Neurophysiology
The impulse travels along the nerve membrane as an action potential. This is entirely mediated by the receptors within the membrane. Indeed, removal of the axoplasm from the nerve fiber…
ANESTHESIA
Circulatory Physiology
Endothelial Function and Regulation of Vascular Tone Endothelial synthesis and release of vasoactive mediators are important elements in the regulation of vascular tone. Substances are released by the endothelium in…
Intravenous Sedatives and Hypnotics
The fact that total body clearance of propofol exceeds hepatic blood flow is consistent with extrahepatic clearance (pulmonary uptake and first-pass elimination, renal excretion) of propofol.14,16 Pulmonary uptake of propofol…
Opioid Agonists and Antagonists
Chemical Structure of Opium Alkaloids The active components of opium can be divided into two distinct chemical classes: phenanthrenes and benzylisoquinolines. The principal phenanthrene alkaloids present in opium are morphine,…
Local Anesthetics
Local anesthetics are poorly soluble in water and therefore are marketed most often as water-soluble hydrochloride salts. These hydrochloride salt solutions are acidic (pH 6), contributing to the stability of…
Metabolism
For adults, total energy expenditure averages 39 kcal/kg in males and 34 kcal/kg in females. Approximately 20 kcal/kg is expended as basal metabolism necessary to maintain integrity of the cell…
Sympatholytics
Clinical Uses The principal use of phentolamine is the treatment of acute hypertensive emergencies, as may accompany intraoperative manipulation of a pheochromocytoma or autonomic nervous system hyperreflexia. Administration of phentolamine,…
Normal Endocrine Function
The pituitary gland lies in the sella turcica at the base of the brain and is connected to the hypothalamus by the pituitary stalk. Physiologically, the gland is outside the…
Gastrointestinal Physiology
Anatomy The liver is divided into four lobes consisting of 50,000 to 100,000 individual hepatic lobules (Fig. 32-1). Blood flows past hepatocytes via sinusoids from branches of the portal vein…
Gastrointestinal Motility Drugs
Pharmacokinetics H1-receptor antagonists are well absorbed after oral administration, often reaching peak plasma concentrations within 2 hours (see Table 35-1).19,20 Many are highly protein bound, with ranges from 78% to…
