10. Osmoregulation, Endocrine System And Neuron Function Flashcards
What is osmoregulation?
The process of maintaining salt and water balance (osmotic balance) across membranes within the body.
It includes the removal of metabolic wastes and the maintenance of the interstitial fluid.
What is excretion?
The disposable of nitrogen-containing metabolites and other waste products.
What are metabolites?
Small molecules that participate in general metabolic reactions and are required for the maintenance, growth and normal function of cells.
What is ammonia?
A toxic metabolite produced as a waste product of cellular metabolism.
Formed from nitrogenous molecules.
What are the plasma membrane’s outer and inner surfaces in contact with?
The outer surface is in contact with the external environment or interstitial fluid.
The inner surface is in contact with the cell’s cytoplasm.
What forms of transport are osmosis and diffusion?
Passive transport.
What is diffusion?
The passive net movement of molecules or particles from an area of higher concentration to an area of lower concentration, resulting in the equalisation of concentration.
A spontaneous process.
What is osmosis?
A specific type of diffusion where solvent molecules (usually water) move from an area of lower solute concentration to higher solute concentration through a semipermeable membrane.
What occurs if an animal cell is in an isotonic solution?
The cell and it’s surrounds are in equilibrium, and the cell is normal.
What is an isotonic solution?
A solution where the solutes inside the solution and the solutes outside the solution are equal.
There is no net movement as equilibrium is reached.
What occurs if an animal cell is in an hypertonic solution?
Water will diffuse out of the cell and the cell will shrivel.
What is a hypertonic solution?
A solution that has a higher solute concentration that it’s surrounds.
Solvents will diffuse into this solution, out of any cell or substance they were contained in.
What occurs if an animal cell is in an hypotonic solution?
Water will diffuse into the cell, causing the cell to lyses (burst).
What is a hypotonic solution?
A solution with a lower solute concentration than its surrounds.
Solvents will diffuse out of this solution in an attempt to reach equilibrium.
What is osmolarity?
The number of particles per litres of solution, expressed as mOsm/L.
(milli Osmoles per litre)
What are osmoconformers?
Organisms that match their internal osmolarity to that of their environment, preventing water loss.
E.g. marine invertebrates.
What are osmoregulators?
Organisms that actively control their internal osmolarity regardless of the external conditions.
E.g. all fish
What is the average osmolarity of saltwater?
Around 1,000 mOsm/L
What is the average osmolarity of freshwater?
< 1 mOsm/L
How does a marine fish act as a osmoregulator?
Marine fish have an internal osmotic concentration lower than the surrounding seawater, so they tend to lose water and gain salt.
They actively excrete salt from the gills and take on water to maintain homeostasis.
How does a freshwater fish act as a osmoregulator?
Freshwater fish have an internal osmotic concentration higher than the surrounding freshwater, so they tend to gain water and lose salts.
They actively excrete water in dilute urine and take up salt via their gills to maintain homeostasis.
What does the osmoregulation of terrestrial animals focus on?
Water preservation to prevent dehydration.
What are 4 ways through which water is lost from an animal’s body?
- Urine.
- Faeces.
- Skin.
- Respiratory organs.
What are 2 ways animals counteract water loss?
- Drinking water and eating moist foods.
- Producing water as a by-product of cellular respiration.
How do the kidneys osmoregulate?
They filter blood to remove excess solutes and waste products as excreted urine.
What is active transport?
A form of transport across a cellular membrane that requires energy (usually ATP) to move against the concentration gradient.
What type of transport do osmoregulators use to maintain their osmotic gradient and solute concentrations?
Active transport.
What is transport epithelia?
One or more layers of epithelial cells specialised for moving particular solutes in controlled amounts in specific directions.
They are typically arranged into tubular networks with extensive surface areas.
Where are transport epithelia in the body?
- Facing the external environment directly.
- Forming linings on channels connected to the external environment through an opening on the body surface.
How can sea birds remove excess salt from their bodies?
They can excreted concentrated salt via transport epithelium.
What is the supraorbital gland?
A salt excreting gland found in some marine birds.
Also known as the salt gland.
E.g. located in the nostrils of pelicans.
What are the 3 forms ammonia is processed into for removal from the animal body?
- Ammonia.
- Urea.
- Uric acid.
What are the details of animal ammonia disposal?
- Requires lots of water to dilute because of toxicity.
- Doesn’t require much energy since it isn’t converted into anything else.
- Mostly directly disposed of by aquatic animals.
What are the details of animal urea disposal?
- Requires some water for excretion due to being somewhat toxic. Highly soluble.
- Requires some energy due to ammonia conversion.
- Mostly disposed of as urea by land-based animals.
What are the details of animal uric acid disposal?
- Water-saving paste. Not toxic.
- Energy expensive due to conversion from ammonia to urea to uric acid.
- Mostly disposed of as uric acid by birds, reptiles, insects, and snails.
What is the white component of bird droppings?
Uric acid.
What is the nitrogenous waste excretion of amphibians?
- Ammonia excretion as tadpoles in an aqueous environment.
- Urea excretion when land based.
What are the 4 main steps of the excretory system?
- Filtration.
- Reabsorption.
- Secretion.
- Excretion.
What drives filtration through the transport epithelium?
Hydrostatic pressure.
(Blood pressure in the circulatory system)
The diverse excretory systems of animals are all very…?
