Exam 1 Master Study Guide

Where Body Water Lives

The ECF splits into three parts:

• Intravascular fluid, the fluid inside blood vessels (plasma).
• Interstitial fluid, the fluid in the spaces around cells.
• Transcellular fluid, smaller pools like spinal fluid, joint fluid, and belly fluid.

Hydrostatic vs. Oncotic Pressure

Causes of Peripheral Edema (fluid in the tissues)

Edema means fluid leaks out of vessels into tissue. It happens when:

• Hydrostatic pressure goes UP → fluid gets pushed out too hard (heart failure, high blood pressure).
• Oncotic pressure goes DOWN → nothing pulls the fluid back in (liver failure, poor diet, kidney disease that loses albumin).
• Lymph vessels are blocked → fluid cannot drain away (lymphedema, after breast surgery).
• Capillaries turn leaky → the vessel walls let fluid through (inflammation, sepsis, burns).

❓ Free-Response Practice

1. What percent of body fluid is inside cells vs outside cells? Which electrolyte leads in each?
   Show answer

   ICF is about 2/3 and is high in K⁺. ECF is about 1/3 and is high in Na⁺.
2. Compare hydrostatic and oncotic pressure.
   Show answer

   Hydrostatic is a pushing force. It pushes fluid OUT of vessels. Oncotic is a pulling force from albumin. It pulls fluid INTO vessels.
3. List 4 causes of edema in the legs and arms.
   Show answer

   Higher hydrostatic pressure (heart failure). Lower oncotic pressure from low albumin (liver failure, poor diet, kidney disease). Blocked lymph vessels. Leaky capillaries (inflammation or sepsis).
4. What is the difference between intravascular and interstitial fluid?
   Show answer

   Intravascular fluid sits inside blood vessels (plasma). Interstitial fluid sits around tissue cells, outside the vessels.
5. Why does a patient with cirrhosis get edema and ascites?
   Show answer

   The scarred liver makes less albumin. That drops oncotic pressure. Fluid then stays in the tissues and belly instead of being pulled back into the vessels.

✅ Multiple Choice Practice

1. The main electrolyte inside cells is:
   A) Sodium · B) Potassium · C) Calcium · D) Chloride
   Show answer

   B. Potassium dominates ICF.
2. A patient with bad burns swells all over. The most likely cause is:
   A) Blocked lymph vessels · B) Leaky capillaries · C) Low hydrostatic pressure · D) High oncotic pressure
   Show answer

   B. A burn makes capillaries leaky. Fluid escapes into the tissue.
3. Which protein does most of the work of oncotic pressure?
   A) Hemoglobin · B) Globulin · C) Albumin · D) Fibrinogen
   Show answer

   C. Albumin.

The RAAS System (Renin-Angiotensin-Aldosterone System)

What turns it on: the kidneys sense low blood pressure, low blood volume, or low sodium.

The chain of steps:

1. The kidneys release renin when BP or volume is low.
2. Renin turns angiotensinogen from the liver into angiotensin I.
3. ACE (angiotensin-converting enzyme) in the lungs turns angiotensin I into angiotensin II.
4. Angiotensin II then does 2 main jobs:
   • It tightens blood vessels → BP goes up.
   • It tells the adrenal cortex to release aldosterone.

Aldosterone vs. ADH: What Each Does at the Kidney

ANP & BNP, The "Off-Switch"

ANP (atrial natriuretic peptide) comes from the atria of the heart. BNP (brain or B-type natriuretic peptide) comes from the ventricles. Both come out when the heart gets stretched by high volume or high pressure.

What they do: the opposite of RAAS.

• Dump sodium in the urine (natriuresis) and water with it.
• Widen blood vessels.
• Lower BP and volume.
• Block renin and aldosterone.

Why it matters: a high BNP is a sign of heart failure.

Angiotensin II: Main Actions

• Tightens vessels → BP goes up.
• Tells the body to release aldosterone.
• Tells the body to release ADH.
• Makes you thirsty.

This is why ACE inhibitors lower BP. These are the "–pril" drugs like lisinopril. They block this whole chain.

