is any change in internal (or external) conditions that can be detected by the body.
The stimulus is detected by a
receptor (
sensor), which is usually part of the
nervous system. The receptor responds by generating an impulse that is relayed to a
control center via
afferent (
sensory) pathways. The control center will usually be part of the
Central Nervous System – either the
brain or the
spinal cord.
The control center responds to the stimulus and generates impulses that are relayed to an
effector (usually, either a gland or a muscle) via
efferent (
motor) pathways. The effector then takes some sort of action to bring the system back toward a state of balance.
Whether they use negative feedback or positive feedback, the
mechanisms that regulate homeostasis involve these five steps.
Homeostasis
Linear Mode
