The oxygen hemoglobin dissociation curve is sigmoidal in shape because the binding of 1st oxygen molecule is difficult, however once bound, they facilitate the binding of subsequent molecules until the saturation is reached (plateau). This is called the allosteric interaction (cooperativity). Lets come to the mnemonics now. The curve can…
Tag: Physiology
PGMEE, MRCS, USMLE, MBBS, MD/MS 
Nerve fibers – Classification
Nerve fibers can be classified as A, B and C and A type fibers can be further classified into alpha, beta, gamma and delta. The size and myelination (thus conduction) progressively decreases in the descending order. A alpha: Efferent (Somatic motor) – To extrafusal fibers (muscle spindle) Afferent (Proprioception): Ia…
PGMEE, MRCS, USMLE, MBBS, MD/MS 
Physiology of Pulmonary Surfactant
Origin Type II alveolar cells/pneumocytes (small but numerous) and Lamellar bodies (appear in Type II pneumocytes at around the 20th week of gestation) Type I alveolar cells (large and covers 95% alveoli) are squamous cells and involved in gas exchange process. Recycling 90% is reprocessed (through endocytosis); average time for…
Clinical Skills and Approaches 
Bulbocavernosus Reflex (BCR)
Synonyms: Bulbospongiosus reflex (BSR), Osinski reflex Reflex arc: a. Stimulus: Briskly squeezing glans penis or clitoris or Tugging Foley’s catheter (pulling the balloon of foley’s catheter against the bladder neck) b. Afferent: Sensory fibers of pudendal nerve c. Reflex center: S2-S4 spinal segments (Polysynaptic) d. Efferent: Motor fibers of pudendal…
PGMEE, MRCS, USMLE, MBBS, MD/MS 
Micturition reflex
Micturition (Urination) is the ejection of urine from the urinary bladder through the urethra to the outside of the body. It is a type of reflex with voluntary control. The micturition cycle occurs in 2 phases: Urinary Storage Mnemonic: Storage = Sympathetic 1. Stimulus: Urine filling until tension in the…
PGMEE, MRCS, USMLE, MBBS, MD/MS 
Visual cycle – Simplified
11-cis-retinal combines with opsin protein to form rhodopsin. Light stimulates conversion of rhodopsin bound 11-cis-retinal to all-trans-retinol (all-trans-retinol is transported from photoreceptor cells to retinal pigment epithelium), which subsequently dissociates from opsin (bleaching), leading to membrane depolarization and initiation of action potential in photoreceptors in the neural retina. Once in…
PGMEE, MRCS, USMLE, MBBS, MD/MS 
Hematopoietic growth factors list with mnemonics
a. SCF (Steel factor): Multipontent stem cells b. IL-3: Myeloid stem cells (“3” turned down looks like “m“) c. IL-7: Lymphoid stem cell (“L” turned up looks like “7“) d. GM-CSF (Granulocyte macrophage Colony stimulating factor): Myeloid lineage (Erythrocytes, Thrombocytes, Granulocytes and Monocytes) Pharmaceutical: Sargramostim e. G-CSF: Granulocytes (Neutrophil, Eosinophil,…
PGMEE, MRCS, USMLE, MBBS, MD/MS 
Cell-Cell or Interceullular Junctions
Junction Location Composition Function Remarks Tight junction (Zonula occludens) Epithelial cell-Epithelial cell Claudin and Occludin (attaches to cytoskeleton – actin filament) Prevents paracellular movement of solutes and diffusion Adherens junction (Zonula adherens) Epithelial cell-Epithelial cell E-cadherin (attaches to cytoskeleton – actin filament) Belt desmosome (Anchoring) Cadherins are Ca2+ depndend adhesion…