Circulation Chpt. 44

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CirculationChpt. 44

• Transportation, cardiac cycle, evolution of
  advanced systems

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• Oxygen and nutrients obtained for simple
  organisms by diffusion
• cnidarians and flatworms bodies only 2 cells
  thick
• Development of multi-layer tissues
• Oxygen and nutrients transported in liquid via
  circulatory system
• Open mollusks, arthropods,
• no distinction between circulating fluid and
  fluid of body tissues
• Called hemolymph
• Closed blood enclosed in vessels, transport
  away and back to a pump (heart)
• Some invertebrates (annelids)

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Vertebrate Circulatory Systems

• Transportation
• Respiratory, nutritive, excretory
• Regulation
• Hormone transport
• Temperature regulation (vasoconstriction/dilation,
  countercurrent heat exchange)
• Protection
• Blood clotting
• Immune defense

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Blood

• Composed of fluid plasma
• Interstitial fluid originates from plasma
• Matrix in which blood cells and platelets are
  suspended
• Metabolites, wastes, hormones
• Ions
• Proteins carriers and clotters
• Red Blood Cell/Erythrocytes
• Oxygen transport, 45 of blood
• Doughnut shaped increases surface area
• Hemoglobin pigment
• Develop from stem cells
• Plasma oxygen levels decrease, bone marrow
  creates more
• Mammalian no nucleus, removed as age

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White blood cells and platelets

• Immunological defenses
• Less than 1 of blood
• Larger, have nuclei, not confined to blood
• Several types, each have specific job
• Platelets pieces of megakaryocytes
• Injury smooth muscle contracts, constriction
• Platelets accumulate, stick to each other via
  fibrin

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Blood vessels

• Blood leaves heart via arteries which branch to
  reach organs,
• Finest branches are arterioles, enters
  capillaries
• Collected in venules led to veins
• Arteries, veins same basic structure
• Innermost endothelium, elastic fibers, smooth
  muscle, connective tissue layer
• Too thick to permit exchange
• Capillaries only endothelium
• Diffusion, filtration, transport

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Arteries and arterioles

• Transport blood away from heart
• Larger arteries more elastic fibers
• Smaller thick smooth muscle
• Vast tree frictional resistance
• Narrower vessel more resistance to flow
• Regulated by constriction and dilation
• Precapillary sphincters limits heat loss in cold

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Exchange in capillaries

• Sufficient pressure needed to pump against
  resistance
• Every cell is within 100 micromteres of a
  capillary
• Capillaries 1 millimeter long, 8 micro in
  diameter
• Slightly wider than erythrocyte, must be flexible
• Although narrow, number means greatest total area
  than any vessel
• Blood has more time in capillaries,
  releases/pick-up
• Loses pressure and velocity, is under low
  pressure in veins

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Venules and veins

• Venules-veins-heart
• Less muscle because less pressure
• Can expand to hold additional blood
• Skeletal muscles can contract to move blood back
  to heart venous pump
• One way back to heart, venous valves

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Lymphatic System

• Closed all vessels connected with another
• Some water and solutes do filter through
  capillaries to form interstitial fluid
• Supplies tissue cells with oxygen and nutrients
• Exits near arteriolar end where pressure is
  higher, re-enters by osmosis (oncotic pressure)
• Lymphatic is open, returns rest of fluid to
  cardiovascular
• Capillaries, vessels, nodes, organs including
  spleen and thymus
• Activate some white blood cells

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Circulatory and respiratory adapatations

• Large body size and locomotion of animals
  possible because of coevolution of systems
• Needed more efficient
• ways to transport
• Circulation and respiration
• linked

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Fish heart

• Early chordates had simple tubular hearts
• Gills of fish required chamber-pump heart
• Peristaltic sequence, heartbeat initiated by
  electrical impulse
• Gills oxygenate blood, but looses pressure
  developed by heart contraction

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Amphibian/reptilian

• Lungs blood is oxygenated then returned to
  heart
• Two circulations pulmonary heart/lungs
• Systemic heart/body
• Separates oxygenated from deoxygenated
• Right atrium receives deoxygenated from
  systemic
• Left atrium receives oxygenated from lungs
• Little mixing in ventricle
• Oxygenated blood to aorta, major artery
• One ventricle with incomplete separations
• Separation of pulmonary and systemic is
  incomplete
• Amphibians can diffuse extra oxygen

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Mammalian and Birds

• Four chambered heart
• Two atria and two ventricles
• Right atrium receives deoxygenated blood,
  delivers to right ventricle, which pumps to blood
  to lungs
• Left atrium receives oxygenated blood from lungs,
  delivers to left ventricle, which pumps blood to
  body
• Occur simultaneously increased efficiency
• Closed system same amount of blood pumped by
  both ventricles at same time
• More pressure generated by left ventricle
• Sinus venosus pacemaker
• site of heartbeat impulse
• Major chamber in fish
• Reduced through amphibians,
• reptiles
• Mammals/birds no longer
• separate chamber tissue remains
• in right atrium sinoatrial (SA)
• node

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Cardiac cycle

• Two separate pumping systems within one organ
• Two pairs of valves
• Atrioventricular (AV) valves guard openings
  between atria and ventricles
• Ttricuspid valve exit of right atrium
• Bicuspid valve exit of left atrium
• Semilunar valves guard openings between
  ventricles and arteries
• Pulmonary right ventricle to lungs
• Aortic left ventricle to body
• Valves open and close during cardiac cycle
• rest (diastole) and contraction (systole)

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• Blood returns to resting heart (diastole)
• Deoxygenated blood into right atrium
• Oxygenated blood into left atrium
• Ventricles contract (systole)
• AV valves close (lub), push semilunar valves open
• Ventricles relax, semilunar close (dub)

http//www.nhlbi.nih.gov/health/dci/Diseases/hhw/h
hw_pumping.html
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Veins and arteries

• Pulmonary arteries to lungs
• Veins back to heart
• Aorta
• Superior vena cava
• Inferior vena cava

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Electrical excitation

• Heart contains specialized autogenic depolarizing
  cells
• Spreads from SA node to atria to ventricles
• Recorded on EKG
• Largest peak is polarization of ventricles

http//www.nhlbi.nih.gov/health/dci/Diseases/hhw/h
hw_electrical.html
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Blood Flow and Blood Pressure

• Cardiac output has normal resting rate
  (5L/minute)
• Increases during exercise (25L/min)
• Vasoconstriction/dilation direct extra blood to
  important areas
• Increased blood pressure increase in heart rate
  or vasoconstriction
• Can be regulated by hormones to increase blood
  volume

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Blood Volume Regulation

• ADH antidiuretic, prevent dehydration
• Aldosterone vasoconstriction
• Atrial Natriuretic Hormone release Na and
  water
• Nitric Oxide gas acts as a hormone -
  vasodilation