Comprehensive Study Guide: Human Anatomy & Physiology II (BIOL 2402) Final Exam Review

Introduction to Homeostasis and Feedback Mechanisms

Homeostasis

Homeostasis is the maintenance of a stable internal environment within the body, despite changes in the external environment. It is essential for the survival and proper functioning of cells and organs.

• Homeostatic Imbalance: A disturbance in homeostasis, which can lead to disease or dysfunction.

Feedback Mechanisms

• Negative Feedback: The most common mechanism; it reduces or shuts off the original stimulus. Example: Regulation of body temperature, blood glucose by insulin.

• Positive Feedback: Enhances or amplifies the original stimulus. Example: Blood clotting, labor contractions.

• Systems Involved:

  • Nervous System: Fast, short-lived, targets specific cells (muscle fibers, glands).

  • Endocrine System: Slower, longer-lasting, targets cells throughout the body.

Endocrine System

Hormonal Regulation

• Parathyroid Hormone (PTH): Increases blood calcium by stimulating bone resorption and increasing calcium absorption in the GI tract.

• Insulin: Secreted by the pancreas in response to high blood glucose; lowers blood glucose by promoting cellular uptake.

• Growth Hormone (GH): Stimulates protein synthesis and growth, especially in bones and muscles.

• Adrenocorticotropic Hormone (ACTH): Stimulates the adrenal cortex to release corticosteroid hormones.

Feedback Mechanisms in Endocrine Regulation

• Neural Messages: Fast, direct control (e.g., adrenal medulla release of epinephrine).

• Chemical Messages: Hormones act as chemical messengers in feedback loops.

Hormones and Receptors

• Protein Hormones: Act via second messengers (e.g., cAMP).

• Hormone Receptors: Cells must have specific receptors to respond to a hormone.

• Types of Glands:

  • Endocrine: Ductless, secrete hormones into blood.

  • Exocrine: Secrete products via ducts (e.g., sweat, digestive enzymes).

• Hormone Definition: Chemical messenger secreted by endocrine glands, transported by blood to target organs.

• Hormonal Receptors:

  • Membrane-bound: Bind amino acid-based hormones.

  • Intracellular: Bind steroid hormones.

Insulin & Glucagon

• Secreted by: Pancreatic islets (Islets of Langerhans).

• Insulin: Released when blood glucose is high; lowers glucose.

• Glucagon: Released when blood glucose is low; raises glucose.

Digestive System and Metabolism

Anatomy and Function

• Small Intestine: Main site of nutrient absorption; villi and microvilli increase surface area.

• GI Tract Layers:

  • Mucosa: Absorption and secretion.

  • Submucosa: Blood vessels, nerves, glands.

  • Muscularis Externa: Smooth muscle for peristalsis.

  • Serosa: Outermost layer, attaches organs to body wall.

• Deglutition: Swallowing; involves mouth, pharynx, esophagus (not pylorus).

• Mastication: Chewing; mechanical breakdown of food.

Chemical Digestion and Metabolism

• Catabolism: Breakdown of large molecules into smaller ones (e.g., digestion).

• Glycolysis: Anaerobic breakdown of glucose to pyruvic acid; produces 2 ATP per glucose.

• Gluconeogenesis: Formation of glucose from non-carbohydrate sources; raises blood glucose.

• Glycogenolysis: Breakdown of glycogen to glucose.

Enzymes

• Definition: Biological catalysts that speed up reactions without being consumed.

Nutrient Absorption and Metabolism

• Small Intestine: Primary site for absorption of nutrients.

• Bile Production: Hepatocytes in the liver produce bile for fat emulsification.

• Krebs Cycle & Electron Transport Chain: Aerobic stages of glucose catabolism; require oxygen.

Endocrine Functions Related to Digestion

• Pineal Gland: Produces melatonin, regulates sleep cycles.

• Thymosin: Produced by thymus; important for T-cell development.

• Epinephrine: Adrenal medulla hormone; triggers fight-or-flight response.

Additional Digestive Concepts

• Peristalsis: Wave-like muscle contractions that move food through the GI tract.

• Pancreatic Enzymes: Bicarbonate-rich juices secreted into the duodenum.

• Anabolic vs. Catabolic Reactions: Anabolic builds molecules; catabolic breaks them down.

Six Essential Activities of Digestion

1. Ingestion

2. Propulsion (including peristalsis)

3. Mechanical breakdown (mastication, churning)

4. Chemical digestion

5. Absorption

6. Defecation

Peritoneum and Related Terms

• Peritoneum: Serous membrane lining the abdominal cavity and covering abdominal organs.

• Visceral Peritoneum: Covers organs.

• Parietal Peritoneum: Lines cavity wall.

Metabolism and ATP

• Anabolism: Synthesis of complex molecules from simpler ones.

• Catabolism: Breakdown of complex molecules.

• ATP (Adenosine Triphosphate): Main energy currency of the cell.

• ATP Yield:

  • Glycolysis: $2$ ATP per glucose

  • Glycolysis + Krebs Cycle + ETC: $36-38$ ATP per glucose

• Oxygen: Required for electron transport chain; CO2 is produced during Krebs cycle.

Absorptive vs. Post-Absorptive State

• Absorptive State: Nutrients are being absorbed; insulin dominates.

• Post-Absorptive State: Fasting; glucagon dominates.

Respiratory System

Mechanics of Breathing

• Diaphragm & Intercostal Muscles: Contract to increase thoracic volume during inspiration.

• Intrapulmonary vs. Atmospheric Pressure: Air flows from high to low pressure.

Gas Exchange

• Alveoli: Main site of gas exchange.

• External Respiration: Gas exchange between alveoli and blood.

• Internal Respiration: Gas exchange between blood and tissues.

