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Atenção: Recomendamos o material a seguir apenas com o objetivo de divulgar materiais de qualidade e que estejam disponíveis gratuitamente. Profa. Cristina Maria Henrique Pinto CFS/CCB/UFSC.

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slide1

Atenção:

Recomendamos o material a seguir apenas com o objetivo de divulgar materiais de qualidade e que estejam disponíveis gratuitamente.

Profa. Cristina Maria Henrique Pinto

CFS/CCB/UFSC

O presente arquivo é uma coletânea de figuras e textos extraídos da coleção em CD-ROM utilizada em nossas aulas.

“Interactive Physiology”, da Benjamin Cummings.

slide2

Você pode também dar baixa destes resumos dos CD-ROM´s, não apenas de Cardiovascular mas de

diversos outros assuntos de Fisiologia Humana

(arquivos em *.pdf e/ou *.doc), com textos e ilustrações, diretamente do site:

Selecione: “assignments”em:

http://www.aw-bc.com/info/ip/

e escolha entre os seguintes assuntos:

Muscular; Nervous I; Nervous II; CardiovascularRespiratory; Urinary; Fluids & ElectrolytesEndocrine e Digestive(novos)

Veja também aulas online (DEMO dos CD-ROM´s) sobre:

Endocrine topics eDigestive system (recém-lançados)

slide3

Cardiovascular Physiology

parte 4:

Blood Pressure Regulation and Autoregulation and Capillary Dynamics

Profa. Cristina Maria Henrique Pinto - CFS/CCB/UFSC

monitores: Vinicius Negri Dall'Inha e Grace Keli Bonafim (graduandos de Medicina)

Este arquivo está disponível em: http://www.cristina.prof.ufsc.br/md_cardiovascular.htm

slide5

Blood Pressure Regulation

Graphics are used with permission of:

Pearson Education Inc., publishing as Benjamin Cummings (http://www.aw-bc.com)

Introduction

• There are two basic mechanisms for regulating blood pressure:

(1) short-term mechanisms, which regulate blood vessel diameter, heart rate and contractility

(2) long-term mechanisms, which regulate blood volume

Goals

• To compare and contrast the short-term mechanisms that respond to rising blood pressure with the short-term mechanisms that respond to falling blood pressure.

• To understand the process of long-term regulation of low blood pressure.

• To describe the long-term and short-term effects of increased osmolarity on blood pressure.

Short-Term Regulation of Rising Blood Pressure

• Short-term Regulation of Rising Blood Pressure

• Rising blood pressure

• Stretching of arterial walls

• Stimulation of baroreceptors in carotid sinus, aortic arch, and other large arteries of the neck and thorax

• Increased impulses to the brain

• Label this diagram:

slide6

Effect of Baroreceptors

• Increased impulses to brain from baroreceptors

• Increased parasympathetic activity and decreased sympathetic activity

• Reduction of heart rate and increase in arterial diameter

• Lower blood pressure

. Increased Parasympathetic Activity

• Effect of Increased Parasympathetic and Decreased Sympathetic Activity on Heart and Blood Pressure:

• Increased activity of vagus (parasympathetic) nerve

• Decreased activity of sympathetic cardiac nerves

• Reduction of heart rate

• Lower cardiac output

• Lower blood pressure

• Label the following diagram and explain what is happening in the animation:

Decreased Sympathetic Activity

• Effect of Decreased Sympathetic Activity on Arteries and Blood Pressure:

• Decreased activity of vasomotor fibers (sympathetic nerve fibers)

• Relaxation of vascular smooth muscle

• Increased arterial diameter

• Lower blood pressure

slide7

Short-term Regulation of Falling Blood Pressure

• Short-term Regulation of Falling Blood Pressure:

• Falling blood pressure

• Baroreceptors inhibited

• Decreased impulses to the brain

• Decreased parasympathetic activity, increased sympathetic activity

• Three effects:

1. Heart: increased heart rate and increased contractility

2. Vessels: increased vasoconstriction

3. Adrenal gland: release of epinephrine and norepinephrine which enhance heart rate, contractility, and vasoconstriction

