Cardiovascular Physiology -Vascular System-

Soo Hwan Lee

Dept of Physiology

Ajou University School of Medicine

(shwanlee@ajou.ac.kr)

1. Hemodynamics

2. The Arterial System

3. The Venous System

4. Microcirculation

5. Coronary Circulation

6. Control of the Circulation

7. Lymphatic System

Contents

Vascular System

Cardiovascular Circuitry Distribution of Blood Volume

Vascular System

Hemodynamics (혈류역학)

Hemodynamics I. Hemodynamics -- 1. 혈류

량

혈류량 (Flow Rate, Q): moving blood volume per unit time (단위시간 당 이동하는 혈액 용적)

Q = V A

Q : Flow rate

V : 평균 혈류속도 (mean velocity)

A : 단면적 (cross-sectional Area)

Velocity of the Bloodstream

Cross-sectional area capillaries > vein > aorta Flow velocity in blood vessels aorta > vein > capillary

Q = ΔP / R < analogous to Ohm’s law : I = V / R >

ΔPr4 Q ≈ ΔP • r4 <Poiseuille Equation> 8L Q: flow rate, R: 저항 (resistance), r: 혈관의 반경(radius), : 혈액 점도 (viscosity), ΔP: 혈관 양단의 압력차(→ 혈압, pressure difference), L: 혈관 길이 (vessel length)

2. 혈류-저항-압력 관계 Relationships between Flow, Pressure, Resistance

• Flow rate (Q) depends on blood pressure (BP). → BP(arterial BP): driving force for circulation! • Size of blood vessels has great influences on the flow rate (Q). 혈류량은 반경(r) 의 4제곱에 비례 (반경의 2배 증가 → 혈류량 16배 증가)

2. 혈류-저항-압력 관계 Relationships between Flow, Pressure, Resistance

Q = ΔP / R < analogous to Ohm’s law : I = V / R >

ΔPr4 Q ≈ ΔP • r4 <Poiseuille Equation> 8L R= ΔP/Q = 8ηL/πr4 R: hydraulic resistance

• Blood Resistance - Cause: friction between blood and vessel wall, friction between

blood molecules - Resistance is inversely proportional to flow rate (Q) - Resistance is inversely proportional to r4 (R 1 / r4, Hagen-Poiseuille Equation: * Atherosclerosis)

- Resistance is proportional to blood viscosity(): hematocrit, diameter,

shear thinning

- Pressure drop: energy loss due to friction → lateral pressure↓

2. 혈류-저항-압력 관계 Relationships between Flow, Pressure, Resistance

Q = ΔP / R < analogous to Ohm’s law : I = V / R >

ΔPr4 Q ≈ ΔP • r4 <Poiseuille Equation> 8L R= ΔP/Q = 8ηL/πr4 R: hydraulic resistance

• Atherosclerosis

The Arterial System (동맥계)

• Arterial Elasticity

• Arterial Blood Pressure - Mean Arterial Pressure - Arterial Pulse Pressure - Peripheral Arterial Pressure Curves

• Blood Pressure Measurement

• Control of Blood Pressure - Determinants of Arterial Pressure

- Regulation of Cardiac Output - Regulation by Baroreceptor and Cardioregulatory Center

1. 대동맥 및 큰 분지(elastic arteries)

- 많은 탄성조직 (elastin)으로 구성

- 확장성 (compliance)이 크고 저항이 낮다.

(압력저장고, pressure storage)

→ 안정적 혈류 (stable blood flow)

→ 심장의 일 감소 (reducing heart-work)

II. 동맥계-1. 동맥의 기능 The Arterial System

Fig-세동맥-SM-13-19-Ho • Artery

- 주된 혈액 관류기능 (hemoperfusion)

- 말초로 갈수록 평활근의 함량이 많아진다. (large smooth muscle content in periphery)

- 벽의 두께에 비하여 혈관내경이 커서 저항이 낮다. (low resistance)

→ 혈압강하가 적다. (small pressure-drop)

• Arteriole (세동맥)

- 내경은 크게 감소하여 높은 저항 (high resistance)

