Osmoregulation and Fluid Balance

Osmoregulation

• Involves maintaining water and salt balance in animal bodies through selective retention and excretion
• Needed because the intracellular aqueous environment impacts organic molecule function
• Protein function depends on ion concentration and is optimal within a narrow range

Fluid Compartments

• Intracellular fluids (ICF) are inside animal cells
• Extracellular fluids (ECF) exist outside animal cells, including interstitial fluid and blood plasma
• Fluids have different ions, electrolytes, and organic compounds, comprising over half the animal's body weight
• Osmoregulation happens through managing water in blood and interstitial fluid
• Regulating ECF saves individual cells from ICF disruptions, allowing cells to exist in a stable chemical environment

Ion Composition of Cells

• Most cells regulate this by using ATP

Water Permeability

• Most cells are permeable to water
• Cells can maintain ionic differences across membranes without osmotic differences

Transport Routes

• Transcellular transport moves substances through cells across membranes
• Paracellular transport moves substances between cells
• Epithelia can be classified as "leaky" or "tight"

Transporters

• Types include:
  • Na-K+ATPase
  • Ca2+-ATPase
  • Electroneutral cotransporters
  • Electroneutral exchangers

Water Movement

• Water travels from low to high solute concentration areas due to osmotic gradients

Osmolarity and Volume

• Osmolarity measures solute concentration, e.g. 1 mol glucose equals 1 osmol, and 1 mol NaCl equals 2 osmol
• Osmolarity changes create transmembrane osmotic gradients, affecting cell volume
• Water movement can cause cells to swell or shrink, affecting volume

Cell Volume Regulation

• Maintaining constant volume amid osmotic changes is a critical problem for all cells
• Cells respond to swelling or shrinking by activating membrane transport or metabolic processes to restore normal volume
• Extremely sensitive volume-sensing mechanisms detect volume changes as small as 3%
• Volume changes trigger regulatory mechanisms like:
  • Regulatory volume increase (RVI), which creates an osmotic gradient of solute into the cell
  • Regulatory volume decrease (RVD), which creates an osmotic gradient of solutes out of the cell

Homeostatic Processes

• Homeostatic processes encompass:
  • Ionic regulation of specific ion concentrations since most animal cells are polarized
  • Volume regulation: maintaining total water amount in bodily fluid, which is critical because cell volume depends on water levels
  • Osmotic regulation of osmotic pressure in circulatory bodily fluids

Osmotic Strategies

• Animals have different strategies for coping with osmotic stress

Osmoconformers

• Their body fluids and cells match the osmotic pressure of their surroundings
• Usually found in the ocean, where osmolarity averages 1000 mOsm/L
• They do not control extracellular osmotic conditions actively, but can control extracellular osmolytes
• Display high cellular osmotic tolerance
• Cells/tissues cope with high external osmolarities by increasing internal osmolarities using compatible osmolytes to maintaining cell volume.

Osmoregulators

• Maintain homeostatically regulated bodily fluids with different osmotic pressure than their environment
• Maintain constant extracellular osmolarity and ion composition with strict extracellular osmotic homeostasis
• Cells/tissues cannot cope with large changes in external osmolarity

Freshwater Fish

• Strong osmoregulators with steady internal osmotic conditions relative to the external medium
• Fish blood has higher osmolarity
• Absorb large amounts of water via osmosis and lose salts
• Strategy has to include the compensation of ion loss through physiological processes
• Gills contain chloride/ionosites to take up salt and intestines to absorb salts from their food
• Produce large volumes of dilute urine and don't drink water
• Take in salts through gills and gut while producing dilute urine

Marine Bony Fish

• Have much lower osmolarity than freshwater fish
• Marine fish lose water from osmosis and gain salt through passive diffusion
• They are susceptible to dehydration
• Must use osmoregulator strategies for losing salt and gaining water
• Also have salt-excreting chloride cells
• Drink sea water and absorb water from their gut
• Kidneys produce little isotonic urine to save water, with gills playing a more significant role

Marine Invertebrate Osmoconformers

• Utilized by most marine invertebrates
• Energetically cheaper than osmoregulation
• Extracellular fluid (ECF) is like seawater (1000 mOsm), mostly NaCl
• No net osmotic gradient which allows osmoconformers to avoid water loss
• ICF has same osmotic pressure as ECF

Osmolyte Considerations

• Use universal solutes, like K+ (400 mOsm), and organic osmolytes (600 mOsm) with some organic osmolytes stabilizing macromolecules
• Common organic osmolytes are:
  • Carbohydrates
  • Free amino acids
  • Methylamines
  • Urea
  • Methylsulfonium solutes

Solute Classifications

• Based on effects to macromolecules:
  • Perturbing solutes disrupt macromolecular functions: Na+, K+, Cl-, SO4- and charged amino acids
  • Compatible solutes have minimal effect: polyols (glycerol, glucose) and uncharged amino acids
  • Counteracting solutes disrupt function alone but counteract others' effects