• Increased blood pressure

Sympathetic Activity on Heart and Blood Pressure

• Effect of Increased Sympathetic Activity on Heart and Blood Pressure:

• Increased activity of sympathetic cardiac nerves

• Decreased activity of vagus (parasympathetic) nerve

• Increased heart rate and contractility

• Higher cardiac output

• Increased blood pressure

. Vasomotor Fibers

• Effect of Increased Sympathetic Activity on Arteries and Blood Pressure:

• Increased activity of vasomotor fibers (sympathetic nerve fibers)

• Constriction of vascular smooth muscle

• Decreased arterial diameter

• Increased blood pressure

slide8

Sympathetic Activity on Adrenal Gland and Blood Pressure

• Effect of Increased Sympathetic Activity on Adrenal Glands and Blood Pressure:

• Increased sympathetic impulses to adrenal glands

• Release of epinephrine and norepinephrine to bloodstream

• Hormones increase heart rate, contractility and vasoconstriction. Effect is slower-acting and more prolonged than nervous system control.

• Increased blood pressure

Recap: Regulation of Falling Blood Pressure

• Recap: Regulation of Falling Blood Pressure

• Falling blood pressure

• Baroreceptors inhibited

• Decreased impulses to the brain

• Decreased parasympathetic activity

• Increased sympathetic activity

• Increased heart rate and contractility

• Increased vasoconstriction

• Release of epinephrine and norepinephrine from adrenal gland

• Increased blood pressure

• Take notes on this diagram as the animation proceeds:

slide9

Introduction: Long-Term Regulation of Low BP

• Long-term regulation of blood pressure is primarily accomplished by altering blood volume.

• The loss of blood through hemorrhage, accident, or donating a pint of blood will lower blood pressure and trigger processes to restore blood volume and therefore blood pressure back to normal.

• Long-term regulatory processes promote the conservation of body fluids via renal mechanisms and stimulate intake of water to normalize blood volume and blood pressures.

Loss of Blood

• When there is a loss of blood, blood pressure and blood volume decrease.

Kidney Juxtaglomerular Cells

• Juxtaglomerular cells in the kidney monitor alterations in the blood pressure. If blood pressure falls too low, these specialized cells release the enzyme renin into the bloodstream.

Renin-Angiotensin Mechanism: Step 1

• The renin/angiotensin mechanism consists of a series of steps aimed at increasing blood volume and blood pressure.

• Step 1: Catalyzing Formation of Angiotensin I: As renin travels through the bloodstream, it binds to an inactive plasma protein, angiotensinogen, activating it into angiotensin I.

slide11

Step 2: Conversion of Angiotensin I

• Step 2: Converting Angiotensin I to Angiotensin II: As angiotensin I passes through the lung capillaries, an enzyme in the lungs converts angiotensin I to angiotensin II.

• Label this diagram:

Step 3: Angiotensin II in the Bloodstream

• Step 3: Angiotensin II Stimulates Aldosterone Release: Angiotensin II continues through the bloodstream until it reaches the adrenal gland.

slide12

Release of Aldosterone

• Step 3: Angiotensin II Stimulates Aldosterone Release: Here it stimulates the cells of the adrenal cortex to release the hormone aldosterone.

slide13

Angiotensin II as a Vasoconstrictor

• A secondary effect is that angiotensin II is a vasoconstrictor and therefore raises blood pressure in the body's arterioles.

Aldosterone Mechanism

• Long-Term Regulation: Aldosterone Mechanism: The target organ for aldosterone is the kidney. Here aldosterone promotes increased reabsorption of sodium from the kidney tubules.

Distal Convoluted Tubule

• Long-Term Regulation: Aldosterone Mechanism:

• Each distal convoluted tubule winds through the kidney and eventually empties its contents into a urine-collecting duct.

• The peritubular capillaries absorb solutes and water from the tubule cells as these substances are reclaimed from the filtrate.

