Structure and function of the cardiovascular system self-study Flashcards Preview

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What are the normal values for the variables listed?


What is heart failure? What kinds of diseases may cause heart failure and what effects do they have on CO (which part of CO specifically)? Why is heart failure often called congestive heart failure?

Heart failure is a reduced capacity of the heart to pump blood. It may a manifestation of may different cardiac diseases including MI, coronary atherosclerosis, cardiomyopathies, valvular heart disease, HTN, and congenital heart diseases. These conditions can affect the determinant of stroke volume e.g. heart failure can result from decreased contractility and/or increased afterload. A common result is fluid retention which leads to an increased cenral venous pressure. This helps to compensate for the impared function of the heart by increasing ventricular filling (which increases stroke volume). However, high venous pressure leads to edema formation and congestion, hence the common term congestive heart failure. 


What are the 2 types of cardiomyopathy?

dilated cardiomyopathy (what case study pt has)

hypertrophic cardiomyopathy


How is hypertrophic cardiomyopathy characterized? What are some of its symptoms/associated diseases? What mutations lead to this disease (when it is inherited) and what do the mutations result in at the cellular level?

Hypertrophic cardiomyopathy causes cardiac muscle cells to grow larger and results in thickening of the walls of the heart. The affected heart does not relax well during the filling phase of the cardiac cycle. It can either be inherited or acquired. Macroscopically, HCM is characterized by increased left ventricular mass (particularly interventricular septum) and is histologically characterized by myofibrillar and myocyte disarray. The myocytes often have bizarre shapes and are arranged in chaotic patterns. These disorganized cells in the ventricle may impair transmission of the AP and predisopose the heart to arrythmias. Additionally, pts may have dyspnea, palpitations, chest pain, syncope, heart failure, or sudden deat, although pts are frequently asymptomatic. Hereditary hypertrophic cardiomyopathies arise from genetic mutations of the sarcomeric contractile proteins, including myosin, tropomyosin, and troponin. These mutations cause muscles to shorten much more slowly than usual with greatly reduced power output so muscle cells enlarge to compensate. 


How is dilated cardiomyopathy characterized? What mutations lead to this disease (when it is inherited) and what do the mutations result in? What is the most common inheritance pattern?

Dilated cardiomyopathy (DCM) is characterized by ventricular dilation, increased ventricular volume, and systolic dysfunction. About 30% of all DCM cases are inherited with autsomal dominant inheritance being most common. Hereditary DCM is apparently most commonly caused by a weakening of the myocyte cytoskeleton. Mutations of the genes encoding dystrophin and dystrophin glycoprotein complex have been shown to produce DCMs. Dystrophin and the DGC are thought to play a vital role in muscle by forming connections between the internal cytoskeleton and/or sarcomeric structure and the extracellular matrix surrounding the muscle cells; mutations can 
cause problems with force transmission and general muscle cell and membrane integrity. 


What are the general fxns of the cardiovascular system?

Transport system that supplies every cell in teh body with required nutrients and removes cells' waste products. Also participates in mechanisms such as temp regulation, humoral communication, and adjustment of O2 and nutrient supply in diff physiological states. 


True or false: The cardiovascular system normally provides each tissue and organ with the blood flow that it 
requires to sustain its metabolism and to carry out its particular special function(s). It must respond:
1) to the fact that the activity of each tissue and organ varies both acutely (short-term) and chronically (i.e. long-term)
2) to pathology that can give rise to changes in tissue or organ function.

True. For example, the cardiovascular system (CVS) needs to be able to respond to both the short-term, 
immediate stress of exercise along with the long-term, gradually developing stress of chronic heart failure. It does this in a variety of different ways.


The CV system is made up of a positive pressure pump, the ____, and a set of blood vessels, the ____, that carry blood to every cell, tissue, and organ.




The heart is a muscular pump which is actually two pumps in ___. The contraction of the left and right heart produces ____ ___ in the blood vessels.

1. series

2. elevated pressure


True or false: The blood vessels into which the heart pumps are elastic and thus maintain a non-zeoro pressure in the circulation at all times. 



Because blood flows from high to low pressure and the rate of flow is proportional to the pressure difference, what is the consequence of the heart pumping with more force?

A greater pressure difference resutls within arteries, and therefore, more flow results. Ohm's Law


Flow is inversely proportional to _____.

resistance. Ohm's law


True or false: Flow is distributed to the various organs to meet physiological needs by maintaining a more of less constant pressure gradient across the circulation 
and varying the resistance to flow of each tissue or organ.



In order to maintain appropriate flow to all parts of the body in the face of changing needs and physiological disturbances, what 2 parameters does the CV system regulate? How does the CV system regulate these parameters? What is the difference btwn a regulated and controlled parameter? Give an example in the body.

