SBI 3U1 Internal Systems Practice Flashcards

Overview of Internal Systems and Biological Organization

• The human body contains $11$ organ systems. This unit focuses on three primary systems:

  • Circulatory System: Transports blood, nutrients, gases, and wastes.

  • Digestive System: Takes in food, breaks it down, absorbs nutrients, and removes solid waste.

  • Respiratory System: Controls breathing and exchanges gases in the lungs.

• Other human organ systems include:

  • Excretory System: Removes liquid wastes from the body.

  • Immune System: Defends the body against infections.

  • Muscular System: Works with bones to move parts of the body.

  • Endocrine System: Manufactures and releases hormones to keep body systems in balance.

  • Reproductive System: Includes organs for producing offspring.

  • Integumentary System (pronounced in-TEG-u-MEN-tar-ee): Includes skin, hair, and nails; creates a waterproof barrier.

  • Nervous System: Detects environmental changes and signals the body to respond.

  • Skeletal System: Supports, protects, and works with muscles for movement.

• Levels of Biological Organization: Living things follow a hierarchy from atoms to the biosphere:

  • Subcellular (Nonliving) Levels: Atom → Molecule → Organelle.

  • Cellular (Living) Levels: Cell → Tissue → Organ → Organ System → Organism (Individual) → Population → Community → Ecosystem → Biome → Biosphere.

Nutrition and Macromolecules

• Nutrient: Any substance with a useful function when taken up by body cells. The body requires $6$ essential nutrients: carbohydrates, proteins, fats, water, vitamins, and minerals.

• Macronutrient: Needed in large amounts daily. Includes carbohydrates, fats, and proteins (macromolecules).

• Micronutrient: Needed in small quantities daily. Deficiency leads to deficiency diseases (e.g., Scurvy from lack of Vitamin C). Includes vitamins and minerals.

• Essential Nutrients: Must be obtained from the diet because the body cannot synthesize them (e.g., certain amino acids and fatty acids).

• Vitamins:

  • Water Soluble: Dissolve in water, carried to tissues but not stored; excreted via urine. Examples: Vitamins $B$ and $C$.

  • Fat Soluble: Absorbed with dietary fats, stored in liver and fat reserves; not excreted. Examples: Vitamins $A, D, E, K$.

• Minerals: Inorganic elements needed in small amounts for body functioning. Examples: calcium, iron, phosphorus.

• Water: Not an energy source but makes up most of the body (plasma, extracellular fluid). Functions include regulating temperature, moistening air for lungs, and enabling chemical reactions. Requirement: $1-1.5\,L$ daily to replace losses.

• Macromolecules: Extremely large molecules of high molecular weight. Most are polymers (long chains of repeating subunits) made of monomers (smallest subunits).

  • Carbohydrates:

    • Monomers: Monosaccharides ($C, H, O$) such as Glucose, Fructose, Galactose.

    • Disaccharides: Maltose (glucose + glucose), Sucrose (glucose + fructose), Lactose (glucose + galactose).

    • Polysaccharides: Glycogen (animal energy storage), Starch (plant energy storage), Cellulose (plant cell walls/fiber).

  • Proteins:

    • Monomers: Amino Acids ($C, H, O, N$). There are $20$ different types; humans make $12$ and must ingest $8$ (essential amino acids).

    • Structure: Polypeptide chains folded into specific shapes. Functions include enzymes, hormones, muscle/hair components, and hemoglobin.

  • Lipids (Fats):

    • Components: Glycerol and fatty acids (Triglycerides have $1$ glycerol + $3$ fatty acids; Phospholipids have $1$ glycerol + $2$ fatty acids + $1$ phosphoric acid).

    • Functions: Insulation, cushioning organs, energy source, and cell membrane components.

  • Nucleic Acids:

    • Monomers: Nucleotides ($C, H, O, N, P$).

    • Examples: DNA and RNA.

The Human Digestive System

• The digestive system consists of the Alimentary Canal (digestive tract, $\sim 7-9\,m$ long) and Accessory Organs (glands providing enzymes via ducts).

• The Digestive Process:

  1. Ingestion: Taking food in via the mouth.

  2. Digestion: Breaking food down. Mechanical Digestion is physical (teeth, stomach churning). Chemical Digestion uses enzymes and juices to break particles small enough for blood absorption.

  3. Absorption: Nutrients move into the blood. $80\%$ occurs in the small intestine; $20\%$ in the stomach and large intestine.

  4. Egestion: Removal of solid waste.

• The Mouth (Oral Cavity):

  • Mechanical: Teeth (Incisors for biting, Canines for tearing, Premolars/Molars for grinding).

  • Chemical: Saliva ($98\%$ water, $1\%$ mucus, $1\%$ enzymes). Enzymes include Amylase (starch → maltose), Maltase (maltose → glucose), and Lingual Lipase (lipids).

  • Food is molded into a soft mass called a Bolus.

• The Esophagus:

  • Connects pharynx to stomach. Movement occurs via Peristalsis (involuntary muscle contractions).

