Of or relating to the vagus nerve. The vagus nerve (also called pneumo-gastric nerve or cranial nerve X) is the tenth of twelve paired cranial nerves, and is the only nerve that starts in the brainstem (within the medulla oblongata) and extends, through the jugular foramen, down below the head, to the neck, chest and abdomen. The medieval Latin word vagus means literally "Wandering" (the words vagrant, vagabond, and vague come from the same root). It is also called the pneumo-gastric nerve since it innervates both the lungs and the stomach.
Anatomy, a membranous fold or other structure that controls the flow of a fluid, as one that permits blood to flow in one direction only. A membranous structure in a hollow organ or passage, as in an artery or vein, that folds or closes to prevent the return flow of the body fluid passing through it.
Vascular is an adjective for the word vessel and refers to tube-like structures.
• In anatomy and physiology, "vascular" means "related to blood vessels", which are part of the circulatory system. An organ or tissue that is vascularized is heavily endowed with blood vessels and thus richly supplied with blood.
Vascular resistance is a term used to define the resistance to flow that must be overcome to push blood through the circulatory system. The resistance offered by the peripheral circulation is known as the systemic vascular resistance (SVR), while the resistance offered by the vasculature of the lungs is known as the pulmonary vascular resistance (PVR). The systemic vascular resistance may also be referred to as the total peripheral resistance.
A vasoconstrictor, also vasopressor or simply pressor, is any substance that acts to cause vasoconstriction (narrowing of the lumen of blood vessels) and usually results in an increase of the blood pressure. The opposite process, vasodilation, is the opening of blood vessels. Vasoconstrictors are used in medicine to treat hypotension.
Vasodilation is a process by which blood vessels in the body become wider following the relaxation of the smooth muscle in the vessel wall. This will reduce blood pressure - since there is more room for the blood.
Arginine vasopressin (AVP), also known as argipressin or antidiuretic hormone (ADH), is a human hormone that is released when the body is low on water; it causes the kidneys to conserve water, but not salt, by concentrating the urine and reducing urine volume. It also raises blood pressure by inducing moderate vasoconstriction. It has various effects in the brain.
Vasospasm refers to a condition in which blood vessels spasm, leading to vasoconstriction. This can lead to tissue ischemia and death (necrosis). Cerebral vasospasm may arise in the context of subarachnoid haemorrhage. Symptomatic vasospasm or delayed cerebral ischemia is a major contributor to post-operative stroke and death after aneurysmal subarachnoid haemorrhage. Vasospasm typically appears 4 to 10 days after subarachnoid haemorrhage.
Vaughan Williams classes.
The Vaughan Williams classification is one of the most widely used classification schemes for anti-arrhythmic agents. This scheme classifies a drug based on the primary mechanism of its anti-arrhythmic effect. However, its dependence on primary mechanism is one of the limitations of the VW classification, since many anti-arrhythmic agents have multiple action mechanisms. Amiodarone, for example, has effects consistent with all of the first four classes. Another limitation is the lack of consideration within the VW classification system for the effects of drug metabolites. Procainamide—a class Ia anti-arrhythmic agent whose metabolite N-acetyl procainamide (NAPA)-( metabolite of procainamide ) has a class III action—is one such example. A historical limitation was that drugs such as digoxin and adenosine – important anti-arrhythmic agents – had no place at all in the VW classification system. This has since been rectified by the inclusion of class V.
There are five main classes in the Vaughan Williams classification of antiarrhythmic agents:
• Class I agents interfere with the sodium (Na+) channel.
• Class II agents are anti-sympathetic nervous system agents. All agents in this class are beta blockers.
• Class III agents affect potassium (K+) efflux.
• Class IV agents affect the AV node.
• Class V agents work by other or unknown mechanisms.
In the circulatory system, a vein is a blood vessel that carries blood toward the heart. The majority of veins in the body carry low-oxygen blood from the tissues back to the heart; the exceptions being the pulmonary and umbilical veins which both carry oxygenated blood.
In respiratory physiology, ventilation (or ventilation rate) is the rate at which gas enters or leaves the lung. It is categorised under the following definitions:
Measurement Equation Description
= tidal volume * respiratory rate
the total volume of gas entering the lungs per minute.
Alveolar ventilation = (tidal volume - dead space) * respiratory rate
the volume of gas per unit time that reaches the alveoli, the respiratory portions of the lungs where gas exchange occurs.
Dead space ventilation = dead space * respiratory rate
is the volume of gas per unit time that does not reach these respiratory portions, but instead remains in the airways (trachea, bronchi, etc.).
