Units 8-12 Practice Flashcards: Case Studies and Clinical Applications

A comprehensive set of vocabulary flashcards covering Units 8 through 12, focusing on homeostatic mechanisms, neurophysiology, muscle pathology, and various clinical case studies derived from the lecture notes.

Homeostasis

The relative constancy of the chemical composition of blood and extracellular fluid despite external variation, a term coined by Walter Cannon.

Internal Environment

The concept proposed by Claude Bernard that vertebrates maintain internal constancy to allow tight regulation of cellular metabolism.

Resting Membrane Potential ($V_m$)

The electrical potential across a cell membrane, measured at $-70\,mV$ on average, sitting between $-65\,mV$ and $-85\,mV$ because roughly $30\%$ of $K^+$ leak channels remain open.

Potassium ($K^+$) Gradient

The concentration difference where intracellular $[K^+]$ is $150\,mEq/L$ and extracellular $[K^+]$ is $5\,mEq/L$, resulting in an equilibrium potential ($E_K$) of $-90\,mV$.

Acute Gastroenteritis & Cholera Pathophysiology

Infection causing severe diarrhea leading to loss of $Na^+$, $H_2O$, malnutrition, and metabolic acidosis.

Oral Rehydration Therapy (ORT)

A treatment including glucose to co-transport $Na^+$ across the intestinal epithelium via $Na^+/\text{glucose}$ symporters, pulling water back into the body by osmosis.

Hyperkalemia

Abnormally high plasma $[K^+]$ which depolarizes the resting membrane potential closer to threshold, initially causing hyperexcitability but ultimately disrupting repolarization and causing ECG abnormalities.

Hypokalemia

Abnormally low plasma $[K^+]$ which hyperpolarizes the resting potential further from threshold, making cells harder to excite and causing muscle weakness.

Guillain-Barré Syndrome

A T-cell-mediated autoimmune attack against peripheral nervous system (PNS) myelin sheaths, leading to motor neuron dysfunction and progressive muscle weakness.

Multiple Sclerosis (MS)

An autoimmune disorder where T-lymphocytes and macrophages breach the blood-brain barrier to attack central nervous system (CNS) myelin sheaths, leading to neuroglia scarring (plaques) and axonal degeneration.

Local Anesthetics (e.g., Procaine, Cocaine)

Drugs that reversibly bind and block voltage-gated $Na^+$ channels in axonal membranes, preventing depolarization and action potential generation.

SNARE Complex

A group of proteins that interact with synaptotagmin and $Ca^{2+}$ to trigger vesicle exocytosis of neurotransmitters into the synaptic cleft.

Tetanus Toxin

A bacterial neurotoxin that cleaves SNARE proteins in inhibitory interneurons releasing GABA/glycine, resulting in uninhibited motor firing and spastic paralysis.

Botulinum Toxin

A toxin that cleaves SNARE proteins at excitatory neuromuscular junctions, blocking acetylcholine (ACh) release and producing flaccid paralysis.

Myasthenia Gravis

A condition where autoantibodies bind and block or destroy post-synaptic nicotinic ACh receptors at the motor endplate of skeletal muscle.

Organophosphates & Nerve Gas

Chemicals that irreversibly inhibit Acetylcholinesterase (AChE), causing massive ACh accumulation and lethal cholinergic overstimulation.

MAO Inhibitors Mechanism

Drugs that block Monoamine Oxidase to prevent the degradation of dopamine, serotonin, epinephrine, and norepinephrine.

Benzodiazepines (e.g., Valium, Xanax)

Drugs that allosterically bind $GABA_A$ receptors to increase $Cl^-$ influx, hyperpolarizing post-synaptic membranes to depress CNS activity.

Excitotoxicity

A pathological process where excessive glutamate release hyper-activates receptors, causing massive intracellular $Ca^{2+}$ influx and neuronal apoptosis, observed in ischemic stroke and ALS.

Duchenne Muscular Dystrophy (DMD)

An X-linked recessive mutation in the dystrophin gene which anchors myofibrils to the sarcolemma; contraction stress causes sarcolemma tears and muscle necrosis.

Rhabdomyolysis

The breakdown of muscle fibers due to trauma or extreme exertion, releasing Creatine Kinase (CK-MM isoenzyme) and myoglobin into the blood.

