Phys Exam 4

Where in the body is the sensor that monitors blood osmolarity?

osmoreceptors in the hypothalamus detect high solute levels

Basically, what happens in the proximal convoluted tubule portion of a nephron?

(The tube where filtrates enter) -sodium can be reabsorbed into body with Na/K pump -H2O reabsorption follows the solutes -amino acids and glucose can also be reabsorbed w/ secondary active transport -reabsorption mainly

What is the general function of kidneys? Explain, in general terms, how the kidney works (in terms of kidney logic)

-Filter, remove excess nutrients (water/salt) and toxins from blood -A Nephron has a glomerulus (filtrates squeezed out of), filtrates enter tube and needed things are reabsorbed into peritubular capillaries -Kidney logic = dump everything and then reabsorb what you want

Discuss how each of the following proteins make it possible for blood to absorb more CO2 at the tissues, and release more CO2 at lungs: hemoglobin, carbonic anhydrase, the permease involved in the antiport of Cl- and bicarbonate. Make sure you include the importance of the chloride shift at both ends of your answer.

-Hemoglobin: if CO2 binds with it, it is no longer "chemically" a CO2 molecule, so it allows for more to exist in the blood until it can be released. -Carbonic Anhydrase (CA): an enzyme that assists in the faster conversion of CO2 + H2O into carbonic acid and then into bicarbonate (with high pH) to be used to lower the pH (goes through reverse reaction later and exits body with time). -Permease: removes the bicarbonate from blood, allows Cl- to enter

Where is the sensor in the renin-angiotensin system located? Explain what conditions trigger an increase in the release of renin, and then go through the steps by which additional renin lead to additional angiotensin II.

-JG cells (??): on smooth muscles detecting local pressure into/out of glomeruli -Low blood pressures trigger JG cells to release RENIN (enzyme) > turns angiotensinogen into Ang. I > (ACE enzyme in lung turns it into...) Ang. II

By what means do we increase bicarbonate levels in blood plasma? Why is this increase in bicarbonate biologically important?

-This happens in the collecting ducts of nephrons so that H+ ions can be immediately removed, and bicarbonate can enter blood stream to be stored. -We store the bicarbonate that is created for later use when pH is SUPER high (so it can re-combine with it to make CO2 that can be exhaled).

What factors can lead to constriction of bronchioles? What factor leads to the dilation of bronchioles? Why does constriction/dilation in the presence of these factors make sense?

-constriction = low CO2 level in blood (meaning not enough oxygen is entering body and blood needs to slow down to allow O2 to attach to its hemoglobin) -dilation = high CO2 (need to get it out quicker!) CO2 influencing makes sense if it's something the body desperately wants to remove it will focus on doing that. And it will realize it's need for O2 for basic functioning

Be able to interpret an oxygen dissociation curve. For example, suppose your heart is currently pumping 15 liters/ min, and the partial pressure of oxygen is 80 mmHg in your lungs, and 25 mmHg in your tissues. Using the oxygen dissociation curve that you put together in class, calculate the amount of oxygen being delivered to your body per minute.

190-75=115 ml O2 /L 115 x 15 l/min = 1725 ml/min

Estimate how many red blood cells that you have in your body. Further estimate how many hemoglobin-based oxygen binding sites that you have in your body

25 trillion RBCs in body. 2.5 x 10^22 oxygen binding sites.

In what ways does increasing levels of angiotensin II effect the kidney, and how does this help an organism deal with fluctuating levels of input.

Ang. II : -Bind to type 1 receptor to CONTRACT SMOOTH MUSCLE (increase blood pressure). Helps process the inputs before they re-enter the blood stream. -[Renal retention of salt and water]

Discuss the digestive tract from a design perspective: Explain the location and basic structure of the pancreas, liver, and gall bladder. What do each of these secrete?

Below the stomach because they secrete hormones and enzymes that neutralize the pH and continue breaking food down even further before it enters the small int.

Discuss the digestive tract from a design perspective: Explain the arrangement of smooth muscle within the digestive tract.

