Physiology, Cell Structure , and Body Fluid Homeostasis 1

Vocabulary flashcards covering major terms from Lecture 1 on physiology, cell structure/function, fluid compartments, and homeostatic mechanisms.

Physiology

The study of the functions and mechanisms that operate within living systems, focusing on how cells, tissues, and organs work and interact.

Homeostasis

The body’s ability to maintain a stable internal environment despite external changes, typically via feedback loops.

Cell

The basic unit of life whose structure-function relationships underpin tissue and organ physiology.

Nucleus

Function: contains DNA site of transcription

Membrane-bound organelle containing DNA; site of transcription and regulation of gene expression.

Central Dogma

Flow of genetic information from DNA → RNA → protein; can reverse via reverse transcriptase.

Mitochondria

Powerhouse of the cell that produces ATP through aerobic respiration and oxidative phosphorylation; possesses its own (maternal) DNA.

Electron Transport Chain (ETC)

Series of protein complexes (I–IV) in the inner mitochondrial membrane that transfer electrons to O₂ while pumping protons to generate an electrochemical gradient.

Proton Gradient

(Chemiosmosis)

H⁺ ions are pumped into the intermembrane
space
• Creates an electrochemical gradient (proton
motive force)

ATP Generation

Protons flow back into the matrix via ATP
synthase
• Drives phosphorylation of ADP → ATP

ATP Synthase (Complex V)

Enzyme that uses the proton motive force to convert ADP and Pi into ATP.

Oxidative Phosphorylation

Process by which energy from electrons (NADH, FADH₂) is used to pump protons and drive ATP synthesis in mitochondria.

Rough Endoplasmic Reticulum (RER)

Organelle studded with ribosomes; synthesizes proteins destined for secretion or membrane insertion.

Smooth Endoplasmic Reticulum (SER)

Organelle lacking ribosomes; synthesizes lipids/steroids and detoxifies drugs (cytochrome P450).

Golgi Apparatus

Organelle that modifies, sorts, and packages proteins; produces lysosomes and adds M6P tags.

Lysosome

Acidic organelle containing hydrolytic enzymes for digesting cellular waste and engulfed material.

Peroxisome

Organelle that performs β-oxidation of very-long-chain fatty acids and detoxifies hydrogen peroxide.

Cytoskeleton

Network of protein filaments (microtubules, microfilaments, intermediate filaments) providing structure, transport, and motility.

Microtubule

Tubulin-based cytoskeletal filament involved in intracellular transport, cilia/flagella motion, and mitosis.

Microfilament

Actin-based filament responsible for cell movement and muscle contraction.

Intermediate Filament

Cytoskeletal component providing tensile strength and structural support to cells.

Tay-Sachs Disease

Autosomal-recessive lysosomal storage disorder due to hexosaminidase

A deficiency of Hexosaminidase A enzyme, leading to GM2 ganglioside accumulation and neurodegeneration

Key Clinical features

-normal development, regression around 6 months

- neurodegeneration

-seizures, blindness, spasticity

-enlarged liver + spleen

-onion skin

Zellweger Syndrome

Autosomal-recessive peroxisomal biogenesis disorder caused by PEX mutations

Key Clinical Features

causing severe hypotonia (floppy baby), seizures, craniofacial anomalies (high forehead) and early death.

Kartagener Syndrome

Ciliopathy (cytoskeleton defect) from dynein arm defects of motile cilia

Affects:

Respiratory tract

Reproductive system

Embryonic development

Key Clinical Features

1. Chronic sinusitis

2. Recurrent otitis/ respiratory infections

3. Situs in versus (organs reversed)

causing immotile cilia, chronic respiratory infections, infertility, and situs inversus.(hearing loss)

Mitochondrial Myopathy

Group of disorders from mitochondrial DNA mutations leading to muscle weakness, lactic acidosis, and neurologic symptoms.

Leber’s Hereditary Optic Neuropathy (LHON)

Mitochondrial disorder involving complex I gene mutations causing acute, painless central vision loss in young males.

Progeria (Hutchinson-Gilford)

Nuclear envelope lamin A defect resulting in premature aging and cardiovascular disease.

Cystic Fibrosis

Disease where misfolded CFTR protein is retained in the RER, causing thick mucus and recurrent lung infections.

Alpha-1 Antitrypsin Deficiency

Misfolded protein accumulates in hepatocyte RER, causing liver disease and early-onset emphysema.

Total Body Water (TBW)

All water in the body (~60 % of adult male weight), divided into intracellular and extracellular compartments.

60=40 ICF + 20 ECF

Intracellular Fluid (ICF)

Fluid contained within cells; ~40 % of body weight or two-thirds of TBW.

Extracellular Fluid (ECF)

Fluid outside cells (plasma + interstitial fluid); ~20 % of body weight or one-third of TBW.

Osmolarity

Number of solute particles per liter of solution (mOsm/L).

Tonicity

Ability of an extracellular solution to cause water movement across a semipermeable membrane (isotonic, hypotonic, hypertonic).

Isotonic solution

No net water movement (e.g., 0.9%
NaCl

Hypotonic

Water enters cell → swelling/lysis

Hypertonic

Water exits cell → shrinkage
(crenation)

Starling Forces

Forces (hydrostatic and oncotic pressures) governing capillary filtration and reabsorption of fluid.

Capillary
hydrostatic
pressure (Pc)

Pressure
exerted by blood
pushing fluid out
of capillaries

Promotes
filtration (out of
capillary

Interstitial
hydrostatic
pressure (Pi)

Pressure in the
tissue pushing
fluid into
capillaries

Promotes
reabsorption
(into capillary

Capillary oncotic
pressure (πc

Osmotic pull by
plasma proteins
(mainly
albumin

Promotes
reabsorption
(into capillary)

Interstitial
oncotic pressure
(πi

Osmotic pull by
proteins in
interstitial fluid

Promotes
filtration (out of
capillary

Antidiuretic Hormone (ADH)

Posterior pituitary hormone that increases water reabsorption in kidneys via aquaporins.

Aldosterone

Adrenal cortex hormone that increases Na⁺ (and water) reabsorption and K⁺ excretion in the kidneys.

Atrial Natriuretic Peptide (ANP)

Cardiac atrial hormone that promotes Na⁺ and water excretion, lowering blood volume and pressure.

Renin–Angiotensin–Aldosterone System (RAAS)

Hormonal cascade activated by low blood pressure/volume to increase volume via vasoconstriction and aldosterone release.

Negative Feedback

Homeostatic mechanism that counteracts deviations from a set point, restoring stability (e.g., insulin lowering blood glucose).

Positive Feedback

Mechanism that amplifies a change until a climactic event stops the loop (e.g., oxytocin surge during labor).