Department of medical physiology11th week

Semester: winterStudy program: Dental medicineLecture: RNDr. Soňa Grešová, PhD.Department of medical physiologyFaculty of Medicine PJŠU

Cardiovascular system10th week

1. General hemodynamics

2. Local control of blood flow by the tissues and humoral regulation

3. Blood pessure regulation

Venous side- Large lumen- Thin wall- Low pressure

system- Hight volume

system- Driving blood

from exchangevessels

- Deoxygenatedblood

- Unstress volume

Arteries side- Small lumen- Thick wall- Hight pressure

system- Low volume

system- Provides blood to

exchange vessels- Oxygenated

blood- Stressed volume

1. General hemodynamics

Copyright: Hall, J. E., & Guyton, A. C. (2006). Guyton and Hall textbook of medical physiology. Philadelphia, PA: Saunders Elsevier.

1. General hemodynamics -pressures

Copyright: Hall, J. E., & Guyton, A. C. (2006). Guyton and Hall textbook of medical physiology. Philadelphia, PA: Saunders Elsevier.

1. General hemodynamics –Cross-Sectional Areas and Velocities of Blood Flow

• Velocity is rate of linear

displacement of blood per unit

time

𝑉 =𝑄

𝐴= 𝜋×𝛾2

- Because the same volume of

blood must flow through each

segment of the circulation

each minute, the velocity of

blood flow is inversely

proportional to vascular cross-

sectional area.

Copyright: Hall, J. E., & Guyton, A. C. (2006). Guyton and Hall textbook of medical physiology. Philadelphia, PA: Saunders Elsevier.

1. General hemodynamics-Interrelationships Among Pressure, Flow, and Resistance

• Blood flow (Q) – bloodwhich passes from a part of circulatory system per time

• Pressure gradient isdifferent from 1 point to 2nd point

• Resistence is obstruction of blood flow

Ohm’s law:

𝑄 =∆𝑃

𝑅

Copyright: Hall, J. E., & Guyton, A. C. (2006). Guyton and Hall textbook of medical physiology. Philadelphia, PA: Saunders Elsevier.

1. General hemodynamics-Interrelationships Among Pressure, Flow, and Resistance

• Poiseuille’s Law

• Resistance- series- paralel

• Reynolds’ number

- Laminar Flow of Blood in Vessels

- Turbulent Flow of Blood

When Reynolds’ number rises above 200 to 400,turbulent flow will occur at some branches of vessels butwill die out along the smooth portions of the vessels.However, when Reynolds’ number rises above approximately2000, turbulence will usually occur even in astraight, smooth vessel.

Copyright: Hall, J. E., & Guyton, A. C. (2006). Guyton and Hall textbook of medical physiology. Philadelphia, PA: Saunders Elsevier.

1. General hemodynamics-microcirculation

• Fluid filtration across capillaries is determined by hydrostatic and colloid osmotic pressures, and capillary filtration coefficient

• Pc – the capillary pressure, which tends to forcefluid outward through the capillary membrane

• πp – the capillary plasma colloid osmotic pressure, which tends to cause osmosis of fluid inwardthrough the capillary membrane

• PIF – the interstitial fluid pressure, which tends to force fluid inward through the capillary membrane when Pif is positive but outward when Pif isnegative

• πIF - the interstitial fluid colloid osmotic pressure,which tends to cause osmosis of fluid outwardthrough the capillary membrane

Copyright: Hall, J. E., & Guyton, A. C. (2006). Guyton and Hall textbook of medical physiology. Philadelphia, PA: Saunders Elsevier.

1. General hemodynamics-microcirculation

• Analysis of the forces causing Filtration at the arterial end of the capillary

• Analysis of Reabsorption at the venousend of the capillary

Copyright: Hall, J. E., & Guyton, A. C. (2006). Guyton and Hall textbook of medical physiology. Philadelphia, PA: Saunders Elsevier.

1. General hemodynamics-microcirculation

• If the sum of these forces, the net filtration pressure, is positive, there will be a net fluid filtration across the capillaries. If the sum of the Starling forces is negative, there will be a net fluid absorption from the interstitial spaces into the capillaries.

• The net filtration pressure (NFP) is calculated as: 𝑁𝐹𝑃 = 𝑃𝑐 − 𝑃𝑖𝑓 − Π𝑝 + Π𝑖𝑓

Copyright: Hall, J. E., & Guyton, A. C. (2006). Guyton and Hall textbook of medical physiology. Philadelphia, PA: Saunders Elsevier.

• Continuous capillaries– Exocrine glands, Nervous tissue, Muscle, Lung

• Endothelial cell body forms a continuous lining• Transport of material across the endothelium is by

diffusion and by pinocytosis• the junctions between the capillary endothelial cells are

mainly “tight” junctions that allow only extremely small molecules such as water, oxygen, and carbon dioxide to pass into or out

• Fenestrated capillaries– Endocrine glands, Kidney, Gut

• Continuous basement membrane• numerous small oval windows called fenestrae

penetrate all the way through the middle of the endothelial cells, so that tremendous amounts of very small molecular and ionic substances

• Discontinuous Capillaries– Bone marrow, Spleen, Liver

• Basement membrane is discontinuous• the clefts between the capillary endothelial cells are

wide open, so that almost all dissolved substances of the plasma, including the plasma proteins, can pass

1. General hemodynamics-microcirculation

Copyright: Hall, J. E., & Guyton, A. C. (2006). Guyton and Hall textbook of medical physiology. Philadelphia, PA: Saunders Elsevier.