• Label the diagram of the kidney tubules and associated blood vessels on the top of the next page.

slide14

. Sodium Reabsorption

• Aldosterone stimulates the cells of the distal convoluted tubule to increase the active transport of sodium ions out of the tubule into the interstitial fluid, accelerating sodium reabsorption.

• Label this diagram:

slide15

. Water Reabsorption

• As sodium moves into the bloodstream, water follows. The reabsorbed water increases the blood volume and therefore the blood pressure.

• Label this diagram:

slide16

Increase in Osmolarity

• Dehydration due to sweating, diarrhea, or excessive urine flow will cause an increase in osmolarity of the blood and a decrease in blood volume and blood pressure.

. Long-Term Effect of Osmolarity on BP

• As increased osmolarity is detected there is both a short and long-term effect. For the long-term effect, the hypothalamus sends a signal to the posterior pituitary to release antidiuretic hormone (ADH).

Antidiuretic Hormone

• ADH increases water reabsorption in the kidney.

ADH in Distal Convoluted Tubule

• ADH promotes the reabsorption of water from the kidney by stimulating an increase in the number of water channels in the distal convoluted tubules and collecting tubules (ducts).

• These channels aid in the movement of water back into the capillaries, decreasing the osmolarity of the blood volume and therefore blood pressure.

• Label the diagram on the top of the next page.

slide18

Short-Term Effect of Osmolarity on BP

• A short-term effect of increased osmolarity is the excitation of the thirst center in the hypothalamus. The thirst center stimulates the individual to drink more water and thus rehydrate the blood and extracellular fluid, restoring blood volume and therefore blood pressure.

Other Chemicals That Influence BP

• There are many other chemicals which influence blood flow and blood vessel diameter. Most of them act by influencing blood vessel diameter.

Summary

• In the short-term, rising blood pressure stimulates increased parasympathetic activity, which leads to reduced heart rate, vasodilation and lower blood pressure.

• Falling blood pressure stimulates increased sympathetic activity, which leads to increased heart rate, contractility, vasoconstriction, and blood pressure.

• Long-term blood pressure regulation involves renal regulation of blood volume via the renin-angiotensin mechanism and aldosterone mechanism.

• Increased blood osmolarity stimulates release of antidiuretic hormone (ADH), which promotes reabsorption of water, and excites the thirst center, resulting in increased blood volume and blood pressure.

slide19

Notes on Quiz Questions:

Quiz Question 1: Identification

• This question asks you to label structures which are important in blood pressure regulation.

Quiz Question 2: High Blood Pressure

• This question asks you to lower blood pressure by clicking on the appropriate nerve.

Quiz Question 3: Chemical Heart Stabilization

• This question asks you to identify the chemical that will increase blood pressure.

Quiz Question 4: Blood Volume Chain Reaction

• This question asks you to list the proper sequence of events that occurs when blood volume and blood pressure increases or decreases.

Quiz Question 5: Dehydration Chain Reaction

• This question asks you to list the proper sequence of events that occurs when dehydration increases or decreases.

slide20

Study Questions on Blood Pressure Regulation:

1. What are baroreceptors?

2. Where are the baroreceptors that sense blood pressure located?

3. What happens to baroreceptors when blood pressure is high?

4. What happens to both parasympathetic activity and sympathetic activity when blood pressure is high?

5. What is the effect of increased parasympathetic activity and decreased sympathetic activity on both heart rate and blood pressure?

6. What is the name of the parasympathetic nerve that decreases heart rate?

7. How does a decrease in heart rate decrease blood pressure?

8. What is a vasomotor fiber?

9. What is the effect of high blood pressure on arteries?

10. How does vasodilation decrease blood pressure?

11. What happens to baroreceptors when the blood pressure is low? What effect does that have on the brain?

slide21

12. What are the three effects of an increased sympathetic activity and decreased parasympathetic activity?

13. How does an increase in heart rate increase blood pressure?

14. What is the effect of low blood pressure on arteries?

15. How does vasoconstriction increase blood pressure?

16. What is the effect of sympathetic activity on the adrenal gland?

17.Why are the effects of epinephrine and norepinephrine from the adrenal gland slower-acting and more prolonged than nervous system control?