Circular and longitudinal to move it forward

Explain what role that the enteric nervous system, vagus nerve, gastrin, CCK, and secretin play in regulating: the release of HCL

Enteric: controls secretory neurons that signal for secretion Vagus nerve: recognizes when food has entered the stomach and needs an acid bath Vagal > enteric > acetylcolene > ECL cells >histamine > HCL Gastrin: hormone that signals release of HCL

Use your understanding of the oxygen dissociation curve to make sense of the oxygen levels (measured in terms of mm Hg) that start having a pronounced effect on ventilation rate.

Extremely low O2 levels will have an effect... "body does respond to decreased O2 levels, but not as much as increased CO2 levels"

After a meal containing starch, proteins, and fats, the blood moving between the small intestine and the liver (within the hepatic portal vein) will tend to have a larger supply of glucose molecules, various types of amino acids, and chylomicrons.

False

Glucose molecules are typically found circulating in our blood stream both right after meals, and in-between meals. Furthermore, all glucose molecules circulating in our blood during these times are dietary in origin (that is, brought in via eating).

False

The delivery of oxygen molecules to the tissues throughout the body is beneficial for many reasons, given the fact that molecular oxygen is used by cells in the performance of many different vital functions.

False ?? I don't know why... maybe because it's just used for ONE function and that is to make ATP?

Increasing circulating levels of angiotensin II will tend to shift the kidney pressure output curve to the right, which means that at any arterial pressure, the kidney output levels will be increased.

False Ang. II maintains it at normal (100). Without it, blood pressure would range all over the place. (low input = more Ang II; high input = no Ang II) (decreased input = DECREASED output)

Consider two individuals with different hematocrits. All else being equal, after passing by the lungs, the person with the higher hematocrit will be able to carry more oxygen molecules (O2) per liter of blood because a higher percentage of the available hemoglobin binding sites will be bound with oxygen molecules.

False Both will likely have an equal amount of percentage of binding sites bound to O2, but the reason why they can carry more is because they have MORE HEMOGLOBIN not more binding sites being used on the hemoglobins.

Increasing carbon dioxide levels in the blood tends to result in increasing levels of hydrogen ions in the blood stream. These hydrogen ions, in turn, directly bind with neurons innervating respiratory centers in the hindbrain triggering them to increase the rate that they fire action potentials, which, subsequently, triggers an increase in both ventilation rate and depth.

False CO2 must travel to the cerebral spinal fluid and then brain first and deconstruct into H+ there for this to happen because H+ ions cannot cross the blood brain barrier (indirect NOT DIRECT) DOES NOT OCCUR IN BLOOD!!

Any molecule that is "squeezed" out of the capillary beds known as glomeruli, and subsequently moves across an epithelium to enter one of a kidney's many nephrons, will subsequently be removed from one's body in their urine.

False Can be reabsorbed

Carbonic anhydrase is an enzyme that facilitates the conversion of carbon dioxide and water molecules into bicarbonate molecules and hydrogen ions, but does not facilitate the reverse reaction.

False It does facilitate the reverse reaction, just not as often (to remove high pH levels)

Increasing potassium ion levels in the blood stream is the one factor known to trigger increasing release of the steroid hormone, aldosterone, from certain cells within the cortical regions of our two adrenal glands.

False It's not the only factor that does this... Ang. II as a tropic hormone can also release it for increased reabsorption.

Kidneys respond to increasing levels of a signal molecule known as ADH by increasing the osmolarity of interstitial fluids located within the middle (medullary) regions of each kidney.

False Kidney's don't change osmolarity because of ADH... ADH recognizes change of osmolarity and opens water gates to fix it.

All the major "out-pockets" found in the digestive tract are found near the beginning of the small intestine (hence, right after the stomach).

False Not "all" of them, some are in the mouth too

One of the important roles played by the "out-pockets" found along the digestive tract is the temporary storage of ingested food, which allows us to consume more food than we need at the moment during times that food is available.

