Transcript Blood Pressure

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Coverings of the heart
 Enclosed in a layered pericardium
 Pericardial space between layers is fluid
filled
Wall of heart
 Endocardium – inner layer
 Myocardium – middle; mostly cardiac
muscles
 Epicardium (visceral pericardium) – outer
layer
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Heart Chambers, Valves & Blood Flow
 Heart is divided into 4 chambers – 2 atria, 2
ventricles
 R. chambers and valves – O2 poor blood
 R. atrium receives blood from superior &
inferior vena cava & coronary sinus
 Blood passes through tricuspid valve to R.
ventricle
 Blood passes through pulmonary
semilunar valve to L. & R. pulmonary
arteries ***only arteries to carry O2 poor
blood***
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Heart Chambers, Valves & Blood Flow
 L. chambers and valves – O 2 rich
 Blood returns from lungs via L. & R. pulmonary
veins ***only veins to carry O2 rich blood***
 O2 rich blood dumps into L. atrium
 Blood passes through bicuspid valve into L.
ventricle
 Blood passes through aortic semilunar valve to
aorta
 Distributed to the rest of body (systemic
circulation)
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http://www.youtube.com/watch?v=mH0QT
WzU-xI (blood flow through the heart)
http://vimeo.com/8321006 (animation - blood
flow)
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Cardiac Cycle
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Pressure within chambers rises & falls in repeated
cycles
Contraction of heart – systole Relaxation of heart –
diastole
When atria are relaxes (atrial diastole) blood flows
into them from veins (about 70% of blood flows
directly into ventricles)
When atria contract (atrial systole) the remaining
30% of blood flows into ventricles
As ventricles contract (ventricular systole)
bicuspid/tricuspid valves are pressed closed; blood
flows either to lungs or body
Stroke volume = volume of blood ejected from
ventricles
http://www.youtube.com/watch?v=jLTdgrhpDCg
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Heart Sounds
 Described as lub-dub
 Due to the vibrations produced by the blood
& valve movements
 Lub – occurs as A-V valves are
closing/ventricles contract
 Dub – occurs as semilunar valves are
closing/ventricles relax
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http://www.youtube.com/watch?v=te_SY3MeWys
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Cardiac Conduction System – Fig. 12-7
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Composed of specialized cardiac muscle tissue and
functions to initiate and conduct depolarization
waves through the myocardium
Signal is initiated by S-A node located in upper part
of R. atrium (known as the pace maker of the heart).
 Ability to excite themselves
 Impulses spread into surrounding myocardium
 Atria contract
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Cardiac Conduction System – Fig. 12-7
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Impulses travel slowly from S-A node (so atria have
time to contract) to A-V node located in lower part of
R. atrium
 Impulses now travel quickly to A-V bundle (bundle of
His) and then to Purkinje fibers
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Ventricles contract – muscle fibers in ventricular
walls are arranged in whorls that “wring” blood out
of ventricles
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Regulation of the Cardiac Cycle
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Heartbeat is affected by physical exercise, body
temp. and concentration of various ions
Parasympathetic impulses cause a decrease in heart
rate
Sympathetic impulses cause an increase in heart rate
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Arteries & Arterioles
 Adapted to carry relatively high pressure
blood AWAY from the heart
 Arterioles are branches of arteries
 Walls of arteries consist of layers of
endothelium, elastic membrane, smooth
muscle, and connective tissue ***walls of
arteries are thicker than walls of veins or
capillaries***
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Capillaries – form connections between
arterioles & venules
 Consist of a single layer of cells that forms a
semipermeable membrane
 Capillary density varies directly with tissue
metabolic rates
 Muscle & nerve – rich supply
 Cartilaginous, epidermis, cornea (low
metabolic rates) lack capillaries
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Capillaries – form connections between
arterioles & venules
 Capillary flow is regulated by opening &
closing of precapillary sphincters
 Open when cells are low in O2
 Close when cellular needs are met
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Capillaries – form connections between arterioles &
venules
 Gasses, nutrients, and metabolic by-products are
exchanged between capillary blood & tissue fluid
 Diffusion provides the most important means of
transport
 Filtration due to the hydrostatic pressure of blood
causes outward movement of fluid at the arterial
end of capillary
 Osmosis causes a net inward movement of fluid at
the venule end of a capillary
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Capillaries – form connections between
arterioles & venules
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Capillaries – form connections between
arterioles & venules
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Veins & venules
 Venules continue from capillaries and merge
to form veins
 Veins carry blood TOWARD the heart
 Contain valves to keep blood moving toward
the heart
 Venous walls are similar to arterial walls, but
are thinner and contain less muscle and
elastic tissue.
http://www.youtube.com/watch?v=HNuPW
dfjDoc
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Blood pressure is the force exerted by blood
against the insides of the blood vessels – Fig.
