The nervous system and brain work to maintain homeostasis through automatic and voluntary responses. The brain controls the nervous system and regulates physiological processes like temperature, hunger, and sleep. The brain also helps regulate the endocrine system, which produces hormones that stimulate processes to maintain homeostasis. Hormones are transported via the bloodstream and target specific cells, like kidney cells, to signal processes like water reabsorption during dehydration. Feedback systems with both positive and negative feedback help regulate body responses to internal and external changes to maintain homeostasis.

1. Homeostasis and Body Systems Biology 2009

2. Role of the Nervous System The nervous system is very important in maintaining homeostasis within our bodies. The nervous system regulates: Automatic Responses Ex = shivering when cold Voluntary Responses Ex = putting on a sweater

3. The Brain is the Nervous System Control Center Different parts of the brain control different nervous system responses: Receive and transmit information Regulate physiological processes like water balance body temperature hunger sleep

4. The Brain also helps to regulate the Endocrine System The Endocrine System is made of glands and cells that produce and release chemical messages in the form of HORMONES. Hormones stimulate processes that help maintain homeostasis.

5. Hormones Transported in Blood Hormones are chemicals Control balance of sugar absorption by cells, water balance in body, and much more Moved within blood stream past every part of body Recognized only by “Target Cells” with special receptor proteins that can interact with the hormones (like a lock & key)

6. Example of Hormone Function Dehydration: Sensor cells in brain detect water shortage because body has higher sodium concentration when water concentration is low . Brain cells signal for production and release of hormones (ex. Vasopressin) which are carried in the blood throughout the body. 

7. Example of Hormone Function cont… Target cells that have certain receptors for this hormone (kidney cells) receive hormone message. Message signals cell membranes of kidney tubule cells to become more permeable to water. More water is reabsorbed by circulatory system and kept within body. Prevents excess water from being released in urine and restores the water balance.

8. Feedback Systems Groups of body systems that work together to maintain homeostasis in the body. Regulates body responses to changing conditions outside and inside the body. Can be POSITIVE or NEGATIVE

9. Negative Feedback Body detects change Body systems attempt to correct the abnormal situation

10. Positive Feedback Example

11. Positive Feedback Quick response that amplifies the change (instead of “correcting it” in negative feedback)

12. The End