  • Epiglottis: Closes the trachea (windpipe) during swallowing to prevent choking.

• The Stomach:

  • J-shaped organ performing mechanical (churning) and chemical digestion. Inner layer contains Rugae (folds) for expansion.

  • Gastric Juice: Contains Hydrochloric Acid ($HCl$) and Pepsin. Pepsin (activated from pepsinogen by $HCl$) digests proteins. Gastric Lipase digests fats.

  • Sphincters: Cardiac (top) prevents reflux; Pyloric (bottom) controls exit to small intestine.

  • Resulting semi-liquid state is called Chyme; stomach $pH$ is $\sim 2-3$.

• The Small Intestine: $\sim 6-7.5\,m$ long, $2.5\,cm$ diameter. Three parts: Duodenum, Jejunum, Ileum.

  • Villi and Microvilli: Finger-like projections that increase surface area for absorption. Villi contain capillaries (absorb most nutrients) and lacteals (absorb lipids/fats).

• The Large Intestine: $\sim 1.5\,m$ long, $7.5\,cm$ diameter. Absorbs water ($\sim 20\,L$ daily), electrolytes ($Na^+, Cl^-$), and vitamins ($B, K$) produced by resident bacteria like E. coli.

  • Includes Cecum, Colon (Ascending, Transverse, Descending, Sigmoid), Rectum, and Anus.

• Accessory Organs:

  • Liver: Largest internal organ ($200+$ functions). Produces Bile (emulsifies fats). Processes nutrients and breaks down toxins.

  • Gallbladder: Stores and concentrates bile.

  • Pancreas: Secretes pancreatic juice (amylase, lipase, trypsin, peptidase). Releases Bicarbonate Ions to neutralize acidic chyme ($pH\,\sim 2$ to $\sim 7$). Produces Insulin and Glucagon.

Digestive Enzymes and Biochemical Breakdown

• Enzymes: Biological catalysts made of proteins that speed up reactions without being consumed. Follow a Lock and Key model where the Substrate binds to the Active Site.

• Carbohydrases: Break down carbohydrates.

  • Salivary Amylase (mouth): Starch → Maltose.

  • Sucrase/Lactase/Maltase (small intestine): Disaccharides → Monosaccharides.

• Lipases: Break down lipids.

  • Lingual Lipase (mouth), Gastric Lipase (stomach), Pancreatic Lipase (small intestine).

• Proteases: Break down proteins.

  • Pepsin (stomach): Protein → Polypeptides.

  • Trypsin/Peptidase (pancreas/small intestine): Polypeptides → Amino Acids.

Blood Sugar Regulation and Diabetes

• Homeostasis: Maintenance of blood glucose levels between $4-7\,mmol/L$.

• Insulin: Secreted by Beta cells in the Pancreas; allows glucose to enter cells, decreasing blood sugar.

• Glucagon: Increases blood glucose levels when they are low.

• Diabetes: Abnormally high blood glucose.

  • Type I (Insulin Dependent): Autoimmune destruction of Beta cells; little to no insulin. Typically affects children/adolescents ($10\%$ of cases).

  • Type II (Non-Insulin Dependent): Cells fail to respond to insulin (defective receptors). Linked to diet and activity ($90\%$ of cases).

• History: Frederick Banting and Charles Best discovered insulin in $1921-1922$ at the University of Toronto. They were awarded the Nobel Prize in $1923$ (shared with Macleod and Collip).

The Respiratory System

• Functions to take in $O_2$ for cellular respiration and remove $CO_2$ waste. Features a thin membrane, large surface area, good blood supply, and ventilation system.

• Anatomy:

  • Nasal Cavity: Warms, cleans, and moistens air via mucus and cilia.

  • Pharynx/Larynx: Common path for food/air; contains vocal cords.

  • Trachea: Windpipe with cartilage rings to prevent collapse.

  • Bronchi/Bronchioles: Branching tubes leading into lungs.

  • Alveoli: Tiny air sacs for gas exchange. Surrounded by capillaries.

  • Pleura: Double membrane surrounding lungs.

  • Diaphragm/Intercostal Muscles: Involved in the mechanics of breathing.

• Mechanics of Breathing:

  • Inhalation (Inspiration): Diaphragm moves down, intercostals contract, thoracic cavity volume increases, lung pressure decreases, and air enters.

  • Exhalation (Expiration): Diaphragm moves up, intercostals relax, thoracic cavity volume decreases, lung pressure increases, and air is expelled.

• Lung Volumes:

  • Tidal Volume (TV): Normal breath, $\sim 250-500\,mL$.

  • Inspiratory Reserve Volume (IRV): Deep breath extra volume, $\sim 2500\,mL$.

  • Expiratory Reserve Volume (ERV): Extra forceful exhale, $\sim 1000\,mL$.

  • Residual Volume (RV): Air remaining after maximal expiration, $\sim 1200\,mL$.

  • Vital Capacity (VC): Total movable air ($TV + IRV + ERV$), $\sim 4500\,mL$.

  • Total Lung Capacity: $\sim 6000\,mL$.

