unit b: human body systems chapter 8: human organization: section 8.4 chapter 9: digestive system...
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UNIT B: Human Body Systems
Chapter 8: Human Organization:
Section 8.4
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
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.
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What situations might disrupt the internal state of the body?
How can alleviating stress improve your health and quality of life?
8.4 Overview of the Endocrine System
The endocrine system consists of glands and tissues that secrete hormones.
•Hormones are chemicals that affect the behaviour of other glands or tissues
o Can act on sites far away from the sites of production by being carried in the bloodstream
o Some hormones are not carried in the bloodstream and can affect neighbouring cells (local hormones)
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Section 8.4
• Functions of hormones:o Maintain homeostasiso Involved in body’s response to stresso Act on the brain to influence behaviouro Promote cell division and mitosis (growth factors)
• Endocrine glandso Secrete hormones into tissue fluido Hormones diffuse into the bloodstream for
distribution to the body
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Section 8.4
UNIT B Chapter 8: Human Organization
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Section 8.4
Figure 8.9 The endocrine system. Anatomical location of major endocrine glands in the body. Other organs, such as the kidneys and heart, produce hormones. However, hormone production is not a primary function of these organs.
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Section 8.4
UNIT B Chapter 8: Human Organization
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Section 8.4
Hormones and Homeostasis
Hormones secreted by the endocrine system must reach their target organs via the blood. This results in a slower but more prolonged response compared to that of the nervous system, which is organized to respond rapidly to stimuli by transmitting nerve impulses.
The production of hormones is controlled in two ways:
•Negative feedback
•Action of other hormones
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Section 8.4
Negative feedback regulation of hormones:
•An endocrine gland can be sensitive to either the condition it is regulating or the blood level of the hormone it is producing. For example,
o Blood glucose rises, causing pancreas to produce insulin
o Insulin causes liver to store glucose, causing glucose removal from the blood (stimulus of insulin production is inhibited)
o Pancreas stops producing insulin
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Section 8.4
Other hormones regulating hormones:
•The effect of a hormone can be controlled by the release of an antagonistic hormone
o The effect of insulin can be offset by the production of the hormone glucagon from the pancreas
o Insulin lowers blood sugar level, while glucagon raises it
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Section 8.4
Check Your Progress
1. List six major human endocrine organs.
2. Explain what it means to say that secretion of a hormone is regulated by negative feedback.
UNIT B Chapter 8: Human Organization
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Section 8.4
UNIT B Chapter 8: Human Organization
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Section 8.4