BAI GIANG HE TUAN HOAN (circulation)

Structure of the heart and heart muscle to function as a pump generating driving force for the bulk flow of the blood 2.. Components of a circulatory system• Circulatory fluid: blood, l

circulatory system

C.L Standfield.2011 Principles of Human Physiology, 4thedition

Color angiogram of a healthy heart

Circulation system

1 Structure of the heart and heart muscle to function as a pump generating

driving force for the bulk flow of the blood

2 autorhythmicity of the heart

3 Heart cycle and its phases

4 Cardiac out and factors affect cardiac output

5 Vasculature : arteries, arterioles, veins and their function

6 Arterioles and the distribution of blood flow to organs

7 Mean arterial pressure (MAP) as the driving force for the blood flow

8 Bulk flow of fluid across capillary walls

9 Role of the lymphatic circulation

Functions of Cardiovascular System

1 Carrying of oxygen and carbon dioxide

2 Carrying of fuel, hormones etc

3 Immunity

4 Heat Transfer

Components of a circulatory system

• Circulatory fluid: blood, lymph

• Pump (heart): generates the driving force for the bulk flow of blood

• Vessels

• Valves

– Keep the blood flowing in one direction

Circulatory systems in human

• Cardiovascular system ( Hệ tuần hoàn máu)

• Lymphatic system ( Hệ tuần hoàn bạch huyết)

Cardiovascular system

Blood flow in the circulation is bulk flow

•Blood pressure values:

Pulmonary Circulation = 24/8 mm Hg (Systolic/Diastolic) Systemic Circulation = 120/80 mm Hg(Systolic/Diastolic)

Huyết áp ở các loại mạch trong tuần hoàn phổi và

tuần hoàn hệ thống

Location of the heart in the thoracic cavity

6

8-12 cm

Xương ức

Structure of the heart

Cung động mạch chủ

Động mạch phổi

Tâm nhĩ trái

Van bán nguyệt Van 2 lá

Vách nhĩ thất

Tâm thất trái Mỏm tim

Tĩnh mạch chủ dưới

•4 chambers, 2 halves (right and left), each half contains:

•Atrium :receives blood coming back to the heart from the vasculature

•Ventricle: receives blood from atrium, generates force to push the blood through the vasculature

•valvesLeft ventricle- Aorta, right ventricle-pulmonary artery

Brief Overview of Electrical Activity of the Heart

There are three main types of heart cells:

•Heart muscle cells‐ These are the contractile cells of the heart.

•Conducting cells‐ Modified muscle cells that rapidly conduct

electrical charge.

•Pacemaker Cells‐ Located in Sinoatrial Node (SAN) these cells

spontaneously electrically discharge and set the pace or rhythm

of the heart rate.

In order for heart muscle cells to mechanically contract or generate force they must first be electrically excited.

Myocardium/ cardiac muscle

• properties of both skeletal muscle and smooth muscle

• Striation appearance

• Cardiac muscle cells are

interconnected by intercalated discs -> action potential is

transmitted rapidly

The autorhythmicity of the heart

• The heart can generate signals triggering its own contraction on a periodic basic – the heart has autorhymthmicity because it has a conduction system

( contractile activity of cardiac muscle is said to be myogenic )

• Conduction system of the heart contains autorhythmic cells :

– Pacemaker cells can generate action potential and establish the heart rhymth:

• Sinoatrial node (SA node)

Spread of action potential between cardiac

muscle cells

Electric current/action potential (ions) can be passed from one cells to other rapidly through gap junctions (intercalated disks)

The spread of action potentials through the heart

Stanius experiment

Xoang nhĩ

2

3 4

5 1

Electrocardiogram-ECG ( Điện tim )

http://www.bmb.leeds.ac.uk/illingworth/myopath/heart.htm

-ECG is a record of the overall spread of electrical current through the heart as a function of time during the cardiac cycle

