Biology Exam III Physiology: test prep questions

If two compartments are separated by a membrane permeable only to water, water will flow from an area of low Osmolarity to high Osmolarity.

True: Water will flow from the compartment that is more dilute (low concentration of solutes) to the compartment that is less dilute (high concentration of solutes). Osmolarity refers to the concentration of dissolved particles in a liquid.

Biomagnification of fat-soluble toxins (that bioaccumulate in individual organisms) is an inevitable consequence of low production and trophic-level transfer efficiencies.

True: bc energy is always lost between successive trophic levels, individual organisms at level always consume more biomass from lower trophic levels than they themselves possess.

The Q10 effect describes how the rate of a chemical or physical reaction (e.g., nerve conduction) changes with an increase in body temperature of 10C. This effect helps explain the adaptive significance of increased body temperature.

True—More precisely, remember that Q10 = R2/R1, where R2 and R1 are rates of reaction at two temperatures (T2 and T1) that differ by 10C. T2 = T1+10.

Describe how counter-current flow between fluid in the salt gland and the blood supply allows for maximally efficient elimination of excess salt in reptiles and birds.

As fluid moves down tubules in the salt gland, it becomes increasingly loaded with Na+ and Cl- ions. This increasing concentration is the result of the active transport of salt ions from body fluids (plasma) to the salt gland against their concentration gradients. As fluid in the gland becomes progressively loaded with Na+ and Cl-, the concentration of these ions in plasma declines. Because of the counter-flow arrangement, blood exiting the gland is "paired with" (lies next to) the most up-stream, beginning segments of the salt gland's tubules. This blood is at its "cleanest"... that is, it has relatively little salt since most was already removed by active transport. At the same time, the salty fluid in the up-stream portion of the tubule is at its most dilute. Thus, the difference in concentration is minimized at the point where blood leaves the glad, and the "cost" of eliminating the last bit of salt is reduced.

The net rate of diffusion (J) is proportional to:

(the inverse of distance) (the concentration gradient)

ACTH released by the pituitary acts on the adrenal glands to produce CORT. CORT has all of the following effects except [select all that apply]: -Decreases the production of releasing hormone by the hypothalamus -Increases the production of ATCH by the pituitary -Decreases immune responsiveness -Increases fat storage

-Increases the production of ATCH by the pituitary -Increases fat storage

Despite the benefits associated with the Q10 effect, increasingly higher Tb can be disadvantageous bc

-Loss of protein structure and function at high Tb -Energetic costs required to maintain a high Tb -Disrupted membrane function

Water and salt balance are important because:

-Water is used to dilute and/or excrete nitrogenous waste in many organisms -Evaporative water loss is an important mode of thermoregulation -Ion gradients across membranes are crucial to physiological function -Most biochemical reactions necessary for life occur in solution

Describe one structure-function relationship pertaining to thermal biology.

-the functioning of counter-current heat exchange s -vasodilation and heat windows.

Organisms with a diameter greater than ___ require some means of delivering O2 to internal cells, cells that would otherwise quickly become starved for O2 as they consume O2 more rapidly than it is replaced by diffusion from the external environment.

1 mm

Describe two ways arthropods can escape cell damage despite being exposed to sub-freezing temperatures during the winter months.

1) They could produce antifreeze proteins, either glycerol (lowers freezing temperature) or glycoproteins (prevent growth of ice crystals 2) They also have nucleating agents, which actually encourage ice crystals to form in the extracellular space so that water is drawn out of the cell to lower it's freezing point (cell becomes saltier) .

Explain how heterotherms can maintain a constant rate of reaction (for key physiological processes) despite seasonal changes in Tb.

Acclimatization to seasonal changes in temperature often involve expression of a new suite of enzymes. If the organism retained the same enzymes all year, rates of reaction would slow in the winter and accelerate in the summer. However, by shifting enzymes, the rate of reaction can be kept constant, assuming that the Q10 of the winter enzymes > than the Q10 of the summer enzymes.

