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Lecture 23, 07 Nov 2006

Vertebrate PhysiologyECOL 437 (MCB/VetSci 437)

Univ. of Arizona, Fall 2006

Kevin Bonine & Kevin Oh

http://eebweb.arizona.edu/eeb_course_websites.htm

1. Osmoregulation(Chap 25-26)

2. Kidney Function(Chap 27)

(Eckert 14-17)

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Housekeeping, 07 Nov 2006

Upcoming Readings

today: Text, Ch. 25-27 (osmoregulation, kidney)

Wed 08 Nov: Kidney/Urine lab, (Heart), Term Paper Thurs 09 Nov: Text, chapter 25-28, kidney, excretion, deserts Tues 14 Nov: begin 4+5 (feeding, nutrition, metabolism)?Thurs 16 Nov: Exam 3

Lab oral presentations 08 Nov9am – none2pm – none

Kidney/Urine Lab on 08 November, Term Paper drafts (2 with codenames)Don’t forget to do seminar write-up! (due 10 November)

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Osmoregulation-Ionic and Osmotic Balance

-Kidney Function

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Osmoregulation

Vertebrate Physiology 437

(Eckert, 14-18)

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Osmoregulation

-life arose in salty sea-extracellular fluids ~ similar

-terrestrial organisms (and their descendents) regulate internal environment (homeostasis)

-salt and water regulation (waste excretion)

-dist’n limited by temperature and osmotic pressure(dehydration, ionic composition)

-kidneys, salt glands, gills

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Obligatory Osmotic Exchanges

2-Surface-to-Volume Ratio-Small animals dehydrate or hydrate more rapidly

-Skin, and Respiratory surface(higher metabolism with higher per/gramrespiratory surface)

3-Integument Permeability-Transcellular or Paracellular-Aquaporins = water channel proteins

1-Gradients-Frog in freshwater-Fish in ocean

-Frogs vs. Lizards, Pelvic Patch etc.

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Obligatory Osmotic Exchanges

4-Feeding, Metabolism, Excretion-metabolic waste products

ammonia, urea, etc.-metabolic water (desert!)-ingestion of salts-kidneys, salt glands, gills (more later)

5-Respiration

-internalize respiratory surface-temporal countercurrent system

(dry and cool IN, becomes moist and warm; recover)(countercurrent blood flow also)

-temperature regulation vs. water conservation-ectotherm vs. endotherm (in deserts)

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Osmoregulation

-Water Breathing

1. Fresh

Blood osmolarity 200-300 mosm/LWater ~ 50 mosm/L

- hyperosmotic animals, danger of swelling, losing salts- get their water across skin- dilute urine- active uptake of salts across epithelium- fish gills, frog skin, etc.

Ambystoma tigrinum

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Osmoregulation

-Water Breathing

2. Salt

Most marine vertebrates hypo-osmotic (e.g., teleost or bony fishes)

- danger of losing water, gaining too many salts- drink saltwater- excess salts actively secreted (gills, kidneys)- chloride cells for salt secretion

(Pelis et al. paper)

(~1,000 mosm/L)

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Osmoregulation

-Air Breathing

Have to lose water to allow gas exchange

- Marine reptiles and marine birds can drink seawater and secrete salts in high [ ]

- SALT GLANDS

- Mammals rely on kidney

(14-8)

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Hill et al. 2004, Fig 26.15

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(16-7)Mouse-to-Elephant Curve

4g shrew eats 2g/day

elephant is 1 million x larger

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Free

Preformed

Metabolic

Water

C6H12O6 + 6O2 6CO2 + 6H20

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Oryx

Camel

K-rat

Hopping Mouse

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K-rat

Lab rats

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ORGANS THAT CONTRIBUTE TO OSMOREGULATION IN VERTEBRATES

Group Osmoregulatory Organs Fish Kidneys Gills Bladder Intestine Amphibians Kidneys Gills Bladder Skin Intestine

