Temperature, Regulation, Thirst and Hunger

Temperature Regulation

Refers to the process by which the body maintains its internal temperature within a narrow range, despite changes in the external environment or metabolic activity.

Homeostasis

Physiologist Walter B. Cannon (1929) introduced the term ________ to refer to temperature and other biological processes that keep the body variables within a fixed range.

Allostasis

Refers to the adaptive way in which the body changes depending on the situation.

Ex. You eat many foods during the holidays, after celebrating the new year , you went to the gym to lessen the weight you’ve gained.

2,600 kilocalories (kcal)

An average young adult expends about _____________ per day. Most of it goes to basal metabolism, the energy used to maintain a constant body temperature while at rest.

Poikilothermic / Varied Heat

• Amphibians, reptiles, and most fish are _____, from the Greek rootsmeaning “varied heat”.

• Their body temperature matches the temperature of the environment.

• lack physiological mechanisms of temperature regulation, such as shivering and sweating.

Homeothermic / Same Heat

• Mammals and Birds are _______ (from Greek roots meaning “same heat”).

• This kind of animals use physiological mechanisms to maintain a nearly constant body temperature despite changes in the temperature of the

  environment.
  

• To cool ourselves when the air is warmer than body temperature, we have only one physiological mechanism—evaporation.

The Hypothalamus

• Plays a central role in regulating body temperature by serving as the body 's thermostat. It receives input from temperature sensors located throughout the body, including the skin, internal organs, and the blood, and integrates this information to initiate appropriate responses to maintain temperature homeostasis

Thirst

• The body also needs enough fluid in the circulatory system to maintain normal blood pressure. People sometimes survive for weeks without food, but not without water.

70%

• Water constitutes about ____ of the mammalian body. Because the concentration of chemicals in water determines the rate of all chemical reactions in the body, the water must be regulated within narrow limits.

Osmotic thirst

• is a type of thirst sensation triggered by changes in the osmotic pressure of the body ' s fluids. Eating salty foods can cause this type of thirst.
  

• This type of thirst is primarily driven by the need to restore fluid balance and dilute the concentration of solutes in the body's fluids.

Osmotic pressure

Refers to the concentration of solutes, such as salts and minerals, dissolved in a fluid. When the osmotic pressure of the ECF increases, indicating a higher concentration of solutes, osmoreceptors in the hypothalamus of the brain are activated, leading to the sensation of thirst.

Hypovlemic Thirst

• is a type of thirst sensation triggered by a decrease in the volume of blood circulating in the body, leading to a decrease in blood pressure.

• It is primarily driven by the need to replenish lost fluids and increase blood

  volume in order to maintain adequate circulation and perfusion of tissues.

• We lose a significant amount of fluid through bleeding, diarrhea or sweating.

Hunger

• is a complex physiological sensation that signals the body's need for food and nutrients. It is regulated by various physiological mechanisms that involve both the central nervous system and peripheral organs.

• arises when the body 's energy stores are depleted or when certain nutrients are lacking, prompting the individual to seek out and consume food to satisfy metabolic needs.

Small Intestines

has enzymes that digest proteins, fats, and carbohydrates.

Large Intestine

absorbs water and minerals and lubricates the remaining materials to pass as feces.

Glucose

an important source of energy throughout the body and nearly the only fuel of the brain.

Insulin

Enables glucose to enter the cells, except for brain cells, where glucose does not need insulin to enter. When insulin levels are high, glucose enters cells easily.

Glucagon

Stimulates the liver to convert some of its stored glycogen to glucose to replenish low supplies in the blood.