exam 1

Question 1

Icefish

Answer 1

• Antarctic fish that differ from most fish in that it has no hemoglobin in its blood, giving it an almost ghostlike appearance
• Icefish are a family of fish in the suborder Nototheniodei, which includes many “red-blooded” fish

Question 2

Hemoglobin function

Answer 2

1) Hemoglobin facilitates the diffusion of O2 into the blood by keeping the partial pressure of blood O2 low
2) binds to O2 to determine oxygen-carrying capacity
- bound oxygen is not good for measuring O2 levels
- Lower O2 levels in the blood due to hemoglobin binding leads to greater diffusion via alveoli
3) Hemoglobin is divided into 4 subunits: 2 alpha and 2 beta
- there is a gene for b-globin and a gene for a-globin
- Hemes groups that aren’t genetically coded for, carry oxygen

Question 3

Why do Icefish lack Hb?

Answer 3

1) Icefish don’t have the B gene and are missing part of the A gene
2) Hb was only deleted one time and all other icefish lacked it after (this is the most parsimonious answer)
3) Loss of Hb was likely due to genetic drift

Question 4

How do they survive with no hemoglobin?

Answer 4

1) There is a high solubility of seawater for O2 and oxygen is plentiful in Antarctica
2) They have a lower metabolism which reduces the demand for O2
3) They have a lower blood viscosity: the heart will work less to pump blood
4) Larger hearts: increased pressure and volume- a greater cardiac output (5x)
5) Larger diameter in blood vessels and capillaries: less resistance to flow
- results in very high flow rates of blood and perfusion of tissues
6) Larger blood volume (4x)- more oxygen overall

Question 5

Presence and absence of myoglobin

Answer 5

1) Myoglobin is a respiratory pigment found in muscles
- only has one heme group
2) Loss of myoglobin occurred after loss of hemoglobin
- Lost 4 independent times and all examined Icefish to date lack myoglobin in oxidative skeletal muscle and cardiac atria
- still have genes for myoglobin- only a loss in expression

Question 6

Transport mechanisms

Answer 6

Equilibrium: a state of minimum capacity to do work under locally prevailing conditions
1) Passive Transport: carry material only in the direction of equilibrium (high to low concentrations)
- simple diffusion: osmosis and small permeable things (oxygen)
- Facilitated diffusion: non-permeable, big non-lipid soluble molecules. Typically use transmembrane proteins, channels, and pores
2) Active Transport: capable of carrying material away from equilibrium
- requires energy, (low to high concentrations), uses proteins
3) Bulk transport (high to low concentrations)
- Endo and exocytosis

Question 7

3 major body fluids

Answer 7

1) Intracellular Fluid: ICF 67% of total body fluids
2) Extracellular fluid: 33% of total body fluids
3) Blood plasma: 20% of ECF
- Interstitial fluid: 80% of ECF

Question 8

Reservoir model

Answer 8

1) water, volume, and solutes in the ECF have many inputs and outputs
2) To maintain homeostasis (or balance, or a steady state) input must equal output

Question 9

conformer vs regulator

Answer 9

1) Idealized regulators maintain the same osmolarity regardless of changes in the ambient environment
2) Idealized conformers: osmolarity conforms to the ambient environment
3) there are in betweens (i.e weak, strict, strong, limited, perfect,

Question 10

Freshwater fish osmotic challenges

Answer 10

1) rely on many things: kidneys, gills, and gi tract to regulate their blood osmotic pressure and salt composition
2) All freshwater animals regulate their blood osmotic pressure at levels hyperosmotic to their environment
- Hyperosmotic regulators
- gain water constantly which dilutes their body fluids
- diffuse ions from blood water
- High energy costs to counteract fluid dilution
- dilute blood was likely an adaptation to reduce energy costs
- U/P is less than 1

