Introduction to Homeostasis in Physiology

Introduction to Homeostasis

• Homeostasis is the maintenance of a stable internal environment, which is a dynamic state of equilibrium.
• It's not static; it constantly attempts to maintain equilibrium.
• Homeostasis is a vital process for normal body functioning and sustaining life.
• Homeostatic imbalance, also known as pathophysiology, is a disturbance in homeostasis. It results in disease.
• The nervous and endocrine systems are crucial for maintaining homeostasis.
• The many organ systems of the body are interconnected and coordinate their functions to maintain homeostasis, even if they have opposing effects.

Learning Outcomes

• Students will be able to describe human physiology.
• Students will be able to outline the structure and function of key systems.
• Students will be able to describe homeostasis.
• Students will be able to explain positive and negative feedback systems.

Physiology – Study of Life Processes

• Physiology describes the processes that occur within an organism.
• Physiology studies how different systems work together, including how substances move, how cells respond to changes, and how nutrients are broken down and delivered.
• Movement of substances and locomotion are key components.
• Respiration is the process of gas exchange.
• Sensation and responsiveness include the ability to sense changes and react.
• Nutrition covers digestion and the breakdown and delivery of nutrients.
• Metabolism includes all chemical reactions within the body, as well as energy production and the creation of body structures.
• Excretion is the elimination of waste from metabolic reactions.
• Reproduction is the production of future generations.
• Growth involves increasing cell size or number.

Physiology: Structural Organization

• Physiology requires a good understanding of anatomy to explain how it works.
• The levels of organization in physiology are: molecular, cellular, tissue, organ, organ system, and organism.

Homeostasis: Organ System Level

• Homeostasis occurs at the organ system level.

Homeostatic Control Mechanisms

• Homeostatic control involves a stimulus, receptor, control centre, effector, and response.
• The stimulus produces a change in a variable.
• The receptor detects the change in variable.
• The control centre processes information and sends signals.
• The effector produces the response.
• The response influences the stimulus magnitude.
• Variables in homeostasis must be returned to their set points.

Homeostatic Control: Example - Glucostatic Control

• Homeostatic control maintains blood glucose levels at around 90 mg/100 ml.
• When blood glucose rises, the pancreas releases insulin, resulting in cells taking up glucose and the liver storing glucose as glycogen.
• When blood glucose levels drop, the pancreas releases glucagon, leading to the liver breaking down glycogen and releasing glucose into the blood.

Terminology: Gluconeogenesis, Glycogenolysis, Lipolysis, Glycogenesis, Lipogenesis

• These are key terms related to glucose/lipid processes and their definitions are detailed.

Systems Working in Harmony: The Stress Response

• The body has specific mechanisms to maintain homeostasis during stress.
• These mechanisms involve hormones like adrenaline, activating specific processes in different organs.
• Key processes include glycogenolysis (breaking down glycogen) and gluconeogenesis (producing glucose) in the liver, and lipolysis (breaking down fat) in adipose tissue.
• This results in an energy response for the body.

Homeostatic Loops

• Negative feedback loops are the most common type of homeostatic loop.
• Positive feedback loops are used in specific situations, such as blood clotting.

Example of Positive feedback: Auto-amplification of cytokines in immunity

• This feedback mechanism amplifies immune/inflammatory reactions.
• Cytokines (e.g., TNF) and chemokines (e.g., CCL2) are increased to elevate and enhance an immune response.

Example of Negative feedback: Suppressors of cytokine signalling

• Inbuilt feedback mechanisms that limit cytokine signalling.
• This prevents over-activation of the immune system.

Homeostasis maintained in immunity

• Positive and negative feedback loops maintain immunity within balanced parameters.

Homeostasis Loops

• Negative feedback loops are vital in maintaining homeostasis, which prevents changes from escalating.
• Positive feedback loops are needed for specific events, such as blood clotting.

New Homeostatic Set Points

• Homeostasis, the body's dynamic equilibrium, is not static.
• New set points occur throughout physiology and pathophysiology.
• They often arise from triggers or disruptions to regulatory systems.
• Examples include Type 2 diabetes and the immune response (e.g., sepsis).

Immune Response - Sepsis

• Sepsis is an example of a disturbance in the immune system, causing a complex and poorly understood response.
• The immune response can become hyperactive (overactive) or suppressed (underactive) resulting in organ failure, death, and other problems.
• A homeostatic set point may shift in the short or long term.

Diabetes - Type 2/1

• Type 2 diabetes is characterized by a dysfunction in insulin production and glucose sensitivity.
• Type 1 diabetes is characterized by a complete loss of insulin production.
• The inability to regulate homeostasis causes significant problems.

Homeostasis and Pathophysiology

• Pathophysiology represents alterations to normal homeostasis that cannot be tolerates.
• Pathophysiology can arise from long-terms modifications or from rapid changes;
• The mechanisms in maintaining homeostasis are extremely complex and difficult to understand/regulate completely.

Principles of Physiology

• The functions of organ systems are coordinated.
• Multiple regulatory systems often have opposing effects.
• Homeostasis is crucial for well-being and survival.
• Information flow among cells, tissues, and organs is fundamental.

This quiz explores the concepts of homeostasis and its critical role in maintaining a stable internal environment necessary for human physiology. Students will learn about the importance of feedback systems and the interconnectedness of various organ systems in sustaining life. Dive into the key processes that ensure our body functions properly.