When the athlete exercises, there is increased heart rate and stroke volume to increase the delivery of oxygen to active tissues. There is no devastating decrease in pressure because the arteries experience vasodialation

Blood pressure is function of both cardiac output (CO; mL blood pumped per minute) and total peripheral resistance (TPR). Although vasodilation results in decreases TPR, the individual simultaneously increases heart rate and stroke volume, which results in increased CO and little overall change in blood pressure (or at least, less change than one might predict given changes in TPR alone). Remember that CO=HR*SV.

How did Starling and Bayliss's discovery of the hormone secretin deviate from the traditional "removal and replacement paradigm" followed in classical studies of endocrinology?

By isolating a loop of the small intestine from the nervous system, Starling and Bayliss were able to prove the the nervous system did not control the secretion of hormones in the digestive system. Injecting HCl into this isolated loop of the small intestine caused the secretion of secretin—which, when comes in contact with the pancreas, stimulated the secretion of digestive juices.

The ascending limb of the Loop of Henle is permeable to water and is the portion of the nephron that most determines a mammal's ability to conserve (reclaim water).

FALSE: the descending limb is permeable to water and contributes substantially to a vertebrate's ability to conserve water. As filtrate moves down the Loop, it is subjected to an increasingly extreme osmotic gradient which draws water out of the Loop and, ultimately, back into circulation. Other segments of the nephron are important to water conservation too, however. These segments include the proximal convoluted tubule (where ~ 2/3 of water in the filtrate is reabsorbed) and the collecting duct, which plunges deep into the medulla, just like the Loop. Be sure you understand how the collecting duct, under control by the hormone ADH, conserves water.

Ectothermic organisms are also heterothermic, by definition.

False. Many ectotherms can achieve remarkable control over their Tb through behavioral mechanisms (e.g., postural adjustment; microhabitat choice; gaping) and low-cost physiological mechanisms (such as vasodilation).

Water soluble hormones are immediately bound to a carrier protein upon exiting endocrine cells (via exocytosis).

False: *Lipid* soluble hormones require a carrier protein. The carrier protein allows the hormone to dissolve in plasma and travel to target tissues. It also prevents absorption by only local cell populations.

Positive feedback loops often form a critical component of homeostatic mechanisms because they have the beneficial effect of preventing "runaway."

False: Negative feedback loops are more often associated with homeostasis. With negative feedback, the product or result of a physiological process inhibits its own continuation. Positive feedback leads to runaway.

Some or all nutrients are acquired via extracellular digestion in all living organisms.

False: Some organisms do not digest food at all but simply absorb monomers directly through body surfaces (e.g., tapeworms). Other organisms assimilate food particles before digesting them in food vacuoles (e.g., sponges). In these latter organisms, all digestion occurs intracellularly

Sharks are osmoregulators because the concentration of salt ions in their body fluid differs substantially from the concentration of the same salts in sea water.

False: The body fluid of sharks has approximately the same osmolarity as ocean water (osmoconformers). However, the concentration of some salts in the sharks' body fluid is greatly reduced. How, then, are they osmoconformers? Sharks add "osmolytes" to their body fluid. These osmolytes compensate for the reduction of some salts, allowing sharks to track the osmolarity of the environment even as they modify salt concentrations.

In addition to secreting amylases and lipases, the pancreas also secretes trypsin, a protease that completes the digestion of proteins that began in the stomach with pepsin.

False: The pancreas does not secrete trypsin but an inactive form of the enzyme called trypsinogen...then converted to trypsin cells lining the small intestine. Trypsin then digests polypeptides, helping digestion of proteins first begun in the stomach by pepsin. Final digestion to individual amino acids occurs by enzymes embedded in lining of small intestine. pancreas doesnt secrete trypsin directly bc Proteases are dangerous...if the pancreas produced trypsin directly, it would digest itself! *same reasoning applies production of pepsinogen instead of pepsin by chief cells in gastric pits of stomach*

Gastric pits show strong exocrine function. The presence of food in the stomach causes G-cells to release gastrin into circulation.

