Chapter 14Chapter 14

Dee Unglaub Silverthorn, Ph.D.

H ^UMAN P ^HYSIOLOGY H ^UMAN P ^HYSIOLOGY

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AN INTEGRATED APPROACH

T H I R D E D I T I O N

Chapter 14 Chapter 14

Cardiovascular Physiology

• Heart and Blood vessels

• Products transported to sustain all cells Overview of the Cardiosvascular System

Overview of the Cardiosvascular System

Table 14-1: Transport in the Cardiovascular System

Circulation Reviewed Circulation Reviewed

• Heart – "four chambered"

• Right atrium & ventricle

• Pulmonary circuit

• Left atrium & ventricle

• Systemic circuit

• Blood Vessels – "closed circulation"

• Arteries –from heart

• Capillaries– cell exchange

• Veins – to heart

Circulation Reviewed Circulation Reviewed

Figure 14-1: Overview of circulatory system anatomy

• Flows down a pressure gradient

• Highest at the heart (driving P), decreases over distance

• Hydrostatic (really hydraulic) pressure in vessels

• Decreases 90% from aorta to vena cava Blood Flow: Pressure Changes

Blood Flow: Pressure Changes

Blood Flow: Pressure Changes

Blood Flow: Pressure Changes

• Flow rate: (L/min)

• Flow velocity

= rate/C-S area of vessel

• Resistance slows flow

• Vessel diameter

• Blood viscosity

• Tube length

Some Physic of Fluid Movement: Blood Flow Some Physic of Fluid Movement: Blood Flow

Figure 14-4 c: Pressure differences of static and flowing fluid

Some Physic of Fluid Movement: Blood Flow

Some Physic of Fluid Movement: Blood Flow

• Pericardium

• Chambers

• Coronary vessels

• Valves-

(one-way-flow)

• Myocardium

Heart Structure

Heart Structure

• Autorhythmic

• Myocardial

• Intercalated discs

• Desmosomes

• Gap Junctions

• Fast signals

• Cell to cell

• Many

mitochondria

• Large T tubes Cardiac Muscle Cells:

Cardiac Muscle Cells:

Mechanism of Cardiac Muscle Excitation, Contraction & Relaxation

Mechanism of Cardiac Muscle Excitation,

Contraction & Relaxation

• Graded Contraction: proportional to crossbridges formed

• More [Ca++]: crossbridges, more force &

speed

• Autonomic n & epinephrine modulation Modulation of Contraction

Modulation of Contraction

Modulation of Contraction

Modulation of Contraction

• Stretch-length relationship

•  stretch,  Ca++ entering

•  contraction force

• Long action potential

• Long refractory period

• No summation

• No tetanus

More Characteristics of Cardiac Muscle Contraction

More Characteristics of Cardiac Muscle

Contraction

More Characteristics of Cardiac Muscle Contraction

More Characteristics of Cardiac Muscle

Contraction

More Characteristics of Cardiac Muscle Contraction

More Characteristics of Cardiac Muscle Contraction

Figure 14-15c: Refractory periods and summation in skeletal and cardiac muscle

• Pacemaker membrane potential

• I-f channels Na ⁺ influx

• Ca++ channels – influx, to AP

• Slow K ⁺ open – repolarization

Autorhythmic Cells: Initiation of Signals

Autorhythmic Cells: Initiation of Signals

Autorhythmic Cells: Initiation of Signals Autorhythmic Cells: Initiation of Signals

Figure 14-16: Action potentials in cardiac autorhythmic cells

• Sympathetic – speeds heart rate by  Ca++

& I-f channel flow

• Parasympathetic – slows rate by  K+

efflux &  Ca++ influx

Sympathetic and Parasympathetic

Sympathetic and Parasympathetic

• AP from autorhythmic cells in sinoatrial node (SA)

• Spreads via gap junctions down internodal pathways and across atrial myocardial

cells (atrial contraction starts)

• Pause – atrioventricular (AV) node delay

• AV node to bundles of His, branches &

Purkinje fibers

• Right and left ventricular contraction from apex upward

Coordinating the Pump: Electrical Signal Flow

Coordinating the Pump: Electrical Signal Flow

Coordinating the Pump: Electrical Signal Flow

Coordinating the Pump: Electrical Signal Flow

Coordinating the Pump: Electrical Signal Flow Coordinating the Pump: Electrical Signal Flow

Figure 14-19a: Electrical conduction in the heart

Electrocardiogram (ECG):

Electrical Activity of the Heart Electrocardiogram (ECG):

Electrical Activity of the Heart

• Einthoven's triangle

• P-Wave – atria

• QRS- wave – ventricles

• T-wave –

repolarizatio

n

Electrocardiogram (ECG):

Electrical Activity of the Heart Electrocardiogram (ECG):

