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Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
IB Biology 2010/2011
Topic 6.2-Human Circulation & 6.4-Gas Exchange
RNS Science
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Circulation, Gas Exchange & Cellular Respiration
Organismal level
Cellular level
Circulatory system
Cellular respiration ATPEnergy-richmoleculesfrom food
Respiratorysurface
Respiratorymedium(air of water)
O2 CO2
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Overview: Trading with the Environment
• Every organism must exchange materials with its environment
– And this exchange ultimately occurs at the cellular level
• Transport systems
– Functionally connect the organs of exchange with the body cells
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Open and Closed Circulatory Systems• More complex animals
– Have one of two types of circulatory systems: open or closed
• Both of these types of systems have three basic components
– A circulatory fluid (blood)
– A set of tubes (blood vessels)
– A muscular pump (the heart)
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• Draw and label a diagram of the heart showing the four chambers, associated blood vessels, valves and the route of blood through the heart.
– Care should be taken to show the relative wall thickness of the four chambers.
• State that the coronary arteries supply heart muscle with oxygen and nutrients.
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
The Heart of the matter…… (sorry)
• 2 thin-walled atria and 2 thicker-walled ventricles (left ventricle the thickest wall)
• Large artery, smaller arteries, arterioles, capillary bed, venule, veins, large veins
• Pulmonary and Systemic Circulation
• Follow that RBC though the entire ‘double circulation’ pattern (one or two minutes)
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• The mammalian cardiovascular system
Pulmonary vein
Right atrium
Right ventricle
Posteriorvena cava Capillaries of
abdominal organsand hind limbs
Aorta
Left ventricle
Left atriumPulmonary vein
Pulmonaryartery
Capillariesof left lung
Capillaries ofhead and forelimbs
Anteriorvena cava
Pulmonaryartery
Capillariesof right lung
Aorta
Figure 42.5
1
10
11
5
4
6
2
9
33
7
8
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
The Mammalian Heart: A Closer Look
– http://www.nhlbi.nih.gov/health/dci/Diseases/hhw/hhw_pumping.html
– Provides a better understanding of how double circulation works
Figure 42.6
Aorta
Pulmonaryveins
Semilunarvalve
Atrioventricularvalve
Left ventricleRight ventricle
Anterior vena cava
Pulmonary artery
Semilunarvalve
Atrioventricularvalve
Posterior vena cava
Pulmonaryveins
Right atrium
Pulmonaryartery
Leftatrium
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• Explain the action of the heart in terms of collecting blood, pumping blood, and opening and closing of valves.
• A basic understanding is required, limited to the collection of blood by the atria, which is then pumped out by the ventricles into the arteries.
– The direction of flow is controlled by atrio-ventricular and semilunar valves.
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Mammalian Circulation: The Pathway
• Heart valves dictate a one-way flow of blood through the heart
• Blood begins its flow with the right ventricle pumping blood to the lungs
• In the lung the blood loads O2 and unloads CO2
• Oxygen-rich blood from the lungs enters the heart at the left atrium and is pumped to the body tissues by the left ventricle
• Blood returns to the heart through the right atrium
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• The heart contracts and relaxes
– In a rhythmic cycle called the cardiac cycle
• The contraction, or pumping, phase of the cycle
– Is called systole
• The relaxation, or filling, phase of the cycle
– Is called diastole
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• The cardiac cycle
Figure 42.7
Semilunarvalvesclosed
AV valvesopen
AV valvesclosed
Semilunarvalvesopen
Atrial and ventricular diastole
1
Atrial systole; ventricular diastole
2
Ventricular systole; atrial diastole
3
0.1 sec
0.3 sec0.4 sec
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• The heart rate, also called the pulse
– Is the number of beats per minute
• The cardiac output
– Is the volume of blood pumped into the systemic circulation per minute
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• Outline the control of the heartbeat in terms of myogenic muscle contraction, the role of the pacemaker, nerves, the medulla of the brain and epinephrine (adrenaline).
