Biology 2672a: Comparative Animal Physiology

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Biology 2672a Comparative Animal Physiology

• Final review lecture

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The Final Exam

• 9 am December 8th
• Talbot Hall Gym
• 2 hours
• If you are sick (etc)
• Take documentation to the Deans counsellors
  they will contact me.
• If in doubt, sit the exam then see the Dr.

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The Final Exam

• 73 Questions
• Covers everything from Lecture 2 (Krogh Principle
  etc) to Lecture 24 (Diving mammals)
• Including animal ethics, freezing frogs,
  hibernation, migration and bird song
• Includes labs (c. 3-5 questions)
• No overt weighting on any part of the course

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The final exam

• 40 simple definition-type questions
• 10 harder single-part questions
• 5 fun graph questions (multiple parts)

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The Make-up

• 7 pm (in the evening!)
• Monday 12 January
• Will include written answers, as per the course
  outline
• Format will be sent in advance to those writing
  the make-up
• If you cant do the make-up, the next exam will
  be in December 2009

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How your mark is calculated

• Added up (by the computer) and rounded to the
  nearest integer
• Nearest integer to (e.g.) 69.45 is 69 (sorry)
• I DO give 89, 79, 69
• I DONT give marks for arbitrary reasons (so
  please dont ask)

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Important things to remember

• READ THE QUESTION!
• READ THE ANSWER!
• LOOK AT THE GRAPH!
• Just because something sounds the most scientific
  doesnt mean it is true
• Im very good at generating meaningless jargon!

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Today

• Five topics
• Control of vasomotor tone
• Freshwater/saltwater fish
• Malpighian tubules
• Concentrating urine
• Freezing frogs

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Regulation of circulation
Change tube diameter
Change Energy input
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Local control

• Myogenic stretch response
• Paracrine control
• e.g. release of NO
• Responses to local conditions and trauma
• Events in muscle cell
• viagra example

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Central control

• Endocrine (Hormonal)
• e.g. Adrenaline (Epinephrine)
• Response depends on receptor densities, so same
  hormone has different effects through body
• Also vasopressin and angiotensin
• Neural
• Sympathetic nervous system
• Usually chemically mediated.

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From Fall 2007 Final Exam

• The release of Epinephrine by the adrenal glands
  is an example of paracrine control of vasomotor
  tone
• True
• False

13
The situation for a marine teleost
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Chloride cells
Apical (Mucosa)
Water
Pavement cell
Lots of mitochondria
Baso-lateral (serosa)
Blood
Fig. 26.6
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Export of Chloride is driven by a Na gradient
Na actively pumped out of cell by Na,K-ATPase
Potassium remains at equilibrium because of K
channels back into blood
Box 26.2
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Active removal of Cl- leads to an electrochemical
imbalance that drives Na out of blood via
paracellular channels
Box 26.2
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Chloride cell summary

• Transcellular transport of Cl-
• Driven by Na,K-ATPase (requires energy)
• Paracellular transport of Na
• Ionoregulation accounts for 3-5 of resting MR
  in marine teleosts

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Salt Water Fresh Water
Drinking Lots
Urine Little, concentrated
Ion flux Passive into fish active out of fish
Na,K-ATPase Na into bloodstream
Tight junctions No
Cl- Transcellular transport driven by Na gradient
Na Paracellular driven by electochemical gradient
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The situation for a freshwater teleost
Fig. 26.7a
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Na uptake
Note tight junction
Box 3.1 Fig.A(2)
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Cl- uptake
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NaCl uptake summary

• Exchange for CO2
• Na via electrochemical gradient
• Cl- via HCO3- antiport
• Very dilute urine gets rid of excess water
  without losing too much salt

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Salt Water Fresh Water
Drinking Lots Little
Urine Little, concentrated Copious, dilute
Ion flux Passive into fish active out of fish Passive out of fish, active into fish
Na,K-ATPase Na into bloodstream Na into bloodstream
Tight junctions No Yes
Cl- Transcellular transport driven by Na gradient Transcellular via HCO3- antiporter (driven by H pump)
Na Paracellular driven by electochemical gradient Transcellular driven by electrochemical gradient (set up by H pump and Na,K-ATPase)
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From Final Exam, Fall 2007

• In gills of a freshwater-acclimated fish, where
  is the Na,K-ATPase pumping Na ions?
• a) From the chloride cell into the bloodstream.
• b) From the chloride cell into the surrounding
  water.
• c) From the bloodstream into the chloride cell.
• d) From the surrounding water into the chloride
  cell.
• e) From the surrounding water into the
  bloodstream.

