Physiology - World of Revision Practice Flashcards

A comprehensive set of vocabulary flashcards covering key physiological concepts, terms, and mechanisms in General, Cellular, Muscle, Neuro, Respiratory, Cardiovascular, GIT, Renal, Endocrine, and Reproductive Physiology.

Homeostasis

A concept of constancy of the internal environment first termed by Walter Cannon.

Milieu interior

The internal environment of the body, a term coined by Claude Bernard.

Negative feedback

A control system mechanism where an increase in a factor ($\uparrow f/b$) leads to a decrease ($\downarrow$) in that factor to maintain stability, such as insulin regulation of glucose.

Positive feedback

A control system mechanism that causes amplification or a 'vicious cycle' ($\uparrow f/b \rightarrow \text{augmentation}$), exemplified by blood clotting, the LH surge, and parturition.

Feed forward control

A control mechanism that initiates anticipatory changes before a variable actually shifts, such as body temperature regulation.

Phosphatidylcholine

Also known as lecithin, it is the major surfactant in the lungs; an $L/S$ ratio of $\ge 2$ indicates fetal lung maturity.

Phosphatidylserine

A membrane lipid normally on the inner surface; if exposed extracellularly, it serves as an 'Eat me signal' for apoptosis.

Gangliosides

Lipids found in the GIT; Fragment B of the GM1 ganglioside specifically serves as the receptor for the cholera toxin.

CFTR

The cystic fibrosis transmembrane conductance regulator, a transmembrane protein (chloride channel) whose mutation causes Cystic Fibrosis.

Chaperones

Proteins located in the Rough Endoplasmic Reticulum (RER) that assist in proper protein folding.

Lysosomes

Organelles known as 'suicidal bags' or 'residual bodies' that perform acid-mediated destruction and autophagy.

Peroxisomes

Also known as microbodies, these organelles are responsible for the oxidation of Very Long Chain Fatty Acids (VLCFA) and the synthesis of plasmalogens for the myelin sheath.

Kinesin

A microtubule motor protein responsible for anterograde axonal transport.

Dynein

A microtubule motor protein responsible for retrograde axonal transport (e.g., transport of the Rabies virus) and ciliary motility.

Glial Fibrillary Acidic Protein (GFAP)

An intermediate filament type used as a cellular/tumor marker for astrocytes and astrocytomas.

Zonula occludens

Also known as tight junctions, these apicolateral junctions regulate paracellular transport and are found in the Blood-Brain Barrier (BBB), kidneys, and GIT.

Gap junctions

Cell-to-cell junctions made of connexons (formed by $6$ connexins) that allow the heart to act as a functional syncytium.

Fick’s Law

A law stating that simple diffusion is directly proportional to the concentration gradient and membrane surface area, and inversely proportional to membrane thickness.

Ouabain

A substance that decreases the activity of the $Na^+-K^+$ ATPase pump.

Resting Membrane Potential (RMP)

The stable electrical potential of a cell at rest, typically $-70,mV$ in neurons and $-90,mV$ in skeletal muscle.

Absolute Refractory Period (ARP)

The time from the threshold to the initial $1/3$rd of repolarization during which the cell cannot respond to a second stimulus because $Na^+$ channels are inactivated.

Wallerian degeneration

Distal nerve degeneration involving axonal and myelin breakdown occurring within $24$ hours of injury.

Sarcomere

The functional unit of skeletal muscle, bounded by Z lines.

SERCA pump

The sarcoplasmic reticulum calcium ATPase responsible for calcium uptake into the SR to initiate muscle relaxation.

Renshaw cell inhibition

A form of feedback inhibition where an $\alpha$ motor neuron stimulates a Renshaw cell to release glycine, inhibiting the same motor neuron.

Epicritic pain

First or fast pain characterized as sharp and pricking, carried by myelinated Adelta fibres using glutamate.

Protopathic pain

Second or slow pain characterized as dull and burning, carried by unmyelinated $C$ fibres using Substance P.

Stereognosis

The ability to identify objects by touch with eyes closed, a sensation carried by the dorsal column medial lemniscal pathway.