❓ Free-Response Practice

1. What turns the RAAS system on?
   Show answer

   The kidneys sense low BP, low blood volume, or low sodium.
2. List the 4 main actions of angiotensin II.
   Show answer

   It tightens vessels. It triggers aldosterone. It triggers ADH. It makes you thirsty.
3. Compare what aldosterone and ADH do at the kidney.
   Show answer

   Aldosterone takes back sodium, and water follows it. It also dumps potassium. ADH takes back water only, with no sodium.
4. What do ANP and BNP do?
   Show answer

   They dump sodium and water. They widen vessels. They lower BP and volume. They block RAAS. They are the mirror image of RAAS.
5. Why is BNP high in heart failure?
   Show answer

   Backed-up fluid overstretches the failing ventricles. That stretch makes them release BNP. More BNP means more stretch, and more stretch means worse failure.

✅ Multiple Choice Practice

1. Aldosterone makes the kidneys:
   A) Dump sodium · B) Take back sodium and water, and dump potassium · C) Take back water only · D) Widen vessels
   Show answer

   B. It takes back Na, and water with it. It dumps K.
2. A high BNP points most directly to:
   A) Liver failure · B) Dehydration · C) Heart failure · D) Diabetes
   Show answer

   C. Heart failure, from stretched ventricles.
3. Which hormone takes back water WITHOUT moving sodium?
   A) Aldosterone · B) ADH · C) Angiotensin II · D) Renin
   Show answer

   B. ADH moves water only.

Hint: Water follows sodium. Potassium is "the heart one." Phosphate moves opposite to calcium. Magnesium blocks calcium at the nerve ending.

⚒ Sodium (Na⁺): 135–145 mEq/L

What it does: runs fluid balance. The kidneys control it.

❤️ Potassium (K⁺): 3.5–5.0 mEq/L, "the heart one"

What it does: sets the resting voltage across the cell membrane, so it runs how easily nerve and heart cells fire and how the beat is carried. It also helps with acid-base balance. The squeeze itself belongs to calcium.

🧹 Calcium (Ca): 8.5–10.5 mg/dL

What it does: helps muscles squeeze, lets nerves fire, helps blood clot, and keeps bone strong.

🧸 Phosphate (P): 2.5–4.5 mg/dL, the opposite of calcium

What it does: steadies cell membranes, builds bone and teeth, powers cells, and builds DNA and RNA.

🧋 Magnesium (Mg): 1.5–2.5 mEq/L, "the muscle relaxer"

What it does: relaxes muscle and helps control potassium. It blocks calcium at the nerve ending, so it damps down how much signal the nerve sends to the muscle.

❓ Free-Response Practice

1. Give the normal lab range for Na, K, Ca, P, and Mg.
   Show answer

   Na: 135–145 mEq/L. K: 3.5–5.0 mEq/L. Ca: 8.5–10.5 mg/dL. P: 2.5–4.5 mg/dL. Mg: 1.5–2.5 mEq/L.
2. Which EKG change goes with high potassium? Which goes with low potassium?
   Show answer

   High potassium gives peaked T waves. Low potassium gives flat T waves with tall U waves.
3. Describe Trousseau's and Chvostek's signs. Which imbalance do they point to?
   Show answer

   Trousseau's sign is a hand spasm after you inflate a BP cuff. Chvostek's sign is a face twitch when you tap the cheek. Both point to low calcium, and low magnesium can do it too.
4. Why does kidney failure raise phosphate AND drop calcium?
   Show answer

   Failing kidneys cannot clear phosphate, so P builds up. Calcium and phosphate move in opposite directions, so Ca drops as P rises. Failing kidneys also turn on less vitamin D. That means the gut absorbs even less calcium.
5. What are the signs of too much magnesium (hypermagnesemia)?
   Show answer

   Weak deep tendon reflexes, sleepiness, low blood pressure, slow breathing, cardiac arrest. This is why reflexes are checked during IV Mg for preeclampsia.

