Download Chapter 14 Heart: Cardiovascular Physiology

Chapter 14
Heart: Cardiovascular Physiology
Exam 3 will be on Monday November 21
Will cover chapters 11, 12, 13, 14
May cover more, depends on how far we get
Heart: Cardiovascular Physiology
Cardiovascular system is a series of tubes (blood
vessels) filled with fluid (blood) and connected to a
pump (the heart)
Pressure generated by the heart continuously moves
blood through the system
Blood picks up oxygen at the lungs and expels carbon
dioxide
Blood circulates to all the body cells, bringing oxygen
and removing waste products
Table 14-1
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Arteries
– Carry blood away from the heart
– Usually carry oxygenated blood
• Exception: pulmonary arteries carry deoxygenated blood to the lungs
– Shown in red on the diagrams
Veins
– Carry deoxygenated blood to the heart
• Exception: pulmonary veins carry re-oxygenated
blood back to the heart
– Shown in blue on the diagrams
Systemic Circulation
– Heart (left ventricle) to body tissues then back to
the heart
Pulmonary Circulation
– Right ventricle to lungs then back to heart (left
atrium)
Hepatic Portal Circulation
– Digestive tract to liver via the hepatic portal vein.
This carries the digested nutrients directly to the
liver for processing
Portal Systems
Definition:
– Two capillary beds directly connected by a set of
blood vessels
Other body portal systems:
– Kidney portal system
– Hypothalamic-hypophyseal portal system
Figure 14-1
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Figure 14-7c
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Figure 14-7a
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Figure 14-7g
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Figure 14-7b
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Figure 14-7d
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Heart Structure
Learn the following diagrams (if you don't already
know them)
Know, for the exam, pericardium, heart structures
(including valves, atria, ventricles, septum), arteries
and veins attached to the heart (including the coronary
arteries—not shown on the diagrams), and the
circulation of blood through the heart
See Table 14-2 on page 478 for heart structures and
major blood vessels
Figure 14-7e
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Figure 14-7f
Atria, ventricles,
veins, arteries
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Table 14-2
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Figure 14-7g
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Coronary Arteries and Veins
Located in shallow grooves on the surface of the heart
Supply blood to the heart muscle
If any of these get blocked, can cause a myocardial
infarction (heart attack)
If the blood flow is blocked, then the heart cells that
the artery supplies start to die
Coronary Arteries and Veins
Heart: Fibrous “Skeleton”
(fig. 14-9a, p. 480)
Four fibrous connective tissue rings surround the four
heart valves
Functions:
1. Separates atria from ventricles
2. Provides attachment for valve cusps and
myocardium (all heart muscle originate and insert on
it). This arrangement pulls the heart base and apex
together when the ventricles contract
Heart: Fibrous “Skeleton”
(fig. 14-9a, p. 480)
3. Helps keep AV and semilunar valves open, but
inhibits over distension of these valves
4. Forms an electrical insulator separating the
electrical impulses of the atria and ventricles, so that
they contract independently
Heart Valves
One-way flow through the heart, ensured by 2 sets of
heart valves
Atrioventricular (AV) valves
– Located between the atria and ventricles
– Tricuspid valve (has 3 flaps)
• Between R. atrium and R. ventricle
– Bicuspid valve (has 2 flaps)
• Between L. atrium and L. ventricle
• Also called mitral valve (looks like a bishop's
hat)
Figure 14-9a
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Figure 14-9c
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Chordae Tendinae
– Collagenous tendons
– Attached to the flaps of the AV valve on the
ventricular side
– At opposite end, they are attached to papillary
muscles
Papillary Muscles
– Mound-like extensions of ventricular muscle
– Provide stability for the chordae tendinae
– These muscles do not actively pull on the valve
flaps
– The AV valves move passively, respond to flowing
blood pressing on them
Chordae Tendinae and Papillary Muscles
When a ventricle contracts, blood pushes against the
bottom side of its AV valve and forces it upward into a
closed position
Chordae tendinae prevent the valve from being
pushed into the atrium during contraction
Prolapse:
– If the chordae tendinae fail and the valve is
pushed into the atrium
Figure 14-9d