Question 11

Freshwater fish permeability

Answer 11

1) integument relatively low permeability to water and ions
- this reduces the rates of passive water and ion exchange
2) Gills are a window for O2, H20, and ions to leave and enter
3) High permeability and large surface area of gills is not good ofr water/salt balance
- mosy osmosis and diffusion occurs across the gills
4) High metabolic intensity: high rates of water/salt exchange

Question 12

Freshwater fish urine

Answer 12

1) Void excess water by making copious amounts of urine
- rate of urine secretion = rate of water influx
2) urine is hypoosmotic to their blood plasma
3) Kidneys are regulatory organs: they adjust thier function in ways that help maintain stability of volume and composition in the body fluids
4) Urinary loss of ions can pose a threat to the integrity of body fluids when Na and Cl are low in supply
5) volume regulation and ionic regulation are at conflict with each other in freshwater fish

Question 13

Freshwater fish active ion uptake

Answer 13

1) Actively transport both ions into their blood directly from the pond or river
- active uptake from ambient water requires ATP, thus active uptake places demand on animals energy resources
- the mechanisms that pump Na and CL are typically different and independent of each other
- the cl pump typically exchanges bicarbonate ions for Cl ions, (electroneutral)
- Na pumps are also electroneutral
- Bicarbonate and hydrogen that are pumped from the blood are produced during aerobic catabolism, being formed by the rxn of metabolically produced CO2 and H2O
- Na and Cl play critical roles in acid-base physiology

Question 14

Gills

Answer 14

1) gills are the principal sites of Na and Cl uptake via active transport
2) Gills are made of many thin folds called the secondary lamellae: increase the surface area in which O2 can diffuse into the blood
3) Gills consist of 2 types of cells
1) Mitochondria rich cells: the principal site of active ion uptake into the gills
2) Pavement cells: the principal site of O2 uptake
4) Physiological tradeoff: low calcium levles lead to an increase in MRC’s, this can interfere with O2 uptake. Increasing one ability decreases the other

Question 15

Food and drinking water

Answer 15

1) freshwater animals gain ions from food
- typically don’t drink water

Question 16

Saltwater fish osmotic challenges

Answer 16

1) Most ocean invertabrates are isosmotic to their environment
- do not face the problems of osmoregulations as they don’t gain or lose water to any great extent
2) relatively permeable to ions and water
3) Active uptake of ions from seawater at body surface or ingested seawater in the gut
4) Kidney regulation of blood composition
5) hyposmotic regulators: body fluids are more dilute than the ambient seawater

Question 17

Saltwater fish blood plasma

Answer 17

Why is their blood plasma dilute?
- lose water by osmosis and gain ions by diffusion to replace water they drink and incur an NaCl load to absorb H2O from the seawater in their gut
- Their kidneys make urine that is approximately isomotic to their blood plasma
- Ocean mammals lack salt glands, but have kidneys that can produce relatively highly concentrated urine

Question 18

Marine organisms

Answer 18

1) ECF always contains inorganic ions
2) They are osmoconformers
3) Urea makes up 1/3 of ECF and ICF in osmoconforming hypoionic regulators
4) ECF and ICF are always equal to each other

Question 19

Hagfish

Answer 19

1) Pure osmoconformers
- stenohaline: mate in salt water and will die if moved to freshwater
- euryhaline: survive in a wide range of osmolarity
- ECF osmolarity conforms to external environment
- Found in brackish waters, tide pools, estuaries
- must “regulate” their ICF osmolarity to prevent changes in cell shape

Question 20

Tuna fish

Answer 20

1) lose water because they are hyposmolar to the marine environment ( obligatory)
- regulatory gain of water
- obligatory gain of salt and regulatroy loss (active)
2) How do they do this?
- gut limits salt absorption
- excrete small amounts of urine that are isomotic to their blood plasma
- this limits water loss
- active extrusion of Cl and active or passive out-flux of Na at the gills