✅ Multiple Choice Practice (SATA practice too)

1. Which lab finding fits high potassium best?
   A) Flat T waves · B) Peaked T waves · C) Long QT · D) U waves
   Show answer

   B. Peaked T waves.
2. Select ALL that apply. Causes of low potassium:
   A) Loop diuretics · B) Vomiting · C) Kidney failure · D) Alkalosis · E) Acidosis
   Show answer

   A, B, D. Loop diuretics waste K. Vomiting loses K. Alkalosis pushes K into cells, so blood K reads low. Kidney failure and acidosis raise K instead.
3. A patient with low calcium is likely to show:
   A) Bone pain · B) Constipation · C) Trousseau's sign · D) Sleepiness
   Show answer

   C. Trousseau's sign, a hand spasm when the BP cuff inflates.

Acid-Base Basics

• Normal body chemistry makes CO₂ and H⁺. Both of these are acids.
• The body's goal is to hold pH between 7.35 and 7.45. That is a very narrow window.
• pH and H⁺ move in opposite directions. When H⁺ is high, pH is low, and the blood is acidic.
• Acids: CO₂ and H⁺. Base: HCO₃⁻.

The 3 Buffer Systems

Why K⁺ Shifts When pH Shifts

In acidosis, H⁺ pours into the cells to be buffered. K⁺ gets pushed out into the blood. So acidosis goes with high potassium. Alkalosis does the reverse, so alkalosis goes with low potassium.

❓ Free-Response Practice

1. Give all 4 normal ABG values.
   Show answer

   pH 7.35–7.45 · PaCO₂ 35–45 mmHg · HCO₃⁻ 22–26 mEq/L · PaO₂ 80–100 mmHg.
2. Which one is the acid and which one is the base: CO₂ or HCO₃⁻?
   Show answer

   CO₂ is the acid. HCO₃⁻ is the base.
3. Put the 3 buffer systems in order of speed.
   Show answer

   Serum works in seconds. The lungs work in minutes. The kidneys take days, and they are the strongest.
4. What is Kussmaul breathing?
   Show answer

   Deep, fast breathing. It blows off CO₂ to make up for metabolic acidosis. You see it most often in DKA.
5. What does acidosis do to blood K⁺?
   Show answer

   It raises it. H⁺ moves into the cells, and K⁺ gets pushed out into the blood.

✅ Multiple Choice Practice

1. Which buffer acts fastest?
   A) Serum · B) Respiratory · C) Renal · D) Lymphatic
   Show answer

   A. The serum (chemical) buffer works in seconds.
2. The strongest buffer system is:
   A) Serum · B) Respiratory · C) Renal · D) Cardiac
   Show answer

   C. The kidneys are the slowest but the strongest.
3. A pH of 7.30 with a PaCO₂ of 50 mmHg means:
   A) Metabolic acidosis · B) Respiratory acidosis · C) Metabolic alkalosis · D) Respiratory alkalosis
   Show answer

   B. An acid pH with a high CO₂ is respiratory acidosis.

Acidosis (pH < 7.35)

Alkalosis (pH > 7.45)

What Acidosis Does to the Body

• Brain: confusion, sleepiness, coma.
• Heart: odd rhythms, a weaker squeeze, wide vessels, low blood pressure.
• Lungs: Kussmaul breathing, which is the body compensating.
• Bone: long-term acidosis pulls Ca out of bone.
• Electrolytes: potassium goes up.
• Enzymes: they lose their shape at an extreme pH.

❓ Free-Response Practice

1. List 2 causes of metabolic acidosis and 2 causes of respiratory acidosis.
   Show answer

   Metabolic: DKA and bad diarrhea. Respiratory: COPD and opioid overdose.
2. List 2 causes of metabolic alkalosis and 2 causes of respiratory alkalosis.
   Show answer

   Metabolic: heavy vomiting and NG suction. Respiratory: a panic attack and fast breathing from fever.
3. Which way does K⁺ move in each acid-base problem?
   Show answer

   Acidosis pushes K⁺ up. Alkalosis pulls K⁺ down.
4. List 3 things acidosis does to the body.
   Show answer

   Confusion or coma. Odd heart rhythms. High potassium. Kussmaul breathing to compensate. Over time, Ca loss from bone.
5. What does a wide anion gap tell you?
   Show answer

   It means metabolic acidosis with extra acid built up that the lab did not measure. Think DKA, lactic acidosis, salicylates, or kidney failure.

