OSMOREGULATION AND EXCRETION

Question 1

What is a portal system?

Answer 1

A portal system is a vascular system that begins and ends at a capillary bed with no pumping mechanism in between

Question 2

What are the 3 types of portal systems in the human body?

Answer 2

1. Hypothalamohypophyseal portal
2. Renal portal
3. Hepatic portal

Question 3

How does the hepatic portal system function?

Answer 3

Blood which enters through the hepatic portal vein from the intestine is rich with nutrients but also toxins

Question 4

What is osmoregulation?

Answer 4

Osmoregulation is required by homeostasis and is the general term for the process by which organism control solute concentrations and balance water gain and loss

Question 5

What is excretion?

Answer 5

Excretion is the ridding of nitrogenous waste and other metabolic waste products from the body

Question 6

How does water leave and enter cells?

Answer 6

Through osmosis, which occurs when 2 solutions separated by a membrane differ in total solute concentrations

Question 7

What is osmolarity?

Answer 7

Osmolarity is the unit of measurement for the solute concentration and is represented by the number of moles of solute per liter of solution (e.g. 300 mOsm/L human blood)

Question 8

What is the formula for osmolarity?

Answer 8

Osmolarity = molarity (moles/L) x # particles/molecule

Question 9

What is an isoosmotic solution?

Answer 9

An isoosmotic solution is when 2 solutions of the same osmolarity continuously share water molecules at equal rates in both directions across a semipermeable membrane

Question 10

What is a hyperosmotic solution?

Answer 10

A hyperosmotic solution is the solution with the higher concentration?

Question 11

What is a hypoosmotic solution?

Answer 11

A hypoosmotic solution is the more diluted solution, or rather the solution with the lower concentration of solutes

Question 12

What direction do water molecules move?

Answer 12

Water molecules move from the less concentrated solution to the higher concentrated solution, reducing the concentration difference for both solutes and free water via dilution

Question 13

What are the 2 ways in which animals can maintain water balance?

Answer 13

1. Osmoconformer
2. Osmoregulator

Question 14

What is an osmoconformer?

Answer 14

An osmoconformer is an organism which is isoosmotic with their surroundings, meaning their internal osmolarity is stable and the same as that of the environment, so there is no gain or loss of water

Question 15

What is an osmoregulator?

Answer 15

An osmoregulator is an organism whose control of internal osmolarity is independent of that of the external environment

Question 16

Why do osoregulators expend more energy then osmoconformers?

Answer 16

Osmoregulators must expend energy to maintain the osmotic gradients that cause water to move in and out, which is done through the active transport of solutes

Question 17

How do animals control solute concentrations?

Answer 17

Animals can indirectly control solute concentrations in cells by managing solute content of an internal body fluid that bathes the cells

Transport epithelia are also required, which are 1+ layers of epithelial cells specialized in moving regulating solute movement

Question 18

What are waste products composed of?

Answer 18

Nitrogenous breakdown products of proteins and nucleic acids, which are broken down for energy or converted into carbohydrates and fats while enyzmes remove nitrogen in the form of ammonia, which is very toxic

Question 19

What are the different forms of nitrogenous waste?

Answer 19

1. Ammonia - toxic, but aquatic organisms dilute their waste with water; lowest energy cost
2. Urea - much less toxic, requiring less water for dilution; requires more energy to convert ammonia to urea
3. Uric acid - least toxis, requiring least water for dilution; required the most energy to produce

Question 20

What are the key functions of every excretory system?

Answer 20

1. Filtration
2. Reabsorption
3. Secretion
4. Excretion

Question 21

What is filtration?

Answer 21

Filtration is the filtering of body fluids producing filtrate, which is then collected in the excretory tubes

Question 22

What is reabsorption?

Answer 22

Reabsorption is the reclaiming of valuable substances from the filtrate by the transport epithelium, and returning them to body fluids

Question 23

What is secretion?

