CHAPTER 17
ENDOCRINE
PART I
OVERVIEW/PHYSIOLOGY
Has animations and will appear only in viewing in Slide Presentation Mode and playing each animation. Most animations will require the latest version of the Flash Player, which is available at http://get.adobe.com/flashplayer 17-1

Chapter 16 Objectives: Endocrine System

Endocrine System
• Overview
• Hypothalamus and Pituitary Gland
• Other Endocrine Glands
• Hormones and Their Actions
• Stress and Adaptation
• Eicosanoids and Paracrine Signaling
• Endocrine Disorders
17-3

Overview of Cell Communications
• internal communication is necessary for coordination of cell activities • four principal mechanisms of communication between cells
– gap junctions
• pores in cell membrane allow signaling molecules, nutrients, and electrolytes to move from cell to cell

– neurotransmitters
• released from neurons to travel across synaptic cleft to second cell – paracrine (local) hormones
• secreted into tissue fluids to affect nearby cells

– hormones
• chemical messengers that travel in the bloodstream to other tissues and organs
17-4

17-5

Endocrine System Components
• endocrine system - glands, tissues, and cells that secrete hormones • endocrinology – the study of this system and the diagnosis and treatment of its disorders
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

• endocrine glands – organs that are traditional sources of hormones
• hormones - chemical messengers that are transported by the bloodstream and stimulate physiological responses in cells of another tissue or organ, often a considerable distance away

Endocrine cells Target cells

Hormone in bloodstream (b) Endocrine system

Figure 17.2b

17-6

Endocrine Organs
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Pineal gland
Hypothalamus
Pituitary gland

Thyroid gland
Thymus

Adrenal gland
Pancreas
Parathyroid glands Posterior view Trachea

Gonads:
Ovary (female)
Testis (male)

Figure 17.1

• major organs of endocrine system

17-7

Comparison of Endocrine and
Exocrine Glands
• exocrine glands
– have ducts carry secretion to an epithelial surface or the mucosa of the digestive tract – ‘external secretions’
– extracellular effects (food digestion)

• endocrine glands
– no ducts
– contain dense, fenestrated capillary networks which allows easy uptake of hormones into bloodstream
– ‘internal secretions’
– intracellular effects such as altering target cell metabolism

• liver cells defy rigid classification – releases hormones, releases bile into ducts, releases albumin and bloodclotting factors into blood (not hormones)

17-8

Comparison of Nervous and Endocrine
Systems (Differences)
• both serve for internal communication
– nervous - both electrical and chemical
– endocrine - only chemical

• speed and persistence of response
– nervous - reacts quickly (1 - 10 msec), stops quickly
– endocrine - reacts slowly (hormone release in seconds or days), effect may continue for weeks

• adaptation to long-term stimuli
– nervous - response declines (adapts quickly)
– endocrine - response persists (adapts slowly)

• area of effect
– nervous - targeted and specific (one organ)
17-9
– endocrine - general, widespread effects (many organs)

Communication by the Nervous and Endocrine Systems
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Neurotransmitter

Nerve impulse

Neuron
Target cells
(a) Nervous system

Endocrine cells Target cells

Hormone in bloodstream (b) Endocrine system

Figure 17.2 a-b

17-10

Nervous and Endocrine Systems
(Similarities)
• several chemicals function as both hormones and neurotransmitters – norepinephrine, cholecystokinin, thyrotropin-releasing hormone, dopamine and antidiuretic hormone

• some hormones secreted by neuroendocrine cells
(neurons) that release their secretion into the bloodstream
– oxytocin and catecholamines

• both systems with overlapping