Question 21

Mechanism of epithelial NaCl secretion in marine organisms

Answer 21

1) Na and Cl are transported independently outward
2) These processes require ATP which is used to indirectly set up Na and K gradients
- sodium gets concentrated in the ECF
- Chlorine is contranspoeted into the MRC from the blood and then diffuses out to the ambient water
- Sodium is driven out of the blood directly to water largely due to electrical forces (negative charge on gill membrane)

Question 22

Salt glands

Answer 22

1) NaCl in most marine vertabrates is ridden via an extrarenal mechanism
2) Limits salt absorption in the gut
U/P ratio = urine osm/ plasma osm
3) Salt glands excretes salt with very little water
- excrete salt from urine to drink salt

Question 23

Cartilaginous fish

Answer 23

1) osmoconforming hypoionic regulators
2) Have TMAO= trimethylammonioum oxide to promote enzymatic reactions
3) Urea helps humans get rif of nitrogenous waste (bad for enzymatic reactions)
4) ECF is a little higher than outside+ drives water into cells (obligatory)
- Obligatory salt gain
- Gills block the loss of urea and TMAO
- excrete salt via rectal gland and produce modest amounts of urine

Question 24

phenotypic plasticity

Answer 24

1) Trout born in freshwater migrate to salt and then back to fresh
- salt exposure leads to phenotypic change
- when in salt water, their NKCC increases to excrete salt
2) How?
- must have mechanism to sense change in osmolarity
- somehow prolactin is released from the pituitary gland
- Prolactin acts on the gills to upregulate the expression of NKCC and Na/K ATPase
- hormones help then regulate physiological changes

Question 25

Body size matters

Answer 25

1) Surface area to volume ratio
- Increased size+ smaller surface area to volume ratio
- smaller fish have larger challenges in terms of osmosis and NaCl gain

Question 26

Mammal osmoregulation

Answer 26

1) In vertebrates, kidneys are one of the main organs that control ECF osmolarity and are the primary organ for osmoregulation in mammals
- lose water but gain w=salt
- kidneys help them excrete salt (hypertonic urine)

Question 27

Kangaroo rats

Answer 27

1) Live in deserts
2) remain in cool burrows during daytime
3) respiratory moisture is condensed in nasal passages
- reduces water loss
4) Gain metabolic water from dry seeds
- free water from food
5) Feces is dehydrated prior to defecation
6) have a u/p of 16

Question 28

U/P ratio

Answer 28

1) urine is concentrated via countercurrent multiplication from loop of henle
2) Significance of u/p ratio
- an index of the action of the kidneys in osmotic regulation
Conserving vs ridding
1) U/P =1 (isomotic urine): water is excreted in the same relation as solutes in plasma, the osmotic pressure isn’t altered
2) U/P= <1 (hyposmotic urine): Water is preferentially excreted. Urine contains less water relative to solutes. Plasma osmolarity increases (water loss)
3) U/P= >1 (hyperosmotic): Water is held back and solutes are lost. Plasma osmolarity decreases

Question 29

Kidney anatomy

Answer 29

1) Renal cortex- layered outer surface
2) Renal medulla- inner layer
- 2 zones: Outer ( close to cortex) and inner ( close to renal pelvis)
3) Renal pelvis- connected to ureter
- ureter: connects to bladder
4) Capillaries and arteries carry water and solutes to the blood
5) Bowman’s capsule: holds capillaries and blood will get squeezed out of the capillaries to be filtered into Bowman’s capsule
- proximal tubule: closest to BC
- distal convoluted tubule: dumps into the collecting ducts

Question 30

3 things happen in the kidney

Answer 30

1) Glomerular filtration: each human kidney filters 120 mL/min or 180 L per day (entire blood volume 72 times a day)
2) reabsorption of solutes and water
- to maintain proper blood osmolarity and volume (5 liters at 300 mOsm)
3) Secretion of a particular substance
- for substances not filtered such as large proteins

