Homeostasis and Feedback Mechanisms

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Questions and Answers

What is the main purpose of the excretory system?

  • To eliminate waste products and regulate water levels (correct)
  • To produce hormones for growth
  • To increase nutrient absorption in the intestines
  • To filter toxins from the atmosphere

Which substance is primarily responsible for nitrogenous waste in mammals?

  • Urea (correct)
  • Ammonia
  • Creatinine
  • Uric acid

How does a hyperosmotic solution affect cell volume?

  • It causes the cell to shrink due to water movement out (correct)
  • It maintains a constant volume inside the cell
  • It causes the cell to swell due to water influx
  • It has no effect on cell volume

Which organ primarily filters out carbon dioxide from the blood?

<p>Lungs (B)</p> Signup and view all the answers

What role does the liver play in the excretion process?

<p>It breaks down toxins for kidneys to excrete (C)</p> Signup and view all the answers

What is the main product of protein metabolism that is toxic and must be processed by the liver?

<p>Ammonia (D)</p> Signup and view all the answers

How does hydrostatic pressure affect fluids in the body?

<p>It is the pressure exerted by the fluid due to its weight (D)</p> Signup and view all the answers

What term describes a solution with a lower concentration of solutes compared to another solution?

<p>Hypotonic (D)</p> Signup and view all the answers

What is the primary role of the kidneys in the urinary system?

<p>Filter waste from blood and produce urine (C)</p> Signup and view all the answers

How does the hypothalamus contribute to maintaining fluid balance in the body?

<p>It produces hormones that regulate thirst and kidney function (C)</p> Signup and view all the answers

What condition leads to the release of Antidiuretic hormone (ADH) from the hypothalamus?

<p>Insufficient water in the bloodstream (A)</p> Signup and view all the answers

Which of the following correctly describes the main waste product excreted by the kidneys?

<p>Urea (C)</p> Signup and view all the answers

What role do ureters play in the urinary system?

<p>Carry urine from the kidneys to the bladder (B)</p> Signup and view all the answers

What substance is primarily filtered in the Bowman's capsule?

<p>Water, salt, and sugar (D)</p> Signup and view all the answers

What happens when there is an excess of water in the body?

<p>ADH levels decrease and more water is excreted (B)</p> Signup and view all the answers

What would occur if the liver did not convert ammonia into urea?

<p>Toxic substances would accumulate in the blood (D)</p> Signup and view all the answers

What is the primary role of vasodilation in temperature regulation?

<p>To bring blood closer to the skin surface for heat release (D)</p> Signup and view all the answers

What happens when the body detects a decrease in temperature?

<p>Blood vessels constrict to minimize heat loss (C)</p> Signup and view all the answers

Which of the following describes a poikilotherm?

<p>An organism that varies its body temperature with the environment (C)</p> Signup and view all the answers

How do thermoreceptors contribute to temperature regulation?

<p>They send signals to the hypothalamus upon detecting temperature changes (D)</p> Signup and view all the answers

What is the function of osmosis in maintaining water balance?

<p>Moving water from areas of high solute concentration to low solute concentration (D)</p> Signup and view all the answers

What condition is depicted by a solution that has a higher concentration of solutes compared to another solution?

<p>Hyperosmotic (A)</p> Signup and view all the answers

Which process is involved when blood returns to the body's core after cooling?

<p>Vasoconstriction to maintain core temperature (B)</p> Signup and view all the answers

Which of the following accurately describes endotherms?

<p>Organisms that generate heat internally through metabolism (B)</p> Signup and view all the answers

Flashcards

Hyperosmotic solution

A solution with a higher solute concentration and lower water concentration than another solution.

Osmolarity

Measure of total solute concentration in a solution, measured in osmoles/L.

Tonicity

Impact of a solution on cell volume, especially for non-penetrating solutes. Described as hypertonic, hypotonic, etc.

Nitrogenous waste (fish)

Fish excrete ammonia, needing a lot of water for elimination.

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Nitrogenous waste (mammals)

Mammals excrete urea, requiring a moderate amount of water for elimination.

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Nitrogenous waste (birds/reptiles/insects)

Birds, reptiles, and insects excrete uric acid, needing little water.

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Excretion

Removal of waste products from the body.

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Liver's role in excretion

Breaks down toxins (like alcohol), converting them to a form kidneys can excrete. Protein metabolism produces toxic ammonia.

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Liver's role in waste processing

The liver converts toxic ammonia from protein breakdown into urea, which is less harmful and can be safely removed from the body.

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Urea's importance

Urea is the main waste product generated by the body, resulting from protein breakdown, and is removed from the blood through the kidneys.

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Kidney function

The kidneys filter waste products like urea from the blood, helping to maintain a healthy balance of fluids and salt in the body.

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Urinary system's function

The urinary system removes waste products from the bloodstream and regulates the body's water and salt balance.

