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Chapters 44-45 - Coggle Diagram
Chapters 44-45
Osmoregulation and Excretion
Osmoregulation
How animals control solute concentrations and balance water gain + loss
Driving force is a concentration gradient of solutes across the membrane
Unit of measurement is osmolarity
The number of moles of solute per liter of solution
Human blood is about 300 milliosmoles per liter
Isoosmotic - Two solutions with equal osmolarity
No net movement
When two solutions have different osmolarity...
Hyperosmotic - The solution with higher solute
Hypoosmotic - The solution with lower solute
Adaptations
Osmoconformer
Isoosmotic with its surroundings
All are marine animals
Hypoosmotic to the seawater
Bony fishes
Drink lots of seawater
Excess salts are eliminated through the gills and kidneys
Hypoosmotic to the seawater (salt)
Cartilage fishes
Tissues have a higher concentration of OTHER solutes
Water flows in through osmosis and in food (no drinking)
1 more item...
No big challenges
Actively transport specific solutes that they maintain at different levels than the ocean
Ex. Atlantic lobster maintains Mg ion concentration at less than 9 mM; their environment's is 50 mM
Osmoregulator
Internal osmolarity is controlled and independent of the external environment
Body fluids of freshwater animals must be hyperosmotic
Freshwater animals can can excrete large amounts of very dilute urine and drinking little water
Lost salts are replenished through food and gills
Prone to drying out
Land animals
Exoskeletons
Keratinized skin cells
Desert animals minimize water loss to begin with
Waxy cuticles on land plants
Most animals are stenohaline; can't tolerate osmotic changes in environment
Euryhaline animals can withstand osmotic fluctuations
Euryhaline osmoconformers: Barnacles, mussels
Euryhaline osmoregulators: Striped bass, salmon
Salmon osmoregulate like freshwater fish, and then acclimatize for sea water
Acclimatize by producing cortisol; increases size of specialized salt secreting cells
Aquatic invertebrates can survive desiccation by anhydrobiosis
"life without water"; a dormant state they enter when their habitats dry up
Ex. Tardigrades
Anhydrobiosis requires adaptations that keep cell membranes intact
Desiccated nematodes have lots of sugars; disaccharide called trehalose protects cells
Energetics
Osmoregulation requires energy because of active transport
Depends on how different the animal's osmolarity is compared to the environment, how easily water and solutes can move across the surface, and how much work is required to pump across the membrane
Energy cost minimized by body fluids that differ less from the external environment
Indirect osmoregulation by managing solute concentration of body fluids
Done by organs like the kidneys
Or done by individual cells
Transport epithelia
Specialized for moving particular solutes in controlled amounts in specific directions
Arranged into tubular networks
Types of excretory systems
Excretion - Process of eliminating nitrogenous wastes from the body
Key steps of excretory system function
Excretory processes begin when body fluids come into contact with transport epithelium
Filtration: Water and solutes (filtrate) are forced into excretory tubules by blood/hydrostatic pressure
(Selective) Reabsorption: Valuable substances in filtrate are recovered and returned to the body fluid
(Selective) Secretion: Other substances in the body fluid can be added to the filtrate by active transport
Excretion: Processed filtrate is released as urine
Ammonia - Toxic metabolite from the break down of proteins and nucleic acids
Most aquatic animals excrete directly
This requires more water
Mammals, most amphibians, sharks, and some bony fish excrete as urea
Ammonia is combined with carbon dioxide in the liver
Low toxicity, high water solubility
High energy cost
Birds, reptiles, insects, land snails excrete uric acid
Nontoxic, does not readily dissolve in water
Semi solid paste
Requires even more energy than urea
Must be transported through and excreted only in large volumes of dilute solution
Type/amount of nitrogenous waste match environment
Abundance of water = ammonia or urea
Dry areas = uric acid
Endotherms can produce more nitrogenous waste than ectotherms
High protein diet = more nitrogenous waste
Protnephridia
Excretory system in flatworms, rotifers, some annelids, mollusc larvae, and lancelets
Beating cilia draws in interstitial fluid through the flame bulb
Fluid is filtered and filtrate enters the tubule
Processed filtrate empties as urine via open tubules
Dead-end tubules that branch throughout the body with flame bulb caps
Metanephridia
Most annelids; a pair in each segment
Collect fluid directly from coelom
Produce urine that is dilute
Both excretory and osmoregulatory
Malpighian tubules
Remove nitrogenous wastes and osmoregulate
Extend from dead-end tips immersed in hemolymph to openings into the digestive tract
No filtration; transport epithelium secretes solutes from the hemolymph into the tubule lumen
Produce uric acid
Insects + terrestrial arthropods
Kidneys
Compact organs consisting of tubules for both excretion and osmoregulation
Vertebrates + some other chordates
Usually nonsegmented except in hagfish
In vertebrates, includes other ducts and structures that carry urine out of the body
The nephron
Filtrate forms when fluid passes from the bloodstream to the lumen of the Bowman's capsule
Glomerular capillaries and specialized cells retain blood cells and large molecules but are permeable to small molecules
So, the filtrate contains small molecules
Proximal tubule: Reabsorbs ions, water, and other nutrients. Materials for excretion become concentrated
Loop of Henle: Filtrate leaves the proximal tubule and descends into the loop of Henle, further reduces filtrate volume. Lots of aquaporins for water to leave the tubule