-ECG reflects patterns of AP firing in entire population of heart muscle cells

- recorded by electrodes placed on the skin

-Willem Einthoven ‘s techmique -Einthoven’s triangle: right arm, left arm, left leg:

- Limb electrodes: Lead I, II, III -Chest electrodes: V1-V6

a basic ECG

− P wave: atrial depolarization

- QRS: ventricular depolarization -T: ventricular repolarization

- QT : time for contraction of ventricles

-PQ interval: time of conduction through AV node

-TQ : time for relaxation of ventricles

- RR : time between heart beats

- rate of record: 25mm/sec;

1mV/cm

C.L Standfield.2011 Principles of Human Physiology, 4thedition

Abnormal ECG

Cardiac cycle

(Chu kì hoạt động của tim/chu chuyển tim)

Cardiac cycle

• Cardiac cycle contains all the events

associated with the flow of blood through the heart during a single complete heart beat

Duration of a cardiac cycle

• 0,8 second (human)

• 2 stages: - systole ( tim co/tâm thu);

- diastole (tim giãn/ tâm trương)

Atria contraction: 0.1 sec.

ventricle contraction: 0.3sec

relaxation

of 8 seconds of a cardiac cycle, atria have

7 sec and ventricles have 5 sec of relaxation !

4 phases of a cardiac cycle

The main variables and events during a cardiac cycle:

• atrial, ventricular, and aortic pressures

• ventricular volume

• valves opening , closure and heart sounds

Changes in atrial and ventricular pressure

Changes in atrial and ventricular pressure

SP (Systolic Pressure) : huyết áp tâm thu

DP (diastolic pressure): huyết áp tâm

trương

MAP (mean aterial pressure): huyết áp

động mạch trung bình

Changes in ventricular volume during the cardiac cycle

At rest: EDV = 130ml, ESV = 60ml -> SV = 130-60= 70 ml

Ejection Fraction (Tỷ lệ tống máu) EF = SV/EDV = 70/130 = 0.54

Thể tích cuối tâm trương

Thể tích tống máu

Thể tích cuối tâm thu

Heart sounds

• “lupp-DUPP

• Sounds caused by the turbulent rushing of blood through the valves as they are narrowing and about to close

– 1 st sound: “lubb” - AV valves are closing

Cardiac Output- CO

from each ventricle with one heart beat ( 60-80ml)

• Cardiac output- CO (lưu lượng tim/thể tích phút): the volume of blood

being pumped from each ventricle in one minute

CO= HR x SV

For an adult at rest: HR = 72 beats/min; SV = 70 ml - CO = 5L

Control of cardiac output

• Extrinsic control ( Điều khiển ngoại sinh): regulation of the heart by neural input, circulating hormones and factors originating from outside the heart

the heart by factors originating from the heart

CO = HR x SV

Factors affecting the heart rate

•sympathetic nervous system

SA, AV nodes as well as to ventricular myocardium

-norepinephrine

(noradrenaline): increases the heart rate

•parasympathetic nervous

system (Thần kinh phó giao

cảm): only to SA,AV nodes

- acetylcholine Decreases the heart rate

neural control of the heart rate

C.L Standfield.2011 Principles of Human Physiology, 4thedition

•autonomous nervous system

Binding of norepinephrine to beta 1 adrenegic receptors on the membrane of SA, AV nodal cells causes an increase in heart rate

• Norepinephrine- beta1 adrenegic receptor ->

cAMP -> activated protein kinase -> open Na+,

Ca2+ channels -> Na+, Ca2+ move into the cells -

> decreases the time for depolarization of the membrane -> increases the frequency of action potentials

-> increases the heart rate

Fig 13.24.a C.L Standfield.2011 Principles of Human Physiology, 4thedition

Binding of Acetylcholine to cholinergic receptors on cells of AS and AV nodes causes decreased heart rate

• cholinergic receptor ->

Acetylcholine-close Ca2+ channels and open K+ -> K+ move into the cells -> hyperpolarization of cell membrane ->

increase the time for the cell membrane to

be depolarized->

decrease heart rate

C.L Standfield.2011 Principles of Human Physiology, 4thedition

C.L Standfield.2011 Principles of Human Physiology, 4thedition.