Urea as an Osmolyte

• Urea increases tissue osmolarity in cartilaginous fish to prevent water loss
• The perturbing effects of ureas are counteracted by methylamines

Osmoconformer Types

• Stenohaline osmoconformers restricted to narrow salinity ranges and cannot regulate osmolytes
• Euryhaline osmoconformers are tolerant to external salinity changes, successful in intertidal zones, and regulate their organic osmolytes

Nitrogenous Waste Excretion

• Metabolism waste problems include:
  • Production of toxic ammonia, which must be excreted
  • Accumulation may lead to death
  • Soluble ammonia excretion demands lots of water
  • Animals use varied strategies to minimize its effect

N-Waste Strategies

• Most aquatic animals excrete N-waste as ammonia, which is cheap but needs lots of water
• These animals are ammoniotelic
• Excreted ammonia is soluble in water, permeates membranes easily, and is excreted by invertebrates(diffusion out of body), and teleost fish(excreted through the gills).
• Mammals, sharks, and amphibians excrete N-waste as urea or uric acid, which is energetically expensive

Nitrogenous Waste Types

• Uerotelic animals excrete less toxic ammonia, tolerating higher concentrations and saving water

Uricotelic animals

• Adapted to very low water availability, excreting 1000x less soluble and less toxic strategies with most energy cost which includes shelled eggs

Osmoregulation in Terrestrial Animals

• Osmoregulatory organs include external surfaces like gills/skin, gut, salt glands, and kidneys

Salt Glands

• Typically found in sea water animals to ride excess salts in the environment
• Found also in desert animals
• Nasal salt glands secrete hyperosmotic NaCl and involve active NaCl transport

Kidney

• Organ mostly concerned with osmoregulation
• Common architectural design and physiological principles
• The nephron is the functional unit
• Its main function is to produce urine, regulating both water and amount of inroganic solutes
• It removes other metabolic waste alongside Nitrogenous waste
• There is close interaction between the blood and tubules
• The membrane exchange mechanism are also key

Mammalian Kidney

• Possess a pair of kidneys, which is connected though the renal artery which bring blood into the kidney
• Renal veins takes blood out the kidney
• Contains two main structures the Renal cortex, and medulla.
• Renal medulla is composed of renal pyramids

Kidney Structures

• Renal pyramids converge into a renal pelvis, is connected to the ureter
• The nephron is the smallest and main unit of the kidney.
• In human nephrons the proximal tubule, and distal tubule are connected
• Juxtamedullary nephrons: Their long Henley loop travel to the medulla. produce and concentrate hyperosmotic urine
• Cortical nephrons: Their short loop travel to the cortex to reabsorb solutes from urine

Nephron Structures

• The Glomerulus is encapsulated by glomerular capsule, and consists of the renal corpuscle
• Afferent arteriole transports blood to be filtered. The filter blood leaves though the efferent Arteride
• The tubule connects connect the renal corpuscle in the proximal convoluted tubule
• The loop of henle has two limbs, the descending, and ascending
• The peritubular capillaries help concentrate urine and also help sustain gradient in the medulla
• Distal convoluted tubule opens into the collecting duct

Kidney Formation

• Ultrafiltration is when the Glomerulus gets blood though the filtration which then then goes through into tubule. this then creates urine
• Reabsorption is when substances for the body move across the tubular wall into vasa recta
• Secretion it for substances to be removed from the body. Substance move vasca recta in the tubular fluid becoming prime components in urine
• Finally, excretion is urination

Glomerular Function

• First step in the process of turning filtration to urine
• Seperation of plasma fraction, driven but blood hydrostatic pressure
• Filtrate contains water, small solute, waste, protein, and cells

Renal Corpuscle Function:

• Transfers blood to the glomerulus via the afferent arteriole, blood leaves thorough the efferent arteriole

Renal corpuscle Diameters

• Afferent is greater than efferent
• The differences in diameter create hydrostatic pressure in the glomerulus during ultrafiltration

Renal Corpuscle Layers

• Glomerular capillaries are very leaky
• The blood separated by the Bowman capsule has three filtration barrirers
  • First layer of endothelial cells which contain finestra
  • Second, Basment membrane
  • Thirds, a layer of epithelial cells

Glomerular Filtration Forces:

• Favour filtration include blood pressure, opposed by Osmotic pressure, hydrostatic pressure

Glomerular Filtration Rate (GFR)

• About 125 ml per min, 7.5 liters per hour, 180 liters pee day
• The plasma volume is filtered at 45 min, 99% is reabsorbed

Proximal Convoluted Tubule:

• Specializes for transport
• Reabsorption of the most solute and water
• 65–70 filtered sodium chloride, and 65% for water
• Glucose and amino acids

Proximal Convoluted Tubule Secretion:

• Variable proton secretion for acid or base regulation
• All tubular exchanges with the blood are made by a single layer of epithelial cells
• Exchange is either paracellular or transcellular

Loop of Henle

• Possesses an ascending and descending limb

Proximal Convoluted Tubule Changes

• Changes of the tubular fluid differs from ascending and descending limb
• Is creates a osmotic gradient in the medulla as well as reduced osmotic pressure of of the filtrate
• Reabsorbs 20 percent of filter water alongside sodium

Descending Limb:

• Is perable to water but not sodium
• The water moves from the to the intestinal however ions don't
• The filtrate concentrate due to osmosis.

