1. Presentation title slide

2. UNIT B: Human Body Systems
Chapter 8: Human Organization:
Section 8.3
Chapter 9: Digestive System
Chapter 10: Circulatory System and Lymphatic System
Chapter 11: Respiratory System
Chapter 12: Nervous System
Chapter 13: Urinary System
Chapter 14: Reproductive System

3. Chapter 8: Human Organization
UNIT B
Chapter 8: Human Organization
Chapter 8: Human Organization
In this chapter, you will learn about how the systems in our bodies are connected and work together to maintain a relatively constant internal environment.
What situations might disrupt the internal state of the body?
How can alleviating stress improve your health and quality of life?
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4. UNIT B
Chapter 8: Human Organization
Section 8.3
8.3 Homeostasis
Homeostasis is the maintenance of a relatively constant internal environment by an organism or single cell.
Internal conditions in the body stay within a narrow range (e.g., body temperature stays at 37ºC)
The internal state of the body is a dynamic equilibrium, since internal conditions are not absolutely constant
Illness can result if the internal conditions change to a great degree
homeostasis: the internal environment of an organism staying relatively constant
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5. Negative Feedback UNIT B
Chapter 8: Human Organization
Section 8.3
Negative Feedback
Negative feedback is the main homeostatic mechanism that keeps a variable close to a set point.
A homeostatic system has at least two components:
Sensor: detects a change in internal conditions
Control centre: directs a response that brings conditions back to normal
negative feedback: the primary homeostatic mechanism that keeps a variable close to a particular value, or set point
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6. UNIT B Chapter 8: Human Organization Section 8.3
Figure 8.5 Negative feedback mechanism. The sensor and control centre of a feedback mechanism work together to keep a variable close to a particular value.
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7. Examples of negative feedback
UNIT B
Chapter 8: Human Organization
Section 8.3
Examples of negative feedback
Regulation of room temperature
Thermostat is set at 20ºC (set point)
Temperature above set point:
The sensor (thermometer in thermostat) detects the increase in temperature
The control centre (also in the thermostat) turns the furnace off, and the room cools
Temperature below set point:
The sensor detects the decrease in temperature
The control centre turns the furnace on, and the room warms
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8. UNIT B Chapter 8: Human Organization Section 8.3
Figure 8.6 Complex negative feedback mechanism. When a room becomes too warm, negative feedback allows the temperature to return to normal. A contrary cycle, in which the furnace turns on and gives off heat, returns the room temperature to normal when the room becomes too cool.
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9. The body temperature set point is 37ºC Temperature above set point:
UNIT B
Chapter 8: Human Organization
Section 8.3
Regulation of body temperature
The body temperature set point is 37ºC
Temperature above set point:
The sensor (hypothalamus in the brain) detects the increase in temperature
The control centre (also in the hypothalamus) directs the blood vessels in the skin to dilate and activates sweat glands
Temperature below set point:
The sensor detects the decrease in temperature
The control centre directs the blood vessels in the skin to constrict and inactivates sweat glands
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10. UNIT B Chapter 8: Human Organization Section 8.3
Figure 8.7 Regulation of body temperature. Normal body temperature is maintained by a negative feedback system.
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11. Positive Feedback UNIT B
Chapter 8: Human Organization
Section 8.3
Positive Feedback
Positive feedback is a mechanism that brings about an even greater change in the same direction.
Example: blood clotting
Injured tissues release chemical factors that activate platelets
Platelets initiate the clotting process and release factors that stimulate further clotting
positive feedback: a homeostatic mechanism that brings about an ever greater change in the same direction
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12. Homeostasis and Body Systems
UNIT B
Chapter 8: Human Organization
Section 8.3
Homeostasis and Body Systems
All body systems contribute toward maintaining homeostasis.
The Transport Systems
Circulatory system: conducts blood to and away from capillaries where exchange of gases, nutrients, and wastes occurs; regulates tissue fluid composition
Lymphatic system: collects excess tissue fluid, which is returned via lymphatic vessels to the circulatory system
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13. UNIT B Chapter 8: Human Organization Section 8.3
Figure 8.8 Regulation of tissue fluid composition. Cells are surrounded by tissue fluid, which is continually refreshed because oxygen and nutrient molecules constantly exit, and carbon dioxide and waste molecules continually enter the bloodstream.
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14. The Maintenance Systems
UNIT B
Chapter 8: Human Organization
Section 8.3
The Maintenance Systems
Respiratory system: adds oxygen and removes carbon dioxide from the blood; regulates blood pH
Digestive system: ingests and digests food, providing nutrients to the blood to replace nutrients that are used in body cells
Liver: regulates blood glucose and removes toxic chemicals
Urinary system: kidneys regulate blood volume, salt balance, and pH
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15. UNIT B
Chapter 8: Human Organization
Section 8.3
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