Exam 3: Mammalian Physiology - Respiratory, Digestive, and Urinary Systems

Comprehensive vocabulary flashcards covering the digestive, respiratory, and urinary systems, including physiology mechanisms, anatomical landmarks, neural pathways, key clinical cases, and historical milestones.

Enteric Nervous System (ENS)

The intrinsic nervous system of the gastrointestinal tract capable of coordinating digestive reflexes independently of the central nervous system.

Myenteric Plexus

The network of enteric neurons located between the longitudinal and circular muscle layers of the gut that controls gastrointestinal motility and muscle contractions.

Submucosal Plexus

The enteric neural network situated beneath the intestinal mucosal lining that regulates local blood flow and glandular secretions.

Peristalsis

A coordinated gastrointestinal reflex where sensory neurons trigger acetylcholine ($\text{ACh}$) release to contract circular muscle behind a bolus, while releasing nitric oxide ($\text{NO}$) and vasoactive intestinal peptide ($\text{VIP}$) to relax muscle ahead, propelling contents forward.

Law of the Intestine

The physiological principle established by Bayliss and Starling in 1899 describing the localized reflex pattern of contraction behind an intestinal bolus and simultaneous receptive relaxation downstream.

Gastrin

A peptide hormone produced by stomach $G$ cells in response to protein and gastric distension that stimulates parietal cells to increase hydrochloric acid ($\text{HCl}$) secretion.

Secretin

A gastrointestinal hormone discovered in 1902 by Bayliss and Starling, released by duodenal $S$ cells in response to acidic chyme, which stimulates the exocrine pancreas to secrete bicarbonate.

Cholecystokinin (CCK)

A hormone synthesized by duodenal $I$ cells in response to intraluminal fat and protein that stimulates gallbladder contraction to eject bile and triggers pancreatic digestive enzyme secretion.

Parietal Cells

Epithelial cells located in the gastric mucosa that secrete hydrochloric acid ($\text{HCl}$) and intrinsic factor, a glycoprotein necessary for the absorption of vitamin $\text{B}_{12}$.

Chief Cells

Gastric zymogenic cells that secrete inactive pepsinogen, which is converted to active proteolytic pepsin in the presence of acidic gastric juice ($\text{HCl}$).

Cephalic Phase of Gastric Secretion

The initial phase of digestion accounting for approximately $30\%$ of gastric acid secretion, stimulated by the thought, sight, smell, or taste of food via vagal parasympathetic pathways.

Helicobacter pylori

A spiral-shaped bacterium that causes the vast majority of peptic and gastric ulcers, treated clinically with antibiotic regimens.

Biliary System Anatomy

The network of ducts and organs comprising the left and right hepatic ducts, common hepatic duct, cystic duct, gallbladder, and common bile duct responsible for channeling and concentrating bile.

Bile Emulsification

The physical process in which amphipathic bile salts use their hydrophobic tails and hydrophilic heads to break large dietary lipid droplets into tiny droplets, increasing surface area for pancreatic lipase activity.

Chylomicrons

Lipoprotein particles synthesized in enterocytes that package absorbed dietary lipids and enter intestinal lymphatic capillaries (lacteals) before reaching systemic blood circulation.

Hirschsprung Disease

A congenital disorder characterized by the absence of enteric ganglion cells along a distal portion of the colon, preventing peristaltic movement and causing functional bowel obstruction in newborns.

Cholelithiasis (Gallstone Disease)

A condition in which excess cholesterol crystallizes into stones within the gallbladder; ingestion of a fatty meal stimulates $CCK$ release, provoking forceful gallbladder contraction against a blocked cystic duct and causing severe pain under the right ribs.

Acute Pancreatitis

Inflammation of the pancreas caused by premature intraductal activation of zymogens, such as trypsinogen converting to trypsin, resulting in enzymatic autodigestion, back-radiating abdominal pain, and elevated serum lipase and amylase levels.

Celiac Disease

An autoimmune enteropathy triggered by ingested gluten (wheat protein) in genetically susceptible individuals, resulting in immune destruction of small intestinal villi (villous atrophy), nutrient malabsorption, diarrhea, weight loss, and anemia.