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Nephron function

Nephrons are the tiny filtering units within the kidneys that clean the blood by filtering water, sugar, and salts, then reabsorbing what's needed.

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Antidiuretic hormone (ADH)

A hormone that regulates water reabsorption by the kidneys, responding to changes in blood water levels.

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Urine formation process

Blood enters the kidneys, passes through nephrons, where water, sugar, and salts are filtered and reabsorbed, and any remaining waste is discharged as urine.

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Urinary bladder function

A stretchy sac that stores urine until it's expelled from the body.

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Hypothalamus Role in Temperature Regulation

The hypothalamus acts as a thermostat in the body, monitoring internal temperature and triggering mechanisms to maintain a stable internal temperature through sweating, vasodilation, and shivering.

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Vasodilation

The widening of blood vessels, particularly in the skin, allowing more blood to flow near the surface, thus releasing heat and promoting cooling.

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Vasoconstriction

The narrowing of blood vessels, primarily in the skin, reducing blood flow near the surface and minimizing heat loss to the environment.

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Shivering

Involuntary muscle contractions that generate heat through rapid muscle movement, helping to raise body temperature.

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Homeotherm

An organism that maintains a relatively stable internal body temperature, regardless of external conditions.

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Poikilotherm

An organism with a body temperature that varies significantly with environmental conditions.

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Endotherm

An organism that generates heat internally through metabolic processes to maintain a constant body temperature.

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Ectotherm

An organism that relies on external heat sources to regulate their body temperature.

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Study Notes

Homeostasis

  • Maintaining a constant internal environment despite external changes
  • Key homeostatic systems include blood pH, oxygen/carbon dioxide levels, body temperature, electrolytes, and blood sugar
  • Homeostatic control systems have three main components
    • Monitor system (receptors): sends signals through sensory pathways
    • Coordinating center (brain): processes information and sends signals to motor pathways
    • Regulator system (muscles, glands): carries out actions using hormones and adjustments
    • These components work together via feedback loops to maintain stability

Negative Feedback

  • Most common type of feedback
  • Reverses or counteracts changes/opposes deviations
  • Example: if body temperature rises above normal, sweating is triggered to lower temperature

Positive Feedback

  • Less common than negative feedback
  • Increases the change
  • Example: oxytocin release during childbirth increases contractions until delivery

Thermoregulation

  • Maintaining stable internal body temperature
  • Hypothalamus acts as a thermostat, monitoring and adjusting body temperature
  • Hypothalamus triggers responses if temperature is too high or low
  • Activates effectors and hormones to communicate with organs and other systems
  • Normal human temperature range: 36.2–37.2 degrees Celsius

Heat Stress

  • Thermoreceptors in peripheral nervous system detect increased body temperature
  • Signal sent to hypothalamus
  • Hypothalamus coordinates a response to activate cooling mechanisms, like sweating
  • Vasodilation (blood vessels dilate) to help release heat from blood
  • Cooling internal systems as cooled blood returns to the core, cooling internal organs

Cold Stress

  • Thermoreceptors in skin detect a drop in temperature
  • Signal sent to hypothalamus
  • Hypothalamus activates warming systems
  • Vasoconstriction (blood vessels constrict) reduces blood flow to skin
  • Shivering (muscle contractions) generates heat
  • Goosebumps increase insulation

Water Balance

  • Organisms maintain constant volume, solute content, and temperature
  • Osmosis: water moves from lower solute to higher solute concentration
  • Hypoosmotic: solution with lower solute concentration
  • Hyperosmotic: solution with higher solute concentration
  • Isosmotic: solution with same solute concentration as another

Nitrogenous Waste

  • Fish and amphibians eliminate ammonia (NH3) requiring large amounts of water
  • Mammals eliminate urea (NH2CONH2) requiring moderate amounts of water
  • Birds and insects eliminate uric acid (c5h4n403) requiring very little water

Excretory System

  • Removes waste products from the body
  • Includes digestive, respiratory, skin, and urinary systems
  • Kidneys filter water and urea
  • Lungs filter carbon dioxide
  • Skin excretes sweat containing urea

Liver

  • Breaks down toxins like alcohol
  • Converts toxic ammonia to less toxic urea
  • Detoxifies the blood and removes harmful substances

Formation of Urine

  • Steps in urine formation include filtration, reabsorption, and secretion
  • Filtration: pushes water, urea, salts from glomerulus into bowman's capsule, large components like proteins do not pass
  • Reabsorption: essential materials (glucose, amino acids, water) are reabsorbed by peritubular capillaries, maintains balance and conserves water and nutrients
  • Secretion: nitrogenous waste, H+ and K+ are moved from blood to the nephron

Kidney Stones

  • Hard deposits of minerals/salts that form in kidney
  • Vary in size and shape causing pain when blocking urinary passages
  • Common minerals forming kidney stones are calcium, oxalate, and uric acid
  • Diagnosed through urinalysis (test of urine sample for high protein, blood, glucose, and pH)

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