Electrical Activity of the Heart

Electrocardiography (ECG) Electrocardiography (ECG)

• Measures galvanically the electric activity of the heart

• Well known and traditional, first measurements by Augustus Waller using capillary electrometer (year 1887)

• Very widely used method in clinical environment

• Very high diagnostic value

1. Atrial

depolarization 2. Ventricular depolarization

3. Ventricular repolarization

12-Lead ECG measurement 12-Lead ECG measurement

• Most widely used ECG measurement setup in clinical environment

• Signal is measured non-invasively with 9 electrodes

• Lots of measurement data and international reference databases

• Well-known measurement and diagnosis practices

• This particular method was adopted due to historical reasons, now it is already rather obsolete

Einthoven leads: I, II & III Goldberger augmented leads: V

, V

& V

Precordial leads: V

-V

• (Non-invasive)

• Heart Rate

• Signal conduction

• Heart tissue

• Conditions

ECG Information Gained

ECG Information Gained

Vectorcardiogram (VCG or EVCG) Vectorcardiogram (VCG or EVCG)

• Instead of displaying the scalar

amplitude (ECG curve) the electric activation front is measured and displayed as a vector (dipole model)

 It has amplitude and direction

• Diagnosis is based on the curve that the point of this vector draws in 2 or 3

dimensions

• The information content of the VCG signal is roughly the same as 12-lead

ECG system. The advantage comes from the way how this information is

displayed

• A normal, scalar ECG curve can be

formed from this vector representation, although (for practical reasons)

transformation can be quite complicated

• Plenty of different types of VCG systems

Heart Cycle

Heart Cycle

Heart Cycle:

Heart Chambers and the Beat Sequence Heart Cycle:

Heart Chambers and the Beat Sequence

1. Late diastole: all chambers relax, filling with blood

2. Atrial systole: atria contract, add 20%

more blood to ventricles

3. Isovolumic ventricular contraction: closes

AV valves ("lub"), builds pressure

4. Ventricular ejection: pushes open semi lunar valves, blood forced out

5. Ventricular relaxation: aortic back flow slams semi lunar valves shut ("dub")

AV valves open refilling starts – back to start of cycle

Heart Cycle: Finish and Around To the Start

Heart Cycle: Finish and Around To the Start

Summary of Heart Beat:

Electrical, Pressure and Chamber Volumes Summary of Heart Beat:

Electrical, Pressure and Chamber Volumes

• Range: about 50 – near 200

• Typical resting: near 70

• AP conduction

• Muscle Contraction

• Parasympathetic slows

• Sympathetic speeds

Regulators of the Heart: Reflex Controls of Rate

Regulators of the Heart: Reflex Controls of Rate

Regulators of the Heart: Reflex Controls of Rate

Regulators of the Heart: Reflex Controls of Rate

Definition of Afterload Definition of Afterload

• The "afterload" for any contracting muscle is the total force that opposes shortening, minus the stretching force that

existed prior to contraction. For cardiac muscle, the afterload is the force against which the myocardial fibers must contact during the ejection phase of systole. Force equals pressure times area, by definition. The total force opposing LV

contraction (i.e., the afterload) is the product of the LV pressure and the internal surface area of the LV cavity. In

hypertensive subjects, of course, the arterial and LV pressures are abnormally high during systole and, therefore, the LV

afterload tends to be high. The internal surface area of the LV varies directly with the volume of blood in the ventricle. If the hypertensive subject also has a dilated LV, the internal area of the LV will be greater than that for a normal subject. Hence, for any given pressure, the afterload tends to increase as the

ventricular volume becomes greater. The internal surface area of the ventricular cavity is extremely difficult to measure

precisely. Furthermore, both pressure and area change

continually throughout ejection. Therefore, it is difficult to

assess afterload accurately.

• Around 5L :

(72 beats/m  70 ml/beat = 5040 ml)

• Rate: beats per minute

• Volume: ml per beat

• EDV - ESV

• Residual (about 50%)

Cardiac Output: Heart Rate X Stroke Volume

Cardiac Output: Heart Rate X Stroke Volume

Deep Vein Thrombosis

Deep Vein Thrombosis

Clot Clot

Leg Swelling from Deep Vein Thrombosis

Leg Swelling from Deep Vein Thrombosis

Pulmonary Embolus

Pulmonary Embolus

Vena Caval Filter

Vena Caval Filter

Cardiac Output: Heart Rate X Stroke Volume

Cardiac Output: Heart Rate X Stroke Volume

Left Ventricular Left Ventricular

Pressure-Volume Loops Pressure-Volume Loops Left Ventricular Left Ventricular

Pressure-Volume Loops Pressure-Volume Loops

• Pressure-volume Pressure-volume loop plots LV

loop plots LV

pressure against LV pressure against LV volume through one volume through one

complete cardiac complete cardiac

cycle cycle

• Factors affecting: Factors affecting:

