Physiology of the cardiovascul
The Cardiovascular System-Blood Pressure and The ECGBlood pressure is the force of blood distending thearterial walls. Blood pressure is measured in the Brachial artery using a sphygmomanometer, the average resting bp in a normal person is 120/80. The higher number is the systolic blood pressure (SBP), which is produced as blood is expelled from the heart during ventricular systole. The lower number indicates diastolic blood pressure (DBP), this corresponds to the pressure being exerted on the blood vessels during the relaxation phase (diastole) of the cardiac cycle. Blood is delivered to all tissues of the body by maintaining arterial blood pressure, which is dependent on cardiac output (volume of blood pumped by the heart per minute) and peripheral resistance (which is increased byconstriction and decreased by dilation of the arterioles).Blood pressure is controlled by chemoreceptors which signal to the vasomotor center in brain causing vasoconstriction as well as barorecepteors. Humans have myelinated Baroreceptors, found in the carotid artery in the neck, the pulmonary arteries and in the aortic arch. They respond to stretch in arterial walls caused by changes in blood pressure. The set point for blood pressure can
The AV node is a highly specialized conducting tissue (cardiac, not neural in origin) that slows the impulse conduction considerably (to about 0. As exercise begins the set pressure value is raised, the higher intensity exercise the higher the new pressure will be, so that when the blood pressure falls the heart rate, stroke volume and cardiac output all increase to allow blood pressure to reach the new level (6). If diastolic bp increases on exercise it is likely that the indidual has coronary artery disease (2). These specialized fibers conduct the impulses at a very rapid velocity (about 2 m/sec). 05 m/sec) thereby allowing sufficient time for complete atrial depolarization and contraction (systole) prior to ventricular depolarization and contraction. It acts on a adrenergic receptors causing vasoconstriction in arteries of the lower limbs, and b1 receptors where it increases heart rate( positive chronotropic effect), force of contraction of the ventricles, (positive inotropic effect) and causes an increase in rate of conduction of electrical impulses (a positive dromotropic effect)(6). Wave of depolarization travels down the bundle, divides into theleft and right branches so that the septum depolarizes from left-to-right producing vector 1. If there is a problem with the body's reflexes or they have low blood volume they may experience postural hypotension when the blood pressure is too high after changing posture or takes longer to return to base levels(4). The bundle branches then divide into an extensive system of Purkinje fibers that conduct the impulses at high velocity (about 4 m/sec) throughout the ventricles. Smooth muscle tone in the veins can be increased by the sympathetic nervous system which acts to ensure that blood returns to the heart. This results in depolarization of ventricular myocytes and ventricular contractionReferences1. Veins in the lower limbs dilate and the net affect is that blood is forced up to the heart.
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