Diaphragm

The primary skeletal muscle responsible for quiet inspiration; when stimulated, it contracts, flattens, and descends, increasing thoracic volume and decreasing alveolar pressure.

Phrenic Nerve

The peripheral somatic motor nerve arising from cervical spinal cord roots $\text{C3}$, $\text{C4}$, and $\text{C5}$ that innervates the diaphragm; spinal cord lesions above $\text{C3}$ cause diaphragmatic paralysis and respiratory arrest.

Boyle's Law

The physical law stating that the pressure of a given mass of gas is inversely proportional to its volume at constant temperature ($P \propto \frac{1}{V}$); expansion of the thoracic cavity lowers intrapulmonary pressure below atmospheric levels, driving airflow inward.

Intrapleural Pressure

The subatmospheric pressure within the pleural space, measuring approximately $-4\,\text{mmHg}$ ($756\,\text{mmHg}$ relative to atmospheric $760\,\text{mmHg}$) during normal resting conditions, which creates suction that prevents lung collapse.

Pneumothorax

A medical emergency where thoracic wall puncture allows atmospheric air ($760\,\text{mmHg}$) into the intrapleural space, raising pleural pressure from $-4\,\text{mmHg}$ to $0\,\text{mmHg}$ and causing lung collapse due to unopposed elastic recoil.

Fick's Law of Diffusion

The physical principle determining that the rate of gas transfer across a membrane is directly proportional to surface area and partial pressure difference, and inversely proportional to membrane thickness.

Central Chemoreceptors

Sensory neurons located on the ventrolateral medulla oblongata that detect increases in brain interstitial hydrogen ion concentration resulting from elevated arterial $\text{CO}_2$, serving as the primary minute-to-minute driver of respiratory rate and depth.

Pre-Bötzinger Complex

A specialized cluster of interneurons situated in the rostral ventrolateral medulla that acts as the autonomic rhythm generator and pacemaker for mammalian breathing.

Kölliker-Fuse Area

A pontine respiratory nucleus involved in modulating breathing patterns and rhythmogenesis alongside medullary respiratory groups.

High-Altitude Hypoxia (Mount Everest)

A condition occurring at extreme elevations (such as $8{,}400\,\text{m}$, barometric pressure $272\,\text{mmHg}$) where the fractional concentration of oxygen remains $21\%$, but total barometric pressure drop reduces alveolar $P(\text{O}_2)$ to $\approx 30\,\text{mmHg}$ and arterial $P(\text{O}_2)$ to $\approx 25\,\text{mmHg}$.

Erythropoietin (EPO)

A glycoprotein hormone synthesized and released by renal interstitial cells in response to chronic tissue hypoxia, stimulating red blood cell production in bone marrow to elevate oxygen-carrying capacity over weeks.

Asthma

An inflammatory airway pathology characterized by bronchial smooth muscle hyperreactivity, mucosal edema, and luminal mucus plugging, halving airway radius ($r \rightarrow \frac{r}{2}$) and increasing airway resistance by $16\times$ according to Poiseuille's relationship.

Albuterol

A short-acting $\beta_2$-adrenergic receptor agonist medication that binds bronchial smooth muscle receptors to induce bronchodilation during acute bronchospasm.

Opioid-Induced Respiratory Depression

Hypoventilation and fatal respiratory arrest resulting from exogenous opioids binding to $\mu$-opioid receptors on the pre-Bötzinger complex and Kölliker-Fuse neurons, decreasing pacemaker activity and blunting the medullary ventilatory response to hypercapnia.

Naloxone (Narcan)

A high-affinity competitive antagonist at $\mu$-opioid receptors that displaces opioid molecules from brainstem respiratory centers to restore spontaneous ventilation.

Cyanide Toxicity

Cellular chemical asphyxiation caused by cyanide binding and inhibiting Cytochrome c Oxidase (Complex $\text{IV}$) in the inner mitochondrial membrane, halting the electron transport chain despite normal arterial oxygen content.

