Fig. 12.2 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. O2O2 Systemic circulation (to body) Circulation.

Fig. 12.2 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

O2

Systemiccirculation(to body)

Circulation totissues of head

Tissuecapillaries

Pulmonarycirculation(to lungs)

Lung

Lungcapillaries

Right side of heart

Tissuecapillaries

O2CO2

Circulation totissues oflower body

CO2

O2

Left sideof heart

CO2

Fig. 12.10-1

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Aortic arch

Left pulmonary artery

Branches of leftpulmonary arteries

Pulmonary trunk

Pulmonary veins

Left atrium

Bicuspid valve

Left ventricle

Interventricular septum

Superiorvena cava

Branches ofright pulmonaryarteries

Aortic semilunarvalvePulmonaryveins

Right atrium

Tricuspid valve

Papillary muscles

Right ventricle

(a)Inferiorvena cava

Pulmonary semilunarvalve

Fig. 12.5-1


Superior vena cava

Branches of rightpulmonary artery

Right pulmonary veins

Right atrium

Coronary sulcus

Right coronary artery

Right ventricle

Inferior vena cava

(a) Anterior view

Aortic arch


Branches of leftpulmonary artery

Pulmonary trunk

Left pulmonary veins

Left atrium

Great cardiac vein(in anterior interventricular sulcus)

Anterior interventricular artery(in anterior interventricular sulcus)

Left ventricle

Fig. 12.13


Branchingmuscle fibers

Intercalated disks

Nucleus of cardiacmuscle cell

LM 400x

Mitochondrion

Striations

Sarcolemma (cell membrane)

Connective tissue

(b)(a)

Myofibrils

Sarcomere

Sarcoplasmicreticulum

T tubule

b: © Ed Reschke

Fig. 12.11


Aortic arch

Pulmonarytrunk

Left atrium

Posterior veinof left ventricle

Coronarysinus

Greatcardiacvein

Leftventricle

Anterior view(b)

Right ventricle

Smallcardiacvein

Middlecardiac vein

Superiorvena cava

Rightatrium Into

rightatrium

Aortic arch

Pulmonarytrunk

Left coronaryartery

Left atrium

Circumflexartery

Left marginalartery

Anteriorinterventricularartery

Left ventricle

Anterior view(a)

Right ventricle

Rightmarginalartery

Posteriorinterventricularartery

Rightcoronaryartery

Rightatrium

Superiorvena cava

Aorticsemilunarvalve


–85

1 2

0

(mV

)

1 2

0

Depolarization phase• Na+ channels open.• K+ channels begin to open.

Repolarization phase• Na+ channels close.• K+ channels continue to open, causing

repolarization.• K+ channels close at the end of

repolarization and return the membranepotential to its resting value.

Depolarization phase• Na+ channels open.• Ca2+ channels open.

Plateau phase• Na+ channels close.• Some K+ channels open, causing

repolarization.• Ca2+ channels are open, producing the

plateau by slowing further repolarization.

Repolarization phase• Ca2+ channels close.• Many K+ channels open.

1

2

1

2

3

1

2 1

2

3

Skeletal Muscle Cardiac Muscle

Plateauphase

Repolarizationphase

RepolarizationphaseDepolarization

phase

–85

(mV

)

500

Time (ms)Time (ms)

Depolarizationphase

(a) (b)


Pulmonary semilunar valve

Aorticsemilunar valve

Tricuspidvalve

Cardiac muscleof the rightventricle

Cardiac muscleof the left ventricle

Posterior view

Bicuspidvalve

Cardiac skeleton

Fig. 12.15

1

2

3

4

1

3

2

4

Action potentials originate in the sinoatrial (SA) nodeand travel across the wall of the atrium (arrows) fromthe SA node to the atrioventricular (AV) node.

Action potentials pass through the AV node andalong the atrioventricular (AV) bundle, which extendsfrom the AV node, through the fibrous skeleton, intothe interventricular septum.

The AV bundle divides into right and left bundle branches,and action potentials descend to the apex of each ventriclealong the bundle branches.

Action potentials are carried by the Purkinje fibersfrom the bundle branches to the ventricular walls.

ApexPurkinjefibers

Right and leftbundle branches

Atrioventricular(AV) bundle

Sinoatrial(SA) node

Atrioventricular(AV) node

Left atrium

Left ventricle



(mV

)

R

P

T

Q

S

QRS complex

Time (seconds)

QT intervalPQ interval


Aortic arch


Pulmonary trunk


Left pulmonary veins

Left atrium

Bicuspid (mitral) valve

Left ventricle

Chordae tendineae

Papillary muscles

Interventricular septum

Anterior viewInferior vena cava

Right ventricle

Papillary muscles

Tricuspid valve

Coronary sinus

Right atrium


Pulmonarysemilunar valve

Aortic semilunar valve

Branches of rightpulmonary artery

Superior vena cava

Fig. 12.8


Pulmonary veins

Aorta

Aortic semilunarvalve (closed)

(a) Anterior view

Left ventricle(relaxed)

Cardiac muscle(relaxed)

Papillary muscle(relaxed)

Left atrium

Bicuspid valve(open)

Aorta

Pulmonary veins

Left atrium

Bicuspid valve(closed)

Chordae tendineae(tension high)

Papillary muscle(contracted)

Cardiac muscle(contracted)

Left ventricle(contracted)

Aortic semilunarvalve (open)Chordae tendineae

(tension low)

(b) Anterior view


Contraction of the ventricles causespressure in the ventricles to increase.Almost immediately, the AV valvesclose (the first heart sound). Thepressure in the ventricles continuesto increase.

