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Homeostasis and excretion.

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Introduction

Homeostasis and excretion. Homeostasis: mechanism that maintains the internal environment at a constant level. This including the blood pH, the O2 and CO2 levels, blood glucose level, blood temperature and the water balance. This is all controlled by a negative feedback system; in this the product controls its own production. This system has three parts to it: 1. Sense organ that senses the difference, 2. Control centre generates a message for 3 to act, 3. Response organ this brings on the change, after receiving the message. Due to these parts, homeostasis needs the CNS and the endocrine systems to help it control it all. Thermo-regulation: Thermo-receptors in the skin monitor the skin temperature. ...read more.

Middle

Cold = goose bumps. When the body is hot the thyroid gland stops producing thyroxin (a hormone) so that you loose your appetite. Osmo-regulation: control of the H2O, through ADH. When cells loose water you feel thirsty. Bi-carbonates: controls the blood pH. Liver: controls the glucose levels. When glucose rich blood passes through the pancreas, chemoreceptors tell how much glucose there is in the blood, and relative to this info insulin is made. In the pancreas Islets of hangerhams are present: * Alpha cells: produce glucogen, this transforms glycogen into glucose * Beta cells: produce insulin, transforms glucose into glycogen. Insulin and glucogen are antagonistic hormones. If the glucose level in the blood is too high, osmosis occurs and the RBC's would decrease. ...read more.

Conclusion

The pre-urine remains isotonic (same conc. Level as the blood.) Loop of Henley: The loop goes down where water is re-absorbed. In the loop going up, NaCl is taken out. This part of the loop is impermeable for water, as the descending part of the loop is impermeable for NaCl. In the collecting duct water is still taken out, which means the urine is hypertonic compared to the blood. You should still find water in this duct because it is close to the others. The permeability of the duct depends on the ADH levels. (High conc.- more released, low conc.- less released) Dialysis: a sort of artificial kidney. It works with the process of diffusion. The patient's blood goes through a machine that cleans it out for them. ...read more.

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