Lecture Notes Flashcards: Body Fluids, Homeostasis, and Cell Biology

Vocabulary flashcards covering key terms from the lecture notes.

Intracellular fluid (ICF)

Fluid inside cells; ~25 L in a 70 kg adult; ~2/3 of total body water; high in K+, Mg2+, phosphate, sulfate, and proteins.

Extracellular fluid (ECF)

Fluid outside cells; ~15 L; ~1/3 of total body water; high in Na+, Cl−, Ca2+, HCO3−, glucose, amino acids, lipids, O2, CO2, hormones, and enzymes.

Interstitial fluid

Part of the ECF that bathes cells in the tissue spaces; excess interstitial fluid = edema.

Transcellular fluid

Small, specialized subset of the ECF (e.g., CSF, bile, urine, synovial fluid); ~0.5 L.

Edema

Excess interstitial fluid causing swelling.

Homeostasis

Maintenance of constant conditions in the internal environment (ECF) by coordinated organ systems (Lungs, CVS, kidneys, GIT).

Negative feedback

Regulatory mechanism that opposes a change to stabilize the system (e.g., BP, blood glucose, temperature).

Positive feedback

Amplifies a change, leading to destabilization; examples include blood clotting, labor contractions, and some pathologic states.

Calcium homeostasis

Regulation of blood Ca2+ by calcitonin, parathyroid hormone (PTH), and vitamin D (calcitriol).

Calcitonin

Thyroid hormone that lowers blood Ca2+ by reducing bone resorption and increasing renal excretion.

Calcitriol (Vitamin D)

Active vitamin D that increases intestinal Ca2+ absorption and promotes bone mineralization.

PTH (Parathyroid hormone)

Hormone that raises Ca2+ levels by acting on bone, kidney, and intestine.

Antagonistic calcium control

Calcitonin lowers Ca2+ while PTH and vitamin D raise Ca2+.

Osteopenia

Lower-than-normal bone density; can progress to osteoporosis; linked to vitamin D and Ca2+ deficiency.

Osteoporosis

Weak, fragile bones due to decreased bone mineral density.

Normal fasting blood glucose

Typically 70–110 mg/dL (often cited 80–120 mg/dL).

Insulin

Hypoglycemic hormone; lowers blood glucose.

Glucagon

Hyperglycemic hormone; raises blood glucose.

Hyperglycemia

Elevated blood glucose; central feature of diabetes mellitus when insulin action is defective.

Hypoglycemia

Low blood glucose.

Osmolality

Concentration of osmotically active particles in a solution; normal range ~285–300 mosm/L.

pH

Acidity/alkalinity of body fluids; normal arterial blood pH ~7.35–7.45.

PCO2

Partial pressure of CO2 in blood; normal ~35–45 mmHg; helps regulate pH.

PO2

Partial pressure of O2 in blood; normal ~40–104 mmHg.

Sodium (Na+)

ECF cation; normal ~142 meq/L.

Potassium (K+)

ICF and ECF cation; normal ~4 meq/L.

Calcium (Ca2+)

Important for bone and metabolic functions; normal ~10 mg/dL (≈5 meq/L).

Chloride (Cl−)

ECF anion; normal ~103 meq/L.

Bicarbonate (HCO3−)

Primary serum buffer; normal ~27 meq/L.

Bilirubin

Bile pigment; normal ~0.5 mg/dL.

Creatinine

Renal function marker; normal ~0.6–1.5 mg/dL.

BUN

Blood urea nitrogen; normal ~8–25 mg/dL.

Uric acid

Purine breakdown product; normal women ~2.3–6.6 mg/dL, men ~3.6–8.5 mg/dL.

Blood pressure terms

Systolic ~120 mmHg (90–140); Diastolic ~80 mmHg (60–90); Pulse pressure ~40 mmHg; Mean BP ~96 mmHg.

RBC count

Red blood cells; ~4–6 million/mm3.

WBC count

White blood cells; ~4,000–11,000/mm3.

Hemoglobin (Hb)

Oxygen-carrying protein in blood; ~12–18 g/dL in females and ~14–20 g/dL in males.

Plasma membrane

Cell membrane with 55% proteins, 42% lipids (cholesterol ~13%, neutral fats ~4%), and 3% carbohydrates; functions include barrier, receptors, and signal transduction.

Glycocalyx

Carbohydrate-rich layer of glycoproteins and glycolipids on the cell surface; involved in blood group antigens, cell recognition, and immune reactions.

ABO and Rh antigens

Glycocalyx-based blood group antigens determining transfusion compatibility.

Nucleus

Control center of the cell; contains DNA; nucleolus makes rRNA.

Rough endoplasmic reticulum (RER)

ER with ribosomes; protein synthesis and export.

Smooth endoplasmic reticulum (SER)

ER without ribosomes; lipid synthesis, Ca2+ storage, glycogen storage, and detoxification.

Golgi apparatus

Organelle that modifies and packages proteins for secretion or delivery; forms lysosomes.

Lysosomes

Digest damaged organelles and bacteria; disorders include Tay-Sachs and Pompe disease.

Peroxisomes

Contain oxidases and catalase; detoxification of harmful substances.

Mitochondria

ATP production; contain DNA; capable of self-replication.

Membrane transport modes

Categories include diffusion, osmosis, facilitated diffusion, active transport, secondary active transport, co-transport, counter-transport, transcytosis, endocytosis, phagocytosis, pinocytosis, and exocytosis.

Simple diffusion

Passive movement of lipid-soluble substances down a concentration gradient.

Osmosis

Water movement across membranes through aquaporins driven by osmotic pressure.

Facilitated diffusion

Carrier-mediated, saturable transport (no ATP); e.g., glucose.

Active transport

Energy-dependent transport requiring ATP; examples include Na+/K+ ATPase, H+/K+ ATPase, Ca2+ ATPase.

Secondary active transport

Coupled transport (co-transport) using Na+ gradient to move substances like glucose or amino acids.

Counter-transport

Transport in which one ion moves in while another moves out (e.g., Na+/Ca2+, Na+/H+).

Transcytosis

Transport of substances across epithelial sheets (e.g., intestine, renal tubules) via vesicles.

Endocytosis

Cellular uptake of material; includes pinocytosis (drinking) and phagocytosis (eating); receptor-mediated endocytosis (RME) is a targeted form.

Exocytosis

Release of substances from a cell via vesicular fusion with the membrane.

Cystic fibrosis

Defective Cl− channel causing thick mucus, infections, and pancreatic insufficiency.

Intercellular communication modalities

Contact-dependent, endocrine, paracrine, synaptic, and autocrine signaling.

Clinical correlations: Graves’ disease

Autoantibodies bind thyroid receptors, affecting thyroid function.