Osmoregulation and Fluid Compartments

Osmoregulation

• Osmoregulation maintains water and salt balance in the animal body through selective retention and secretion.
• Necessary for maintaining the intracellular aqueous environment's function and the effect of ion concentration on protein function.
• Optimal protein function occurs within a narrow range of inorganic ion concentration.

Fluid Compartments

• Intracellular fluids (ICF) exist inside animal cells.
• Extracellular fluids (ECF) exist outside animal cells and include interstitial fluid and blood plasma.
• Each fluid contains different ions, electrolytes, and organic compounds, accounting for over half of an animal's body weight.
• Most animals regulate water in blood for osmoregulation, but it can also occur in interstitial fluid.
• Regulating ECF spares individual cells from disruptions and allows cells to exist in a more stable chemical environment.
• ATP is used by most cells to regulate intracellular ion composition.
• Most cells are water-permeable, maintaining ionic differences across their membranes without osmotic differences.

Transport

• Transcellular transport involves the movement of substances through cells across membranes.
• Paracellular transport involves the movement of substances between cells in "leaky" or "tight" epithelia.
• Transporters include: Na-K+ATPase, Ca2+-ATPase, Ion channels, Electroneutral cotransporters, and Electroneutral exchangers.
• Water moves from low to high solute concentration, driven by an osmotic gradient based on differences across the cell membrane.
• Water cannot be actively pumped.

Osmolarity

• Osmolarity measures solute concentration.
• 1 mole of glucose equals 1 osmol, and 1 mole of NaCl equals 2 osmols.
• Changes in osmolarity create transmembrane osmotic gradients, affecting cell volume.
• Water movement can cause cells to swell or shrink.

Volume Regulation

• Cell volume regulation maintains constant volume despite osmotic changes.
• Cells respond to swelling or shrinking by activating membrane transport or metabolic processes.
• Volume sensing mechanisms are sensitive and respond to changes as small as 3%.
• Volume regulatory mechanisms include:
  • Regulatory volume increase (RVI), creating an osmotic gradient of solute into the cell.
  • Regulatory volume decrease (RVD), creating an osmotic gradient of solute extrusion from the cell.

Homeostatic Processes

• Three homeostatic processes include:
  • Ionic regulation, concerning concentrations of specific ions important for cell polarization.
  • Volume regulation, maintaining total water amount where cell volume is regulated.
  • Osmotic regulation, controlling the osmotic pressure of circulatory bodily fluids.

Animal Adaptations

• Osmoconformers: Their body fluids and cells are equal to the environment's osmotic pressure.

  • Typically found in oceans, do not control extracellular conditions, and have high cellular osmotic tolerance.

• Osmoregulators: Homeostatically regulate bodily fluids, differing from the external environment.

  • Maintain constant extracellular osmolarity and ion composition, unable to cope with large-scale changes.

Osmoregulation and Excretion

• Freshwater fish: These are strong osmoregulators whose internal osmotic condition stays steady relative to the external environment.

  • Blood has higher osmolarity, causing water absorption via osmosis and salt loss.

• Marine bony fish: These have much lower osmolarity than freshwater fish.

  • Marine fish lose water and gain salt through osmosis and passive diffusion.
  • Osmoregulation involves excreting salt and gaining water through the chloride cell, drinking seawater, and producing isotonic urine.

• Marine invertebrates: This is the most common strategy and is energetically less expensive than osmoregulation.

  • ECF is similar to seawater (1000 mOsm), dominated by NaCl, and ICF has the same osmotic pressure as ECF and has universal/organic solutes.

Solutes

• Solutes' effects on macromolecules distinguish their classification.
  • Perturbing solutes disrupt macromolecular function.
  • Compatible solutes have little effect.
  • Counteracting solutes disrupt functions but can counteract effects when combined.

Urea

• Cartilaginous fish use urea to increase tissue osmolarity, preventing water loss.
• Methylamines counteract urea's perturbing effects.

Osmoconformers

• Stenohaline osmoconformers have restricted salinity ranges and cannot regulate osmolytes.
• Euryhaline osmoconformers tolerate salinity changes, are successful in intertidal zones, and regulate organic osmolytes.

Nitrogenous Waste

• Nitrogen metabolism yields toxic ammonia, requiring excretion strategies.
• Ammonia excretion, used by aquatic species (ammoniotelic).
  • It's energetically cheap but needs lots of water which is highly soluble and easily permeates membranes.
• Urea and uric acid excretion by mammals, sharks, and amphibians.
  • It's energetically expensive but requires minimal water for being less toxic.

Waste Excretion

• Uerotelic animals excrete less-toxic urea.
• Uricotelic animals excrete insoluble, least-toxic uric acid, suiting shelled eggs.