The CV system regulates (holds more or less constant) mean arterial pressure (MAP) and blood volume (BV). It does this through sensory receptors that measure MAP and BV. All other CV parameters are controlled in a manner that contributes to regulating MAP and BV. For example, baroreceptors in the carotid sinuses in the aortic arch sense changes in blood pressure and reflexively elicit inverse changes in heart rate. MAP is regulated (i.e. the body tries to keep it constant), HR is controlled by the body to maintain the regulated parameter. 


Describe the anatomy of the aorta, arteries, arterioles, capillaries, venules, and veins as it relates to diameter, thickness, and contents (endothelium, elastic tissue, smooth muscle, fibrous tissue).

• The aorta has a large diameter, thick walls, has a high 
percentage of elastic tissue.
• The arteries are of intermediate diameter, thick walled, and have a high percentage of smooth muscle.
• The arterioles are of small diameter, relatively thick 
walled, and have a high percentage of smooth muscle. They are the stopcocks of the body: control flow to tissues by adjusting degree of contraction (decreases radius, increases resistance).
• Capillaries are small in diameter, have walls one cell 
thick and are the level on which nutrient exchange takes place.
• Venules are small in diameter, have thicker walls and are mostly fibrous tissue.
• Veins are large in diameter, have thick walls and are 
largely smooth muscle.


Blood entering the right ventricle through the right atrium is pumped through the pulmpnary arterial system at a mean pressure of about ______ of the systemic arteries.


Pulmonary artery pressure (s/d/m) 25/7/13 mmHg

Aortic pressure (s/d) 120/70 mmHg


Pressures in the body are expressed relative to _____ pressure. Negative pressures (which exist in the thorax) merely represent pressures that are less than ____ (same as previous blank) pressure. 

atmospheric. 100 mg of Hg is 100 mmHg greater than atmospheric pressure.


How does flow change as you go from the aorta, to arteries, to arterioles, etc.?

It doesn't! The flow, which is the sum of the movement of blood in all of the vessels in a particular section of the circulation, is the same in all parts of the system. The flow of blood in the aorta is equal to the flow of blood in all of the little capillaries (when added all together).


Remember that the flow in any system is directly proportional to the pressure gradient and is inversely proportional to the resistance. If there is a large pressure difference form one end of a particular class of vessels to another, what does this mean for resistance?


If there is a large pressure gradient from one end of a class of vessels to another, there is large resistance to flow. 



So, if flow is constant when the resistance goes up, the pressure difference rises as well. 


What is the pressure in the aorta as compared to arteries and what does this mean for resistance? Where in the vascular system is there a pressure difference? How is this pressure difference obtained and why? How does this effect pressure in vasculature that come after it?

Pressure is generally maintained from the aorta to the larger arteries which means that resistance is relativley small. The arterioles are the principal points of resistance to blood flow in the circulatory system. These vessels are primarily responsible for regulating flow into organs and tissues and they increase resistance through vasoconstriction (decreasing radius). Because the resistance in this section is relatively high, there is a large pressure drop across this class of vessels. That is, it takes a large pressure gradient to drive the flow through the high resistance arterioles. On the other hand, it takes a small pressure difference to drive the same flow through the low resistance arteries and veins. Since the pressure drops so much across arterioles, the hydrostatic pressure is low in capillaries and is even slightly lower in venules and veins. 

Note that flow cannot take place without some kind of pressure gradient. Although it appears presure is the same in the aorta and arteries, it must (and does) drop. 


Veins are more compliant than arteries. What is compliance? What anatomical differences lead veins to be more compliant?

Compliance: meausre of stretchiness. Measured by determining  Δvolume/Δpressure (that is, the 
change in volume that is observed for each unit change in observed pressure). If I blow up a balloon, 
the pressure inside goes up. As this happens, there is a measurable increase in the balloon volume. 
Its walls have a relatively high compliance. If I blow into a container made of steel, the pressure 
will go up but the volume will not increase very much. The walls of the steel container have a relatively low compliance.

Arteries and arterioles have relatively thick, muscular walls and veins and venules have relatively 
thin walls. It therefore makes sense that it would take less pressure to increase the volume of a vein 
and, indeed, it does. You may also think of it the other way, it takes more volume to increase the 
pressure in a vein. Veins are therefore considered to be more compliant than arteries.


In what vessels is most of the blood volume contained? What property of these vessels allows them to store so much blood?

Most (2/3) of the blood volume is to be found in the venous compartment. This is by far the vascular compartment with the most blood. Indeed, whereas the arteries are often referred to as “resistance vessels” because of their regulatory role, the veins are often referred to as “capacitance vessels” because of their role in storage of blood as a reserve. The high compliance of the veins makes this storage function possible as the veins can keep large volumes of blood at relatively low pressure.

Note that very little blood is contained within arterioles. Blood volume within the arteriolar compartment therefore does not change a great deal when they contract.


What are the differences btwn velocity of blood flow and rate of blood flow in a vessel? How is velocity of blood flow calculated? 

