Download Arteries

 Chapter 42
Circulation and Gas
Exchange
Label the heart vessels & valves
Trace the flow of blood beginning with return through the
Vena cava (list)
If you are only a couple of cell
layers thick or very flat—a simple
distribution system works just fine.
 Gastrovascular cavity
in cnidarians
 Highly branched
gastrovascular cavity
in flatworms
Circulatory Systems
 Complex animals
 2 types
 3 basic components:
1. circulatory fluid (blood)
2. set of tubes (blood vessels)
3. muscular pump (heart)
The 2 Types of Circulatory Systems:
 Open circulatory arthropods, mollusks
circulatory fluid directly bathes cells--exchange
hemolymph (blood & interstitial fluid) •pumped into sinuses
(spaces surrounding organs) through vessels
 Closed circulatory: blood confined to vessels;
earthworm, squid, vertebrates
Cardiovascular system
 vertebrates •
 blood-circulatory fluid- circulates within vessels
(arteries, veins, capillaries)
 Chemical exchange at capillaries
 Within organs:
 Arteries
arterioles
capillary beds
tissues – exchange
venules
veins
return blood to heart
 Arteries: carry blood AWAY from the heart
 Veins: return blood TO THE HEART
The Vertebrate Heart
 Atria: receive blood returning to the
heart
 Ventricles: pump blood out of the heart
Generalized Circulatory schemes
 Fish: 2-chambered heart (1 atrium & 1 ventricle); single circuit
of blood flow. Heart-to gills picks up O2, eliminates CO2--to
systemic capillaries—then back to heart.
 Disadvantage: low pressure from Gills
Generalized Circulatory schemes
 Amphibians: 3-chambered heart; 1 Ventricle, 2 Atria; 2 circuit
of blood flow- (double circulation)
1.pulmocutaneous (lungs and skin);
2.systemic (some mixing of O2-rich and O2-poor blood
occurs)
 Mammals, birds, crocodilians: 4-chambered heart; double
circulation; complete separation between oxygen-rich and
oxygen poor blood (2 ventricles)
 The mammalian heart
 located beneath
 consists mostly of cardiac muscle.
 Two atria:
 relatively thin walls
 collection chambers for blood returning to the heart.
 The ventricles have thicker walls and contract
much more strongly than the atria.
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
Fig. 42.5
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
Double
circulation
Advantage--Provides
vigorous flow of bloodblood pumped through
heart 2 TIMES
 From right ventricle to lungs
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via pulmonary arteries through
semilunar valve (pulmonary
circulation)
Capillary beds in lungs to left
atrium via pulmonary veins
Left atrium to left ventricle
(through atrioventricular valve)
to aorta
Aorta to coronary arteries;
then systemic circulation
Back to heart via two venae
cavae (superior and inferior);
right atrium
 Cardiac cycle: sequence
of filling and pumping
 Systole- contraction
 Diastole- relaxation
 Cardiac output: volume of
blood per minute
 Heart rate- number of
beats per minute
 Stroke volume- amount of
blood pumped with each
contraction
The mammalian
heart
Heart Valves
 Prevent backflow
 Keep blood moving in correct direction
 AV valves close at ventricular contraction
 Semilunar Valves: at the 2 arterial exits of
the heart
 forced open at ventricular contraction
(arteries stretch under this pressure)
 For a human at rest with a pulse of about
75 beat per minute, one complete
cardiac cycle takes about 0.8 sec.
(1) During the relaxation phase (atria and
ventricles in diastole) lasting about 0.4 sec,
blood returning from the large veins flows into
atria and ventricles.
(2) A brief period (about 0.1 sec) of atrial systole
forces all the remaining blood out of the atria
and into the ventricles.
(3) During the remaining 0.3 sec of the cycle,
ventricular systole pumps blood into the large
arteries.
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
 Cardiac output depends on two factors:
 1. the rate of contraction or heart rate (number of
beats per second)

and
 stroke volume, the amount of blood pumped by
the left ventricle in each contraction.
 The average stroke volume for a human is about 75 mL.
 Cardiac output can increase about fivefold during heavy
exercise.
 Heart rate can be measured indirectly by measuring
your pulse - the rhythmic stretching of arteries
caused by the pressure of blood pumped by the
ventricles.
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 A defect in one or more of the valves
causes a heart murmur, which may be
detectable as a hissing sound when a
stream of blood squirts backward through a
valve.
 born with
 damage to the valves by infection (rheumatic
fever)
 Most heart murmurs do not reduce the
efficiency of blood flow enough to warrant
surgery.
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 Continuity and control of the heartbeat.
 Each cell has its own intrinsic contraction
rhythm.
 Synchronized by the sinoatrial (SA) node, or
pacemaker
 which sets the rate and timing at which all cardiac
muscle cells contract.