18. When there is a loss of blood through hemorrhage, accident, or donating a pint of blood, what two long-term regulatory processes will restore blood volume and therefore blood pressure back to normal?

19. What happens to blood volume and blood pressure when there is blood loss?

20. If blood pressure falls too low, what do the juxtaglomerular cells of the kidney release into the bloodstream?

slide22

21. What is angiotensinogen?

22. How is angiotensinogen activated?

23. How is angiotensin I converted into Angiotensin II?

24. Place the following steps in the release of aldosterone in order:

a. An enzyme in the lungs converts angiotensin I to angiotensin II.

b. Angiotensinogen is activated into angiotensin I.

c. Angiotensin II stimulates the cells of the adrenal cortex to release the hormone aldosterone.

d. As renin travels through the bloodstream, it binds to an inactive plasma protein, angiotensinogen.

e. Angiotensin II continues through the bloodstream until it reaches the adrenal gland.

f. Angiotensin I passes through the lung capillaries.

25. What happens when Angiotensin II reaches the adrenal gland?

26. What are two effects of angiotensin II?

27 What is the target organ for aldosterone?

28 What is the effect of aldosterone?

slide23

29.What is "filtrate" and where is it located within the kidneys? What is its relationship to the blood capillaries.

30. What is the process of reabsorption within the kidneys?

31. What happens when aldosterone binds to the cells of the distal convoluted tubule?

32. How does aldosterone increase the blood volume and blood pressure?

33. What effect does dehydration due to sweating, diarrhea, or excessive urine flow have on osmolarity of the blood, blood volume, and blood pressure?

35. An increased osmolarity of the blood causes the release of what hormone?

36. What is the effect of ADH?

37.How does ADH increase water reabsorption in the kidney?

38. What is the short-term effect of increased osmolarity of the blood on blood pressure?

slide24

39.. (Summary) When blood volume and blood pressure are increased, do the following increase or decrease?

a. Renin release from the kidney ________.

b. Angiotensinogen into Angiotensin I _______.

c. Angiotensin I into Angiotensin II _______.

d. Aldosterone release from the adrenal gland _______.

e. Sodium reabsorption from the filtrate into the blood _______.

f. Water reabsorption _______.

g. Blood volume and blood pressure _______.

40 (Summary) When blood volume and blood pressure are decreased, do the following increase or decrease?

a. Renin release from the kidney ________.

b. Angiotensinogen into Angiotensin I _______.

c. Angiotensin I into Angiotensin II _______.

d. Aldosterone release from the adrenal gland _______.

e. Sodium reabsorption from the filtrate into the blood _______.

f. Water reabsorption _______.

g. As a result blood volume and blood pressure _______.

41(Summary) When there is an increase in dehydration, are the following increased or decreased?

a. Body water _______.

b. Blood volume and blood pressure _______.

c. Blood osmolarity _______.

d. ADH release from the pituitary _______.

e. Water permeability of the kidney tubules _______.

f. Urine output and blood osmolarity _______.

g. As a result, blood volume and blood pressure _______.

slide25

Autoregulation and Capillary Dynamics

Graphics are used with permission of:

Pearson Education Inc., publishing as Benjamin Cummings (http://www.aw-bc.com)

Introduction

• Blood flow through individual organs is controlled intrinsically in response to local requirements. The phenomenon is called autoregulation. When true capillaries are flushed with blood, exchanges occur between the capillary blood and tissue cells.

. Goals

• To explain the importance of autoregulation.

• To list the chemical and physical factors that serve as autoregulatory stimuli in the various tissues.

• To describe the means by which various solutes are transported across capillary walls

• To explain factors that determine the amount and direction of fluid flows across the capillary walls.