✅ Multiple Choice Practice

1. Heavy vomiting is most likely to cause:
   A) Metabolic acidosis · B) Metabolic alkalosis · C) Respiratory acidosis · D) Respiratory alkalosis
   Show answer

   B. You lose HCl from the stomach, so you get metabolic alkalosis.
2. A patient with an opioid overdose is at highest risk for:
   A) Metabolic acidosis · B) Metabolic alkalosis · C) Respiratory acidosis · D) Respiratory alkalosis
   Show answer

   C. Slow breathing traps CO₂ in the blood.
3. Bad diarrhea is most likely to cause:
   A) Metabolic acidosis · B) Metabolic alkalosis · C) Respiratory acidosis · D) Respiratory alkalosis
   Show answer

   A. You lose HCO₃⁻ from the gut, so you get metabolic acidosis.

Why we draw ABGs

An ABG shows three things. It shows oxygen (PaO₂), air movement (PaCO₂), and acid-base balance. That makes it key in the ICU, on a ventilator, and in metabolic emergencies.

The 3-Step ABG Method

1. Look at the pH: under 7.35 is acidosis. Over 7.45 is alkalosis. A pH of 7.35–7.45 is normal, though it may be compensated.
2. Decide if it is respiratory or metabolic, using ROME:
   • Check the PaCO₂, which is the lung value. Normal is 35–45 mmHg.
   • Check the HCO₃⁻, which is the kidney value. Normal is 22–26 mEq/L.
   • Respiratory Opposite: if the CO₂ moved the opposite numeric way from the pH, meaning one went up while the other went down, the lungs are the cause.
   • Metabolic Equal: if the HCO₃⁻ moved the same numeric way as the pH, meaning both went down or both went up, the kidneys are the cause.
3. Look for compensation: if the OTHER value is also off, and it is pulling the pH back toward normal rather than driving it further out, the body is compensating.

ROME Memory Trick

Compensation Levels

• Uncompensated. Only the value causing the problem is off.
• Partly compensated. Both values are off, and the pH is still out of range.
• Fully compensated. Both values are off, but the pH is back in range.

Worked Examples

❓ Free-Response Practice

1. What does ROME stand for?
   Show answer

   Respiratory Opposite, Metabolic Equal.
2. Read this one: pH 7.50, CO₂ 28 mmHg, HCO₃⁻ 22 mEq/L.
   Show answer

   The pH is alkaline. The CO₂ of 28 is low while the pH went up, so they moved in opposite directions. Respiratory Opposite points to the lungs. The HCO₃⁻ is normal. This is uncompensated respiratory alkalosis. Think fast breathing or a panic attack.
3. Read this one: pH 7.32, CO₂ 35 mmHg, HCO₃⁻ 17 mEq/L.
   Show answer

   The pH is acidic. The CO₂ is normal. The HCO₃⁻ of 17 is low and the pH is low too, so Metabolic Equal points to the kidneys. This is uncompensated metabolic acidosis.
4. Why does a high CO₂ act like an acid?
   Show answer

   CO₂ + H₂O → H₂CO₃ → H⁺ + HCO₃⁻. More CO₂ drives that reaction forward, so the blood ends up with more H⁺.
5. What does a normal pH with an abnormal CO₂ AND an abnormal HCO₃⁻ mean?
   Show answer

   It is fully compensated. The body pulled the pH back in range, but both systems are still off.

✅ Multiple Choice Practice

1. pH 7.20, CO₂ 58 mmHg, HCO₃⁻ 22 mEq/L. This is:
   A) Uncompensated respiratory acidosis · B) Compensated metabolic acidosis · C) Metabolic alkalosis · D) Mixed disorder
   Show answer

   A. The pH is acidic and the CO₂ is high, so they moved in opposite directions. Respiratory Opposite points to the lungs. The HCO₃⁻ is normal, so nothing is compensating.
2. pH 7.38, CO₂ 56 mmHg, HCO₃⁻ 32 mEq/L. This is:
   A) Uncompensated respiratory acidosis · B) Fully compensated respiratory acidosis · C) Metabolic alkalosis · D) Normal
   Show answer

