26.2 Water Balance
3 min read•june 18, 2024
Water balance is crucial for our bodies. The hypothalamus controls thirst, prompting us to drink when blood gets concentrated. Our body fluids are split between cells and the spaces around them, with playing a key role in balance.
We lose water through pee, sweat, breath, and poop. ADH, a hormone, helps our save water when needed. can happen if we lose too much fluid, leading to thirst, fatigue, and even serious health issues if left unchecked.
Water Balance
Thirst cycle and body water
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- Hypothalamus contains that detect changes in blood
- Increased blood osmolarity (water loss or solute gain) stimulates in hypothalamus triggers thirst sensation prompts water consumption
- Water intake increases blood volume reduces osmolarity suppresses thirst
- Decreased blood volume stimulates thirst through in blood vessels detect reduced blood pressure and volume signal hypothalamus to induce thirst
Fluid Compartments and Electrolytes
- Body fluids are distributed across different compartments ()
- Intracellular fluid: water within cells, largest compartment
- Extracellular fluid: includes blood plasma and interstitial fluid
- Electrolytes: charged particles in body fluids crucial for maintaining osmotic balance
- : process of maintaining proper solute concentrations in body fluids
Primary pathways of water loss
- production by kidneys filter blood produce urine to remove waste and excess water output regulated by hormones (ADH)
- through skin release water and electrolytes onto skin surface evaporation helps regulate body temperature
- Respiration water vapor lost through exhaled air amount depends on breathing rate and humidity of inhaled air
- Feces some water lost through digestive tract in feces amount usually small compared to other pathways
ADH regulation of water balance
- ADH () produced by hypothalamus stored in
- ADH release triggered by:
- Increased blood osmolarity detected by osmoreceptors in hypothalamus
- Decreased blood volume and pressure detected by baroreceptors in blood vessels
- ADH targets in kidneys:
- Increases water permeability of collecting duct cells
- Allows more water reabsorption from tubular fluid into bloodstream
- Concentrates urine reduces output conserves water in body
- When blood osmolarity and volume normal or low ADH release suppressed:
- Decreases water permeability of collecting ducts
- Results in dilute urine increased output removes excess water from body
Dehydration causes and effects
- condition where body loses more water than it takes in caused by excessive loss inadequate intake or both
- Causes of dehydration:
- Prolonged sweating due to exercise heat exposure or fever
- Diarrhea and vomiting can lead to significant fluid loss
- Inadequate water intake especially during illness or in hot environments
- Certain medications () that increase urine output
- Effects of dehydration on body:
- Thirst dry mouth decreased urine output
- Fatigue dizziness headache due to reduced blood volume and pressure
- Impaired cognitive function and mood changes
- In severe cases rapid heartbeat low blood pressure organ damage
- Untreated severe dehydration can lead to kidney failure death
- can be assessed through various methods (e.g., urine color, body weight changes)
Homeostasis and Water Balance
- Water balance is crucial for maintaining overall in the body
- Proper hydration supports various physiological processes and organ functions
Key Terms to Review (21)
ADH (Antidiuretic Hormone): ADH, also known as vasopressin, is a hormone produced by the hypothalamus and released by the posterior pituitary gland. It plays a crucial role in the regulation of water balance in the body, as well as in the control of blood pressure and other physiological processes.
Baroreceptors: Baroreceptors are specialized sensory receptors that detect changes in blood pressure within the body. They play a crucial role in the homeostatic regulation of the cardiovascular system, helping to maintain blood pressure within a normal range.
Collecting ducts: Collecting ducts are specialized tubules in the kidneys that play a crucial role in the final stages of urine formation and the regulation of water balance in the body. They receive urine from the nephrons and transport it to the renal pelvis, while also allowing for the reabsorption of water and certain ions, which is essential for maintaining homeostasis and regulating blood volume and pressure.
Dehydration: Dehydration occurs when the body loses more fluids than it takes in, leading to an imbalance that disrupts normal physiological functions. It can result from inadequate water intake, excessive sweating, or illnesses causing vomiting and diarrhea.
