versus Endocrine Nervous system
Nervous system performs short term crisis management Endocrine system regulates long term ongoing metabolic Endocrine communication is carried out by endocrine cells releasing hormones Alter metabolic activities of tissues and organs Target cells Paracrine communication involves chemical messengers between cells within one tissue
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Figure 18.1 The Endocrine System
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Figure 18.1
Figure 18.2 A Structural Classification of Hormones
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Figure 18.2
Hormones can be
Freely circulating Rapidly removed from bloodstream Bound to transport proteins
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Mechanisms of hormone action
Receptors for catecholamines, peptide hormones, eicosanoids are in the cell membranes of target cells Thyroid and steroid hormones cross the membrane and bind to receptors in the cytoplasm or nucleus
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Figure 18.3 G Proteins and Hormone Activity
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Figure 18.3
Figure 18.4 Hormone Effects on Gene Activity
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Figure 18.4
Figure 18.5 Three Methods of Hypothalamic Control over the Endocrine System
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Figure 18.5
Hypophysis
Releases nine important peptide hormones All nine bind to membrane receptors and use cyclic AMP as a second messenger
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Figure 18.6 The Anatomy and Orientation of the Pituitary Gland
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Figure 18.6a, b
The anterior lobe (adenohypophysis)
Subdivided into the pars distalis, pars intermedia and pars tuberalis At the median eminence, neurons release regulatory factors through fenestrated capillaries Releasing hormones Inhibiting hormones
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Figure 18.7 The Hypophyseal Portal System
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Figure 18.7
Figure 18.8 Feedback control of Endocrine Secretion
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Figure 18.8a
Figure 18.8 Feedback control of Endocrine Secretion
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Figure 18.8b
Hormones of the adenohypophysis
Thyroid stimulating hormone (TSH) Triggers the release of thyroid hormones Thyrotropin releasing hormone promotes the release of TSH Adrenocorticotropic hormone (ACTH) Stimulates the release of glucocorticoids by the adrenal gland Corticotrophin releasing hormone causes the secretion of ACTH
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Hormones of the adenohypophysis
Follicle stimulating hormone (FSH) Stimulates follicle development and estrogen secretion in females and sperm production in males Leutinizing hormone (LH) Causes ovulation and progestin production in females and androgen production in males Gonadotropin releasing hormone (GNRH) promotes the secretion of FSH and LH
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Hormones of the adenohypophysis
Prolactin (PH) Stimulates the development of mammary glands and milk production Growth hormone (GH or somatotropin) Stimulates cell growth and replication through release of somatomedins or IGF Growthhormone releasing hormone (GHRH) Growthhormone inhibiting hormone (GHIH)
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Melanocyte stimulating hormone (MSH)
May be secreted by the pars intermedia during fetal development, early childhood, pregnancy or certain diseases Stimulates melanocytes to produce melanin
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The posterior lobe of the pituitary gland (neurohypophysis)
Contains axons of hypothalamic nerves neurons of the supraoptic nucleus manufacture antidiuretic hormone (ADH) Decreases the amount of water lost at the kidneys Elevates blood pressure
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The posterior lobe of the pituitary gland (neurohypophysis)
Neurons of the paraventricular nucleus manufacture oxytocin Stimulates contractile cells in mammary glands Stimulates smooth muscle cells in uterus
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Figure 18.11 The Thyroid Gland
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Figure 18.11a
Figure 18.11 The Thyroid Gland
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Figure 18.11b, c
Thyroid follicles and thyroid hormones
Thyroid gland contains numerous follicles Release several hormones such as thyroxine (T4) and triiodothyronine (T3) Thyroid hormones end up attached to thyroid binding globulins (TBG) Some are attached to transthyretin or albumin
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Figure 18.12 The Thyroid Follicles
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Figure 18.12a
Figure 18.12 The Thyroid Follicles
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Figure 18.12b
Thyroid hormones
Held in storage Bound to mitochondria, thereby increasing ATP production Bound to receptors genes activating that control energy utilization Exert a calorigenic effect
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Cells of the thyroid gland
C cells produce calcitonin Helps regulate calcium concentration in body fluids
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Figure 18.14 The Parathyroid Glands
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Figure 18.14
Figure 18.15 The Homeostatic Regulation of Calcium Ion Concentrations
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Figure 18.15
Adrenal cortex
Manufactures steroid hormones (corticosteroids) Cortex divided into three layers Zona glomerulosa (produces mineralocorticoids) Zona fasciculate (produces glucocorticoids) Zona reticularis (produces androgens)
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Figure 18.16 The Adrenal Gland
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Figure 18.16
Adrenal medulla
Produces epinephrine (~75 80%) Produces norepinephrine (~2530%)
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Pineal gland
Contains pinealocytes Synthesize melatonin Suggested functions include inhibiting reproductive function, protecting against damage by free radicals, setting circadian rhythms
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The pancreatic islets
Clusters of endocrine cells within the pancreas called Islets of Langerhans or pancreatic islets Alpha cells secrete glucagons Beta cells secrete insulin Delta cells secrete GHIH F cells secrete pancreatic polypeptide
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Figure 18.18 The Endocrine Pancreas
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Figure 18.18a, b
Insulin and glucagon
Insulin lowers blood glucose by increasing the rate of glucose uptake and utilization Glucagon raises blood glucose by increasing the rates of glycogen breakdown and glucose manufacture by the liver
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Figure 18.19 The Regulation of Blood Glucose Concentrations
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Figure 18.19
The intestines
Produce hormones important to the coordination of digestive activities
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The kidneys
Produce calcitriol and erythropoietin (EPO) and the enzyme rennin Calcitriol = stimulates calcium and phosphate ion absorption along the digestive tract EPO stimulates red blood cell production by bone marrow Renin converts angiotensinogen to angiotensin I
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Angiotensin I converted to angiotensin II in the lungs
Stimulates adrenal production of aldosterone Stimulates pituitary gland release of ADH Promotes thirst Elevates blood pressure
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Figure 18.20 Endocrine Functions of the Kidneys
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Figure 18.20a
Figure 18.20 Endocrine Functions of the Kidneys
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Figure 18.20b
The heart
Specialized muscle ...