The Functions Of The Heart And Blood Vessels

The heart sometimes is thought of as an organ that pumps blood through the organs of the body. While this is true, it is more accurate to view the heart as a pump that receives blood from venous blood vessels at a low pressure, imparts energy to the blood (raises it to a higher pressure) by contracting around the blood within the cardiac chambers, and then ejects the blood into the arterial blood vessels. It is important to understand that organ blood flow is not driven by the output of the...

Table 93 Causes Of Hypertension

- increased systemic vascular resistance (vascular disease) - age, race, and socioeconomic status Secondary hypertension (5 to10 ) Hyperaldosteronism (primary) Pheochromocytoma (catecholamine-secreting tumor) Cushing's syndrome (excessive glucocorticoid secretion) has led some investigators to suggest that the basic underlying defect in hypertensive patients is an inability of the kidneys to adequately handle sodium. Increased sodium retention could account for the increase in blood volume....

Review Questions

Please refer to appendix for the answers to For each question, choose the one best 1. During a moderate level of whole-body exercise (e.g., running), a. Arterial pulse pressure decreases owing to the elevated heart rate. b. Sympathetic-mediated vasoconstriction occurs in the skin. c. Systemic vascular resistance increases owing to sympathetic activation. d. Vagal influences on the sinoatrial node are inhibited. 2. One important reason why stroke volume is able to increase during running...

Ventricular Hypertrophy

Eccentric Concentric Hypertrophy

Ventricular hypertrophy i.e., increased ventricular mass occurs as the ventricle adapts to increased stress, such as chronically increased volume load preload or increased pressure load afterload . Although hypertrophy is a physiological response to increased stress, the response can become pathological and ultimately lead to a deterioration in function. For example, hypertrophy is a normal physiological adaptation to exercise training that enables the ventricle to enhance its pumping capacity....

Info

Vagal Innervation Vessel

FIGURE 6-3 Adrenergic and muscarinic receptors in the heart and blood vessels. Norepinephrine NE released from sympathetic nerve terminals binds to postjunctional adrenoceptors in the heart subtype affinity to NE p1 gt gt p2 and a1 to produce positive inotropy, chronotropy, and dromotropy. In blood vessels, NE binds to postjunctional adrenoceptors subtype affinity to NE a1 gt gt a2 and p2 . NE binding to postjunctional a-adrenoceptors causes vasoconstriction, whereas binding to -adrenoceptors...

Normal Cardiac Presure

Heart Chambers Pressures

The seven phases of the cardiac cycle are 1 atrial systole 2 isovolumetric contraction 3 rapid ejection 4 reduced ejection 5 , isovolumetric relaxation 6 rapid filling and 7 reduced filling. LV, left ventricle ECG, electrocardiogram a, a-wave c, c-wave y, v-wave AP, aortic pressure LVP, left ventricular pressure LAP, left atrial pressure LVEDV, left ventricular end-diastolic volume LVESV, left ventricular end-systolic volume, S1-S4, four heart sounds. the left...

Of Blood Flow

Pgi2 Dilation

Tissues and organs have the ability to regulate, to a varying degree, their own blood flow. This intrinsic ability to regulate blood flow is termed local regulation and can occur in the complete absence of any extrinsic neurohumoral influences. For example, if a muscle is removed from the body, perfused under constant pressure with an oxygenated salt solution, and then electrically stimulated to induce muscle contractions, the blood flow increases. The increase in blood flow occurs in the...

Venous Blood Pressure

Venous Compliance

Venous pressure is a general term that represents the average blood pressure within the venous compartment. A more specific term, central venous pressure, describes the blood pressure in the thoracic vena cava near the right atrium. This pressure is important because it determines the filling pressure of the right ventricle, and thereby determines ventricular stroke volume through the Frank-Starling mechanism as discussed in Chapter 4. Several factors influence central venous pressure cardiac...

The Arrangement Of The Cardiovascular System

The Arteries Systemic Circulation

The cardiovascular system has two primary components the heart and blood vessels. A third component, the lymphatic system, does not contain blood, but nonetheless serves an important exchange function in conjunction with blood vessels. The heart can be viewed functionally as two pumps with the pulmonary and systemic circulations situated between the two pumps Fig. 1-1 . The pulmonary circulation is the blood flow within the lungs that is involved in the exchange of gases between the blood and...

Conduction Of Action Potentials Within The Heart

Intrinsic Conduction System Heart

Electrical Conduction within the Heart The action potentials generated by the SA node spread throughout the atria primarily through cell-to-cell conduction Fig. 2-10 . FIGURE 2-10 Cell-to-cell conduction. Cardiac cells are connected together by low-resistance gap junctions between the cells, forming a functional syncytium. When one cell depolarizes, depolarizing currents can pass through the gap junctions and depolarize adjacent cells, resulting in a cell-to-cell propagation of action...

Cardiac Cell Structure And Function

Troponin Tropomyosin

Cardiac myocytes represent a type of striated muscle, so-called because crossbands or cross striations are observed microscopically. Although cardiac muscle shares some structural and functional similarities with skeletal muscle, it has several important differences. Cardiac myocytes are generally single nucleated and have a diameter of approximately 25 m and a length of about 100 m. In contrast, although some types of skeletal muscle myo-cytes may have a similar diameter, their cell lengths...