Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Functions of circulation To transport: 1. Solutes - gases - nutrients - chemical wastes - chemical signals- hormones 2. Heat - insects 3. Force - use in locomotion (e.g. spiders, slugs) - use in ultrafiltration across membranes 4. Immunity 5. Clotting A version of proposed evolutionary relationships between animal phyla Poriphera No tissues Unicellular organisms Cnidaria Multicellulariity Radial symmetry Ctenophora True tissue organization Platyhelmintha Evolution of Circulatory systems No body cavities Bilateral symmetry Body cavity develops from other cells Have body cavities and blood vascular system Body cavity develops from mesoderm Nematoda Annelida Arthropoda Mollusca Echinodermata Hemichordata Urochordata Chordata Vertebrata Comparative circulatory systems Components of circulation system 1. Pump 2. Channels 3. Blood/Hemolymph Methods of circulation Circulation of external medium in Poriphera and Cnidaria (propulsion by cilia, flagella, or muscle contraction) Open circulatory system of arthropods and most molluscs Closed circulation in annelids and cephalopod molluscs; respiratory surface may be skin or gills hemocoel heart heart respiratory surface Open vs. closed systems Closed •Blood remains in vessels •High pressure •Regulate flow to each organ •Return to heart rapid •Found in: vertebrates, echinoderms, cephalopods* (why?) annelids* Open •Blood directly bathes tissues •Usually lower pressure •Less regulated flow •Return to heart slower •Found in: most arthropods, urochordates most other molluscs Vertebrate respiratory mechanisms Efficiency of O2 extraction Types of pumps: Peristaltic e.g. squirt; insect; worms Contractile chamber e.g. vert. branchial heart Tube chamber with separate muscles e.g. vert. veins Flow in rigid tubes Flow in a rigid tube can be described by: Average flow velocity will be flow volume rate Q divided by the x-sectional area Q = Velocity š r2 Poiseuille’s Law Q = (P1-P2) š r2 8Lh Q=P/R Q is flow volume rate (P1-P2) is pressure diff. r is radius of tube L is length of tube h is fluid viscosity Flow dynamics Bernoulli’s theorem: Energy = Pressure + Kinetic + Gravity E=(pv)+(mgh)+(1/2mu^2 Where does the energy go? Flow dynamics Bernoulli’s theorem: Flow from high E to low E (not high P to low P) Energy = Pressure + Kinetic + Gravity assume flow rate steady (no other path) Vessels are not rigid tubes compliance- (1/spring constant) • Veins are volume reservoir and high compliance. Terrestrials!! Stand up and you might get a head rush, which is actually an “out of head rush”. Compensated by adrenergic fibers. If you prick me and I bleed, do I not vasoconstrict? • Arteries are pressure reservoir. Less compliance. Smooth heartbeat. Keep pressure relatively constant to not strain capillaries. Also maintain efficiency of diffusion with constant velocity. The body plan of platyhelminths makes diffusion an effective mechanism of transport. S/V= 6 L2/L3 Fick equation: J = k(Cs - Cx) Only good when: very small, very thin, very inactive-or all three What energy drives this? where J = quantity of a commodity moved per unit time k = a constant related to how readily the commodity can move Cs = concentration at the source Cx = concentration some distance away from the source A very simple distributing system: the gastro-vascular system of Cnidaria radial canal Each canal is lined with beating cilia ring canal Aequorea victoria, Open circulation in insect Low metabolism? Pulsatile organs Dorsal diaphragm Nerve cord septa Insect circulation Anterior dorsal aorta peristalsis Accessory pumps for antennae, legs, wings External muscles assist filling of dorsal heart (“suction”) Typical crustacean circulation THE ANIMAL OF THE DAY Hagfish (Ph:Chordata; ?:Agnatha) <2 feet Why is it interesting? • Unlike other chordates, hagfish possess several hearts. • A systemic heart & accessory hearts to help with venous return. • Mostly closed circulation, but some sinuses w/o endothelium. • As much as 80% of O2 through skin. • Systemic heart is myogenic, & not innervated. • Blood pressure is quite low. THE ANIMAL OF THE DAY Hagfish (Ph:Chordata; ?:Agnatha) Amphibian (bullfrog, Rana) What happens when the frog dives? separate at high flow rates * crocodiles dive too??? S = O2 saturation Control of heart rate 1. Neurogenic hearts- beat initiated by CNS - annelids, crustaceans, arachnids 2. Myogenic hearts - they got rhythm - vertebrates, most molluscs, some insects - are modulated by autonomic CNS sympathetic v. parasympathetic input (noreprinephrine v. acetyl choline) How change amount transported? The volume transported over time (Q) can be changed by: Q=f•V 1. Increased rate of pumping (f). e.g birds, mammals 2. Increase volume (V) for each stroke of the pump. e.g. fish 3. Increased carrying capacity of the fluid (i.e. blood). Each of these can account for individual differences or species diff. Heart rate decreases w/size mammals Heart rate decreases w/ mammal size log scale mammals Why? (slope) Other methods? (predict slope) logarithmic relationship: r=k•Mb (b = slope = –.25) log r = log k • b(logM) log scale Heart mass directly proportional to body mass (0.6%) in mammals Stroke volume is proportional to body mass in mammals, and can not account for phylogenetic variation in metabolism. h.m. = k • b.m 0.98 Heart rate v. Stroke volume * What else is changing? * Lower volume Q compensated by carrying capacity Hemocyanin is an O2 carrying pigment found in many invertebrate bloods. Unlike Hb, it is dissolved in the hemolymph. The total cross-sectional area of the vessels increases with distance from the heart. Q = Velocity š r2 Why? Consequently, the velocity of flow decreases, and then increases after passing the capillaries. Blood pressure decreases away from heart As x-sectional area increases, pressure decreases in arterioles. When x-sectional area decreases again in venules, the pressure does not return due dissipation due to friction w/ capillaries. Distribution of blood Control of cardiovascular systems Baroreceptors - atrial tonic receptors cause reflexive compensation Chemoreceptors (CO2, O2, pH) - if CO2 increases or O2, pH decrease, then slow heart if not breathing (how maintain B.P.?) Stretch receptors - increased atrial volume changes hormones to inc. urine Thermoreceptors Sympathetic v. parasympathetic centers & signals Feedback control in circulation Control of capillaries Nervous system: - Sympathetic norepinephrine to a-adrenergic receptors. - Parasympathetic ACh release. (effects on heart rate?) Local control: NO; peptides; histamine Adaptation to posture changes tree snakes have tight skin and anteriorly displaced hearts ground snakes will pass out if held upright too long Pressure in humans Giraffe (Ph:Chordata, Ge:Giraffa) Lowering head could result in aneurysm. Giraffe (Ph:Chordata, Ge:Giraffa) • lower heart pressure & vasodilation • tight skin around legs prevents pooling • prehensile tongue What color? Don’t worry, sea slugs also have the same problem Exercise 1) Vasodilation in muscles; reduce resistance, reflex increases cardiac output. 2) Increased heart rate and force; stroke vol. in fish. 3) Release RBCs from spleen. Diving Diving verts need to limit consumption of O2. If CO2 builds up, and lungs not stretched, then peripheral vasoconstriction -> reduced heart rate. (vice-versa if lungs stretched) Bradycardia shown by forced dive animals. Not in free diving animals, unless chased. Distribution of blood flow Relative osmotic pressure & exchange Ultrafiltration. protein colloids regain some fluid not quite even; lymph Phylogeny of respiratory pigments Respiratory Pigments