Human Body Systems and Homeostasis Human Body Systems & Homeostasis

Organization of Living Things The trillions of cells in your body can be organized into approximately 100 different types of cells. Cells that perform a common function are organized into tissues, which are organized into organs. Organs work together in systems. Smooth muscle cells make up smooth muscle tissue. Smooth muscle tissue lines the inside of the urinary bladder, an organ that is part of the excretory (urinary) system. Human Body Systems & Homeostasis

Human Body Systems Transport materials in the body via circulatory (blood, nutrients, oxygen, cellular waste), lymphatic (fat and excess tissue fluid), and immune systems Add or remove substances from blood via digestive, respiratory, and excretory systems Communicate with the brain and spinal cord via the integumentary system (hair, skin, nails, glands) Continued… Human body systems perform the following functions: Human Body Systems & Homeostasis

Human Body Systems Enable the body to move through the muscular and skeletal systems Allow responses from external and internal stimuli via the nervous system Secrete chemicals for messaging between cells using the endocrine system Produce sex hormones and produce and transport gametes via reproductive systems Human Body Systems & Homeostasis

Homeostasis Homeostasis is the tendency of the body to maintain a relatively constant internal environment. It is dynamic and allows for fluctuations throughout the day and night.  Some of the variables controlled are: -temperature -blood glucose concentration -blood pH -blood pressure -heart rate Human Body Systems & Homeostasis

Feedback Systems Homeostasis is continuously disturbed by external or internal stimuli. Body systems constantly monitor changes and maintain homeostasis through both negative and positive feedback systems. A feedback system consists of: a sensor, which detects changes and sends signals to the control centre a control centre, which sets the range of values within which a variable should be maintained, receives information from sensors, and sends signals to effectors an effector, which responds to signals from a control centre to effect change in a variable Human Body Systems & Homeostasis

Negative Feedback Systems In a negative feedback system, the body works to reverse a change detected in a variable so that the variable is brought back to within a normal range. Most variables are maintained by negative feedback loops. (A) In a negative feedback system, homeostasis is returned to normal. (B) Body temperature is maintained by a negative feedback system. Human Body Systems & Homeostasis

Thermoregulation Decreasing body temperature: –As you sweat and the perspiration evaporates from your skin, it requires heat –When your blood vessels dilate (vasodilation), more blood is brought to surface of skin, resulting in heat loss through radiation and conduction Increasing body temperature: –When you shiver, muscles contract repeatedly, which increases heat production –When your blood vessels constrict (vasoconstriction), heat loss through the skin is decreased Human Body Systems & Homeostasis

Positive Feedback Systems Positive feedback systems tend to strengthen or increase a change in a variable. Contractions during childbirth is a variable controlled by a positive feedback system. This loop has a definitive cut-off point to stop amplification of the response. Contractions during childbirth are regulated by a positive feedback system. Human Body Systems & Homeostasis