Chapter 13 Endocrine System Endocrine glands are ductless Exocrine glands have ducts

Endocrine Glands Paracrine secretions Endocrine glands act locally release hormones hormones travel through blood to target cells Paracrine secretions act locally affect only neighboring cells Autocrine secretions affect only the secreting cell

Comparison of Nervous System and Endocrine System Neurons release neurotransmitters into a synapse, affecting postsynaptic cells Glands release hormones into the bloodstream Only target cells of hormone responds

Comparison of Nervous System and Endocrine System

Major Endocrine Glands

Chemistry of Hormones Nonsteroid Hormones amines proteins peptides glycoproteins most hormones Steroid or Steroid-Like Hormones sex hormones adrenal cortex hormones

Types of Hormones

Structural Formulas of Hormones

Actions of Steroid Hormones hormone crosses membranes hormone combines with receptor in nucleus synthesis of mRNA activated mRNA enters cytoplasm to direct synthesis of protein

Actions of Steroid Hormones

Actions of Nonsteroid Hormones hormone binds to receptor on cell membrane adenylate cyclase activated ATP converted to cAMP cAMP promotes a series of reactions leading to cellular changes

Actions of Nonsteroid Hormones

Prostaglandins paracrine substances act locally very potent in small amounts regulate cellular responses to hormones can activate or inhibit adenylate cyclase controls cAMP production alters cell’s response to hormones wide variety of functions

Control of Hormonal Secretions primarily controlled by negative feedback mechanism

Negative Feedback

Major Endocrine Glands

Pituitary Gland Two distinct portions anterior pituitary (adenohypophysis) posterior pituitary (neurohypophysis)

Pituitary Gland Control Hypothalamic releasing hormones stimulate cells of anterior pituitary to release hormones Nerve impulses from hypothalamus stimulate nerve endings in the posterior pituitary gland to release hormones

Hypothalamic Hormones

Hormones of the Pituitary Gland

Thyroid Gland

Thyroid Gland Hormones

Disorders of the Thyroid Gland

Disorders of the Thyroid Gland Graves Disease Hyperthyroidism Cretinism Infantile hypothyroidism

Parathyroid Glands

Parathyroid Hormone

Parathyroid Hormone Mechanism by which PTH promotes calcium absorption in the intestine

Disorders of the Parathyroid Glands

Adrenal Glands

Hormones of the Adrenal Medulla

Hormones of the Adrenal Cortex

Hormones of the Adrenal Cortex

Hormones of the Adrenal Cortex

Pancreas

Hormones of the Pancreatic Islets

Insulin and Glucagon Insulin and glucagon function together to stabilize blood glucose concentrations

Other Endocrine Glands Pineal Gland secretes melatonin regulates circadian rhythms Thymus Gland secretes thymosins promotes development of certain lymphocytes important in role of immunity

Other Endocrine Glands Reproductive ovaries produce estrogens and progesterone testes produce testosterone placenta produces estrogens, progesterone, and gonadotropins

Stress Types of Stress physical stress psychological stress

Responses to Stress

Life-Span Changes endocrine glands decrease in size muscular strength decreases as GH levels decrease ADH levels increase due to slower break down in liver and kidneys calcitonin levels decrease; increase risk of osteoporosis PTH level changes contribute to risk of osteoporosis insulin resistance may develop changes in melatonin secretion affect the body clock thymosin production declines increasing risk of infections

Clinical Application Growth Hormone Ups and Downs Gigantism - hypersecretion of GH in children Acromegaly – hypersecretion of GH in adults Dwarfism – hyposecretion of GH in children Figure shows oversecretion of GH in adulthood as changes occur in the same person at ages (a) nine, (b) sixteen, (c) thirty-three, and (4) fifty-two