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Figure 14-9b
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Heart Valves
Semilunar valves
– Separate the ventricles from the major arteries
– Look like “half-moon” shapes
– Each made of 3 “cuplike leaflets” that snap shut to
prevent backflow of blood (back into the ventricles)
– Don't need connective tendons like the AV valves
– Aortic semilunar valve
• Located between L. ventricle and aorta
– Pulmonary semilunar valve
• Located between R. ventricle and pulmonary
trunk
Figure 14-9c
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Figure 14-9a
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Blood Flow Through the Heart
Right Atrium
– Deoxygenated blood enterrs R. Atrium from the
superior and inferior vena cavae
– R. Atrium contracts, sends blood through the
tricuspid valve and into the R. Ventricle
Right Ventricle
– R. Ventricle contracts, sends blood through the
Pulmonary semilunar valve into the pulmonary
artery
– Pulmonary Artery takes blood to lungs
Figure 14-7g
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Blood Flow Through the Heart
Left Atrium
– Pulmonary veins bring freshly oxygenated blood
from the lungs back to the L. Atrium
– L. Atrium contracts, sends blood through the mitral
valve into the L. Ventricle
Left Ventricle
– Largest and most powerful of the four heart
chambers
– L. Ventricle contracts, sends blood through the
aortic semilunar valve and into the aorta
– Aorta distributes blood to the entire body
Figure 14-7g
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Figure 14-9d
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Figure 14-9b
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Figure 14-7h
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Cardiac Muscle (Myocardium)
Most of the heart is composed of cardiac muscle
Most cardiac muscle is contractile
Approximately 1% of cardiac muscle cells are
specialized to spontaneously generate action
potentials
Heart muscle is myogenic: the contraction signal
originates within the heart itself, doesn't need external
input to keep beating
Cardiac Muscle (Myocardium)
Pacemaker or autorhythmic cells
– Specialized myocarial cells
– These set the rate of the heartbeat
Pacemaker cells are anatomicall distinct from other
myocardium
– Smaller than the other cells
– Contain few contractile fibers
– Lack organized sarcomeres
– Don't contribute much to heart contraction
Figure 14-10
Cardiac muscle
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Figure 14-10a
Spiral arrangement of
ventricular cardiac muscle
Allows ventricular contraction
to squeeze blood upward
from the heart apex
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Myocardium or Cardiac Muscle
Differs in significant ways from skeletal muscle
Shares some similarities with smooth muscle
1. Cardiac muscle fibers much smaller than skeletal
muscle fibers and have a single nucleus per fiber
3. Individual cardiac muscle cells branch and join
(end-to-end) with neighboring cells. Intercalated disks
form the cell junctions
Figure 14-10b
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Intercalated disks are interdigitated membranes
consisting of desmosomes and gap junctions
Desmosomes
– Strong connections, tie adjacent cells together
– Allow force created in one cell to be transferred to
the adjacent cell
Gap Junctions
– Electrically connect cardiac muscle cells
– Allow waves of depolarization to spread rapidly
from cell to cell
– Makes possible nearly simultaneous contraction of
entire heart
4. T-tubules of myocardial cells are larger than those
of skeletal muscle and they branch inside the
myocardial cells
5. Myocardial sarcoplasmic reticulum is smaller than
that of skeletal muscle
This is because cardiac muscle depends more on on
extracellular Ca++ to initiate contraction
In this, it resembles smooth muscle more than skeletal
muscle
6. Mitochondria occupy about one third of cell volume
in a cardiac muscle fiber
Cardiac muscle fibers have a very high energy
demand
Cardiac muscle consumes 70-80% of the oxygen
delivered to it by the blood. This is twice the amount of
oxygen extracted from blood by other body cells
The only way to get more oxygen to an exercising
heart is to increase blood flow
This is why blocked arteries can be so dangerous!
Cardiac Muscle Contraction
Fig. 14-11, p. 482
In cardiac muscle, an action potential intitiates EC
coupling (like in the previous chapter), but here, the
AP originates spontaneously in the heart's pacemaker
cells
It then spreads throughout the heart via the gap
junctions connecting the cardiac muscle cells
Neurotransmitters can modulate the pacemaker rate
Cardiac Muscle Contraction
Fig. 14-11, p. 482