Lec 16

What are 2 types of HT?

essential/primary secondary

what is a baroreceptor?

A baroreceptor is a receptor that monitors changes in blood pressure by monitoring the "stretch" in a vessel.

How can edema be caused by a lack of protein in the diet, liver disease, kidney disease, pregnancy?

A variety of things can cause edema. When someone does not eat enough proteins, the body can decrease its production of the plasma proteins, such as albumin, and then there is a decrease in the colloid osmotic pressure, that results in not as much fluid returned to the capillaries. Since the liver produces the plasma proteins, if there is liver disease your generally have a decrease in plasma proteins, again decreasing the colloid osmotic pressure in the capillaries. In kidney disease, the kidneys are our major regulators of the total blood volume (amount of water in the blood), when they are failing, the volume increases, this produces higher hydrostatic pressure, as this increases, the end of the capillary bed pressure can increase to the point where not a lot of fluid can return to the capillaries. In pregnancy, the growing fetus can start to pinch the veins, which backs up the blood and therefore increase the hydrostatic pressure at the end of the capillary bed, again preventing the return of fluid from the interstitial space.

What do lymph vessels and veins have in common?

Both vessels are bringing fluid and cells back to the heart.

What is congestive heart failure?

Congestive heart failure is any condition that results in the hearts INABILITY to produce sufficient CO to maintain blood flow required by the body.

What effect does a decrease in pressure have on the baroreceptors? On the sympathetic neurons to the heart? On the cardiac output?

Decrease in BP -> decrease in firing of the baroreceptors. This leads to an increase of firing of sympathetic neurons to the heart (and a decrease in firing of the parasympathetic neurons) and that will increase the cardiac output and therefore increase the blood pressure. In increase in BP will have the opposite affects.

What is edema?

Edema is the condition that occurs when not all of the fluid is returned to the heart, but instead builds up in the interstitial spaces.

What damage can chronic high blood pressure cause?

High blood pressure can damage small blood vessels, which can contribute to arteriosclerosis, hemmorage, heart attack, or stroke, and it can also put an excess workload on the heart that can lead to hypertrophy and congestive heart failure.

What creates hydrostatic pressure in vessels?

Hydrostatic pressure is created from the pressure of the contraction of the heart.

How can congestive heart failure result in pulmonary as well as peripheral edema?

In congestive heart failure, since the heart is not able to pump efficiently, blood back up in the venous side and as outlined above prevents fluid return to the capillaries. Not only can blood back up in the systemic or peripheral blood vessels, but in congestive heart failure, the blood can also back up in the pulmonary circulation, which, just like any other capillary bed in the body, will prevent the normal return of fluids to the capillaries in the pulmonary circuit and cause pulmonary edema.

What is hypotension?

Low BP

what are causes of circulatory shock?

It can be produced from decreased blood volume (as from internal bleeding), massive vasodialation that can occur in sepsis (an infection), severe allergic reactions, loss of sympathetic tone, or congestive heart failure.

how is interstitial fluid different from lymph?

Lymph has much less water than interstitial fluid since most of it has returned to the capillaries. We also find that lymphocytes tend to stay more often in the lymphatic system, hence the name, although the lymphocytes all migrate through the lymphatic system, blood stream and interstitial fluids.

How many cell membranes must an oxygen molecule cross to pass from plasma to tissue cells?

Oxygen may have to pass through 3 different membranes to get into tissue cells: The two sides of the endothelial cells that line the capillaries, and the membrane of the tissue cell.

How are preload and afterload involved in CHF?

Preload is a general term referring to the amount of the EDV. Afterload refers to the total peripheral resistance that the heart must pump against. Because the CO is dependent on the HR and SV, the less preload and/or the greater the afterload, the more likely you may produce congestive heart failure.

At what level is blood pressure considered to be hypertensive?

When BP >140/90mmHg, this is generally considered to be hypertensive. Currently, antihypertensive measures are indicated in some people as systolic pressure rises to 130mmHg.

What is circulatory shock?

Shock is a general term for inadequate perfusion of tissues with blood and therefore not enough oxygen going to the tissues.

What creates plasma colloid osmotic pressure in capillaries?

The colloid osmotic pressure is created by the large proteins which are "trapped" in the blood stream and do NOT go out into the interstitial space.

are hydrostatic pressure and plasma colloid osmotic pressure constant?

The osmotic pressure stays constant, however the hydrostatic pressure changes. It is because of the change in hydrostatic pressure that movement of water occurs in both directions. At the beginning of the capillary bed, hydrostatic pressure is the greatest, and will drive the water out of the capillaries. At the end of the capillary bed, the hydrostatic pressure has decreased to the point where the osmotic pressure becomes the greater influence of water movement and so water moves back into the capillaries.

are hydrostatic pressure and plasma colloid osmotic pressure equal?

The pressures are NOT equal, this is why water moves out of the capillaries at the beginning of the capillary bed and returns to the capillaries at the end of the capillary bed.

How is interstitial fluid different from plasma?

The interstitial fluid does NOT contain the large proteins found in the plasma - albumin, globulins and fibrinogen.

Where do lymph vessels originate?

The lymph vessels originate as "blind" vessels (meaning that they are not associated with any other vessel) in the capillary beds.

Why is the lymphatic system necessary?

The lymphatic system is necessary, because the oncotic pressure from the plasma proteins is NOT enough to draw all the fluid back into the capillaries, so excess fluid in the interstitial space is filtered into the lymphatic system. Our bodies then return the fluid in the lymphatic system back to the bloodstream via the thoracic duct or the right lymphatic duct, but before doing so, our immune system screens the lymphatic fluid for microbes or foreign substances.

What is the general mechanism for movement of fluid from the bloodstream to the interstitial fluid and back?

There are four potential different forces which are acting to move fluid from the bloodstream to the interstitial compartment and back; the hydrostatic pressure within the capillary, the hydrostatic pressure in the interstitial fluid, the oncotic pressure within the capillary and any oncotic pressure in the interstitial fluid (the last of which normally doesn't exist). Both the hydrostatic pressure in the interstitial fluid and the oncotic pressure within the capillary don't really change. Only the hydrostatic pressure within the capillary changes from the beginning of the capillary bed to the end of the bed. At the beginning of the capillary bed, there is more hydrostatic pressure within the capillaries and so there is net filtration of fluid out into the interstitial space. At the end of the capillary bed, the hydrostatic pressure has dropped, so that the oncotic pressure from the large plasma proteins helps to draw fluid back into the capillaries.

where are baroreceptors found?

There is one in the aortic arch, there is one in each of the carotid arteries, and there is one in the right atrium.

By what transport mechanism does oxygen travel?

Transport is all by passive diffusion

What happens to your upper body blood pressure when you go from a prone to a standing position?

When you go from a prone (or lying down position) to a standing position, you suddenly will have a drop in blood pressure as gravity is now pulling the blood into the foot area of your body.

where does edema occur?

capillary beds

How is the situation of laying down to suddenly standing corrected?

the baroreceptors immediately sense this drop and activate the sympathetic system, which will help to speed up the heart, and vasoconstrict vessels to help return blood back to the heart. When the blood pressure returns to normal, the sympathetic system will "back off" a little, just to the point to maintain proper blood pressure.