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Ch. 42 Circulation and Gas Exchange Title: Mar 16 9:17 PM (1 of 59)
Ch. 42 Circulation and Gas Exchange
Title: Mar 16 9:17 PM (1 of 59)
Types of circulatory systems1. Gastrovascular cavities
hydra and cnidarians, planarians and flatworms no true circulation, have cavity two cells thick that
distributes substancessubstances easily diffuse through two layers
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2. Open and closed circulatory systemsadaptation if have many cell layersboth have:
a. blood circulatory fluidb. blood vessels blood moves through thisc. muscular pump heart
have blood pressure to blood by pressure gradient
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Open circulatory systeminsects, arthropods, mollusksblood bathes organs directlyno difference between blood and interstitial fluid
fluid called hemolymphhemolymph pumped into sinuses (spaces)
Closed circulatory systemearthworms, squids, vertebrates, octopusblood is confined to vesselsinterstitial fluid and blood are separate
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Cardiovascular systemconsists of:
heart with atria(receive blood) and ventricles (pump out blood)blood vessels arteries, veins, capillaries arteries pump blood away from heart veins bring blood back to heartarteries arterioles capillaries capillary bedscapillaries venules veins
animals with high metabolic rates usually have a more complex circulatory system
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fish two chambered heart (1 atrium, 1 ventricle)amphibians three chambered heart (2 atria, 1 ventricle)
double circulation pulmonary and systemic is some mixing of oxygen rich blood with oxygen poor blood
reptiles 3 chambered, less mixing of oxyrich and oxypoor blood, have double circulation
birds, mammals 4 chambered heart, no mixing of oxyrich and oxypoor blood
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2 chambered heart three chambered heart four chambered heart
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Flow of blood through mammalian heartPulmonary circuit1. right ventricle pumps blood to lungs via pulmonary
artery2. in lungs: blood gets oxygen, gets rid of carbon dioxide3. blood returns to heart via pulmonary veins4. blood enters the left atrium5. blood goes through mitral valve to left ventricleSystemic circuit6. left venticle pumps blood through aorta7. blood in aorta goes to body via arteries
coronary arteries supply the heart muscle8. from arteries to capillary beds9. from capillary beds to veins10. veins to superior or inferior vena cava (anterior/posterior respectively)11. from vena cava to right atrium12. from rigth atrium into right ventricle
process starts again
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Cardiac Cycle= one complete cycle of contracting (pumping) and relaxing (filling)
systole = contraction phasediastole = relaxation phase
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Cardiac output= volume of blood per minute that the left ventricle pumps into the systemic system
cardiac output = heart rate x stroke volume
heart rate = number of beats per minutestroke volume = amount of blood pumped during each contraction, ave. = 75 mL
four valves in heart:atrioventicular valves between atrium and ventriclesemilunar valves between left ventricle and aorta and right ventricle and pulmonary artery
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pulse = rhythmic stretching of arteries caused by pressure of blood from contraction of ventricles
Heart sounds = "lubdup"heart murmur due to defect in valve, blood goes
backwards through valve
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Heart can beat without nervous systemsinoatrial node (SA node) = pacemaker
sets rate and timing of cardiac muscle contractions
in wall of right atriumgenerates electrical impulses that spread
through heart walls to atrioventricular node(AV node) in wall between right atrium and ventricle
travels through rest of heart muscle
measured with ECG or EKG = electrocardiogram
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Control of heart rhythym
Title: Mar 17 11:04 AM (16 of 59)
Structural Differences of Veins and Arteries
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Blood flow velocity faster in aorta than capillaries (total cross section)Law of continuity flows faster through narrower tubes than wider tubes (volume per second is constant)
Blood pressure hydrostatic pressure = fluid exerting a force on surfacesflows from high conc. to low conc.blood pressure = hydrostatic pressure that blood exerts on vesselsperipheral resistance =impedence of blood flow by arterioles
peripheral resistance
total cross sectional area decreases velocity and pressure
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Blood pressure is determined by cardiac output and peripheral resistance (work together)stress increases blood pressure by triggering nervous system and hormonal responses to constrict blood vessels
gravity also affects blood pressure, blood needs to go above heartif have long neck like a giraffe, need more pressure
blood returns to heart via veins under low pressureskeletal muscles used to push backvalves to prevent backflowbreathing pressure changes
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Valves help blood flow back to heart due to low pressure
