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Why closed circulatory system?
no openings to leave the vessels
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systematic circulation (path)
left ventricle - aorta - arteries, arterioles, capillaries
capillaries - collected into venules - veins - superior and inferior vena cava - right atrium
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pulmonary circulation
right ventricle - pulmonary arteries - arteries - capillaries in lungs:
venues - veins - pulmonary veins - left atrium [heart]
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Is the heart a muscle?
Yes
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systole v. diastole
- systole = ventricles contract
- diastole = relaxation of heart and then contraction of aorta
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how is the blood propelled?
hydrostatic pressure
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how is hydrostatic pressure initiated?
contraction of the heart
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how is the rate of contraction controlled?
ANS
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does ANS initiate contraction?
No
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How does it contract then?
automatically
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How does it contract? (method)
sinoatrial node (SA) in right atrium contracts at regular intervals
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How is the contraction spread?
via electrical synapses from gap junctions
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How is contraction slowed down?
parasympathetic vagnus nerve
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Where is the Action Potential spread to next?
atrioventicular node (AV node)
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what happens when AP reaches AV node, before ventricles can contract?
AV node contracts slower, allowing atria to contract and squeeze contents into ventricles
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So, AV node does what to contraction of ventricle in heart?
delays contraction -
pauses for a fraction of a second
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Where is Action Potential spread down?
bundle of His
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What is the bundle of His?
wall separating ventricles
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What are Purkinje fibers?
branches out AP through gap junctions throughout the cardiac muscles
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advantages of purkinje fibers
allows for more unified, stronger contraction
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Are arteries elastic?
Yes
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What does that say about arteries?
they stretch when filled with blood
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What allows them to stretch?
wrapped by smooth muscle
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How is the smooth muscle that allows for elasticity controlled?
sympathetic nervous system
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large arteries (muscle and sympathetic control)
have less smooth muscle
less affected by sympathetic innervation
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Are they wrapped by smooth muscle?
Yes
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What does constriction and dilation of arterioles control?
regulate blood pressure
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capillaries (relative size)
microscopic
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capillary function
intermediate for nutrient and gas exchange with tissue
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methods for material to cross capillary walls:
- 1. pinocytosis
- 2. diffusion or transport (membrane)
- 3. mvmt. through pores
- 4. mvmt. through space between cells
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when blood flows into capillary what is greater hydrostatic or osmotic pressure?
hydrostatic pressure
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So in what direction is the net fluid flow?
out of the capillary
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What happens when fluid flows out?
hydrostatic pressure drops from arteriole to venule -
osmotic pressure is greater at the venule end
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So in what direction is net fluid flow now?
into capillary
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fluid that is not reabsorbed is sent to the lymph
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What percentage of fluid is lost in the process
10%
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venules and veins
similar to arterioles and arteries
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in systematic circulation what is the main function of veins and venues?
storage
hold about 64% of blood in body at rest
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How much blood do arteries, arterioles, and capillaries hold
about 20%
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artery v. veins (direction of blood flow)
artery = caries blood away from heart
vein = carries blood toward heart
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velocity of blood flow
inversely proportional to cross-sectional area
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cross sectional area - greater in capillaries, arteries, or veins?
greatest in capillaries
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so blood moves slowest through....
capillaries
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flow rate of blood in capillaries
constant rate
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blood pressure is greater where?
increases near the heart
decreases near the capillaries
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