2. Local control of blood flow by thetissues and humoral regulation

• Local control

• Short term regulation = acute control (second to minutes)– changes in vasodilatation

(adenosine, carbon dioxide, adenosine phosphate compounds, histamine, potassium ions, and hydrogenions) or vasoconstriction of the arterioles, metarterioles, and precapillary sphincters

e.g., tissue metabolism, oxygen,

Copyright: Hall, J. E., & Guyton, A. C. (2006). Guyton and Hall textbook of medical physiology. Philadelphia, PA: Saunders Elsevier.

2. Local control of blood flow by thetissues and humoral regulation

• Local control

• Long-term local control– change in the physical sizeor number of the bloodvessels (vascularendothelial growth factor(VEGF), fibroblast growth factor, and angiogenin), occurs over days to months

• e.g., tissue vascularity, oxygen,

2. Local control of blood flow by thetissues and humoral regulation

• Local control• Humoral control

- Substances secreted or absorbed into the body fluids that cause

vasoconstriction or vasodilatation, e.g. hormones, peptides and ions• Vasoconstrictors agents

- Norepinephrine and Epinephrine- Angiotensin II.- Vasopressin- Endothelin-A- Serotonin (from platelets)- Tromboxane A2 (from platelets)

• Vasodilatator agents- Bradykinin- Histamine- Nitric oxide (from endothelial cells)- Prostacyclin (from endothelial cells) Copyright: Hall, J. E., & Guyton, A. C. (2006). Guyton and Hall

textbook of medical physiology. Philadelphia, PA: Saunders Elsevier.

3. Blood pressure

• The force of blood against artery walls• Recoreded as two numbers

1. Systolic pressure (120 mmHg)

- heart contracts

2. Diastolic pressure (80 mmHg)

- heart relaxes

3. Blood pressure regulationBP

Systolic BP Diastolic BP

Total peripheral resistanceCO

SV HR

preload contractility afterload

Regulatory mechanisms of systemiccirculation

1. Local

a) myogenic autoregulation (stretch gated Ca channels)b) metabolic autoregulation (CO2, ADP, organic acids)c) Endothelial regulation (constr.: Endothelin, TX A2), (dilatat.: NO, PGI2)d) enzymatic regulation (constr.: Serotonin, dilatat.: Histamin, bradykinin)

2. Generala) short-therm regulation

I. nervous regulation (SNS, dilatation =pas. mechanisms, PSNS)II. humoral regulation (N/Epi, Endothelin, ANP, RAAS stress)

III. vascular reflexes (baroreceptors, chemoreceptors)b) long-therm regulation

I. ADH (osmoreceptors)II. Aldosterone (RAAS)

BP

Systolic BP Diastolic BP

Total peripheral resistanceCO

SVHR

preload contractility afterload

Circulatingfactors

Innervation Viscosity Localregulators

Ang II(N)-Epi

α1 Rβ 2 R

EndothelinO2

NOH+

AdenosinePG

(N)-EpiGlucagonThyroid HSNSPSNS

TPR

• Atrial Ref. Volum.R-Bainbridge response

• Bezold-Jarisch reflexHR

(N)-EpiGlucagonThyroid HSNSPSNS • Blood Volume

- Renal retentionAldosteroneADHSNSANP

- Thirst• Venous tone

(N)-EpiSNS

1. Baroreceptors

- carotic sinus

- aortic arch receptors

3. Blood pressure regulationShort-term regulation (neural)

Copyright: Hall, J. E., & Guyton, A. C. (2006). Guyton and Hall textbook of medical physiology. Philadelphia, PA: Saunders Elsevier.

3. Central chemoreceptors

3. Blood pressure regulationShort-term regulation (neural)

2. Peripheral Chemoreceptors

- carotic body

- aortic body

Copyright: Hall, J. E., & Guyton, A. C. (2006). Guyton and Hall textbook of medical physiology. Philadelphia, PA: Saunders Elsevier.

Arterioloconstrictor: TPR, afterload, CO

Arteriolodilatator: TPR, afterload, CO

+ Inotropic effect: LV contractility isstrong, operating with less pressure, CO

- Inotropic effect: LV contractility is less, operating with hight pressure, CO

Venoconstrictor: VR, RAP, CO

Venodilatator: VR, RAP, CO

Cardiac Output

Afterload

Preload

Medulla oblongata

1. Nucleus of tractussolitarius

2. Cardioinhibitory center

3. Cardioacceleratorycenter

4. Vasomotor center

3. Blood pressure regulationShort-term regulation (neural)

Copyright: Hall, J. E., & Guyton, A. C. (2006). Guyton and Hall textbook of medical physiology. Philadelphia, PA: Saunders Elsevier.

3. Blood pressure regulationShort-term regulation (neural)

Copyright: Hall, J. E., & Guyton, A. C. (2006). Guyton and Hall textbook of medical physiology. Philadelphia, PA: Saunders Elsevier.

• Atrial natriureticpeptide

- natriumuresis

3. Blood pressure regulationShort-term regulation (humoral)

3. Blood pressure regulationLong-term regulation

• Long- term regulation = long-term control

- Regulation renin-

angiotensine-aldosteron

system (RAAS)

Copyright: Hall, J. E., & Guyton, A. C. (2006). Guyton and Hall textbook of medical physiology. Philadelphia, PA: Saunders Elsevier.

• ADH – antidiuretichormon

3. Blood pressure regulationLong-term regulation (humoral)

3. Blood pressure regulation

Copyright: Hall, J. E., & Guyton, A. C. (2006). Guyton and Hall textbook of medical physiology. Philadelphia, PA: Saunders Elsevier.

4. Special hemodynamics

1. Pulmonary circulation2. The coronary circulation3. Cerebral circulation4. Renal blood circulation5. Splanchnic blood circulation6. Skeletal muscle blood circulation7. Circulation of blood through the skin8. Fetal circulation