→ “저항혈관 (resistance vessel)” → big pressure drop

- 평활근: 혈류 조절의 기능 (control of blood flow)

Arterial Blood Pressure

• Systolic blood pressure (SBP, maximal)

• Diastolic blood pressure (DBP, minimal)

• Pulse pressure (PP, 맥압) = systolic pressure - diastolic pressure

• Mean arterial pressure (평균동맥압) - the average pressure in a complete cardiac cycle - the main driving force for blood flow

MAP = diastolic pressure + 1/3 pulse pressure

= 1/3 x (systolic pressure + 2 diastolic pressure)

(e.g. At RR 120/80, MAP = 80 mmHg + (1/3) 40 mmHg = 93 mmHg)

Blood Pressure Measurement

brachial artery (상완동맥) Korotkoff’s sound

Control of Blood Pressure (혈압 조절)

Determinants of Pulse Pressure and Mean Arterial Pressure

MAP

• Physical factors

PP SV / C

(PP: pulse pressure, SV: stroke volume, C: aortic compliance)

• Physiological factors

MAP = CO ☓ TPR

* Total Peripheral resistance (TPR) = sum of the resistance of all peripheral vasculature

Control of Blood Pressure (혈압 조절)

1. Regulation of Cardiac Output

Determinants of Cardiac output

- Cardiac factors (heart rate, myocardial contractility), Coupling factors (preload, afterload)

◦ Preload: affected by venous blood pressure and the rate of venous return

◦ Afterload: the tension against which the heart contracts to eject blood

preload afterload HEART

VEDP

Venous Return

VEDV

Hypervolemia/hemorrhage

Contractility

Ejection fraction

TPR

Vasodilation/constriction

Hypertension

Aortic stenosis

Regulation of Blood Pressure (혈압 조절)

1. Regulation of Cardiac Output

1) Frank-Starling’ Principle

- Relationships between Cardiac Output and Venous Return ◦Cardiac Function Curve cardiac output vs venous pressure (usually right atrial pressure) - preload에 의존적으로 CO이 결정된다.

Venous Return VEDV (확장말기용적) stretch of cardiac muscle (심근의 신전) cardiac contractility stroke volume (1회 박출량), cardiac output (심박출량)

- shift upward: cardiac performance is enhanced; increased inotropy, increased heart rate, reduced afterload

- shift downward: cardiac performance is decreased; decreased inotropy, decreased heart rate, increased afterload

- regulation results in [Cardiac output = Venous return]

2) Causes for increase in venous return (정맥환류량의 증가 요인)

- Increase in total blood volume (총혈액량의 증가) - Redistribution of blood by venous compression/constriction (정맥수축에 의

한 혈액량의 재분배)

Cardiac Function Curve ; essentially Frank-Starling curves: - cardiac output (instead of ventricular stroke volume) vs venous pressure (usually right atrial pressure)

Relationships between Cardiac Output and Venous Return

Sympathetic Nervous System

Parasympathetic Nervous System

Effect of Heart Rate on Cardiac Output

HR increase ventricular filling ↓ stroke volume ↓

1. HR increase up to 100 - HR 증가 영향이 SV 감소 보다 큼 - contractility 증가 Increase CO

2. HR (100-200): no significant change in CO

3. HR>200: severe decrease of SV CO 급격한 감소

CO= SV ☓ HR

2. Autonomic Regulation of the Heart

Sympathetic: innervated to both atria and ventricle

Parasympathetic: innervated to SA, AV nodes, and atria

Fig-자율-SA-자극효과-f-2-10-OP

교감신경의 작용 효과 (Sympathetic Effects)

Adrenergic receptors (1)에 작용

- Positive chronotropism (양성변주기작용, HR↑) - Positive inotropism (양성변력작용, contractility↑) - Positive dromotropism (양성변전도작용, conduction velocity↑)

부교감신경의 작용효과 (Parasympathetic Effects)

Acetylcholine (ACh)

- Negative chronotropism: HR 감소

- Negative inotropism: 수축력 감소

- Negative dromotropism: 전도속도 감소

Autonomic Effects on Heart

- atropine (M receptor blocker): heart rate↑ - propranolol ( receptor blocker): heart rate↓ - effects on SA node: parasympathetic > sympathetic

