Lecture Human anatomy and physiology - Chapter 16: The endocrine system (part a). The objectives of this chapter are to: Indicate important differences between hormonal and neural controls of body functioning; list the major endocrine organs, and describe their body locations; distinguish between hormones, paracrines, and autocrines;. | 16 The Endocrine System: Part A Endocrine System: Overview Acts with the nervous system to coordinate and integrate the activity of body cells Influences metabolic activities by means of hormones transported in the blood Responses occur more slowly but tend to last longer than those of the nervous system Endocrine glands: pituitary, thyroid, parathyroid, adrenal, and pineal glands Endocrine System: Overview Some organs produce both hormones and exocrine products (., pancreas and gonads) The hypothalamus has both neural and endocrine functions Other tissues and organs that produce hormones include adipose cells, thymus, cells in the walls of the small intestine, stomach, kidneys, and heart Figure Pineal gland Hypothalamus Pituitary gland Parathyroid glands (on dorsal aspect of thyroid gland) Thymus Thyroid gland Adrenal glands Pancreas Ovary (female) Testis (male) Chemical Messengers Hormones: long-distance chemical signals that travel in the blood or lymph Autocrines: chemicals that exert effects on the same cells that secrete them Paracrines: locally acting chemicals that affect cells other than those that secrete them Autocrines and paracrines are local chemical messengers and will not be considered part of the endocrine system Chemistry of Hormones Two main classes 1. Amino acid-based hormones Amines, thyroxine, peptides, and proteins 2. Steroids Synthesized from cholesterol Gonadal and adrenocortical hormones Mechanisms of Hormone Action Hormone action on target cells Alter plasma membrane permeability of membrane potential by opening or closing ion channels Stimulate synthesis of proteins or regulatory molecules Activate or deactivate enzyme systems Induce secretory activity Stimulate mitosis Mechanisms of Hormone Action Two mechanisms, depending on their chemical nature Water-soluble hormones (all amino acid–based hormones except thyroid hormone) Cannot enter the target cells Act on plasma membrane receptors Coupled by G proteins to intracellular . | 16 The Endocrine System: Part A Endocrine System: Overview Acts with the nervous system to coordinate and integrate the activity of body cells Influences metabolic activities by means of hormones transported in the blood Responses occur more slowly but tend to last longer than those of the nervous system Endocrine glands: pituitary, thyroid, parathyroid, adrenal, and pineal glands Endocrine System: Overview Some organs produce both hormones and exocrine products (., pancreas and gonads) The hypothalamus has both neural and endocrine functions Other tissues and organs that produce hormones include adipose cells, thymus, cells in the walls of the small intestine, stomach, kidneys, and heart Figure Pineal gland Hypothalamus Pituitary gland Parathyroid glands (on dorsal aspect of thyroid gland) Thymus Thyroid gland Adrenal glands Pancreas Ovary (female) Testis (male) Chemical Messengers Hormones: long-distance chemical signals that travel in the blood or lymph Autocrines: .
