26 Lecture 28 Oct, 2009 Osmoregulation and excretion
Today at
TODAY
Dr. Sarvarys office hour will be cancelled today. Instead, he will have office hours tomorrow (Thursday) 2-3pm.
Lecture final examination is on December 11th, 911.30 am Final exam makeup is on December 14th, 9-11.30 am
Circulation Respiration, Concepts & Terms
albumin alveolus arteriole artery atrioventricular valve atrium bicarbonate blood blood pressure blood vessels Bohr shift breathing control center capillary capillary bed carbonic acid cardiac cycle cardiovascular system cooperativity closed circulatory system diastole diastolic pressure dissociation curve double circulation erythrocyte erythropoetin EPO gas exchange gastrovascular cavity heart rate hemocyanin hemoglobin hydrostatic pressure interstitial fluid kwashiorkor lymph node lymphatic system medulla myoglobin open circulatory system osmotic pressure partial pressure plasma pons red blood cell respiratory pigment semilunar valve systemic circuit systemic circulation systole systolic pressure trachea tracheal system vein vena cava ventilation ventricle venule
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Course announcement
Incorrect web quiz answer
Which one of the following choices names an item which does not normally get translocated through plasmodesmata? A B C D E disaccharides, such as sucrose. trisaccharides, such as raffinose Water Amino acids Minerals
Where we were going
1. Open circulatory systems 2. Comparative vertebrate circulatory systems 3. Blood pressure and flow 4. Gas exchange 5. Control of breathing
Answer A for proper credit, But B is the correct answer
Velocity, area, and pressure differ in various parts of the circulatory system
Fluid exchange between capillaries and interstitial fluid depends on balance of hydrostatic and osmotic pressures
tissue cells
interstitial fluid
15 m
Cross sectional
hydrostatic pressure osmotic pressure
(esp. proteins)
Poor regulation of osmotic pressure leads to adverse health
Blood is a complex tissue composed of cellular and non-cellular (humoral) elements
hydrostatic
Pressure
Lack of protein in diet can lower osmotic pressure
osmotic
Movement through capillary bed
Kwashiorkor: edema from hypoalbuminemia
Red Blood Cells
Erythrocytes (RBCs) Bi-concave disks (diameter: 7 Specialized to carry O2
lack nucleus (mammals), Golgi, mitochondria loaded with hemoglobin (2.5 x 108)
Hemoglobin
globular protein 4 subunits (2 x 2) Heme groups with Fe atom reversibly bind O2
m)
Amount of O2 bound depends upon oxygen partial pressure
Dissociation curve for hemoglobin
O2 unloaded during resting metabolism
pH also affects dissociation curve (the BOHR shift)
High pH (basic): curve shifts to left. Low pH (acid): curve shifts right.
steep slope reveals cooperativity among 4 subunits
O2 available to high demand tissues
pH is much lower in tissues than lung. O2 bound less tightly CO2 + H 2O H 2CO3 H + + HCO3
Bohr shift helps load and unload hemoglobin
from tissue
Brainstem circuits control breathing
Pons sets the tempo Medulla circuit(s) establish rhythmic breathing pattern Inhalation: contraction of diaphram, intercostal (rib) muscles. negative pressure Exhalation: relaxation of muscles
Phrenic nerve
Low PCO2
Chemical control of breathing
Extreme gas concentrations control breathing by negative feedback
Increase in breathing rate is mediated by High PCO2 , low pH receptors on surface of the medulla & major vessels very low PO2 receptors on carotid artery, aorta
Where were going
1. Conformers and regulators
2. Nitrogenous wastes 3. Mammalian kidney high pressure filtration 4. Mammalian kidney selective reabsorption
Osmoconformers
no homeostasis. cells are isoosmotic with environment. the stable environments typically marine
