chapter 14a
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Chapter 14a
Cardiovascular Physiology
About this Chapter
• Overview of the cardiovascular system• Pressure, volume, flow, and resistance• Cardiac muscle and the heart• The heart as a pump
Overview: Cardiovascular System
Table 14-1
Overview: Cardiovascular System
Figure 14-1
Ascending arteries
Descending arteries
Abdominal aorta
Left atrium
Left ventricle
HeartRight ventricle
Renalveins
Renalarteries
Hepaticvein
Right atrium
Coronary arteries
PulmonaryveinsPulmonary
arteriesSuperior vena cava
Inferior vena cava
Ascending veins
Venous valve
Arms
Lungs
Aorta
Trunk
Kidneys
Pelvis andLegs
Liver Digestivetract
Hepatic artery
Hepatic portal vein
Capillaries ArteriesVeins
Head andBrain
Pressure Gradient in Systemic Circulation
• Blood flows down pressure gradients
Figure 14-2
Pressure Differences in Static and Flowing Fluids
• The pressure that blood exerts on the walls of blood vessels generates blood pressure
Figure 14-3a
Pressure Differences in Static and Flowing Fluids
• Pressure falls over distance as energy is lost due to friction
Figure 14-3b
Pressure Change
• Pressure created by contracting muscles is transferred to blood
• Driving pressure for systemic flow is created by the left ventricle
• If blood vessels constrict, blood pressure increases
• If blood vessels dilate, blood pressure decreases
• Volume changes greatly affect blood pressure in CVS
Fluid Flow through a Tube Depends on the Pressure Gradient
• Flow ∆P
Figure 14-4a
★
Fluid Flow through a Tube Depends on the Pressure Gradient
Figure 14-4b
Fluid Flow through a Tube Depends on the Pressure Gradient
Figure 14-4c
As the Radius of a Tube Decreases, the Resistance to Flow Increases
Figure 14-5
★
Flow Rate is Not the Same as Velocity of Flow• Flow (Q): volume that passes a given point• Velocity of flow (V): speed of flow• V = Q/A A= cross sectional area
• Leaf in stream• Mean arterial pressure cardiac output
peripheral resistance (varies by X-sec of arteries)
Figure 14-6
Structure of the Heart
• The heart is composed mostly of myocardium
Figure 14-7e–f
Diaphragm
(e) The heart is encased withina membranous fluid-filledsac, the pericardium.
Pericardium
STRUCTURE OF THE HEART
(f) The ventricles occupy the bulk ofthe heart. The arteries and veins allattach to the base of the heart.
Superiorvena cava
Rightatrium
Auricle ofleft atrium
Aorta
Pulmonaryartery
Rightventricle Left
ventricle
Coronaryarteryand vein
Anatomy: The Heart
Table 14-2
Structure of the Heart
• The heart valves ensure one-way flow
Figure 14-7g
(g) One-way flow through the heartis ensured by two sets of valves.
Right atrium Left atrium
Pulmonarysemilunar valve
Rightpulmonary
arteries
Right ventricle
Superiorvena cava
Left pulmonaryarteries
Aorta
Left pulmonaryveins
Cusp of the AV(bicuspid) valve
Cusp of a right AV(tricuspid) valve
Chordae tendineae
Inferiorvena cava
Papillary muscles
Left ventricle
Descendingaorta
Heart Valves
Figure 14-9a–b
Heart Valves
Figure 14-9c–d
Anatomy: The Heart
PLAY Interactive Physiology® Animation: Cardiovascular System: Anatomy Review: The Heart
Cardiac Muscle
Figure 14-10(b)
Contractile fibers
Nucleus
Mitochondria
Cardiac muscle cell
(a)
Intercalated disk(sectioned)
Intercalated disk
Cardiac Muscle• Excitation-contraction coupling and relaxation in cardiac muscle Ca+2• Autorhythmic cells – pacemakers set heart rate ~ 70 / min
• Auto or self generate action potentials – stimulate neighboring cells to generate action potentials
Figure 14-11
1
2
3
4
5
6
7
8
9
10
776
5
8
4
910
32
1
Ca2+ ions bind to troponinto initiate contraction.
Relaxation occurs whenCa2+ unbinds from troponin.
Na+ gradient is maintainedby the Na+-K+-ATPase.
Voltage-gated Ca2+
channels open. Ca2+
enters cell.
Ca2+ induces Ca2+ releasethrough ryanodinereceptor-channels (RyR).
Local release causesCa2+ spark.
Ca2+ is pumped backinto the sarcoplasmicreticulum for storage.
Ca2+ is exchanged withNa+ by the NCX antiporter.
Action potential entersfrom adjacent cell.
Summed Ca2+ sparkscreate a Ca2+ signal.
ATP NCX
3 Na+
3 Na+
2 K+
ATP
Sarcoplasmic reticulum(SR)
Myosin
Actin
Relaxation
Ca2+
Ca2+
Ca2+ Ca2+
Ca2+ stores
ECF
ICF
T-tubule
L-typeCa2+
channel
Ca2+
Ca2+ sparks
Ca2+ signal
Contraction
Ca2+
SR
RyR
Cardiac Muscle Contraction
• Can be graded• Sarcomere length affects force of contraction• Action potentials vary according to cell type
Myocardial Contractile Cells• Action potential of a cardiac contractile cell• Refractory period in cardiac muscle – long no tetanus
Figure 14-13
44
0
0 100 200 300Time (msec)
PX = Permeability to ion X
PK and PCa
PNa
PK and PCa
+20
–20
–40
–60
–80
–100
Phase Membrane channels
Na+ channels openNa+ channels closeCa2+ channels open; fast K+ channels closeCa2+ channels close; slow K+ channels openResting potential
PNa
0
01234
12
3
Mem
bran
e po
tent
ial (
mV)
Long refractory period in cardiac muscle
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