All details about today pptbHomeostasis.pptx

details about today pptbHomeostasis.pptx

1. Anatomy & Physiology Homeostasis

2. Objectives At the end of the lecture, students will able to Define the term “Homeostasis”. Discuss factors which effect Homeostasis. Define feedback mechanisms and its components. Discuss the role of feedback mechanisms in the maintenance of homeostasis with example.

3. Homeostasis is the regulation and maintenance of the internal environment of the body

4. Homeostasis Homeostasis Conditions within the body must remain within a narrow range – like your body temperature Homeostasis involves keeping the internal environment within set ranges

5. Homeostasis Cont.… A property of cells, tissues, and organisms that allows the maintenance and regulation of the stability and constancy needed to function properly . Homeostasis   refers to the body's need to reach and maintain a certain state of equilibrium. The term was first coined by a physiologist named Walter Cannon in 1926. More specifically, homeostasis is the body's tendency to monitor and maintain internal states, such as temperature and blood sugar, at fairly constant and stable levels.

6. Homeostasis Cont.… Homeostasis is a healthy state that is maintained by the constant adjustment of biochemical and physiological pathways. An example of homeostasis is the maintenance of a constant blood pressure in the human body through a series of fine adjustments in the normal range of function of the hormonal, neuromuscular, and cardiovascular systems. These adjustments allow the maintenance of blood pressure needed for body function despite environmental changes and changes in a person's activity level and position. Other homeostatic mechanisms, for example, permit the maintenance of body temperature within a narrow range.

7. How Is It Maintained ? Your body has set points for a variety of states including temperature, weight, sleep, thirst, and hunger. When the level is off (in either direction, too much or too little), homeostasis will work to correct it. For example, to regulate temperature, you will sweat when you get too hot or shiver when you get too cold . Another way to think of it is like the thermostat in your house. Once set at a certain point, it works to keep the internal state at that level. When the temperature drops in your house, your furnace will turn on and warm things up to the preset temperature.

8. Conti…………. In the same way, if something is out of balance in your body, a physiological reaction will kick in until the set point is once again reached. Here's how the primary components of homeostasis work: Stimulus : A stimulus from a change in the environment kicks something out of balance in the body. Receptor : The receptor reacts to the change by informing the control unit. Control unit : The control unit then communicates the change needed to bring the body back into balance. Effector : The effector receives this information and acts on the change that is needed.

9. Control systems help maintain homeostasis. Sensors gather data Control center receives data, sends messages Communication system delivers messages to target organs, tissues Targets respond to change pore sweat glands hair follicle muscle goose bump

10. Feedback mechanism A feedback loop will work to decrease or increase the effect of the stimulus. There are two type of feedback, positive and negative. Positive feedback increase the effect of the stimulus while negative feedback decrease the effect of the stimulus. In homeostasis, negative feedback loops are most common, as the body is typically attempting to decrease the effect of the stimulus to get the body back to equilibrium .

11. Positive Feedback Positive feedback is a mechanism in which an output is enhanced in order to maintain homeostasis. Positive feedback mechanisms are designed to accelerate or enhance the output created by a stimulus that has already been activated. Positive feedback mechanisms are designed to push levels out of normal ranges.

12. Positive Feedback Cont... This process can be beneficial but is rarely used because it may become uncontrollable. A positive feedback example is blood platelet accumulation and aggregation, which in turn causes blood clotting in response to an injury of the blood vessels.

13. Negative Feedback Negative feedback mechanisms reduce output or activity to return an organ or system to its normal range of functioning. Regulation of blood pressure is an example of negative feedback. Blood vessels have sensors called baroreceptors that detect if blood pressure is too high or too low and send a signal to the hypothalamus. The hypothalamus then sends a message to the heart, blood vessels, and kidneys, which act as effectors in blood pressure regulation.

14. Negative Feedback Cont.… If blood pressure is too high, the heart rate decreases as the blood vessels increase in diameter ( vasodilation ), while the kidneys retain less water. These changes would cause the blood pressure to return to its normal range. The process reverses when blood pressure decreases, causing blood vessels to constrict and the kidney to increase water retention.

15. Negative Feedback Cont.… Temperature control is another negative feedback mechanism. Nerve cells relay information about body temperature to the hypothalamus. The hypothalamus send signals several effectors to return the body temperature to 37 degrees Celsius (the set point). The effectors may signal the sweat glands to cool the skin and stimulate vasodilation so the body can give off more heat.

16. Negative Feedback Cont.… If body temperature is below the set point, muscles shiver to generate heat and the constriction of the blood vessels helps the body retain heat. This example is very complex because the hypothalamus can change the body’s temperature set point, such as raising it during a fever to help fight an infection. Both internal and external events can induce negative feedback mechanisms.

17. Negative Feedback Loop Example: Holding breath, CO 2 levels rise Control system forces exhale, inhale O 2 / CO 2 level returns to normal