False: The release of the hormone gastrin into circulation shows endocrine not exocrine function.

A fish capturing, consuming, and then digesting a mayfly larva is an example of (i) bulk feeding, and (2) assimilation followed by digestion.

False: Yes, this example describes bulk feeding, likely by a "pursuit" strategy (not sit-and-wait). However, it is not an example of "assimilation followed by digestion," which describes intracellular digestion. All bulk feeders digest their food extracellularly in the lumen of their alimentary canal. They then absorb (assimilate) monomers via passive or active transport.

order of extracellular digestion in the foregut (stomach) of vertebrates

G-cells release gastrin into circulation, which stimulates chief cells to secrete pepsinogen and parietal cells to produce HCl

Compare and contrast strategies used by homeotherms in the Thermal Neutral Zone with strategies used by homeotherms when they are faced with ambient temperature below the LCT

In the thermal neutral zone, homeotherms use strategies that require very little energy: behavioral strategies, ptiloerection, counter current exchange, sweating, etc. However, once they are below the LTC, they must expend energy in order maintain body temperature.

Above the UCT, an endotherm:

Increases metabolic rate to maintain Tb

Saltwater fish drink seawater but freshwater fish do not? Why is that!?! Describe how fish in both environments maintain salt balance.

Saltwater fish drink salt water and eliminate the exess salt through active transport in gill epethilia, and havel ow voume and concentrated urine to preserve H2O. Freshwater fish gain water and lose salt through respitory surfaces, and they get this NaCl back by using B-Chloride cells in their gills that pump the salt against concentration gradient. They also have a lot of diluted urine.

Describe how the collecting duct controls the final osmolarity of urine

The collecting duct controls the final osmolatiry of urine by determining whether urine excreted by the animal is dilute or filtrated. As the collecting duct plunges down into the medulla, the concentration gradient from the cortex to inner medulla becomes higher. This means that when the animal is dehydrated and ADH is present, aquaporins in the collecting duct will open and water will flow into the bloodstream. A small and concentrated amount of urine will be produced. On the other hand, if the animal is hydrated, the no ADH is present and the collecting duct is impermeable to water, and a large volume of dilute urine is produced.

Describe the hormone cascade involved in linear growth (bone elongation), including how negative feedback is achieved.

The hypothalamus secretes GHRH, which then causes the anterior pituitary to release Growth Hormone, and triggers the liver to secrete insulin-like Growth Factor 1 (that causes bone elongation). Negative feedback is achieved when GH targets the hypothalamus itself, causing it to manufactire GHIH/ GHIH acts on the anterior pituitary to decrease the production of GH

Describe the functioning of metanephridia in segmented worms. Be sure to address the functional significance of the nephrostome and metranephridial tubules in the worms' filtration-reabsorption system. What is one major advantage of such a system of excretion?

The metanephridia in worms filters and reabsorbs salts and eliminates urea. When fluid from the body enters the ciliated nephrosome, cellls and macromolecles are filtered out as filtrate passed through tiny pores. Advantages to this system of filtration is that unwanted and unknown toxic chemical don't need to be identified, and is useful in freshwater environments since the final urine is very dilute.

Which element(s) of the mammalian and avian heart are most similar to the circulatory system found in fish

The right atrium and ventricle, which receive and then deliver deoxygenated blood to the respiratory surface

Amylases secreted in saliva and by the pancreas initiate digestion of polysaccharides in the lumen of the alimentary canal. Final digestion to simple sugars, however, occurs by enzymes embedded in the membrane of cells lining the small intestine. Absorption of monomers occurs via active transport.

True

Food chains tend to be short because the loss of energy (to entropy) between successive trophic levels ultimately limits the abundance of top (apex) predators. Trophic levels cannot be added indefinitely.

