Chapter 20 Endocrine System Endocrine glands transmit signals

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Chapter 20 Endocrine System

Chapter 20 Endocrine System

 • Endocrine glands transmit signals through blood stream to cells far away •

• Endocrine glands transmit signals through blood stream to cells far away • Different from nervous system; Neuron can affect only cells it contacts Nerve signal Neurotransmitter Fig. 20. 1 Endocrine gland Hormone Blood Target cells (a) Nervous system (b) Endocrine system

Fig. 20. 2 Major endocrine glands Pituitary gland Pineal gland Thyroid gland Organs containing

Fig. 20. 2 Major endocrine glands Pituitary gland Pineal gland Thyroid gland Organs containing endocrine cells Hypothalamus Thymus Heart Kidney Gastrointestinal (GI) tract Pancreatic islets Parathyroid glands Adrenal glands

Fig. 20. 4 Hypothalamus The hypothalamus produces regulatory hormones that either stimulate or inhibit

Fig. 20. 4 Hypothalamus The hypothalamus produces regulatory hormones that either stimulate or inhibit anterior pituitary hormone secretion. Anterior pituitary The hypothalamus produces two hormones (antidiuretic hormone and oxytocin) that are stored in and released from the posterior pituitary. Posterior pituitary

Adrenal cortex Adrenal glucocorticoids • Adrenal cortex secretes three types of steroid hormones •

Adrenal cortex Adrenal glucocorticoids • Adrenal cortex secretes three types of steroid hormones • Aldosterone (aka mineralocorticoid) • Glucocorticoids, including cortisol • Increase plasma glucose concentrations • Sex hormones, including estrogens, progesterone, androgens • DHEA (dietary supplement) converted to testosterone Kidney

Growth hormone Hypothalamus • Released by anterior pituitary throughout life • Anabolic • Required

Growth hormone Hypothalamus • Released by anterior pituitary throughout life • Anabolic • Required for growth in childhood • Combined with thyroid, insulin, sex hormones in some cases • In adults, GH stimulates release of insulin-like growth factors (IGF) • Stimulate bone and soft tissue growth Anterior pituitary Posterior pituitary

Growth hormone pathologies • In childhood, lack of GH leads to dwarfism with proportional

Growth hormone pathologies • In childhood, lack of GH leads to dwarfism with proportional body • (one of many possible causes of dwarfism)

Growth hormone pathologies • Excessive GH leads to acromegaly • Long jaw, coarse facial

Growth hormone pathologies • Excessive GH leads to acromegaly • Long jaw, coarse facial features, excessive height

Thyroid • In adults: • Increase oxygen consumption in tissues • Modulate metabolism of

Thyroid • In adults: • Increase oxygen consumption in tissues • Modulate metabolism of proteins, carbohydrates, and fat • In children Larynx Thyroid gland • Necessary for expression of growth hormone • Necessary for development of nervous system Trachea

Fig. 20. 11 Hypothalamus secretes thyrotropin-releasing hormone (TRH), which acts on the anterior pituitary.

Fig. 20. 11 Hypothalamus secretes thyrotropin-releasing hormone (TRH), which acts on the anterior pituitary. 2 Anterior pituitary releases thyroidstimulating hormone (TSH). stimulatory inhibitory Negative feedback inhibition TRH 5 Secretion of TRH by the hypothalamus is inhibited. TH prevents the formation of TSH in anterior pituitary TSH Anterior pituitary Target organs in body TH 4 Target cells increase metabolic activities. 3 Thyroid gland releases thyroid hormone (TH).

Hyperthyroidism • Elevated TSH causes enlargement of thyroid gland = goiter • Increases oxygen

Hyperthyroidism • Elevated TSH causes enlargement of thyroid gland = goiter • Increases oxygen consumption and metabolic heat production • Causes warm, sweaty skin; intolerance to heat • Protein catabolism causes weak muscles • Weight loss • Hyperexcitable reflexes • Insomnia, irritability, psychosis • Rapid heartbeat

Hyperthyroidism • Graves’ disease • Body produces antibodies that mimic TSH • Thyroid overstimulated

Hyperthyroidism • Graves’ disease • Body produces antibodies that mimic TSH • Thyroid overstimulated • May cause exophthalmos (bulging eyes) • Caused by enlargement of tissues around eyes Marty Feldman

Parathyroid gland • Regulates calcium levels in the blood • vital for muscle contractions

Parathyroid gland • Regulates calcium levels in the blood • vital for muscle contractions

Fig. 20. 15 Body of pancreas Pancreas • Located behind stomach Pancreatic ducts Tail

Fig. 20. 15 Body of pancreas Pancreas • Located behind stomach Pancreatic ducts Tail of pancreas Major duodenal papilla Duodenum of small intestine Spleen Head of pancreas

Fig. 20. 15 Pancreas • Acinar cells produce digestive juices (not endocrine) • Pancreatic

Fig. 20. 15 Pancreas • Acinar cells produce digestive juices (not endocrine) • Pancreatic islets are clusters of endocrine cells Pancreatic acinus Alpha cell Blood capillary Pancreatic islet cells Alpha cell Beta cell Delta cell F cell Pancreatic islet

Fig. 20. 15 Pancreas • Alpha cells secrete glucagon when blood glucose is low

Fig. 20. 15 Pancreas • Alpha cells secrete glucagon when blood glucose is low • Beta cells secrete insulin when blood glucose is high • Delta cells and F cells affect digestion and release of insulin and glucagon Pancreatic acinus Alpha cell Blood capillary Pancreatic islet cells Alpha cell Beta cell Delta cell F cell Pancreatic islet