WEEK 2: THERMOREGULATION AND PYREXIA Flashcards
What is hunt?
What is negative feedback?
Describe the concept of hunt in negative feedback.
Hunt = oscillate
The depth and extent of the hunting depends upon the properties of the elements of the feedback system.
- In the context of negative feedback, the term “hunt” refers to an undesirable and oscillatory behavior that can occur in control systems.
- Negative feedback is a fundamental control mechanism used in various systems to maintain stability and regulate a specific variable or parameter.
It works by continuously comparing the actual value of the controlled variable with a reference or setpoint value and then adjusting the system’s output to minimize the error between the two.
- However, in some cases, negative feedback systems can become unstable and exhibit a hunting behavior, which is often counterproductive.
This hunting behavior involves the system repeatedly overshooting and undershooting the setpoint, resulting in oscillations around the desired value. This can lead to erratic and inefficient operation.
In summary, “hunt” in the context of negative feedback represents the undesired oscillatory behavior that can occur when a control system repeatedly overshoots and undershoots the desired setpoint.
Physiological Control Centers in many locations in the body.
State the 2 important centers.
Where is the temperature control center?
Two important centers:
*Medulla of brainstem
*Hypothalamus of the diencephalon of the brain
Temperature control center in the Hypothalamus
State the 2 main hypothalamic nuclei responsible for temperature regulation and their functions.
Posterior nucleus- Heat conservation
Preoptic area- Heat dissipation
Hypothalamus is small area of the brain but with considerable variety of inputs and outputs.
These inputs/outputs are both ______ and ________.
Neural inputs from both negative feedback receptors (e.g., temperature) and emotion (e.g., limbic system).
Hypothalamus is small area of the brain but with considerable variety of inputs and outputs.
These inputs/outputs are both neural and hormonal.
Neural inputs from both negative feedback receptors (e.g., temperature) and emotion (e.g., limbic system).
46 male medical students measured after no exercise, food, drink and tobacco for 2 hours, mean oral temperature 36.72oC
276 medical students measured in class with no restriction on activity, mean oral temperature 36.70oC but with greater variation.
What is the conclusion?
This suggests that the conditions under which temperature measurements are taken can have a slight impact on the mean oral temperature, with a slight decrease observed when students are allowed to engage in various activities.
The greater variation in the second group’s measurements could be due to factors such as differing activity levels, environmental conditions, or individual variations in body temperature response.
Overall, these findings highlight the importance of consistent measurement conditions when comparing or interpreting oral temperature data.
There are several conditions, emotions and activity that affect temperature.
Differs slightly in different individuals.
Value may be altered by e.g., exercise.
Outline 8 physiological variations that affect temperature.
Physiological variations:
Age
Sex
Diurnal variation (time of the day)
After meals
Exercise
Sleep
Emotion
Menstrual cycle
Describe how the following physiological variations affect body temperature.
Physiological variations:
Age
Sex
Diurnal variation (time of the day)
After meals
Exercise
Sleep
Emotion
Menstrual cycle
Physiological variations:
Age: Babieshave a slightly higher temperature.
Sex: Women tend to have slightly higher core body temperatures than men.
Diurnal variation (time of the day): Typically, core body temperature is at its lowest in the early morning and highest in the late afternoon or early evening.
After meals: High temperature
Exercise: High temperature
Sleep: Low temperature in deep sleep
Emotion: When angry or having high stress levels, temp becomes high
Menstrual cycle: High temperature
State the 3 pathological variations that affect body temperature.
Hyperthermia
Fever
Hypothermia
What is hyperthermia?
State 4 causes of hyperthermia.
Hyperthermia is a medical condition characterized by an elevated body temperature that exceeds the body’s normal range.
It specifically refers to a situation where the body temperature is raised above the normal range due to external factors or the body’s inability to regulate temperature effectively.
Hyperthermia can result from a variety of causes, including:
- Environmental Heat Exposure: Prolonged exposure to hot weather, especially without adequate hydration, can lead to hyperthermia. This condition can range from heat exhaustion to heatstroke, which is a medical emergency.
- Exercise-Induced Hyperthermia: Intense physical activity, especially in hot and humid conditions, can cause the body temperature to rise significantly. This can lead to exercise-induced hyperthermia and, if severe, may result in heat-related illnesses.
- Certain Medications and Drugs: Some medications, recreational drugs, or stimulants can interfere with the body’s ability to regulate temperature, leading to hyperthermia.
For example, certain stimulants, like amphetamines or ecstasy (MDMA), can lead to elevated body temperature.
- Certain Medical Conditions: Some medical conditions, like hyperthyroidism or neurological disorders, can disrupt the body’s temperature regulation mechanisms, causing persistent hyperthermia.
