Blood Vessels

17. Why does blood flow decrease so drastically in the small arteries and arterioles? (2 reasons)

1. blood flow is according to needs 2. disperses to a larger area

27. List the four routes of passage out of a capillary in to the ECF.

1. lipid-soluble solutes diffuse through plasma membrane (gases) 2. water-soluble substances leave the blood/cells within vesicles by endo/exocytosis 3. Intercellular clefts allow limited passage of fluids/solutes. 4. Very free passage of small solutes and fluids is allowed by fenestrated capillaries, found where absorption is a priority or where filtration occurs. Fenestra is more permeable than other portions of the plasma membrane.

3. Which are thicker, arteries of veins? Why? Why is it important for arteries to have enhanced musculature? Do arteries expand or contract during systole? During diastole?

Arteries are thicker and the tunica media is heavier to expand as blood is forced into them and then recoil passively as the blood flows off into the circulation during diastole. Walls must be strong and stretchy to take continuous changes in pressure.

20. How do the kidneys alter blood volume? More water retained means what for SVR and CO? Less water retained means what for SVR and CO?

As bp increases beyond normal, the kidneys allow more water to leave the body in the urine. Since the sourve of this water is the bloodstream, the blood volume decreases which in turn decreases blood pressure.

A. Systemic Arteries 1. Major Arteries of the ascending Aorta and Aortic Arch

Ascending aorta Right and left coronary arteries Aortic arch Brachiocephalic trunk R and L common carotid arteries R and L subclavian arteries

23. What do baroreceptors measure? Know the two locations for BP baroreceptors. The baroreceptors in the arch of the aorta are part of a reflex that controls what aspect of BP? The baroreceptors in the arch of the aorta are part of a reflex that controls what aspect of BP? Know that together these two receptors monitor and control everyday BP.

Baroreceptors are mechanoreceptors located in the carotid sinus and in the aortic arch. Their function is to sense pressure changes by responding to change in the tension of the arterial wall. The baroreflex mechanism is a fast response to changes in blood pressure.

1. Big picture: What direction does blood flow in arteries? In veins? What is the role of capillaries? What is an arteriole? A venule? Where do they fit into the picture? Draw a simple diagram to illustrate the five types of vessels we discussed in class.

Blood flows from the heart into arteries then into smaller arteries-then arterioles-then capillary beds which are drained by venules which empty into veins that finally empty into the great veins entering the heart. Arteries carry blood away from the heart and veins carry blood toward the heart. Capillaries connect small arteries to small veins and directly serve the tissue.

32. What is bulk flow? List the four pressures that cause bulk flow. Explain the concept of hydrostatic pressure. Explain the concept of osmotic pressure. Be able to draw the bulk flow diagram as we did in class from memory. Label the artery, the vein, the capillary. Show the area where net movement of fluid is into the capillary. Show the area where the net movement is out of the capillary. At each of these locations know which pressures are at work and in which direction.

Bulk flow is a movement of molecules from an area of high pressure to an area of low pressure. In cell biology, it refers to the transport of fluids or electrolytes between cells through openings, or pores, between the cells.

9. With respect to the hepatic portal system - Draw a simple diagram of the hepatic portal system. What is its' purpose? Where do it's two capillary beds lie? What is moved into / out of the capillary at each capillary bed? What is the nickname for the liver? Explain. What is meant by the terms fed state and fasted state?

Drain the digestive organs, spleen and pancreas and deliver this blood to the liver through the hepatic portal vein to ensure the liver processes substances (glucose, fat, protein) before they enter the systemic circulation. Some can be stored for later. The fed state refers to the period following a meal and is characterized by high levels of nutrients in the blood. There are high circulating levels of a family of simple sugars, the most important being glucose. The fasted state is when your body needs to rely on endogenous sources of energy (i.e. glycogen, fat, protein) rather than from exogenous sources (i.e. from food absorbed in the gastrointestinal tract), which starts about 12h after the last meal.

21. Know that renin is released from the kidney in the case of low blood pressure.

Enzyme. Triggers chemical reactions that result in the formation of a vasoconstrictor and also stimulate the adrenal cortex to release aldosterone, a hormone that enhances sodium reabsorption by the kidneys. As sodium moves into the blood, water follows thus bp/blood vol rise.

25. Be able to explain the neural control of blood pressure using the diagram from class. Know the steps for low BP and for high BP. In each case know how the SNS and the PNS affect HR, contractility and vessel diameter. BE SURE TO KNOW THAT IN CASES OF LOW BLOOD PRESSURE - CO NEEDS TO INCREASE (and the other way around.)

HIGH BP signs: High blood pressure is often associated with few or no symptoms. •dull headaches •dizzy spells •frequent nosebleeds LOW BP signs: •Dizziness or lightheadedness •Fainting (syncope) •Lack of concentration •Blurred vision •Nausea •Cold, clammy, pale skin •Rapid, shallow breathing •Fatigue •Depression •Thirst

16. Again, define MAP. How is MAP calculated? Explain why it's closer to diastolic than systolic pressure. Know the normal clinical value for MAP.

