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104 Cards in this Set
- Front
- Back
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Why is diffusion insufficient to transport substances over distances of more than a few mm?
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because the time it takes for a quantity of substance to diffuse is proportional to the SQUARE of the distance
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If it takes 1 second for a given quantity of glucose to diffuse 100 micrometers, how long will it take for it to diffuse 1 mm? 1 cm?
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1 mm = 100 seconds
1 cm = 3 hours |
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how does the circulatory system solve the problem of diffusion?
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by ensuring that no substance must diffuse very far to enter or leave a cell
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what is the function of the circulatory system (besides the most obvious answer)?
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it connects the aqueous environment of the body cells to rogans that exchange gases, absorb nutrients, and dispose of wastes?
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where does exchange between the blood and interstilial fluid take place?
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in capillary beds
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why don't hydras and other cnidarians need circulatory systems?
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because they have a body wall only two cells thick which encloses a central gastrovascular cavity, which serves for both digestion and for distribution of substances througout the body
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what is unique about the gastrovascular cavity?
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the fluid inside the cavity is continious with the water outisde through a single opening
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planarians and flatworms have what kind of circulatory system?
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they don't; they have a gastrovascular cavity
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what are the 3 basic components of a circulatory system?
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1. circulatory fluid (blood)
2. a set of tubes (blood vessels) 3. a muscular pump (heart) |
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what is the motive force for blood movement in the circulatory system?
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blood pressure
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briefly describe an open circulatory system
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blood directly bathes the organs and there is not distinction between blood and interstilial fluid; the general body fluid is more correctly termed hemolymph; present in insects, other arthropods, and most mollusks
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what are sinuses?
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interconnected spaces surrounding organs
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briefly describe the closed circulatory system
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blood is confined to vessels and is distinct from interstilial fluid; present in earthworms, squids, octopuses, and vertebrates
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the heart has how many chambers?
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four (2 atria and 2 ventricles)
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what are the 3 main types of blood vessels?
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arteries, capillaries, and veins
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how long do blood vessels extend in a human?
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100,000 km
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how are arteries and veins different
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arteries carry blood away from the heart; veins carry blood towards the heart
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the complexity and number of blood vessels in a particular organ are usually correlated with what?
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the organ's metabolic requirements
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what are 3 generalized circulatory schemes of vertebrates?
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Fish, Amphibian, and Mammal
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how many chambers does a fish heart have?
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2
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how many chambers does an amphibian heart have?
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3 (1 ventricle and 2 atria)
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circulation is usually divided into which 2 parts?
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the pulmonary circuit and systemic circuit
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why is the fish heart inefficient?
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oxygen rich blood leaving the gills flows to the systemic circulation quite slowly because the blood pressure, the motive force for circulation, drops substantially
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what separates oxygen rich blood and oxygen poor blood in the ventricle of a frog?
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a ridge within the ventricle
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reptiles have what specific type of circulation?
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double circulation
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why was the evolution of the four chambered heart necessary?
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to support the endothermic way of life
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endotherms use how much more energy than similar sized ectotherms?
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10 times
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bird and mammal heart evolution is an example of what type of evolution?
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convergent evolution (birds and mammals supposedly descended from different reptilian ancestors)
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the right ventricles pumps blood to the lungs via the ______
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pulmonary arteries
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oxygen rich blood returns from the lungs to the left atrium via the ______
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plumonary veins
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blood leaves the left ventricle via the _____
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aorta
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the ______ are vessels that diverge from the aorta and supply blood to the heart muscle itself
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coronary arteries
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oxygen poor blood from the head, neck, and forelimbs is channeled into a large vein called the _______
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anterior (or superior) vena cava
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the _____ drains blood from the trunk and the hind limbs
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posterior (or inferior) vena cava
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the two venae cavae empty blood into ______
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the right atrium
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about how big is the human heart?
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the size of a clenched fist
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where is the human heart located?
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below the breastbone (sternum)
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what is the function of the two atria?
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they act as collection chambers for blood returning to the heart
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one complete sequence of pumping and filling is known as _____
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the cardiac cycle
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the contraction phase is called _____
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systole
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the relaxation phase is called _____
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diastole
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what is the cardiac output?