Autoregulation

• Autoregulation is the process by which the various organs and tissues of the body self-regulate blood delivery. This process can be compared to water flow regulation. A pumping station pumps water to individual houses via water pipes, just as the heart pumps blood to individual organs via blood vessels.

slide26

Water Regulation and Water Pressure

• Within each house, the residents can regulate the amount of water entering the house according to their needs. As long as water pressure remains normal, they can get water anytime they want to.

. Blood Regulation and Mean Arterial Pressure

• Similarly, as long as mean arterial pressure is normal, the various organs and body tissues of the body can regulate the amount of blood that enters them according to their needs at any given time.

. Single Capillary Bed

• Blood flow regulation occurs at the capillary beds. The feeder arteriole bring blood to the capillary bed. The shunt is a short vessel that directly connects the feeder arteriole and the drainage venule at the opposite end of the bed. Exchanges of materials take place between tissue cells and the blood in the true capillaries. The precapillary sphincter is a cuff of smooth muscle fibers that surround the root of each true capillary, acting as a valve to regulate the flow of blood into the true capillaries.

Precapillary Sphincters Open or Close

• The build-up of certain chemical signals locally acts as a metabolic control that causes the feeder arterioles to dilate, bringing more blood into the local area. These chemical signals also cause the precapillary sphincters to relax.

slide27

Oxygen

• If the oxygen levels in the tissue cells are already high, no more blood flow is needed in that area until the oxygen levels are lower again.

Carbon Dioxide

• Carbon dioxide is a metabolic waste product. If it builds up in a capillary bed, then the precapillary sphincters will open to allow it to be removed from the area.

pH

• Typically acids that accumulate must be removed from tissues. So when there is a low pH a lot of acid is present and the precapillary sphincters open.

Nutrients

• If nutrients are already present in a capillary bed, precapillary sphincters will close. They open when nutrients are needed.

Body Temperature

• During a fever, precapillary sphincters tend to open. In the skin, this will allow heat to dissipate from the body.

Blood Pressure

• Local physical factors acting on the vascular smooth muscle, such as changing blood volume and blood pressure, also act as autoregulatory stimuli that affect arterioles.

• Decreased blood pressure will cause precapillary sphincters to open, allowing more blood to reach the capillary bed.

• Circle each of the following conditions that cause precapillary sphincters to open:

slide28

High 02

Low 02

High CO2

Low CO2

High pH (low acid)

Low pH (high acid)

Adequate nutrients

Lack of nutrients

Normal Body Temperature

Fever

Decreased blood pressure,

decreased arteriole stretch

Increased blood pressure,

increased arteriole stretch

slide29

Capillary Exchange

• True capillaries are the sites of solutes exchanges between blood in the lumen of the capillaries and the tissue cells.

Capillary Wall Anatomy

• Several structural characteristics of capillaries aid the transport process:

1. Capillary endothelial cells have fenestrations, which are pores that may be opened or covered by a very delicate membrane, allowing for passage of fluids and small solutes.

2. Clefts between cells also allow movement of materials between the blood and tissue cells.

3. Cytoplasmic vesicles move material across the capillary wall by bulk transport.

• Label the parts of the diagram on the top of the next page.

slide31

Types of Solutes

• Most solutes move across the capillary wall by diffusion, which is the movement of solutes from an area of higher concentration to lower concentration.

Diffusion Through Membranes

• Lipid soluble molecules, such as oxygen and carbon dioxide, diffuse through the lipid phase of the intervening plasma membranes.

• They are able to move freely across the endothelial cells from areas of higher to lower concentration without the help of transport proteins or expenditure of metabolic energy.

Exocytosis

• Some molecules, which are not lipid soluble, are translocated across the capillary wall by cytoplasmic vesicles in a process called exocytosis.

• Proteins, which are very large molecules, are typically transported in this way. The materials would be brought into the endothelial cell via endocytosis at the side of the cell facing the lumen of the capillary. The cytoplasmic vesicle carrying the protein moves to the side of the endothelial cell facing the interstitial fluid. Then exocytosis occurs, which releases the materials into the interstitial fluid.

slide32

Clefts and Fenestrations

• Water-soluble solutes, such as amino acids and sugars diffuse from the capillary through fluid-filled clefts or fenestrations.

