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