Urinary System Flashcards

Homeostasis and Osmoregulation

• Homeostasis: Maintaining a stable internal environment despite external changes.

  • Regulates body temperature, blood pressure, blood pH, and oxygen levels.

  • Relies on negative feedback loops.

• Negative Feedback:

  • A stimulus (change from the set point) is detected by a receptor.

  • The central nervous system (CNS) interprets the change.

  • Effectors are activated to return the body to its set point.

  • Once the set range is reestablished, the response is turned off.

• Water Balance:

  • The human body is approximately 45-75% water.

  • Blood is ~50% water, and cells are ~70% water.

  • Water is crucial for various bodily functions.

• Osmoregulation: Water regulation to maintain fluid and solute balance.

  • Water input (8-10 glasses per day) should match outputs (urination, defecation, sweating).

  • Body fluids require constant temperature, pH, and solute concentration.

  • Osmotic regulation maintains the balance of body solutes (salts and sugars).

• Osmosis: Movement of water across a semipermeable membrane.

Body Membranes and Tonicity

• Body Membranes: Cell membranes and serous membranes lining internal body cavities/organs.

• Semipermeable Membranes: Allow certain solutes and water to cross.

  • Water and solutes typically move down the concentration gradient.

• Tonicity: Describes relative solute concentration.

• Hypotonic Solution:

  • Cells swell due to water movement into the cells (low salt outside).

• Hypertonic Solution:

  • Cells shrivel due to water loss out of the cells (high salt outside).

• Isotonic Solution:

  • Equal solute concentration inside and outside the cell; no net water movement.

Kidney Filtration and Function

• Kidney's Role: Main osmoregulatory organ.

  • Filters approximately 200 liters of blood per day (total blood volume is ~5 liters).

  • Removes wastes from the blood and excretes them as urine, altering the chemical composition of the blood.

• Kidney Structure:

  • Outer Cortex: Contains nephrons.

  • Medulla: Contains renal pyramids (loop of Henle/collecting duct) and renal columns (blood vessels).

  • Renal Pelvis: Leads to the ureter.

• Blood Flow:

  • Blood enters via renal arteries, branching into smaller vessels leading to capillaries in nephrons.

  • Blood exits via renal veins.

• Nephron: Functional unit of the kidney (>1 million nephrons per kidney).

  • Composed of the renal corpuscle, renal tubules, and capillary network.

Nephron Components and Filtration Process

• Renal Corpuscle: Kidney filtering unit.

  • Glomerular Capillaries: Filter out small items like water, amino acids, glucose, and nitrogenous wastes.

  • Blood cells and large proteins are not filtered.

  • The filtered items form the kidney filtrate.

• Renal Tubules: Process kidney filtrate.

  • The composition of kidney filtrate is adjusted as it travels through renal tubules towards a collecting duct.

  • Water, glucose, some salts, and amino acids are returned to the blood.

• Collecting Duct: Collects urine from the tubules.

  • Final opportunity for water and salt reabsorption.

  • Nitrogenous wastes are eliminated (urea) in urine.

  • Urine concentration depends on reabsorption in tubules and collecting duct.

Hormonal Control of Kidney Function

• Hormonal Influence: Brain, heart, and adrenal glands contribute to kidney function.

  • Hormones instruct the kidney on how much water or salt to retain or eliminate.

• Antidiuretic Hormone (ADH):

  • Causes the kidney to conserve water by reabsorbing it back into the blood, reducing water loss in urine.

  • Hypothalamus senses blood water concentration and triggers ADH release when water levels are low.

• Alcohol's Effect:

  • Inhibits ADH secretion, leading to increased urination and dehydration.

• Aldosterone:

  • Released from adrenal glands in response to drops in blood pressure or blood volume.

  • Promotes reabsorption of Na^+ in kidney tubules; water follows Na^+, increasing blood volume and pressure.

  • Works with ADH when dehydrated.

• Atrial Natriuretic Peptide (ANP):

  • Produced by heart cells.

  • Blocks aldosterone secretion when blood pressure is high.

  • Causes the kidney to excrete Na^+ and H_2O, lowering blood pressure.

Blood Pressure Regulation

• Influences: Blood volume and vessel size affect blood pressure.

  • Increasing blood volume increases pressure; decreasing blood volume decreases pressure.

  • Decreasing vessel size increases pressure; increasing vessel size decreases pressure.

• Measurement: Force of blood against arterial walls.

  • Two measurements: higher value during heart contraction and lower value during heart rest.

• Hypertension: High blood pressure.

  • Damages blood vessels over time.

  • Can lead to heart attack, stroke, kidney damage, etc.

  • Awareness is the first step – check your BP regularly.

Homeostasis and Osmoregulation

Homeostasis: Maintaining a stable internal environment despite external changes.

• Temperature: Body temperature regulation involves balancing heat production and loss. Mechanisms include sweating, shivering, vasodilation, and vasoconstriction.

• Blood Pressure: Maintained through adjustments in heart rate, blood vessel diameter, and blood volume. The renin-angiotensin-aldosterone system (RAAS) plays a crucial role.

