Endocrine System

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The Endocrine System
FOCUS: The endocrine system is one of the major regulatory systems in the body, along with the nervous system. However, the endocrine system responds more slowly, and has a longer-lasting, more general effect on the body than the nervous system. Endocrine tissues internally produce hormones which are released into the blood, where they are carried to target tissue and produce a response. Some hormones bind to receptors on the surface of the cell membrane, producing permeability changes or production of a substance inside the cell. Other hormones diffuse into the cell and cause new proteins to be produced. The secretion of hormones is controlled by negative-feedback mechanisms. The major endocrine glands are the pituitary, thyroid, parathyroids, adrenal glands, pancreas, testes, ovaries, thymus, and pineal body.

Chemical Signals

❛❛Chemical signals, or ligands, are molecules released from one location that move to another❜❜ location to produce a response. A.

Match these terms with the correct statement or definition:

Intercellular chemical signals Intracellular chemical signals 1. Produced in one part of a cell, and travel to another part of the same cell and attach to receptors. 2. Released from one cell, carried in the intercellular fluid, and bind to their receptors on other cells.



Match these terms with the correct statement or definition:

Autocrine Hormones and neurohormones

Neuromodulators and neurotransmitters Paracrine Pheromones

1. Chemical signals released by cells that have a local effect on the same cell type from which the chemical signals were released. 2. Chemical signals released by cells that have effects on other cell types near the cells from which they are released. 3. Intercellular chemical signals secreted into the circulatory system; carried to organs they control, where they bind to receptors and produce a response. 4. Intercellular chemical signals, secreted by nerve cells; important in the function of the nervous system. 5. Chemical signals secreted into the environment that modify the behavior and physiology of other individuals.

❛❛Chemical signals bind to proteins or glycoproteins, called receptor molecules,❜❜ to produce a response. A.


Match these terms with the correct statement or definition:

Intracellular receptors Membrane-bound receptors 1. Receptors located in either the cytoplasm or nucleus of the cell. 2. Receptors that extend across the cell membrane and have a receptor site on the outer surface of the membrane. 3. Relatively small chemical signals that are soluble in lipids bind to these receptors. 4. Large, water-soluble chemical signals that do not diffuse across the cell membrane bind to these receptors. 5. When chemical signals bind to these receptors, messenger RNA synthesis is increased, and new proteins are produced. 6. When chemical signals bind to these receptors, many specific enzymes in the cell may be rapidly activated, producing a cascade effect. 7. Several hours are required between the time when chemical signals bind to these receptors and the response.



Using the terms provided, complete these
cAMP cGMP Enzymes Ion channels

statements: G protein GTP Phosphate

1. 2. 3. 4. 5. 6. 7.

A hormone that binds to membrane-bound receptors may cause (1) to open or close, or may cause the activity of (2) inside the cell to increase or decrease. For example, when some intercellular chemical signals bind to receptor sites, a protein complex called (3) on the inner surface of the cell membrane is activated. GDP is replaced by (4) on the alpha subunit of the G proteins; this complex activates enzymes that produce intracellular chemical signals such as DAG, IP3, and (5) . Some intercellular chemical signals directly alter enzyme activity on the inner surface of the cell membrane, which can increase or decrease synthesis of intracellular chemical signals such as...
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