Terrestrial Osmoregulation

• Osmoregulatory organs include external surfaces, the gut, specialized kidneys, and salt glands.

Salt Glands

• These are in elasmobranchs, birds, and reptiles that live in seawater or deserts.
• Nasal salt glands secrete hyperosmotic NaCl with active NaCl transport.

Kidney Function

• The kidney regulates water, inorganic solute levels, and removes waste.
• The nephron has tubules for collecting areas, the proximal/distal tubule, a storage bladder, and has a final duct.

Kidney Structure

• A pair of kidneys connects to the renal artery/vein.
• The renal medulla has renal pyramids.

Nephron Parts

• The renal pelvis connects the ureter, and the nephron is its smallest functional unit.
• In humans, the proximal/distal tubules connect with the loop of Henle.
• Juxtamedullary nephrons have a long loop of Henle/produce concentrated urine.
• Cortical nephrons have a short loop of Henle/reabsorb in the cortex.

Vascular Elements

• Components constitute the renal corpuscle.
• The afferent arteriole brings blood in for filtering, and the efferent arteriole takes it out.
• The proximal convoluted tubule connects to the renal corpuscle.
• The loop of Henle has descending/ascending limbs.
• Peritubular capillaries concentrate the urine/maintain the osmotic gradient.
• The distal convoluted tubule connects to the collecting duct. The kidneys' physiology includes ultrafiltration, reabsorption, and secretion.

Ultrafiltration

• The blood undergoes filtration in the glomerulus of the ultrafiltration process.
• This is where blood is filtered into the tubule to make urine.

Reabsorption & Secretion

• Needed substances are absorbed or reabsorbed with substances moving into the vasa recta.
• To be eliminated, substances are secreted/transfer from the vasa vera to the tubular fluid.

Excretion

• Excretion= filtration - reabsorption + secretion.
• Glomerular filtration is the first step.
• It separates the plasma with waste products, useful molecules and small plasma solutes/water from blood, with no/low protein content.
• Blood hydrostatic pressure drives the process.

Corpuscle

• Blood flows into the corpuscle via afferent/efferent arterioles with a large diameter difference for hydrostatic ultrafiltration.

Transport Barriers

• Three barriers separate blood from the Bowman's capsule.
  • Fenestra exist in the endothelial cells.
  • A basement membrane exists.
  • A layer called podocytes with foot processes form the filtration surface.
• Filtration is favored by capillary blood pressure and opposed with plasma-colloid osmotic/Bowman's capsule hydrostatic pressure with a net pressure.

Filtration Rate

• Glomerular filtration rate is ~125 mL/min or 180 liters/day.
• With 99% of plasma reabsorbed and is filtrated every 45 mins.

Tubule Features

• Proximal convoluted tubule is specialized for transport/reabsorption of much solute and water, plus filtered fluids and aminos
• A Single layer exchange with blood through renal epithelium is transcellular or paracellular in the Loop of Henle
• The descending limb's changes are different than the ascending limb, which helps establish the gradient.

Limb Characteristics

• The descending limb is permeable/reabsorbs filtered water into the medulla, increasing filtrate concentration via osmosis. The ascending limb is impermeable for concentrating the interstitial/diluting the ultrafiltrate with active reabsorption
• As water is reabsorbed and salts exit, the filtrate becomes more dilute.
• Urea moves throughout the gradient and builds up with salt and water.

Distal Tubule Characteristics

• Volume is 20% or less of the original filter, hypotonic
• Sodium is reabsorbed along the distal tubule

Collecting Duct

• Main function is exploiting the osmotic pressure/permeability via hormones and H20 absorptions to the tubules
• ADH is secreted in the pituitary and activated when dehydrated

Terrestrial Inverts

• Osmoregulation and excretion occur through nephridia.
  • This primitive "kidney" is found in flatworms/mollusks.
  • Excretory tubules are found in insects.

Excretory Types

• Protonephridia excretes through fluid flow
• Fresh water flatworms are mainly osmoregulate, and parasitic worms are mainly excretory.
• The Metanephridia tubules can filters, absorbs. and reabsorb.
• Hindgut releases K+ and absorbs H20

The need for O2 constant

• O2 is the electron acceptor, without it bodies yield in aerobic respiration and most animals won't survive it

Transport/Composition

• Organisms transpire internally and externally.
• Diffusion is defined by fick's law- as organisms are larger, surface area will become smaller, but oxygen use increases
• Respiration will require the need for ventilation, diffusion, perfussion, and capillary use
• Physical components need to be considered with daltons law

Gills

• Gills can either be external or internal
• Internal Gills will use water flow and ram ventilation
• The filaments flow with water in a countercurrent fashion.

