Heart rate, normal values

Figure 1.2 Negative feedback. These types of responses are employed throughout the body in order to maintain homeostasis. In this example, any change in blood pressure, which is monitored within the circulatory system and processed within the CNS, will cause reflex changes in heart rate. The change in heart rate will be in the opposite direction of the change in blood pressure if blood pressure increases, then heart rate decreases if blood pressure decreases, then heart rate increases. In this way, blood pressure is adjusted back to its normal value.

An example of this type of reflex is the baroreceptor reflex (see Figure 1.2). Baroreceptors located in some of the major systemic arteries are sensory receptors that monitor blood pressure. If blood pressure decreases, the number of sensory impulses sent from the baroreceptors to the cardiovascular control center in the brainstem also decreases. As a result of this change in baroreceptor stimulation and sensory input to the brainstem, ANS discharge to the heart and blood vessels is adjusted to increase heart rate and vascular resistance so that blood pressure increases to its normal value. 

Treatment of atrial fibrillation is initiated to relieve patient symptoms and prevent the complications of thromboembolism and tachycardia-induced heart failure, the result of prolonged uncontrolled heart rates. The initial treatment objective is control of the ventricular response. This is usually achieved by use of a calcium channel-blocking drug alone or in combination with a 13-adrenergic blocker. Digoxin may be of value in the presence of heart failure. A second objective is a restoration and maintenance of normal sinus rhythm. Several studies show that rate control (maintenance of ventricular rate in the range of 60-80 bpm) has a better benefit-to-risk outcome than rhythm control (conversion to normal sinus rhythm) in the long-term health of patients with atrial fibrillation. If rhythm control is deemed desirable, sinus rhythm is usually restored by DC cardioversion in the USA in... 

During phase I, each seizure produces marked increases in plasma epinephrine, norepinephrine, and steroid concentrations that may cause hypertension, tachycardia, and cardiac arrhythmias. " Within minutes, arterial systolic pressures may rise to values above 200 mm Hg, and heart rate may increase by 83 beats per minute. Although blood pressure returns to normal within 60 minutes, mean arterial pressure does not fall below 60 mm Hg hence cerebral perfusion pressure is not compromised. In animals, cerebral blood flow is also increased by 200% to 600%, thereby protecting neurons from hypoxic injury. 

Physical examination in the nursery at 10 minutes showed a thin, malnourished female newborn. Her body temperature was slightly low, her heart rate was rapid, and her respiratory rate of 35 breaths/minute was elevated. Getta s birth weight was only 2,100 g, compared with a normal value of 3,300 g. Her length was 47 cm, and her head circumference was 33 cm (low normal). The laboratory reported that Getta s serum glucose level when she was uiu-esponsive was 14 mg/dL. A glucose value below 40 mg/dL (2.5 mM) is considered to be abnormal in newborn infants. 

Figure 2 Relationship between the developmental profiles for the maximal sensitivity to 2-ClA-induced inhibition of atrial beating rate and the maximum number (Bmax) of Aj adenosine receptors labeled by [ HJDPCPX in embryonic chick heart membranes. Values for 2-ClA-induced suppression of atrial beating rate and [ H]DPCPX Bmax were normalized to the percentage of the maximal value obtained for each parameter during embryogenesis. The normalized values for [ HJDPCPX Bmax for each embryonic age depicted were calculated as the percentage of the value obtained on embryonic day 9 (74.8 6.5 fmol/mg protein), while values for sensitivity to 2-ClA-induced negative chronotropy are the percentages of the maximum response which was a complete suppression of beating rate.

The effect of anemia on the coronary flow was studied here (Table 3), by comparing the two values of abnormal hemoglobin concentrations, Hb = 0.07 gm/ml and Hb = 0.04 gm/ml, to the normal value of 0.15 gm/ml. Anemia is shown here to be associated with increased coronary flow, increased oxygen extraction and a decrease in the oxygen tension in the coronary venous blood. (Jan et ai, 1977). It is shown by the model that at hemoglobin values of 0.07 gr/ml and a heart rate of 120 cycles per minute the myocardium is not hypoxic throughout. However, when Hb = 0.04gm/ml, similar heart rate is associated... 

The relation between ECG wave amplitudes and durations, as well as some other ECG indices, (heart rate, age), commonly used in pediatric cardiology were calculated. The normal standards for each age group, including the number of subjects analyzed, the mean and standard deviation and the 95 and 5 percentile values of the variables were listed in tables, and the 5, 25, 50, 75 and 95 values were illustrated in percentile format charts. 

The tissue distribution and levels of RBP in normal and in retinol-deficient rats were measured in order to explore the role of different tissues in the metabolism of RBP (J. E. Smith et al., 1975). The tissues examined included liver, kidney, fat, muscle, brain, eye, salivary gland, thymus, lung, heart, intestine, spleen, adrenal, testes, thyroid, and red blood cells. The RBP levels were low or very low in tissues other than liver, kidney, and serum and varied from 12 p.g/g of tissue for normal spleen to an undectable level in red blood cells. Much of the RBP in the tissues with low levels was most likely due to residual serum in the samples. In general, except for liver, RBP levels were lower in tissues from retinol-deficient rats than in those fixim normal rats. In normal rats, the liver, kidney, and serum levels were 30 4 (mean SEM), 151 22, and 44 3 p.g/g, respectively. In retinol-deficient rats, the liver RBP level was about three times the normal level whereas the kidney and serum levels were about one-fifth the normal values. It was suggested that die levels of RBP in normal as compared to deficient liver, serum, and kidney appear to reflect the relative rates of RBP secretion and turnover (see later discussion). 

Model parameter values that lie outside the normal physiological range can further enhance auto-regulatory instability. Abnormal values may occur in the pathological situation. Oscillations in pressure and flow were predicted by the model to lie well below heart rate, in the range below 0.1 Hz for a dog. For example, prominent low-frequency oscillations have been observed during heart failure (Goldberger et al., 1984). While it has been proposed that these oscillations follow the respiratory rate, they have... 

Using AEDs as soon as possible after sudden cardiac arrest, within 3-4 minutes, can lead to a 60 percent survival rate. CPR is of value because it supports the circrdation and ventilation of the victim rmtil an electric shock delivered by an AED can restore the fibrillating heart to normal. 

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