Homeostasis and Feedback Systems Quiz

Applied Homeostasis

• Homeostasis is the state of equilibrium in the body's internal environment, maintained through constant interactions of regulatory processes.
• Homeostasis is a dynamic process, meaning the body's equilibrium can shift within a narrow range to maintain life.
• Glucose levels in blood typically remain between 70 and 110 mg/100mL.
• Body cells function optimally within such limits.
• Cellular adaptations (e.g., hypertrophy, hyperplasia, atrophy, metaplasia) adjust in response to environmental changes.
• The proper functioning of body cells depends on precisely regulating the composition of interstitial fluid.
• The blood capillaries facilitate exchange of materials between the interstitial fluid and plasma and deliver needed substances like glucose and oxygen to cells.
• Wastes (e.g. carbon dioxide) are also removed from the interstitial fluid.

Cell Theory

• Cells are the basic structural and functional units of all living organisms.
• All living organisms, unicellular or multicellular, are made up of at least one cell.
• Cells originate from pre-existing cells.

The Cell

• The human body comprises approximately 100 trillion cells.
• Cells vary in specific functions.
• Cells share basic functional characteristics like metabolism.
• Cells release by products into the surrounding medium.
• All cells can reproduce.

Tissues, Organs, and Systems

• Cells with similar functions group to form tissues.
• Various tissues combine to form organs.
• Multiple organs work together to form systems.

Internal Environment

• The interstitial fluid surrounding body cells is often called the internal environment.
• Unicellular organisms rely on the external environment.
• Multi cellular organisms maintain relative independence of the external environment.

Extracellular and intracellular fluid

• The fluid within cells is intracellular fluid (ICF).
• The fluid outside body cells is extracellular fluid (ECF), which includes plasma and interstitial fluid.
• ECF contains primarily Na+ and Cl- and lesser amounts of HCO3- in plasma.
• ICF contains mainly K+, and phosphates and protein anions.

Cell-Cell Communication

• Cells require rapid and effective communication to convey physiological information.
• Four basic mechanisms of cell-to-cell communication in the body are:
• Gap junctions
• Contact-dependent signals
• Local communication (paracrine and autocrine signals)
• Long-distance communication (chemical and electrical signals transported in the blood).

Important Characteristics of Each Cell-Cell Communication Type

• Gap junctions form cytoplasmic connections between adjacent cells, facilitating the direct transfer of electrical and chemical signals.
• Contact-dependent signals require interaction between membrane molecules on two cells, triggering signaling during immune system development and growth.
• Paracrine signaling occurs as secreted molecules diffuse through interstitial fluid to act on nearby cells.
• Autocrine signaling occurs when secreted molecules diffuse through interstitial fluid and act on cells that secrete them.
• Long-distance communication takes place via electrical signals conducted by neurons and chemical signals (hormones) transported in the blood.

Local Communications

• Chemical signals travel short distances through interstitial fluid.
• Paracrine and autocrine signals act on adjacent cells.
• Their range is limited to nearby cells.

Long-Distance Communication

• Hormones travel through the bloodstream.
• Hormones affect distant organs.
• Nervous system: Electrical and chemical signals travel to distant cells along neurons.

Cellular Signaling

• Cells respond to chemical signals by binding to specific receptors on their cell surfaces.
• The signal triggers a series of steps in the receptor cell that modifies cellular activity in a specific way.
• Ligand binding drives the receptor toward the active conformation.
• Sorting and integration of signals often involves multisteps and the activation of secondary messengers.

Homeostasis-Introduction

• Homeostasis refers to a state of equilibrium.
• Homeostasis involves the body's regulatory processes.
• Internal environmental factors like blood glucose levels can change but remain within a narrow range for optimal body functioning.

Homeostasis-Control Systems

• Feedback systems, or feedback loops, are cycles of events that monitor, evaluate, change, re-monitor, and re-evaluate a controlled condition in response to stimulus.
• The body uses feedback systems to regulate body conditions within normal limits.
• A disruption in a regulated factor is called a stimulus.
• Key components of feedback systems
• Receptors
• Control centers
• Effectors

Components of Feedback Systems

• Receptors: body sensors that detect changes associated with a stimulus.
• Control centers: integrate information from receptors and determine an appropriate response.
• Effectors. respond to the output from the control center by causing a change in the controlled condition.