**

Introduction to Bulk Fluid Flows

• Bulk fluid flows, which have little to do with nutrient and gas exchanges, also occur at capillary beds.

• Note that fluid leaves the capillaries at the arterial end and returns to the capillary at the venule end.

Enlargement of True Capillary

• Bulk fluid flows are important in determining the relative amount of fluid in blood and tissue spaces.

• Interstitial fluids, including any plasma proteins which have escaped from the blood stream, enter the lymph capillaries. These leaked fluids and plasma proteins are carried back to the blood stream by the lymphatic system.

slide33

Fluid Flow

• As the amount of fluid in the tissue spaces varies, the distance that solutes must travel between the blood and tissue cells changes proportionately.

• If there is more fluid in the tissue spaces, solutes must travel farther between the blood and the tissue cells.

Hydrostatic Pressure Example

• Fluid flows represent the balance between hydrostatic and osmotic pressures acting at capillary beds. Let's look at just hydrostatic pressure (HP) first.

• Hydrostatic pressure is the pressure exerted on a fluid on the walls of its container.

Capillary Hydrostatic Pressure

• In capillaries, hydrostatic pressure is exerted by blood. Thus, capillary hydrostatic pressure (HPc) is equivalent to the blood pressure in the capillaries.

slide34

Filtration Pressure

• Capillary hydrostatic pressure (HPc) is also called filtration pressure because it forces fluid out of the capillaries. Because of friction encountered in the capillaries, the capillary hydrostatic pressure (HPc) is lower at the venule end of the bed.

• At arterial end HPc = 35 mm Hg

• At venous end HPc = 15 mm Hg

Interstitial Fluid Hydrostatic Pressure

• In theory, the hydrostatic pressure of the interstitial fluid (HPif) in the tissue spaces opposes the capillary hydrostatic pressure (HPc).

• HPif = 1 mm Hg

Lymph Capillaries

• Normally, however, there is very little fluid in the tissue spaces because fluid is quickly picked up by the lymphatic capillaries, so the hydrostatic pressure of the interstitial fluid (HPif) is very low.

Net Hydrostatic Pressure

• Net hydrostatic pressure (Net HP) is equal to the capillary hydrostatic pressure (HPc) minus the hydrostatic pressure of the interstitial fluid (HPif).

• Net HP = HPc - HPif

• Net HP forces fluid out of the capillary.

slide35

Arteriole Net Hydrostatic Pressure

• Let's determine the net hydrostatic pressure (HP) at the arteriole end of the capillary bed.

• Taking the capillary hydrostatic pressure (HPc) of 35 mm Hg minus the interstitial fluid hydrostatic pressure of 1 mm Hg gives us 34 mm Hg for the net hydrostatic pressure at the arterial end of the capillary bed.

• Fill out this equation:

__________ = ________________ - _______________

Net HP at arteriole end = HPc - HPif

Venule Net Hydrostatic Pressure

• Now let's determine the net hydrostatic pressure (HP) at the venule end of the capillary bed.

• Taking the capillary hydrostatic pressure (HPc) of 15 mm Hg minus the interstitial fluid hydrostatic pressure of 1 mm Hg gives us 14 mm Hg for the net hydrostatic pressure at the venule end of the capillary bed.

• Fill out this equation:

___________ = ________________ - _______________

Net HP at venule end = HPc - HPif

slide36

Osmotic Pressure Example

• Osmotic pressure is the "pull" on water exerted by large nondiffusable solutes like proteins.

• The higher the solute concentration, the more the solution pulls (or holds) water.

• The movement of a solvent, such as water, through a membrane from a more dilute solution to a more concentrated solution is called osmosis.

• Indicate the net movement of water with arrows as you observe the animation:

slide37

Capillary Osmotic Pressure

• Because of its high content of plasma proteins, capillary blood has a relatively high osmotic pressure (OPc) which tends to draw fluid into the capillary.

