Study Guides (248,454)
Canada (121,562)
HMB302H1 (5)
all (1)

BIOB34_Textbook notes for Midterm 2 readings, Lec 11-15.docx

10 Pages
Unlock Document

Human Biology
All Professors

BIOB34 – Lecture Notes for Midterm 2 Readings Chapter 8: Circulatory Systems  Common features of animal circulatory systems: o transport oxygen and nutrients o remove CO2 and other waste products o help coordinate physiological processes by transporting signaling molecules o assist in defense of body by transporting immune cells to site of invasion  heart is developed very early because it is needed to develop other components of circulatory system (valves, chambers, capillaries) o pressure in blood vessels cause vessels to grow and sprout  Diffusion is not efficient at transporting nutrients over long distances o time needed for diffusion directly proportional to (x^2) or square of distance between 2 points o larger animals move fluids through body by process called bulk flow / convective transport o in bulk flow, external force is applied to fluid to set it in motion (ie- moves from high to low pressure) Characteristics of Circulatory System  has 3 components: o pump/propulsive structure that applies force to the liquid o system of tubes, channels or spaces through which the fluid flow o fluid that circulates system  Pumping structures: o Heart: muscular contractions of heart increased the pressure inside heart chambers  when pressure in heart exceeds the rest of circulatory system, blood flows down pressure down the gradient  one-way valves help ensure unidirectional flow  usually first enters the ‘atria’ (reservoirs), then into muscular chamber ‘ventricles’ (pump) o External pump: skeletal muscles used to develop pressure gradients  ie – in terrestrial animals, skeletal muscles in leg help propel blood back up to heart o Peristaltic contraction or tubelike hearts: found in invertebrates and early vertebrate embryos move blood by peristalsis  rhythmic waves of muscle contraction in a coordinated faction from one end of tube to other  Circulatory systems: o blood carried through enclosed blood vessels o Closed circulatory system: fluid remains within blood vessels at all points  substances may diffuse across walls of blood vessels to enter tissues o Open circulatory system: circulating fluid enters sinus at least at one point in circulatory system and comes in direct contact with tissues  allows circulating fluid to mix with extracellular fluids  Types of Fluids: o Interstitial fluid: extracellular fluid that directly bathes the tissues of vertebrates/invertebrates o Blood: fluid that circulates within a closed circulatory system (a complex tissue with many components) o Plasma: contains proteins and variety of cells o Lymph: formed by ultrafiltration in small blood vessels  pumps ultrafiltrate through the body and returns to the circulatory system o Hemolymph: circulating fluid of open circulatory systems  sinuses of open systems collectively called ‘hemocoel’  Diversity of Circulatory Systems  Sponges (porifera): propel water through bodies using ‘choanocytes’ – specialized cells with rhythmically beating flagellae  Cnidarians: propel water from external medium through their mouths into gastravascular cavity o uses muscular contractions to pump water down to tentacles  Flat worms: have gastrovascular cavity lined with ciliated ‘flame cells’ – beating propels water containing food particles to all parts of body  Nematodes: lack specialized circulatory systems, but can move interstitial fluid through body cavity by bulk flow contractions of muscles in their body walls o obtain oxygen by simple diffusion across body surface  Annelids: divided into 3 main branches o Polychaeta (ie – tube worms) have open circulatory o Oligochaeta (ie – earth worms) have closed circulation  have series of blood vessels connecting large dorsal and ventral blood vessels that run the length of the animal  dorsal vessel can contract and moves blood toward head using rhythmic waves of peristaltic contraction (with tubelike hearts)  Molluscs: all have hearts/contractile organs and most are open circulatory systems o Cephalopods (octopus) has closed circulatory system with 3 muscular chambered hearts  Arthopods: all have open circulatory systems with one or more hearts and some blood vessels o have small holes called ostia that can be opened/closed to regulate blood flow  Chordates: o Invertebrate urochordates (ie – tunicates): have simple tubular heart that propels fluid through series of channels in the tissues. Some tunicates can reverse blood flow direction by changing contraction o Cephalochordates (ie – lancelets): lack obvious chambered heart, have long tubular heart/contractile blood vessel, mostly a closed system with few exceptions  thus closed circulatory systems seem to have evolved convergently from many different routes (by vertebrates, cephalopod mollusks, and annelid worms) Vertebrate Circulatory Plan  Artery: carry blood away from heart o branches into succeedingly smaller arteries called arterioles o thin walled vessels called capillaries is the primar site of diffusion of material into the tissues o small vessels called venules then being larger vessels called veins that return blood to heart o also form ‘Anastomoses’: connections from one blood vessel to another, as an alternate pathway for blood to flow if one route is blocked  Complex walls of vertebrate blood vessels: o Tunica intima: innermost layer of the blood vessel  has lining called vascular endothelium, made of smooth sheet of epithelial cells o Tunica media: middle layer, composed of smooth muscle and sheets of extracellular matrix protein ‘elastin’  contraction causes vasoconstriction