Chronotropy: 변주기작용

Dromotropy: 변전도작용

Inotropy:변력작용

Lusitropy : 심근이완도

3. Regulation by Baroreceptor and Cardioregulatory Center

• Baroreceptor: arch of aorta (대동맥궁), carotid sinus (경동맥동)

- Sensitively respond to changes in arterial pressure → induce the reflex for reciprocal changes of heart rate → prevent steep changes of blood pressure

2. Baroreceptor

MAP Baroreceptor

stretching

Afferent nerve

Cardiovascular

Center (Medulla)

Efferent nerve

Sympathetic↓, Parasympathetic↑

HR↓, Cardiac contractility↓,

Venous expansion Arteriole expansion↑ (skin,

viscera, skeletal muscle)

CO↓ TPR↓

MAP

Baroreceptor reflex

Baroreceptors

Carotid sinus baroreceptors Aortic arch baroreceptors

Location In the walls of the carotid sinus In the walls of the aortic arch

Characteristics more sensitive than aortic

baroreceptor

sensitive to pulsatile pressure

sensitive to stretch pressure

경동맥동 대동맥궁

Fig-Baroreceptor- LI

Fig-Baroreceptor reflex- LI

The Microcirculation System (미소순환계)

• Microcirculation System

• Transcapillary Exchange - Diffusion - Transcytosis - Filtration and Absorption

• Forces of Capillary Filtration

미소순환계 (Microcirculation System)

Microcirculation

Arterioles → Capillaries → Venules

precapillary sphincter(모세혈관 전 괄약근)

모세혈관 (Capillaries)의 특성

- 평균직경 (diameter): 7 μm

- No smooth muscle, thin vessel wall(1 μm)

- 혈류속도 (blood flow velocity): 0.1 ~ 1 mm/sec

- 신체의 거의 모든 세포는 모세혈관으로부터 20 μm 이내에 있다.

미소순환계 (Microcirculation System)

Types of capillaries

1. Diffusion: depends on concentration gradient

- O2, glucose: capillary tissue; CO2, urea: tissue capillary

* low lipid solubility (e.g. Na+, K+, Cl-, glucose): through endothelial pore

* high lipid solubility (e.g. O2, CO2, urea): through endothelial membrane

2. Transcytosis: large molecules encapsulated in vesicle

3. Filtration and absorption

내피 세포공(endothelial pore, fenestrae)을 통한 혈장성분의 이동

Transcapillary Exchange

Forces of Capillary Filtration

Starling equilibrium (Starling’s hypothesis)

- Direction of water flow: determined by balance of hydrostatic pressure and oncotic pressure between inside of capillary and interstitial fluid (ISF)

Fig. 모세혈관-Starling 평형-OX 14-15

The Venous System (정맥계)

• The Venous System

• Characteristics of Venous Flow - Venous Pressure - Factors Promoting Venous Return

Function of Veins (정맥의 기능)

1. Venous return (정맥환류): 정맥을 경유하여 심장으로 유입(환류)되는 혈액

- conduit for venous return from capillaries

2. Capacitant vessel (용량혈관) - blood reservoir: (ca. 64% of total blood volume in systemic veins)

• Volume shift: 정맥의 저장용량은 평활근 수축에 의하여 동맥계(출혈시)로 이동.

정맥계 (The Venous System)

Characteristics of venous flow (정맥혈류의 특징 )

Venous Pressure (정맥압)

• Pressure difference between venule and right atrium: 10 mmHg - venule (세정맥), small vein (소정맥): 10 mmHg - right atrium (우심방): 0 mmHg

Factors promoting venous return

1. Large diameter, low resistance

2. Venous valve (정맥 판막): one-way valve (일방성 판막)

3. Compression/decompression of veins Muscle pump (근육 펌프 ): compression by skeletal muscle

Respiration (호흡운동): descent of diaphragm during inspiration → expansion due to reduced intrathoracic pressure (흉강내 압력) during inspiration; abdominal vein compression by abdominal contents → enhancement of blood flow (abdominal vein → thoracic vein)

Characteristics of venous flow (정맥혈류의 특징 )

