Physiology of Homeostasis and Temperature Regulation

Homeostasis

Stable internal conditions maintained by physiological systems.

Extracellular Fluid (ECF)

Fluid outside cells, includes blood plasma and interstitial fluid.

Tissues

Groups of similar cells performing specific functions.

Epithelial Tissue

Covers body surfaces and lines cavities.

Muscle Tissue

Responsible for movement in the body.

Connective Tissue

Supports, binds, and protects other tissues.

Nervous Tissue

Transmits signals for communication within the body.

Organs

Structures composed of multiple tissue types for specific functions.

Organ Systems

Groups of organs working together for a common purpose.

Multicellularity

Organism composed of multiple cells, allowing specialization.

Nervous System

Controls physiological systems by transmitting signals.

Endocrine System

Regulates physiological processes through hormone release.

Digestive Tract

Example of an organ with all four tissue types.

Cell Membrane Surface Area

Limits material exchange in single-celled organisms.

Specialization of Cells

Different cell types perform unique functions in multicellular organisms.

Nutrient Exchange

Process of cells obtaining nutrients from ECF.

Waste Elimination

Cells expel toxins into the extracellular fluid.

Physiological Systems

Mechanisms maintaining homeostasis in organisms.

Optimal Conditions

Ideal physical and biochemical states for cellular function.

Cellular Damage

Occurs when homeostasis is disrupted.

Organizational Hierarchy

Cells → Tissues → Organs → Organ Systems → Organism.

Blood Plasma

Liquid component of blood, part of ECF.

Interstitial Fluid

Fluid surrounding cells, facilitating nutrient and waste exchange.

Set point

Desired reference point for physiological regulation.

Thermostat

Device comparing current temperature to set point.

Feedback

Information compared to the set point.

Error signal

Difference between set point and feedback.

Effectors

Muscles or glands that enact changes.

Negative feedback

Counteracts deviations from the set point.

Positive feedback

Amplifies response, increasing deviation from set point.

Feedforward information

Anticipates changes, adjusting the set point.

Temperature-sensitive

Biological processes affected by temperature changes.

Antifreeze molecules

Substances preventing ice crystal formation in blood.

Denaturation

Loss of protein function due to high temperature.

Heat shock proteins (HSPs)

Proteins stabilizing others to prevent denaturation.

Survival limits

Temperature range within which cells function.

Thermoregulatory adaptations

Evolved traits for temperature regulation.

Q10

Reaction rate change per 10°C temperature difference.

Isozymes

Different enzyme forms with varying temperature optima.

Acclimatization

Adjustment to environmental temperature changes.

Metabolic rate

Rate of energy expenditure in organisms.

Geographic range

Area where a species can thrive.

Cellular damage

Harm caused by extreme temperatures.

Biochemical reactions

Processes influenced by temperature variations.

Cell Membrane Composition

Changes maintain fluidity with temperature variations.

Isozyme

Different enzyme forms adapting to temperature.

Hyperthermia

Excessive body heat requiring rapid cooling.

Heat-Induced Cramps

Muscle spasms causing exercise cessation in athletes.

Pyruvate Kinase

Enzyme inactivating at 40°C, halting ATP production.

Homeotherms

Animals maintaining a constant body temperature.

Poikilotherms

Animals with variable body temperatures.

Ectotherms

Body temperature relies on external heat sources.

Endotherms

Animals generating internal metabolic heat.

Heterotherms

Animals alternating between endothermic and ectothermic states.

Behavioral Mechanisms

Actions taken to regulate body temperature.

Radiation Heat Transfer

Heat transfer via infrared radiation between objects.

Convection Heat Exchange

Heat transfer with surrounding air or water.

Conduction Heat Transfer

Heat transfer through direct contact between objects.

Evaporation Heat Transfer

Heat loss as water evaporates from surfaces.

Energy Budget

Balance of heat production and heat exchange.

Surface Temperature Control

Regulated by blood flow to the skin.

Increased Blood Flow

Enhances heat loss, lowering body temperature.

Vasoconstriction

Reduces blood flow, decreasing heat loss.

Marine Iguanas

Alternate feeding and basking to regulate temperature.

Heart Rate Adjustment

Changes blood flow to control body heat.

Insulation

Fur retains body heat in mammals.

Heat Loss Control

Blood vessels regulate heat loss in skin.

Cold Fish

Heat lost primarily over gills during circulation.

Hot Fish

Maintain muscle temperatures 10°-15°C above water.

Peripheral Arteries

Transport cool blood, minimizing heat loss.

Countercurrent Heat Exchanger

Heat flows from arteries to veins, conserving warmth.

Metabolic Heat Production

Ectotherms raise body temperature through metabolism.

Isometric Muscle Contraction

Insects warm flight muscles before activity.

Honeybee Temperature Regulation

Group adjusts heat production for larval warmth.

Metabolic Rate Measurement

Assessed via O2 consumption or CO2 production.

Basal Metabolic Rate (BMR)

Energy use at rest in thermoneutral zone.

Metabolic Rate and Body Mass

Smaller animals have higher metabolic rates.

Surface Area to Volume Ratio

Larger animals dissipate heat less effectively.

Thermoneutral Zone

Temperature range with minimal energy use.

Critical Temperatures

Bounds of thermoneutral zone for endotherms.

Energy Use Outside Thermoneutral Zone

Increased energy required for temperature regulation.

Endothermic Response to Cold

Increased heat production and reduced heat loss.

Heat Retention Mechanism

Blood vessels adjust to maintain body temperature.

Swimming Muscle Temperature

Higher temperatures enhance fish swimming power.

Metabolic Rate Formula

Metabolic rate = Mass^3/4.

Heat Exchange in Fish

Warm blood from veins heats cool arterial blood.

Shivering heat production

Muscle contractions release heat via ATP conversion.

Thermogenin

Protein that uncouples ATP production from heat generation.

Brown fat

Fat tissue rich in mitochondria for heat production.

Endotherm adaptations

Features that minimize heat loss in warm-blooded animals.

Surface area-to-volume ratio

Smaller ratios help retain body heat.

Thermal insulation

Fur, feathers, and fat reduce heat loss.

Vasoconstriction

Narrowing blood vessels to decrease skin blood flow.

Countercurrent heat exchange

Blood flow adaptation to conserve heat in extremities.

Heat dissipation adaptations

Mechanisms to release excess heat in hot climates.

Evaporation cooling

Sweating or panting to lower body temperature.

Metabolic rate increase

Higher metabolism when exceeding upper critical temperature.

Hypothalamus

Brain region regulating body temperature and thermoregulation.

Set points

Hypothalamic temperature targets for thermoregulation.

Circadian rhythm

Daily cycle of body temperature changes.