CARDIAC OUTPUT C O Cardiac output C O

CARDIAC OUTPUT (C. O. ) Cardiac output (C. O. )is the volume of blood pumped by each ventricle into the circulation, per unit time. Definitions: 1 -Stroke Volume(S. V) is the volume of blood pumped by each ventricle per beat, averages 6070 mlbeat, at rest. 2 -Minute volume is the volume of blood pumped by each ventricle per minute. It equals the product of the S. V and HR, under basal conditions. The averages 5 -6 L=C. O

CARDIAC OUTPUT (C. O. ) 3 -End systolic volume is volume of blood remains in the ventricle at the end of ventricular systole , it is about 50 ml. 4 -End diastolic volume is the volume of blood present in the ventricle at the end of diastole and before the onset of the next systole, it equal about 120 ml.

CARDIAC OUTPUT (C. O. ) Distribution of the cardiac output: 1 -Kidney-1300 mlmin. 2 -Brain-700 -800 mlmin. 3 -Coronary-200 mlmin. (800 ml in exercise) 4 -Muscle-600 -900 mlmin. 5 -Liver-about 1. 5 Lmin.

CARDIAC OUTPUT (C. O. ) C. O. in various conditions: No changes –Sleep, moderate changes in environmental temperature. Increase -Anxity&excitement(50 -100%) -Eating(30%) -Exercise(700%) -High environmental temperature. -Epinephrine. Decrease -Sitting or standing from lying position(20 -30%) -Rpid arrhythmia, heart disease.

CARDIAC OUTPUT (C. O. ) Factors controlling cardiac output A)The rate of the venous return(V. R): Factors that influence the V. R: 1 -The venous pressure gradient: In the recumbent position the venous blood pressure gradient is about 15 mm. Hg, during quiet expiration &about 20 mm. Hg during quiet inspiration. This is because the venous pressure in the start of venule=12 mm. Hg, and in the vein just outside the chest cavity=0 mm. Hg. Veins which are inside the chest cavity the venous pressure is -3 mm. Hg during quiet expiration and -8 mm. Hg during quiet inspiration.

CARDIAC OUTPUT (C. O. ) 2 -The respiratory movements: Inspiration increases both the –ve intrathoracic pressure and the +ve intra abdominal pressure. Thus it helps the passage of blood towards the heart. 3 -Voluntary muscle contraction and tone: The contraction of voluntary muscle squeezes the blood from the capillaries and small veins at lie between the fibers. (Voluntary muscles, acts as peripheral hearts, the activity of which is essential for maintaining the circulation against the earth's gravity).

CARDIAC OUTPUT (C. O. ) 4 -Arteriolar diameter: Arteriolar dilatation in the body makes faster the blood from arteries to veins, thus the V. R&C. O. are increased. During digestion the C. O. might show about 30% increase because of arteriolar dilation in the splanchnic area In hot weather the dilatation of the cutaneous arterioles increases the V. R about 10%. Constriction of the arterioles would diminish the V. R. provided the A. B. P does not sufficiently rise to overcome the increased P. R. Adrenaline increases the C. O. due to its net vasodilator effect while noradrenaline decreases the C. O. because of its marked vasoconstrictor action.

CARDIAC OUTPUT (C. O. ) 5 -The tone of the capillaries: -About 90% of the total capillaries in the body are completely closed. -The open capillaries are often not fully dilated. -Capillary tone refer to the number of partially or totally closed capillaries. -It is most essential for an adequate V. R, a normal C. O. &a normal ABP. -If all the capillaries in the body were dilated, they would accommodate the total blood volume and little or no blood would return to the heart. The C. O. would drop to a fatal level (shock). The shock that occurs in man after sever burns or extensive surgical operations and tissue injury is due to the release of histamine like substances from the damaged tissue.

CARDIAC OUTPUT (C. O. ) 6 -Venomotor tone: This is vasoconstrictor sympathetic discharge from the vasoconstrictor neurons of the CVCs to the muscular coat of veins, preventing their distention which is very dangerous. Veins have a great capacity and they contain more than 60% of the total blood volume. In case the venomotor tone is much lowered much blood would stagnate in the veins and the V. R &C. O. are markedly reduced. 7 -Contraction of the spleen and other blood reservoirs: Contraction of the spleen, ejects its store of blood into the circulation and increases the V. R.

CARDIAC OUTPUT (C. O. ) B)The effect of H. R on the C. O. Moderate changes in the heart rate have no effect on the minute volume, which remains equal to the V. R. S. V increases when the H. R slow, and decreases when the H. R accelerates. H. R. bmin. S. V. C. O. 25 120 3 L 60 80 4. 8 L 80 60 4. 8 L 100 48 4. 8 L 120 40 4. 8 L 200 15 3 L

CARDIAC OUTPUT (C. O. ) In paroxysmal tachycardia (rate 200)the diastolic periods are shortened to a great extent than the systolic periods →↓C. O&↓S. V. (15 ml)&C. O=3 L. When the V. R is increased as in muscular exercise, the ↑H. R becomes of importance in increasing the C. O. C)The effect of the ABP: The heart is capable to strengthen its contraction by increasing its diastolic volume(Starling Law).