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To measure blood pressure (mmHg)sphygmomanometer (blood pressure cuff)
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blood flow through capillaries is filled to capacity in brain, heart, kidneys, and liver
in other capillaries can be partially filled at any one time
ex. skin depending on body temperature
controlled by smooth musclesif arterioles constrict flow to capillaries decreases
also controlled by precapillary sphincter muscles before capillary beds
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since capillaries are 1 cell thick, gas exchange between cells and blood happens by diffusion
fluid flows out of a capillary at the upstream end near an arteriole, reenters near venule. direction of movement depends on the difference between two opposing forces:blood pressure and osmotic pressure
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Lymphatic system function: returns leaky fluid back into bloodfluid is called lymph when in lymphatic systemflows one way only back to heart (right atrium)
also have valves to prevent back flowlymph goes through lymph nodes on the way backlymph nodes filter lymph of viruses, bacterialymph nodes have white blood cells inside for
defense
have swollen lymph when have an infection
Title: Mar 17 11:50 AM (24 of 59)
Bloodconnective tissue
consists of: a. plasmaliquid matrix
makes up 55% of blood90% water, inorganic salts (electrolytes),plasma
proteins 1. albumin osmotic balance and pH buffer2. fibrinogen for blood clotting3. immunoglobulins (antibodies) defense
also carries nutrients, waste products, gases, hormones
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components of blood
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b. Formed elements (45% of blood)1. erythrocytes (red blood cells)
most numerous blood cell, 56million/mm3biconcave disk shapedtransport oxygen (oxygen diffuses through RBC membrane)mammalian RBC lack nuclei more room for hemoglobin(ironcontaining protein
that carries oxygengenerate ATP via anaerobic metabolismeach hemoglobin can bind 4 oxygensRBC about 120 days, get destroyed by phagocytic cells in liver and spleen, can
recycle some of the components like iron, amino acids
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Red and White blood cells
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2. Leukocytes (white blood cells)function is to fight infectionsspend most of their time in interstitial fluid and
lymphatic systemneutrophils, monocytes are phagocyteslymphocytes produce immune responsebasophilsdischarge histamine (vasodilator) at
inflammation siteseosinophils kill parasitic worms, increase during
allergy attacks (might phagocytize antigenantibody complexes)
5,00010,000/mm3
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3. Plateletsfragments of cellsfunction in blood clotting
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How do RBC, WBC and platelets get made?from pluripotent stem cells in red bone marrow (ribs,
sternum, vertebrae and pelvis)stem cells can differentiate into any type of cell
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Hematopoiesis process of making RBCnegative feedback mechanism based on amount of oxygen in bloodkidney converts a plasma protein to erythropoietinerythropoietin stimulates production of RBCif level of oxygen is too high level of erythropoietin is decreased
in leukemia cancerous stem cell linecancerous cells crowd out RBC and make WBC, some abnormal30 pluripotent cells can repopulate bone marrow
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Hemotasis process of blood clotting
platelets release chemicals that makenearby platelets sticky
collagen fibers
clotting factors from:plateletsDamaged cellsPlasma (factors include Ca, Vit K)
Prothrombin Thrombin
Fibrinogen Fibrin
platelet plugFibrin
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blood clot
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problems with clotting:a. hemophilia
sexlinked inherited traitdefect in clotting processcauses excessive bleeding even with minor cuts
and bruisesb. thrombus when platelets clump and fibrin
coagulates in a blood vesselbecomes an embolus if the clot gets loose in
blood vessel
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Cardiovascular diseasediseases of the heart and blood vesselsheart attack (myocardial infarction), death of cardiac
tissue from blockage of coronary arteriesstroke death of nervous tissue due to lack of blood flow
or rupture of blood vesselboth may result from a thrombusfibrillation when heart beats irregularly
use a defibrillizer to bring back rhythmCPR technique used to resuscitate a person who has had
a heart attackatherosclerosisimpaired arteries due to cardiovascular
diseaseplaques develop(inner wall fills with lipids and fibrous connective tissue)
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Atherosclerosis
connective tissue
smooth muscle
endotheliumplaque
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arteriosclerosis when plaques become hardened by calcium deposits
"hardening of the arteries"also lead to thrombus formationincrease risk of heart attack or stroke
angina pectoris chest pain, means heart is not receiving enough oxygen
