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Cardiovascular System -Heart AND Blood Vessels function together -Bulk Transport vs. Diffusion -Laws of Chemistry and Physics set limits -The way evolution builds it is NOT the way an engineer would build it Cardiovascular Essential Questions • What are the functions of the CV system? • What are the different types of CV systems (open; closed)? • Why are there 2, 3 and 4 chambered hearts? • How does the body monitor and adjust CV function? Surface area to volume ratio (Large surface area needed wherever diffusion is utilized) Heart, bronchi and some of the arteries Arteries of the systemic circulatory system (torso) Arteries of the neck and brain Functions of the Cardiovascular System There is much more blood flowing to the rabbit’s ears than is needed to support that amount of tissue. Whenever you see a disproportionately large amount of blood flowing to a region you know there must be more going on than just delivery of nutrients. Functions of the Cardiovascular System • • • • • • Deliver Nutrients (O2, glucose, fatty acids, water*) Remove Wastes (CO2, nitrogen compounds, water*) Heat/Cool (deliver or remove heat) Deliver Hormones (epinephrine, cortisol) Movement (spider jump) Certain aspects of reproduction (erection) Open vs. Closed Spider Jump Leg extension in spiders involves pumping of fluid into legs to “inflate” them They do have muscles to flex their legs. Types of Closed CV Systems Two chambers (one ventricle*) Three chambers (one ventricle*) Four chambers (two ventricles*) *Ventricles are responsible for doing all the work Dual Circulation Dual Pump Systemic *to body *high oxygen in arteries Pulmonary *to lungs *low Oxygen in arteries Left more muscular Does more work Electrical Activity Coordinates Heart Beat • Pacemaker cells set Heart Rate • Sympathetic Activation – Speeds up rate – Strengthens contraction of muscle • Parasympathetic Activation – Slows rate – Weakens contraction Physics of Blood Flow • CV system must provide blood flow BUT… • It must also provide pressure Blood Pressures and Posture Density of blood is similar to density of H2O therefore similar changes in pressure with posture 1 mmHg = 13.5 mm H2O (0.53 inches H2O) 44mmHg = 594mm H2O (23 inches H2O) ~23in What about other creatures? 100 mmHg What is the blood pressure in the head of a giraffe? 260 mmHg 420 mmHg 14 ft What about creatures that lie flat? Ohm’s Law • • • • V=IR Pressure = Flow x Resistance P = Cardiac Output x Total Peripheral Resistance C.O. = Heart Rate x Stroke Volume • P = (H.R. x S.V.) x TPR Blood Vessels Blood Vessels Blood Pressure in CV system Need pressure for filtration Where is the blood? Where is the blood? Do we have more blood than we need? • Veins of the systemic circulation act as a reservoir where blood is allowed to pool under resting conditions. • When more Pressure and C.O. is needed, not only does the heart beat faster and stronger, the veins squeeze on this reservoir to push more blood back to the heart. • Veins are now aqueducts rather than reservoir Nervous System Control of Cardiovascular System HEART 1. Heart Rate Symp↑; Parasymp ↓ 2. Strength of Heart contraction Symp↑; Parasymp ↓ (Both 1 & 2 ↑ ↓ cardiac output – more/less flow) Blood Vessels 1. Resistance in arterioles Symp↑ (↑ Pressure & shunt blood away from some tissues & towards other tissues) 2. “Squeezing” of veins Symp↑ (↑ cardiac output by ↑ effective blood volume by pushing more blood back to heart) Symp also innervates arterioles and veins How does the brain monitor Cardiovascular System Function? • Pressure sensing neurons in the walls of the carotid artery) monitor pressure in this blood vessel and send signals to the brainstem which controls heart and blood vessels • There are other pressure sensing neurons in upper chest (aortic arch) as well • Key point - pressure is measured in vessels feeding the brain. CV System Design