   B. The pH is back in range but sits on the acid side of 7.40. Both the CO₂ and the HCO₃⁻ are off. That makes it fully compensated respiratory acidosis. This is the classic long-term COPD picture.
3. A patient having a panic attack most likely has:
   A) Respiratory acidosis · B) Respiratory alkalosis · C) Metabolic acidosis · D) Metabolic alkalosis
   Show answer

   B. Fast breathing drops the CO₂, and that gives respiratory alkalosis.

Types of Pathogens

Fungal Infections: Surface vs Deep

Many fungi are normal flora, meaning they live on us all the time. They cause trouble when they overgrow or push into tissue. This often happens after antibiotics wipe out the bacteria that kept them in check.

Testing for Microbes

• Gram stain (for bacteria):
  • Gram-positive bugs have a thick cell wall. They stain PURPLE.
  • Gram-negative bugs have a thin cell wall. They stain PINK or RED. They are harder to treat, because an outer membrane blocks drugs.
• Culture and sensitivity. The culture names the bug. The sensitivity shows which antibiotic will work on it.

What Drives Antibiotic Resistance

• Using antibiotics when they are not needed, like for a cold or the flu, which are viral.
• Stopping the antibiotic early. The bacteria that live through it multiply and pass on resistance.
• Heavy use on farms and in livestock.
• Patients not taking the drug as directed.
• Reaching for broad-spectrum antibiotics too often.
• Picking up resistant bugs in the hospital, such as MRSA, VRE, and C. diff.

❓ Free-Response Practice

1. List the 4 types of pathogens and one example of each.
   Show answer

   Bacteria, like E. coli. Viruses, like HIV. Fungi, like Candida. Parasites, like tapeworm.
2. What color does a gram-positive bacterium stain, and why?
   Show answer

   Purple. Its thick cell wall holds on to the crystal violet dye.
3. Why are gram-negative bacteria often harder to treat?
   Show answer

   Their outer membrane acts as a shield. It stops many antibiotics from reaching the target inside.
4. List 3 things that drive antibiotic resistance.
   Show answer

   Using them when they are not needed, such as for a virus. Stopping the course early. Farm use. Reaching for broad-spectrum drugs too often. Patients not taking the drug as directed.
5. What is the difference between a culture and a sensitivity?
   Show answer

   The culture names the bacteria. The sensitivity shows which antibiotic kills it.

✅ Multiple Choice Practice

1. A patient has a fungal infection in the mouth. This is likely:
   A) Tinea · B) Candida (thrush) · C) Helminth · D) Virus
   Show answer

   B. Candida in the mouth is called thrush.
2. Viruses differ from bacteria because viruses:
   A) Have a thick cell wall · B) Show up on a gram stain · C) Cannot copy themselves without a host cell · D) Are killed by antibiotics
   Show answer

   C. Viruses need a host cell to make more of themselves.
3. Which of these feed antibiotic resistance? (SATA)
   A) Stopping antibiotics early · B) Using antibiotics for viral infections · C) Taking the drug as directed · D) Farm use of antibiotics · E) Hand washing
   Show answer

   A, B, D. Taking the drug as directed and washing hands both help PREVENT resistance.

Routes of Transmission

• Direct contact means person to person, through touch or sex. Examples: HIV, herpes, scabies.
• Indirect contact means through an object, called a fomite. Examples: doorknobs, IV poles.
• Droplet means large drops from the airway that fall within about 3 to 6 feet. Examples: influenza, pertussis, meningococcal disease.
• Airborne means tiny particles that float a long way. Examples: TB, measles, varicella. COVID spreads this way as well as by droplets, so do not file it under droplets alone.
• Vector-borne means spread by an insect or animal. Examples: malaria from a mosquito, Lyme from a tick.
• Vehicle or foodborne means through food or water that carries the bug.
• Vertical means from mother to baby. It happens through the placenta, breast milk, or the birth canal.

Stages of Infection

Tuberculosis (TB)

TB is a bacterial infection caused by Mycobacterium tuberculosis. It usually sets up in the lungs. It spreads through the air, so it is airborne.