Rods

Retinal cells responsible for dim vision and peripheral vision; they hyperpolarize in response to light.

Organ of Corti

The receptor organ for hearing located in the scala media of the cochlea, containing hair cells.

Pill rolling tremor

A resting tremor caused by the degeneration of the Substantia Nigra pars compacta (decreased dopamine), characteristic of Parkinson’s disease.

Broca’s area

The motor area for speech located in the inferior frontal gyrus (Brodmann area $44$); lesions result in non-fluent aphasia.

Wernicke’s area

The sensory area for speech comprehension located in the superior temporal gyrus (Brodmann area $22$); lesions result in fluent aphasia.

Type 2 pneumocyte

A round alveolar cell that acts as a stem cell and produces surfactant.

Compliance

The expansibility of the lungs or chest wall, calculated as the change in volume divided by the change in pressure (C = \frac{Delta V}{Delta P}).

Bohr’s equation

The formula used to measure physiological or total dead space in the lungs.

Haldane effect

The principle that the deoxygenation of hemoglobin increases its ability to carry carbon dioxide ($CO_2$).

Ondine’s curse

A defect in spontaneous or automatic breathing caused by failure of the Pre-Bötzinger complex.

Kussmaul’s breathing

Rapid, deep acidotic breathing typically seen in patients with Diabetic Ketoacidosis (DKA).

AV node

The 'gatekeeper' of the heart, characterized by a physiological delay and the slowest conduction velocity ($0.04,m/s$).

Frank-Starling Law

The law stating that within physiological limits, the force of ventricular contraction is directly proportional to the end-diastolic volume (EDV).

Erythropoietin

A glycoprotein produced mainly by the kidneys (85, \text{%}) that inhibits RBC apoptosis in response to hypoxia.

Bombay blood group

A rare blood grouping that lacks A, B, and H antigens and contains Anti-A, Anti-B, and Anti-H antibodies.

Baroreflex

The first line of short-term blood pressure control, located in the carotid sinus and aortic arch.

Bainbridge reflex

A tachycardic reflex triggered by right atrial stretching due to fluid overload, common in congestive cardiac failure.

Meissner’s plexus

Also known as the submucosal plexus, it is located in the submucosa and controls GIT secretions.

Parietal cells

Gastric cells responsible for secreting hydrochloric acid ($HCl$) and intrinsic factor for Vitamin $B_{12}$ absorption.

Cholecystokinin (CCK)

A GI hormone secreted by I cells that acts as a cholagogue to contract the gallbladder and increases pancreatic digestive enzymes.

Ghrelin

An orexigenic hormone produced in the oxyntic region of the stomach that peaks during fasting and stimulates appetite.

Migratory Motor Complex (MMC)

A motility pattern regulated by motilin that clears the GIT between meals, occurring every $90$ minutes during fasting.

Inulin

The gold standard marker used to estimate the Glomerular Filtration Rate (GFR).

Liddle syndrome

A condition caused by overactivity of ENaC (Epithelial Na+ channels) leading to hypertension due to excessive sodium and water retention.

Anion Gap

The difference between measured cations and measured anions ($AG = Na^+ - [HCO_3^- + Cl^-]$), with a normal range of $8-16,mEq/L$.

Somatotrophs

Acidophilic cells in the anterior pituitary (50,\text{%}) that secrete Growth Hormone.

Wolff-Chaikoff effect

The inhibition of thyroid hormone organification caused by an excess of iodide.

Sertoli cells

Commonly known as 'nurse cells' of the testis, they form the blood-testis barrier and produce androgen-binding protein (ABP).

hCG

Human chorionic gonadotropin, a 'super LH' secreted by the syncytiotrophoblast that maintains the corpus luteum in early pregnancy.

MET

Metabolic equivalent, where $1,MET$ equals the resting oxygen consumption of approximately $250,mL/min$.

Malignant hyperthermia

A severe hyperthermic reaction to agents like succinylcholine due to a ryanodine receptor (RyR) mutation, treated with dantrolene sodium.