Homeostasis and Chemical Structure in Human Physiology

Homeostasis

HUBS 1401 - Biomedical Science Part 1

Learning Outcomes

  • Name the 6 levels of structural organization within the human body and explain their interrelations.

  • Recognize the 11 body systems and their major functions.

  • Understand the communication and cooperation among body systems to achieve normal functionality.

  • Define homeostasis and explain its significance to survival.

  • Identify the elements of a homeostatic control system and the role of each element.

  • Define negative feedback and discuss its role in maintaining homeostasis.

Complexity & Levels of Organization

Levels of Structural Organization

  1. Chemical Level    - Atoms (e.g., C, H, O, N, P)    - Molecules (e.g., DNA)

  2. Cellular Level    - E.g., Smooth muscle cell

  3. Tissue Level    - E.g., Smooth muscle tissue

  4. Organ Level    - E.g., Stomach, liver, intestines, etc.

  5. System Level    - E.g., Digestive system

  6. Organismal Level    - E.g., The entire human body

Human Body Systems

  • Respiratory System

  • Reproductive System

  • Integumentary System

  • Urinary System

  • Skeletal System

  • Digestive System

  • Nervous System

  • Lymphatic System

  • Endocrine System

  • Circulatory System

  • Muscular System

Integration of Body Systems

  • The body’s systems work together, wherein the interiors of some hollow organs are part of the external environment.

  • Communication is vital between systems:    - Integumentary System    - Circulatory System    - Digestive System    - Respiratory System    - Nervous System    - Endocrine System    - Urinary System    - Musculoskeletal System    - Reproductive System

Homeostasis

Definition and Significance

  • Homeostasis refers to maintaining a stable internal environment essential for survival.

  • Examples:    - Blood pH: Approximately 7.4    - Body Temperature: Approximately 37°C

  • Achieved by balancing inputs and outputs of various body systems.

Balancing Inputs & Outputs

  • Involves various body systems continuously regulating physiological parameters.

Homeostatic Regulation

  • Involves the nervous and endocrine systems, which can act together or independently.

  • Regulation through Negative Feedback:    - Adjustments in physiological systems in response to stimuli through feedback mechanisms.

Components of Homeostatic Control

  1. Receptor (Sensor):    - Monitors a physiological variable and detects changes.

  2. Control Centre:    - Integrates information and compares monitored values with acceptable ranges.

  3. Effector:    - Returns the monitored variable to within normal limits.

Temperature/homeostasis Examples

Thermoregulation

  • Normal Internal Temperature: Approximately 36-38°C.

  • Mechanisms:    - Temperature rises:      - Thermoregulation center activated, triggering sweat glands to cool the body through evaporation.      - Blood vessels dilate, allowing heat to escape.    - Temperature falls:      - Thermoregulation center again activated, causing shivering which generates heat.      - Blood vessels constrict to minimize heat loss.

Regulation of Glucose Levels

  • Low Blood Glucose:    - Pancreas releases glucagon (from alpha cells) leading to liver action to normalize levels.

  • High Blood Glucose:    - Pancreas releases insulin (from beta cells) to promote uptake in fat cells.

Negative Feedback Control

  • Regulated Variables:    - Core Body Temperature: 37°C    - Blood pH: 7.35-7.45    - Potassium Levels: 3.5-5.0 mmol/L    - Calcium Levels: 2.2-2.7 mmol/L    - Blood Glucose: 70-110 mg/dl    - Blood Volume: 5 L    - Mean Arterial Pressure: 93 mmHg    - Oxygen and Carbon Dioxide Levels: Various ranges.

Consequences Of Homeostatic Failure

  • Physiological parameters may drift

  • Can lead to disease affecting tissues, organs, or systems.

  • May result in systemic changes throughout the body and culminate in death.

Summary

  1. Structural Organization Levels: Six distinct levels from atoms to whole organisms.

  2. Organ Systems: Eleven systems with various vital functions, interconnected and integrated.

  3. Homeostasis: Crucial for maintaining a stable internal environment achieved through inputs/outputs and specific regulatory mechanisms.

  4. Components: Include receptors, control centers, and effectors.

Chemical Level of Organisation

Atoms & Molecules

Learning Outcomes

  • Define element and list the four primary elements that constitute body matter.

  • Explain the relationship between elements and atoms.

  • Describe atomic structure, including subatomic particles, their masses, charges, and positions.

  • Discuss radioisotopes and their medical applications.

  • Elucidate atomic stability/reactivity; differentiation between ions and their formation.

  • Contrast ionic, polar covalent, nonpolar covalent bonds; significance of hydrogen bonds.

  • Explain the importance of reactivity in life; define molarity; measure concentrations of atoms and molecules.

Definition of Matter

  • Anything that occupies space and has mass; exists in three states:    - Solid    - Liquid    - Gas

Importance of Elements in Matter

  • Composed of unique substances known as elements (e.g., carbon, oxygen) that cannot be decomposed by chemical means.

  • The human body primarily includes 26 elements.

Periodic Table Structure

  • Arranged by increasing atomic numbers; symbols are based on English or Latin names.

Key Elements in the Human Body

  • Hydrogen (H), Carbon (C), Nitrogen (N), Oxygen (O), Phosphorus (P), Sulphur (S), etc.

Atoms

  • Smallest component of an element retaining the properties of that element.

  • Unique properties due to subatomic particles:   - Protons (p+), Neutrons (n°), Electrons (e¯)

Subatomic Particles

  • Nucleus: Contains protons (charge +1) and neutrons (charge 0).

  • Electron Shells: Electrons orbit the nucleus (charge -1).   - Example: Carbon atom has 6 protons, 6 neutrons, and 6 electrons.

Atomic Number and Weight

  • Atomic Number: Number of protons in the atom.

  • Atomic Weight: Total number of particles in the nucleus (protons + neutrons).

Isotopes

  • Different atomic forms of the same element with varying neutrons.   - Example: Deuterium (2H^{2}H) and Tritium (3H^{3}H) of hydrogen.

  • Some isotopes are radioactive, useful in science and medicine.

Reactivity of Atoms

  • Atoms desire stability, achieved by filling outer electron shells:   - Complete Shell: Stable and unreactive.   - Incomplete Shell: Unstable and reactive.

Methods for Stability

  1. Transfer: Gain, lose or share electrons.

  2. Ion Formation: Creation of charged particles leading to ionic bonds.

Ionic Bonds

  • Formed by electrical attractions between cations (positive ions) and anions (negative ions):    - Cations: Electron donors.    - Anions: Electron acceptors.

Electrolytes

  • Substances like sodium chloride ( ext{NaCl}) that dissociate in body fluid crucial for muscle and nerve function.

  • Concentration balance is vital for maintaining physiological functions.

Chemical Bonds

Types of Bonds

  1. Ionic Bonds: Attraction between charged ions.

  2. Covalent Bonds: Result from sharing electrons (e.g., water molecule, H2OH_2O).

  3. Hydrogen Bonds: Occur between polar molecules, crucial for water’s properties.

Organic Compounds

Overview

  • Typically large, organic compounds contain carbon and include:   - Carbohydrates   - Lipids   - Proteins   - Nucleic Acids   - Adenosine Triphosphate (ATP)

  • Most organic molecules are polymers made from monomer units.

Carbohydrates

  • Comprise carbon, hydrogen, and oxygen, abbreviated as CHO.

  • Categories: Monosaccharides, disaccharides, polysaccharides.

  • Functions include energy sources and structural roles in nucleic acids.

Lipids

  • Composed of fats, oils, and sterols, generally insoluble in water.

  • Defined by their structure and extensive energy storage capacity.