Tubular.
What occurs during the start of the excretory process?
A body fluid (blood, haemolymph, or coelomic fluid) comes into contact with a selectively permeable membrane of transport epithelium.
What is nitrogenous waste excreted as?
Urine.
What is the filtration step (in an excretory system)?
Water and small molecules like salts, sugars, amino acids, and nitrogenous waste cross the transport epithelium, forming a filtrate that flows into an excretory tube.
What is the reabsorption step (in an excretory system)?
Selective reabsorption recovers useful molecules via active transport (after filtration) and returns them to the body fluid.
What is the secretion step (in an excretory system)?
Occurring after reabsorption.
Any additional unwanted substances still in the body are secreted into the excretory tubule.
What is the excretion step (in an excretory system)?
Water is either added or removed by osmosis before the waste fluid is excreted from the body as urine.
What is a protonephridia?
The basic excretory system of flatworms (planaria).
What is the structure of a protonephridia?
A set of tubules ending in filtering units called flame cells.
The cilia of flame cells propel waste through tubules into branched structures that lead to pores all along the sides of the body. The filtration is excreted through these pores
What is a metanephridium?
The excretory system of annelids (e.g. earthworms).
Flatworms (planaria) lack what embryotic structure?
A body cavity or coelom.
What is the structure/function of a metanephridium?
- Ciliated nephridia filter fluid from the coelom (or body cavity) into tubules.
- Nutrients and other solutes are reabsorbed by capillaries as the filtration passes down the tubules.
- Filtered fluid is stored in a bladder then secreted through a pore in the side of the body.
What are malpighian tubules?
Excretory osmoregulatory organs found in insects and arthropods.
Where in the body are malpighian tubules found?
Immersed in haemolymph.
What is the structure/function of malpighian tubule excretory systems?
- Sodium or potassium ions are actively transported into the lumen of the tubules.
- Water enters the tubules via osmosis, forming urine.
- The urine passes through the intestine and into the rectum, where nutrients are reabsorbed by the haemolymph.
- Sodium or potassium ions are pumped into the haemolymph, and water follows.
- The concentrated waste is excreted.
What animals have a kidney?
Mammals, vertebrates, and some chordates.
What are the 4 structures of the human urinary system?
- Kidneys.
- Ureter.
- Bladder.
- Urethra.
What is the basic (excretory) function of the kidneys?
To produce urine.
What is the basic (excretory) function of the ureter?
To transport urine from the kidney to the bladder.
What is the basic (excretory) function of the bladder?
To store urine.
What is the basic (excretory) function of the urethra?
To conduct urine into the environment.
What are the differences between the male and female urinary systems?
The only difference is the length of the urethra.
Shorter in females, longer in males
What are 2 additional functions of the kidney, outside of waste excretion?
- Blood volume, pressure, and pH regulation.
- Regulation of important electrolytes and metabolites.
What percentage of human urine is water?
90-95%
What is the principle organ of the urinary system?
The kidneys.
Solid waste from the blood eventually leaves the body as…?
Urine.
What are the 4 steps of the human excretory system (organs)?
- The renal arteries and vein circulate blood to 2 kidneys.
- Urine produced by the kidney exists via the duct called the ureter.
- The ureter drains into the urinary bladder.
- The urine is excreted via the urethra.
What is the outer layer of the kidney?
The Renal cortex.
What is the inner layer of the kidney?
The Renal medulla.
What is the Renal pelvis?
A hollow opening in the kidney where all the nephrons enter into to get rid of their urine.
Connected to the ureter.
What does blood enter the kidney through?
The Renal artery.
What does blood leave the kidney through?
The Renal vein.
What percentage of cardiac output is filtered by the kidneys?
20%
What is a nephron?
The functional unit of the kidney.
There are about 1 million nephrons in a human kidney
What is the glomerulus?
A long tubule with a ball of capillaries.
Part of the nephron.
What is the Bowman’s Capsule?
A cup shaped swelling that surrounds the glomerulus.
Where are the glomerulus and convoluted tubules located?
The kidney cortex.
Where are the collecting ducts located?
The pyramids of the Renal medulla.
What is the order of tubules that filtrate passes through?
- From blood into glomerulus.
- Bowman’s Capsule.
- Proximal Tubule.
- Loop of Henle.
- Distal Tubule.
- Recieved by collecting duct and transported to the Renal pelvis.
What is the circulatory pathway of the kidney?
- Blood enters the nephron through the afferent arterioles.
- Enters the glomerulus before reaching ‘dead end’ in Bowman’s Capsule.
- Filtration occurs in Bowman’s Capsule.
- Blood goes through the efferent arterioles and through the peritubular capillaries, where secretion and reabsoprtion occur.
What is the Renal corpuscle?
The blood-filtering part of a nephron, consisting of the glomerulus and Bowman’s Capsule.
What is the first Renal tubule?
The proximal convoluted tubule.
What occurs in the proximal convoluted tubules?
Reabsorption of solutes and water into the circulatory system.
What occurs in the distal convoluted tubules?
Both secretion and absorption.
What occurs in the Loop of Henle?
- Water is reabsorbed in the descending loop of Henle.
- Salts are reabsorbed in the *ascending** loop of Henle.
What occurs in the medulla that impacts the loop of Henle?
Increased salt levels set up a countercurrent exchange.