Amyotrophic Lateral Sclerosis (ALS)

Progressive neurodegeneration of both Upper Motor Neurons (UMN) and Lower Motor Neurons (LMN) often involving superoxide dismutase (SOD1) mutations and ROS damage.

Spastic Paralysis

Paralysis caused by UMN or descending tract damage, removing inhibitory control over spinal $\gamma$-motor neurons and leading to hyperreflexia and clonus.

Calcium Channel Blockers

Pharmacological agents that block L-type voltage-gated $Ca^{2+}$ channels; dihydropyridines act on vascular smooth muscle, while Verapamil acts on cardiac pacemaker activity.

Huntington's Disease

An autosomal dominant mutation involving CAG expansion in the HTT gene on chromosome 4, leading to loss of GABAergic/cholinergic neurons and involuntary chorea.

Parkinson's Disease

A movement disorder caused by the degeneration of dopaminergic neurons in the substantia nigra of the midbrain.

Cerebellar Ataxia

Loss of voluntary coordination and a wide-based gait resulting from damage to the cerebellum, impairing the integration of proprioceptive and vestibular input.

Beta-Blockers ($\beta_1$ antagonists)

Drugs that lower heart rate and blood pressure; non-selective versions can cause bronchoconstriction via $\beta_2$ blockade.

Atropine

A competitive antagonist of muscarinic ACh receptors used to treat bradycardia and serve as an antidote for organophosphate poisoning.

Autonomic Dysreflexia

A condition occurring in spinal cord injuries at or above T6 where a noxious stimulus below the lesion triggers massive, uninhibited sympathetic vasoconstriction.

Pneumothorax

A condition where air breaches the intrapleural space, causing the loss of negative transmural pressure and resulting in lung collapse.

Neonatal Respiratory Distress Syndrome (RDS)

A lack of surfactant produced by Type II alveolar cells which increases alveolar surface tension and leads to diffuse atelectasis.

Pulse Oximetry

A diagnostic method emitting $660\,nm$ red and $940\,nm$ infrared light to measure the absorption ratios of Oxy-Hb vs. Deoxy-Hb.

Carbon Monoxide (CO) Poisoning

CO binds hemoglobin with more than $200\times$ higher affinity than $O_2$, forming carboxyhemoglobin (CO-Hb) and preventing $O_2$ unloading to tissues.

Ondine's Curse (CCHS)

A mutation in the retrotrapezoid nucleus of the medulla oblongata that abolishes the automatic respiratory response to elevated arterial $P_{CO_2}$.

Respiratory Alkalosis via Hyperventilation

A high blood pH caused by excessive "blowing off" of $CO_2$, which lowers ionized plasma $Ca^{2+}$ and causes neuromuscular tetany.

Barrett's Esophagus

Metaplasia where esophageal stratified squamous epithelium is replaced by acid-resistant simple columnar epithelium due to chronic GERD.

Proton Pump Inhibitors (PPIs)

Drugs used to treat GERD by inhibiting the parietal cell $H^+/K^+$ ATPase pumps.

Lactose Intolerance

A deficiency of the brush border lactase enzyme, leading to undigested lactose exerting osmotic force and causing diarrhea.

Celiac Disease

An autoimmune reaction to gluten that destroys duodenal and jejunal villi, flattening the surface area and causing severe malabsorption.

Crohn's Disease

A type of inflammatory bowel disease characterized by transmural inflammation and fibrotic skip lesions throughout the GI tract.

Ulcerative Colitis

Inflammatory bowel disease involving mucosal and submucosal erosion that starts in the rectum and progresses proximally through the colon.

Liver Cirrhosis

The replacement of hepatic lobules with non-functional fibrotic scar tissue, leading to portal hypertension and impaired toxin clearance.

Pre-hepatic Jaundice

Yellowing of tissues caused by excessive hemolysis (e.g., Sickle Cell) which overwhelms the liver's conjugation capacity.

Post-hepatic Jaundice

Jaundice caused by biliary tree obstruction, such as gallstones, which blocks bile drainage into the duodenum.

Cytochrome P450 (CYP3A4) and Grapefruit

Grapefruit juice inhibits this enzyme in hepatocytes, slowing drug breakdown and causing toxic accumulation in plasma.

Pancreatitis Pathophysiology

The premature intracellular activation of pancreatic zymogens (e.g., trypsinogen to trypsin) causing enzymatic auto-digestion of pancreatic tissue.