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
Veins
Capillaries
Arteries
Head and
Brain
Arms
Lungs
Superior vena cava
Pulmonary
arteries
Right atrium
Pulmonary
veins
Ascending arteries
Aorta
Left atrium
Coronary arteries
Left ventricle
Abdominal aorta
Right ventricle
Heart
Inferior vena cava
Trunk
Hepatic artery
Hepatic portal vein
Hepatic
vein
Digestive
tract
Liver
Ascending veins
Renal
veins
Renal
arteries
Descending arteries
Venous valve
Kidneys
Pelvis and
Legs
Figure 14-1
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
STRUCTURE OF THE HEART
Aorta
Superior
vena cava
Pericardium
Right
atrium
Right
ventricle
Pulmonary
artery
Auricle of
left atrium
Coronary
artery
and vein
Left
ventricle
Diaphragm
(e) The heart is encased within
a membranous fluid-filled
sac, the pericardium.
(f) The ventricles occupy the bulk of
the heart. The arteries and veins all
attach to the base of the heart.
Figure 14-7e–f
Anatomy: The Heart
Table 14-2
Structure of the Heart
• The heart valves ensure one-way flow
Aorta
Pulmonary
semilunar valve
Right
pulmonary
arteries
Superior
vena cava
Left pulmonary
arteries
Left pulmonary
veins
Left atrium
Right atrium
Cusp of the AV
(bicuspid) valve
Cusp of a right AV
(tricuspid) valve
Chordae tendineae
Papillary muscles
Left ventricle
Right ventricle
Inferior
vena cava
Descending
aorta
(g) One-way flow through the heart
is ensured by two sets of valves.
Figure 14-7g
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
(a)
Intercalated disk
(sectioned)
Nucleus
Intercalated disk
Mitochondria
Cardiac muscle cell
Contractile fibers
(b)
Figure 14-10
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
10
Ca2+
1
ECF
2 K+
ATP
ICF
9
3 Na+ Ca2+
1 Action potential enters
from adjacent cell.
NCX
3 Na+
RyR
2
Ca2+
2+
2+
3 Ca induces Ca release
through ryanodine
receptor-channels (RyR).
2
3
L-type
Ca2+
channel
SR
Ca2+
4
Sarcoplasmic reticulum
(SR)
release causes
4 Local
Ca2+ spark.
Ca2+ stores
ATP
Ca2+ sparks
T-tubule
Voltage-gated Ca2+
channels open. Ca2+
enters cell.
2+
5 Summed Ca sparks
create a Ca2+ signal.
8
2+
6 Ca ions bind to troponin
to initiate contraction.
5
Ca2+ signal
6
Contraction
Ca2+
7 Relaxation occurs when
Ca2+ unbinds from troponin.
Ca2+
7
7
Relaxation
Actin
Myosin
2+
8 Ca is pumped back
into the sarcoplasmic
reticulum for storage.
2+
9 Ca is exchanged with
Na+ by the NCX antiporter.
10 Na+ gradient is maintained
by the Na+-K+-ATPase.
Figure 14-11
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
Membrane potential (mV)
1
+20
PX = Permeability to ion X
PNa
2
PK and PCa
0
–20
3
–40
0
–60
PNa
–80
4
PK and PCa
4
–100
0
Phase
100
200
Time (msec)
300
Membrane channels
0
Na+ channels open
1
Na+ channels close
2
Ca2+ channels open; fast K+ channels close
3
Ca2+ channels close; slow K+ channels open
4
Resting potential
Figure 14-13
Long refractory period in cardiac muscle