Body Fluid Distribution and Water Balance

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Questions and Answers

What role does the integrating centre play in the body's response to environmental changes?

It serves as the primary sensor for monitoring the external environment.

It detects specific variables such as temperature and blood pressure.

It determines the appropriate response to correct imbalances. (correct)

It directly executes the physiological actions based on received signals.

Which of the following accurately describes negative feedback in the context of homeostasis?

The process enhances a deviation from the set point until equilibrium is achieved.

The effectors work to reverse conditions when they go beyond the set point. (correct)

It stops the functioning of effectors entirely once the set point is achieved.

It activates physiological mechanisms that could lead to a continuous rise in temperature.

What is the primary function of effectors in a feedback control system?

To process environmental changes and send signals to the integrating centre.

To receive signals from the brain without generating a physiological response.

To serve as the initial receptors that detect changes in the environment.

To carry out responses that restore balance after receiving instructions. (correct)

What kind of receptors are responsible for detecting temperature changes in the body?

Temperature receptors in the skin or hypothalamus. Signup and view all the answers

What happens to the secretion of insulin when blood sugar levels normalize?

Insulin secretion completely stops and does not resume. Signup and view all the answers

What is the primary factor that prevents net water movement across cell membranes between intracellular fluid (ICF) and extracellular fluid (ECF)?

Similar osmolarity Signup and view all the answers

If the body loses 2.5 L of water per day, approximately how long can a person theoretically survive without further water intake?

17 days Signup and view all the answers

Which fluid compartment is characterized by high concentrations of Na⁺ and Ca²⁺?

Extracellular Fluid (ECF) Signup and view all the answers

What is the total daily water loss in a typical day according to the information provided?

2.5 L Signup and view all the answers

What role does exercise play in the body's regulation of water?

Increases the rate of water loss Signup and view all the answers

Which of the following is NOT a primary method of water excretion in the human body?

Digestion through stomach Signup and view all the answers

What is one significant factor that affects the body's daily water loss?

Exercise Signup and view all the answers

Which solute is predominantly found in high concentrations in Intracellular Fluid (ICF)?

K⁺ Signup and view all the answers

What term did Walter Cannon coin to describe the body's ability to maintain internal stability?

Homeostasis Signup and view all the answers

Which mechanism is used by the body to increase temperature when it is too cold?

Shivering Signup and view all the answers

How does the body respond if blood pressure rises too high?

Vasodilation Signup and view all the answers

What role does the autonomic nervous system play in homeostasis?

It regulates heart rate Signup and view all the answers

Which term is used for the feedback mechanism that amplifies a change during processes like childbirth?

Positive feedback Signup and view all the answers

What is the primary function of insulin in the context of homeostasis?

Lower blood glucose levels Signup and view all the answers

Which ion's levels are primarily regulated to ensure normal cellular function?

Calcium Signup and view all the answers

In what situation would the body increase respiration rate?

When carbon dioxide levels rise Signup and view all the answers

What is the term for the body's response to low blood glucose levels?

Secretion of glucagon Signup and view all the answers

Which mechanism contrasts negative feedback by amplifying changes within the body?

Positive feedback Signup and view all the answers

What is the primary location where filtration occurs in the kidneys?

Glomerulus Signup and view all the answers

Which process involves selectively reabsorbing substances back into the bloodstream?

Reabsorption Signup and view all the answers

What is the role of the basement membrane in kidney filtration?

To act as a filtration barrier for large molecules Signup and view all the answers

Which characteristic of the basement membrane contributes to its function in filtration?

Negatively charged Signup and view all the answers

What type of cells are podocytes and what is their role?

Epithelial cells that form filtration slits Signup and view all the answers

What substances are primarily removed during the filtration process in the kidneys?

Water and waste products Signup and view all the answers

How do the kidneys contribute to the balance of electrolytes?

By regulating which ions are filtered and reabsorbed Signup and view all the answers

What percentage of a kidney's function is attributed to filtration?

50% Signup and view all the answers

What is the structural feature of podocytes that contributes to their function?

Foot-like projections for filtration Signup and view all the answers

What process in the kidneys ensures that essential substances are not lost in urine?

Reabsorption Signup and view all the answers

What role do aquaporins play in water transport across epithelial cells?

They facilitate rapid water transport across cell membranes. Signup and view all the answers

Which of the following mechanisms contributes to water loss through the skin?

Increased evaporation due to sweating. Signup and view all the answers

How can diarrhea lead to dehydration?