– Preload Preload – Afterload Afterload – Contractility Contractility – IHSS IHSS

– Valvular problems Valvular problems

Left Ventricular Left Ventricular

Pressure-Volume Loops Pressure-Volume Loops Left Ventricular Left Ventricular

Pressure-Volume Loops Pressure-Volume Loops

• KNOW KNOW : :

1. 1. When the mitral and aortic valves are open and When the mitral and aortic valves are open and closed during each phase

closed during each phase

2. 2. When systole begins (B) and ends (D) When systole begins (B) and ends (D) 3. 3. When diastole begins (D) and ends (B) When diastole begins (D) and ends (B)

4. 4. Diastolic filling occurs between points A and B Diastolic filling occurs between points A and B

5. 5. Ejection occurs between points C and D Ejection occurs between points C and D

Left Ventricular Left Ventricular

Pressure-Volume Loops Pressure-Volume Loops Left Ventricular Left Ventricular

Pressure-Volume Loops Pressure-Volume Loops

• Acute changes in Acute changes in preload

preload

– Increased preload Increased preload : :

• Filling increases Filling increases

• SV increases SV increases

– Decreased Decreased preload

preload : :

• Filling decreases Filling decreases

• SV decreases SV decreases

*NOTE: the ventricle

*NOTE: the ventricle empties to the same empties to the same end-systolic volume end-systolic volume

after either an after either an

increase or increase or

decrease in preload

decrease in preload

Left Ventricular Left Ventricular

Pressure-Volume Loops Pressure-Volume Loops Left Ventricular Left Ventricular

Pressure-Volume Loops Pressure-Volume Loops

• Acute changes in Acute changes in Afterload

Afterload

– Increased Increased afterload afterload : :

• Ventricle empties Ventricle empties less completely less completely

• SV decreases SV decreases

• Increase in BP Increase in BP (shifts up and right) (shifts up and right)

– Decreased Decreased afterload afterload : :

• Ventricle empties Ventricle empties more completely more completely

• SV increases SV increases

• Decrease in BP Decrease in BP (shifts down and (shifts down and

left)

left)

Left Ventricular Left Ventricular

Pressure-Volume Loops Pressure-Volume Loops Left Ventricular Left Ventricular

Pressure-Volume Loops Pressure-Volume Loops

• Altered Altered

contractility contractility

– Increased Increased contractility contractility : :

• Ventricle empties Ventricle empties more completely more completely

• SV increases SV increases

• BP increases BP increases

(shifts up and left) (shifts up and left)

– Decrease Decrease d d contractility contractility : :

• Ventricle empties Ventricle empties less completely less completely

• SV decreases SV decreases

• BP decreases BP decreases (shifts down and (shifts down and

right)

right)

Left Ventricular Left Ventricular

Pressure-Volume Loops Pressure-Volume Loops Left Ventricular Left Ventricular

Pressure-Volume Loops Pressure-Volume Loops

• Summary of concepts: Summary of concepts:

– Alterations in preload Alterations in preload : end-diastolic : end-diastolic

volume increases or decreases, but the volume increases or decreases, but the amount of blood in the chamber at end- amount of blood in the chamber at end-

systole does not change systole does not change

– Stroke volume falls Stroke volume falls : result of either an : result of either an increase in afterload or a decrease in increase in afterload or a decrease in

contractility, the volume of blood in the LV contractility, the volume of blood in the LV

chamber increases (chamber dilates) chamber increases (chamber dilates) – Stroke volume increases Stroke volume increases : result of a : result of a

decrease in afterload or an increase in decrease in afterload or an increase in

contractility, the volume of blood in the LV contractility, the volume of blood in the LV

chamber decreases (chamber shrinks)

chamber decreases (chamber shrinks)

Left Ventricular Left Ventricular

Pressure-Volume Loops Pressure-Volume Loops Left Ventricular Left Ventricular

Pressure-Volume Loops Pressure-Volume Loops

• A = Normal A = Normal

• B = Mitral B = Mitral stenosis

stenosis

• C = Aortic C = Aortic stenosis

stenosis

• D = mitral D = mitral regurgitation regurgitation

(chronic) (chronic)

• E = aortic E = aortic

regurgitation regurgitation

(chronic)

(chronic)

• Starlings Law – stretch

• Force of contraction

• Venous return:

• Skeletal pumping

• Respiratory pumping Regulators of the Heart:

Factors Influencing Stroke Volume Regulators of the Heart:

Factors Influencing Stroke Volume

Regulators of the Heart:

Factors Influencing Stroke Volume Regulators of the Heart:

Factors Influencing Stroke Volume

Regulators of the Heart:

Factors Influencing Stroke Volume Regulators of the Heart:

Factors Influencing Stroke Volume

Figure 14-31: Factors that affect cardiac output