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39 Cards in this Set

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  • Back
3 functions of the cardiovascular system?
1. Transport oxygen and other essential substances to tissues
2. Removal of byproducts of metabolism
3. Helps regulate hemostasis, including body temp and blood pressure
What part of the CV system serves as the primary determinant of systemic vascular resistance?
Arteries
What vessels have the most elastin?
Arteries
What vessels have the most smooth muscle?
Arterioles
Which vessels have valves?
Veins
Are all capillary beds the same?
No. Some are "leaky" (renal capillaries), while others are not (pulmonary capillaries)
Where is the majority of the body's blood volume?
Venous system
What regulates regional blood flow?
Precapillary sphincters
What are three ways that nutrients are exchanged in the capillary beds?
1. Diffusion between cells
2. Diffusion through cells
3. Transport via vesicles
What is the basic contractile unit of cardiac muscle?
Sarcomere
What is systole?
The time between the first (S1, closure of the AV valves) and second (S2, closure of the semilunar valves) heart sounds.
What are the two phases of the cardiac cycle?
Systole and diastole
What is the path that electrical signals course through the heart?
SA node --> atrial myocardium --> AV node --> His-Purkinje system --> ventricular myocardium
What ion channels are opened by depolarization of the sarcolemma membrane?
L-type calcium channels
What do ryanodine receptors do?
Calcium binds to ryanodine receptors in the sarcoplasmic reticulum, leading to calcium release from the sarcoplasmic reticulum. (Calcium induced calcium release)
What are the contractile proteins of the heart?
Myosin (thick filaments), actin (thin filaments), tropomyosin, and troponin I, C, and T
What is ventricular diastole?
An active, energy requiring process wherein the increased cytosolic calcium concentration achieved during systole results in the reuptake and efflux of calcium out of the cell.
What are the mechanisms for restoring the calcium gradient?
1. Uptake back into the sarcoplasmic reticulum (85%)
2. Extrusion to the extracellular space via the Na/Ca exchanger (5%)
3. Removal via dedicated Ca pump (1%)
4. In diseased conditions calcium can be sequestered into the mitochondria.
What is the blood pressure in each chamber of the heart, the pulmonary artery, and the aorta?
Right atrium: 0-3 mmHg
Right ventricle: 25/3 mmHg
Pulmonary artery: 25/12 mmHg
Left atrium: 0-5 mmHg
Left ventricle: 120/5
Aorta: 120/80
What are the two fundamental mechanical functions of the heart?
Eject Blood
Receive Blood
Which side of the heart has greater compliance?
Right side
What signs of congestion occur in right heart failure?
Hepatomegaly and ascites
Occurs when venous pressure exceeds 15 mmHg (normal <5 mmHg)
What signs of congestion occur in left heart failure?
Cough, labored breathing. Occurs when pulmonary capillary pressure exceeds 25 mmHg (normal <10 mmHg)
What are the five determinants of systolic performance and cardiac output?
Preload
Afterload
Myocardial contractility
Heart rate
Ventricular synchrony
What effect does increased end-diastolic volume have on contractility in a normal heart?
Increased contractility, to a point.
What are two conditions that impede diastolic filling?
Myocardial fibrosis and hypertrophy impede filling because they prevent optimal stretch by the myofibers even when filling pressures are increased.
What is afterload?
Afterload represents the sum of all those forces that oppose the ejection of blood from the ventricle into the circulation. Also called systolic tension or wall stress.
Afterload is determined by systemic vascular resistance and compliance.
What is Ohm's law?
Cardiac output (flow) = (P1-P2)/R
What is Laplace's Law?
Wall stress = (pressure x radius)/(2 x wall thickness)
What factors influence contractility?
Level of sympathetic nerve activity, the circulating concentration of catecholamines, and to some extent heart rate.
Anoxia, ischemia/fibrosis, and acidemia reduce contractility.
What determines heart rate?
The automaticity of the SA node, which is subject to autonomic regulation and other environmentsl and metabolic factors.
True or False: Ventricular dyssynchrony has little effect on cardiac output.
False. Ventricular synchrony is needed to maintain stroke volume.
What are the four phases of ventricular diastole?
1. Isovolumetric relaxation - begins when the semilunar valves close and lasts until the AV valve opens and filling of the heart begins.
2. Rapid ventricular filling - blood pours in when the AV valves open
3. Diastasis - a period of little/no blood flow that serves as a reserve to be encroached upon when heart rate increases.
4. Late filling period - associated with atrial systole
Which of the phases of ventricular diastole can be used as an indicator or diastolic function?
Isovolumetric relaxation time (IVRT). A prolonged IVRT suggests impaired relaxation.
What is ventricular compliance?
The ability of the heart to fill passively. This is determined by the volume and geometry of the chamber as well as the thickness and tissue composition of the walls.
What effect does decreased compliance have on end diastolic pressure.
Increased pressure is needed to push blood through a non-compliant heart.
What conditions could cause decreased contractility?
Myocardial fibrosis, hypertrophy
True or false: Animals with impaired diastolic function almost always have impaired systolic function as well.
False. Animals can have heart failure due to diastolic dysfunction while having normal systolic function.
How does calcium interact with the contractile proteins in the sarcomere?
Calcium binds to the troponin complex (troponin C). Troponin C interacts with tropomyosin to expose actin binding sites, enabling cross bridges to form between actin and myosin.