Anatomy 2 Review

Overview of Anatomy & Physiology

Anatomy

Anatomy is the study of body structures, which includes understanding organs, tissues, and cells. It can be divided into several categories:

• Gross Anatomy: Examines structures that can be seen with the naked eye, such as organs and systems.

• Microscopic Anatomy: Involves histology, the study of tissues, and cytology, the study of cells.

• Comparative Anatomy: Compares anatomical structures between different species to understand evolutionary relationships.

Physiology

Physiology investigates the functions and activities of life. It studies the physical and chemical processes that take place within living organisms, involving multiple levels of organization, from cellular to whole-body systems. Physiologists analyze how every system works and interacts with other systems within the body.

• Cellular Physiology: Focuses on the functions of cells and their components.

• Systemic Physiology: Examines how specific organ systems operate, such as the cardiovascular system.

Key Principle

The key principle in anatomy and physiology is that structure determines function. This means that the shape and structure of an anatomical part directly influence its function.

Key Physiological Concepts

Conformity vs. Regulation

• Conformers: These organisms have internal environments that change with external environments. For instance, ectotherms like reptiles have body temperatures that vary with their surroundings.

• Regulators: These organisms maintain stable internal conditions regardless of external changes. Homeotherms like birds and mammals regulate their body temperatures to keep them constant despite variations in environmental temperatures.

Homeostasis

Homeostasis is the body’s ability to maintain a stable internal environment under varying external conditions. This involves complex feedback systems capable of adjusting physiological processes to promote stability.

Integration of Body Systems

Different organ systems work together to ensure overall function and stability. For example, the respiratory, cardiovascular, and muscular systems cooperate during physical activity to provide adequate oxygen to tissues.

Regulation of Internal Environment

Fluid Compartments of the Body

1. Intracellular Fluid (ICF): Fluid found within cells, which constitutes a significant proportion of body fluid.

2. Extracellular Fluid (ECF): Fluid located outside cells, further divided into:

   • Interstitial Fluid (ISF): Surrounds and nourishes tissues.

   • Intravascular Fluid (IVF): Blood plasma, which transports nutrients and waste products.

Homeostasis & Regulation Mechanisms

Feedback Loops

Feedback mechanisms are vital for maintaining internal stability:

• Negative Feedback: Restores balance by reversing a change. Examples include hormone regulation where insulin lowers blood glucose levels, blood pressure regulation to maintain optimal levels, and calcium homeostasis involving parathyroid hormone and calcitonin.

• Positive Feedback: Amplifies a change within a system. Examples include childbirth where oxytocin increases uterine contractions, and blood clotting, where platelets release chemicals to recruit more platelets, enhancing the clotting process.

Thermoregulation & Hypothalamus Role

The hypothalamus plays a crucial role in thermoregulation by regulating body temperature:

• Cooling the Hypothalamus: Blood vessels constrict to reduce heat loss, and metabolic rate can increase to generate additional heat.

• Warming the Hypothalamus: Blood vessels dilate to release excess heat, and sweating increases for evaporative cooling to help lower body temperature.

Physiological Adaptations & Changes

Types of Physiological Changes

1. Acute Changes: Immediate responses to environmental changes (e.g., increased heart rate during exercise). These changes are often short-term and reversible.

2. Chronic Changes (Acclimation & Acclimatization): Longer-term physiological adaptations that occur over days to months due to changes in conditions (e.g., increased red blood cell production at high altitudes). This process can be reversible but may last longer than acute changes.

3. Evolutionary Changes: Permanent adaptations resulting from natural selection over generations (e.g., larger lung capacity in populations adapted to high altitudes).

4. Developmental Changes: These are programmed changes that occur from conception to adulthood (e.g., hormonal changes during puberty).

5. Biological Clocks: Cyclical physiological changes in organisms, including circadian rhythms that govern sleep-wake cycles and seasonal breeding patterns in certain species.

Principles of Physiology

Structure & Function Relationship

Molecular Level

The shape of molecules can determine their function. An example is Sickle-Cell Anemia, where a mutation in hemoglobin alters the shape of red blood cells, leading to reduced oxygen delivery and causing blockages in small blood vessels.

