Animal Bodies and Homeostasis

Animal Bodies and Homeostasis Part 1

Objectives for Today

• Describe the different tissue types found in animal bodies.

• Explain the differences between tissues and organs.

• Investigate how animals move substances at the cellular level.

• Understand how and why animals maintain homeostasis.

• Examine how animals regulate their body temperatures.

• Differentiate between ectotherms and endotherms.

Animal Tissues

• Tissue: An association of specialized cells that have a similar structure and function.

  • 4 main types of tissues:

  • Muscle Tissue

  • Nervous Tissue

  • Epithelial Tissue

  • Connective Tissue

Muscle Tissue

• Muscle Tissue: Consists of cells that can shorten or contract, which leads to several functions:

  • Produce body movements.

  • Decrease the diameters of tubes (e.g., blood vessels).

  • Exert pressure on fluid-filled cavities.

Types of Muscle Tissue

1. Skeletal Muscle:

   • Usually linked to bones via tendons (or to an exoskeleton).

   • Most is under voluntary control.

   • Contract when stimulated by signals from the motor neurons.

2. Smooth Muscle:

   • Surrounds hollow tubes and cavities within the body (e.g., intestines).

   • Contraction and relaxation push fluids through these tubes.

   • Generally involuntary control.

3. Cardiac Muscle:

   • Composed of interconnected cells that contract and relax in unison, forming the heart.

   • Control is involuntary.

   • Key Components:

     • Atrial musculature: Muscles responsible for contractile action in the heart's atria (upper chambers).

     • Ventricular musculature: Muscles involved in the heart's ventricular contractions (lower chambers).

Nervous Tissue

• Nervous Tissue: Composed of cells called neurons.

  • Function: Initiate and conduct electrical signals throughout the body.

  • Function: Stimulate or suppress various activities within the body, facilitating communication between body parts.

Epithelial Tissue

• Epithelium: Tissue that covers the body or lines walls of organs. Its characteristics include:

  • Composed of sheets of densely packed cells.

  • Protects organs and the body’s surface.

  • Functions include secretion and transport of ions or organic molecules.

  • Polar Cells: These cells have one side connected to the basal lamina (the underlying layer of support).

Connective Tissues

• Connective Tissues: These serve multiple functions, including connecting, supporting, surrounding, and anchoring different body structures. Examples include:

  • Adipose Tissue: Stores fat and provides insulation.

  • Bone: Provides structure and support.

  • Cartilage: Flexible support within joints.

  • Blood: Connective tissue that transports nutrients and waste throughout the body.

Organ Systems

• Organs: Structures composed of two or more types of tissues working together. Examples include:

  • Lumen of stomach: The cavity within the stomach.

  • Components within an organ:

  • Layers of muscle tissue

  • Simple columnar epithelial tissue

  • Connective tissue

  • Nervous tissue

  • Simple squamous epithelial tissue

• Organ System: A group of organs that work together to accomplish a specific task. Examples of organ systems include:

  • Salivary glands, pharynx, liver, gallbladder, small intestine, large intestine, mouth, esophagus, stomach, pancreas, anus.

Transport at the Cellular Level

• Movement of substances: Occurs down their concentration gradients from areas of high concentration to lower concentration.

  • Osmosis: The movement of water down its concentration gradient, crucial for transport across and between tissues.

Mechanisms of Transport

• Ways substances move in and out of cells:

  • Passive diffusion: Movement of small, uncharged molecules through cell membranes without energy input.

  • Facilitated diffusion: Involves surface proteins that create channels, allowing substances to diffuse more quickly.

  • Active transport: Requires energy to move specific molecules, typically against their concentration gradient.

Animal Bodies and Homeostasis Part 2

Homeostasis

• Homeostasis: The maintenance of a stable internal environment within a narrow range of parameters crucial for survival.

  • Conformers: Organisms that match their internal parameters to external environmental conditions (e.g., freshwater fish maintain specific ion concentrations).

  • Regulators: Organisms that maintain internal parameters that differ from external conditions.

Active Homeostasis Maintenance

• Maintenance of homeostasis is an active process requiring constant adjustments.

  • Physiological variables are kept within strict ranges but may also fluctuate based on the organism's needs.

  • Compensatory Mechanisms: These restore variables to normal ranges when deviations occur.

Example: Control of Blood Sugar Levels

• Regulation example involving blood sugar:

  • High blood sugar stimulates insulin release.

  • Insulin function:

  • Stimulates glucose uptake by cells.

  • Promotes glycogen breakdown in the liver.

  • Low blood sugar promotes glucagon release:

  • Stimulates glycogen formation in the liver.

Homeostatic Control Systems

• Components of a Homeostatic Control System:

  • Set Point: The normal desired range for a variable.

  • Sensor: Monitors the level of the variable.

  • Integrator: Compares the monitored signal to the set point.

  • Effector: Adjusts the variable back to the set point.

Feedback Mechanisms

• Negative Feedback: A physiological response to a change in the variable being regulated that moves the variable in the opposite direction towards the set point.

• Feedforward Regulation: A proactive system where the body prepares for changes before they occur.

Homeostasis: Regulation of Body Temperature

• Optimal body temperature is critical; extremes can disrupt physiological functioning:

  • High Temperatures:

  • Proteins denature, losing function.

  • Accelerates reaction rates too fast.

  • Cell membranes may leak.

  • Low Temperatures:

  • Reaction rates become too slow.

  • Cell membranes become rigid.

Metabolic Rate

• Metabolic Rate: The amount of energy an organism uses over time, essential for various activities including:

  • Movement, active transport, and cellular functions.

  • Some energy is lost as heat.

• Basal Metabolic Rate: The rate of energy usage under controlled resting conditions.

Ectotherms vs. Endotherms

• Endotherms: Maintain body temperature primarily through metabolic processes, often keeping a constant internal temperature.

• Ectotherms: Regulate body temperature largely through behavioral adaptations, relying on external environmental conditions.

Heat Exchange Mechanisms

• Heat Exchange occurs in four ways:

  • Radiation: Loss or gain of heat via electromagnetic waves.

  • Evaporation: Heat loss through the transformation of liquid water to vapor, cooling the body.

  • Conduction: Heat loss or gain through direct contact with a surface.

  • Convection: Heat transfer by the movement of fluids or air adjacent to the body's surface.

Behavioral and Physiological Temperature Regulation

• Manipulating heat exchange:

  • Changes in blood flow near the skin (dilation/contraction) to manage heat loss or retention during temperature fluctuations.

  • Use of countercurrent exchange to conserve heat, particularly in extremities.

  • Evaporative cooling mechanisms: E.g., panting and sweating.

  • Behavioral adaptations include seeking shade, water splashing, ruffling fur/feathers, and cuddling.

Shivering Thermogenesis

• Shivering Thermogenesis: A mechanism for warmth where rapid contractions of skeletal muscles generate heat, redirecting energy usually used for movement towards thermoregulation.