Ascending Limb:

• This Active reabsorbs sodium and chloride
• Is impermeable to water
• Dilutes the ultra filtrates
• Pressure drops from bottom of the limb to distal tubules

Urea in relation with the Kidney"

• The molecule also contributes the gradient and accumulates in the medulla

Distal Convoluted Tubule:

• About 20 percent original volume of total filtered fluid
• Is hypotonic to plasma
• About 75 precent of sodium is reabsorbed
• not commonly permeable to water so water stays in with salts actively moving

ADH

• The collecting ducts functions through concentrating urine
• Is regulated by ADH hormone by dehydration

ADH in the collecting duct:

• Is created in they hypothalamus, and stored in the pituitary
• Increases permeability of water which increases water and absorption in the tubule

Terrestrial invertebrates/excretion

• Nephridia, Protonephridia, Metanephridia, and tubules is the process

protonephridia

• A system where where interstitial fluids turns though

FlatWorms (Osmoregulation)

• Waste from most diffuses out of body

parasitic FlatWorms

• In the isotonic environment, it is the waste is released by its nitrogenous attributes

Netanephridia

• This creates and filters coelomic then Reabsorbs fluids

Malpighian tubule:

• Is in the hindgut and secretes k+, drawing chloride, and water creating urine

Respiration

• Gas exchange between the body, and CO2 that occurs for Aerobic energy requirements
• External respiration requires transportation of oxygen to the internal body from the source

Fick's Law

• Physics of diffusion is calculated though ficks law C and C two are regions though diffusion, area separation
• As organisms get larger and requires multiple steps

Respiratory step:

Ventilation, oxygen diffuses over Epithelia, perfusion and capillary

• Respiratory needs varies on the media type, requirements and needs

Respiratory surfaces is dependent on medium

• Daltons Law is determined in water breathing,
• Fish is Invasions of the body, to increase diffusion

Gills and Oxygen

• Extends to outer with protective cover ,
• Is internally protected by chambers
• Ram ventilation is used in fish to get oxygen

Gas exchange in Air Breather

• A system in air that comes from through the epidermis.
• That moves with open Spiracles. That enters trachea

Lungs

• The lungs do not expand with a series of air sacs with a two cycle of respiration

Advantage of Gas exchange

• Blood moves where with the help of oxygen, is very efficient

Animal breathing

• Lungs in mammals are recycled and have air always
• Refes is the epiglottis, and divide two bronchi that is connected to air sacs

Human lungs:

• Air volumes are at its high, and are divided
• Boyles law helps in explaining the lungs function through press
• tidal is a single breaths, and residual is lungs in their end
• Oxygen is absorbed then passes from high to low to have oxygen diffuse

Regulation of Lungs:

• Senses in body through central types. The controller are pons
• O2 is transported with hemoglobin, carries with plasma

Transport In Blood

• 98 in blood stream of red blood cells with, to transport
• Its why hemoglobin is important

Oxygen

• Is needed to transport in tissue for diffusion
• Hemoglobin-Oxygen dissociation curve •The sigmoid shape results from cooperativity •Binding of O2 in one site increases the affinity of the other sites for O2

Alveoli

• Large qualities when diffused maintain pressure
• Hemoglobin's effect on the blood depends in the temperature
• The effect helps with oxygen in tissues

Cardiovascular System

• The amount of heart rate per time is a high
• Cardiac is 7ml beat, pumps in each, and has a lot of regulation
• The regulation is autonomic
• Blood has two fraction, liquids plasma. Those functions has plasma to move lipid volume with hemotocit

Capillaries

• The arteries, and arterioles are smaller than the blood diameter
• A velocity is made with muscle pump, and has vaves to help
• Wall in the area are single all to help

All animal requirements

• Eliminate waste, adequate nutrition, and thickness

Simple Circulation

• Diffusion system to bring and waste
• Internal fluid brings medium transports molecule. Invertebraes has a hard, heart

Functions of insect hemolymph

Hemolymph:

• A fluid analogous to the blood in vertebrates

Most circulatory in system has basic elements, like heart

• Invertebrates has this better system
• Heart is better with blood at a high price, and delivery and has tissue faster

Evolution of Animal

• Is a single loop, high bp has single atria
• Birds/mammals had artim that is divided which is a closed circuit that has 2 loops to provide O that is very metabolically active

More Evolution

The Mammalian has 4 is for pumping, to contract and has a cycle for blood flow. NErviogenic hearts are needed for brain