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Cardiovascular Physiology -Vascular System-
Soo Hwan Lee
Dept of Physiology
Ajou University School of Medicine
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
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.