The velocity of blood flow is NOT the same as the rate of flow in a blood vessel. The velocity of blood flow is perhaps better designated as the "linear velocity" which refers to the rate of displacement with respect to time (cm/s). The flow or "volume flow" has the dimensions of volume per time (ml/s). The linear velocity is related to the flow and cross sectional area (cm2):

Q=v x A


As cross-sectional area decreases, velocity increases. 


How does velocity change as blood travels through the aorta and to increasingly smaller vasculature?

As shown in Figure S.8, the velocity decreases progressively as the blood travels through the aorta, 
progressively through the smaller and smaller branches to the arterioles. Note that the total flow is constant (top panel) through out the system. A minimal value is reached at the level of the capillaries. As the blood traverses the venules to the veins and the vena cavae, the velocity gradually increases again. The relative velocities in each of these components are related to their total cross-sectional areas. Note that though the cross-sectional area in each individual capillary is 
small, there are so many that the sum total cross-sectioanl area of the compartment (i.e. all of the 
capillaries added together) is relatively large. The larger the total area, the smaller the velocity!


True or false: Compliance is more or less constant over the range of physiological pressures.



Fill in this table. 


What are the 3 functions of the arterial compartment of the cardivascular system?

1. Creation of the elevated pressure head that brings about continuous perfusion of tissue. This elevated pressure is actually generated by the heart, which forces a large volume of blood into the aorta and its branches. The pressures within the aorta and the arterial branches from it are very large and it’s this pressure which drives the flow of blood.
2. Containment and transport of blood ("conduit" function). The arteries carry the blood from the heart to the general vicinity of the organs which need it.
3. Control of the resistance to flow (in individual pathways and in the CV system as a whole). The 
arterial system distributes blood to the capillary beds throughout the body through the action of the 
arterioles which constrict to raise resistance and restrict flow to the bed and dilate to decrease resistance and increase that flow


What is hydraulic filtering? What effect does this have on capillaries?

Hydraulic filtering is the process by which the distensibility of the aorta and the arteries converts 
the intermittent output of the heart into continuous (but pulsatile) tissue perfusion (Figure S.9). 
Thus, the rapid ejection of blood from the heart is converted to a continuous flow. Here’s how it works. The entire stroke volume of the heart is ejected into the arterial system in about 300 ms or approximately the first 1/3 of the cardiac cycle. Most of this is ejected in the first 150 ms or so. While the flow to the capillaries increases some during this phase, it doesn’t increase 
enough to compensate for the increased flow into the arteries as the heart contracts - nor would we 
want it to. A slower, steadier flow will be more efficient for nutrient exchange.

Therefore, in order to compensate for this rapid ejection of blood, the arterial walls stretch and the volume increases. During diastole, the elastic recoil of the arterial walls continues to maintain a pressure head which results in sustained capillary flow. As the volume drops, the pressure gradually declines but slowly. The resultant pressure wave in the arterial compartment is illustrated in Figure S.10.


What determines pressure within arteries? State the equation. What determines the volume of blood in the arteries?

Recall that compliance of a vessel is the rship btwn volume and pressure (∆V/∆P). The pressure in the 
arteries is determined by the volume of the fluid contained within the arteries and by their compliance

C= ∆V/∆P

∆P= ∆V/C

In turn, the volume within the system is determined simply by the amount of fluid entering and the amount of fluid leaving the system. The amount of fluid entering is the cardiac output. The amount leaving the system is determined by the flow of blood through the resistance vessels (the terminal 
arterioles). If the inflow exceeds the outflow, the arterial volume increases and the arterial walls are 
stretched more and pressure rises. When the outflow exceeds the inflow, pressure declines. This is 
effectively what is happening during the pressure wave in Figure S.10, which shows the features of 
the aortic (arterial) pressure pulse wave. Note: Although the pressure in the left ventricle fluctuates 
between essentially 0 and 120 mm Hg, the pressure in the aorta fluctuates between 80 and 120 mm Hg


What is mean arterial pressure (MAP)? What two ways may it be calculated? Why is MAP important?

MAP is the average, over the time of one cycle, of arterial pressure. The approximate value of MAP can be calcuated from the systolic (Ps) and diastolic (Pd) blood pressure values:

MAP=PD + (PS-PD)/3

MAP is important bc it describes, in one term, the average pressure on the arterial side of the circulation. 

Refer to attached diagram. Blood flows from right to left as you look at the diagram. The high, arterial pressure drives that flow in the direction of the low venous pressure. In between we have sources of resistance which control the flow to the individual tissues and organ systems (Circled with heavy, black lines). If we consider the total effect of all of the individual resistances upon the systemic circulation as a whole from right to left, arterial to venous, we can lump them together as one number, the total peripheral resistance or TPR. Therefore, over the entire circulatory system:
1) is the pressure in the arterial system or the MAP
2) is the pressure in the venous system (PV)
3) is the cardiac output (CO)
4) is the total peripheral resistance (TPR) 



But, Pv is normally very smal and more or less constant and hence it can usually be ignored. Therefore , we can write: