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Unformatted text preview: Circulation and Gas Exchange
1. Circulatory Systems: General Features 2. Vertebrate Circulatory Systems Overview: Structure of the Heart and Circulatory Pathway Cardiac Cycle: Systole and Diastole Control of Heart Beat Blood Vessels Blood Pressure Lymphatic System 3. Composition of Blood 4. Respiratory Pigments 5. Platelets Blood Clotting 6. Gas Exchange (Gills, Trachea, Lungs) Common Elements of Animal Circulatory Systems
• Circulatory Fluid: Blood or Hemolymph • Tubing: Vessels • Pump: Heart There are Two Types of Circulatory Systems
• Open: – He m o ly m p h d ire c tly b a th s o rg a ns a nd th e re is no d is tinc tio n b e twe e n th e “blood” a nd th e fluid th a t s urro und s th e c e lls “lymph”. – Fo und in invertebrates – especially insects and mollusks. • Closed: – Blo o d is c o nfine d to ve s s e ls a nd is ke p t s e p a ra te fro m th e inte rs titia l lym p h . – Fo und in a ll ve rte b ra te s a nd a fe w inve rte b ra te s like th e e a rth wo rm . O p e n a nd C lo s e d Fig. 42.3 Campbell Vertebrate Closed Circulatory Systems Gas exchange with the environment: blood picks up O2 Gas exchange with tissues of the body: blood releases O2 Fig. 42.4 Campbell Circulatory Pathway: Overview See page 903 in text Fig. 42.6 & 42.7 Campbell Pacemaker for the Vertebrate Heart
Fig. 42.9 Campbell and Reece • The vertebrate heart is “myogenic”. The “pacemaker” is made of specialized muscle tissue, the sinoatrial node (SA) located in the wall of the right atrium An action potential is spontaneously initiated in the SA Cardiac muscle cells are electrically coupled so the impulses spread rapidly in the atria After a delay of ~0.1 sec, impulses are relayed to the ventricles by another region of specialized muscle tissue, the atrioventricular node (AV) which is located in the wall between the right atrium and the right ventricle. • • • C a rd ia c C y c le : Ma m m a ls
1. Mus c le re la xe d (d ia s to le ) : b lo o d flo ws into a tria a nd ve ntric le s 2 . S ino a tria l no d e initia te s a c tio n p o te ntia l in a tria l m us c le 3 . Atria c o ntra c t (s ys to le ) : fo rc e s b lo o d fro m a tria into ve ntric le s 4 . Ac tio n p o te ntia l is d e la ye d in th e a trio ve ntric ula r no d e , th e n re la y e d to th e ve ntric le s 5 . Ve ntric le s c o ntra c t (s ys to le ) : b lo o d p um p e d into a rte rie s Fig. 42.7 Campbell A Beating Human Heart and Its Valves Blood Vessels
Blood pressure is high in the arteries but low in the veins. Thus the veins can have thinner walls, but need valves to prevent the backflow of blood. The flow of blood can be regulated by signals from the endocrine or nervous systems that cause contraction of the smooth muscle surrounding the vessels constricting the flow. Fig. 42.9 Campbell Regulation of Blood Flow Through Vessels An Unconventional Signal Molecule Arginine + O2 NOS • NOS = nitric oxide synthetase (regulated by Ca ions) • Not released by exocytosis (diffuses freely across cell membranes) • Does not interact with conventional “receptors” of target cells • Its major mechanism of action is the direct stimulation of guanylate cyclase in target cells for the production of cGMP. Nitric Oxide: NO + citrulline Vasodilation & Viagra
Endothelial cells contain a Ca++ regulated enzyme – Nitric Oxide Synthase. NO activates guanylate cyclase in the smooth muscle of the blood vessels. cGMP activates a kinase that, in turn, triggers increased Ca++ uptake into the endoplasmic reticulum. As Ca++ level fall, the muscle relaxes, the vessel dilates, and blood flows Viagra (initially developed for use on hypertension) is an inhibitor of cGMP phosphodiesterase Blood Pressure Fig. 42.11 Campbell A giraffe has to pump blood 2.5 meters above heart. This requires a systolic pressure of 250 mm Hg. In humans, blood pressure this high (hypertension) would damage vessels. Pressure and Fluid Exchange Fluid and proteins that do not reenter the capillary system (about Fig. 42.14 Campbell 15%) are recovered by the lymphatic system. This is a separate system of vessels that collects and returns to fluid to the circulatory system at a junction near the heart. Composition of Blood Fig. 42.15 Campbell Platelets: Blood Clotting
Platelets stick to collagen fibers and form a plug, then release clotting factors. Hemophilia is a common hereditary disease in which one of the clotting factors is missing or defective Prothrombin is a plasma protein Thrombin is an enzyme Fibrin threads weave into a patch that stabilizes the plug. Fig. 49.16 Purves Gas Exchange: CO2 O2
Trachea, Gills, Lungs Maximize Surface Area for gas exchange Insect Trachea Lungs Salmon Gill • Hemocyanin – Copper + protein (Crustacea, Mollusks O2 transport) • Hemoglobin – Ironheme + protein (Red Blood Cells, O2 transport) • Myoglobin – Ironheme + protein (muscle, O2 “Storage”) O2 Transport: Examples of Respiratory Pigments Each red blood cell contain about 250 million molecules of hemoglobin There are about 25 trillion red blood cells in the blood Carbon Dioxide Transport Catalyzed by Carbonic Anhydrase A small amount of CO2 is transported in solution in blood plasma (7%). About a quarter of it is bound to hemoglobin, and the rest is in the form of bicarbonate ions (H CO3 ). ...
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This note was uploaded on 11/12/2010 for the course BSCI BSCI 110B taught by Professor Johnson during the Spring '09 term at Vanderbilt.
- Spring '09