• Blood pH: Monitored and regulated by the respiratory system (CO2 levels) and the kidneys (bicarbonate levels).

• Oxygen Levels: Maintained by adjusting breathing rate and depth, and by the oxygen-carrying capacity of hemoglobin in red blood cells.

Regulates body temperature, blood pressure, blood pH, and oxygen levels.

Relies on negative feedback loops.

Negative Feedback:

A stimulus (change from the set point) is detected by a receptor.

• Receptors: Temperature-sensitive neurons in the skin and hypothalamus, baroreceptors in blood vessels, chemoreceptors for pH and oxygen levels.

The central nervous system (CNS) interprets the change.

Effectors are activated to return the body to its set point.

• Effectors: Sweat glands, muscles (shivering), blood vessels, kidneys, lungs.

Once the set range is reestablished, the response is turned off.

Water Balance:

The human body is approximately 45-75% water.

• Variation: Water content varies with age, sex, and body composition. Infants have higher water content.

Blood is ~50% water, and cells are ~70% water.

Water is crucial for various bodily functions.

• Functions: Nutrient transport, waste removal, temperature regulation, chemical reactions.

Osmoregulation: Water regulation to maintain fluid and solute balance.

Water input (8-10 glasses per day) should match outputs (urination, defecation, sweating).

• Input Sources: Drinking, food, metabolic water production.

• Output Routes: Urine, feces, sweat, exhalation.

Body fluids require constant temperature, pH, and solute concentration.

Osmotic regulation maintains the balance of body solutes (salts and sugars).

Osmosis: Movement of water across a semipermeable membrane.

Body Membranes and Tonicity

Body Membranes: Cell membranes and serous membranes lining internal body cavities/organs.

Semipermeable Membranes: Allow certain solutes and water to cross.

• Examples: Cell membranes with aquaporins (water channels), kidney tubules.

Water and solutes typically move down the concentration gradient.

Tonicity: Describes relative solute concentration.

Hypotonic Solution:

Cells swell due to water movement into the cells (low salt outside).

• Example: Distilled water.

Hypertonic Solution:

Cells shrivel due to water loss out of the cells (high salt outside).

• Example: Concentrated salt solution.

Isotonic Solution:

Equal solute concentration inside and outside the cell; no net water movement.

• Example: Normal saline (0.9% NaCl).

Kidney Filtration and Function

Kidney's Role: Main osmoregulatory organ.

Filters approximately 200 liters of blood per day (total blood volume is ~5 liters).

Removes wastes from the blood and excretes them as urine, altering the chemical composition of the blood.

Kidney Structure:

Outer Cortex: Contains nephrons.

Medulla: Contains renal pyramids (loop of Henle/collecting duct) and renal columns (blood vessels).

Renal Pelvis: Leads to the ureter.

Blood Flow:

Blood enters via renal arteries, branching into smaller vessels leading to capillaries in nephrons.

Blood exits via renal veins.

Nephron: Functional unit of the kidney (>1 million nephrons per kidney).

Composed of the renal corpuscle, renal tubules, and capillary network.

Nephron Components and Filtration Process

Renal Corpuscle: Kidney filtering unit.

Glomerular Capillaries: Filter out small items like water, amino acids, glucose, and nitrogenous wastes.

• Filtration Pressure: High blood pressure in glomerular capillaries drives filtration.

Blood cells and large proteins are not filtered.

• Significance: Prevents loss of essential components.

The filtered items form the kidney filtrate.

Renal Tubules: Process kidney filtrate.

• Segments: Proximal convoluted tubule, loop of Henle, distal convoluted tubule.

The composition of kidney filtrate is adjusted as it travels through renal tubules towards a collecting duct.

• Reabsorption: Water, glucose, some salts, and amino acids are returned to the blood.

• Secretion: Additional wastes and toxins are removed from the blood and added to the filtrate.

Water, glucose, some salts, and amino acids are returned to the blood.

Collecting Duct: Collects urine from the tubules.

Final opportunity for water and salt reabsorption.

• Influence of ADH: Determines the final urine concentration.

Nitrogenous wastes are eliminated (urea) in urine.

Urine concentration depends on reabsorption in tubules and collecting duct.

Hormonal Control of Kidney Function

Hormonal Influence: Brain, heart, and adrenal glands contribute to kidney function.

Hormones instruct the kidney on how much water or salt to retain or eliminate.

Antidiuretic Hormone (ADH):

Causes the kidney to conserve water by reabsorbing it back into the blood, reducing water loss in urine.

• Mechanism: Increases water permeability of collecting duct.

Hypothalamus senses blood water concentration and triggers ADH release when water levels are low.

Alcohol's Effect:

Inhibits ADH secretion, leading to increased urination and dehydration.

Aldosterone:

Released from adrenal glands in response to drops in blood pressure or blood volume.

Promotes reabsorption of Na^+ in kidney tubules; water follows Na^+, increasing blood volume and pressure.

Works with ADH when dehydrated.

Atrial Natriuretic Peptide (ANP):

Produced by heart cells.

Blocks aldosterone secretion when blood pressure