• Orthostatic hypotension

선 자세일 때 venous return의 감소 → 수축기압, 이완기압 감소

Effect of Postures to Blood Pressure

• Arterial and venous pressure difference

http://www.google.co.kr/url?sa=i&rct=j&q=&esrc=s&source=images&cd=&cad=rja&uact=8&ved=0CAcQjRw&url=http://courses.washington.edu/conj/heart/cardiacoutput.htm&ei=zoBLVamUOYPOmAXYw4HoCA&bvm=bv.92765956,d.dGY&psig=AFQjCNF0dI6wjEbdOTs_9QBmFDoTtcpTXw&ust=1431097817622603

Valsalva Maneuver

1. Initial pressure rise

2. Reduced venous return and compensation

3. Pressure release

4. Return of cardiac output

attempting to forcibly exhale while keeping the mouth and nose closed.

→ increased intra-thoracic pressure

→ decreased venous return

G-LOC : G-force induced Loss of Consciousness

Major Factors determining peripheral venous

pressure, venous return and stroke volume

Coronary Circulation (관상혈관순환)

• Coronary Circulation

• Acute Coronary Syndrome

Coronary Circulation

• Right coronary artery: right atrium and right ventricle

• Left coronary artery: anterior descending and circumflex branches;

left atrium and left ventricle • Coronary sinus • Anterior coronary vein

Coronary Artery Bypass Graft (CABG)

Coronary Angioplasty Nitroglycerin

Sublingual Tablet : act in 1 -3 min

Acute Coronary Syndrome

: group of symptoms attributed to obstruction of the coronary arteries

• Symptoms

- Angina pectoris (chest pain often radiating to the left arm) - chest pressure - nausea and sweating

• Treatment

Control of the Circulation (순환조절)

• Regulation of the Peripheral Circulation - Intrinsic or Local Control of Peripheral Blood Flow - Extrinsic Control of Peripheral Blood Flow

• Interplay of Central and Peripheral Factors in Control of the Circulation: Integrated Control

- Hemorrhage - Exercise

Regulation of the peripheral circulation

1. Intrinsic or local control of peripheral blood flow

Autoregulation and Myogenic regulation

Endothelium-mediated regulation

Metabolic Regulation

2. Extrinsic control of peripheral blood flow

Sympathetic vasoconstriction

Parasympathetic neural influence

Humoral factor

Vascular reflex

1. Intrinsic or local control of peripheral blood flow

- Local (intrinsic) control of blood flow: the primary mechanism utilized for matching blood flow to the metabolic needs of a tissue

1) Autoregulation and Myogenic regulation

; the maintenance of a constant blood flow to an organ in the face of changing arterial pressure. (changes in transmural pressure)

2) Endothelium-mediated regulation

Local vasoactive mediators

Vasodilators: nitric oxide, histamine, PGI2, EDHF Vasoconstrictors: angiotensin II, endothelin, EDCF

3) Metaboilc regulation

Active hyperemia (능동적 충혈) ; blood flow to an organ is proportional to its metabolic activity e.g. to meet the increased metabolic demand * Local metabolic changes O2↓ CO2↑ acid↑ (carbonic acid, lactic acid ) K+↑ (repeated action potentials) Osmolarity↑ (by increased cellular metabolism) Adenosine release Prostaglandin releases

Reactive hyperemia (반응충혈) ; an increase in blood flow in response to

or reacting to a prior period of decreased blood flow.

e.g. arterial occlusion O2 debt increase in blood flow above the pre-

occlusion levels

2. Extrinsic control of peripheral blood flow

1) Sympathetic vasoconstriction

- pressor region (dorsal lateral medulla) stimulation: vasoconstriction, cardiac acceleration, enhanced myocardial contractility

- depressor area (caudal, ventromedial) stimulation: decreases arterial blood pressure

2) Parasympathetic neural influence

3) Humoral factor - epinephrine and nor-epinephrine

4) Vascular reflex - area of the cerebral medulla that mediate sympathetic and vagal

effects are under the neural influence from the baroreceptor, chemoreceptor, hypothalamus, cerebral cortex, and skin