Air and Fluid

• Tracheal system uses air in windpipes.
• Birds circulate air sacs in a 2 cycle system
• Mammals use a chest cavity for breathing and mixing of air in the lungs

Ventilating air

• Ventilating is according to boyle's law and the air molecules are compressed
• Inhalation will be active and the lungs use Diaphragm and external intercostal to change pressure/ribcage.
• exhalation is the reverse: (passive)residence muscle go back, then active using abdominals.
• Total lung compacity varies

Ventilation regulation

• Ventilation is regulated with detection of PH, 02, stretch. Then through the control center being effected by respiratory muscles.
• Peripheral bodies detect ph/C02/02 and inform the medulla for respiration
• 02 is transported with hemolysis, >98%
• if the bodies have low 02 in fluids, the bodies require to much 02.

Hemoglobin

• Hemoglobin combines through blood with 1.39 ml O2 therefore can transport 21.1.5+
• Partial 02 is higher with air, leading blood to enter RBSC

Iron/Oxygen

• Oxygen is bounded with hemoglobins that bind 4 oxygen molecules with ferrous (Fe2+) ion

Oxygen binding

• Binding increase when binding to 02- leading maintain a large partial pressure and release 02 when the affinity is low.
• A lower PH reduces hemoglobin

Diffusion/Concentration

• Oxygen enters the tissues and exits the body in with fluids from plasma for C02
• Carbonic anhydrase Catalyzes the rapid interconversion to ensure blood and tissue

Blood

• C02 travels from cells to RBS by first combining hemoglobin

Circulation Types

• The system is mammilian which has a variable heart rate and is autonomic and is controlled with sensoring blood/pressure .
• Blood includes plasma that composes of protein.
• Two vessel are the Arteries that deliver to artioles, from veins that derive.
• Lumen gets thicher with blood volume through collagen and vascuolity- creating pressure

Vasculature

• Blood flows to valves (unidirectional)
• Blood flows down into cross sections before slowly moving/exchange

Complex System

• The system requires a "Skin" to protect and carry nutrience
• it flows with water and can be open (low 02) ot slosed (fast 02 delivery) or in a double circuit.

Inverts

• They uses fluid-Analagous blood and can can contain hemolymph
• Vertebrae can pump with a 2 atrium or 1/2 ventricles.
• Birds and mammals use 2/2

Heart Action

• Valves pumps from top to side/lungs.
• Rhythm occur/relax through nerugenic actions with high speed

Heart Rhythm

• The heart is coordinated
• It can be influenced with action potential and the signal start with S/A/V nodes- and the cardiac cells will reach it at some point.

Nutrition

• Nutrience are what bodies use for energy
• Animals break down these product/are absorbed from the bodies.

Nutrition phases

• Phase with an intake
• Break down with absorbtion until excretion.

Requirements

• Body needs inorganic/organic materials and macro/Micro nutrients.
• Hydrolysis breaks chemicals and converts into ATP
• 20 vs carbs/protein/fat
• Energy is calroies

building phases

• AmInos fatty molecules / acid need to synthesized
• Vits are needed because the bodies cant take them without

Molecules

• Soluble vitamins are water in and out, and insoluble are stored in the fat.
• Carbohyd are main and can be combined, same with proteins/lipids

Animals feeding

• Animal feed with fluid. Solids, susupned particles, or large sections.
• Bodies take place withextra/Intracellular.

Digestion tracts

• Bodies digest through a caviruty and 2 sides
• Intersintes are a sequence of muscle/chemical breakdown

Intestine layers

• The intestines has a layer of muscle on the mucosa- for protection and abrosbtion
• Mucas regulates, bacteria lives in intestines
• Digestion occurs through cell types like microvilli

Metabolism Processes

• The bodies goes Through Absorptove Vs Post
• Stored in glycogen then into ATP

Metabolite Regulation

• Can be stimulated with Insulin and glycogenisis reduced
• The rate/nutrience will influnce appetite

Body Temp

• The bodies runs on a range with metobilzing/radiation
• temp depends on body compacity and if it needs to create more with heat

Endocrine Systems

• Endocrine System Uses horommes that regulate with negative/positive feedback- with cellular reaction

Hydrophilic Horomones

• Horomones that affect proteins and act on phosphate

Hydrophobic Horomones

• Affect protein and act on internal receptors

Hypothalumus

• Hypo releases/Inhibits/ peptides

Glands

• Anterior controls endocreine- Thryoid/ adrencotopric and procreation. Posterior is the opposite, urine
• The Endocrine glans is in the from throat