Bio Exam 4: Chapter 45 (3)

Types of Blood Vessels

1. Arteries are tough, thick-walled vessels that take blood away from the heart under high pressure. Small arteries are called arterioles. 2. Capillaries are the smallest vessels. Their walls are just one cell thick, allowing gases and other molecules to exchange with tissues in networks called capillary beds. 3. Veins are vessels that return blood to the heart(s) under low pressure. -Small veins are called venules.

carbonic anhydrase

1. CO2 that is produced by cellular respiration enters the blood and RBCs, where it is quickly converted to bicarbonate ions and protons in a reaction catalyzed by the enzyme

Carbonic anhydrase catalyzes the formation of carbonic acid from carbon dioxide in water

1. Consequently, CO2 that diffuses into red blood cells is quickly converted to bicarbonate ions and protons. 2. Thus, most CO2 is transported in blood (specifically in plasma) in the form of the bicarbonate ion, HCO3.

Bohr shift

1. Hemoglobin is also sensitive to changes in pH and temperature. 2. Decreases in pH and increases in temperature alter hemoglobin's conformation such that it is more likely to release O2 at all values of Po2 3. The Bohr shift makes hemoglobin more likely to release oxygen during exercise or other conditions in which Pco2 is high, pH is low, and tissues are under oxygen stress

What Is a Closed Circulatory System?

1. In a closed circulatory system, blood flows in a continuous circuit through the body under pressure generated by a heart. Because blood is confined to vessels, a closed system can generate enough pressure to maintain a high flow rate. 2. Blood flow can also be directed in a precise way in a closed circulatory system.

circulatory system

1. In larger animals, however, the problem of providing a large surface area for diffusion is solved by 2. The function of a circulatory system is to carry blood or hemolymph into close contact with every cell in the body. 3. Circulatory systems can be open or closed.

What Happens in the Lungs?

1. In the alveoli, a partial-pressure gradient favors the diffusion of CO2 from plasma and RBCs to the atmosphere. 2. Hemoglobin releases protons, which combine with bicarbonate to form CO2, which then diffuses into the alveoli and is exhaled from the lungs. 3. Hemoglobin picks up O2 during inhalation, and the cycle begins again.

The structure of arteries, capillaries, and veins correlates closely with their function in a closed circulatory system:

1. The heart ejects blood into a large artery, usually called the aorta, which has elastic walls, allowing it to expand when blood enters it under high pressure from the heart. 2. Arterioles have muscle fibers called sphincters wrapped around their circumference. The sphincters allow the diameter of the vessel to be carefully regulated in response to signals from the nervous system.

Cooperative Binding

1. The most remarkable feature of the oxygen-hemoglobin equilibrium curve is that it is sigmoidal, or S-shaped. 2. The pattern occurs because the binding of each successive oxygen molecule to a subunit of the hemoglobin molecule causes a conformational change in the protein that makes the remaining subunits much more likely to bind oxygen 3. Cooperative binding makes hemoglobin exquisitely sensitive to changes in the Po2 of tissues

Carbonic anhydrase activity in red blood cells is important for two reasons:

1. The protons produced by the carbonic anhydrase reaction induce the Bohr shift, which makes hemoglobin more likely to release oxygen. 2. The Pco2 in blood drops when CO2 is converted to bicarbonate, maintaining a strong partial-pressure gradient favoring the entry of CO2 into red blood cells

Animals maximize the surface area available for diffusion of gases and other key solutes in a variety of ways:

1. Tiny animals have a small enough volume that diffusion over their body surface is adequate to keep them alive. 2. Jellyfish and corals have a large, highly folded gastrovascular cavity that offers a large surface area for molecular exchange. 3. The flattened bodies of flatworms and tapeworms give them a high surface area/volume ratio; molecular exchange thus occurs over the body surface. 4. Diffusion across the body wall also occurs in roundworms, where gas exchange is facilitated by muscular contractions in their body wall.

Hemolymph

1. is pumped into blood vessels that empty into an open, (lower pressure) fluid-filled space, and is returned to the heart when the heart relaxes, lowering its internal pressure. 2. Hemolymph transports wastes and nutrients and may also contain oxygen-carrying pigments, some cells, and clotting agents

open circulatory systems

a fluid connective tissue called hemolymph is actively pumped throughout the body by a muscular organ called the heart, but is not confined exclusively to vessels

buffer

minimizing changes in pH

valves

thin flaps of tissue that prevent any backflow of blood