Homeostasis and Human Body Systems Miss Richardson SBI

Homeostasis and Human Body Systems Miss Richardson SBI 4 U

How would you feel if you were here?

How would you feel if you were here?

How would you feel? South Pole, <41°C

Homeostasis • … is the tendency of the body to maintain a constant internal environment • This is done through regulating various systems • Human body: body temp: 37⁰C blood p. H: 7. 3 – 7. 4 Blood sugar: 5 mmol/L blood

Feedback Systems • The body maintains homeostasis through feedback systems • Feedback systems consist of three components: • Receptor/sensor – detect the stimuli/change in internal environment and send signal to control centre • Integrator/Control Centre – receives information and takes appropriate action • Effector – cause change and make a response to change conditions

Negative Feedback Systems Most homeostatic mechanisms in animals use negative feedback systems to operate Negative Feedback Systems: � brings the system back to its original state If a level increases, the body works to decrease it If a level decreases, the body works to increase it • Example: • When you exercise, your muscles produce heat, raising your body temperature • Signals are sent to control centre to induce sweating and dilation of blood vessels • Results in heat loss through radiation and conduction

Why does the body need to regulate temperature? • Human enzymes work best at 37°C. • The hypothalamus is a part of the brain that detects change in internal body temperature. • Thermoregulation is the process of regulating body temperatures • When we are hot: • Erector muscles in skin relax, allowing hairs to lie flat so the body is less insulated • Vasodilation – blood capillaries near the skin’s surface get wider, and more blood flows near skin surface • allows for more heat loss due to radiation • Sweat glands secrete – allows for cooling due to evaporation

Thermoregulation • When we are cold: • Shivering – muscles contract and relax quickly to release heat • Rate of cellular respiration increases to release heat and energy • Vasoconstriction – blood capillaries near skin surface narrow to keep blood near the core of the body and conserve heat • Hairs on skin stand up – erector muscles contract, allowing more air to be trapped between hairs to act as insulating layer • Sweat secretion is reduced

Thermoregulation

Positive Feedback Systems • Positive Feedback Systems: • moves system further from the steady state • Example: • In labour, a woman’s uterine muscles contract, triggering production of oxytocin • Oxytocin increases strength of contractions

Feedback Systems • Other examples of positive feedback systems include: • Platelets – when platelets clump to form blood clots that signals more platelets are activated • Lactation – when breastfeeding, the more the baby suckles the more milk is produced • Estrogen – during follicular phase it causes the thickening of the uterine lining • Nerve signals – Na+ channels open when stimulated, this causes more Na+ channels to open resulting in an action potential