Downloaded 16 times
Uploaded byMohd Asif Kanth
Homeostasis
The document discusses homeostasis and osmoregulation. It explains that homeostasis refers to the maintenance of a stable internal environment through physiological and behavioral controls like negative and positive feedback loops. Osmoregulation maintains water balance and involves diffusion, osmosis, and active transport of water and solutes. It then describes osmoregulatory mechanisms in invertebrates, fish, and the mammalian kidney which filters blood, secretes and reabsorbs solutes via the nephron to produce concentrated urine and regulate water balance.
More Related Content
![Transport in plants AS Biology [jm]](https://cdn.slidesharecdn.com/ss_thumbnails/transportinplantsasjm-121015152537-phpapp01-thumbnail.jpg?width=640&height=640&fit=bounds)
![Chapter 25: Excretion [compatibility mode]](https://cdn.slidesharecdn.com/ss_thumbnails/chapter25-excretioncompatibilitymode-141214135059-conversion-gate01-thumbnail.jpg?width=640&height=640&fit=bounds)
Homeostasis
- 1. Homeostasis Biology 2: Formand Function MOHD ASIF KANTH M.SC ZOOLOGY ,B.ED 9070262786 [email protected]/asifkant [email protected]
- 2. Overview • Homeostasis =maintenance of constant internal environment • Physiological controls – Negative feedback loops – Positive feedback loops • Behavioral controls [email protected]/asifkant [email protected]
- 3.
- 4.
- 5.
- 6.
- 7.
- 8.
- 9.
- 10.
- 11. Osmoregulation • Water isvital to the chemistry of life • Therefore, must attain a water balance within the body • Water balance systems are based on three processes: – Diffusion – Osmosis – Active transport • Osmoregulation processes often tied to excretion [email protected]/asifkant [email protected]
- 12. • Diffusion – Thespread of molecules along a concentration gradient by brownian motion, towards a state of entropy • Osmosis (the diffusion of water) – Water moves from a low solute concentration (hypotonic) to a high solute concentration (hypertonic) • Active transport – The movement of molecules across a membrane, usually against a gradient, involving the expenditure of energy [email protected]/asifkant [email protected]
- 13.
- 14. Osmoregulation in invertebrates •Since most invertebrate phyla evolved in water, no shortage • However, differences in concentration between the cell and the solution surrounding it may cause problems – e.g., Amoeba in freshwater: hypertonic cell in hypotonic solution – Result: movement of water into cell – Defense: Contractile vacuole pumps out water [email protected]/asifkant [email protected]
- 15. • Multicellular organismsuse transport epithelia to control water loss and excretion – Platyhelminthes • Protonephridia (flame cells) collect excess water in addition to nitrogenous wastes, empty into nephridiopore, excretes NH3 – Annelida • Metanephridia organized on a per segment basis collect waste from coelom via the nephrostome, counters water uptake by epidermis, excretes NH3 – Insecta • Malpigian tubules collect nitrogenous wastes from haemocoel, excretes Uric [email protected]/asifkant [email protected]
- 16.
- 17.
- 18.
- 19.
- 20. Osmoregulation in fish •Depends on environment – Freshwater • Cells are hypertonic to environment, must defend against water uptake – Excretion of dilute urine – Mucous covering of epidermis – Marine • Cells are hypotonic to environment, must defend against water loss – Water gain through food uptake and drinking – Concentration of urine [email protected]/asifkant [email protected]
- 21.
- 22.
- 23.
- 24.
- 25.
- 26.
- 27.
- 28.
- 29. Filtration • Occurs inBowmans capule – Afferent arteriole from renal artery enters glomerulus, exits via efferent arteriole – Blood filtered by capsule: all non-cellular products pushed into nephron (proximal tubule) – Filtrate includes products that must be retained: blood sugars, salts and vitamins [email protected]/asifkant [email protected]
- 30.
- 31.
- 32. Secretion • Occurs inproximal and distal tubule • Secretion is initially active, although certain molecular transport occurs passively as a result • e.g., NaCl actively pumped out, H2O follows [email protected]/asifkant [email protected]
- 33.
- 34. Reabsorption • Materials thatmust be retained are brought back by active transport or passive diffusion • Result of absorption/secretion in Loop of Henle is highly concentrated urine • Nephron tubule is lined by transport epithelia • Amount of water retained is controlled by hormones that control activity of transport [email protected]/asifkant [email protected]
- 35. The Loop ofHenle • Descending limb is permeable to water but not NaCl • H2O moves by osmosis to high salt concentration in interstitial fluid • Thin segment of ascending limb is permeable to NaCl which moves passively by diffusion to equalize gradient • Thick segment of ascending limb actively transports [email protected]/asifkant [email protected]
- 36.
- 37.
- 38.
- 39.