Bio 1106- Lesson 7

BIOL 1106: Organization of Animal Bodies and Homeostasis

Course Information

• Institution: Virginia Tech

• Department: Biological Sciences

Lesson Learning Objectives

1. Hierarchical Organization: Understand the complex hierarchy in animal bodies ranging from the molecular level (cells) to the highest level of organization (organisms).

2. Tissue Types: Identify and differentiate between the four major tissue types: epithelial, connective, muscle, and nervous tissue; describe the three primary embryonic tissue layers - ectoderm, mesoderm, and endoderm and their developmental significance.

3. Integumentary System: Describe the intricate structure and multifunctional role of the integumentary system in protecting the body and maintaining homeostasis.

4. Homeostasis: Explain the fundamental concepts of homeostasis, emphasizing the mechanisms of negative feedback and positive feedback with relevant physiological examples.

5. Temperature Regulation: Classify animals based on their temperature regulation mechanisms, contrasting endotherms and ectotherms based on their physiological adaptations.

6. Metabolic Rate: Understand the relationship between body mass and metabolic rate, including the implications for energy expenditure in different species.

Organization of Animal Bodies

Hierarchical Structure

• Multicellular Organization:

  • Structures range from simple to complex:

    • Cell > Tissue > Organ > Organ System > Organism > Population > Community > Ecosystem > Biosphere

  • Each level of organization contributes to the overall function and homeostasis of the organism.

Basic Units of Biological Organization

• Atoms > Molecules > Macromolecules > Organelles > Cells

  • Understanding these levels provides insight into how cellular processes relate to the functioning of the whole organism.

Vertebrate Body Organization

• Cells and Tissues:

  • The human body comprises approximately 210 different cell types categorized into 4 major tissue types.

  • Examples of hierarchy in organization:

    • Cardiac muscle cell > Cardiac muscle (tissue) > Heart (organ) > Circulatory system (organ system) > Whole organism.

Early Stages of Tissue Development

Gastrulation Process:

• Describes a critical phase of embryonic development involving cell shape changes and movements in the blastula, establishing the basic body plan that further differentiates into specialized tissues.

Germ Layers:

• Endoderm: Forms the inner lining of the digestive and respiratory tracts, major glands like the pancreas and liver.

• Mesoderm: Develops into bones, muscles, the circulatory system, and the dermis of skin as well as organ systems including reproductive organs.

• Ectoderm: Forms the outer layer, developing into the epidermis of skin, the nervous system, and the oral cavity lining.

Tissue Types

1. Epithelial Tissue

• General Functions:

  • Covers body surfaces, lines cavities and organs, and provides protective barriers.

  • Functions include secretion, absorption, and sensation.

• Types:

  • Classified as Simple (single layer) or Stratified (multiple layers); shapes include Squamous, Cuboidal, and Columnar.

2. Connective Tissue

• Characteristics:

  • Derived from mesoderm, composed of diverse cell types embedded within a complex extracellular matrix.

• Matrix Components:

  • Combination of ground substance (liquid, gel, or solid) and protein fibers (such as Collagen and Elastin) which provide structure and strength.

3. Muscle Tissue

• Types:

  • Smooth (involuntary muscle found in hollow organs), Skeletal (voluntary muscle responsible for movement), and Cardiac (involuntary muscle that makes up the heart).

4. Nervous Tissue

• Components:

  • Comprised of Neurons (specialized for impulse conduction) and Neuroglia (supporting cells for neurons).

• Structure includes:

  • Dendrites (receive signals), Cell body (contains the nucleus), Axons (transmit impulses), Myelin sheath (insulates axons for efficient signal conduction), Nodes of Ranvier (gaps in the myelin sheath enhancing conduction speed).

The Integumentary System

Layers:

• Epidermis: Outer protective layer, important for barrier function.

• Dermis: Contains blood vessels, nerves, hair follicles, and glands providing structural support and sensory functions.

• Subcutaneous layer (hypodermis): Contains fat deposits that provide insulation and cushioning for the underlying structures.

Accessory Organs:

• Include hair follicles, sweat glands, oil glands (sebaceous glands), and sensory receptors that facilitate interaction with the external environment.

Functions of Skin

• Protection:

  • Shields against water loss, pathogens, UV radiation, and physical damage to internal organs.

• Thermoregulation:

  • Regulates body temperature through sweat production and blood flow adjustments.

• Vitamin D Synthesis:

  • Initiated by UV exposure which is essential for calcium metabolism and bone health.

• Sensory Reception:

  • Contains sensory receptors that respond to touch, pain, and temperature.

Homeostasis

Definition

• The maintenance of stable internal conditions (temperature, pH, glucose levels, oxygen concentration) despite fluctuating external environments.

• Crucial for the survival of living organisms.

Negative Feedback Mechanism

• Components:

  • Stimulus (initial change) > Sensor (detects change) > Integrating Center (processes information) > Effector (executes response) > Response (returns to set point).

• This system works to reverse the initial change, restoring balance.

Positive Feedback Mechanism

• Example:

  • The release of Oxytocin during childbirth: Cervical stretching stimulates increased contractions, leading to more oxytocin release and further amplifying the contraction process until delivery.

Temperature Regulation

Importance of Temperature

• Temperature profoundly affects biochemical reaction rates; a 10°C increase can double the reaction rates, highlighting the importance of thermoregulation for metabolic efficiency.

Heat Transfer Methods

• Types:

  • Radiation, Conduction, Convection, Evaporation are vital mechanisms by which organisms regulate their internal temperature.

Classification of Animals:

• Endotherms: Organisms that generate heat metabolically to maintain body temperature (e.g., mammals).

• Ectotherms: Organisms that rely on environmental heat sources, affecting their activity levels and metabolic rates (e.g., reptiles).

Body Mass and Metabolic Rate

Relationship

• Investigating metabolic rates across mammals reveals a correlation where as body mass increases, metabolic rate exhibits allometric scaling, indicated as mass-specific metabolic rate.

• Graphical Representation:

  • Illustrates variations in metabolic rate among various species providing insights into evolutionary adaptations and energy requirements (e.g., Shrew, Mouse, Cat, Horse, Elephant).

Upcoming Topic

• Next Lecture Focus: The Organization of the Nervous System, exploring its complexity and vital role in the functioning of animal bodies.