❓ Free-Response Practice

1. List the 6 stages of infection in order.
   Show answer

   Exposure → Incubation → Prodrome → Acute → Convalescent → Resolution.
2. In which stage does a person usually spread the infection most?
   Show answer

   Prodrome. The symptoms are still vague, but the person is shedding a lot of the pathogen. Many people pass it on here without knowing.
3. List 4 routes of spread with an example of each.
   Show answer

   Direct contact, like HIV. Droplet, like the flu. Airborne, like TB and measles. Vector-borne, like malaria from a mosquito. Food or water, like Salmonella. Vertical, like HIV passing from mother to baby.
4. Compare latent TB with active TB.
   Show answer

   Latent TB is walled off by the immune system. There are no symptoms, the person cannot spread it, and the skin test is positive. In active TB the bacteria have escaped. There are symptoms, such as a cough over 3 weeks, coughing up blood, fever, and weight loss. The person can spread it.
5. How does TB spread?
   Show answer

   Through the air, in tiny particles from the lungs.

✅ Multiple Choice Practice

1. Which pathogen spreads through the air?
   A) HIV · B) Tuberculosis · C) Salmonella · D) Lyme
   Show answer

   B. TB spreads through the air.
2. A patient with latent TB:
   A) Has active symptoms · B) Spreads it easily · C) Has a positive skin test but no symptoms · D) Should not be treated
   Show answer

   C. The PPD or TST is positive, there are no symptoms, and the person cannot spread it. We still treat it, to keep it from waking up.
3. Vague tiredness and a low fever, before any specific symptoms, happen in which stage?
   A) Incubation · B) Prodrome · C) Acute · D) Resolution
   Show answer

   B. Prodrome is the stage of early, vague symptoms.

How It Looks Different in Older Adults

Older adults often look nothing like the textbook picture:

• Confusion, delirium, or any change in thinking may be the ONLY sign of a UTI.
• They may have no burning and no need to go often.
• Watch for falls, doing less than usual, and new loss of bladder control.
• Always check for a UTI in an older patient with new confusion.

Risk Factors

• Diabetes. Sugar in the urine feeds bacteria, and the immune system works less well.
• HIV or any weak immune system.
• Problems with the shape of the tract, such as kidney stones or urine flowing backward (vesicoureteral reflux).
• Female anatomy. The urethra is shorter and sits closer to the anus.
• A catheter left in place, which can cause a CAUTI.
• Pregnancy.
• Sex.

❓ Free-Response Practice

1. List 3 symptoms of acute cystitis.
   Show answer

   Burning with urination, going often, sudden urges, and cloudy or bloody urine. There is usually NO fever.
2. Which UTI usually brings fever and flank pain?
   Show answer

   Pyelonephritis, which is a kidney infection.
3. How does an older patient with a UTI usually look?
   Show answer

   Confusion or any change in thinking may be the only sign. The classic burning and frequency may be missing.
4. List 3 risk factors for a UTI.
   Show answer

   Diabetes. A weak immune system, such as from HIV. Problems with the shape of the tract. Female anatomy. A catheter. Pregnancy. Sex.
5. What is urosepsis?
   Show answer

   A bloodstream infection that started in the urinary tract. It is what can happen when pyelonephritis goes untreated.

✅ Multiple Choice Practice

1. The clearest thing that separates cystitis from pyelonephritis is:
   A) Burning with urination · B) Going often · C) Fever and flank pain · D) How clear the urine is
   Show answer

   C. Pyelonephritis adds whole-body symptoms: fever, flank pain, feeling ill, nausea and vomiting.
2. Which of these are unusual UTI signs in an older adult? (SATA)
   A) New confusion · B) Falls · C) Classic burning with urination · D) New loss of bladder control · E) Bad flank pain
   Show answer

   A, B, D. Confusion, falls, and new loss of bladder control are the classic unusual signs.
3. Untreated pyelonephritis can lead to:
   A) Otitis media · B) Urosepsis · C) Hepatitis · D) Hypothyroidism
   Show answer

   B. Urosepsis. Bacteria move from the kidney into the blood.

Innate vs Adaptive Immunity (the 3 Lines of Defense)

Lymphocytes (Adaptive)

• B cells make antibodies. Antibodies are also called immunoglobulins, and the five of them spell "GAMED."
• T cells:
  • T helper cells (CD4) direct the B cells and the other T cells. Think of them as the conductor.
  • Cytotoxic T cells (CD8) kill infected cells and foreign cells themselves.