Mechanical ventilation is a method to mechanically assist or replace
spontaneous breathing when patients cannot do so on their own, and must be done so after invasive intubation with an endotracheal or tracheostomy tube through which air is directly delivered .In many cases, mechanical ventilation is used in acute settings such as in the ITU for a short period of time during a serious illness. For some patients who have certain chronic illnesses that require long-term ventilation assistance, they are also able to do so at home or other nursing/rehabilitation institution with the help of respiratory therapists and physicians. The main form of mechanical ventilation currently is positive pressure ventilation, which works by increasing the pressure in the patient's airway and thus forcing additional air into the lungs. This is in contrast to the more historically common negative pressure ventilators (for example, the "iron lung") that create a negative pressure environment around the patient's chest, thus sucking air into the lungs. Although often a life-saving technique, mechanical ventilation carries many potential complications including pneumothorax, airway injury, alveolar damage, and ventilator-associated pneumonia, among others. Accordingly it is generally weaned off or to minimal settings as soon as possible.
Ventricle / ventricular.
A small pouch or cavity; applied especially to the lower chambers of the heart, and to the four cavities of the brain. Ventricular, pertaining to a ventricle, e.g. the outer folds of mucous membrane forming the false vocal cords.
Ventricular assist device (VAD):
A Ventricular assist device, or VAD, is mechanical device that is used to partially or completely replace the function of a failing heart. Some VADs are intended for short term use, typically for patients recovering from heart attacks or heart surgery, while others are intended for long term use (months to years and in some cases for life), typically for patients suffering from congestive heart failure. VADs need to be clearly distinguished from artificial hearts, which are designed to completely take over cardiac function and generally require the removal of the patient's heart. VADs are designed to assist either the right (RVAD) or left (LVAD) ventricle, or both at once(BVAD). The choice of device depends on the underlying heart disease and the pulmonary arterial resistance which determines the load on the right ventricle. LVADs are most commonly used but when pulmonary arterial resistance is high, right ventricular assist becomes necessary. Long term VADs are normally used to keep patients alive with a good quality of life while they wait for a heart transplant (bridge to transplant). However LVADs are sometimes used as destination therapy sometimes as a bridge to recovery.
Ventricular tachycardia can be classified based on its morphology: Monomorphic ventricular tachycardia means that the appearance of all the beats match each other in each lead of a surface electrocardiogram (ECG).
Polymorphic ventricular tachycardia, on the other hand, has beat-to-beat variations in morphology. This most commonly appears as a cyclical progressive change in cardiac axis referred to by its French eponym Torsades de Pointes (literally twisting of the points).
Another way to classify ventricular tachycardias is the duration of the episodes: Technically, three or more beats in a row on an ECG that originate from the ventricle at a rate of more than 100 beats per minute constitute a ventricular tachycardia. If the fast rhythm self-terminates within 30 seconds, it is considered a non-sustained ventricular tachycardia. If the rhythm lasts more than 30 seconds it is known as a sustained ventricular tachycardia(even if it terminates on its own after 30 seconds).
Ventricular tachycardia (cont).
A third way to classify ventricular tachycardia is on the basis of its symptoms: Pulseless VT is associated with no effective cardiac output, hence, no effective pulse, and is a cause of cardiac arrest. In this circumstance it is best treated the same way as ventricular fibrillation (VF) and is recognized as one of the shockable rhythms on the cardiac arrest protocol. Some VT is associated with reasonable cardiac output and may even be asymptomatic. The heart usually tolerates this rhythm poorly in the medium to long term, and patients may certainly deteriorate to pulseless VT or to VF.
Ventricular tachycardia ( VT ) is a fast heart rate that starts in the lower chambers of the heart (ventricles). VT may result from serious heart desease, it usually requires prompt treatment. If treatment is required, it includes medicines and treating the cause, if possible. The type and length of treatment depends on what’s causing the problem. In some cases radiofrequency ablation or surgery may be needed to control the tachycardias .During VT the heart becomes unable to pump adequate blood around the body.
• usually, there are no P waves visible
• when P waves are detectable they are not related to QRS complexes (atrioventricular dissociation is present)
• the QRS complexes are wide (> 0.12 s) and they appear in a regular rhythm
• the rate of QRS complexes is between 100 and 260 beats per minute (usually between 180 and 250)
Ventricular fibrillation (V-fib or VF) is a condition in which there is uncoordinated contraction of the cardiac muscle of the ventricles in the heart. As a result the heart fails to adequately pump blood and hypoxia will occur followed by unconsciousness within 20 - 30 seconds. Ventricular fibrillation is a medical emergency. If the arrhythmia continues for more than a few seconds, blood circulation will cease — as evidenced by lack of pulse, blood pressure, and respiration — and eventually death will occur. Ventricular fibrillation is a cause of cardiac arrest and sudden cardiac death. The ventricular muscle twitches randomly, rather than contracting in unison, and so the ventricles fail to pump blood into the arteries and into systemic circulation.
• there are neither P waves, nor QRS complexes visible
• there is an irregular electric activity with a rate usually between 150 and 500 waves per minute
A venule is a small blood vessel that allows deoxygenated blood to return from the capillary beds to the larger blood vessels called veins.
Anatomy, a tube or duct, as an artery or vein, containing or conveying blood or some other body fluid.
