BIOL 1011 Lecture Notes - Lecture 13: Heart Valve, Diastole, Systolic Geometry
Circulation and Gas Exchange
March 17, 2015
Why do we have circulatory systems?
Every cell must exchange oxygen and carbon dioxide. Diffusion is slow beyond
distances of 1mm.
2 Solutions:
1. Keep every cell in contact with external environment
2. Use a circulatory system
Jellyfish, flatworms and hydras expose all of their cells to the outside environment
to exchange gases.
Properties of Circulatory Systems:
1. Circulatory fluid
2. Interconnecting vessels
3. Muscle pump (usually a heart)
Two types of systems: open and closed.
Open Systems (molluscs, anthropods)
• Slightly inefficient
• Loses hemolymph in sinuses surrounding organs
Closed Systems (annelids, vertebrates)
• More efficient
• Heart is completely closed off with vessels
• Gases exchange within capillaries
Vertebrate Cardiovascular System:
• Arteries carry blood from heart to tissues
• Arteries branch off into small arterioles which then branch off into capillaries
• At the capillaries, gases and nutrients can exchange
• The capillaries join into venules which combine into larger veins
• The major veins carry blood from the tissues to the heart
Heart Chambers:
• Atrium (atria) – receive blood from veins
• Ventricles – pump blood to arteries
• Anything blue is deoxygenated blood
• Anything red is oxygenated blood
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In fish, there is a unidirectional single circulation system.
Incomplete Double Circulation:
Complete Double Circulation:
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Left ventricle is larger than right ventricle (has to pump blood to entire body not
just lungs).
Contraction – Cardiac Cycle
• Diastole: relaxation of the heart, filling of the atria or ventricles or both
• Systole: contraction of the heart, emptying of blood from atria or ventricles
• Valves prevent backflow and keep blood flowing unidirectional
(atrioventricular and semilunar)
How much blood does the heart pump?
• Cardiac output: volume of blood pumped per minute
• Heart rate: contractions (beats) per minute
• Stroke volume: volume of blood per contraction
* CO = HR (72bpm) x SV (70mL) = ~5L/min
Heart Rate Regulation
Each contraction is initialted by autorhythmic cell in the right atrium (sinonatrial
node aka pacemaker cells). They produce electrical signals similar to nerve cells.
Signals are spread rapidly through the heart.
External cues influence the activity of the sinoatrial node:
• Temperature
• Exercise
• Hormones
Fig. 42-8-3
Semilunar
valves
closed
0.4sec
AV
valves
open
Atrialand
ventricular
diastole
1
2
0.1sec
Atrialsystole;
ventricular
diastole
3
0.3sec
Semilunar
valves
open
AVvalves
closed
Ventricularsystole;
atrialdiastole
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Document Summary
Every cell must exchange oxygen and carbon dioxide. 2 solutions: keep every cell in contact with external environment, use a circulatory system. Jellyfish, flatworms and hydras expose all of their cells to the outside environment to exchange gases. Properties of circulatory systems: circulatory fluid, interconnecting vessels, muscle pump (usually a heart) Open systems (molluscs, anthropods: slightly inefficient, loses hemolymph in sinuses surrounding organs. Closed systems (annelids, vertebrates: more efficient, heart is completely closed off with vessels, gases exchange within capillaries. Heart chambers: atrium (atria) receive blood from veins, ventricles pump blood to arteries, anything blue is deoxygenated blood, anything red is oxygenated blood. In fish, there is a unidirectional single circulation system. How much blood does the heart pump: cardiac output: volume of blood pumped per minute, heart rate: contractions (beats) per minute, stroke volume: volume of blood per contraction. * co = hr (72bpm) x sv (70ml) = ~5l/min.
