Circulation and Gas Exchange

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Circulation and Gas Exchange

• AP Biology

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Invertebrate Open Circulatory System

• Arthropods and mollusks
• Blood and interstitial fluid are the same
  (hemolymph)
• Tubular heart pumps hemolymph through a dorsal
  vessel out into sinuses
• Hemolymph bathes cells and allows for exchange of
  nutrients
• When heart relaxes, hemolymph flows back into
  vessels through ostia
• Body movements squeeze sinuses to aid circulation

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Invertebrate Closed Circulatory System

• Annelids (earthworms) have closed circulatory
  system
• 5 Aortic arches or hearts force blood down to
  the ventral vessel, which carries blood to
  posterior and up to complete the circuit
• Blood carries O2 and CO2 between cells and the
  skin where gas exchange takes place
• Blood also circulates nutrients from digestive
  tract to the rest of the body

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Vertebrate Circulatory System

• Closed system with a chambered heart that pumps
  blood through arteries that lead away from the
  heart to capillaries.
• Capillariessmall vessels in tissues where
  exchange of materials take place
• Blood is carried back to heart through veins

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Fish

• 2 chamber heart
• One artrium
• One ventricle
• Blood from ventricle picks up O2 in gills, then
  is collected into a large artery to pass directly
  to the rest of the body before returning to the
  atrium

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Amphibian

• 3 chamber heart
• Two artria
• One ventricle
• Ventricle pumps blood to both the lungs and the
  rest of the body simultaneously through 2
  different major arteries
• Allows oxygenated blood from lungs and
  deoxygenated blood from the body to mix in the
  ventricle before it is delivered back to the body
• Allows higher arterial pressure in blood pumped
  to vessels

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Birds and Mammals

• 4 chamber heart
• Two artria
• Two ventricle
• Higher metabolic need met by division of heart
  into 2 pumps
• Right atrium and ventricle pumps deoxygenated
  blood to lungs through pulmonary circulation
• Left atrium and ventricle pumps oxygenated blood
  to the rest of the body through systemic
  circulation
• Avoids mixing of oxygenated and deoxygenated
  blood
• Allows high arterial pressure required for quick
  delivery

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Human Heart

• Located beneath the sternum
• About the size of your fist
• Composed mostly of cardiac muscle tissue
• 2 atria have thin walls and function as
  collection chambers for returning blood
• 2 ventricles have thick, powerful walls that pump
  blood to the organs

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Four valves function to prevent backflow of blood

• Atrioventricular valves
• Prevent backflow when ventricles contract
• Semilunar valves
• Prevent backflow when ventricles relax

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Cardiac Cycle

• Systoleheart muscles contract and the chambers
  pump blood
• Diastoleheart muscles relax and fills with blood
• Cardiac outputvolume of blood per minute that
  the left ventricle pumps into the systemic
  circuit

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Control of Heart Rhythm

• Sinoatrial (SA) nodecells are self-excitablegene
  rate electrical impulses
• Cardiac muscle cells are electrically coupled by
  intercalated discs b/w cells

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Control of Heart Rhythm

• Atrioventricular (AV) nodereceives signal from
  atria, delays 0.1 sec, and then sends signal
  throughout walls of ventricle via the bundle
  branches and Purkinje fibers

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Blood Vessels

• Arteriescarry blood away from the heart to the
  tissues
• Branch into smaller arterioles, which supply
  blood to tissues via capillaries
• Thick-walled, muscular (smooth muscle), and
  elastic, transporting blood at high pressure
• Blood is oxygenated, except the pulmonary artery
  that carries deoxygenated blood from tissues to
  lungs through the right atrium and ventricle

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• Veinscarry blood to the heart from the
  capillaries
• Capillaries branch into larger venules, which
  supply blood to veins and back to the heart
• Thin-walled, little smooth muscle, transporting
  blood at low pressure, and contain many valves to
  prevent backflow
• Veins have no pulse and carry deoxygenated blood,
  except the pulmonary vein which carries
  oxygenated blood from the lungs
• Skeletal muscle contraction aids in systemic
  circulation

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• Capillariesthin-walled vessels (simple squamous)
  
• Permit exchange of materials between blood and
  body cells
• Controlled by precapillary sphincters

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• Capillaries
• Fluid containing water with nutrients and
  hormones seep from capillaries into tissues,
  driven by pressure
• Cells and proteins are retained in the
  capillaries and draw water back into the
  capillaries by osmosis
• Excess fluid in tissue can enter lymphatic system
  to be filtered and cycled back to the circulatory
  system

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Capillary Exchange
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Regulation of Blood Flow

• Regulated to match the metabolic needs
• Smooth muscle in walls of arterioles constrict to
  reduce blood flow to capillaries
• Smooth muscle relaxes when blood leaving
  capillaries is low in O2, allowing more blood to
  flow through capillary bed

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Regulation of Blood Flow

• Secretion of epinephrine by adrenal glands ?
  heart rate and constricts arteries to ? arterial
  pressure
• Angiotensin secreted from the kidney acts on
  smooth muscle in the arterioles and arteries to
  cause constriction and ? arterial pressure
• Vasopressin secreted by posterior pituitary in
  response to stretch sensors causes constriction
  in arterioles and arteries to ? arterial pressure

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Erythrocytes Red Blood Cells