Gas Exchange and Respiration Phases

• Respiration Phases:

  1. Breathing (Ventilation): Movement of air in and out.

  2. External Respiration: Gas exchange between alveoli and capillaries. $O_2$ moves into blood; $CO_2$ moves into alveoli.

  3. Circulation: Transport of gases via blood. Phosphorus binds to Hemoglobin ($Hb$) in RBCs ($98.5\%$). $CO_2$ travels as Bicarbonate ions ($70\%$), bound to $Hb$ ($20\%$), or dissolved in plasma ($10\%$).

  4. Internal Respiration: Gas exchange between blood and body cells. $O_2$ into cells; $CO_2$ into blood.

  5. Cellular Respiration: Equation: $O_2 + C_6H_{12}O_6 \rightarrow CO_2 + H_2O + \text{Energy (ATP)}$.

• Breathing Rate Control: Regulated by the Medulla Oblongata and Pons based on $CO_2$ levels/blood $pH$, not $O_2$. Normal rate: $12-20$ breaths per minute.

The Cardiovascular System: Blood and Typing

• Blood Components:

  • Plasma ($55\%$): Straw-colored liquid ($92\%$ water); transports nutrients, wastes, hormones.

  • Erythrocytes (RBCs) ($45\%$): Biconcave discs with no nucleus; contains hemoglobin to carry $O_2/CO_2$. Lifespan: $\sim 120$ days.

  • Leukocytes (WBCs) (<1\%): Fight infection; possess a nucleus.

  • Thrombocytes (Platelets) (<1\%): Cell fragments for blood clotting.

• Blood Typing (ABO System):

  • Determined by Antigens on RBC surface and Antibodies in plasma.

  • Type A: A antigens, B antibodies. Type B: B antigens, A antibodies.

  • Type AB: A and B antigens, no antibodies (Universal Recipient).

  • Type O: No antigens, A and B antibodies (Universal Donor).

  • Agglutination: Clumping that occurs if incompatible blood is mixed.

• Rh Factor: "D" antigen. Rh+ has it ($85\%$ of population); Rh- lacks it ($15\%$).

  • Rh- persons can develop antibodies against Rh+ blood, causing hemolytic disease in pregnancy.

Blood Vessels and the Heart

• Blood Vessels:

  • Arteries: Carry blood AWAY from the heart. Thick, elastic walls; high pressure. Pulmonary Artery is the only one carrying deoxygenated blood.

  • Veins: Carry blood TOWARD the heart. Thin walls, low pressure; contain One-Way Valves to prevent backflow. Pulmonary Vein carries oxygenated blood.

  • Capillaries: Microscopic, one-cell thick for gas/nutrient exchange.

• The Heart:

  • Chambers: Right Atrium, Right Ventricle, Left Atrium, Left Ventricle.

  • Septum: Muscular wall separating right/oxygen-poor side from left/oxygen-rich side.

  • Valves: Tricuspid and Mitral (AV valves); Pulmonary and Aortic (Semilunar valves). Create the "LUB-DUB" sound.

  • Cardiac Cycle:

    • Systole: Contraction (emptying).

    • Diastole: Relaxation (filling).

  • Path of Blood Flow: Vena Cava → Right Atrium → Tricuspid Valve → Right Ventricle → Pulmonary Valve → Pulmonary Artery → Lungs → Pulmonary Vein → Left Atrium → Mitral Valve → Left Ventricle → Aortic Valve → Aorta → Body.

Electrical Control and Blood Pressure

• Heart Rhythm: Heart muscle is Myogenic (contracts on its own) but regulated by nerves.

  • SA Node (Pacemaker): Initiates signal in right atrium.

  • AV Node: Delays signal to allow ventricles to fill.

  • Bundle of His / Purkinje Fibres: Distribute the electrical signal to cause ventricular contraction.

• Blood Pressure: Force of blood against vessel walls.

  • Normal reading: $120/80\,mmHg$ (Systolic/Diastolic).

  • Hypertension: High blood pressure (>140/90\,mmHg). Causes include arteriosclerosis and obesity.

Summary of Internal Disorders

• Digestive Disorders:

  • Stomach Ulcers: Sores in stomach lining; often caused by bacteria.

  • Constipation / Diarrhea: Issues with water reabsorption in the colon.

  • Celiac Disease: Gluten triggers immune response damaging small intestine villi.

  • Stones: Gallbladder stones formed from bile salts.

• Respiratory Disorders:

  • Bronchitis: Inflammation of bronchial tubes.

  • Pneumonia: Infection filling alveoli with fluid.

  • Emphysema: Destruction of alveoli wall, decreasing surface area for gas exchange.

  • Cystic Fibrosis: Genetic disease causing thick mucus buildup.

• Circulatory Disorders:

  • Anemia: Reduction in RBCs or hemoglobin.

  • Leukemia: Cancer of the white blood cells.

  • Arteriosclerosis: Hardening of arteries due to plaque buildup.

  • Angina / Heart Attack: Reduced or blocked blood flow in coronary arteries.