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From final exam, Fall 2007

• As well as an increase in Na,K-ATPase activity,
  what else would you expect to happen as a fish
  moves from fresh to salt water?
• The closure of gap junctions between pavement
  cells.
• Increased activity of the Cl-/HCO3- antiporter in
  chloride cells.
• Expression of chloride channels on the apical
  (mucosal) surface of the chloride cells.
• Removal of K channels from the basal (serosal)
  surface of the chloride cells.
• Increase in gill surface area.

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Malpighian tubules
Cells
Haemolymph
Lumen
Fig 27.21
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Haemolymph
Stellate cell
Principal cell
Mitochondria packed into evaginations
Lumen
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Haemolymph
K Channel

• Proton pump generates electrochemical gradient
• Requires ATP
• K follows via electrogenic transporter

V-ATPase (H pump)
Lumen
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Haemolymph
Cl- Channel

• Cl- follows K gradient
• Water follows osmotic gradient into tubule lumen

Aquaporin
V-ATPase (H pump)
Lumen
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Malpighian tubules summary

• Active transport sets up ion gradients
• Proton pump K, Cl-
• Water follows
• Passive transport of nitrogenous wastes, amino
  acids etc. down electrochemical gradients
• Active transport of large molecules
• Alkaloids, proteins etc.

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Water and solute reabsorption

• Urine from tubules is dilute and contains lots of
  things the insect doesnt want to lose
• Reabsorption of water and solutes in
  hindgut/rectum
• Determines final concentration of the urine

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Final exam, Fall 2007

• Chloride ions pass from the haemolymph to the
  lumen of the Malpighian tubule largely via the
  Principal cells.
• True.
• False.

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New Question

• Chloride concentrations are high in the lumen of
  the Malpighian tubule because...
• Active transport of chloride ions from the
  haemocoel by the stellate cells.
• The chloride ions follow an electrochemical
  gradient set up by sodium pumping in the
  principal cells.
• The chloride ions follow an electrochemical
  gradient set up by proton pumping in the
  Principal cells.
• All of the above.
• None of the above.

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Concentrating Urine
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Bowmans capsule Ultrafiltration, Production of
primary urine
Thick ascending loop of Henle
Salt Re-absorption
Thick segment of descending loop of Henle
Collecting Duct
Urine out, concentration of definitive Urine
Re-absorption of sugars, amino acids, water
Loop of Henle
Thin segment of descending loop of Henle
Thin ascending loop of Henle
Fig. 27.6
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Concentration gradient in kidney
Fig. 27.13
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Concentration of urine

• Occurs in collecting ducts
• Driven by osmotic gradient across kidney
• Both urea and salts
• Can be manipulated by altering permeability of
  collecting duct to water

Fig. 27.14a
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Changing concentration of definitive urine
Fig. 27.14
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Medullary thickness is positively correlated to
maximum urine concentration
Fig. 27.8
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Concentrating Urine

• Bigger concentration gradient higher maximum
  concentration of urine
• Longer loop of Henle (i.e. relatively thicker
  medulla) longer concentration gradient higher
  maximum concentration of urine

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Modulating urine concentration

• Modulate permeability of collecting duct to water
• Permeable
• Concentrated urine
• Antidiuresis
• Impermeable
• Dilute urine
• Diuresis

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Final exam Fall 2007

• A longer loop of henle allows for a shorter
  concentration gradient, increasing kidney tubule
  efficiency.
• True.
• False.

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Final Exam, Winter 2007

• Which change is primarily responsible for the
  shift in production from concentrated to dilute
  urine?
• Increased absorption of amino acids by the
  descending loop of Henle.
• Decreased absorption of amino acids in the
  descending loop of Henle.
• Increased permeability of the collecting duct.
• Decreased permeability of the collecting duct.

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To freeze a frog
Freezing initiated
Massive conversion of glycogen to glucose (liver)
and circulation around body (Glycogen
phosphorylase)

• Protein Synthesis slows to 1
• Pumps channels closed
• Energy Production slows to 5
• Energy Utilization slows to 2
• Few SAP kinases activated
• Gene inactivation (mRNA)
• Few Genes activated
• NRF-2 ( more antioxidants, especially GST)

Dehydration of major organs (water relocated to
the coelom and lymph system)
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New Question

• Freezing in frogs results in decreased production
  of NRF-2 and subsequent gene activation.
• True.
• False.