Clinical Review Sheet Final Lab Exam

Bleeding in the right internal capsule paralyzes the left side. Why the opposite side?

The internal capsule contains the corticospinal tract, where fibers decussate in the medulla oblongata. A vascular stroke or hemorrhage in the right internal capsule interrupts signals sent to the opposite (left) side of the body, producing contralateral paralysis.

Why is brainstem trauma more dangerous than frontal lobe trauma?

The brainstem contains the pons and the medulla, which control vital autonomic centers for heart rate, blood pressure, and respiration. Damage to the frontal lobe impairs high-order voluntary functions, whereas the brain stem damage stops cardiac and respiratory functions, which are life-threatening.

The chickenpox virus hides in dorsal root ganglia

and can return as shingles. Can shingles happen

more than once? Why?

The varicella-zoster virus remains dormant in sensory cell bodies within the dorsal root ganglia. Shingles can recur because the virus persists in nerve ganglia throughout life and can reactivate when immunity drops due to stress, illness, or aging.

A patient has wrist drop. Which nerve is most likely

injured, and why?

Wrist drop is caused by injury to the radial nerve, which supplies the extensor muscles of the wrist and fingers. When damaged, the patient loses the ability to extend the wrist joint, leaving the hand hanging.

How could damage to a muscle, a sensory neuron or

a motor neuron cause weak reflexes (hyporeflexia)?

The reflex arc requires a receptor, a sensory neuron, an integration center, a motor neuron, and an effector muscle to function. Damage to any step disrupts impulse transmission along the arc, resulting in weak or absent reflex responses (hyporeflexia).

Tetanus toxin makes opposing muscles contract

together (lockjaw). What process does it block, and

how does that affect stretch reflexes?

Tetanus toxin blocks inhibitory interneurons that normally relax antagonist muscles during contractions. Without inhibition, opposing agonist and antagonist muscles contract together (causing lockjaw spasms), and the stretch reflex becomes hyperactive.

Use visual field loss patterns to locate a lesion along

the visual pathway.

Visual field patterns isolate lesion locations along the pathway: a lesion in one optic nerve causes total blindness in that eye; a lesion at the optic chiasma causes loss of peripheral visual fields; a lesion in an optic tract or radiation causes opposite visual field loss in both eyes.

Why does a cornea transplant heal slowly, and why

is rejection rare?

The cornea is avascular (lacks blood vessels), receiving oxygen and nutrients solely by diffusion from aqueous humor. Because it lacks direct blood flow, cell repair and wound healing are very slow, but immune cells and antibodies cant reach tissues, making transplant rejection rare.

Why does macular degeneration harm vision more

than damage elsewhere in the retina?

The macula lutea and fovea centralis contain the highest density of cone photoreceptors responsible for high-acuity central vision. Macular degeneration damages this area, destroying central visual acuity while leaving peripheral retinal vision intact.

Strabismus and the "near triad": which reflex is

affected, and are intrinsic or extrinsic eye muscles

involved?

Strabismus affects the accommodation-convergence reflex (lens accommodation, pupil constriction, and eye convergence). It involves the extrinsic eye muscles, which are uncoordinated, preventing both eyes from aligning on a target.

Acute labyrinthitis: which structures can be inflamed, and what symptoms would you expect?

Acute labyrinthitis is inflammation of the inner ear structures, specifically the semicircular canals, vestibule, and cochlea. Patients experience severe equilibrium loss, dizziness, and vertigo combined with tinnitus or hearing loss.

Why does plasmapheresis before and after a kidney

transplant make rejection unlikely when blood types

differ?

Plasmapheresis removes pre-existing donor-specific antibodies and circulating plasma proteins from the recipient’s bloodstream. Removing these antibodies before and after surgery prevents hyperacute and acute tissue rejection, even when donor and recipient blood types differ.

Why can a low platelet count (thrombocytopenia)

cause abnormal bleeding?

Platelets (thrombocytes) are essential for initiating blood clotting and forming a platelet plug during hemostasis. A low platelet count prevents clot formation, resulting in easy bruising and uncontrolled bleeding.

Why is a blockage of the left anterior descending (LAD) artery called the “widow maker”?

The LAD coronary artery supplies oxygenated blood to the anterior wall of the left ventricle and the interventricular septum. Blockage impairs the primary systemic pumping chamber, causing fatal cardiac arrest or a myocardial infarction.

Congestive heart failure: where does edema form

when the left side fails vs the right side?

When the left side of the heart fails, blood backs up into the pulmonary circulation, causing pulmonary edema (fluid in the lungs). When the right side fails, blood backs up into the systemic veins, causing peripheral edema (swelling in the legs, feet, and abdomen).

Atrial fibrillation: how could scar tissue from a maze

procedure stop it?

The maze procedure creates scar tissue lines across the atrial walls. Because scar tissue does not conduct electrical impulses, it blocks chaotic reentry pathways while forcing impulses to travel cleanly from the SA node to the AV node.

Long QT syndrome: what electrical events happen

during the Q–T interval?

The Q-T interval represents ventricular depolarization and repolarization time. Long QT syndrome means a delayed ventricular repolarization time. Long QT syndrome means delayed ventricular repolarization, which extends the vulnerable cardiac cycle period and increases the risk of ventricular tachycardia.