Question 31

Kidney Terms

Answer 31

1) Filtrate: what’s filtered into the tubules of the nephron at BC. Similar in ions and small molecules to blood plasma. Lower osmolarity because large molecules aren’t in the filtrate
2) Definitive urine: what exits to the bladder
3) Key: most of what is reabsorbed from the filtrate to the IF must also be reabsorbed back into the plasma
4) Ultrafiltration: The pressure drived process of driving water and some solutes from the blood to bowman’s capsule. This bulk flow is driven by hydrostatic pressure rather than osmosis. Stronger hydrostatic pressure in the capsule offsets colloid pressure gradient towards the blood

Question 32

Vertical osmotic pressure gradient

Answer 32

1) Found in the IF of the renal medulla
- higher osm than salt water (1200 mOsm)
- cortex= Na and Cl
- medulla= Na, CL, and urea due to urea recycling between filtrate and the ECF ( our inner shark)

Question 33

Countercurrent Exchange

Answer 33

1) The single effect and the end to end gradient generated from it by countercurrent multiplication
2) Multiplication: different osmotic potential between cortex and medulla&raquo_space;> difference in osmotic potential between ascending and descending limb
- the single effect of moving some solute horizontally is much more than the concentrating effect w/in the loop
3) You need to move solute to move water
- active transpory of NaCl out of ascending limb will draw water out of the descneding limb
- the horizontal flow of solute and water and countercurrent flow creates a highly effective reapsorbption mechanism
- the single effect is happening all down the vertical loop= countercurrent multiplication

Question 34

Factors affecting the osmotic gradient of interstital fluid

Answer 34

1) NaCl is actively transported out og distal and proximal tubules
2) Osmotic water reabsorption from upper tubules
3) Urea diffuses out of lower portion of the collecting duct raising the osm potential inner medulla
4) Water reapsorption from the descending limb makes the urine at the bottom of the loop very concentrated
5) NaCl diffuses out of thin portion of the ascending limb
- osmosis facilitated by aquaporins

Question 35

Reapsorption in the Nephron

Answer 35

1) Proximal tubule
- 70% of NaCl is reabsorbed via active transport
- 65% of the water “follows” NaCl via osmosis
2)Descending Limb
- no NaCl active transport
- low permeability to both NaCl and urea
- permeable to water… therefore, mostly water is reabsorbed via osmosis
3) Ascending limb (thin portion)
- no NaCl active transport
- low permeability to both NaCl and urea
- permeable to water… therefore, mostly water is reabsorbed via diffusion
4) Ascending limb (thick portion)
- NaCl is actively transported
- Low permeability to urea and water… therefore, mostly salt is reabsorbed via active transport
5) Distal Tubule and Upper collecting duct ( cortex)
- NaCl is actively transported
- water permeability is ADH-dependent… therefore, moslty salt is reabsorbed via osmosis in the presence of ADH
6) Lower collecting duct ( in the medulla)
- water permeabilty is still ADH-dependent
- urea permeabilty is high… therefore, water is reabsorbed via osmosis in the presence of ADH and some urea is reabsorbed increasing the osmolarity of the medullary interstitial fluid

Question 36

Homeostasis

Answer 36

• The process by which the body maintains a stable internal environment despite external or internal challenges
• Homeostasis is maintained through a negative feedback mechanism which resists change to regulated variables
  
  • requires sensors to “sense” change/ measure variable
• integrating center to compare the sensed variable to a set point or range
• effectors to resist the change (neg feedback) and restore the regulated variable to set point
• can have anticipator built in to activate corrective responses before the internal variable is disturbed

Question 37

regulation of blood volume

Answer 37

• In the mammalian kidney, water conservation can be achieved in 2 ways
  1) decreasing the resistance to osmosis: vasopressin/ADH: increases water reabsorption and is released from the pituitary gland
  2) increase the osmotic potential gradient or driving force for osmosis: aldosterone( increases Na reabsorption at kidney) released by the adrenal glands
• ADH and aldosterone are synergistic hormones
• chemical signals act over short and long distances
• for a hormone to affect an organ or tissues, the cells must have a receptor specific to the hormone