• Primary function to carry oxygen
• Production in red bone marrow of bones stimulated
  by erythropoietin (produced by kidneys)
• Mature cells lack nuclei and circulate 4mos.
• Mature cells lack mitochondriaproduce ATP
  without oxygen through glycolysis
• Contain hemoglobin-pigment that binds oxygen

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Erythrocytes Red Blood Cells

• Red blood cells (rbc) manufacture 2 antigens,
  antigen A (Blood Type A) and antigen B (Blood
  Type B)
• Plasma carries antibodies for the antigens that
  are not present on the rbcs

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Leukocytes White Blood Cells

• Involved in immune functions in the body
• Phagocytesengulf bacteria
• Neutrophils1st to arrive at site of inflammation
• Macrophages and Monocytes
• Lymphocytes (B and T cells)immune response
• B cells produce antibodies
• Helper T cells kill infected cells

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Leukocytes White Blood Cells

• Plateletscell fragments produced in marrow
• Involved in blood clotting mechanism
• Activation of protease thrombin cleaves
  fibrinogen protein in the blood to make fibrin
  that polymerizes to for a net across the wound,
  trapping more cells and blocking the flow of blood

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Cardiovascular Disease

• Heart attackdeath of cardiac muscle tissue
  resulting from artery blockage of one or more
  coronary arteries which supply oxygen to the
  heart
• Strokedeath of nervous tissue in the brain
  resulting from artery blockage in the head

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Cardiovascular Disease

• Atherosclerosisplaques develop on inner walls of
  arteries
• Forms where smooth muscle thickens abnormally and
  is infiltrated by fibrous connective tissue
• Arteriosclerosishardening of the arteries by
  calcium deposits
• Hypertensionhigh blood pressure

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Cardiovascular Disease

• Hypertension and atherosclerosis have genetic
  component and environmental component (smoking,
  lack of exercise, high fat and cholesterol diet)
• Low-density lipoproteins (LDLs)add deposits of
  cholesterol in arterial plaques
• High-density lipoproteins (HDLs)may reduce
  cholesterol deposition
• Exercise increases HDL concentration
• Smoking increases LDL concentration

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Gas Exchange

• Involves both Respiratory system and Circulatory
  system

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Invertebrate Gas Exchange

• Water contains less oxygen than air
• As an adaptation, most aquatic animals have gills
  
• Total surface area of gills is often larger than
  that of the rest of the body

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Invertebrate Gas Exchange

• Arthropods respiratory system consists of a
  series of respiratory tubules, tracheae
• Open to the outside in the form of pairs of
  orifices called spiracles
• Tracheae subdivide into smaller and smaller
  branches, to make close contact with most cells
• Direct diffusion through tracheae is one factor
  that limits body size in arthropods

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Fish
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Countercurrent Exchange

• Maximizes exchange of gases between blood inside
  the gills and the water flowing over the gills
• Blood flows through capillaries in direction
  opposite of water flowing across gills

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Amphibians

• Simple air sac with little surface area
• Must supplement gas exchange in lungs with
  exchange across the thin moist skin

http//www.answersingenesis.org/home/area/magazine
s/images/v22frogR.jpg
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Avian Respiration

• Air sacs permit a unidirectional flow of air
  through the lungs
• Unidirectional flow means that air moving through
  bird lungs is largely 'fresh' air has a higher
  oxygen content

http//numbat.murdoch.edu.au/Anatomy/avian/fig3.2.
GIF
http//people.eku.edu/ritchisong/RITCHISO/birdresp
iration.html
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Air Flow through Avian System

• On first inhalation, air flows through the
  trachea bronchi primarily into the posterior
  (rear) air sacs
• On exhalation, air moves from the posterior air
  sacs into the lungs
• With the second inhalation, air moves from the
  lungs into the anterior (front) air sacs
• With the second exhalation, air moves from the
  anterior air sacs back into the trachea out
• Air flow is driven by changes in pressure within
  the respiratory system
• So, it takes two respiratory cycles to move one
  'packet' of air completely through the avian
  respiratory system

http//people.eku.edu/ritchisong/RITCHISO/birdresp
iration.html
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Ventilating Lungs Breathing
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Automatic Control of Breathing

• Breathing control center in brain medulla
  oblongata and pons
• Monitors CO2 levels in blood by changes in pH
• CO2 H2O ? Carbonic acid
• ? pH ? depth and rate of breathing
• ?altitude ? O2 levels
• Sensors in aorta and carotid arteries detect and
  signal control center to ? breathing rate

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Loading and Unloading of Respiratory Gases
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Oxygen Transport

• Oxygen carried by respiratory pigments
• Invertebrates utilize hemocyaninCu is the
  oxygen-binding component
• Vertebrates utilize hemoglobinfour heme groups
  surrounding an Fe atom
• Can carry four oxygen atoms

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Oxygen Dissociation Curves for Hemoglobin
Bohr Shift Active tissue releases CO2 CO2
reacts with H2O to form carbonic acid This ? pH
which induces hemoglobin to release more O2
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Carbon Dioxide Transport

• Hemoglobin transports CO2 and assists with
  buffering the bloodprevents dramatic changes in
  pH
• 7 CO2 released by cells transported as dissolved
  CO2
• 23 binds to amino group of hemoglobin
• 70 transported in form of bicarbonate ions in
  red blood cells

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