False Not all outpockets store food... only the stomach. Therefore their main role is to secrete digestive enzymes and hormones. *During times food is SCARCE

Both chylomicrons and VLDLs contain triglycerides. Furthermore, the fatty acids making up the triglycerides in both are typically dietary in origin (that is, brought in via eating).

False Only Chylomicrons are dietary. VLDLs are liver synthesized triglycerides.

The only two sphincters associated with our gut tube under voluntary control are the one at the beginning of the gut tube (lips), and the one at the end of the gut tube (external anal sphincter).

False There is also the epiglottis (throat) that controls swallowing or letting food continue into the body.

During each ventilation cycle, the relative pressure of the atmosphere surrounding one's body undergoes considerable fluctuations.

False atmospheric pressure doesn't change based on ventilation.

Discuss the digestive tract from a design perspective: Why secrete hydrogen ions into the stomach? Why do chloride ions accompany the hydrogen ions?

H+ ions are acidic and help chemically break down food further. Chloride ions participate in secondary active transport to help bicarbonate exit the epithelial lining of the stomach into interstitial space... so the Cl- just follows into the stomach. (sterilizes food)

Under what conditions do oxygen dissociation curves shift to the right? How does this type of shift facilitate oxygen transport to tissues?

Increased temperature or decreased pH. To deliver MORE O2 to tissues. (Left shift for fetus to bind tighter to oxygen)

Discuss the digestive tract from a design perspective: Where are the involuntary sphincters, and why does their location make sense? (Note: For a&b, eight sphincters in total.)

Involuntary: stomach opening stomach exit large intestine opening entrance to rectum pancreatic duct opening

Complete this statement: Any molecule dissolved in blood plasma will be removed from the body in the urine unless...

It is reabsorbed (??)

Discuss the digestive tract from a design perspective: Why does the pancreas secret bicarbonate?

It neutralizes the pH (combines with H+ ions to make CO2 that is then removed from the body)

Explain this statement: Regardless how it happens, breathing has to do with changing the size of the pleural cavity. How are the properties of lung tissue, specifically elastance and compliance involved in ventilation (both inspiration and expiration)?

Make the box bigger so lungs expand (let in air), and smaller so they contract (push out air). Elastance: Once stretched, lungs can return to original shape and breathe out Compliance: Can stretch to a larger shape (breathe in)

Discuss the digestive tract from a design perspective: Why does it make sense for a gut tube to develop outpockets? What are the major outpockets?

More space for secretions and to hold food over time. Stomach pancreas liver gallbladder salivary glands

Discuss how hemoglobin makes it possible for blood to absorb more O2 .

O2 doesn't mix well with H2O, so Hemoglobin on RBCs have 4 binding sites which, if all filled, would carry 200 L of O2 in blood!

Discuss breathing in terms of being controlled by a central pattern generator. Where in the nervous system is this CPG seemingly generated? What muscles are involved in inspiration and expiration during quiet breathing?

PARAsympathetic innervation of smooth muscle on bronchioles - Dorsal resp. group (ensures you continue breathing in sleep). DIAPHRAGM involved.

Explain the usefulness of the hepatic portal system. To do so, first list the three potential problems associated with absorbing materials from the small intestines (into the blood) after a meal. Next explain how the combination of the hepatic portal system in combination with the metabolic abilities of hepatic cells helps contend with each of these problems.

PROBLEMS 1. Good AND bad absorbed 2. Osmotic issue (all solutes > shrink cells) 3. Eating molecules you don't need that are saved too long SOLUTIONS 1. Liver's macrophages eat toxins or they're rearranged until they can be expelled 2. Liver strings solutes into larger polymers to reduce solute number and osmolarity

Understand the basic scheme by which dietary protein could end up as amino acids (or glucose molecules) traveling throughout your body. Why does it make sense that there are more types of digestive enzymes and permeases involved in the digestion and absorption of proteins in comparison to carbohydrates?