C.L Standfield.2011 Principles of Human Physiology, 4thedition.

Factors affect the stroke volume(SV)

• contractility

• End diastolic volume (EDV)

• afterload

The sympathetic nervous system increases the strength

and rate of contraction of cardiac muscle cells

C.L Standfield.2011 Principles of Human Physiology, 4thedition

End-diastolic volume affects stroke volume

C.L Standfield.2011 Principles of Human Physiology, 4thedition

C.L Standfield.2011 Principles of Human Physiology, 4thedition.

• Factors that increase activity of the

Vasculature, blood flow, blood pressure,

and resistance

Blood flow through the systemic circulation is driven

by mean arterial pressure (MAP)

MAP is the driving force for the blood flow

C.L Standfield.2011 Principles of Human Physiology, 4thedition

Q = ΔP/R

ΔP = aortic pressure (MAP) – vena cava pressure

= MAP – 0 = 85 - 0 = 85

• total peripheral pressure -TPR

Pressure and pressure drops in the pulmonary and

L: vessel length R: vessel radius

C.L Standfield.2011 Principles of Human Physiology, 4thedition

η : blood viscosity

MAP = HR x SV x TPR

Huyết áp động mạch tỉ lệ thuận với tần số tim, thể tích tâm thu và tổng sức cản

• Arteries conduct blood away from the heart

• Veins: conduct blood back to

the heart

• Arterioles: passageway for blood to enter the capillaries from capillary

• Capillaries: site of exchange between blood and tissue

• Venule:s passageway for blood

to flow to the veins from the capillary

• Walls of arteries and veins:

– endothelium

– Smooth muscle

– Connective tissue

containing collagen , elastin

• Walls of capillaries:

– endothelium

– Basement

membrane

Functions of blood vessels

• Arteries – pressure reservoir

• Arterioles – sites for control of blood flow distribution to organs

• Capillaries – sites of material exchange

between blood and tissues

• Veins: volume reservoir

• Conduct blood away from the heart

• The largest artery is the aorta (ĐMC): 12.5

mm ( diameter), 2mm (wall thickness)

• Arteries branching off the aorta: 2-6mm; 1

mm

• The walls of large arteries are richer in

collagen and elastin than those of small ones

• The walls of small arteries with diameter

<0.1mm have almost no elastic fibers but are rich in smooth muscles

Arteries: pressure reservoir

The heart beats periodically but the blood flows

• Systolic/ Diastolic pressures

• Korotkoff sounds caused by turbulent blood flow

C.L Standfield.2011 Principles of Human Physiology, 4thedition

Arterioles – sites for control of blood flow

distribution to organs

Arterioles provide the greatest resistance

to blood flow

• Conducts blood flow from

smallest arteries into capillary beds

• Total cross-sectional area of

arterioles is smaller than that of arteries ->Arterioles provide the greatest

resistance to blood flow (60% of total peripheral resistance)

C.L Standfield.2011 Principles of Human Physiology, 4thedition

• Blood pressure

decreases gradually as blood flow from arteries

to veins

• pressure drop is a

difference in pressure across any portion of the vasculature

• As arterioles have

highest resistance, the largest pressure drop occurs along them

C.L Standfield.2011 Principles of Human Physiology, 4thedition

Arterioles – sites for control of blood flow

distribution to organs

• Walls of arterioles are surrounded by

numerous rings of circular smooth

change the radius of arterioles -> the resistance for the blood flow is best regulated in arterioles to control blood

regulate blood pressure

• Intrinsic factors regulate arteriole

smooth muscle contraction and relaxation: O2 and metabolite concentration, myogenic control, local chemicals: NO, bradykinin, histamine, prostacyclin, adenosine (specially for coronary arteries) as vasodilator;

endothelin-1 as vasoconstrictor

C.L Standfield.2011 Principles of Human Physiology, 4thedition.

