MEDICAL BIOLOGY, HUMAN ANATOMY, PHYSIOLOGY AND PATHOLOGY - Ya.I. Fedoniuk 2010

ANATOMY, PHYSIOLOGY, PATHOLOGY

CHAPTER 7. NUTRITION PROCESS AND ITS PATHOLOGY

ANATOMY AND PHYSIOLOGY OF THE DIGESTIVE ORGANS

DISORDERS OF THERMOREGULATION

1. FEVER

Fever is a protective and adaptive reaction of the Organism that occurs in response to pyrogenic stimuli and manifests as a restructuring of thermoregulation to maintain a higher-than-normal body Temperature. Infectious and non-infectious causes of fever are distinguished. Throughout evolutionary development, the febrile response evolved primarily as a defense mechanism against the invasion of microorganisms and their toxins. At the same time, fever can also be induced by non-infectious factors, such as Blood transfusion and the administration of Proteins and Lipids for parenteral Nutrition.

Pyrogenic substances are agents that, upon entering the body from the outside or being produced within it, induce a fever. According to their origin, pyrogens are divided into exogenous (bacterial, non-bacterial) and endogenous (leukocytic). Exogenous infectious Antigens enter the body alongside infectious agents and comprise Bacterial toxins, parasites, and Viruses. Exogenous non-infectious pyrogens may include various sera administered to induce passive Immunity (diphtheria, tetanus), Vaccines used to stimulate active immunity, as well as transfused blood, snake venom, and secretions of certain insects. Endogenous antigens are generated within the organism independently of Bacteria (e.g., fever following bone fractures or myocardial infarction). The underlying cause of their production is the injury or destruction of the body's own Tissues. All the aforementioned substances act as etiological factors, or primary pyrogens, which do not cause fever directly but instead promote the Synthesis of Secondary antigens. Under METABOLISM/18.html">The Influence of primary pyrogens on macrophages and neutrophil granulocytes, these Cells synthesize interleukin-1, a hormone-like protein that exerts specific effects on several systems, including The Nervous system. Stimulated by interleukin-1, Prostaglandins E1 and E2 are synthesized near cerebral Blood Vessels; these prostaglandins act on the thermoregulatory center located in the Hypothalamus. As a result, the set-point of this center is altered, maintaining the body temperature at an elevated level throughout the duration of interleukin-1 synthesis.

The febrile process comprises three stages: temperature elevation (onset); Maintenance of the temperature at an elevated level (fastigium); and temperature reduction to the baseline level (defervescence).

Stage of temperature elevation. In The First stage, thermoregulation is reorganized so that heat production exceeds heat loss. Heat loss decreases due to the constriction of peripheral blood vessels, reduced blood flow to tissues, and contraction of arrector pili Muscles, which manifests as "goosebumps." Heat production increases due to heightened metabolic activity in muscles and shivering. Thermoreceptors are excited, producing a sensation of cold, known as chills.

Stage of maintenance of temperature at an elevated level. The persistence of elevated temperature In the second stage is attributed to a shift in the set-point of the thermoregulatory center. Heat loss increases simultaneously through the dilation of peripheral blood vessels; the previously pale Skin becomes hyperemic and warm to the Touch. A feeling of heat ensues.

Stage of temperature reduction to the baseline level. In the Third Stage, the thermoregulatory center

returns to its previous state, and the set-point shifts back to the normal level. The heat accumulated within the organism is dissipated via the dilation of cutaneous blood vessels, profuse sweating, and rapid breathing. Temperature reduction can occur gradually, by lysis (over several days), or rapidly, by crisis. In the event of a critical temperature drop, a sharp vasodilation may occur, potentially leading to life-threatening circulatory collapse.

Types of temperature curves. The temperature curve during a fever consists of three phases—rise, maintenance, and decline; however, each phase, as well as the curve as a whole, may exhibit specific features that provide insight into the patient's condition and The Nature of the pyrogenic factor.

Continuous fever is characterized by daily temperature fluctuations that do not exceed 1 °C. Initially, the temperature curve rises sharply, reaches its maximum, remains steady for 7–9 days, and then drops abruptly. This type of temperature curve is typical of lobar Pneumonia and typhoid fever.

In remittent fever, daily temperature fluctuations range from 1 to 2 °C. It occurs in conditions such as pneumonia and tuberculosis.

Sepsis presents with hectic fever, where body temperature reaches 41 °C and daily fluctuations span 3–5 °C.

Intermittent fever occurs in patients with malaria. For instance, in tertian malaria, fever attacks recur every other day. During an attack, body temperature rises sharply, remains elevated for 30 minutes to 2–3 hours, and then drops back to baseline or even lower.

Relapsing fever curves are characterized by longer periods of elevated temperature (5–8 days) and a lack of strict regularity in the onset of paroxysms, observed in patients with relapsing fever.

It should be noted that recently, due to the widespread use of Antibiotics, temperature curves have largely lost their typical presentation.