Protein (hydrochloric acid) > denatured protein (pepsin in stomach) > large polypeptide (pancreatic enzymes) > small polys (brush border peptidase) > peptides (cellular peptidase) > amino acids absorption in small int.: cotransport with H+ (big) or Na+ (amino acid) to blood. Proteins need to be denatured to be broken down. It takes more energy to break their bonds.

Discuss the digestive tract from a design perspective: List some of the things that happen in the large intestine. Why might the large intestine of humans be proportionally smaller than other great apes?

Reabsorption of water largely and moving un-digestible material completely out of body. we probably can't digest as much material as great apes do.

If the enteric nervous system can orchestrate motility and secretion on its own, why are parasympathetic connections (especially through the vagus nerve) important? (Note: the vagus nerve carries both sensory neurons and efferent preglanglionic neurons). Why are sympathetic connections (from postganglionic neurons) important?

SENSATION (hunger, saciation, pain, nerves, etc) sympathetic connection controls blood flow to the gut (enteric can slow it if needed)

Distinguish between maintaining an input-output balance for a scarce resource and an excess resource. Be sure to consider both the supply-side and demand-side of the issue

Scarce (oxygen): -increase rate it is brought in -could potentially be released from storage if available -reduce rate it is lost (skin) -reduce activities to convert it into something else (sit down/not use ATP) -substitution / use something else to do same job (lactic acid fermentation to make ATP) Excess (CO2): -increase rate it is released from body -increase conversion rate of it by chemical reactions -increase rate it is put into storage -keep it from being made in the body by other molecules

Discuss the similarities and the differences between how oxygen and carbon dioxide are transported in the circulatory system.

Similarity: Both go from high to low concentration areas. Difference: O2 needs hemoglobin transport, CO2 just travels by simple diffusion. O2 compelled to move into lungs, CO2 compelled to move out. CO2 converted into other things (like bicarbonate)

Trace how dietary carbohydrates could end up as glucose molecules traveling throughout your body. (Note: Be sure to include how these carbohydrates are digested, where the digestion occurs, how and where absorption occurs, and what, if anything, happens in the liver.)

Starch --------------- amylase (mouth) begins digestion > >> Maltose (Maltase) > G's >> sucrose (sucrase) > G-F >> lactose (lactase) > Gal-G >>>small intestine absorption: GL/G cotransport with Na+ and GLUT2 (Fruc w/GLUT5 first). Pancreas releases insulin. Liver strings glucose into glycogen or delivers it via LDLs

Why it is more difficult to maintain oxygen balance when breathing through a five-foot long snorkel than a foot long snorkel? through a foot long snorkel than no snorkel at all?

There's more dead air space. This means that there's more room for leftover CO2 air to remain and that will be the first air inspirated into lungs, meaning there won't be much room in the inhale for oxygen to enter. If there was no tube, there'd be no dead air space and 100% levels of oxygen would be inspirated every time. *there's 150 ml of dead air space in trachaea and bronchioles

Why are plasma proteins not normally found in urine?

They don't fit through glomeruli openings

Discuss the digestive tract from a design perspective: What are the salivary glands, what do they secrete, and why does their location make sense?

They secrete salivary amylase to begin chemical breakdown of food in the mouth (right where food enters, to help coat it with lubrication to travel down gut tube easily)

Trace the pathway by which dietary fatty acids could end up stored in adipose cells as triglycerides. Make sure you include discussion of why dietary sugars must be present for such storage to occur. Next trace the pathway by which dietary carbohydrates can end up stored as triglycerides in adipose cells. Finally trace the path by which dietary cholesterol (or cholesterol synthesized in the liver) is delivered to other body tissues. Why is a cholesterol source for body tissues important?

Trig (micelle to cell) > fatty acid (enter cell) | FA > tri-g > chylomicron Fatty acids need insulin to be stored and insulin is only triggered by sugars (glucose) Liver can synthesize triglycerides (VLDLs) from excess glucose. Which can be used in the body in times of need. Cholestrol is also inserted by liver into VLDLs and then convert into LDLs to transport cholestrol to body cells that need it. It builds cell membranes, makes bile salts, and helps digest vitamin D.

