Chap 44-45 - Osmoregulation & Endocrine Flashcards
Osmolarity
Moles of solute per litre of solution.
(mOsm/L)
Hypo-, iso- & hyperosmotic
vs
Hypo-, iso- & hypertonic
-osmotic refers to the osmolarity.
-tonic refers to the cell’s response in solutions.
Osmoconformer
Organism that is isoosmotic with surroundings - seen in many marine animals.
Stenohaline
Organisms that can’t tolerate large changes in external osmolarity. Osmoregulators can be stenohaline.
Euryhaline
Organisms that can survive large fluctuations in external osmolarity.
Eg. barnacles in estuaries.
Anhydrobiosis
Dormant, desiccated state.
Eg. in tardigrades
Typical osmolarity of seawater
1,000 mOsm/L
or 1,00 mOsmol/kg
Typical osmolarity of freshwater
0.5-15 mOsm/L or mOsmol/kg
Source of nitrogenous waste in animals
Breaking down of molecules that contain amino groups (NH2). Specifically amino acids and nucleic acids.
Forms of nitrogenous waste in animals
Straight ammonia NH3 - fish, aquatic animals.
Urea - mammals, amphibians, some fish.
Uric acid - reptiles, birds, arthropods & terrestrial molluscs.
Ammonia as nitrogenous waste
Highly toxic since it easily converts to Ammonium (NH4+) that interferes with respiration.
Easily diffuses out of cells/highly soluble.
(Aquatic animals)
Urea as nitrogenous waste
Less toxic than NH3 but requires energy to assemble. Conserves water with an energy cost.
Produced in the liver in vertebrates.
(Mammals, amphibians, some marine fish)
Uric acid as nitrogenous waste
Least toxic, highly concentrated (lipid-soluble rather than water-soluble) conserves water/weight. But very energy expensive.
(Birds, reptiles, terrestrial inverts)
Filtrate
The fluid extracted by filtration system.
Steps of filtration
- Filtrate is collected - water and small molecules collected due to blood pressure.
- Reabsorption of valuable molecules.
- Secretion of more wastes into filtrate.
- Excretion of modified filtrate.
Main blood vessels supplying/draining a kidney
Renal artery & Renal vein.
Three main “layers” of tissue in a kidney
- Renal cortex; where nephrons start/end.
- Renal medulla; where nephron tubules descend into.
- Renal pelvis; collects filtrate from nephrons.
Nephrons
Filtrating ‘units’ in kidneys.
Each has a glomerulus (capillary ball) that supplies filtrate, and tubules that process the filtrate.
Two types of nephrons
- Cortical nephrons (more common, mostly in cortex)
- Juxtamedullary nephrons (conserves water, descends deeper)
Bowman’s capsule
The start of nephron tubule that encapsulates a glomerulus (the capillaries).
Glomerulus
Pronounced “Glo-MAIR-yu-lus”
Ball of capillaries from a renal arteriole that creates the filtrate into nephron tubules.
Loop of Henle
Middle part of nephron tubule that descends into medulla and then ascends back.
Has closely associated capillaries. Modification of filtrate happens here.
Vasa recta
Capillaries that serve the loop of Henle in the renal medulla.
Variation in osmolarity in the kidney
The inner layers (medulla) have much higher osmolarity than the cortex; urine becomes more concentrated as it descends into renal pelvis.
3 main classes of hormones
- Polypeptides (water-soluble)
- Steroids (lipid-soluble)
- Amines (water-soluble)
Also some other lipid-soluble stuff, like vitamins.
Transport of lipid-soluble hormones
Bound to transport proteins which allows them to be soluble in blood.
Structure of steroids
- Lipids with 4 fused carbon rings
- Derived from cholesterol
Endocrine vs Paracrine signalling
Endocrine - into bloodstream and distributed through body.
Paracrine - into interstitial fluid and targets neighbouring cells.
Autocrine signalling
The cell that releases the hormone has a response to it - regulation of its own activity.
Neuroendocrine signalling
Special neurons produce the hormone, which is then brought into the bloodstream.
Posterior pituitary hormones
Oxytocin and ADH (antidiuretic hormone)
Differences between Posterior vs Anterior pituitary glands
Posterior:
- extension of hypothalamus.
- stores hormones from hypothalamus to release when needed.
Anterior
- not nervous tissue.
- receives hormones from hypothalamus to secrete its own hormones.
Tropic hormones
Hormones that are an intermediate step in a hormone cascade; they don’t cause an effect themselves, but they signal cells to produce another hormone.
Thyroid hormone pathway
Hypothalamus: TRH (thyrotropin-releasing hormone)
Anterior pituitary: TSH (thyroid-stimulating hormone)
Thyroid gland: TH (thyroid hormone)
Adrenal gland structure
- Located above kidneys (ad-renal)
- Outer cortex has true endocrine cells
- Inner medulla is derived from nerve tissue
Adrenal medulla hormones & triggering stimulus
Adrenaline & Noradrenaline
- Stimulated by nerve signals from brain
Adrenal cortex hormones & triggering stimulus
A range of different corticosteroids that maintain blood homeostasis in response to low glucose/shock/bleeding.
- Stimulated by tropic hormones from brain
Effects of adrenaline/epinephrine
- Raise blood glucose levels
- Raise blood pressure & metabolic rate
- Faster/deeper breathing & heartbeats
- Diverts blood flow
Antidiuretic hormone (ADH)
Secreted by posterior pituitary.
Promotes water reabsorption in kidneys.
Androgens
Steroid hormones that promote male characteristics.
Includes testosterone.
Oestrogens vs Progesterone
Oestrogens - Steroid hormones that promote female characteristics.
Progesterone - Contributes to menstrual cycle.
Oestradiol
The main oestrogen in mammals.
Gonadotropins
Hormones that control production of the main sex hormones.
Luteinizing hormone (LH) & Follicle-stimulating hormone (LSH)