• Factors Affecting Gas Exchange: Partial pressures, solubility of gases.

Respiratory Regulation

• CO2 and O2: CO2 is the main driver of breathing rate.

• Respiratory Centers: Located in the brainstem (medulla, pons).

Respiratory Physiology

• Inspiration: Diaphragm contracts, thoracic cavity expands, air flows in.

• Expiration: Diaphragm relaxes, thoracic cavity decreases, air flows out.

• Gas Transport:

  • Oxygen: Mostly bound to hemoglobin; high partial pressure in lungs, low in tissues.

  • CO2: Transported as bicarbonate, dissolved in plasma, or bound to hemoglobin; high partial pressure in tissues, low in lungs.

• Exercise: Increases respiratory rate and gas exchange.

Four Processes of Respiration

1. Pulmonary Ventilation

2. External Respiration

3. Transport of Gases

4. Internal Respiration

Cardiovascular System

Heart Anatomy and Function

• Chambers: Right/left atria (receive blood), right/left ventricles (pump blood).

• Valves: Tricuspid, bicuspid (mitral), semilunar; prevent backflow.

• Cardiac Cycle: Systole (contraction), diastole (relaxation).

Blood Vessels

• Arteries: Carry blood away from heart; thick walls.

• Veins: Carry blood to heart; thinner walls, valves.

• Capillaries: Exchange vessels; thin walls.

• Pulmonary Circuit: Heart to lungs and back.

• Systemic Circuit: Heart to body and back.

Blood Flow Pathway

• Right atrium → right ventricle → pulmonary arteries → lungs → pulmonary veins → left atrium → left ventricle → aorta → body

Blood Pressure and Pulse

• Blood Pressure: Force of blood against vessel walls; measured as systolic/diastolic (e.g., 120/80 mmHg).

• Pulse: Rhythmic expansion of arteries with each heartbeat.

Blood Composition

• Plasma: Liquid component (~55%).

• Formed Elements:

  • Erythrocytes (RBCs): Transport oxygen.

  • Leukocytes (WBCs): Immune defense.

  • Thrombocytes (Platelets): Blood clotting.

Blood Types and Compatibility

• ABO System: Based on presence of A and B antigens (agglutinogens) on RBCs.

• Rh Factor: Presence (+) or absence (−) of Rh antigen.

• Agglutinogens: Antigens on RBCs.

• Agglutinins: Antibodies in plasma.

Blood Type	Agglutinogens (Antigens)	Agglutinins (Antibodies)
A	A	Anti-B
B	B	Anti-A
AB	A, B	None
O	None	Anti-A, Anti-B

Urinary System

General Components and Functions

• Kidneys: Filter blood, form urine, regulate pH, electrolytes, and blood pressure.

• Ureters: Transport urine to bladder.

• Bladder: Stores urine.

• Urethra: Excretes urine.

Nephron Structure

• Renal Corpuscle: Glomerulus (capillary tuft) + glomerular capsule.

• Renal Tubule: Proximal convoluted tubule, nephron loop (loop of Henle), distal convoluted tubule.

Filtrate vs. Urine

• Filtrate: Fluid filtered from blood in glomerulus; becomes urine after modification.

Urine Formation Steps

1. Glomerular Filtration

2. Tubular Reabsorption

3. Tubular Secretion

Filtration Pressures

• Blood Osmotic Pressure: Draws water back into glomerulus.

• Capsular Hydrostatic Pressure: Opposes filtration.

• Glomerular Hydrostatic Pressure: Promotes filtration; higher due to afferent/efferent arteriole size difference.

Net Filtration Pressure (NFP)

• Calculated as the sum of forces favoring and opposing filtration.

• Equation: $NFP = (Glomerular\ Hydrostatic\ Pressure) - (Blood\ Osmotic\ Pressure + Capsular\ Hydrostatic\ Pressure)$

Glomerular Filtration Rate (GFR)

• Volume of filtrate formed per minute; decreases after blood loss.

• Regulated by the juxtaglomerular complex.

Urine Pathway and Peristalsis

• Renal pelvis → ureter → bladder → urethra.

• Peristalsis moves urine through ureters.

Bodily pH Control

• Buffer Systems: Immediate response.

• Respiratory Rate: Rapid adjustment.

• Renal Excretion: Slow, long-term control.

Erythropoietin

• Hormone from kidneys; stimulates RBC production.

Lymphatic and Immune Systems

Lymphatic System

• Lymph Flow: Enters lymph nodes via afferent vessels, exits via efferent vessels.

• Organs:

  • Spleen: Removes old RBCs.

  • Thymus: T cell maturation.

Immune System

• Three Main Parts: Lymphatics, lymph, lymph nodes.

• Innate Defenses:

  • First Line: Skin, mucous membranes.

  • Second Line: Phagocytes, NK cells, inflammation, antimicrobial proteins, fever.

• Adaptive Defenses:

  • Humoral: B cells produce antibodies (extracellular targets).

  • Cellular: T cells target infected cells directly or indirectly.

• Antigen: Substance that triggers an immune response.

• Complement System: Promotes phagocytosis, agglutination, precipitation, neutralization, and complement activation.

• Macrophage Presentation: Presents antigens to naive CD4 or CD8 T cells.

• Inflammation: Histamine release stimulates inflammation; chemotaxis attracts neutrophils/macrophages.

• Antibody Production: Plasma cells produce antibodies.

• Antigen Presentation: Macrophages activate T cells in lymph nodes.

• Cell-Mediated Immunity: Cytotoxic T cells destroy infected cells.

• Thymus Gland: Programs cytotoxic T cell precursors.

• Interferon: Released in response to viral infection.

• HIV: Targets and destroys helper T cells.

• Memory Cells: Enable faster, stronger response upon re-exposure to the same antigen.