• Histology of the heart muscle, names of nerves or transmitter substances are not required.
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Control of Heart Rate……
• Cardiac muscle spontaneously contracts and relaxes without nervous system control = myogenic muscle contraction (this must be controlled to keep contractions unified)
• Sinoatrial node (SA) in the right atrium – sends out a signal to initiate contraction in the atria
• Atriventricular (AV) node receives impulse from SA node and sends an impulse for the ventricles to contract
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
More on Maintaining the Heart’s Rhythmic Beat…• Some cardiac muscle cells are self-excitable
– Meaning they contract without any signal from the nervous system
• A region of the heart called the sinoatrial (SA) node, or pacemaker
– Sets the rate and timing at which all cardiac muscle cells contract
• Impulses from the SA node
– Travel to the atrioventricular (AV) node
• At the AV node, the impulses are delayed
– And then travel to the Purkinje fibers that make the ventricles contract
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• The control of heart rhythm
Figure 42.8
SA node(pacemaker)
AV node Bundlebranches
Heartapex
Purkinjefibers
2 Signals are delayedat AV node.
1 Pacemaker generates wave of signals to contract.
3 Signals passto heart apex.
4 Signals spreadThroughoutventricles.
ECG
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• The pacemaker is influenced by nerves, hormones, and exercise:
– Exercise causes carbon dioxide levels to rise, which is sensed by the medulla area of the brainstem
– The medulla sends a signal through a cranial nerve (the cardiac nerve) to the SA node to increase heart rate
– As carbon dioxide level decreases with less activity, the medulla sends a signal through the vagus cranial nerve to the SA to slow the rate
– Adrenalin from the adrenal gland during ‘stress’ can also signal the SA node to pick up the heart rate
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Blood Vessel Structure and Function
• Explain the relationship between the structure and function of arteries, capillaries and veins:
• The “infrastructure” of the circulatory system is its network of blood vessels
• Structural differences in arteries, veins, and capillaries correlate with their different functions
• Arteries have thicker walls to accommodate the high pressure of blood pumped from the heart
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• All blood vessels
– Are built of similar tissues
– Have three similar layers
Figure 42.9
Artery Vein
100 µm
Artery Vein
ArterioleVenule
Connectivetissue
Smoothmuscle
Endothelium
Connectivetissue
Smoothmuscle
EndotheliumValve
Endothelium
Basementmembrane
Capillary
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• In the thinner-walled veins
– Blood flows back to the heart mainly as a result of muscle action
Figure 42.10
Direction of blood flowin vein (toward heart)
Valve (open)
Skeletal muscle
Valve (closed)
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Quick Comparison of Arteries, Capillaries, & Veins
Artery Capillary Vein
Carries blood away from heart
Connects arterioles and venules
Carries blood toward the heart
Thick walled Wall is 1 cell thick Thin walled
No exchanges All exchanges occur No exchanges
No internal valves No internal valves Have internal valves
Internal pressure high Internal pressure low Internal pressure low
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Blood Pressure
• Blood pressure
– Is the hydrostatic pressure that blood exerts against the wall of a vessel
• Systolic pressure
– Is the pressure in the arteries during ventricular systole
– Is the highest pressure in the arteries
• Diastolic pressure
– Is the pressure in the arteries during diastole
– Is lower than systolic pressure
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• Blood pressure
– Can be easily measured in humans
Figure 42.12
Artery
Rubber cuffinflatedwith air
Arteryclosed
120 120
Pressurein cuff above 120
Pressurein cuff below 120
Pressurein cuff below 70
Sounds audible instethoscope
Sounds stop
Blood pressurereading: 120/70
A typical blood pressure reading for a 20-year-oldis 120/70. The units for these numbers are mm of mercury (Hg); a blood pressure of 120 is a force that can support a column of mercury 120 mm high.
