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Lecture 13

Lecture 13 - The Heart, Blood and Oxygen Association Curves

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Western University
Biology 2601A/B
Graeme Taylor

LECTURE 13: THE HEART, BLOOD AND OXYGEN ASSOCIATION CURVES Closed Circulatory System  Heart o A discrete pumping structure o Drive the flow of blood o Single chambered o Two or more chambers o Multiple hearts (accessory hearts) o Muscle tissue of a heart, is known as myocardium o Highly compact and dense o Systole o Diastole o Most important aspect is the volume of blood it pumps per unit of time o Cardiac output is the product of the heart rate and the stroke volume (cardiac output = heart rate x stroke volume)  Humans: heart rate = 60-180 beats/min and stroke volume = 70-120  Mouse: 600 beats per minute - has an allometric relationship with its aerobic capacity - demand on the tissue is much greater so in order to compensate, it has a high heart rate (in comparison to a whale - 6 beats per minute)  Coronary circulation of human heart  Highly resistant to fatigue and loaded with mitochondria A Teleost Heart  Heart of a fish – single-chambered  Pockets are perfused with blood and oxygenated – not an effective system  Bulbus arteriosus – damps pressure oscillations, is elastic  Spongy myocardium – this is how the heart obtains oxygen Fish Circulatory System  As deoxygenated blood from the body enters via the sinus venosus into the atrium, which then fills the ventricle by the way of weak muscular contractions  In the ventricle, the blood encounters spongy myocardium, which contains internal spaces whereby oxygen can diffuse and oxygenate the blood adjacent  Ventricle pumps recently oxygenated blood via bulbus arteriosus to the rest of the body  Physiological problems associated with teleost heart include: o Loss of pressure in oxygenating blood across the gills (resulting in low flow rate) o Heart is thus unable to receive freshly oxygenated blood (resulting in lower metabolic activity)  This pressure difference will vary among fish species (active fish vs. non-active fish) High Performance Fish Hearts  Deoxygenated blood perfusing spongy myocardium is a limiting factor for fish o As it is circulated throughout the body, it is depleted of oxygen  Salmonids, tuna, sharks have a ‘hybrid heart’ – needed in order to support their energetic lifestyles as they are high-performance fish  Allows coronary veins to deliver freshly oxygenated blood from the gills The Heart and Major Arteries Veins  Muscular, elastic thick walls (smooth muscle  Low pressure and elastin)  Have a system of one-way valves  Pressure of 10-20 kPa  Much thinner-walled than arteries  Elastic – dampens pressure differences an sto
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