hypertension (high blood pressure)promotes arteriosclerosis, heart attack and strokecan be controlled by diet, exercise, medication
diastolic above 90 = concern
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cholesterol low density lipoproteins (LDLs) = bad cholesterol
deposits fat in plaquessmoking increases LDL
high density lipoproteins (HDLs) = good cholesterolcan reduce cholesterol depositionexercise increases HDL
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Gas Exchangeuptake of oxygen from environment and discharge of
carbon dioxide to environmentrespiratory medium = air, 21% gas exchange occurs through respiratory surface by
diffusionsurfaces are moist so oxygen and carbon dioxide
must dissolve in moisture first
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Where does it occur?a. protists entire surface of protistb. sponges, cnidarians, flatworms plasma membranes of all cellsc. earthworm diffuse through body surfaced. fish, marine worms, mollusks, crustaceans gills
ventilation increases respiratory medium over surface (makes water move faster over gills, due to low oxygen dissolved in water) countercurrent exchange blood flows in
opposite direction of flow of water
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Gill structures
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Fish Gills
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e. tracheal systems advantages:
1. higher conc. of oxygen in air than in water2. don't have to be ventilated
disadvantage:lose water to surrounding environment
air tubes= in insectslarger insects also use body movement to help when
active
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lungslungfishes, spiders, terrestrial snails, vertebrates
frogs also use skin for gas exchangeturtles use lungs and moist tissue in mouth and anus
for gas exchangemost reptiles, all birds and mammals use just lungs
ectotherm lungs are smaller, less gas exchange area than endotherms
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Mammalian Respiratory System
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Alveoli of mouse lung
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How do we breathe?positive pressure breathing (frog)
opens mouth, brings air in nostrils, mouth/nostrils close forcing air to trachea and lungs
negative pressure breathing (mammals)works like suction pump, pulling air
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tidal volume volume of air an animal inhales and exhales with each breath (500 ml)vital capacitymaximum vital capacity during forced breathing (3.44.8 L)residual volume air left after a forced exhale
with lung diseases, residual vol. increases, while vital capacity decreases
in birds more complex (have additional air sacs act as bellows)
have parabronchi instead of alveolibetter gas exchange than mammals, high oxygen exchange
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Bird lungs
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What causes us to breathe?
breathing control centers medulla oblongata and ponsmedulla monitors level of carbon dioxide in blood
due to changes in blood and Cerebral Spinal Fluid pH
if oxygen low, sensors in aorta and carotid arteries signal breathing center
hyperventilating tricks control center too much CO2 given off so breathing shuts down until CO2 levels increase or oxygen levels decrease
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Title: Nov 307:09 AM (52 of 59)
Pressure gradients also help exchange gasesat sea level:
partial pressure of oxygen = 160 mm Hgpartial pressure of carbon dioxide = 0.23 mm Hg
if water is exposed to air, the amount of gas that dissolves in water is proportional to its partial pressure in air and solubility in water
gas diffuses from high partial pressure to low partial pressure
gas coming into lungs from cells has low oxygen partial pressure, high in air coming into lungs, so diffuses
opposite with carbon dioxide
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Partial pressure of oxygen is high in lungs, low at cells
Partial pressure of carbon dioxide is high in cells and low in lungs
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Respiratory pigments also help carry oxygenhemocyanin in arthropods = blue blood, copper carries oxygenhemoglobin iron binds to oxygen
four heme subunits with iron in eachif one oxygen attaches to iron, other subunits change shape slightly to increase affinity for oxygen (allosteric proteins)
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use dissociation curves to show amount of oxygen bound to hemoglobin at particular partial pressures
Bohr shift a shift that occurs due to change in pH that will affect hemoglobin's affinity for oxygen
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Carbon dioxide Transport
7% in plasma
23% binds to amino groups of hemoglobin
70% in form of bicarbonate ion
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Adaptations for deep sea diving
Weddell seal can store lots of oxygen in blood and muscles, 5% in lungs and 70% in bloodhas 2x vol. of blood per kilogram of body weighthuge spleen can store 24L of blood myoglobin oxygen storing protein in musclesswim with little muscular effort so don't use
oxygen quicklycan change depth by increasing or decreasing
buoyancyheart rate decreases and oxygen consumption
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