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exchange ultimately occurs at the _______ level; in ___________ organisms exchange occurs directly with the ________ _________
cellular; unicellular; external environment
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two solutions to the slowness of difussion:
1) a body size/shape that keeps cells in direct contact w/ environment (sponges, cnidarians, flatworms) or 2) circulatory system that moves fluid between cell's immediate surroundings (found in all other animals)
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open circulatory system
circulatory fluid (hemolymph) also serves as the interstitial fluid and bathes the organs directly; arthropods and mollusks; lower hydrostatic pressure = less costly
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closed circulatory system
blood is confined to vessels and is distinct from interstitial fluid; annelids, cephalopods, and vertebrates; benefit = high blood pressure (effective delivery of O2 & nutrients
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arteries
carry blood from the heart TOWARD the capillaries
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veins
return blood to the heart FROM capillaries; except the portal vein, which carries blood between pairs of capillary beds
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atria
muscular chamber of the heart that RECEIVES blood
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ventricle
muscular chamber of the heart that pumps out blood
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single circulation
a heart with TWO chambers each of which the blood only passes through once; foudn in bony fishes, rays, sharks; swimming helps accelerate pace of circulation
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double circulation
pumps for 2 distinct circuts serve different tissues but combined in the heart; found in amphibians, reptiles, mammals
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pulmonary circuit
the right side of the heart carries oxygen-depleted blood away from the heart, to the capillary beds in the lungs ONLY, and returns oxygenated blood back to the heart
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pulmocutaneous circuit
found in amphibians, where deoxygenated blood is carried to the capillary beds in both the lungs AND skin
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systemic circuit
contraction of the left side of the heart carries oxygenated blood away from the heart to the body, and returns deoxygenated blood back to the heart
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cardiac cycle
one complete sequence of pumping and filling; contraction = systole, relaxtion = diastole
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cardiac output
the volume of blood each ventricle pumps per minute; determined by heart rate (number of beats per minute) and stroke volume (amount of blood pumped by a ventricle in a single contraction)
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blood _____ as it moves from arteries to arterioles to capillaries because:
SLOWS; there are MANY capillaries, therefore the overall area of campillary beds is much greater than anywhere else in the circulatory system
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endothelin
a peptide that induces vasoconstriction
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exchange of substances takes place:
across endothelial walls of capillaries
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blood pressure...
drives fluid out of capillaries
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blood proteins (albumin)...
create osmotic pressure differences between inside the capillary and the outside interstitial fluid; tends to pull fluid back into the capillaries
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edema
swelling resulting from the excessive accumulation of fluid in tissues
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lymph nodes
organs along a lymph vessel that filter the lymph and house cells that attack viruses/bacteria; play important role in body's defenses
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partial pressure
the pressure exerted by a particular gas in a mixture of gasses; Po2 = 160 mm Hg (partial pressure of O2; is much less at sea level)
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alveoli
air sacs clustered at the tips of the tiniest bronchioles; where GAS EXCHANGE occurs; maximum partial pressure of oxygen is a always LESS in the alveoli than in the atmosphere
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sufacants
specialized secretions (containing a mixture of phospholipids and proteins) that relieve the surgace tension in the fluid that coats the surface of the alveoli; in their absence alveoli collapse
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tidal volume
volume of air inhaled and exhaled with each breath; during maximum in/exhalation it's called the vital capacity, and amounts to about 3.4-4.8 L
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breathing control centers
networks of neurons that control breathing, located in the medulla oblongata [establish breathing rhythm] and pons [regulate medulla onlongata's tempo] (brainstem)
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respiratory pigments
molecule consisting of a protein and metal (metalloproteins)that binds to O2 and transport the majority of oxygen by circulating with blood (hemolymph) and are often contained within specialized cells; reduces cardiac output
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hemoglobin
vertebrate respiratory pigment that consists of 4 polypeptide chains that each contain a cofactor called a heme group with an iron atom at its center; e/a iron atom binds to 1 molecule of O2, meaning 1 hemoglobin carries 4 O2's
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Bohr shift
when low pH decreases hemoglobins affinity for O2; thus when CO2 production is greatest, hemoglobin releases MORE O2 which can be used to support cellular respiration
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