medical

Acute Inflammation:  def.  lasts minutes to days and characterized by exudation of fluid and plasma proteins and emigration of leukocytes, predominantly neutrophils. 1.  Alterations in vascular caliber that lead to increased blood flow: vasodilation 2.  Microvascular structural changes that allow exudation of plasma protens and leukocytes: increased permeability mediated by histamine, bradykinin, leukotrienes, substance P, endothelial retraction exudate (s.g. > 1.012) vs. transudate (s.g. < 1.012) 3.  Emigration of leukocytes: margination, rolling, adhesion, diapedesis, migration neutrophils predominate (6-24 hours) and replaced by monocytes (24-48 hours) E-selectin (endothelium) - rolling, adhesion [induced by IL-1 and TNF] P-selectin (endothelium, platelets) - rolling [present in Weibel-Palade bodies] L-selectin (leukocytes) - homing ICAM (interacts with integrins LFA-1 on leukocytes) - adhesion, arrest, transmigration VCAM (interacts wit...

Frank-Starling Law of the Heart Two physiologists, Otto Frank and Ernest Starling, demonstrated that the strength of ventricular contraction varies directly with the end-diastolic volume (fig. 14.2). Even in experiments where the heart is removed from the body (and is thus not subject to neural or hormonal regulation) and where the still-beating heart is filled with blood flowing from a reservoir, an increase in EDV within the physiological range results in increased contraction strength and, therefore, in increased stroke volume. This rela- tionship between EDV, contraction strength, and stroke volume is thus a built-in, or intrinsic, property of heart muscle, and is known as the Frank-Starling law of the heart.

Regulation of Stroke Volume The stroke volume is regulated by three variables: the end-diastolic volume (EDV), which is the volume of blood in the ventricles at the end of diastole; the total peripheral resistance, which is the frictional resistance, or impedance to blood flow, in the arteries; and the contractility, or strength, of ventricular contraction. The end-diastolic volume is the amount of blood in the ven- tricles immediately before they begin to contract. This is a work- load imposed on the ventricles prior to contraction, and thus is sometimes called a preload. The stroke volume is directly proportional to the preload; an increase in EDV results in an increase in stroke volume. (This relationship is known as the Frank-Starling law of the heart, discussed shortly.) The stroke volume is also directly proportional to contractility; when the ventricles contract more forcefully,...

Effect of pH and Temperature on Oxygen Transport In addition to changes in P O 2 , the loading and unloading reac- tions are influenced by changes in the affinity (bond strength) of hemoglobin for oxygen. Such changes ensure that active skeletal muscles will receive more oxygen from the blood than they do at rest. This occurs as a result of the lowered pH and increased temperature in exercising muscles. The affinity is decreased when the pH is lowered and increased when the pH is raised; this is called the Bohr effect. When the affinity of hemoglobin for oxygen is reduced, there is slightly less loading of the blood with oxygen in the lungs but greater unloading of oxygen in the tissues. The net effect is that the tissues receive more oxygen when the blood pH is lowered (table 16.8). Since the pH can be decreased by carbon dioxide (through the formation of carbonic acid), the Bohr effect helps to provide more oxygen to the tissue...

Boyle’s Law Changes in intrapulmonary pressure occur as a result of changes in lung volume. This follows from Boyle’s law, which states that the pressure of a given quantity of gas is inversely proportional to its volume. An increase in lung volume during inspiration decreases intrapulmonary pressure to subatmospheric levels; air therefore goes in. A decrease in lung volume, conversely, raises the intrapul- monary pressure above that of the atmosphere, expelling air from the lungs. These changes in lung volume occur as a consequence of changes in thoracic volume,

SKELETAL MUSCLES Skeletal muscles are composed of individual muscle fibers that contract when stimulated by a somatic motor neu- ron. Each motor neuron branches to innervate a number of muscle fibers. Activation of varying numbers of motor neurons results in gradations in the strength of contraction of the whole muscle the agonist muscle; in flexion, for example, the flexor is the agonist muscle. Flexors and extensors that act on the same joint to produce opposite actions are antagonistic muscles

Sleep Although environmental factors affect sleep, there is evidence that sleep is genetically controlled. This is shown by sleep dis- orders that run in families and the heritability of sleep patterns. Histamine and several other neurotransmitters promote wake- fulness, while adenosine and GABA promote sleep. The neural control of sleep and arousal is discussed in conjunction with the reticular activating system in section 8.4. Two categories of sleep are recognized. Dreams—at least those that are vivid enough to recall upon waking—occur dur- ing rapid eye movement (REM) sleep. The name describes the characteristic eye movements that occur during this stage of sleep. The remainder of the time sleeping is spent in non-REM, or resting, sleep. These two stages of sleep can also be distin- guished by their EEG patterns. The EEG pattern during REM sleep consists of theta waves (5 to 8 cycles per second), although the EEG is often desynchronized as in...