Feedback System Types

• Negative feedback: negates the stimulus.
• Positive feedback: amplifies the stimulus.

Homeostatic Imbalances

• Homeostatic imbalances result in various diseases and disorders.
• Examples of conditions related to disruptions in homeostasis: cancer, infections, tissue damage are all disruptions to the internal environment of the body.
• Other factors include changes in body temperatures and presence of pollutants or toxins.

Homeostasis Model vs. Allostasis model

• Homeostasis: maintaining a constant set point, responding only to deviations from that set point.
• Allostasis: anticipating and adjusting to anticipated changes in the internal/external environment, adjusting the set point to cope with the change.
• Homeostasis is the maintenance, and Allostasis is the regulation in response to anticipated changes.

Allostasis

• Allostasis describes mechanisms that change the controlled variable by predicting what level will be needed and then overriding local feedback to meet anticipated demand.

Homeostasis vs Allostasis

• Homeostasis maintains stable internal environment.
• Allostasis regulates in response to anticipated changes, adjusting set points.

Homeostatic Mechanisms that can fail due to...

• Congenital metabolic disorders
• Ageing
• Chromosomal abnormalities
• UV radiation
• Chemical pollutants

Cellular Responses to Stress

• Adaptive responses: hypertrophy, hyperplasia, atrophy, metaplasia.
• Harmful cellular injuries: cell death (apoptosis or necrosis).

Adaptations

• Hypertrophy - increase in cell size, often due to increased workload.
• Hyperplasia - increase in cell number, sometimes triggered by hormones.
• Atrophy - decrease in cell size, often due to reduced use or decreased blood supply.
• Metaplasia - change in one cell type to another, often in response to chronic irritation.

Acclimatization

• Acclimatization refers to adaptive physiological or behavioral changes within an organism in response to their climate environment
• These changes are usually completely reversible once the stressor is removed and body reverts to the original condition.

Apoptosis

• Programmed cell death; a natural process where cells self-destruct when they are no longer needed or are a threat to the organism.
• Abnormalities of apoptosis may have a role in neurodegenerative diseases and some cancers.

Mechanism of Apoptosis

• A specific proteolytic cascade that causes cell shrinkage, cytoskeleton disassembly, and alterations in cell surface to enable phagocytic cells to attach and digest the cell.
• The process involves a specific series of steps involving enzymes and molecules.

Necrosis

• Unplanned cell death; occurs due to cell injury.
• Swelling of the organelles and an eventual rupturing of the cell membrane occur.
• The ruptured cell contents are leaked into the surrounding environment.

Biological Clock

• Internal timing mechanism that regulates physiological processes on a roughly 24-hour cycle, responding to light and darkness.
• Examples : sleep-wake cycle, hormone secretion (e.g., cortisol).

Circadian rhythm

• Internal biological clock mechanism that regulates cellular responses on a roughly 24-hour cycle, in response to light and darkness.
• Sleep-wake cycle and hormone secretion (e.g. cortisol)
• Key component : Suprachiasmatic Nucleus (SCN).

Applied Homeostasis - Blood Glucose Control

• Homeostatic control of blood glucose involves different hormones influencing the processes and maintaining normal blood glucose levels.
• Low blood glucose - Alpha cells in pancreas release glucagon stimulating glycogenolysis; resulting in higher blood glucose.
• High blood glucose - Beta cells in pancreas release insulin, resulting in blood glucose being stored in peripheral tissues.

Tutorial Questions

• These are a series of questions intended for review of learned content and/or practice
• Expect to see a diversity of content that includes basic concepts to more complex cases, likely based on the content presented in the lecture.

