Body Temperature Regulation

Body Temperature Regulation

• The hypothalamus controls body temperature, receiving signals from peripheral nerves and blood temperature.
• The hypothalamic thermoregulatory center balances heat production from metabolic activity with heat loss from skin and lungs to maintain a normal body temperature.
• Normal oral temperature ranges from 37.2°C at 6 A.M. to 37.7°C at 4 P.M.

Fever

• Fever is defined as a temperature above 37.2°C in the morning and 37.7°C in the evening.
• Fever is caused by infection, microbial toxins, mediators of inflammation, and immune reaction, which raise the hypothalamic set point.
• Pyrogenic mediators, such as IL-2, IL-6, TNF, and INF, contribute to fever development.

Types of Fever

• Continuous fever: temperature remains above normal throughout the day, fluctuating less than 1°C in 24 hours (e.g., lobar pneumonia, typhoid fever, and UTI).
• Intermittent fever: temperature elevation occurs only for a certain period, later cycling back to normal (e.g., malaria).
• Remittent fever: temperature remains above normal throughout the day, fluctuating more than 1°C in 24 hours (e.g., infective endocarditis).

Hyperpyrexia

• Hyperpyrexia is a fever above 41.5°C, which can develop in patients with severe infections or central nervous system disease.
• Hyperpyrexia is characterized by an elevated hypothalamic set point.

Hyperthermia

• Hyperthermia is an uncontrolled increase in body temperature, exceeding the body's ability to lose heat, with a normal hypothalamic set point.
• Hyperthermia is often caused by heat exposure, drugs, cancer treatment, and endocrine diseases, and can be rapidly fatal.
• Hyperthermia does not involve pyogenic molecules and does not respond to antipyretics.

Treatment of Fever and Hyperthermia

• Cooling the patient's body
• Good hydration
• Antipyretic therapy

Cough

• Cough is an explosive expiration that provides a normal protective mechanism for clearing the tracheobronchial tree of secretions and foreign material.
• Cough can be initiated voluntarily or reflexively, involving afferent and efferent pathways.

Mechanism of Cough

• Cough starts with a deep inspiration, followed by glottic closure, relaxation of the diaphragm, and muscle contraction against a closed glottis.
• The resulting positive intrathoracic pressure causes tracheal narrowing, rapid flow rates, and shearing forces that aid in eliminating mucus and foreign materials.

Causes of Cough

• Acute cough (less than 8 weeks) in a smoker may indicate chronic obstructive lung disease or bronchogenic carcinoma.
• Other causes of cough include postnasal drip, asthma, gastroesophageal reflux (GERD), and ACE inhibitors.

Approach to the Patient with Cough

• A detailed history provides valuable clues for the etiology of the cough.
• Important questions include:
  • History of chronic rhinitis
  • Voice or altered swallowing
  • Dry or productive cough
  • Haemoptysis
  • Worsening at night or in the morning
  • Persistent or not
• Chest radiography and pulmonary function testing can help suggest or confirm the cause of the cough.
• Fiberoptic bronchoscopy is useful for visualizing endobronchial tumors and collecting cytologic and histologic specimens.

Treatment of Cough

• Definitive treatment depends on determining the underlying cause.
• Elimination of exogenous inciting agents (e.g., cigarette smoke, ACE inhibitors) or endogenous triggers (e.g., postnasal drip, GERD) can be effective.
• Symptomatic or nonspecific therapy may be used for chronic, unexplained cough.

Learn about how the hypothalamus controls body temperature, receiving signals from peripheral nerves and blood temperature. Understand how it maintains a normal body temperature despite environmental changes.