White Blood Cells (Leukocytes)

The 5 Immunoglobulins (Antibodies): GAMED

❓ Free-Response Practice

1. Compare innate and adaptive immunity.
   Show answer

   Innate is fast, works on anything, and has no memory. It includes barriers, macrophages, and neutrophils. Adaptive is slower, aims at one target, and has memory. It uses B cells and T cells.
2. Describe IgG, IgA, IgM, IgE, and IgD in one short phrase each.
   Show answer

   IgG: long-term, crosses the placenta. IgA: in mucus and other secretions. IgM: first to show up. IgE: allergies and parasites. IgD: on B cells that have not met an antigen.
3. What do CD4 T helper cells do?
   Show answer

   They direct the immune response and keep B cells and T cells working together.
4. Which WBC gets to a bacterial infection first?
   Show answer

   Neutrophil.
5. Which WBC and which Ig take part in allergies?
   Show answer

   Eosinophils and basophils are the WBCs. IgE is the antibody, and it sits on mast cells.

✅ Multiple Choice Practice

1. Which antibody crosses the placenta to protect a newborn?
   A) IgA · B) IgM · C) IgE · D) IgG
   Show answer

   D. IgG. Think "Gestational."
2. The first antibody the body makes in a new infection is:
   A) IgG · B) IgA · C) IgM · D) IgE
   Show answer

   C. IgM. Think "Monitor," the first one there.
3. Which of these belong to innate immunity? (SATA)
   A) Skin · B) IgG antibodies · C) Neutrophils · D) T helper cells · E) Stomach acid
   Show answer

   A, C, E. IgG and T helper cells belong to adaptive immunity.

The 4 Types of Hypersensitivity Reactions

Hypersensitivity means the immune system over-reacts to an antigen. The body's own response does more harm to tissue than the antigen ever would.

Anaphylaxis, a Type I Emergency

IgE triggers a huge release of histamine. That leads to:

• Skin: hives, flushing, and deep swelling called angioedema.
• Lungs: wheezing, a harsh noise on breathing in (stridor), a tight throat, and a blocked airway.
• Heart and vessels: low blood pressure, which is distributive shock, and a fast heart rate.
• Gut: nausea, vomiting, and diarrhea.

Treatment: IM epinephrine comes first. Then oxygen, IV fluids, antihistamines, steroids, and airway support.

Transplant Rejection

Graft-versus-host disease (GVHD) works the OTHER way. Here the donor's T cells attack the person who got the graft. It shows up mostly after bone marrow or stem cell transplants.

Types of Immunity, and How You Get Each

❓ Free-Response Practice

1. List the 4 types of hypersensitivity with one example each.
   Show answer

   Type I is Allergic, like anaphylaxis. Type II is antiBody, like an ABO transfusion reaction. Type III is Immune complex, like SLE. Type IV is Delayed, like a PPD, poison ivy, or transplant rejection.
2. What are the main signs of anaphylaxis?
   Show answer

   Hives and angioedema. Wheezing, stridor, and a tight airway. Low blood pressure with a fast heart rate. Nausea, vomiting, and diarrhea. The first drug is IM epinephrine.
3. What causes hyperacute transplant rejection?
   Show answer

   Antibodies the patient already had, which is a Type II reaction. It is often an ABO mismatch. It hits within minutes to hours of the transplant.
4. Compare the 4 ways to get immunity.
   Show answer

   Natural active means you caught the disease. Artificial active means you got a vaccine. Natural passive means you got mom's antibodies, through the placenta or breast milk. Artificial passive means you were given an antibody product, like IVIG or a monoclonal antibody.
5. Why does passive immunity wear off so fast?
   Show answer

   The body is not making those antibodies itself. The borrowed ones break down over weeks to months, and no memory cells get built.