Pulmonary Fibrosis

A restrictive lung disorder involving interstitial collagen deposition that thickens the alveolar-capillary barrier, reducing gas diffusion capacity according to Fick's law and causing exercise-induced hypoxemia.

Shallow Water Blackout

Loss of consciousness during an underwater dive caused by voluntary hyperventilation beforehand, which clears systemic $\text{CO}_2$ without adding significant $\text{O}_2$, delaying the hypercapnic urge to breathe until cerebral hypoxia causes blackout.

Nephron

The structural and functional microscopic unit of the kidney, consisting of an initial filtering corpuscle (glomerulus and Bowman's capsule) connected to a specialized epithelial tubular system.

Glomerular Filtration

The non-selective size-dependent process driven by renal arterial hydrostatic pressure where roughly $160\,\text{L/day}$ of plasma water and solutes (glucose, ions, urea) pass into Bowman's space while erythrocytes and large proteins are retained.

Proximal Convoluted Tubule (PCT)

The highly coiled segment of the nephron downstream of the glomerulus responsible for reabsorbing approximately $65\%$ of filtered water, most sodium, and virtually all filtered glucose and amino acids.

Antidiuretic Hormone (ADH)

A neurohypophyseal nonapeptide hormone released by the posterior pituitary that inserts aquaporin water channels into collecting duct principal cell membranes, facilitating water reabsorption into the hypertonic medullary interstitium.

Diabetes Insipidus

A pathological state characterized by deficient production or impaired renal receptor responsiveness to antidiuretic hormone ($\text{ADH}$), resulting in failure of collecting duct water reabsorption and excretion of high-volume, highly dilute urine.

Juxtaglomerular (JG) Cells

Specialized smooth muscle cells in afferent arterioles that synthesize, store, and secrete the enzymatic hormone renin in response to decreased renal perfusion pressure or sympathetic stimulation.

Renin-Angiotensin-Aldosterone System (RAAS)

A systemic endocrine cascade triggered by renal hypoperfusion wherein renal renin cleaves hepatic angiotensinogen into angiotensin $\text{I}$, which is converted by pulmonary endothelial $ACE$ into angiotensin $\text{II}$, subsequently inducing vasoconstriction and adrenal aldosterone synthesis.

Angiotensin-Converting Enzyme (ACE)

An ectoenzyme localized primarily to the luminal endothelial surface of pulmonary capillary vascular beds that converts inactive decapeptide angiotensin $\text{I}$ into biologically potent octapeptide angiotensin $\text{II}$.

Aldosterone

A steroid hormone synthesized and released by the adrenal cortex (zona glomerulosa) that acts on late distal tubules and collecting ducts to stimulate sodium and water retention while promoting urinary potassium ($\text{K}^+$) elimination.

Atrial Natriuretic Peptide (ANP)

A cardiac peptide hormone released by atrial myocytes in response to excessive atrial stretch and vascular volume expansion that antagonizes the $RAAS$ cascade by stimulating renal sodium and water excretion.

Rhabdomyolysis

A clinical syndrome resulting from skeletal muscle breakdown (via trauma, crush injury, or extreme exertion) where released myoglobin passes through the glomerular filter, precipitating into casts that plug renal tubules and releasing nephrotoxic iron.

SGLT2 (Sodium-Glucose Cotransporter 2)

A high-capacity, low-affinity apical membrane carrier protein situated in the proximal convoluted tubule responsible for reabsorbing approximately $90\%$ of filtered glucose alongside sodium.

Phlorizin

A naturally occurring glucoside isolated from apple tree bark in 1835 found to induce glucosuria by competitively inhibiting renal sodium-glucose cotransporters, providing the molecular basis for $SGLT2$ inhibitor drugs.

Renal Artery Stenosis

Atherosclerotic narrowing of the renal artery that drops post-stenotic perfusion pressure to the ipsilateral kidney, tricking juxtaglomerular cells into sustained excess renin secretion and causing severe secondary systemic arterial hypertension.

Goldblatt Experiment (1934)

A classic physiological experiment demonstrating that placing a partial constricting clamp on a renal artery causes persistent renin secretion and widespread systemic hypertension, mimicking clinical renal artery stenosis.