A PICC line goes into the right cephalic vein. Trace

the medication's route to the right atrium.

Medication administered into the right cephalic vein flows into the right subclavian vein, then into the right brachiocephalic vein, and enters the superior vena cava to reach the right atrium.

A clot in the femoral vein (DVT). Trace its route to

the pulmonary artery.

A deep vein thrombosis (DVT) clot breaks free from the femoral vein, travels into the external iliac vein, common iliac vein, inferior vena cava, right atrium, tricuspid valve, right ventricle, pulmonary semilunar valves, and pulmonary trunk into the pulmonary arteries, where it lodges as a pulmonary embolism.

A left ventricular assist device (LVAD) pumps blood

from the left ventricle to the aorta. Which cardiac

cycle phase does it assist, and what are the valves

doing?

A left ventricular assist device LVAD assists during ventricular systole by actively pumping blood from the left ventricle into the ascending aorta. During this action, the mitral valve is closed to prevent backflow, while the aortic semilunar valve is bypassed.

Why is dehydration a risk factor for fainting during

urination in older men?

Micturition triggers parasympathetic activation that lowers heart rate and causes vasodilation. In dehydrated men with low blood volume, this sudden drop in blood pressure impairs brain blood flow, leading to syncope during urination.

Lymphedema: why would exercise help move lymph

out of a swollen limb?

Lymphatic vessels lack a heart pump and rely on skeletal muscle contraction, thoracic pressure changes during breathing, and one-way valves to move fluid. Physical exercise squeezes lymph vessels, driving excess interstitial fluid out of swollen limbs back into venous blood.

Buboes are swollen lymph nodes in bubonic plague.

Where on the body would they most likely form?

Buboes are painfully swollen lymph nodes forming in major regional node clusters draining infection sites. They appear most frequently in the inguinal, axillary, and cervical nodes.

Why is an inflamed epiglottis (epiglottitis) life-

threatening?

The epiglottis covers the glottis during swallowing to prevent aspiration into the trachea. Severe inflammation and swelling of the epiglottis obstruct the upper airway at the larynx entrance, leading to suffocation.

How does pneumonia lower blood oxygen

saturation?

Pneumonia fills alveoli with fluid and inflammatory exudate, thickening the respiratory membrane. This barrier impairs gas diffusion across alveolar walls, preventing oxygen from reaching RBC hemoglobin.

What signs would an infant with pyloric stenosis show?

Pyloric stenosis is hypertrophy of the pyloric sphincter, preventing stomach contents from entering the duodenum. Affected infants present with severe projectile vomiting after feedings, persistent hunger, dehydration, weight loss, and a palpable olive-shaped abdominal mass.

Why can people live without a gallbladder, and what

diet changes might help after removal?

Bile is synthesized by the liver; the gallbladder only stores and concentrates it. After cholecystectomy, bile trickles constantly into the duodenum, requiring patients to reduce dietary fat intake and avoid high-fat meals to prevent indigestion and diarrhea.

Celiac disease: why would gluten-digesting enzyme

pills not work in the stomach?

Gluten-digesting enzyme pills taken orally encounter strong stomach HCl and pepsin. This denatures enzyme proteins, inactivating them before they reach the small intestine, where celiac mucosal damage occurs.

Cystic fibrosis: how does reduced pancreatic

enzyme secretion affect digestion?

In cystic fibrosis, a thick mucus plug blocks the pancreatic ducts, preventing digestive enzymes (lipase, protease, amylase) from reaching the duodenum. This leads to severe fat and nutrient malabsorption, malnutrition, and steatorrhea.

Why are females more likely to get urinary tract

infections?

Females have a shorter urethra that opens in proximity to the anal orifice. This short distance allows enteric bacteria to easily migrate into the urinary bladder.

Glomerulonephritis damages the filtration

membrane. What abnormal substances appear in

the urine?

Glomerulonephritis inflames and damages the glomerular filtration membrane, increasing its permeability. Consequently, large blood proteins (proteinuria) and intact red blood cells (hematuria) leak into the renal filtrate and appear in urine^[23]

Why are patients with hyperparathyroidism at risk

for kidney stones?

Hyperparathyroidism causes excessive parathyroid hormone (PTH) secretion, elevating blood calcium (hypercalcemia) through bone breakdown and renal reabsorption. Excess calcium filtered into the renal tubules precipitates with oxalate or phosphate to form calcium kidney stones

Why does a UTI caused by Proteus mirabilis raise

urine pH?

Proteus mirabilis produces the enzyme urease, which breaks down urea into ammonia (NH₃). Ammonia acts as a strong base, raising urine pH (alkaline urine, pH > 7.0–8.0) and favoring kidney stone formation.

Why can undescended testes (cryptorchidism) cause

sterility if not corrected?

Because sperm need a cooler temperature (2–3°C below body temp) to develop properly, being held inside the warmer pelvic cavity causes thermal damage that prevents sperm production, leading to sterility.

During a hysterectomy, why is it an advantage to

leave the ovaries in place?

Leaving ovaries intact during a hysterectomy maintains natural estrogen and progesterone hormone production^[26]. This prevents immediate surgical menopause, preserving bone density, cardiovascular health, and endocrine balance^[26].