• OPc = 25 mm Hg

Interstitial Fluid Osmotic Pressure

• Interstitial fluid contains few proteins because leaked proteins (like leaked fluids) are quickly gathered up by the lymph capillaries. Hence, interstitial fluid osmotic pressure (OPif) is very low.

• OPif = 3 mm Hg

Net Osmotic Pressure

• Net OP pulls fluids into the capillary.

• The osmotic pressure in the capillaries of 25 mm Hg minus the osmotic pressure in the interstitial fluid of about 3 mm Hg is equal to the net osmotic pressure of 22 mm Hg.

• Net OP = OPc - OPif

• Fill out this equation:

_________________ = ________________ - ___________

Net OP = OPc - OPif

slide38

Net Force

• Both net hydrostatic pressure and net osmotic pressure affect fluid flows at the capillary beds. Remember that hydrostatic pressure forces fluid out of the capillary blood and osmotic pressure pulls fluid into the capillary.

• If net HP is higher than Net OP, fluid leaves the capillary.

• If net HP is lower than Net OP, fluid enters the capillary.

• Net force (Determines the direction of flow) = Net HP - Net OP

Leave or Enter at Arterial End?

• Net force (determines the direction of flow) = Net HP - Net OP

• Fill out this equation:

_______________ = ________________ - ____________

Net Force = Net HP - Net OP

• The net force at the arterial end of the capillary equals 34 mm Hg minus 22 mm Hg which equals 12 mm Hg. Since the net hydrostatic pressure is greater than the net osmotic pressure, at the arterial end of the capillary, the hydrostatic pressure wins out and fluid leaves the capillary at the arteriole end.

slide39

Net Force

• Both net hydrostatic pressure and net osmotic pressure affect fluid flows at the capillary beds. Remember that hydrostatic pressure forces fluid out of the capillary blood and osmotic pressure pulls fluid into the capillary.

• If net HP is higher than Net OP, fluid leaves the capillary.

• If net HP is lower than Net OP, fluid enters the capillary.

• Net force (Determines the direction of flow) = Net HP - Net OP

Leave or Enter at Arterial End?

• Net force (determines the direction of flow) = Net HP - Net OP

• Fill out this equation:

_________________ = ________________ - ____________

Net Force = Net HP - Net OP

• The net force at the arterial end of the capillary equals 34 mm Hg minus 22 mm Hg which equals 12 mm Hg. Since the net hydrostatic pressure is greater than the net osmotic pressure, at the arterial end of the capillary, the hydrostatic pressure wins out and fluid leaves the capillary at the arteriole end.

slide40

Notes on Quiz Questions:

Quiz Question 1. MAP and Autoregulation

• This question asks you to predict the factors that relate MAP (mean arteriole pressure) to autoregulation.

Quiz Question 2. Enhanced Blood Delivery

• This question asks you to predict what happens when the cells in a particular area require enhanced blood delivery.

Quiz Question 3. Autoregulatory Stimuli

• This question asks you to identify autoregulatory stimuli that enhance blood flow to a local area.

Quiz Question 4. Blood Delivery to Muscles

• In this question, you will be asked to identify factors that will restore blood flow to overworked muscle cells.

Quiz Question 5. Food and Capillary Exchanges

• This question allows you to predict the way various digested food molecules move from the blood to the interstitial fluid.

Quiz Question 6. Diffusion of Respiratory Gases

• This question asks you to predict the method of movement and direction of flow of respiratory gases in a capillary bed.

slide41

Quiz Question 7. Normal Fluid Flows

• This question asks you to predict the value of the various pressure that would allow a normal fluid flow.

Quiz Question 8. Hydrostatic Pressure and Osmotic Pressure of Interstitial Fluid

• This question asks you to determine why the hydrostatic and osmotic pressures of the interstitial fluid are so low.