Question 38

Diruresis vs anti

Answer 38

1) Diruresis: low ADH ( lots of water loss)
2) Antidiruresis: high ADH (more water retention leads to an increase of blood volume)
- concentrated urine because solvent is removed… collecting duct walls are highly permeable to water (decreases U/P)

Question 39

ADH permeability

Answer 39

1) ADH binds to its receptor on collecting duct
2) a second messenger acts to shuttle storage vesicles to the membrane (CAmp)
3) storage vesicles fuse w/ apical membrane to incorporate AQ P-2 channels (aquaporins)
4) Water follows its osmotic potential gradient through AQ P-2 into epithelial cells and ECF through AQP-3
5) Water moves through ECF into the blood through spaces between capillaries endothelial cells

Question 40

Urea Retention

Answer 40

1) urea requires a transport molecule to cross the tubular wall
2) ADH causes insertion of more UI-Al transporters into the lower collecting duct
- this increases osmotic gradient= an increase in water retention

Question 41

Aldosterone Function

Answer 41

1) increases the driving force of osmosis (increases Na reabsorption)
- this increases ECF which leads to higher blood pressure

Question 42

Angiotensin II

Answer 42

• stimulates constriciton of arterioles, promotes thirst, stimulates ADH secretion
  
  • upregulates Na/K pumps
  • upregulates sodium channels
• upregulates NKCC (NaCl symporter)
• stimulates sodium reabsorption from the gut
• lowers plasma K concentration

Question 43

Antagonistic hormones

Answer 43

1) ANP (atrial natiuretic peptide): promotes diruresis
- secreted after atrial stretch (increase in blood volume)
- Na and H2O secretion, decreases blood pressure and volume

Question 44

drugs and pathologies

Answer 44

1) caffeine causes diruresis by inhibiting salt reabsorption = decrease in osmotic potential
2) Alcohol inhibits ADH secretion: causing a decrease in water permeability in the distal tubules and collecting duct and decrease in osmotic potential gradient (less urea recycling)
3) Insulin-dependent diabetes mellitus : autoimmune destruction of insulin secreting cells in pancreas
- symptoms
- hyperglycemia ( increase in blood sugar)
- glucosuria ( glucose in urine)
- polyuria (increase in urine)
- polydipsia (increase in thirst)

Question 45

Diabetes insipidus

Answer 45

1) produces large amounts of urine (up to 20 L a day and increased thirst)
4 causes
1) central: lack of ADH (use desmoporessin)
2) nephrogenic: kidney doesn’t respond to vasopressin
3) dipsogenic: abnormal thirst mechanism in hypothalumus
4) gestational: only during pregnancy. excessive vasopressinase (use desmopressin)

any hormonal malfunction due to receptors leads to higher levles of said hormone

Question 46

blood flow

Answer 46

1) blood enters the heart through the atria
- left atria carries blood to left lung
- right atria carries blood to right lung
2) Superior vena cava: carries blood to the heart from the upper body
3) inferior vena cava: carries blood to the heart from the lower body
4) atrial contraction pushes blood to the ventricles
5) ventricle contraction pushes blood out of the heart

Question 47

Cardiac cycle

Answer 47

1) atrial systole: P wave ( depolarization of atria (atrial contraction) increases atrial pressure and increases ventricular volume
2) Ventricular systole: QRS complex (depolarization of ventricles (ventricular contraction) increases ventricular pressure, isovolumetric contraction(volume stays the same because all valves are closed), until the semilunar valve opens
3) greater than 80 mmHg the aortic valve opens and ventricular volume goes down (ejection)
4) T wave: ventricular repolarization: pressure decreases, valves close (relaxation), isovolumetric relaxtion: valves closed, pressure drops.
once ventricular pressure is below atrial pressure, the mitral valve opens. Blood coming back passively fills the vents