Ion and Water Balance

Question 1

What are the three homeostatic processes?

Answer 1

Osmotic Regulation: Water
Ionic regulation: Ions
Nitrogen excretion: Excretion

Question 2

What are the strategies to cope with ionic & osmotic challenges

Answer 2

Ionoconformer: exert little control over the solute profile within the extracellular space (marine)

Ionoregulator: control ion profile of extracellular space = use active mechanisms

Osmoconformer: internal and external osmolarity are similar

Osmoregulator: osmolarity is constant regardless of external environment

Question 3

What is osmolarity?

Answer 3

Osmolarity: indication of the total solute concentration. Measure of the total # of solute particles per unit volume.

Question 4

What is Tonicity? What are the types of tonicity?

Answer 4

Tonicity: The ability of a solution to cause a cell to shrink or swell. Depends of non-penetrating solutions

Isotonic: happy cells
Hypertonic: cells shrink
Hypotonic: cells burst

Question 5

What is Dietary Water? Metabolic Water?

Answer 5

Dietary: water performed in plant and animal tissues
Metabolic: water generated as a result of oxidative phosphorylation

Question 6

How do Animals compensate for ion and water movements?

Answer 6

By active transport of ions.

Primary Osmoregulatory epithelium of vertebrates are gills, kidney, and digestive system

Question 7

How do Sharks maintain osmolarity?

Answer 7

Shark blood contains high levels of urea and TMAO (Trimethylamine oxide)

Maintains blood osmolarity slightly higher than seawater

Gill has specializations to reduce permeability to urea. Sharks gain H2O passively and use urea as a somolyte to increase osmolarity

Using Urea alone would be toxic, needs TMAO

Question 8

How to Marine mammals differ from Terrestrial mammals? Desert?

Answer 8

Marine Mammals: Do not drink sea water, hyperosmotic (similar to desert)

Terrestrial Mammals: replace lost water through eating and drinking

Desert Mammals: Have little access to freshwater and has efficient kidneys

Can produce concentrated urine to conserve water

Question 9

What epithelia are involved with ion and water balance? What else are they involved with?

Answer 9

Gills and Kidneys are also involved in the excretion of nitrogenous waste.

Protein catabolism (breakdown) generates ammonia (NH3)

Question 10

What forms is Amino Acid breakdown is excreted as?

Answer 10

Ammonia, Urea, Uric Acid

Question 11

What do Mammals produce when dehydrated? Alligators?

Answer 11

Mammals: Dehydrated = produce Uric Acid when = gout

Alligators: Hydrated = produce NH4HCO3 (Ammonium Bicarbonate) Dehydrated = produce Uric Acid

High Uric Acid can lead to gout in animals that dont normally excrete it

Question 12

Summary of Ammonia

Answer 12

Aquatic Animals avoid ammonia poisoning by dissolving it in large amounts of H2O

Diffuses across gill epithelium/permeable membrated bathed by H2O

Question 13

Summary of Urea

Answer 13

Urea is soluable in H2O and moderately toxic

Can accumulate Higher levels in tissues w/o damage

excreted in concentrated form and requires energy (pee)

Question 14

Summary of Uric Acid

Answer 14

Uric Acid is ALMOST insoluble in water

In Cloaca, uric acid joins with ions and precipitates out. Little H2O loss

Nontoxic if doesn’t accumulate, 15 rxn each catalyzed by enzyme = lots of energy to cause rxns.

Question 15

What are the Functions of the Kidney?

Answer 15

Ion Balance
Osmotic Balance
Blood pressure: a change in blood volume = change in BP
pH Balance: H+
Excretion: helps detoxify
Hormone production: Erythropoietin Calcitriol, Adrenal glands
Gluconeogenesis: making glucose form non-carb stuff (amino acids)

Question 16

How do Kidneys make glucose via gluconeogenesis

Answer 16

Amino Acids involved: Lactate, Glutamine, Glycerol, Alanine

Catecholamines = stimulus for gluconeogenesis

Renal Medulla: enzymes that help break down glycogen

Renal Cortex: enzymes that make glucose from non-carb

Question 17

What is the kidney structure?