Pathophysiology of heart failure In heart failure, the heart may not provide tissues with adequate blood for metabolic needs, and cardiac-related elevation of pulmonary or systemic venous pressures may result in organ congestion. This condition can result from abnormalities of systolic or diastolic function or, commonly, both. Although a primary abnormality can be a change in cardiomyocyte function, there are also changes in collagen turnover of the extracellular matrix. Cardiac structural defects (eg, congenital defects, valvular disorders), rhythm abnormalities (including persistently high heart rate), and high metabolic demands (eg, due to thyrotoxicosis) also can cause HF.

Many different types of medicines help treat heart failure. Some of the more common types are: ACE inhibitors : Widen your blood vessels to lower blood pressure so your heart doesn't have to work as hard, and help your kidneys get rid of extra water Beta-blockers : Slow your heart rate so your heart doesn't have to work as hard, and can help a stiff heart relax so it fills with blood better Diuretics (water pills) : Help your kidneys get rid of the extra water by making you urinate more If you have very bad heart failure that isn’t responding to medicines, doctors may suggest a heart transplant or a mechanical device that helps pump blood.

eeling like you can’t catch your breath, which worsens when you lie flat Feeling tired all over Swelling in your feet, ankles, and legs Symptoms usually develop slowly. At first you may feel out of breath only when you climb stairs and notice only a little leg swelling at the end of the day. Later, you may feel out of breath or tired when you do ordinary activities. When heart failure is severe, you may be out of breath even sitting in a chair and have a lot of leg swelling all the time. Heart failure can shorten your life, especially when it's severe. Treatment can help you live longer.

Any problem that makes your heart weak or stiff can cause heart failure. Common examples of such problems are: High blood pressure  (makes your heart work too hard) Coronary artery disease  (blocks the blood supply to your heart muscle) Heart valve problems  (leaky or blocked valves make it hard to pump blood) Other problems that can cause heart failure are an  irregular heart rhythm , low number of red blood cells ( anemia ),  thyroid gland  problems, and heart muscle infections. Most disorders cause heart failure only after many years. However, some disorders, such as a major  heart attack , can cause heart failure quickly. Often, a person’s heart failure has more than one cause.

Who can have heart failure Anyone can have heart failure, even young children (especially children born with a heart defect). However, it’s much more common in older people, because: Older people are more likely to have other heart problems that can cause heart failure Older people are more likely to have high blood pressure and diabetes , which can lead to heart failure The heart's walls stiffen with age

Your heart pumps blood to carry oxygen and nutrients to the rest of your body. Heart failure is when your heart doesn’t pump blood as well as it should. It doesn’t mean your heart has stopped (that's called cardiac arrest ). If you have heart failure, your heart pumps less blood That causes fluid to back up in your lungs and other body part Extra fluid in your lungs makes it hard to breathe Extra fluid in your legs makes them swell If your kidneys don’t get enough blood, they make less urine so the body has more fluid That extra fluid makes your heart work even harder Then, your heart failure can get even worse The extra fluid in your body is called “congestion.” That’s why heart failure is sometimes called “congestive heart failure.”

The new coronavirus that began as a handful of infections in central China has rapidly become a worldwide pandemic, shutting down entire cities, threatening the health of thousands and testing the strength of the global economy. More than 155,000 cases of the coronavirus have been confirmed worldwide across more than 100 countries and regions, and more than 5,800 people have died as of Saturday evening, according to  data from Johns Hopkins University . At the same time, more than 72,000 people worldwide have recovered from the virus. As the rate of  new cases in China continues to decline , more and more cases are being confirmed across the globe, with clusters in Italy and Iran. In the U.S., the death toll is creeping upward as new cases are cropping up   across dozens of states. Months into the outbreak, there are still more questions than answers. Here's what you need to know about COVID-19