Chylomicron remnants and LDLs are similar in that the "fats" that they are carrying are largely cholesterol molecules, and membrane lipids. An important difference is that only LDLs are involved with delivering cholesterol molecules and membrane lipids to cells throughout the body.

True (both don't have triglycerides anymore) and LDLs are transporters to cells. Remnants transport to the liver only.

Increasing circulating levels of angiotensin II will lead to smooth muscles wrapped around arterioles throughout the body with angiotensin II receptors, to increasingly contract, and also lead to certain cells within the outer part of the two adrenal glands to release more of a steroid hormone known as aldosterone.

True Ang. II is responsible for vasoconstriction to absorb more from blood and as a tropic hormone releases aldosterone for reabsorption.

There is a direct link between the fact that hydrogen ions are added to the kidney filtrate (urine) from certain collecting duct epithelial cells, and that bicarbonate levels in the blood are much higher than blood hydrogen ion levels.

True Because in this reaction, CO2 has combined with H2O to make H+ (which exits through the filtrate) and bicarbonate (which enters interstitial space for later use)

The ingestion of a starch molecule leading to glucose molecules moving into a capillary surrounding your small intestine, involves all the following steps. The starch molecule is first broken into disaccharides of glucose, called maltose, by an enzyme called amylase that is released both by the salivary glands and the pancreas. Maltose is then broken into individual glucose molecules by an enzyme called maltase, which is located within the "brush border" of the small intestine. Glucose molecules are then brought into epithelial cells of the small intestine by secondary active transport, and then move out of these cells into interstitial space by facilitated diffusion. Once in interstitial space, based on both their small size and the concentration gradient, there is a net movement of glucose molecules into surrounding capillaries.

True Digestion of Glucose

After a carbohydrate heavy meal, glucose molecules that enter into liver (hepatic) cells can be used in the assembly of a glucose polymer known as glycogen, or used in the synthesis of fatty acids.

True Glucose can make either.

Formed from neural crest cells that migrate into the area by following the developing gut tube early in embryogenesis, the gut tube has, in effect, its own nervous system. That is a connecting neural network consisting of sensory neurons, interneurons, and motor neurons.

True It is PARASYMPATHETIC Post-ganglionic

After leaving the lungs, blood passing by the tissues never actually releases all the oxygen molecules that are bound to hemoglobin binding sites.

True It probably saves some for later in case it is needed in emergency reserve.

Small, potentially damaging, water-soluble molecules circulating in one's blood stream could potentially be removed by the kidney, even if the kidney has no means to "identify" or "recognize" that molecule.

True It will dump all molecules that fit into the tubule, and then only reabsorb that which it needs (so it wouldn't reabsorb a toxin)

While postganglionic parasympathetic neurons innervate the smooth muscles wrapped around bronchioles, postganglionic sympathetic neurons do not.

True NO SYMPATHETIC!!! ONLY PARA-SYMPATHETIC

An important component of a kidney being able to generate relatively dilute urine is to have some region of a nephron that actively transports sodium ions out of the filtrate, but is impermeable to water, so water molecules are unable to follow.

True That is the diluting region

If all else remained the same, increasing the diameter of someone's trachea would decrease the resistance to air flow in and out of the lungs, while also decreasing the proportion of the oxygen molecules brought in during each inhalation that are able to diffuse into the blood stream.

True There'd be less wind resistance, but more dead air space.

In comparison to their role in the delivery of oxygen molecules from lungs to tissues, hemoglobin molecules in red blood cells do not play as large of a role in the transfer of carbon dioxide molecules from tissues to the lungs. But they do still play a couple important roles, including directly binding with some of the carbon dioxide molecules being released by tissues, along with binding with hydrogen ions generated from a chemical reaction involving carbon dioxide molecules.

True They bind with CO2 to turn it into a chemically different thing (so there's technically less CO2 in the blood)

The typical path for a fatty acid that is part of an ingested triglyceride to become part of a triglyceride found within chylomicron is: It is first cleaved off the ingested triglyceride within the small intestine (by an enzyme known as lipase), and then reassembled into a triglyceride within an epithelial cell of the small intestine.