Continued ventricular contractioncauses the pressure in the ventriclesto exceed the pressure in the pulmonarytrunk and aorta. As a result, thesemilunar valves are forced open,and blood is ejected into thepulmonary trunk and aorta.

The atria contract and completeventricular filling.

The AV valves open, and blood flows intothe ventricles. The ventricles fillto approximately 70% of theirvolume.

At the beginning of ventriculardiastole, the ventricles relax, and thesemilunar valves close (the secondheart sound).

2

3

4

5

1

Semilunarvalves closed

Semilunarvalves opened

AV valvesclosed

AV valvesclosed


AV valvesopened


AV valvesclosed


AV valvesopened


Pulmonarysemilunar valve

Aorticsemilunar valve

Bicuspidvalve

Outline ofheart

Tricuspidvalve

© Terry Cockerham/Cynthia Alexander/ Synapse Media Productions

Fig. 12.22


Sensory neurons (green) carryaction potentials from baroreceptorsto the cardioregulatory center.Chemoreceptors in the medullaoblongata influence thecardioregulatory center.

The cardioregulatory center controlsthe frequency of action potentials inthe parasympathetic neurons (red )extending to the heart. Theparasympathetic neurons decreasethe heart rate.

The cardioregulatory center controlsthe frequency of action potentials inthe sympathetic neurons (blue)extending to the heart. Thesympathetic neurons increase theheart rate and the stroke volume.

The cardioregulatory centerinfluences the frequency of actionpotentials in the sympatheticneurons (blue) extending to theadrenal medulla. The sympatheticneurons increase the secretion ofepinephrine and somenorepinephrine into the generalcirculation. Epinephrine andnorepinephrine increase the heartrate and stroke volume.

Adrenal medullaEpinephrine and norepinephrine

Circulation

Heart

SA node

Baroreceptorsin aorta

Carotid bodychemoreceptors

Baroreceptorsin wall of internalcarotid artery

Cardioregulatory center andchemoreceptors in medulla oblongata

Sensory nervefibers

Sensorynervefibers

Sympatheticnerve fibers toadrenal gland

4

3

2

1

3

1

2

3

4

Fig. 12.20Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Blo

od

pre

ssu

re(n

orm

al r

ang

e)

The SA node and cardiac muscle (theeffectors) increase activity and heartrate and stroke volume increase.

The SA node and cardiac muscle (theeffectors) decrease activity and heartrate and stroke volume decrease.

Baroreceptors in the carotid arteries andaorta detect a decrease in blood pressure.

The cardioregulatory center in the brainincreases sympathetic stimulation of theheart and adrenal medulla and decreasesparasympathetic stimulation of the heart.

Baroreceptors in the carotid arteries andaorta detect an increase in blood pressure.

The cardioregulatory center in the braindecreases sympathetic stimulation of theheart and adrenal medulla and increasesparasympathetic stimulation of the heart.

Blo

od

pre

ssu

re(n

orm

al r

ang

e)

Blood pressure increases:Homeostasis Disturbed

Blood pressure decreases:Homeostasis Disturbed

2

3

4

61

Start here

Blood pressure decreases:Homeostasis Restored

5

Blood pressure increases:Homeostasis Restored


Blo

od

pH

(no

rmal

ran

ge)

The SA node and cardiacmuscle (the effectors) increaseactivity and heart rate and strokevolume increase, increasingblood flow to the lungs.

The SA node and cardiac muscle(the effectors) decrease activityand heart rate and stroke volumedecrease, reducing blood flow tothe lungs

Chemoreceptors in the medulla oblongata detect anincrease in blood pH (often caused by a decreasein blood CO2). Control centers in the brain decreasestimulation of the heart and adrenal medulla.

Chemoreceptors in the medulla oblongata detect adecrease in blood pH (often caused by an increasein blood CO2). Control centers in the brain increasestimulation of the heart and adrenal medulla.

Blood pH decreases:Homeostasis Disturbed

Blood pH increases:Homeostasis Restored

Blood pH decreases:Homeostasis Restored

2

3

4

5

1 6

Blo

od

pH

(no

rmal

ran

ge)

Start here

Blood pH increases:Homeostasis Disturbed

Fig. 12.2 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. O2O2 Systemic circulation (to body) Circulation.

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