Answer 17

Crescent shaped with the cortex and medulla
Cortex: Bowman’s capsule, Proximal Tubule, Distal Tubule

Medulla: Collecting Duct, Loop of Henle

Question 18

What is the Nephron? Nephron Vasculature?

Answer 18

Nephron: functional unit of the kidney, tubular system

Nephron Vasculature:
Afferent Arteriole = Leads to glomerulus
Glomerulus = Twisted ball of Capillaries (little ball)
Efferent arteriole = leads away from glomerulus
Peritubular Capillaries =
Vasa recta =deeper

Question 19

Explain the juxtaglomerular apparatus

Answer 19

proximal convoluted tuble cells have mirovilli

Juxtaglomerular Apparatus: regulate BP in Kidney
- Jux cells: cells of afferent and efferent
arterioles have modified smooth muscle fibers

Principal Cells: receptor proteins for antidiuretic hormone (ADH) and Aldosterone (on distal convoluted tubule)

Question 20

Explain Juxtaglomerular Complex

Answer 20

Juxtaglomerular Complex: endocrine structure that secretes hormones and renin
- Hormone/Erythropoietin = released by jux
cells. Goes to red bone marrow to make RBC
- Renin = Enzyme released when BP is low
Macula densa sense NaCl flow change

Question 21

What are the 4 processes of Urine production?

Answer 21

Filtration
Reabsorption
Secretion
Excretion

Question 22

Where is Filtration? Explain it

Answer 22

Filtration: produces protein free solution similar to blood plasma

• passive through hydrostatic pressure. Forces water through membrane pores
• proteins and RBC are not filtered
• RBC whole in urine = kidney failure
• RBC lysed = organ failure other than kidney

Question 23

Filtration at Glomerulus?

Answer 23

• Glomerular capillaries = very leaky
• Podocytes = foot proccesses form filtration structure
• Mesangial cells = control BP & Filtration within glomerulus

Question 24

What is Filtration Pressure and what are the components?

Answer 24

Filtration Pressure: governed by balance btwn:
Glomerular Hydrostatic Pressure: BP seen @ A arteriole = favors

Capsular Hydrostatic Pressure: fluid within tubular system = opposes filtration

Colloid Osmotic Pressure: bc of proteins (albumin) = opposes filtration = draws fluid back to capillaries.

GHP-CHP-COP=Filtration pressure

Question 25

How do you regulate Glomerular filtration?

Answer 25

GFR = glomerular filtration rate regulate GFR by changing diameter of the afferent arteriole radius of EFFERENT arteriole decreases, GFR increase If afferent arteriola constricts = GFR Decreases - INCREASE radius @ A = INCREASE GFR - DECREASE radius @ A = DECREASE GFR - INCREASE radius @ E = DECREASE GFR - DECREASE radius @ E = INCREASE GFR

Question 26

What is the control of GFR?

Answer 26

GFR= automatically maintained 1. Autoregulation = when BP increases at afferent arteriole. Maintains GFR despite BP and blood flow changes (Myogenic and Tubuloglomerular mechanisms) 2. Hormonal regulation = Angiotensin II = potent vasoconstrictor Natriuretic peptides 3. Automatic regulation (by sympathetic division of ANS) Kidney blood vessels supplied by sympathetic ANS fibers release norepinephrine = vasoconstriction = reduce GFR

Question 27

How do we automatically constrict the afferent arteriole?

Answer 27

Stretch receptors open allowing sodium to enter and getting a depolarization leading to contraction of smooth muscles.

Question 28

How is filtration regulated in the Renin Angiotensin System?

Answer 28

- Low BP in the cells sensed by Juxtaglomerular cells -> release Renin RENIN: enzyme converting Angiotensinogen to Angiotensin I. Liver releases Angiotensinogen Angiotensin: Converting enzyme converts ANG I to ANGII, released by lungs. ACE inhibitors lower BP - ANG II = potent vasoconstrictor 1. Hypothalamus: feeling thirsty 2. Hypothalamus makes ADH 3. Adrenal cortex releases Aldosterone GFR decreases

Question 29

How is filtration regulated in ADH?