Extrinsic control of arteriole Radius and mean

arterial pressure

• The autonomous nervous system:

– The sympathetic nervous system ->

norepinephrine –α adrenergic receptor ->

vasoconstriction

– Epinephrine- α receptor – vasoconstriction

– Epinephrine- beta 2 receptor – vasodilation

– The parasympathetic nervous system innervate only arteriolar smooth muscles of external

genitalia -> acetylcholine -> vasodilation

• Hormonal control:

– Vasopressin (ADH) – vasodilation

– Angiotensin II: vasoconstriction

Arterioles - sites for control of blood flow distribution to organs

•Blood flow in the circulation is parallel

flow

• With parallel flow every organ can be

supplied by the same flow given the resistance is the same in each organ

•By changing its own resistance, each

organ can receive a desired blood flow matching its metabolic need -> at any given time blood flow can be increased to more organs and decreased to less active organ

•Arterioles are sites where resistance for

blood flow to each organ can be regulated

by intrinsic factors

Blood flow distribution to organs changes on organ’s need

C.L Standfield.2011 Principles of Human Physiology, 4thedition

Capillaries – sites of material exchange

between blood and tissues

Capillaries

• 1mm long , 5-10 um in diameter

• Thin walls (0.5 um) contain one layer of endothelial cells and basement

membrane -> facilitates diffusion

• Branching structures: 10-40 billion capillaries -> 600 m2 exchanging surface

• Greatest total sectional area ->

cross-Slowest velocity of blood flow

C.L Standfield.2011 Principles of Human Physiology, 4thedition

Regulation of blood flow through capillaries

•1mm long, 5-10micrometer thick

•10-40 billion cappilaries – 600 m2

•Capilalary bed

•Microcirculation

•precapillary sphinters regulate the

blood flow to tissues:

•precapillary sphinters are affected

by local controls : metabolites produced by local tissues

– increased CO2 , decreased O2 -> sphinters relax -> increased blood flow and vice versa – Metarteriole connect arteriole với venule có các vòng cơ bị tác động của yếu tố nội sinh co để thay đổi dòng chảy

C.L Standfield.2011 Principles of Human Physiology, 4thedition

• Continuous capillaries

(Mao mạch kín):

permeable to small molecules and lipophilic molecules (O2, CO2, steroid hormones)

• Fenestrated capillaries

(Mao mạch thấm):

permeable to proteins, cells, small hydrophilic molecules

C.L Standfield.2011 Principles of Human Physiology, 4thedition

The bulk flow across capillary walls maintains balance

between interstitial fluid and plasma

• As capillary walls are permeable to water and small solutes-> fluid can move from blood to interstitial fluid: filtration or from interstitial fluid to blood : absorption

• Starling forces is the driving forces for the

movemnet of fluid into or out of capillaries : capillary hydrostatic pressure (PCAP) and the interstial hydrostatic pressure t (PIF ); capillary osmotic pressure (πCAP ) ,

interstitial osmotic pressure (πIF)

• NFP (net filtration pressure- Áp lực lọc thực ) NFP = Filtration pressure – Absorption Pressure

Blood flow through a capillary is filtrated at the arteriole end and

absorbed at the venule end

• one day: 20 L of fluid are filtered and 17 L of fluid are absorbed

-> 3 L of fluid moves out of

the blood vessels each day !

- > roles of the lymphatic system

NFP= 12 mmHg NFP= -10 mmHg

Veins function as volume reservoirs

• Veins are thin walled

• Veins are equipped with one-way valves

• Veins have high compliance as they are thin walled and easily stretched -> can

accommodate a large blood volume with little change in blood

of the total blood volume is stored in the systemic veins

C.L Standfield.2011 Principles of Human Physiology, 4thedition