12-16 (also see – Clinical Application pg. 327)
http://www.youtube.com/watch?v=0L3hVPLlC4 (how to take blood pressure)
Arterial blood pressure
 Produced primarily be heart action; rises &
falls with phases of the cardiac cycle
 Systolic pressure occurs when the ventricles
contract; diastolic pressure occurs when the
ventricles relax
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Factors that influence arterial blood pressure
 Blood Volume
 An increase in volume causes an increase in
pressure
 A decrease in volume causes a decrease in
pressure
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Factors that influence arterial blood pressure
 Heart Action
 Volume of blood discharged from L. ventricle with
each contraction is called stroke volume (70ml –
75ml)
 Cardiac output = volume discharged in 1 minute
 Cardiac output = stroke volume x heart rate
(ex. 75ml x 70 beats/min. = 5250 ml/min)
 If stroke volume increases & heart rate stays the
same the cardiac output increases causing an
increase in blood pressure
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Factors that influence arterial blood pressure
 Peripheral Resistance – friction between the
blood and the walls of the blood vessels
 An increase in PR causes an increase in bp
 A decrease in PR causes a decrease in bp
 Viscosity – physical property – thickness
 An increase in viscosity causes an increase
in bp
 A decrease in viscosity causes a decrease in
bp
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Control of Blood Pressure – heart rate is
regulated by different portions of medulla
oblongata
Venous Blood Flow
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Not a direct result of heart action; it depends on
skeletal muscle contraction, breathing movements,
and venoconstriction
Many veins contain flaplike valves that prevent
blood from backing up
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Central Venous Pressure – pressure in the R.
atrium
 Influenced by factors that alter flow of blood
into R. atrium
 Ex. – A weak heart causes an increase in
pressure in R. atrium which causes the flow
of blood to slow which causes pressure to
increase in peripheral veins
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Pulmonary Circulation
 Composed of vessels that carry blood from R.
ventricle to lungs and back to l. atrium
 Pulmonary capillaries contain lower pressure
than systemic capillaries (R. ventricle
contracts with less force than L. ventricle
 Exchange of oxygen and carbon dioxide;
tightly joined epithelial cells of alveoli
prevent most substance from entering alveoli
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Pulmonary Circulation
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Systemic Circulation
http://www.youtube.com/watch?v=0jznS5psypI
 Vessels that carry blood from L. ventricle to body
cells and back to R. atrium
 Includes aorta & branches & system of veins
 Hepatic portal – the route of blood flow through
the liver (fig. 12-14); blood passes through 2
capillary beds before returning to the heart
 Renal circulation – the route of blood through
kidneys (fig. 17-3 pg. 443); blood passes through 2
capillary beds before returning to the heart
 Coronary Circulation – The delivery of oxygen &
nutrients and the removal of carbon dioxide & wastes
from cardiac muscle tissue
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Hepatic Portal Circulation
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Renal Circulation
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Coronary
Circulation
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Blood is carried between the placenta and the fetus by
umbilical vessels
Fetal blood carries more O2 than maternal blood
Blood enters fetus through umbilical vein (O2 rich) and
partially bypasses the liver by means of the ductus
venosus
Blood enters R. atrium & partially bypasses the lungs
by means of the foramen ovale
Blood entering the pulmonary trunk partially bypasses
the lungs by means of the ductus arteriosus
Blood enters umbilical arteries from the internal iliac
arteries (O2 poor)
http://www.youtu
be.com/watch?v=
OV8wtPYGE-I
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http://www.mhhe.com/biosci/genbio/virtual
_labs_2K8/labs/BL_14/index.html (Virtual
Blood Pressure Lab)