What is fever?
What is the normal body temperature?
State the 3 main characteristics of fever.
What are some of the causes of fever?
Outline common ways of dealing with fever at home.
- Fever is a temporary increase in the body’s core temperature, often as a response to an underlying illness, infection, or inflammatory condition. It is one of the body’s natural defense mechanisms to combat infections and other health threats.
- Normal body temperature is around 98.6°F (37°C), but it can vary slightly among individuals. When the body’s temperature rises above its usual set point, it is considered to have a fever.
Fever is typically characterized by the following features:
-Elevation in Body Temperature: A fever involves a body temperature that exceeds the normal range. In adults, this is often defined as a temperature of 100.4°F (38°C) or higher when measured orally.
-Systemic Response: Fever is not just a localized increase in temperature but a systemic response. It affects the entire body and can be accompanied by a range of symptoms, including chills, sweating, muscle aches, and fatigue.
-Regulatory Role: Fever is not an illness itself but a symptom of an underlying condition. It is a sign that the body’s immune system is working to combat an infection or another health threat. The elevated temperature can help the body’s immune response by making it more difficult for some pathogens to replicate and enhancing the activity of immune cells.
- Common causes of fever include:
-Viral and bacterial infections, such as the flu, colds, and urinary tract infections, as well as
-Inflammatory conditions like rheumatoid arthritis.
-Medication side effects, heat stroke, or certain medical conditions.
- To manage fever, individuals often take over-the-counter fever-reducing medications like acetaminophen or ibuprofen, drink plenty of fluids, and rest. In some cases, particularly when fever is high or accompanied by severe symptoms, medical attention may be necessary to address the underlying cause or provide additional treatment.
Describe how fever comes about.
Name the receptor bound by PGE2 in the hypothalamus.
-Infection or inflammation
- Macrophages produce endogenous pyrogens (e.g., interleukins) under action of microbial toxins.
-Endogenous pyrogens stimulate production of prostaglandin E2 (PGE2) in the hypothalamus.
-PGE2 acts via EP3 receptors to reset body temperature in hypothalamus.
-The hypothalamus setpoint is increased.
-There is increased heat production and less heat loss.
How does Aspirin reduce fever?
Acts to inhibit synthesis of prostaglandin.
Reduces body temperature only if fevered.
Consider why aspirin induces pleasant warm sensations when feverish.
What is the difference between fever and hyperthermia?
Hyperthermia should be distinguished from fever, where the elevated body temperature is a response to an infection or illness.
Fever is typically a controlled and regulated response by the body, while hyperthermia results from external factors or the body’s failure to regulate temperature effectively.
What is hypothermia?
Hypothermia is typically divided into stages based on the severity of the condition. Describe them.
State causes of hypothermia.
How can hypothermia be treated?
- Hypothermia is a medical emergency condition characterized by a significant and potentially life-threatening drop in the body’s core temperature.
It occurs when the body loses heat more quickly than it can produce it, causing the body’s temperature to fall below its normal range (approximately 98.6°F or 37°C).
- Hypothermia is typically divided into stages based on the severity of the condition:
Mild Hypothermia: In this early stage, the body temperature drops to between 95°F (35°C) and 90°F (32°C). Symptoms may include shivering, increased heart rate, rapid breathing, cold and pale skin, and difficulty with fine motor skills.
Moderate Hypothermia: As the body temperature falls further (between 90°F or 32°C and 82°F or 28°C), shivering may become more intense, and the individual may experience confusion, lethargy, slurred speech, and coordination difficulties. Muscle stiffness and a slowing heart rate may also occur.
Severe Hypothermia: This is the most critical stage, with the body temperature dropping below 82°F (28°C). At this point, shivering may stop, and the individual can become unresponsive, with extremely slow or irregular breathing and a dangerously slow heart rate. Skin may appear bluish or gray, and there is a significant risk of unconsciousness and life-threatening complications.
Hypothermia can be caused by prolonged exposure to cold weather, immersion in cold water, inadequate clothing, or medical conditions that affect temperature regulation.
Treatment for hypothermia involves rewarming the person, which can be done through various means, such as removing wet clothing, providing warm, dry clothing or blankets, and using external heat sources like heating pads or warm water immersion. Severe cases of hypothermia may require hospitalization and more aggressive rewarming techniques.
Prevention is crucial, especially in cold weather or when engaged in outdoor activities in cold environments. Proper clothing, staying dry, and recognizing the early signs of hypothermia are essential to avoid this potentially life-threatening condition.
State the 4 heat transfer mechanisms.
Radiation
Conduction
Convection
Evaporation