1
A sphygmomanometer, an inflatable cuff attached to apressure gauge, measures blood pressure in an artery.The cuff is wrapped around the upper arm and inflated until the pressure closes the artery, so that no blood flows past the cuff. When this occurs, the pressure exerted by the cuff exceeds the pressure in the artery.
2 A stethoscope is used to listen for sounds of blood flow below the cuff. If the artery is closed, there is no pulse below the cuff. The cuff is gradually deflated until blood begins to flow into the forearm, and sounds from blood pulsing into the artery below the cuff can be heard with the stethoscope. This occurs when the blood pressure is greater than the pressure exerted by the cuff. The pressure at this point is the systolic pressure.
3
The cuff is loosened further until the blood flows freely through the artery and the sounds below the cuff disappear. The pressure at this point is the diastolic pressure remaining in the artery when the heart is relaxed.
4
70
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• Blood pressure is determined partly by cardiac output
– And partly by peripheral resistance due to variable constriction of the arterioles
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Capillary Function
• Capillaries in major organs are usually filled to capacity
– But in many other sites, the blood supply varies
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• Two mechanisms
– Regulate the distribution of blood in capillary beds
• In one mechanism
– Contraction of the smooth muscle layer in the wall of an arteriole constricts the vessel
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• In a second mechanism
– Precapillary sphincters control the flow of blood between arterioles and venules
Figure 42.13 a–c
Precapillary sphincters Thoroughfarechannel
ArterioleCapillaries
Venule(a) Sphincters relaxed
(b) Sphincters contractedVenuleArteriole
(c) Capillaries and larger vessels (SEM)
20 m
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• The critical exchange of substances between the blood and interstitial fluid
– Takes place across the thin endothelial walls of the capillaries
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• State that blood is composed of plasma, erythrocytes, leucocytes (phagocytes and lymphocytes) and platelets.
• State that the following are transported by the blood: nutrients, oxygen, carbon dioxide, hormones, antibodies, urea and heat.
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Blood Composition and Function
• Blood consists of several kinds of cells
– Suspended in a liquid matrix called plasma
• The cellular elements (hematocrit)
– Occupy about 45% of the volume of blood
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Plasma
• Blood plasma is about 90% water
• Among its many solutes are
– Inorganic salts in the form of dissolved ions, sometimes referred to as electrolytes
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• The composition of mammalian plasmaPlasma 55%
Constituent Major functions
Water Solvent forcarrying othersubstances
SodiumPotassiumCalciumMagnesiumChlorideBicarbonate
Osmotic balancepH buffering, andregulation of membranepermeability
Albumin
Fibrinogen
Immunoglobulins(antibodies)
Plasma proteins
Ions (blood electrolytes)
Osmotic balance,pH buffering
Substances transported by bloodNutrients (such as glucose, fatty acids, vitamins)Waste products of metabolismRespiratory gases (O2 and CO2)Hormones
Defense
Figure 42.15
Separatedbloodelements
Clotting
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• Another important class of solutes is the plasma proteins
– Which influence blood pH, osmotic pressure, and viscosity
• Various types of plasma proteins
– Function in lipid transport, immunity, and blood clotting
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Cellular Elements
• Suspended in blood plasma are two classes of cells
– Red blood cells, which transport oxygen
– White blood cells, which function in defense
• A third cellular element, platelets
– Are fragments of cells that are involved in clotting
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Figure 42.15
Cellular elements 45%
Cell type Numberper L (mm3) of blood
Functions
Erythrocytes(red blood cells) 5–6 million Transport oxygen
and help transportcarbon dioxide
Leukocytes(white blood cells)
5,000–10,000 Defense andimmunity
Eosinophil
Basophil
Platelets
NeutrophilMonocyte
Lymphocyte
250,000400,000
Blood clotting
• The cellular elements of mammalian blood
Separatedbloodelements
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Erythrocytes