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the volume of blood per minute that the left ventricle pumps into the systemic circuit
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the cardiac output depends on which two factors?
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the rate of contraction (or heart rate) and stroke volume
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what is stroke volume?
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the amount of blood pumped by the left ventricle in each contraction
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what is the average stroke volume for a human?
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75 mL
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what is the average resting heart rate?
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70 beats per minute
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a person with the avg. stroke volume and avg. resting heart rate pumps how much blood per minute?
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5.25 L
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what is the volume of blood in the human body?
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5.25 L
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where is the atrioventricular valve (AV) valve located?
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between each atrium and ventricle
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how are AV valves anchored?
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by strong fibers that prevent them from turning inside out
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how are AV valves closed?
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by the pressure generated by powerful contraction of ventricles
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what is the function of the AV valve?
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it keeps the blood from flowing back into the atria
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where are semilunar valves located?
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at the two exits of the heart, where the aorta leaves the left ventricle and the pulmonary artery leaves the right ventricle
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how are semilunar valves opened?
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they're forced open by pressure created by ventricular contraction
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how are semilunar valves closed?
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when ventricles relax, blood starts to flow back toward the ehart, flosing the semilunar valves, which prevents blood from flowing back into the ventricles
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how long does a complete cardiac cycle last?
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0.8 seconds
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how long is the relaxation phase (atrial and ventricular diastole)
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0.4 seconds
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how long does it take for the atrial systole to force all the remaining blood out of the atria and into the ventricles? (ventricular diastole)
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0.1 seconds
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how long does it take for the ventricle systole to pump blood into large arteries? (atrial diastole)
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0.3 seconds
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the "lub-dup" sound of the heart is caused by what?
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the closing of valves
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the "lub" sound of "lub-dup" is caused by what?
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by the recoil of the blood against the closed AV valves
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the "dup" sound of "lub-dup" is caused by what?
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by the recoil of blood against the semilunar valves
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what is heart murmur?
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when a stream of blood squirts backward through a valve, usually caused by a defect in one or more of the valves
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how are hear murmurs caused?
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some people are born with it; others can have it damaged by infection (from rheumatic fever, for instance)
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true or false: heart murmurs reduce the efficiency of blood flow so much that surgery is required
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false
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certain vertebrate cardiac muscle cells are self-excitable. what does this mean?
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they contract without any signal from the nervous system
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what is the function of the sinoatrial (SA) node (aka the pacemaker)?
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it sets the rate and timing at which all cardiac muscle cells contract
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where is the SA node located?
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in the wall of the right atrium, near the point where the anterior vena cava enters the heart
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how does the SA node make the cardiac cells contract in unison?
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it generates electical impulses, which spread rapidly through the walls of the atria, making them contract in unison
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where is the atrioventricular (AV) node located?
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in the wall between the right atrium and the right ventricle; it acts as a relay point for electrical impulses from the SA node
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how long are impulses delayed at the AV node before spreading to the walls of the ventricles? why does this occur?
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0.1 seconds; it ensures that the atria empty completely before the ventricles contract
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what is an electrocardiogram? (ECG or EKG)
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a record of the electrical impulses that travel through the cardiac muscle during the heart cycle
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how are electrical impulses that proudce an ECG detected?
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impluses that travel through the cardiac muscle produce electrical currents that are conducted through the body fluids through the skin, where they are detected by electrodes
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what is the effect of epinephrine on heart rate?
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increases it
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a body temp. increase of 1 degree celcius increases the heart rate by how much?
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10 beats/min
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what are bundle brances and Purkinje fibers?
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specialized muscle fibers that conduct the signals to the apex of the heart after signals are delayed at the AV node
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what are the 3 main tissue layers of areteries and veins? briefly describe them
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1. connective tissue on the outside (allow vessel to stretch and recoil)
2. smooth muscles and elastic fibers in the middle (more elastic fibers) 3. endothelium lining the lumen of all blood vessels, including capillaries (provides a smooth surface that minimizes the resistance to the flow of blood) |
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what's the function of capillares?