Tissue & Organ Level

Analyzing the layers of the stomach wall provides insight into the relationship between structure and function:

• Epithelial cells for secretion and absorption.

• Connective tissue for structural support.

• Smooth muscle for movement and mechanical digestion.

• Neurons to regulate and coordinate digestive processes.

Physiological Regulation

Autoregulation of Iodine & Thyroid Hormones

Iodine is essential for the production of thyroid hormones, which play critical roles in regulating metabolism and promoting healthy growth. The transport of iodine into thyroid cells is crucial for maintaining these functions.

Electrical Properties

The existence of membrane potentials creates electrical signals critical for coordination in the body. Excitable cells, such as neurons and muscle cells, rely on action potentials to transmit signals and trigger responses.

Blood Flow & Pressure Regulation

Blood flow and pressure are regulated by the resistance found in blood vessels, which is described by Poiseuille's Law, stating that flow is proportional to the vessel’s radius. Changes in vessel diameter can significantly alter blood flow and pressure, influencing overall circulatory dynamics.

Oxygen Regulation & Acclimatization

Effects of High Altitude on Oxygen Availability

At high altitudes, the partial pressure of oxygen (PO2) decreases significantly:

• Sea Level PO2: Approximately 159-160 mmHg.

• High Altitude PO2: Can drop to 92 mmHg or lower, leading to conditions like hypoxia (low oxygen levels).

Body Senses Hypoxia and Responds

The body detects hypoxia and initiates responses, including increasing red blood cell production through the release of Erythropoietin (EPO), which enhances the oxygen-carrying capacity of the blood and improves oxygen delivery to tissues.

Erythropoiesis (RBC Production) & Regulation

Erythropoietin (EPO) is released by the kidneys under specific conditions:

• When the red blood cell count decreases.

• When oxygen levels drop.

• In response to increased tissue oxygen demand.Effects of EPO include stimulating red bone marrow to produce more red blood cells.

Evolution & Physiology

Adaptations & Natural Selection

Physiological adaptations are crucial for the survival of organisms in various environments. Evolutionary change involves:

• Genetic Variation among individuals within a population, allowing for diversity in traits.

• Increased Fitness, which boosts individual reproductive success.

• Environmental Influence, where natural selection determines which traits are beneficial and therefore preserved.For example, Arctic animals have developed thicker fur and additional fat layers as adaptations to conserve heat in extreme cold.

Common Evolutionary Traits

Organisms with shared ancestry may exhibit similar physiological features, demonstrating evolutionary links and relationships.

• Diversity in Adaptations: Different environments lead to unique physiological strategies adapted for specific survival scenarios.

Phenotypic Plasticity & Environmental Influence

Genotype vs. Phenotype

• Genotype refers to the genetic makeup of an organism, determining its inherited characteristics.

• Phenotype is the observable traits influenced by both genetics and environmental conditions.

• Phenomics is the extensive study of how genetic variations translate into observable physical traits.

Types of Phenotypic Plasticity

• Reversible Plasticity includes acclimation (changes that can be induced in a lab setting) and acclimatization (natural adaptations).

• Irreversible Plasticity includes developmental changes known as polyphenism, where specific traits can be permanently altered based on environmental factors; for example, butterflies can exhibit seasonal wing color changes.

Heat Acclimation in Humans

In a study involving 24 men exercising in hot, dry air (49°C, 20% humidity):

• Day 1 (Acute Response): Participants demonstrated low endurance levels.

• After 1 Week (Chronic Response): There was a significant increase in endurance. This adaptation was reversible, as it could fade if exposure to heat ceased.

Summary

Anatomy and physiology explore the structure and function of organisms critically, with homeostasis and regulation mechanisms ensuring internal stability. Various physiological adaptations occur over different time scales (acute, chronic, evolutionary), and understanding oxygen transport and erythropoiesis is vital for survival at high altitudes. Evolution shapes physiology through natural selection, illustrating common ancestry, adaptations, and how phenotypic plasticity allows organisms to adjust effectively to changing environmental conditions.