Answer 23

Secretion is the addition of toxins and other solutes from body fluid to filtrate

Question 24

What is the principle site of osmoregulation?

Answer 24

The kidneys

Question 25

What is the name of the duct in which urine leaves the kidneys?

Answer 25

Ureter

Question 26

What is the name of the duct in which urine leaves the bladder?

Answer 26

Urethra

Question 27

What is the first collection point of urine in the kidneys?

Answer 27

Renal pelvis

Question 28

A closer look at what happens in the proximal tubule:

Answer 28

1. Reabsorption is critical for the recapture of ions, water, and valuable nutrients from the huge volume of initial filtrate 1. NaCl enters by facilitated diffusion and is then moved to interstitial fluid by active transport 2. H2O reduces filtrate volume 3. Glucose, amino acids, K+ and other essentials are transported from filtrate to intertitial fluid 2. Filtrate processsing helps maintain pH 1. H+ is secreted into lumen 2. 90% of the buffer HCO3- is reabsorbed from filtrate 3. As filtrate passes, materials to be excreted become concentrated

Question 29

A closer look at what happens in the descending limb of the Loop of Henle:

Answer 29

1. Filtrate volume is further reduced 2. Aquaporins allow permeability to water, resulting in an increase in solute concentration 3. No channels for salts or other solutes

Question 30

A closer look at what happens in the ascending limb of the Loop of Henle?

Answer 30

1. Lacks water channels and is therefore impermeable to water, diluting filtrate as it moves up the cortex 2. Thin region near loop allows NaCl diffusion into interstitial fluid to help maintain osmolarity 3. Thick region adjecent to the distal tubule allows the active transport of NaCl

Question 31

A closer look at what happens in the distal tubule:

Answer 31

1. Key to regulating K+ and NaCl concentrations 1. K+ secreted into filtrate 2. NaCl reabsorbed from filtrate 2. pH regulated by controlling H+ secretion and HCO3- reabsorption

Question 32

A closer look at what happens in the collecting duct:

Answer 32

1. Filtrate processed into urine 2. Hormone control of permability and transport determine extent to which urine becomes concentrated 3. Impermeable to salts and, in the renal cortex, urea

Question 33

If ATP production stopped, urine production would...?

Answer 33

Decrease and be isoosmotic to plasma

Question 34

What is the primary solute affecting osmolarity?

Answer 34

NaCl

Question 35

Why is the production of urine hyperosmotic?

Answer 35

Because considerable energy is expended for active transport of solutes against concentration gradients

Question 36

What is the function of the anti-diuretic hormone (ADH)?

Answer 36

ADH restores normal osmolarity by increasing permeability to water when there is an increase in blood osmolarity

Question 37

What released ADH?

Answer 37

ADH is produce by the hypothalamus and "stored" in the posterior pituitary gland

Question 38

What is the function of the renin-angiotensin-aldosterone-system (RAS)?

Answer 38

RAAS increases blood pressure and regulates kidney functions when the body needs to reduce blood volume without increasing osmolarity?

Question 39

What is the function of the JGA in RAAS?

Answer 39

The JGA releases renin when blood volume or pressure drops, allowing for the cleavage of angiotensin into angiotensin II

Question 40

What is the function of angiotensin II in RAAS?

Answer 40

Angiotensin II triggers vasocontriction, increasing blood presure and decreasing blood flow

Question 41

What stimulates the release of aldosterone from the adrenal glands?

Answer 41

Angiotensin II

Question 42

What is the fuction of aldosterone in RAAS?

Answer 42

Aldosterone causes nephron's distal tubules and collecting ducts to reabsorb Na+ and water

Question 43

What is the function of the atrial natriretic peptide (ANP)?

Answer 43

ANP opposes RAAAS and decreases blood pressure or volume through 1 of 3 ways: 1. Inhibiting the release of renin from the JGA 2. Ihibiting reabsorption of NaCl 3. Reducing release of aldosterone