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to exchange substances between blood and interstilial fluid
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what is the function of elastic fibers in arteries?
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to maintain blood pressure even when the heart relaxes between contractions
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how does the structure of a vein correlate with its function?
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the thinner walled veins convey blood back to the heart at low velocity and pressure
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compare the rate of blood flow in the aorta versus the capillaries
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blood travels over a thousand times faster (about 30 cm/sec) than in capillaries (about .026 cm/sec)
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why do capillaries how such a slow blood flow compared to arteries and veins?
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there are so many of them and their cross sectional area is large
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true or false: capillaries are the only vessels with walls thin enough to permit the transfer of substances between the blood and the interstilial fluid
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true
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how does blood flow through the veins?
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contractign skeletal muscles squeeze the veins, and flaps of tissue within the veins act as one way valves that keep blood moving only toward the heart
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why do our feet swell if we sit or stand too long?
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the lack of muscular activity causes our feet to swell with stranded blood unable to return to the heart
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what is hydrostatic pressure?
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a force that a fluid exerts against the surfaces it contacts
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fluids always flow from areas of _____ pressure to areas of ____ pressure
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high; low
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where is blood pressure the highest: arteries, veins, or capillaries?
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arteries
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what is peripheral resistance?
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when the heart contracts, it forces blood into arteries, but the blood does not leave the arteries to enter the arterioles fast enough, and the arteries expand
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what is the average arterial blood pressure of a healthy resting human at systole and diastole?
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systole = 120 mm Hg
diastole = 70 mm Hg |
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blood pressure is determined by what 2 factors?
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cardiac output and peripheral resistance
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describe blood pressure as it relates to arteries and arterioles
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when the smooth muscles of the arterioles contract due to increased peripheral resistance, pressure in the arteries increases; when smooth muscle in the arterioles relaxes, pressure in the arteries drops
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what happens to arterioles during exercise?
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they dilate and allow for greater blood flow
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in large land animals what is another factor that affects blood pressure (hint: it has to do with physics; the first letter of it is g, and ends in -ravity)
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gravity (the human heart must expend an extra 27 mmHg of pressure to raise the blood from the heart to the brain, a height of .35 m)
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how does blood from the veins reach the heart if so much resistance has been encountered in the arterioles and capillaries?
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1. by rhythmic contractions of smooth muscles in walls of venules and veins
2. activity of skeletal muscles 3. the change in pressure within the thoracic cavity when we inhale |
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at any given time, about what percent of our bodies' capillaries have blood flowing through them?
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5-10%
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give one reason why exercising after eating a meal causes indigestion
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when you exercise, the blood flow is diverted away from the digestive systema and to the skeletal muscles and the skin
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what are two mechanisms by which blood flow in capillary beds is regulated?
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1. smooth muscles in walls of arterioles contract and relax
2. precapillary sphincters (located at the entrance to capillary beds) control the flow of blood between arterioles and venules |
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what is a sphygmomanometer?
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an inflatable cuff attached to a pressure gauge which measures blood pressure in an artery; the cuff is wrapped around the upper arm and inflated until the pressure closes the artery, so that no blood flows past the cuff; when this occurs, the pressure exerted by the cuff exceeds the pressure in the artery
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in what ways can substances be exchanged between the endothelial walls of the capillaries and the interstilial fluid?
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1. endocytosis
2. diffusion (passive, facilitated) 3. pressure pushes fluid through the capillary clefts, which causes a net loss of fluids from the upstream end of the capillary |
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as blood passes through the capillaries, what happens to its osmolarity? why?
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it increases; blood cells suspended in blood and most proteins dissolved in the blood are too large to pass readily through the endothelium; also, the blood loses fluid during its passage thorugh a capillary
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what is the result of the increased osmolarity as blood travels through a capillary?
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the osmotic gradient pulls water into the capillary by osmosis near the downstream end
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about what percent of the fluid that leaves the blood at the arterial end of a capillary bed reentes at the venous end?
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85%
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how are fluids lost from the blood returned?
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1. reenter through the venous end
2. the lymphatic system |
