Endocrine & Cell Communication Part II: The STUDENT HANDOUTS 2/4/2013

Endocrine System

• The human endocrine system is composed of a collection of glands that secrete a variety of . • These chemicals use long distance Endocrine & Cell Communication Part II: communication to control the daily functioning The Endocrine System of the cells of the body.

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AP Biology Curriculum Frameworks Endocrine System

• EK 3.D.1 Cell communication processes share common features: • The endocrine system produces more than 30 – d. In multicellular organisms, pathways different chemicals used by your body to coordinate the activities within individual cells. maintain homeostasis and promote normal • EK 3D.2 Cells communicate with each other through direct contact with other cells or from a distance via chemical body function. signaling. • This system contains 9 primary glands as well as – c. Signals released by one cell type can travel long distances to target cells of another cell type. endocrine cells found within major organs. • 1. Endocrine signals are produced by endocrine cells that • The endocrine system is a ductless system that release signaling molecules, which are specific and can employs the circulatory system when delivering travel long distances through the blood to reach all parts of the body. chemical signals over long distances.

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To trust or not to trust? Ask The Endocrine System works with the Nervous System

• Some people trust others easily while others • Two systems coordinate communication require additional time to decide if a person is throughout the body: the endocrine system trustworthy. and the nervous system. • The endocrine system secretes hormones that • A recent article in Scientific American coordinate slower but longer-acting responses indicates that the oxytocin known including reproduction, development, energy, for its role in social attachment and metabolism, growth, and behavior. interaction may also play an important role in • The nervous system conveys high-speed our ability to trust. electrical signals along specialized cells called ; these signals regulate other cells.

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1 Endocrine & Cell Communication Part II: The Endocrine System STUDENT HANDOUTS 2/4/2013

Coordination of Endocrine and Nervous Systems in Table 45.1a Vertebrates Production and Release of Hormones

Neurosecretory • The hypothalamus receives information from the cells of the nervous system and initiates responses through the hypothalamus

endocrine system. Axons • Attached to the hypothalamus is the pituitary gland, composed of the and the posterior Posterior pituitary. pituitary Anterior • The anterior pituitary makes and releases hormones pituitary under regulation of the hypothalamus.

• The posterior pituitary stores and secretes hormones HORMONE ADH Oxytocin that are made in the hypothalamus. TARGET Mammary glands, tubules uterine muscles

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Table 45.1b Anterior and Posterior Pituitary Anterior Pituitary Hormones

• Hormone production in the anterior pituitary is controlled by releasing and inhibiting hormones from the hypothalamus. • For example, -releasing hormone from the hypothalamus stimulates the anterior pituitary to secrete prolactin (PRL), which has a role in milk production and secretion. • Another example is Stimulating Hormone (TSH), which stimulates the thyroid gland to produce thyroxine which stimulates and maintains metabolic processes.

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Figure 45.16 Tropic effects only: Thyroid Regulation: Posterior Pituitary Hormones FSH Neurosecretory LH cells of the A Hormone Cascade Pathway TSH hypothalamus ACTH Nontropic effects only: • The two hormones released from the posterior Prolactin • A hormone can stimulate the release of a series of pituitary act directly on nonendocrine tissues. MSH other hormones, the last of which activates a Nontropic and tropic effects: GH Hypothalamic nonendocrine target cell; this is called a hormone Portal vessels releasing and – Oxytocin regulates milk secretion by the mammary inhibiting cascade pathway. hormones glands and stimulates contraction of the uterus. Endocrine cells of the anterior Posterior pituitary The release of thyroid hormone results from a pituitary • Pituitary – Antidiuretic hormone (ADH) promotes retention of hormones hormone cascade pathway involving the water by the kidneys. hypothalamus, anterior pituitary, and thyroid gland.

HORMONE FSH and LH TSH ACTH Prolactin MSH GH • Hormone cascade pathways typically involve negative

TARGETTestes or ThyroidAdrenal Mammary Melanocytes , bones, feedback. cortex glands other tissues

2 Endocrine & Cell Communication Part II: The Endocrine System STUDENT HANDOUTS 2/4/2013

An Example of Negative Feedback

Created by:

Debra Richards Coordinator of Secondary Science Programs Bryan ISD Bryan, TX

Figure 45.17 Example Pathway Stimulus Cold

Hypothalamus−

− Negative feedbackNegative

Target cells Increased cellular metabolism Response

Figure 45.17 Example Pathway Stimulus Cold

Sensory − Hypothalamus Hypothalamus secretes thyrotropin-releasing hormone (TRH). Neurosecretory cell Releasing hormone Blood vessel

− Anterior pituitary secretes Anterior pituitary thyroid-stimulating hormone (TSH, also known as thyrotropin).

Thyroid gland secretes

Negative feedbackNegative thyroid hormone Endocrine cell (T3 and T4). Hormone

Target Body tissues cells Increased cellular metabolism Response

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