Osmoregulators
Environmental conditions vary over time. Internal conditions regulated at relatively constant level
environment internal environment
homeostasis
but it comes at a cost
Cost of homeostasis is high when:
Steep gradient between internal & external environment Permeable integument
Male moths, Gluphisia septentrionalis, selectively filter Na+ from mud puddles
Large surface area/volume Evaporative cooling is necessary
Excretion of nitrogenous wastes
Other moths also exploit unusual habitats to acquire adequate Na+
Nitrogenous waste products have different costs and benefits
Property
Excretion involves four functions
and is typically done by tubular systems that run past each other
The mammalian Kidney
Posterior vena cava Renal artery and vein Aorta Ureter Urinary bladder Urethra (a) Excretory organs and major associated blood vessels JuxtaCortical medullary nephron nephron Kidney Renal medulla Renal cortex Renal pelvis Ureter (b) Kidney structure
The nephron and collecting duct: regional functions of the transport epithelium
1 Proximal tubule NaCl Nutrients HCO3 H2O K+ NaCl 4 Distal tubule H2O HCO3
H+
NH3
K+
H+
Section of kidney from a rat Afferent arteriole from renal Glomerulus artery Bowmans capsule Proximal tubule Peritubular capillaries
Filtrate filtrate
high pressure
H2O Salts (NaCl and others) HCO3 H+ Urea Glucose; amino acids Some drugs
CORTEX 2 Descending limb of loop of Henle H2O 3 Thick segment of ascending limb NaCl NaCl 3 Thin segment of ascending limbs NaCl INNER MEDULLA 5 Collecting duct Urea H2O
Renal cortex
Collecting duct
OUTER MEDULLA
via aquaporins
20 m Renal medulla
To renal pelvis
SEM Efferent arteriole from glomerulus Branch of renal vein Descending Loop limb of Ascending Henle limb (d) Filtrate and blood flow
Distal tubule Collecting duct
Key Active transport Passive transport
(c) Nephron
Vasa recta countercurrent to loop
hyperosmotic 0.1% of filtrate volume
How the human kidney concentrates urine
resorb nutrients adjust pH
300 300 100 CORTEX Active transport Passive transport OUTER MEDULLA H2O H2O H2O H2O H2O H2O INNER MEDULLA H2O 1200 1200 900 700 900 1200 400 600 400 200 400 400 100 300
How the human kidney concentrates urine
resorb nutrients adjust pH
300 300 100 100 CORTEX Active transport Passive transport OUTER MEDULLA H2O H2O H2O H2O H2O H2O INNER MEDULLA H2O 900 400 NaCl NaCl NaCl NaCl NaCl NaCl NaCl 1200 700 900 1200 200 300
regulate ions (Na+/K+) adjust pH Osmolarity of
interstitial fluid (mosm/L) 300
regulate ions (Na+/K+) adjust pH Osmolarity of
interstitial fluid (mosm/L) 300
400
400
600
600
600
400
600
600
1200
How the human kidney concentrates urine
resorb nutrients adjust pH
300 300 100 CORTEX Active transport Passive transport OUTER MEDULLA H2O H2O H2O H2O H2O H2O INNER MEDULLA H2O 900 400 Nacl Nacl Nacl Nacl Nacl Nacl Nacl 700 200 H2O H2O H2O 400 H2O H2O Urea H2O Urea H2O Urea 600 400 100 300
regulate ions (Na+/K+) adjust pH Osmolarity of
interstitial fluid (mosm/L)
Thirst
Osmoreceptors in hypothalamus trigger release of ADH.
Homeostasis of water/salt balance is maintained by hormonal negative feedback on kidney function
Hypothalamus
300
Drinking reduces blood osmolarity to set point.
ADH Pituitary gland
COLLECTING DUCT LUMEN INTERSTITIAL FLUID
Increased permeability
400
Distal tubule
COLLECTING DUCT CELL cAMP
ADH ADH receptor
600
600
900 1200 1200
H2O reabsorption helps prevent further osmolarity increase. Collecting duct
STIMULUS: Increase in blood osmolarity Exocytosis H2 O
Second messenger signaling molecule
Storage vesicle Aquaporin water channels H2 O
1200
-
Homeostasis: Blood osmolarity (300 mOsm/L)
+
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