• Red blood cells, or erythrocytes
– Are by far the most numerous blood cells
– Transport oxygen throughout the body
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Leukocytes & Platelets
• The blood contains five major types of white blood cells, or leukocytes
– Monocytes, neutrophils, basophils, eosinophils, and lymphocytes, which function in defense by phagocytizing bacteria and debris or by producing antibodies
• Platelets function in blood clotting
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Bloody Summary…..• Components of Blood
• Transport by Blood
Component Description
plasma Liquid portion of blood
erythrocytes Red blood cells(carry oxygen and carbon dioxide)
leukocytes White blood cells (phagocytes and lymphocytes)
platelets Cell fragments (assist in blood clotting
What is transported What it is or does
Nutrients Glucose, amino acids, etc
Oxygen Reactant for cell respiration
Carbon dioxide Waste product of cell respiration
Hormones Transported from gland to target cell
Antibodies Protein molecules involved in immunity
Urea Nitrogenous waste (filtered out of blood by kidneys)
Heat Skin arterioles – vasodilation or vasoconstriction
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Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Gas Exchange
• Occurs across specialized respiratory surfaces
• Supplies oxygen for cellular respiration and disposes of carbon dioxide
Organismal level
Cellular level
Circulatory system
Cellular respiration ATPEnergy-richmoleculesfrom food
Respiratorysurface
Respiratorymedium(air of water)
O2 CO2
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Gas Exchange
• Distinguish between ventilation, gas exchange and cell respiration.
– Ventilation – drawing air in and out of the lungs
– Gas Exchange – occurs at capillary beds
– Cell Respiration – see earlier stuff on mitochondrion
•
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• Explain the need for a ventilation system.
– A ventilation system is needed to maintain high concentration gradients in the alveoli.
– Humans are too thick….
• In mammals, air inhaled through the nostrils
– Passes through the pharynx into the trachea, bronchi, bronchioles, and dead-end alveoli, where gas exchange occurs
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• Concept 42.6: Breathing ventilates the lungs
• The process that ventilates the lungs is breathing
– The alternate inhalation and exhalation of air
– Explain the mechanism of ventilation of the lungs in terms of volume and pressure changes caused by the intercostal muscles, the diaphragm and abdominal muscles.
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Tidal Ventilation in Humans
• Lung volume increases
– As the rib muscles (external intercostals) and diaphragm contract
• Lung Volume decreases due to
either
– Relaxation of diaphragm and external intercostals and the natural elasticity of lung tissue
or– Forced out by contraction of the internal
intercostals (and abdominal muscles)
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• Draw and label a diagram of the ventilation system, including trachea, lungs, bronchi, bronchioles and alveoli.
– Students should draw the alveoli in an inset diagram at a higher magnification.
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Mammalian Respiratory Systems: A Closer Look
• A system of branching ducts
– Conveys air to the lungsBranch from the pulmonary vein (oxygen-rich blood) Terminal bronchiole
Branch from thepulmonaryartery(oxygen-poor blood)
Alveoli
Colorized SEMSEM
50 µ
m
50 µ
m
Heart
Left lung
Nasalcavity
Pharynx
Larynx
Diaphragm
Bronchiole
Bronchus
Right lung
Trachea
Esophagus
Figure 42.23
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• Describe the features of alveoli that adapt them to gas exchange.
– This should include a large total surface area,
– a wall consisting of a single layer of flattened cells,
– a film of moisture and a dense network of capillaries.
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Inhaled air Exhaled air
160 0.2O2 CO2
O2 CO2
O2 CO2
O2 CO2 O2 CO2
O2 CO2 O2 CO2
O2 CO2
40 45
40 45
100 40
104 40
104 40
120 27
CO2O2
Alveolarepithelialcells
Pulmonaryarteries
Blood enteringalveolar
capillaries
Blood leavingtissue
capillaries
Blood enteringtissue
capillaries
Blood leaving
alveolar capillaries
CO2O2
Tissue capillaries
Heart
Alveolar capillaries
of lung
<40 >45
Tissue cells
Pulmonaryveins
Systemic arteriesSystemic
veinsO2
CO2
O2
CO 2
Alveolar spaces
12
43
Figure 42.27
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings