Immune Response and Specific Defenses

Specific Defenses

• Immune Response: Triggered when pathogens bypass nonspecific defenses.
• Antigens: Substances that trigger the immune response (e.g., viruses, bacteria).
• Lymphocytes: Immune system cells that recognize antigens.
• B Cells: Provide humoral immunity against antigens and pathogens in body fluids.
• T Cells: Provide cell-mediated immunity against abnormal cells and pathogens inside cells.
• Humoral Immunity: B cells recognize pathogens, rapidly divide into plasma cells and memory B cells.
• Plasma Cells: Release antibodies to recognize, bind, and target pathogens for destruction. They stop producing antibodies once the infection is gone.
• Memory B Cells: "Remember" pathogens, enabling rapid antibody production upon subsequent exposure. A key aspect of long-term immunity.
• Vaccines: Introduce antigens without pathogens, creating antibody-producing plasma cells. Booster shots are useful for maintaining immunity by providing refresher exposure to the targeted antigen, stimulating further antibody production.

Antibody Structure

• Shaped like a Y, with two binding sites for antigens.
• Diverse shapes allow for recognition of many antigens.
• Healthy adults can produce millions of different antibody types.

Excretory System

• Goal of Urinary System: Filter wastes from the blood, regulate fluid levels, and eliminate excess salts.
• Waste Production: Cells during respiration produce wastes.
• Hypothalamus Regulation: Monitors blood water levels. When water is high, reduces hormone release. This decreases water reabsorption in kidneys leading to increased urine output.
• Kidneys: Main organs; filter blood containing cellular waste. Each consists of one million filtering units called nephrons.

Nephron

• Structure: Located mostly in the renal cortex.
• Filtration: Blood enters through renal artery; water, sugars, salts, and waste enter Bowman's capsule.
• Reabsorption: Most water, sugar, and salts are reabsorbed.
• Excretion: Other substances (drugs) are actively excreted.
• Filtration Rate: ≈ 2000 Liters of blood filtered daily. Approximately 1.5 Liters of urine excreted daily.
• Urine Formation: Four-step process (Filtration, Reabsorption, Secretion, Excretion)
• Urinalysis: Common non-invasive medical test.

Immune System

• Function: Guard against disease by producing cells that inactivate foreign substances/cells.
• Layers of Defense: Multiple layers of defense to fight disease-causing agents (pathogens).
• Immune Response: Recognition, attack, destruction, and immunological "memory" of pathogens.
• Immune System Organs: Skeletal system (bone marrow produces white blood cells), stomach and saliva help.

Nonspecific Defenses

• Skin: Crucial first line of defense; unbroken skin prevents pathogen entry. Breaks in skin lead to infection.
• Secretions (Mucus, Saliva, Tears, Oil, Sweat): Contain lysozyme (enzyme that breaks down bacterial cell walls); acidic environment inhibits bacterial growth.
• Inflammatory Response: Reaction to tissue damage; characterized by swelling, redness, pain, heat, white blood cell recruitment and targeted destruction, and fever response
• Interferons: Proteins that resist viral infections by interfering with viral growth, giving the immune system time to respond.

Transportation System (Circulatory System)

• Components: Heart, arteries, veins, capillaries.
• Closed System: Blood remains contained in vessels.
• Arteries: Carry oxygenated blood away from the heart; deoxygenated blood to lungs.
• Capillaries: Sites of gas and waste exchange.
• Veins: Carry deoxygenated blood back to the heart; oxygenated blood from lungs to heart.

Heart

• Structure and Function: Muscular pump; composed of mostly cardiac muscle; divided by the septum to prevent mixing of oxygenated and deoxygenated blood.
• Atrium: Receives blood.
• Ventricles: Pumps blood out.
• Circulatory Systems: Pulmonary (right side - blood to lungs) and Systemic (left side - blood to body tissues) circulation.

Digestive System

• Mouth: Contains digestive enzymes (amylase, lysozyme) that break down carbohydrates and fight infection.
• Teeth: Tear, crush, and chew food.
• Esophagus: Connects mouth to stomach; peristalsis moves food.
• Stomach: Mechanical/chemical digestion; releases HCl and pepsin for protein breakdown; mucus to protect lining.
• Small Intestine: Most digestion and nutrient absorption, with enzymes from pancreas and liver.
• Pancreas: Produces hormones and enzymes for digestion.
• Liver: Produces bile for fat digestion; stored in gallbladder.
• Large Intestine: Removes water from undigested materials; harbors beneficial bacteria.

Cell-Mediated Immunity

• Mechanism: T cells (killer, helper, memory, suppressor) are activated when abnormal cells or pathogens are detected.
• Killer T cells: Destroy infected or cancerous cells.
• Helper T cells: Stimulate adaptive immune response
• Memory T cells: Provide long-term immunity
• Suppressor T cells: Regulate the immune response

Beneficial Bacteria

• Presence: Found on skin, small intestine, etc.
• Competition/Defense: Outcompete pathogens or create substances that kill them.

Acquired Immunity

• Definition: Immunity gained through exposure or introduction from outside the body.
• Types: Active (vaccination) and Passive (antibodies from another source).
• Active Immunity: Vaccination stimulates an immune response resulting in long lasting antibody production,
• Passive Immunity: Temporary immunity provided by introduction of antibodies from an external source (e.g., mother to infant).

Blood

• Blood Pressure: Force of blood against artery walls (systolic and diastolic values).
• Normal Blood Pressure: 120/80 mm Hg
• Composition: Plasma (55%), red blood cells, white blood cells, platelets.

Lymphatic System

• Function: Collects fluid lost by blood, returns it to the circulatory system; part of waste removal and immunity
• Components: Vessels, nodes, organs.