True Triglyceride > fatty acid | fatty acid > Triglyceride >> chylomicron

During each ventilation cycle, there is a moment when the relative pressure within the pleural cavities drops to around its lowest point (its most negative relative pressure), and the relative pressure inside the lungs is around zero.

True When the lungs inhale fully.

Decreasing arterial pressure will tend to lead to JG cells, associated with individual kidney nephrons, to increase their release of a molecule known as renin. Which is curious, in the sense that renin is not a signal molecule, per se. It is an enzyme.

True low pressure is sensed by JG cells which release renin enzyme > Ang I (from angiotensinogen) > Ang II (with ACE in lungs)

We have two expanded storage areas in our gut. The first is our stomach, which temporarily stores much of what is ingested after a large meal. The second is our colon, which temporarily stores those components of what we ingested that could not be digested and absorbed in the small intestine. Yet, in addition to their storage roles, other important aspects of the overall story of digestion and absorption occur in both of these locations.

True yes, this is all right.

What factors modulate ventilation rate? Where are monitors to these factors located? Explain why the chemosensitive area is affected more by blood levels of carbon dioxide than by hydrogen ions, even though the actual sensor responds to hydrogen ion levels.

Ventral resp group: controls muscles attached to ribs that increase/decrease ventilation rate. Chemosensitive area: -Detects H+ ions (pH) and CO2 levels in cerebral spinal fluid -CA enzyme increases H+ and decreases CO2 -So if it recognizes these changes of pH or CO2 it will change breathing rate. High CO2 = high ventilation rate. higher pH increases it only a bit. (high pH = high CO2)

Discuss the digestive tract from a design perspective: Where are the voluntary sphincters, and why does their location make sense?

Voluntary sphincters: lips throat (epiglottis) anus control when food enters and waste leaves

Explain how kidney output could continue to match fluctuating levels of salt and water input in the absence of a renin-angiotensin system. What are the problems associated with this method of outputs matching inputs? Use understanding of these problems to explain why a person with a poorly functioning renin-angiotensin system needs to carefully regulate their salt intake.

With fixed kidney output curve (wouldn't use smooth muscle or ang. II). Blood pressure changes depending on intake. -PROBLEM: blood pressure goes all over the place depending on what you're eating. -Careful regulation of salt intake would be important because you don't want your blood pressure to suddenly skyrocket when your body cant control how quickly/slowly it's processed (no smooth muscle use)

Two different counter-current multipliers work to increase, above normal, interstitial fluid osmolarity within the inner region of a kidney (the medulla). a. Explain how each of these work? b. Explain the biological importance of generating this high osmotic area. c. What hormone must be present for an organism to take advantage of this high osmotic area? d. Why are individuals with low protein diets unable to concentrate their urine to the same degree as individuals with high protein diets?

a. Loop of Henle: creates a higher osmolarity region. Na+ will already be exiting the diluting region to create a lower osmolarity in the ascending portion. Interstitial space causes water to leave the descending portion and increase its osmolarity. all moves and starts again. (increases to 1200 mOsm and then Water will be compelled to exit the collecting duct to balance it) Urea Waste CCmultiplier: collecting duct is permeable to urea which enters interstitial fluid and re-enter the ascending portion of loop. It could circle like this many times before being released from body. helps compel water out of the collecting duct. b. It's the only way that water will leave the collecting duct (to even out the osmolarity) so that concentrated urine can be produced (when there's too much solute in body) c. Anti-diuretic hormone (allows channels on collecting duct to open) d. Anti diuretic hormone (vasopressin) is a PROTEIN hormone. So without enough proteins it is not created to the extent needed to regulate opening of channels to allow water out of the collecting ducts.