Ventricular Septal Defect
A ventricular septal defect (VSD) is a defect in the ventricular septum, the wall dividing the left and right ventricles of the heart.
The ventricular septum consists of an inferior muscular and superior membranous portion and is extensively innervated with conducting cardiomyocytes – (cardio=heart, myo=muscle and cyte=cell). The membranous portion, which is close to the atrioventricular node, is most commonly affected. Congenital VSDs are collectively the most common congenital heart defects.
The vocal folds, also known popularly as vocal cords, are composed of twin infoldings of mucous membrane stretched horizontally across the larynx. They vibrate, modulating the flow of air being expelled from the lungs during phonation - (is the "use of the laryngeal system to generate an audible source of acoustic energy, i.e., sound).
Open during inhalation, closed when holding one's breath, and vibrating for speech or singing; the folds are controlled via the vagus nerve. They are white because of scant blood circulation.
Wolff (Wolfe)-Parkinson-White (WPW) is a very rare cause of sudden death. It results from an additional electrical connection between the atria (upper chambers of the heart) and the ventricles (lower chambers of the heart). This extra or accessory electrical pathway is present in approximately 1.5 people per 1,000 people. It runs in families in less than 1% of cases. In the majority it is completely
Wolff-Parkinson-White Syndrome (cont).
silent and only detected on a routine ECG. In a small proportion of patients the extra electrical pathway allows conduction of the electrical pathway generating an electrical circuit which produces a very rapid heart rate. Most patients tolerate this well but some experience very troublesome palpitations, light-headedness and blackouts. A very small minority of patients may die suddenly from ventricular fibrillation (<0.1% of patients).Palpitations are the main symptoms. When the patient is experiencing palpitations the heart rate is usually in excess of 150 beats per minute. When the patient has no symptoms there is nothing to find on examination. WPW is diagnosed by performing an ECG. The ECG usually shows two abnormalities when the patient is free of symptoms – a short PR interval and a delta wave. It is often an incidental finding during a routine ECG check as part of a medical insurance or detected by a cardiologist when a patient is referred with palpitations. The ideal treatment in patients with symptoms is to destroy the extra electrical pathway, a procedure termed radio frequency catheter ablation.
White Blood Cells (see leucocytes).
White Blood Cell Count (WBC).
Leukocyte count = White blood cell count. A WBC count is a blood test to measure the number of white blood cells (WBCs). White blood cells help fight infections. They are also called leukocytes. There are five major types of white blood cells: Basophils ,Eosinophils Lymphocytes,Monocytes and Neutrophils.
• Basophils are the least common of the granulocytes, representing about 0.01% to 0.3% of circulating leukocytes (white blood cells). They contain large cytoplasmic granules which obscure the cell nucleus under the microscope.
• Eosinophil granulocytes, commonly referred to as eosinophils (or less commonly as acidophils), are white blood cells of the immune system that are responsible for combating infection by parasites in vertebrates. They also control mechanisms associated with allergy and asthma. They are granulocytes that develop in the bone marrow before migrating into blood.
• Neutrophil granulocytes, generally referred to as neutrophils, are the most abundant type of white blood cells and form an integral part of the immune system. Their name arrives from staining characteristics on haematoxylin and eosin (H&E) histological preparations.
• A lymphocyte is a type of white blood cell in the vertebrate immune system. By their appearance under the light microscope, there are two broad categories of lymphocytes, namely the large granular lymphocytes and the small lymphocytes.
• A monocyte is a leukocyte, part of the human body's immune system that protects against blood-borne pathogens and moves quickly (aprox. 8-12 hours) to sites of infection in the tissues. Monocytes are usually identified in stained smears by their large bilobate nucleus.
• Granulocytes: leukocytes characterised by the presence of differently staining granules in their cytoplasm when viewed under light microscopy. These granules are membrane-bound enzymes which primarily act in the digestion of endocytosed particles. There are three types of granulocytes: neutrophils, basophils, and eosinophils, which are named according to their staining properties.
The test is performed to find out how many white blood cells you have. Your body produces more white blood cells when you have an infection or allergic reaction -- even when you are under general stress. Normal Values =4,500-10,000 white blood cells/mcL (cells per micro litre)
A low number of WBCs is called leukopenia. It may be due to:
White Blood Cell Count (WBC) (cont).
• Bone marrow failure (for example, due to infection, tumor, or abnormal scarring)
• Collagen-vascular diseases (such as lupus erythematosus)
• Disease of the liver or spleen
A high number of WBCs is called leukocytosis. It may be due to:
• Infectious diseases
• Inflammatory disease (such as rheumatoid arthritis or allergy)
• Severe emotional or physical stress
• Tissue damage (for example, burns)
People who have had their spleen removed will always have a slightly higher number of WBCs.
Zymogen - any of a group of compounds that are inactive precursors of enzymes and require some change (such as the hydrolysis of a fragment that masks an active enzyme) to become active.