and vasodilation o Tunica externa: composed of collagen fibres that support and reinforce the blood vessel  Wall thickness varies among blood vessels o arteries have thick-walls with thicker tunica externa and tunica media (making them more elastic) o Paracellular pathway: pores between cells of the capillary walls allow small molecules (water, ions) to move across o Vein has thinner wall and larger lumen (space inside wall) than the similarly sized artery  Angiogenesis: after embryonic development, blood vessels undergo constant remodeling through life o reproduction of new blood vessels (ie – for uterine lining), to heal wounds o controlled by activator and inhibitor molecules  paracrine signaling molecules bind to receptors on the endothelial cells of existing blood vessels  binding of growth factor to its receptor activates signal transduction cascade that results in endothelial cells to proliferate  specialized integrin proteins help pull sprouting blood vessel forward  research for drugs to stimulate angiogenesis tested for coronary artery disease, late-stage diabetes (when blood vessels in feet begin to fail).  Vertebrate circulatory systems: o water-breathing fish have single-circuit circulatory system: blood flows from heart, through gills to body tissues then back to heart o Tetrapods (amphibians, reptiles, birds, mammals) have 2 circuits within circulatory system  Pulmonary circuit: right side of heart pushes blood through lungs  Systemic circuit: pushes blood through rest of circulatory system  Mammals and birds have completely separated pulmonary and systemic circuits o allows pressures to be different in pulmonary and systemic circuits (ie – in pulmonary, blood must flow through capillaries with low pressure to flow through thin capillaries without damaging)  but, high pressures needed to force blood through the long systemic circulatory system o Amphibians and tetrapods have incompletely separated pulmonary and system circuits  thus it’s possible for oxygenated and deoxygenated blood to mix Physics of Circulatory Systems  Law of Bulk Flow: Q = delta(P) / R o Q = flow, delta(P) = pressure gradient, R = resistance  Radius of tube affects it’s resistance o liquids with higher viscosity have higher resistance: R = 8Ln/(pi*r^4) o Poiseuille’s equation: Q = (delta(P)*pi*r^4)/8ln  R= resistance, L = length of tube, n = viscosity of fluid, r = radius of tube o Conclusions from Poiseuille’s equation:  animals can control flow through organs by changing radius of blood vessels (vasodilation-less resistance/vasoconstriction-more resistance)  blood vessels can be arranged in series or in parallel o Series: total resistance of circuit with resistors arranged in series is sum of individual resistances (Rt = R1+R2+..). Thus, total resistance of circuit increases o if resistors added in parallel: 1/Rt = 1/R1 + 1/R2… the total resistance of circuit decreases  Velocity of blood flow is dependent on pressure and cross-sectional area o velocity inversely related to cross-sectional area: In narrower channels-blood is likely to flow slower than normal, in wider channels- blood flows faster  important to go slower in capillaries because it takes to time for substances to diffuse o Blood velocity = Q/A; Q = flow, A = sum of cross-sectional areas of channel  Pressure exerts force on walls of blood vessels o LaPlace law: T = alpha*P*r  alpha = constant, P = transmural pressure (difference between internal and external pressure), r= radius of vessel  to take account of thickness of vessel: sigma = Pr/w, sigma = wall stress (force/unit cross- sectional area of wall), w= thickness of wall  as thickness as vessel increases, stress in the wall of vessel decreases (thus aorta must be thicker or made of stronger material than arterioles, veins)  LaPlace explains that when vessel dilates, stress/tension in wall is increased although pressure remains the same Heart (pg 366)  Cardiac cycle (pumping action of heart) includes Systole (contraction) and Diastole (relaxation) phase o Systole: heart contracts, increasing pressure inside chambers and forcing blood out into circulation o Diastole: heart relaxes, reducing pressure within chambers of heart and allowing blood to enter from circulatory system  Arthopod Hearts: pump hemolymph into circulation via arteries o blood returns to heart via ostia (series of holes). Valves in ostia open and close to regulate flow of hemolymph o heart held in place by suspensory ligaments o Neurogenic heart – contracts in response to signals from nervous system  primary rhythm generators – undergo depolarizations to initiate contractions  neurons of cardiac ganglion signal ostia to close and initiate heart beat  as cardiomyocytes contract, decrease volume of heart chamber exerts pressure on fluids causing blood to squirt out of heart into circulatory system.  