Dehydration: Dehydration is a condition that occurs when the body loses more fluids than it takes in, resulting in an imbalance in the body's fluid and electrolyte levels. It is a critical factor in understanding both body fluid compartments and water balance within the human body.
Diuretics: Diuretics are substances that promote the increased production and excretion of urine, often used to manage conditions like hypertension and edema. By influencing the kidneys, diuretics help regulate fluid balance in the body, affecting water retention and electrolyte levels. Their primary function is to assist in removing excess fluid from the body, which can be crucial for individuals with heart, liver, or kidney issues.
Electrolytes: Electrolytes are minerals that carry an electric charge when dissolved in body fluids such as blood, urine, and sweat. They are essential for maintaining proper fluid balance, muscle function, and nerve transmission throughout the body.
Fluid Compartments: Fluid compartments refer to the different regions within the body where fluids are contained and regulated. These compartments play a crucial role in maintaining water balance and ensuring proper physiological functioning.
Heat Stroke: Heat stroke is a severe and life-threatening condition that occurs when the body's temperature regulation system fails, leading to a rapid and uncontrolled rise in body temperature. It is a medical emergency that requires immediate treatment to prevent permanent damage or death.
Homeostasis: Homeostasis is the process through which the body maintains a stable internal environment despite external changes. This concept is crucial as it ensures that physiological processes function optimally, allowing for growth, reproduction, and overall health.
Hydration Status: Hydration status refers to the balance between the amount of water in the body and the body's water requirements. It is a critical factor in maintaining overall health and physiological functions, particularly in the context of water balance.
Kidneys: The kidneys are a pair of vital organs located in the lower back that play a crucial role in the body's overall health and functioning. They are responsible for filtering waste and excess water from the blood, regulating fluid and electrolyte balance, and maintaining acid-base balance, among other essential functions.
Osmolarity: Osmolarity is a measure of the concentration of solute particles in a solution, typically expressed in osmoles per liter (osmol/L). It reflects the ability of a solution to exert osmotic pressure, which is crucial for maintaining fluid balance across cell membranes and influencing various physiological processes such as blood volume, urine formation, and water distribution in the body.
Osmoreceptors: Osmoreceptors are specialized sensory receptors that detect changes in the osmolarity or solute concentration of body fluids, particularly in the hypothalamus. They play a crucial role in the regulation of water balance within the body.
Osmoregulation: Osmoregulation is the biological process of maintaining the appropriate balance of water and solutes, such as salts and nutrients, within the body's fluids. It is a critical homeostatic mechanism that ensures the proper functioning of cells, tissues, and organs across various physiological systems.
Perspiration: Perspiration, also known as sweating, is the process by which the body releases water, salts, and other substances through the sweat glands located on the skin. This physiological mechanism helps regulate body temperature and maintain water balance within the body.
Posterior Pituitary Gland: The posterior pituitary gland, also known as the neurohypophysis, is a lobe of the pituitary gland that is responsible for the storage and release of two important hormones: oxytocin and antidiuretic hormone (ADH). This gland plays a crucial role in maintaining homeostasis, central control, fluid volume and composition, as well as water balance within the body.
Sweat Glands: Sweat glands are exocrine glands found in the skin that produce and secrete sweat, a watery substance composed of water, salts, and other compounds. These glands play a crucial role in regulating body temperature and maintaining homeostasis, and they are closely connected to the structural organization of the human body, epithelial tissue, the layers of the skin, and water balance.
Thirst Center: The thirst center, also known as the thirst regulating center, is a region within the hypothalamus of the brain that is responsible for controlling and regulating the body's thirst response. It plays a crucial role in maintaining water balance and homeostasis within the body.
Urine: Urine is the liquid waste product that is filtered from the blood by the kidneys and stored in the bladder before being excreted from the body. It is a key component in the water balance of the body and plays a crucial role in the elimination of waste and maintenance of homeostasis.
Vasopressin: Vasopressin, also known as antidiuretic hormone (ADH), is a peptide hormone produced by the hypothalamus and stored in the posterior pituitary gland. It plays a crucial role in regulating water balance and blood pressure within the body.