Interplay of central and peripheral factors in control of the circulation: integrated control

Hemorrhage

1) Course of arterial pressure changes 2) Compensatory mechanism

• Baroreceptor reflex • Chemoreceptor reflex • Cerebral ischemia • Reabsorption of tissue fluid • Release of endogenous vasoconstrictors • Renal conservation of salt and water

3) Decompensatory mechanism

A: recovery

B: hemorrhagic shock

• Baroreceptor reflex

• Chemoreceptor reflex

Blood loss → Hypoxia

→ chemoreceptor reflex → enhancing peripheral

constriction

→ respiration center에 작용, respiration→ venous

return (due to inspiration)

-Baroreceptor

Chemoreceptors

1. Peripheral chemoreceptors - Located in aortic and carotid bodies, heart - PO2 , PCO2 , pH 변화 감지

- sensitive to decrease in PO2 - less sensitive to PCO2 , pH

2. Central chemoreceptors - Located in medulla - PCO2 , pH 변화 감지 (PO2 has little effect)

• Reabsorption of tissue fluid

Short-term regulation

Long-term regulation에 의해 유지되어야 함.

• Release of endogenous vasoconstrictors

- catechoamines, vasopressin, renin-angiotensin system

Fig-R-A-A system- LI

Renin-Angiotensin-Aldosterone system

• Renal conservation of salt and water - vasopressin, renal sympathetic activity↑ → reabsorption of NaCl by

nephron↑ - low arterial pressure → glomerular filtration↓ → excretion of water

and electrolytes↓ - angiotensin II → aldosterone↑ → reabsorption of water, NaCl↑

3) Decompensatory mechanism

• cardiac failure (bleeding → blood pressure ↓ → coronary blood flow ↓

→ ventricular function ↓ )

• acidosis

• central nervous system depression

• aberrations in blood clotting

• reduced function of mononuclear phagocytic system

Hemorrhage

Exercise

Interplay of central and peripheral factors in control of the circulation: integrated control

- Control of cardiovascular function during exercise by

Neural factor

(1) central command (중추명령) (2) reflex originating in the muscle contraction (3) the baroreceptor reflex

Chemical factor - vascular chemoreceptor (pH, PCO2, PO2)

Mild to Moderate Exercise

Peripheral resistance↓ Cardiac output↑ Venous return↑ Arterial pressure↑ Redistribution of blood

Mild to Moderate Exercise

Peripheral resistance

Cardiac output

Venous return

Arterial pressure

Severe exercise - compensatory mechanisms begin to fail

Postexercise recovery

Limits of exercise performance - the rate of O2 utilization by muscles and O2 supply to muscles

Physical training and conditioning - Response to regular exercise: increase capacity to deliver O2 to the active

muscles and improve the ability of the muscle to use O2

C: 혈관수축활성, D: 혈관확장활성

ix:혀인두신경(glossopharyngeal

nerve);

VR, vasomotor region (혈관운동부위)

X: 미주신경;

+ 증가활성; -: 감소활성

Lymphatic System (림프계)

an accessory route by which interstitial fluid can be returned to the blood

V. Lymph-1. 림프관의 기능-2. 부종

Lymphatic System

Functions 1. removal of interstitial fluid from tissues 2. absorbs and transports fatty acids and fats from the digestive system 3. transports white blood cells to and from the lymph nodes into the bones 4. transports antigen-presenting cells (APCs), to the lymph nodes where an

immune response is stimulated.

Fig. 림프관-전신-fig 22-4-FM

• Definition

; abnormal accumulation of fluid in the interstitium • Causes

- Increased venous pressure, accompanied by an increased capillary pressure (congestive heart failure, 울혈성심부전).

- Increased permeability of the capillary walls (inflammation).

- Decreased plasma proteins (malnutrition, renal failure).

- Blockage of lymph vessels (parasite infection, surgery)

Edema

Elephantiasis

Lymphatic filariasis (림프사상충증)

Blockage of lymph vessels

출석확인용 Assignmnet (Assignment for checking attendance) Q. Cardiac function curve에서 shift upward 및 shift downward의 의미와, 그 원인에 대해 쓰시오.