By the time filtrate (within a nephron) passes through the early distal tubule, it is osmotically dilute (less than 300 mOsm). a. How did it become osmotically dilute? b. Complete this statement: This dilute filtrate will remain dilute as it passes to the bladder, and then out of the body if... c. When would the production of dilute urine be biologically important? d. What CNS created sensation should not accompany the production of dilute urine?

a. urine goes through the loop portion of the convoluted tubule, and then passes by the selectively impermeable portion which only allows Na+ to exit (H2O stays in urine) making it dilute. b. collecting duct remains closed to the passing of water out of selectively impermeable channels c. When there's too much water in the body than what's needed. d. ??

In addition to altering the kidney, what are some other effects that angiotensin II has on the body?

acts as a tropic hormone in adrenal cortex to trigger the release of Aldosterone (increase sodium potassium pumps in kidney nephrons for reabsorption) -effects brain conscious thought and is thirsty. Also releases vasopressin for water reabsorption in kidney. -[increase heart muscle growth] -[vasomotor center signaled to help all of this move quickly]

Explain how a (relatively) negative pressure in each pleural cavity develops. How is negative pressure involved in keeping lungs from collapsing?

at a compressed condition (breathe out), there's not pressure in cavity. At expanded condition (breathing in) pleural cavity pressure grows increasingly negative because it doesn't expand as much as the lungs do. Without pressure, lungs won't be compelled to expand/contract and their compliance/elastance will be lost. They stay in a uniform stance. Residual volume: you can't collapse everything

Explain this statement: While carbon dioxide is a by-product of metabolism, it seems incorrect to call it a waste product.

because there's still many uses of CO2 in the body, even if it's an excessive resource. -combines with water and CA enzyme to make carbonic acid and then bicarbonate (to regulate pH levels) -High CO2 levels lead to high pH -remove CO2 as much as it's produced to maintain pH balance

Explain the connection between excessive levels of cell breakdown, aldosterone, and prevention of irregular heart beats.

cell breakdown > releases potassium (hyperkalemia which could effect action potentials and cause irregular heart beats) > aldosterone (triggered by tropic hormone Ang. II, but this time release with high K+) shut down K+ production or seeking until its removed.

Discuss the digestive tract from a design perspective: Explain how the small intestine increases its absorptive area.

convoluted tubing in the gut allows for a long tube in a small space, outpocket spaces for extra absorptive cells.

Use the perspective established in the above question to discuss, in general, maintaining an oxygen and carbon dioxide balance.

done

Discuss the digestive tract from a design perspective: Why a stomach?

it holds food for a period of time so it isn't all digested at once and you don't have to constantly eat. It also mechanically and chemically digests it.

Discuss the digestive tract from a design perspective: Why is the stomach not an absorptive area?

pH here is too high to absorb any nutrients into the blood stream. We first want it nutrilized and in the small intestine there is more surface area for complete absorption of all molecules.

How would the absence of surfactants make ventilation more difficult? Explain your answer

surfactants allow smaller alveoli to remain (reduce surface tension on those alveoli). There are more of them in small alveoli and less in large ones. Small alveoli would collapse and you'd have less exchange areas for oxygen in lungs.

Explain why a nephron lacking a loop of Henle could help restore osmotic balance to an organism with low blood osmolarity (too much water in the mix), but could not help restore osmotic balance to an organism whose blood's osmolarity is too high (too little water in the mix).

with no loop, there will still be the diluting region that lets only Na+ out of the tube (releasing more water out of the body and reabsorbing sodium), but only with the loop will the difference in osmotic balance be detected to allow water to exit the tubule, even out the balance, and filter out concentrated urine. (loop is a countercurrent multiplier)

(Something to ponder!) A human and an Australian hopping mouse are both on board a ship that shipwrecks on a small tropical island. The island has plenty of nutritious food but no freshwater. The human dies within a few days, while the hopping mouse keeps on hopping. Why was the mouse, but not the human, able to survive?

without pure water the body cannot filter out enough of the solute. Too much solute in blood will not be processed or filtered out. And there won't be enough room for H2O molecules in blood stream to assist with basic cellular function. idk why the mouse is alive though, maybe they have a better filter since they're so small it circles around faster ??