True

Compare and contrast how water soluble and lipid soluble hormones interact with target tissues to alter cell function.

Water soluble hormones cannot pass through the cell membrane of target cells but instead interact with membrane-bound receptor proteins. The receptor protein has an extracellular domain that recognizes the hormone and an intracellular domain that is involved in signal transduction. Changes in the conformation of the receptor protein unleash a cascade of events within the cell that change its function or gene expression. Example: effect of ADH on the collecting duct of the kidney. By contrast, lipid soluble hormones simply pass through the cell membrane of target cells. These hormones interact with a receptor protein inside the cell (an intracellular receptor). Binding of the hormone changes the conformation of the receptor protein, which may than act to modify patterns of gene expression.

Acid in the small intestine stimulates secretion of the hormone secretin from endocrine cells in the intestinal epithelium.

When chyme enters the small intestine, endocrine cells release the hormone "secretin" into circulation, which acts on the pancreas, causing it to release bicarbonate into the midgut. Endocrine cells in the small intestine also release the hormone "CCK" into circulation, which acts on the liver and pancreas to produce bile salts and digestive enzymes, respectively.

explain why seals become skinny while feeding on sea urchins but fat when feeding on fish

When seals are feeding on fish, the prey do all of the osmoregulation so that the seals don't have to. The fish get rid of exess salt by using alpha chloride cells in gill epethelia (active translport then takes plae). Since sea urchins are osmoconformers, the seals need to burn fat in order to generate metabolic water (bc they are not getting it from the prey).

Rank nitrogenous wastes according to level of toxicity, from most to least toxic:

ammonia/ammonium, urea, uric acid

Bubbles of air within a plant's vascular tissue destroy its function. Which of the following structures help conifers prevent embolisms from spreading to adjacent tracheids, an adaptation to cold, arid environments: a)lignin b) tori c) stomata d) vessel members

b) tori

Which of the follow is true of open circulatory systems: [select all that apply] they cannot direct hemolymph to tissues according to demand a) they lack hearts b) they possess hearts but not veins that collect and return hemolymph (to the heart) c) they are not responsive to changing activity levels d) they cannot direct hemolymph to tissues according to demand

d) they cannot direct hemolymph to tissues according to demand

In the mammalian kidney, all of the following structures are involved in the filtration of plasma except:

distal convoluted tubule

Hormone-releasing cells in the anterior pituitary are ____ cells, while hormone-releasing cells in the posterior pituitary are____ cells.

endocrine, neurosecretory

Which of the following animals utilize reabsorption (of water, salts, and/or nutrients) as a component of their excretory physiology.

flatworms mammals insects segmented worms (aka all of them)

Which of the following invertebrates have a filtration-reabsorption system of excretion in which the beating of cilia by flame cells draws body fluid into protonephridia.

flatworms (Platyhelminthes)

In the absence of channels or carrier proteins, biological membranes are least permeable to:

ions (Na, Cl, Mg)

Which of the following animals utilize the secretion of unwanted substances as a component of their excretory physiology.

mammals and insects

Cells whose hormones are not released into circulation but instead affect only local cells are termed

paracrine

In the mammalian heart, which vessels deliver oxygenated blood from the lungs to the heart

pulmonary veins

Describe how structure relates to function for each of the three main components of the peripheral vascular system: veins, arteries, and capillaries.

role of pores/fenestrations in capillaries and how plasma and the solutes it carries are released and then reabsorbed in capillary beds; the importance of one-way valves in veins; and the function of smooth muscle and elastin in arteries.

what hormones are complexed with carrier proteins in plasma and, upon entering the target cell, bind to intracellular receptors?

thyroxin + cortisol

The absence of a peptide hormone's receptor protein in the cell membrane of a target tissue will render that tissue unresponsive to the hormone. For example, the absence of IGF-1 receptors in the growth plate of bone tissue can cause of dwarfism in humans.

true