Answer 29

Stimulus: Low blood volume (detected by baroreceptors), increased blood osmolarity (detected by chemoreceptors from hypothalamus), Angiotensin II (from decrease in BP). Regulation: Hypothalamus increases nerve signals to posterior pituitary, release ADH into blood. Outcome: Blood pressure increase, blood osmolarity decreases.

Question 30

How is filtration regulated in Aldosterone?

Answer 30

Stimulus: Angiotensin II (decrease in BP), Decrease in Na+ blood plasma lvls, Increase K+ blood plasma lvls. Regulation: Adrenal cortex releases Aldosterone to blood Outcome: Na+ maintained, K+ decreases, Blood volume and BP maintained by decreasing urine output

Question 31

How is filtration regulated in Natriuretic Peptides?

Answer 31

Simulus: Blood volumed increased (increase stretch of baroreceptors in atria) Regulation: Atria releases ANP into blood Outcome: Peripheral resistance decreases, blood volume decreases, BP decreases. - leads to vasodilation - Increase GFR = pee out more H2O, - inhibit ADH synthesis. Aldosterone Not released - Don't feel thirsty.

Question 32

What does reabsorption look like in kidneys? Glucose? H2O?

Answer 32

- Useful materials recaptured before filtrate leaves kindeys. - Reabsorption occurs in proximal convoluted tubule. - Diffusion: small hydrophobic stuff - Osmosis: water - Channel-mediated diffusion = facilitated diffusion = ions/ 2ndary active transport = if keeping against gradients - Carrier mediated transport - Obligatory water reabsorption in the proximal tubule = not regulated by ADH = happens automatically to maintain osmolarity of blood leaving kidneys.

Question 33

What is the countercurrent mechanism in kidneys?

Answer 33

- Loop of Henle: juxtamedullary nephrons function as countercurrent multiplier. Increasing osmotic gradient as we move deeper towards loop of Henle - Descending limb = permeable to water, water leaves, increase osmolarity -Ascending limb = permeable to ions, ions leave, decrease osmolarity - Deeper = higher osmolarity

Question 34

What is a buffer?

Answer 34

- Buffer act quickly to temporarily bind to H+ - Do not prevent pH changes but will reduce or minimize them.

Question 35

What are the Buffer Systems?

Answer 35

Protein Buffer System: proteins (-) charged so they can bind to H+ - Most abundant buffer in ICF and blood plasma -Hemoglobin in RBC = review CO2 & Hemoglobin Carbonic Acid-Bicarbonate Buffer System: HCO3- = weak base & H2CO3 = weak acid - HCO3- = significant anion in ICF and ECF Phosphate Buffer System: Important regulator of pH in cytosol - H2PO4- & HPO4 2- = major anions in ICF and minor in ECF

Question 36

Acidosis v.s. Alkalosis

Answer 36

Acidosis: depression of synaptic transmission in CNS Alkalosis: overexcitability if CNS and peripheral nerves

Question 37

Respiratory Acidosis v.s. Respiratory Alkalosis

Answer 37

Respiratory Acidosis: Abnormally high PCO2 in systemic arterial blood - Inadequate exhalation of CO2 = Hypoventilate - Emphysema, Pulmonary Edema, Airway obstruction = decrease CO2 movement out - Kidneys pee out H+ Respiratory Alkalosis: Abnormally low PCO2 in systemic arterial blood - Causes Hyperventilation - Pulmonary disease, Stroke, Severe anxiety = Hyperventilation - O2 deficiency from high altitudes = Hyperventilation

Question 38

Metabolic Acidosis v.s. Metabolic Alkalosis

Answer 38

Metabolic Acidosis: Too much H+ - loss of HCO3- - Ketosis: accumulate acids other than carbonic acid - can hyperventilate Metabolic Alkalosis: Too little H+ - Nonrespiratory loss of acid (vomiting stomach acids) HCl=stomach acid - Dehydration - can hypoventilate, keep in CO2