Tuesday, December 4, 2007

Regulating the Internal Environment

Today we learned a way cells maintain homeostasis. Negative feedback occurs, this is where different receptors and effectors bring about a reaction to maintain the favourable balance.

During class we went over a few specific examples. Ms. Foglia explained to us the regulation of body temperature. When the body's temperature increases the brain sends nerve signals through the body causing us to sweat and dilates the surface blood vessels. Also she explained the body's response to a decrease in body temperature. In this case the body sends nerve signals through the body causing us to shiver and constrict the surface blood vessels.

We also went over negative feedback in the endocrine system. We went over blood osmolarity, which is the measurement of the concentration of solutes dissolved in the water. Blood osmolarity affects blood pressure. When increased blood pressure increases. When blood pressure and blood osmolarity are increased the pituitary gland releases anti-diuretic hormones (decrease the need to urinate). This increases water reabsorption and increases thirst, bringing blood pressure back to its set point. When blood osmolarity and blood pressure are low JuxtaGlomerular Apparatus releases renin which activates angiotensinogen. Angiotensinogen is an inactive protein but in this process is activated, becoming angiotensin (zymogen). The angiotensin triggers the aldosterone which increases the absorption of salt and water in the kidneys.

This occurs not only in our bodies but in our everyday lives. We too use negative feedback, when criticized we change to make ourselves better.

Tomorrow's sherpa will be Mia =]

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