 Located in the wall of the right atrium.
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
 The cardiac cycle is regulated by electrical
impulses that radiate throughout the heart.
 Cardiac muscle cells are electrically coupled
by intercalated disks between adjacent cells.
Fig. 42.7
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(1) The SA node generates electrical impulses
that spread rapidly (2) through the wall of the
atria, making them contract in unison.
Delayed by about 0.1 sec at the atrioventricular
(AV) node, the relay point to the ventricle,
allowing the atria to empty completely before
the ventricles contract.
(3) Specialized muscle fibers called bundle
branches and Purkinje fibers conduct the
signals to the apex of the heart and (4)
throughout the ventricular walls.
This stimulates the ventricles to contract from the
apex toward the atria, driving blood into the
large arteries.
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
 Impulses generated during the heart cycle
produce electrical currents that are
conducted through body fluids to the skin.
 Here, the currents can be detected by
electrodes and recorded as an
electrocardiogram (ECG or EKG).
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
 While the SA node sets the tempo for the
entire heart, it is influenced by a variety of
physiological cues.
 Two sets of nerves affect heart rate with one set
speeding up the pacemaker and the other set
slowing it down
 Heart rate is a compromise regulated by the opposing
actions of these two sets of nerves.
 hormones.
 For example, epinephrine from the adrenal glands
increases heart rate.
 temperature and with exercise.
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
5. Structure of arteries, veins,
and capillaries
 arteries and veins have three similar layers.
 On the outside, a layer of connective tissue with
elastic fibers allows the vessel to stretch and
recoil.
 A middle layer has smooth muscle and more
elastic fibers.
 Lining the lumen of all blood vessels, including
capillaries, is an endothelium, a single layer of
flattened cells that minimizes resistance to blood
flow.
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
 Structural &function
 Capillaries lack the two outer layers and their
very thin
Fig. 42.8
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
 Arteries have thicker middle and outer
layers than veins.
 strength to accommodate blood pumped
rapidly and at high pressure by the heart.
 Their elasticity (elastic recoil) helps maintain
blood pressure even when the heart relaxes.
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
 The thinner-walled veins convey blood
back to the heart at low velocity and
pressure.
 Blood flows mostly as a result of skeletal
muscle contractions when we move that
squeeze blood in veins.
 Within larger veins, flaps of tissues act as
one-way valves that allow blood to flow
only toward the heart.
Fig. 42.9
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
Blood
 Plasma: liquid matrix of blood in which cells are suspended (90%
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water)
Erythrocytes (RBCs): transport O2 via hemoglobin
Leukocytes (WBCs): defense and immunity
Platelets: clotting
Stem cells: pluripotent cells in the red marrow of bones
Blood clotting: fibrinogen (inactive)/ fibrin (active); hemophilia;
thrombus (clot)
Cardiovascular disease
 Cardiovascular disease (>50%
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of all deaths)
Heart attack- death of cardiac
tissue due to coronary blockage
Stroke- death of nervous tissue
in brain due to arterial blockage
Atherosclerosis: arterial plaques
deposits
Arteriosclerosis: plaque
hardening by calcium deposits
Hypertension: high blood
pressure
Hypercholesterolemia:
LDL, HDL
Gas exchange
 CO2 <---> O2
 Aquatic: •gills •ventilation
•countercurrent
exchange
 Terrestrial: •tracheal systems •lungs
Mammalian respiratory systems
 Larynx (upper part of
respiratory tract)
 Vocal cords (sound production)
 Trachea (windpipe)
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Bronchi (tube to lungs)
Bronchioles
Alveoli (air sacs)
Diaphragm (breathing muscle)
Breathing
 Positive pressure breathing: pushes air into lungs (frog)
 Negative pressure breathing: pulls air into lungs (mammals)
 Inhalation: diaphragm contraction; Exhalation: diaphragm
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relaxation
Tidal volume: amount of air inhaled and exhaled with each breath
(500ml)
Vital capacity: maximum tidal volume during forced breathing (4L)
Regulation: CO2 concentration in blood (medulla oblongata).
Detects blood pH changes
Respiratory pigments: gas
transport
 Respiratory Pigments
 Oxygen transport Hemocyanin: found in hemolymph
of arthropods and mollusks (Cu)
 Hemoglobin: vertebrates (Fe)
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Carbon dioxide transportBlood plasma (7%)
Hemoglobin (23%)
Bicarbonate ions (70%)
 Deep-diving air-breathers Myoglobin: oxygen storing protein
 Cooperative oxygen binding
 Diffusion of O2 in air greater
 Drop in pH lowers the affinity of hemoglobin
for O2
 Bohr Shift
The heartbeat
 Label the pictures below.
 Describe or list the steps in the Control of Heart Rhythm