Homeostasis

Page 1

Responding to Change

• In order to survive, and organism must be able to adapt to its environment, whether to an internal or external condition

• Homeostasis is the ability for an organisms body to adapt or change to suit their environment.

- The constant internal environment within an organism despite internal or external changes

• Homeostasis is mostly maintained through the internal metabolic reactions occurring in all cells- think cellular respiration or control of materials entering a cell via the cell membrane.

• There are two types of metabolic reactions:

Catabolic Reactions: Break down complex molecules into simpler ones

Anabolic Reactions: Build simple materials into complex molecules (uses energy)

Enzymes

• Each step of the metabolic process requires a specific enzyme reaction to occur.

• As enzymes are pH and temperature specific, they require very specific internal environments to work properly

Tolerance Range

• Tolerance Range is the full range where the enzyme (and therefore the process) can still work, even if only slightly

• Optimal Range is the ideal condition for the enzyme to work at. This means that the enzyme is working to its full ability and fulfilling its potential

Page 2

• Irritability is the ability to detect and respond to changes in the environment

• Stimulus is any change in the environment of an organism that brings about a response

• Coordination occurs when different body parts work together to maintain homeostasis. As such, an organisms irritability enables it to detect a stimulus to which its body can coordinate a response

Stimulus-Response Model

• A stimulus can either be physical or chemical.

• For a response to be formed, an organism must have cells that can detect a specific stimulus and then coordinate a response

• How the human body does this is conceptualised through the stimulus-response model

- Sees any response to a stimulus as occurring in 5 steps:

1. Input: The original stimulus

2. Receptor: A specialised cell or organ that receives the stimulus and passes the information along

3. Regulator: Control mechanism that decides upon and evokes the correct response

4. Effector: The cell or organ which carries out the response

5. Output: The actual response that occurs

Feedback

• Whenever the internal environment an organism fluctuates from the optimum level, the body will activate control systems to return it to the optimum. The constant receiving of information is called feedback.

Negative Feedback: The response is reversed and negated. It is constant and never fully resolves.

Positive Feedback: The same response continues the feedback until the issue is fixed

The Two Main Homeostatic Systems

• The nervous system: The system of our nerves and impulses which control how our bodies react to stimuli in a quick and immediate fashion

• The endocrine system: Controls our hormones and is responsible for slower and longer lasting responses to stimuli.