✅ Multiple Choice Practice

1. A bee sting causes throat swelling and low blood pressure. Which type of reaction is this?
   A) Type I · B) Type II · C) Type III · D) Type IV
   Show answer

   A. Type I. IgE drives it, it hits right away, and this is anaphylaxis.
2. A patient gets mismatched blood, then has fever, back pain, and bloody urine. This is:
   A) Type I · B) Type II · C) Type III · D) Type IV
   Show answer

   B. Type II. Antibodies break down the donor red cells, which is a hemolytic transfusion reaction.
3. Getting a tetanus vaccine gives you which type of immunity?
   A) Natural active · B) Artificial active · C) Natural passive · D) Artificial passive
   Show answer

   B. Artificial active. Your own body makes the antibodies after the shot.

HIV & AIDS

HIV (Human Immunodeficiency Virus) is a retrovirus. It attacks CD4 T helper cells, the cells that conduct the immune response.

• As the CD4 count falls, the immune system loses its conductor and stops working together.
• AIDS is the late stage. It means a CD4 count under 200, or an infection that only takes hold in AIDS.

Infections That Take Hold in AIDS

Immunodeficiency: What Causes It

• Cancer, and cancer treatment such as chemo and radiation.
• HIV infection.
• Diabetes. Neutrophils work poorly, and high sugar feeds organisms.
• Long-term stress. Steady cortisol holds the immune system down.
• Poor nutrition.
• Having the spleen removed, since it is a key immune organ.
• Drugs that hold the immune system down, used after transplants and in autoimmune disease.
• Being very young or very old.

Autoimmune Disease vs Immunodeficiency

Leukemia (Cancer of the WBCs)

Leukemia is cancer of young blood cells. The cells multiply out of control, and they do not do their job.

• Lymphoblastic leukemias hit the cells that would become lymphocytes, meaning B and T cells.
• Myelocytic leukemias hit the cells that would become basophils, eosinophils, and neutrophils.
• Acute means it starts fast, the cells stay immature, and it moves hard.
• Chronic means it starts slowly, the cells are more mature, and it runs longer.

All leukemias share these signs: tiredness, anemia, infections, bleeding and bruising, weight loss, and a big spleen (splenomegaly).

Lymphoma: Hodgkin vs Non-Hodgkin

❓ Free-Response Practice

1. Which cell does HIV attack, and why does that hurt the immune system so much?
   Show answer

   It attacks CD4 T helper cells. Those cells run the whole adaptive immune response. Without them, B cells and the other T cells cannot work right.
2. Define AIDS.
   Show answer

   Late HIV with a CD4 count under 200 cells/mm³, OR an infection that only takes hold in AIDS.
3. List 4 causes of a weak immune system.
   Show answer

   Cancer or chemo. HIV. Diabetes. Poor nutrition. Long-term stress. Spleen removal. Drugs that hold the immune system down.
4. Which cell tells Hodgkin lymphoma apart from non-Hodgkin lymphoma?
   Show answer

   The Reed-Sternberg cell, which shows up in Hodgkin.
5. Why does Hodgkin lymphoma have a better outlook?
   Show answer

   It stays in one area and spreads node to node, so it gets caught earlier. It hits younger patients, who handle treatment better. It also responds strongly to chemo and radiation.

✅ Multiple Choice Practice

1. HIV is a:
   A) DNA virus · B) Retrovirus · C) Bacteria · D) Fungus
   Show answer

   B. A retrovirus. It uses reverse transcriptase to slip its genes into the host's DNA.
2. Reed-Sternberg cells point to:
   A) Acute leukemia · B) Hodgkin lymphoma · C) Non-Hodgkin lymphoma · D) Kaposi sarcoma
   Show answer

   B. Hodgkin lymphoma.
3. Which of these are AIDS-defining illnesses? (SATA)
   A) Common cold · B) Kaposi sarcoma · C) PCP pneumonia · D) Thrush in the mouth · E) Strep throat
   Show answer

   B, C. Kaposi sarcoma and PCP are AIDS-defining. Thrush in the mouth is common with a weak immune system, but on its own it is not AIDS-defining.