Homeostasisq Defined as maintenance of a relatively stable internal environment Defined as maintenance of a relatively stable internal environment Homeostasis is essential for survival and function of all cells. Homeostasis is essential for survival and function of all cells.

Maintenance of Homeostasis Nervous system Nervous system Controls and coordinates bodily activities that require rapid responses. Controls and coordinates bodily activities that require rapid responses. Detects and initiates reactions to changes in external environment and internal environment. Detects and initiates reactions to changes in external environment and internal environment. Endocrine system Endocrine system Secreting glands of endocrine regulate by release of hormones. Secreting glands of endocrine regulate by release of hormones.

Control of Homeostasis Homeostasis is continually being disrupted by: Homeostasis is continually being disrupted by: External stimuli External stimuli heat, cold, lack of oxygen, pathogens, toxins heat, cold, lack of oxygen, pathogens, toxins Internal stimuli Internal stimuli Body temperature Body temperature Blood pressure Blood pressure Concentration of water, glucose, salts, oxygen, etc. Concentration of water, glucose, salts, oxygen, etc. Physical and psychological distresses Physical and psychological distresses

Stimuli Demo Ice Water and Heart Rate/Blood Pressure. Ice Water and Heart Rate/Blood Pressure.

Homeostasis Components There are three main components (players) involved when homeostasis is disrupted by a stimuli. There are three main components (players) involved when homeostasis is disrupted by a stimuli. The Receptor The Receptor The Control Center The Control Center The Effector The Effector

Receptors The receptor is an organ or sensor that receives the chemical signal and communicates to the next Component ( the control center). The receptor is an organ or sensor that receives the chemical signal and communicates to the next Component ( the control center). In the case of blood sugar the liver is the main receptor. In the case of blood sugar the liver is the main receptor.

Homeostatic Control Systems The control system must be able to: The control system must be able to: Receives signal from the receptor. It also can sense deviations from the norm its self. Receives signal from the receptor. It also can sense deviations from the norm its self. Integrate this information with other relevant information. Integrate this information with other relevant information. Sends a signal to the appropriate organ or gland to make the necessary adjustment. Sends a signal to the appropriate organ or gland to make the necessary adjustment. Generally the Brain (hypothalamus) is the control center. However, the pancreas is its own control center for blood sugar.

Effector Effector The effector is the component that causes the change. It sends out the chemical to deal with the stimulus. The effector is the component that causes the change. It sends out the chemical to deal with the stimulus. In the case of blood sugar the pancreas would be the effector because it sends out the insulin. In the case of blood sugar the pancreas would be the effector because it sends out the insulin.

Homeostatic Control Systems Feedback - refers to responses made after change has been detected Feedback - refers to responses made after change has been detected Types of feedback systems Types of feedback systems Negative Negative Positive Positive

Feedback Loops: Types Negative feedback loop Negative feedback loop original stimulus reversed (shut off) original stimulus reversed (shut off) most feedback systems in the body are negative most feedback systems in the body are negative Positive feedback loop Positive feedback loop original stimulus intensified original stimulus intensified seen during normal childbirth seen during normal childbirth

Negative Feedback Loop

Negative Feedback & Blood Pressure Baroreceptors in walls of blood vessels detect an increase in BP Baroreceptors in walls of blood vessels detect an increase in BP Brain receives input and signals blood vessels and heart Brain receives input and signals blood vessels and heart Blood vessels dilate, HR decreases Blood vessels dilate, HR decreases BP decreases BP decreases

Positive Feed Back In this case the stimuli causes an increase in the original stimulus. In this case the stimuli causes an increase in the original stimulus.

Positive Feedback during Childbirth Stretch receptors in walls of uterus send signals to the brain Stretch receptors in walls of uterus send signals to the brain Brain induces release of hormone (oxytocin) into bloodstream Brain induces release of hormone (oxytocin) into bloodstream Uterine smooth muscle contracts more forcefully Uterine smooth muscle contracts more forcefully More stretch, more hormone, more contraction etc. More stretch, more hormone, more contraction etc. Cycle ends with birth of the baby & decrease in stretch Cycle ends with birth of the baby & decrease in stretch

Feed Back Graphs To be Drawn. To be Drawn.