CARDIAC OUTPUT (C. O. ) D)The effect of myocardial strength: Starling law of the heart represents an important mechanism of cardiac reserve power. Weakening of the myocardium may be caused by : Hypoxia, hypercapnia. acidosis, ether, chloro form, bacterial toxins and vitamin B deficiency, the most common cause for myocardial weakness is cardiac ischemia.

The cardiac reserve Definition: The difference between the work of the heart in maximal activity and its work under basal conditions is known as the cardiac reserve. Mechanisms of cardiac reserve: 1 -Acceleration: increase HR from 70 -200 bmin. 2 -Dilatation: Starling law…. 3 -Hypertrophy

The Blood Pressure Blood pressure is the lateral pressure exerted by the blood on the vessel walls while flowing through it. Four terms in common use: 1 -Systolic pressure(S. P): The maximum pressure during systole=120 mm. Hg 2 -Diastolic pressure(D. P): The minimum pressure during diastole=80 mm. Hg 3 -Pulse pressure(P. P): The difference between systolic and diastolic p. =40 mm. Hg. 4 -Mean pressure(M. P): is the average P throughout the cardiac cycle=D. P+(13 XPP)=80+(13 X 40)=93 mm. Hg.

The Blood Pressure Physiological variation: 1 -Age: B. P rises with age. 2 -SEX: Women have a slightly lower B. P than men. 3 -Build: The systolic pressure is usually high in obese persons. 4 -Exersise: ↑S. P&↔ or↓D. P. 5 -Meals: The blood pressure rises slightly after meals (5 -10 mm. Hg. ) 6 Sleep: The systolic pressure falls by about 15 -20 mm. Hg.

The Blood Pressure Regulation of arterial diameter The plain muscles of the arterioles are arranged circularly and act as sphincters, they are under control of: 1 -CVCs→sympatetic tone Factors influence the CVCs: a-From the baroreceptors b-Pressor impulses from the right atrium. d-Other afferent: -Painful stimuli -Voluntary muscles. -Exposure to air currents -A cold shower

The Blood Pressure 2 -The chemical composition of the blood affecting the directly. -Metabolites(CO 2, Lactic acids…………………. ) -Ach, adrenaline, angiotensin II. ADH Renin-Angiotensin-Aldosterone

The Blood Pressure 2 -The chemical composition of the blood affecting the directly. -Metabolites(CO 2, Lactic acids…………………. ) -Ach, adrenaline, angiotensin II. ADH Renin-Angiotensin-Aldosterone

The Blood Pressure Renin angiotensin aldosterone l Aldosterone l Cortisol l Nor adrenaline l Adrenalne l. ADH l estrogen & progestrone l Ca++ l

The Blood Pressure l A. Ch l Bradikinin l ANP l HISTAMINE l PGs l (k, Mg, h)Ions l waste products l

l Measurment of ABP l -PALPATION METOD l -AUSCALTATION METHOD l

EFFECT OF MUSCULAR EXERCISE ON l CIRULATION A-General effects: l 1 -Increased heart rate (conditional l reflex, stim. RC, Chemoreceptors, Bainbridge reflex, Increaesd blodd temperature, Alam smirk reflex, secretion of adrenaline).

2 -Increased V. R(Contraction of l muscles, respiration, increased blood volume. 3 -Increased coronary blood flow(cardiac l metabolites, adrenaline) 4 -increased S. V. (due to increased coronary l blood flow, adrenaline that increased contractility, starling low due to increased V. R)

5 -Increased C. O(Due to increased l : HR&V. R) 6 -Increased ABP(due to increased l : C. O, CO 2&H+, &impulses from contracting muscles)

LOCAL EFFECTS l 1 -Icreased blood flow to active l musclse&dilatation of arterioles(Co 2&H. ) 2 -Increased O 2 supply to active muscles l (shifting to right in O 2 dissociation curve)

CARDIAC METABOLISM AND WORK 1 -O 2 dept doesn’t occur in the heart. l 2 -Myocardium utilizes lactic acid as a nice l fuel while other tissues reject it as a wast product. 3 -Glycogenolysis doesn't occur in the heart l except in emergency condition as hypoxia.

Metabolic reactions in the heart. 1 -ATP→ADP+P+E for systole(ATPase l &Ca++) without O 2. 2 -CP→C+ph+E without O 2. l 3 -Oxidation of lactic acid or fat. l Lactic acid (with O 2) →H 2 O+CO 2+E l C 3 H 6 O 3→ 3 H 2 O+3 CO 2+E l

The myocardium consumes about 15 l cc. O 2MIN. during rest and 200 -250 ccmin during severe exercise. (coronary dilatation).

Mechanical efficiency of the heart M. E=Work donetotal energy expenditure l × 100 Normally M. E=20% and In heart failure l =3% and in a well trained athlete =30% Work of the heart =B. P×C. O ……(factor l. . )