Quiz Question 9. Abnormal Fluid Flows

• This question asks you to predict what happens when there is an abnormal fluid flow.

slide42

Study Questions on Autoregulation and Capillary Dynamics:

1. What is autoregulation?

2. Where does blood flow regulation occur?

3. Where does exchanges of materials take place between tissue cells and the blood?

4. What regulates the flow of blood into the true capillaries?

5. The build-up of certain chemical signals in an area of the body can act as a metabolic control, bringing more blood to the capillaries of the area. What two types of blood vessels do these chemical signals affect and how do they work?

6.Will the precapillary sphincters open or close in a capillary bed that is high in oxygen? Explain.

7. Will the precapillary sphincters open or close in a capillary bed that is high in carbon dioxide? Explain.

8. Will the precapillary sphincters open or close in a capillary bed that has a high pH? Explain.

9. Will the precapillary sphincters open or close in a capillary bed that is high in nutrients? Explain.

10. Why would a decreased blood pressure cause precapillary sphincters to open?

11. List three ways materials move from the lumen of the capillary into the interstitial spaces.

slide43

12. What are fenestrations?

13. How do clefts differ from fenestrations?

14. Explain how materials are moved across an endothelial cell via bulk transport.

15. Most solutes move across the capillary wall by diffusion. Define diffusion.

16. What types of solutes are able to diffuse though the plasma membranes of the endothelial cells from higher to lower concentration without the help of transport proteins or expenditure of metabolic energy. Give two specific examples.

17. What types of solutes are typically transported from the blood to interstitial fluid by exocytosis and endocytosis across endothelial cells?

18. What types of solutes are typically transported from the blood to interstitial fluid through clefts or fenestrations? Give two specific examples.

19. What process is responsible for fluid leaving the capillaries at the arterial end and returning to the capillary at the venule end?

20. (What happens if more fluid leaves the capillaries than is returned to the capillaries?

21. What two types of pressures influence fluid exchanges at capillary beds?

slide44

22. . Define hydrostatic pressure.

23. What term is used to denote the blood pressure in the capillaries?

24. What happens to capillary hydrostatic pressure as the blood moves through a capillary bed? Explain.

25. What term is used to denote the pressure of the fluid in the interstitial fluid?

26. Why is the hydrostatic pressure of the interstitial fluid (HPif) normally low?

27. (What is the net hydrostatic pressure in a capillary bed?

28. (Given the data in this picture, calculate the:

a. Net hydrostatic pressure (HP) at the arteriole end of the capillary bed.

b. Net hydrostatic pressure (HP) at the venule end of the capillary bed

slide46

29. Predict the net movement of water (osmosis) across a membrane permeable only to

water in the following situations:

a. Higher concentration of solute

inside the sac compared to outside

the sac.

b. Higher concentration of solute

outside the sac compared to inside

the sac.

c. Equal concentrations of solute on both sides.

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30. When you talk about osmotic pressure in a capillary bed, why is protein the only solute that is considered?

31. Why is the osmotic pressure of the interstitial fluid typically very low?

32. Given the data in this picture, calculate the net osmotic pressure (Net OP) in the capillary bed.

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33. What is the difference in the direction of force of net hydrostatic pressure and net osmotic pressure in a capillary bed?

34. If net hydrostatic pressure is higher than net osmotic pressure, in which direction will fluid flow?

35. If net hydrostatic pressure is lower than net osmotic pressure, in which direction will fluid flow?

36. Given the data in this picture, calculate the:

a. Net force at the arteriole end of the capillary bed.

b. Net force at the venule end of the capillary bed.

What effect does each have on the movement of fluids?

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Cardiovascular Physiology

aulas anteriores:

parte 1: Anatomy review: the heart, anatomy review: blood vessel and structure and function

parte 2: Intrinsic Conduction System, Measuring Blood Pressure and Cardiac Action Potential

parte 3: Factors that Affect Blood Pressure, Cardiac Cycle, Cardiac Output

Profa. Cristina Maria Henrique Pinto - CFS/CCB/UFSC

monitores: Vinicius Negri Dall'Inha e Grace Keli Bonafim (graduandos de Medicina)

Este arquivo está disponível em: http://www.cristina.prof.ufsc.br/md_cardiovascular.htm