MAP = (CO x SVR) + CVP

5. What is meant by the term capillary bed? The term microcirculation? List and explain the five components of a capillary bed. Explain how precapillary sphincters and vascular shunt work together to route blood flow.

Network of interweaving capillaries. The flow from arteriole to a venule is through a capillary bed, called microcirculation. A vascular shunt connect the arteriole and venule at opposite ends. True capillaries actually serve the tissue with gas exchange and branch off from the shunt. The precapillary sphincter surrounds the root of each true capillary and acts as a valve to regulate the flow of blood into the capillary. Blood either goes through the true capillaries or through the shunt. If the sphincter is relaxed (open), blood flows through the capillaries and takes part in exchanges with tissue cells. When the sphincters are contracted (closed), blood flows through the shunts and bypasses the tissue cells.

28. Which substances cross the capillary membrane directly? List two examples.

Oxygen, nutrients, carbon dioxide, wastes, steroids

24. What do chemoreceptors measure (in general)? Know the two locations for BP chemoreceptors. Know that together these two receptors monitor and control BP problems due to blood volume emergencies. What three specific chemicals do the BP chemoreceptors notice? What do these three chemicals have to do with blood pressure?

Peripheral chemoreceptors (or carotid and aortic bodies) are so named because they are sensory extensions of the peripheral nervous system into blood vessels where they detect changes in chemical concentrations. oxygen, carbon dioxide, pH

C. Pulmonary Circulation (p. 497)

Pulmonary trunk R and L pulmonary arteries R and L pulmonary veins

2. Major Veins Draining the Head and Neck (p. 491)

R and L internal jugular veins R and L external jugular veins R and L vertebral veins R and L brachiocephalic veins

26. Draw a simple diagram of a capillary bed. What is the function of the ECF in a capillary bed?

Substances move to/fro the body cells according to their concentration gradients

B. Systemic Veins 1. Veins Carrying Blood to the Right Atrium (p. 490)

Superior vena cava Inferior vena cava Coronary sinus

15. What does systolic blood pressure measure? What does diastolic blood pressure measure? Know the normal clinical value for systolic and diastolic blood pressure.

Systolic-the pressure in the arteries at the peak of ventricular contraction 120 Diastolic-the pressure when the ventricles are relaxing 80

11. Does MAP drive or resist blood flow? Increase or decrease CO? Does SVR drive or resist blood flow? Increase or decrease CO?

The mean arterial pressure (MAP) is a term used in medicine to describe an average blood pressure in an individual.[1] It is defined as the average arterial pressure during a single cardiac cycle.

6. What is the function of a capillary? Explain how the form of a capillary fits its function.

Thin walls allow for diffusion to tissue easily.

4. Describe the wall of a capillary? It is made of only one tunic - which one? How many cell layers is it?

Tunica interna which is very thin to allow exchanges of gas easily between blood and tissue cells.

13. List three factors that affect SRV. Know how each affects SVR.

Vascular resistance is the resistance that must be overcome to push blood through the circulatory system and create flow.

18. What is meant by the term vasoconstriction? How is it accomplished? Explain the effect of vasoconstriction on vessel radius, SVR and CO (flow).

Vasoconstriction is the narrowing of the blood vessels resulting from contraction of the muscular wall of the vessels, in particular the large arteries and small arterioles

22. Name the two mechanisms for nervous control of blood pressure. Know that both of them are negative feedback mechanisms. List and explain the 5 components of a reflex mechanism.

Vasoconstriction: increases bp Vasodilation: decreases bp Reflex mechanism:

7. Why are veins thinner than arteries? Why is it not necessary for veins do not have enhanced musculature? List three mechanisms which help veins return blood to the heart under low pressure and against the pull of gravity? Explain how each of the three works.

Veins are far from the heart and the pressure is low so the veins don't need thicker walls. Veins are modified to ensure venous return equals cardiac output at any time. Skeletal muscles contract and relax and milk the blood back towards the heart. The respiratory pump causes a drop in pressure the causes the veins to expand and fill, which also helps blood return to the heart. Valves?

19. What is venous tone? What is the effect of high venous tone on SVR and CO? What is the effect of low venous tone on SVR? On CO?

Venous tone is a property of the venous system which reflects the venous resistance and pressure. An increased venous tone caused by venoconstriction leads to an increased net capillary filtration by increasing the venous resistance and venous pressure.

31. What is a fenestration? What is a fenestrated capillary? List three examples of locations which utilize fenestrated capillaries

Very free passage of small solutes and fluids is allowed by fenestrated capillaries, found where absorption is a priority or where filtration occurs. Fenestra is more permeable than other portions of the plasma membrane.

29. What substances utilize vesicles to move from the capillary to the ECF? What is endocytosis? Exocytosis?

Water-soluble substances (glucose, amino acids, insulin)

What is meant by the term vasodilation? How is it accomplished? Explain the effect of vasodilation on vessel radius, SVR and CO (flow).

refers to the widening of blood vessels. It results from relaxation of smooth muscle cells within the vessel walls, in particular in the large veins, large arteries, and smaller arterioles. reduces bp

30. What substances move from the capillary to the ECF via intercellular clefts? These clefts are found everywhere in the body except one place. Where is that?

sodium, potassium, NOT in the brain