Biophysical Principles

• Change in pressure in a hydraulic system changes velocity of fluid movement.
• In circulatory system, the rate of blood flow is determined by the difference in pressure of the blood at the two ends of a vessel, and the resistance to blood flow through the vessel.
• Resistance is inversely proportional to the fourth power of the radius of the arterioles.
• Blood flow is determined by pressure gradient and vascular resistance.
• Laminar flow - smooth, layered flow.
• Turbulent flow - chaotic, disordered flow.
• Reynolds number determines the type of blood flow.
• Critical closing pressure: pressure below which flow ceases.
• Methods of measuring blood pressure: direct methods (cannula and manometers), indirect methods (sphygmomanometer).
• Korotkoff sounds: sounds heard during indirect blood pressure measurement; due to turbulence of the blood flow.

Biophysical Principles - Tutorial Questions

• Questions for active evaluation and practice
• The tutorial questions are provided to evaluate the student's mastery, often based on factual information presented in the lecture.

Tutorial Questions -Further Reading

• Focused questions on specific topics and their application
• These questions are provided to extend understanding and help prepare students for a range of assessment.

Blood Pressure

• Blood pressure : pressure exerted by the blood on the walls of arteries.
• Blood flow: amount of blood passing a point in circulation over time.
• Pressure gradient: difference in pressure between the two ends of a vessel, which drives the blood.
• Vascular resistance: impediment to blood flow through the vessel, impacted by the size and characteristics of the blood vessels themselves. (e.g., the radius of the vessel).
• Some terms like windkessel effect, and types of blood flow (i.e., laminar and turbulent) are explained to provide a broader understanding of the mechanics of the circulation process.

Autonomic Nervous System (ANS)

• The ANS: part of the nervous system responsible for controlling visceral functions; typically involuntary.
• There are two main subdivisions of the autonomic nervous system: • Sympathetic • Parasympathetic
• These two subdivisions function in opposition and interplay to meet the demands of the body's internal environment in activities like sleep/wake cycles, or stress/no-stress cycles.
• Higher brain centers regulate and coordinate tone and integration of the two divisions of the ANS.

Tutorial Questions - ANS

• These are a series of questions provided to evaluate understanding of specific concepts and mechanisms of a topic (i.e., the autonomic nervous system)
• Examples of question topics include homeostasis and control systems, functions of the autonomic system, and roles in response to stress or situations.

Cell Volume and Cell Signaling

• Osmolarity
• Tonicity
• Na+/K+-ATPase
• Cell-to-cell communication
• Signal pathways
• Second Messengers
• Active Transport
• Passive Transport
• Diffusion
• Osmosis

Tutorial Questions on Cell Volume and Cell Signaling

• Series of questions are designed for review and practice related to cell volume and cell signaling concepts.
• The tutorials will provide important questions and topics that cover the mechanisms, significance, and importance of biological processes.

Membrane Potential and Bioelectricity

• Bioelectricity
• Resting membrane potential
• Graded potential
• Action potential
• Types of ion channels.
• Ionic concentration (ECF vs ICF)
• Nernst equation
• GHK equation

Tutorial questions-Membrane Potential

• Questions given to help students practice and demonstrate their understanding of the presented content.
• The tutorial will encompass a series of questions about the concept of membrane potentials in excitable tissues or cells like nerve and muscle tissues.

Muscle Physiology

• Types of muscle tissue: skeletal, smooth, and cardiac muscle.
• Muscle tissues: location, function, microscopic structure, and proteins.
• Muscle contraction: isometric and isotonic contractions.
• Properties of muscle tissue: excitability, contractility, extensibility, elasticity.
• Twitch, summation, and tetanus
• Muscle fatigue: causes and mechanisms.
• Central fatigue.

Tutorial questions -Muscle Physiology

• Questions for evaluation and active learning
• These questions will often cover the content presented, ensuring knowledge of the different types of muscle and components, properties, and contraction mechanisms and related concepts.

General Tutorial Questions

• These questions are a series of general review questions that apply broad concepts and/or practical scenarios.

Test your knowledge on the principles of homeostasis and feedback systems. This quiz covers the roles of control centers, types of feedback mechanisms, and associated imbalances in various systems. Challenge yourself with questions related to the nervous and skeletal systems to enhance your understanding of physiological processes.