By excess secretion of water and electrolytes into the intestinal lumen. Signup and view all the answers

What is a consequence of impaired water reabsorption in the kidneys?

Increased urine output and potential dehydration. Signup and view all the answers

What can lead to increased water loss due to osmotic diuresis?

High levels of glucose in the urine. Signup and view all the answers

What happens during the filtration process in the kidneys?

Excess water and waste products are filtered out of the blood. Signup and view all the answers

What is considered insensible water loss?

Water vapor lost during respiration. Signup and view all the answers

What effect can cholera toxin have on intestinal function?

It causes excessive secretion of water and electrolytes. Signup and view all the answers

During normal respiration, what mechanism primarily accounts for water loss in the lungs?

Evaporation during exhalation of water vapor. Signup and view all the answers

Which condition can lead to an increase in sensible water loss?

High ambient temperature leading to sweating. Signup and view all the answers

Study Notes

Body Fluid Distribution: ICF & ECF

Intracellular Fluid (ICF): Fluid inside cells, approximately 28 liters
Extracellular Fluid (ECF): Fluid outside cells, approximately 14 liters
ECF includes blood plasma and interstitial fluid
Both ICF and ECF have equal osmolarity (~280 mOsm), preventing net water movement across cell membranes.
ECF has high concentrations of sodium (Na⁺) and calcium (Ca²⁺)
ICF has high concentrations of potassium (K⁺)

Daily Water Balance

Average daily water loss: 2.5 liters
- Urine: 1.5 liters
- Lungs (breathing): 0.3 liters
- Skin/Sweat: 0.6 liters
- Feces: 0.1 liters
Water intake should match water loss for hydration
Without water intake, survival is unlikely beyond 3 days due to severe dehydration

Factors Affecting Water Loss

Exercise
External temperature
Intake of coffee, alcohol, or salt
Medical conditions (diseases)

Maintaining Water Balance

Body regulates water levels through:
- Water intake: Drinking fluids and consuming water-rich foods
- Water excretion: Primarily through kidneys, but also via lungs, skin, and feces
Water moves across epithelia primarily via osmosis, following solutes like sodium and glucose.
Aquaporins facilitate rapid water transport across epithelial cells in intestines and kidneys.

Water Crossing Epithelia

Lungs:
- Water loss as vapor during breathing
- Increased with exercise or cold, dry environments
Skin:
- Sweating: Water secretion helps cool the body
- Insensible water loss: Continuous, small water loss through skin, even without sweating
Gut:
- Diarrhea: Increased water excretion due to poor absorption or excessive secretion
Kidneys:
- Filtration: Water filtered out of blood in glomeruli
- Secretion: Some water secretion into renal tubules
- Reabsorption: Water reabsorption back into blood in nephrons
- Reduced reabsorption increases urine output, eliminating excess water

Filtration in Kidneys: The Protein Mesh

Filtration: One of the kidneys' main functions, along with reabsorption
Occurs in the glomerulus, where blood is filtered into Bowman's capsule
Kidney filtration removes waste products, excess ions, and water, retaining larger molecules like proteins.
The protein mesh in the glomerulus is composed of:
- Basement membrane: Gel-like matrix of collagen and glycoproteins, the primary filtration barrier
- Podocytes: Specialized epithelial cells with foot-like projections (pedicels) that form filtration slits

Homeostasis: Maintaining Internal Stability

Walter Cannon coined the term "homeostasis"
Body's ability to maintain internal stability (temperature, pH, fluid balance) through regulatory mechanisms
Examples:
- Body temperature: Maintained around 37°C (98.6°F)
- Blood pressure: Regulated for proper blood circulation
- Heart rate: Adjusted based on activity levels, stress, etc.
- Respiration rate: Adjusted to maintain oxygen and carbon dioxide balance
Other examples:
- Blood glucose levels: Regulated by insulin and glucagon
- Electrolyte balance: Regulation of ions like sodium, potassium, and calcium

Feedback Loops in Homeostasis

Sensors (receptors): Detect changes in internal or external environment (temperature, pressure, pH)
Integrating centers (control centers): Receive sensor signals, process information, and determine appropriate response
Effectors: Organs or systems that carry out the response to restore balance
Feedback control: Regulates the response of effectors to maintain homeostasis
- Negative feedback: Most common type, opposes changes to bring system back to equilibrium
- Positive feedback: Amplifies changes, often involved in specific processes like childbirth

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Description

Explore the concepts of intracellular and extracellular fluids, including their distribution and osmolarity. Learn about daily water balance, factors affecting water loss, and the importance of maintaining hydration for survival.