Reptiles Kidneys Salt Glands Intestine Birds Kidneys Salt Glands Intestines Mammals Kidneys

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Osmoregulation

-Air Breathing Desert Mammals

Behavior and Physiology

Kangaroo Rat-Reduce Activity-Remain in Cool Burrow-Highly concentrated urine-Very dry feces (rectal absorption)-Metabolic water

(Eckert 14-9)

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Water

Lose water:evaporationurinefecessalt glands

Alter behavior and physiology to minimize water lossWater balance limits activity in time and space

Amphibs lose most water via evaporation- cutaneous resistance

1 dried mucus2 cocoon3 wax

Eleutherodactylus coquiPough et al., 2001

Role ofmicrohabitat

eyes

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19Pough et al., 2001

PhyllomedusaPhyllomedusa sauvagi

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Moreevap.

Lessevap.

Pough et al., 2001

Chuckwalla (lizards have more lipids in skin)

Monkey Tree FrogAnolis lizard

Alligator

Softshell Turtle

Bufo, Spadefoots, Rana

Water

(free water surface)

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Volume Regulation

Osmotic Regulation

Ionic Regulation

Kidney Function

How do these differ?

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Osmoregulatory MechanismsApical surface (faces lumen and outside world)Basal surface (faces body and extracellular fluid)

- Active movement of ions/salts requires ATP- Movement of water follows movement of ions/salts

(14-11)

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Gradients established and used…to move ions, water

(Eckert 14-12)

active

passive

Mammalian Kidney

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Fish Gills Chloride cells involved in osmoregulation-(recall lab paper on smolting)-lots of mitochondria to power ATPases-mechanism similar in nasal glands (birdsand reptiles), and shark rectal gland

(14-14)

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Kidney Functions:

-Osmoregulation-Blood volume regulation-Maintain proper ion concentrations-Dispose of metabolic waste products-pH regulation (at ~ 7.4)-Dispose of toxins and foreign substances

How does the kidney accomplish this?

(Eckert 14-17)

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(Eckert 14-17)Mammalian Kidney

-Paired-1% body mass-20% blood flow

-from ureter to urinary bladder(smooth muscle, sphincter, inhibition)

-out via urethra during micturition

-urine contains:watermetabolic byproducts (e.g., urea)excess salts etc.

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(Eckert 14-17)

Mammalian Kidney Anatomy

FUNCTIONAL UNIT(~ 1 million)

Urine

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extracellular

intracellular

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Hill et al. 2004, Fig. 27.6

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-numerous nephronsempty into collecting duct

-collecting ducts empty into renal pelvis

1 -Proximal tubule2 -Loop of Henle

-descending-ascending

3 -Distal tubule

Nephron Anatomy

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31Knut Schmidt_Nielsen 1997

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Nephron Anatomy

32Knut Schmidt_Nielsen 1997

Vasa recta

Countercurrent exchange

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(Eckert 14-21)

1. FILTRATIONblood --> filtrate

2. REABSORPTIONfiltrate --> blood

3. SECRETIONblood --> filtrate

All 3 involved in finalUrine Composition

Kidney Processes- overview

34Knut Schmidt_Nielsen 1997

Filtration plus secretionU/PMosm = x1000

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Dipodomys

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35Hill et al. 2004, Fig 25.7

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(14-20)

Sympathetic innervation tends to constrict

Humans:125 ml/min

or180 L/day

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Filtration:

Bowman’s capsule3 layers1. Glomerular endothelial cells

-100x leakier than other capillary walls2. Basement membrane

-negatively charged glycoproteins-repel plasma proteins by charge

3. Epithelial cells-podocytes create slits

Glomerular Filtration Rate (GFR)Humans: 125 ml/min or 180 L/day (60x plasma vol.)

Filtrate = protein-free and cell-free plasma

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Bowman’s capsule

(Eckert 14-23)

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(Eckert 14-22)

proteins and larger molecules remain

About 20% of the plasma and solutes that enter glomerulus end up in BC

Bowman’s capsule