Ascending loop of Henle: Filtrate returns to the cortex. No aquaporins. NaCl diffuses out (thin segment) and is actively transported into the interstitial fluid (thick segment). Filtrate becomes dilute
Recovery of salt
Distal tubule: K+ secreted into the filtrate and NaCl reabsorbed form the filtrate
Collecting duct: Processes filtrate into urine and is carried to the renal pelvis
Recovery of water
Produce an osmolarity gradient that allows water to be extracted from filtrate
Juxtamedullary nephrons
Maintain osmolarity gradient in tissues surrounding the loop of Henle
Allow shedding of salts and nitrogenous wastes without wasting water
Mammals that excrete the most hyperosmotic urine have many + very deep loops of Henle
Aquatic mammals have mostly cortical nephrons and intermediate loops
Countercurrent multiplier systems - expend energy to create concentration gradients
Vampire bats can drink too much blood, so the kidneys begin to excrete large amounts of dilute urine while they feed
Because they consume so much protein but don't have enough water to drink for dilution, their kidneys produce smaller quantities of highly concentrated urine
Birds have juxtamedullary nephrons for dry environments, and have shallower loops
Conserve water by excreting uric acid
Reptiles have cortical nephrons and produce isoosmotic or hypoosmotic urine
Cloaca absorb water
Uric acid
Freshwater fish produce large volumes of very dilute urine; cortical nephrons
Similar to amphibians
Bony fish have fewer and smaller nephrons in comparison
Low filtration rates
Osmoregulation relies on specialized chloride cells
Hormonal regulation
Antidiuretic hormone (ADH)
Increased release triggered when blood osmolarity is high
After eating salty food, or water loss like sweating
Osmoreceptors in the hypothalamus detect this + release ADH from posterior pituitary
Increase in water absorption reduces urine volume
Release is reduced when blood osmolarity is low
Such as after drinking too much water
Decrease in permeability of collecting ducts reduces water absorption = large volumes of dilute urine
Alcohol inhibits ADH release = excessive urinary water loss and dehydration
Mutations that interfere block additional aquaporin channels and result in severe dehydration + solute imbalance
ADH molecules bind to and activate membrane receptors on the surface of collecting ducts
Renin-angiotensin-aldosterone system (RAAS)
Responds to drop in blood volume and pressure by increasing water and Na+ absorption
Involves the juxtaglomerular apparatus: specialized tissue that supplies blood to the glomerulus
When blood pressure or volume drop in afferent arteriole, JGA releases renin
Renin cleaves plasma protein angiotensinogen, yielding angiotensin II which triggers vasoconstriction
Stimulates release of aldosterone: causes distal tubules and collecting ducts to reabsorb more Na+ and water
Atrial natriuretic peptide inhibits release of renin if blood volume/pressure need to be lowered
Hormones and the Endocrine system
Types of hormones + how they work
Protein based
Polypeptides
Water soluble
The most common
Protein fragments
Amines
Water soluble
Modified amino acids
Can't permeate cell membranes; must bind to specific receptors to communicate
Binding breaks off a G protein inside cell
G protein binds to enzyme to start a process
Steroids
Nonpolar
Small lipid based hormones that can permeate cell membranes
Directly interact with cell's DNA
Hormone effects
Hormone deficiency or overload
Down-regulation
Too much hormone
Less receptors available when a hormone is overused
Up-regulation
Too little hormone
Increase in receptors for a hormone that is scarce
Stimulation
Hormone increases or triggers metabolic activity
Inhibition
Hormone slows or stops metabolic activity
Agonists
Hormone increases the effect of another hormone
Positive feedback
Ex. Prolactin and oxytocin
Antagonists
Hormone cancels out the effect of another hormone
Negative feedback
Ex. Insulin and glucagon, calcitonin and parathyroid hormone
Neuroendocrine pathway
Hypothalamus, pituitary, glands throughout the body
Endocrine glands
Pituitary
Anterior
Thyroid stimulating hormone
Stimulates the thyroid
Adrenocorticotropic hormone
Stimulates the adrenal gland cortex
Follicle stimulating hormone
Stimulates sperm + egg maturation
Luteinizing hormone
Triggers release of estrogen and testosterone
Prolactin
Triggers release of milk
Melanocyte stimulating hormone
Determines color of melanocytes
Growth hormone
Stimulates mitosis
In sphenoid bone behind the nasal cavity, below the hypothalamus
Posterior
Antidiuretic hormone
Regulates water reabsorption
Oxytocin
Triggers milk production and labor contractions
Hormones released by the posterior pituitary are produced in the hypothalamus
Thymus
Middle of chest
Thymosin
Stimulates variation during production of T cells
Parathyroid
Parathyroid hormone
Breaks down bones to increase blood calcium
Behind the thyroid
Gonads
Ovaries
Pelvis
Estrogen
Triggers puberty in females and stimulates follicle
Progesterone
Prevents shedding of the uterine lining
Testes
Scrotom
Testosterone
Triggers puberty in males and development of sperm
Pineal
Epithalamus
Melatonin
Makes you sleepy; regulates circadian rhythm
Thyroid
Thyroid hormone
Regulates metabolic rate
Calcitonin
Takes calcium from the blood to deposit in bones
Front of larynx, top of trachea
Adrenal
Cortex
Mineralocorticoids
Regulate minerals like sodium and potassium ions
Glucocorticoids
Turns fats into sugars for cells
Gonadocorticoids
act like estrogen and testosterone
Outer layer
Medulla
Epinephrine
Triggers fight or flight
Norepinephrine
Triggers fight or flight
Inner layer
Sit on top of the kidneys
Pancreas
Underneath the stomach
Insulin
Triggers cells to take in sugar from the bloodstream
Glucagon
Triggers release of sugar from glycogen stores in the liver