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Vasopressin
Friday, September 23 (2022); Cardiovascular system
Vasopressin is an endogenously available vasoconstrictor with antidiuretic effects. "Vasopressor effects are exerted by V1 receptors, which are Gq-protein coupled receptors. Similarly to alpha-1 receptors, they increase intracellular calcium by means of increasing cAMP concentrations. V2 receptors are Gs-coupled receptors and produce the insertion of aquaporins into the apical membrane of principle cells of the collecting tubule, promoting the retention of watr.
Unlike catecholamine receptors, vasopressin receptors do not lose their affinity for vasopressin with changing pH."Solutions of dextrose: 5%, 10% and 50% concentrations
Thursday, September 22 (2022);
5% Dextrose is essentially just free water. No anions, no cations. No added buffer, no antimicrobial agent, no artificial colours or preservatives. For flavour, 278mmol of dextrose is added. If you were trying to use this as a source of nutrient, consuming the whole litre would yield 835 kJ, or 198 calories.
Vasopressin and its analogues in the CICM Second Part Exam
Wednesday, September 21 (2022); Pharmacology and Toxicology
Question 22 from the second paper of 2009 asked the candidates to talk about the role of vasopressin and its analogues in the critically ill patient. The question did not ask to critically evaluate anything; the objective was to merely outline. However, vasopressin probably merits a more detailed exploration. An extensive homage to vasopressin is available elsewhere; this chapter should only offer a brief revision of vasopressin and vasopressin-like substances.
Pharmacology of oral hypoglycaemic drugs
Sunday, September 18 (2022); Endocrine System
Numerous chemically diverse classes of oral hypoglycemic agents with various mechanisms of action exist, including biguanides, sulfonylureas, α-glucosidase inhibitors, meglitinides, thiazolidinediones, DPP-4 inhibitors, and SGLT-2 blockers. Unsurprisingly, for the majority of these (with some exceptions), hypoglycaemia is the most clinically important adverse effect.
Ventricular pressure-volume loops
Friday, September 16 (2022); Cardiovascular system
A PV loop plots the changes in ventricular pressure associated with the changes in volume which occur during the cardiac cycle. Multiple pieces of information can be extracted from such a loop, including volumes (eg. stroke volume), pressures (eg. end-systolic pressure), and area (which represents myocardial work). The PV loop can also be used to represent the relationships of contractility preload and afterload to cardiac function, and to model the effects of changing these variables.
Pharmacology of insulin preparations and glucagon
Tuesday, September 6 (2022); Endocrine System
Regular human insulin (eg. Actrapid) is an exact duplicate analog of the human peptide hormone, consisting of 51 amino acids. Other insulin variants modify the normal molecule to adjust the self-association behaviour of the drug, leading to longer or shorter absorption from the subcutaneous depot.
Adrenaline
Friday, September 2 (2022); Cardiovascular system
Adrenaline is an endogenous catecholamine, a sympathomimetic drug with little receptor selectivity. In its role as a haemodynamic support infusion, adrenaline acts as an inodilator, increasing cardiac output and increasing blood pressure while decreasing the afterload (mainly by its effect on the arterioles of the skeletal muscle). It also has several unpleasant side effects (hyperglycaemia, hypokalemia, lactate elevation) which decrease its popularity somewhat.
Essential features of the microcirculation
Thursday, September 1 (2022); Cardiovascular system
The microcirculation is the terminal vascular network of vessels smaller than 100 μm in diameter, where the exchange of substances between the blood and the tissues occurs. It consists of arterioles, capillaries and venules. Its main characteristics are its vast surface area and the low velocity of flow, which allows enough transit time for gas exchange and solute diffusion.
Control of plasma calcium
Wednesday, August 31 (2022); Endocrine System
Calcium homeostasis is regulated by three main hormones: parathyroid hormone (PTH), calcitriol, and calcitonin. PTH and calcitriol work to increase plasma calcium by increasing its absorption from the intestine and bone, and by resisting its loss in the renal tubule. Calcitonin, on the other hand, defends against hypercalcemia by inhibiting bone resorption and encouraging renal elimination.
Physiology of adrenal hormones
Tuesday, August 30 (2022); Endocrine System
Adrenal hormones include cortisol, aldosterone, androgens, and catecholamines. Each hormone is secreted from structurally and functionally distinct zones of the adrenal gland. The synthesis of steroid hormones occurs on demand in the adrenal cortex, whereas catecholamines are constantly being synthesised and stored in chromaffin granules inside cells of the adrenal medulla. The stimuli for their release can be broadly summarised as "stress".
Distribution and regulation of calcium in the body fluids
Tuesday, August 30 (2022); Body fluids and electrolytes
Calcium is an almost exclusively extracellular cation. Its concentration in the extracellular fluid is tightly regulated by the actions of PTH, calcitriol and calcitonin. PTH and calcitriol increase its absorption from the gut, reabsorption from the nephron, and increase the retrieval of bone calcium stores. Calcitonin, in contrast, acts to decrease plasma calcium levels
Physiology of pituitary and hypothalamic hormones
Monday, August 29 (2022); Endocrine System
The hypothalamus and pituitary are small CNS endocrine organs that are involved in the regulation of numerous processes, among them the autonomic nervous system, temperature, body water volume, reproductive function, emotion, metabolic rate, satiety, and stress responses.
Effects of catecholamine receptor activation
Sunday, August 28 (2022); Autonomic nervous system
This chapter offers a summary of the effects of catecholamine receptor activation
Behaviour of catecholamines at the synapse
Sunday, August 28 (2022); Autonomic nervous system
This is something of a summary of how catecholamines behave around adrenergic receptors. It describes catecholamine storage in vesicles, their exocytosis, presynaptic neurotransmission, and reuptake by NET ad DAT transporter proteins.