Mechanisms of Homeostasis

Homeostasis is like your home’s thermostat Thermostat’s set point is 75ºF Inside temperature = heat 72ºF73ºF74ºF75ºF

Defined: Process where the body maintains a constant internal environment Importance: Internal reactions & enzymes work best in specific conditions Control systems adjust to internal/external changes Changes controlled: pH, temp, fluids

Control Systems Sensors (aka: receptors) –Gather information about the body and environment –Ex: skin senses pressure Communication Center –Messages sent throughout the body to respond –Ex: Impulse travel through your nerves Control Center –Receives information from the sensors –Ex: Brain interprets the impulse Targets –Body part that changes its activity –Ex: Muscles in foot stretch/contract abruptly !*%!?%&#

Negative Feedback Loops Regulates most of the body Reverses any change that moves conditions from a set point –Ex: if your temp drops…you will shiver to generate heat

Negative Feedback Loops Regulates most of the body Reverses any change that moves conditions from a set point –Ex: if your temp drops…you will shiver to generate heat –Ex: If your temp rises…you will sweat to cool down

Negative Feedback Loop: Cold Response

Negative Feedback Loop: Breathing

Positive Feedback Loop Increases the changes away from set points Important when rapid change is needed Ex: Pregnancy contractions –Uterus contractions begin slowly –Oxytocin released to speed up the contractions Ask yourself… If this was negative feedback, what would happen next? Negative feedback would reverse and stop the contractions. But if the contractions stopped, would the baby be delivered? So how will the body respond to the contractions if it’s positive feedback?

Working Together Thermoregulation: Maintenance of body temperature –Skin: sensors detect cold –Nervous system: electrical impulse sent to brain –Endocrine system: releases hormones into blood stream –Muscles: Hormones cause shivering

Some disruptions temporary –Infections, fever, sore throats, muscle soreness Some disruptions too great for your body to control –Frost bite: Sensors are destroyed –Paralysis: Messages from brain doesn’t reach target Beck Weathers, thought to be dead, survived a night exposed to Mt. Everest cold. Homeostasis disruption

Normal Insulin Production Cells needs glucose Mitochondria uses glucose to make ATP energy After meals, glucose levels in the blood increase Blood cell

Normal Insulin Production Cells needs glucose Mitochondria uses glucose to make ATP energy After meals, glucose levels in the blood increase Blood cell G G G G G G G G G G G G G Alert! High blood sugar

Normal Insulin Production But the channels (doors) that allow glucose into your cells are closed Your pancreas responds by releasing insulin into the blood stream Blood cell G G G G G G G G G G G G G closed Alert! High blood sugar

Normal Insulin Production But the channels (doors) that allow glucose into your cells are closed Your pancreas responds by releasing insulin into the blood stream Blood cell G G G G G G G G G G G G G i i i i i i i i i i Alert! High blood sugar

Normal Insulin Production Insulin causes the channels (doors) to open Glucose diffuses into the cells, giving them much needed nutrition Blood cell G G G G G G G G G G G G G iii iii i ii i Alert! High blood sugar

Normal Insulin Production Insulin causes the channels (doors) to open Glucose diffuses into the cells, giving them much needed nutrition Glucose level in blood returns to normal Blood cell iii iii i ii i G G G G G G G G G G G G G Alert! High blood sugar

Diabetes Cells needs glucose Mitochondria uses glucose to make ATP energy After meals, glucose levels in the blood increase Blood cell

Diabetes Cells needs glucose Mitochondria uses glucose to make ATP energy After meals, glucose levels in the blood increase Blood cell G G G G G G G G G G G G G Alert! High blood sugar

Diabetes But the channels (doors) that allow glucose into your cells are closed A damaged pancreas will often release too little insulin Blood cell G G G G G G G G G G G G G Alert! High blood sugar

Diabetes But the channels (doors) that allow glucose into your cells are closed A damaged pancreas will often release too little insulin Blood cell G G G G G G G G G G G G G Alert! High blood sugar i i

Diabetes But the channels (doors) that allow glucose into your cells are closed A damaged pancreas will often release too little insulin Reduced insulin causes only a few channels (doors) to open Blood cell G G G G G G G G G G G G G i i Alert! High blood sugar

Diabetes Very little glucose can diffuse into the cells The glucose level in the blood never returns to normal Hours later, the next meal adds even more glucose Blood cell i i G G G G G G G G G G G G G Alert! High blood sugar

Diabetes Very little glucose can diffuse into the cells The glucose level in the blood never returns to normal Hours later, the next meal adds even more glucose Blood cell i i G G G G G G G G G G G G G G G G G G G G G G G G G G G G G G G G G GG G G G G G G G G G G G Alert! High blood sugar

Diabetes Ironically, the cells begin to starve even though food is nearby The blood becomes acidic Negative effects: heart disease, high blood pressure, stroke, death Blood cell i i G G G G G G G G G G G G G G G G G G G G G G G G G G G G G G G G G G G GG G G G G G G Alert! High blood sugar

Diabetes Treatment Insulin injections Insulin causes the channels to open and allows glucose to enter the cells Blood cell i i G G G G G G i i i i i ii i G G G G G G G G G G G G G G G G G G G G G G G G G G G G G G GGG G G GG

Review 1)Define homeostasis. 2)Name and describe the four parts of the “control system.” 3)What is negative feedback? 4)What is positive feedback? 5)Is the following example positive or negative feedback? During heavy exercise your body loses water when you sweat. As a result of water loss, your body redirects the remaining water inside your body to vital parts of your body to replenish these vital organs. 6)What is diabetes? 7)Which organ releases insulin? 8)What happens when glucose levels are too high in the blood?