during diastole, heart relaxes and ligaments recoil causing volume to increase and lower pressure in which blood sucked through ostia  Vertebrate hearts: have 4 compartments, pericardium forms protective layer o Fish heart: 4 chambers arranged in series  Blood enters heart through sinus venosus, flows into atrium, then into muscular ventricle which pumps blood through bulbus arteriosus (in bony fish) or conus arteriosus (in elasmobranchs) o Amphibian heart: has 3 chambered heart with 2 artia and 1 ventricle  deoxygenated and oxygenated held separate by trabeculae (divisions) o Reptiles:  Non-crocodilian have 5 chambers (2 atria, 3 interconnected ventricles)  reptiles can distribute blood selectively between pulmonary and systemic circulation  can bypass either pulmonary or systemic circulation with a shunt (because are intermittent breathers)  Crocodilian: have completely divided ventricles and can shunt blood between them o Birds/Mammals: 4 unobstructed chambers (2 atria, 2 ventricles)  right ventricle pumps through pulmonary circuit (thus less forceful)  left ventricle pumps more forcefully through systemic circuit (which has high resistance) Cardiac Cycle 1. Ventricular Diastole: pressure in atria exceeds ventricular pressure and AV valves open as ventricles fill passively 2. Atrial systole: atrial contraction forces additional blood into ventricles 3. Ventricular systole (isovolumetric contraction): volume doesn’t change, but ventricular contraction pushes the AV valves closed and increase the pressure inside the ventricle 4. Ventricular systole (ventricular ejection): increased ventricular pressure forces the semilunar valves open and blood is ejected 5. Ventricular diastole: as ventricles relax, pressure in arteries exceed ventricular pressure, closing the semilunar valves Control of Contraction  vertebrate hearts are myogenic (not neurogenic) o the cardiomyocytes can produce spontaneous rhythmic depolarizations that initiate contraction o cardiomyocytes are electrically coupled via gap junctions so depolarization can spread to adjacent cells o cells with fastest intrinsic rhythm called ‘pace maker cells’ because they determine the contraction rate for entire heart  Pacemaker cells do not contract and have unstable resting membrane  Action potential of pacemaker cells o slow inward movement of Na+ (called ‘funny current’) causes slow depolarization o slow decrease in potassium movement contributes to slow depolarization of cell o when threshold reached, T-type voltage-gated Ca2+ channels open causing rapid depolarization (but less steep than neural action potential) o after 200 ms, Ca2+ channels begin to close o K+ channels open and cause repolarization of action potential of pacemaker cell  Nervous and endocrine control of rate of pacemaker potentials o norepinephrine and epinephrine can bind to beta-adrenergic receptors on pacemaker cells, stimulating a cAMP-mediated pathway to alter ion channels  funny channels and Ca2+ channels open, increasing influx of Na+ and Ca2+ which increase rate of depolarization of cell  increased depolarization increases frequency of action potential in pacemaker cell o acetylcholine (from parasympathetic) bind to muscarinic receptors on pacemaker cells; stimulate signal that increases K+ efflux thus making pacemaker hyperpolarize  thus takes pacemaker potential longer to reach threshold value, thus slows heart rate  Action potential of cardiomyocyte is different from pacemaker potentials o cardiomyocytes can also depolarize adjacent cells o also they have extended depolarization phase that creates a plateau face  caused when Na+ channel closes and L-type voltage-gated Ca2+ channels open  creates a longer refractory period  Electrocardiograph o P-wave: spread of depolarization through atria o QRS complex: result of ventricular depolarization and atrial repolarization o T-wave: caused by ventricular repolarization o Ventricular fibrillation: when ventricles do not contract in coordinated way  electronic defibrillator deliver intense pulse of current to body, causing cells of heart to depolarize and gives pacemaker cells of heart a chance to take over and start normal heartbeat  ineffective pumping of blood to tissues may result in oxygen deprivation and kill tissues  Heart rate: decreases called bradycardia, increases called tachycardia o nervous and endocrine systems can modulate stroke volume (by altering contractility) o norepinephrine/epinephrine increase stroke volume by activating protein kinases that result in 4 mechanisms to increase contractility  phosphorylation of L-type Ca2+ channels increases Ca2+ into cell in response to depolarization  phosphorylation of proteins in sarcoplasmic reticulum causes it to release more Ca2+ in response to action potential  phosphorylatin of myosin increases rate of myosin ATPase, increase rate of cross-bridge cycling and speed of contractions  phosphorylation of sarcoplasmic reticulum Ca2+ ATPase enhances Ca2+ reuptake, increases rate of relaxation o Frank-starling effect: the length-tension effect, when you experience increase end-diastolic volume (max volume during cardiac cycle), the ventricle pumps more forcefully and stroke volume increases  important effect to protect heart from abnormal increases in volume Regulation of Pressure and Flow (pg 384)  circulatory system must regulate distribution of flow to tissues, highly aerobically active tissues have greater demand for oxygen and require greater blood flow o changes in demand regulated by altering diameter (or resistance) of blood vessels to capillary beds  arterioles stretch/constrict to regulate blood flow to capillary beds o Myogenic autoregulation: smooth muscles surrounding arterioles are sensitive to stretch/contract o ie – Nitric oxide released by vascular smooth muscles help keep arterioles dilated (vasodilation)  nitric oxide activates enzyme that converts GMP to cGMP which triggers muscles to relax o Vasopressin promote vasoconstriction, ANP promote vasodilation  arteries also dampen pressure fluctuations,
More Less

Related notes for HMB302H1

Log In


Join OneClass

Access over 10 million pages of study
documents for 1.3 million courses.

Sign up

Join to view


By registering, I agree to the Terms and Privacy Policies
Already have an account?
Just a few more details

So we can recommend you notes for your school.

Reset Password

Please enter below the email address you registered with and we will send you a link to reset your password.

Add your courses

Get notes from the top students in your class.