ENDOCRINE SYSTEM Review PETER REONISTO, MD MOORPARK COLLEGE

Nervous System vs. Endocrine System 3) Hormones travel more slowly than nerve impulses, the endocrine system tends to regulate slow processes such as growth and metabolism.

1. “Pure” endocrine organs Major Endocrine Organs Pineal gland Pituitary gland Thyroid gland Parathyroid gland Endocrine cells of the body contained in: Adrenal gland 1. “Pure” endocrine organs

Major Endocrine Organs Hypothalamus Endocrine cells of the body contained in: Thymus Pancreas 2. “Partly” endocrine organs Gonads

CLASSES OF HORMONES AMINO ACID-BASED Most hormones Proteins Modified amino acid peptides STEROIDS Lipid molecules derived from cholesterol Sex hormones Adrenal cortex hormones

CONTROL OF HORMONE SECRETION Humoral Neural Hormonal

CONTROL OF HORMONE SECRETION Humoral- influenced by plasma concentration of the substance. Low Ca2+ blood concentration Parathyroid gland Parathyroid gland Parathormone secretion Nephron, intestinal cells Action

CONTROL OF HORMONE SECRETION 2. Neural- SNS stimulation Preganglionic SNS fibers Adrenal medulla Medulla of adrenal gland Adrenaline secretion Body Actions: “Fight, flight, or fright” response

CONTROL OF HORMONE SECRETION 3. Hormonal-influenced by the amount of hormones in the plasma Releasing hormones Hypothalamus Releasing hormones Adenohypohysis Stimulating Hormones Thyroid gland Adrenal cortex Gonads (Testis) Thyroxine Cortisol Androgens Body Cortisol Androgens Increase Metabolic rate Anti-stress Sperm formation

MAJOR ENDOCRINE ORGAN PITUITARY GLAND

> Hypophyseal fossa PITUITARY GLAND Or, hypohysis Secretes at least 9 major hormones Location: > Hypophyseal fossa Depression in the Sella turcica of the Spenoid bone

ANATOMY: PITUITARY GLAND infundibulum

Anterior Pituitary Gland

Adenohypophysis Pars distalis Pars intermedia Pars tuberalis

Adenohypophysis Pars distalis Largest division Contains 5 different endocrine cells that make and secrete 7 different hormones

Pars distalis 5 CELL CLASSES: 1. Somatotrophic cell (most abundant) 2. Mammotrophic cells 3. Thyrotrophic cells 4. Corticotrophic cells 5. Gonadotrophic cells Growth Hormone (Somatotrophic Hormone / Somatotropin / GH) Growth of the entire body Prolactin (PRL) Breast milk production Thyroid Stimulating Hormone (TSH) Thyroid gland stimulation to release thyroid hormone Adrenocorticotropic Hormone (ACTH) Adrenal Cortex stimulation to release glucocorticoids Melanocyte Stimulating Hormone (MSH) Stimulates melanocytes to produce melanin pigment Follicle Stimulating Hormone (FSH) Gonads: maturation of sex cells; secretes sex hormones Gonadotropins Leutenizing Hormone (LH) Gonads: maturation of sex cells; secretes sex hormones

Pars distalis 5 CELL CLASSES: Growth Hormone (Somatotrophic Hormone / Somatotropin / GH) Growth of the entire body Act directly on non-endocrine target tissues Prolactin (PRL) Breast milk production M P G Thyroid Stimulating Hormone (TSH) Thyroid gland stimulation to release thyroid hormone Tropic Hormones - Regulate the secretion of hormones by other Endocrine glands Adrenocorticotropic Hormone (ACTH) Adrenal Cortex stimulation to release glucocorticoids F L A T Melanocyte Stimulating Hormone (MSH) Stimulates melanocytes to produce melanin pigment Follicle Stimulating Hormone (FSH) Gonads: maturation of sex cells; secretes sex hormones Leutenizing Hormone (LH) Gonads: maturation of sex cells; secretes sex hormones

HYPOTHALAMIC CONTROL OF THE ADENOHYPOPHYSIS Controlled by RELEASING HORMONES and INHIBITING HORMONES - Peripheral Endocrine gland Peripheral Endocrine gland Peripheral Endocrine gland Target cell Target cell

HYPOPHYSEAL PORTAL SYSTEM Hypothalamic neurons Releasing hormones are made in Hypothalamic neurons Primary capillary complex Releasing hormones are secreted at the neuron synapse To the primary capillary complex Releasing hormones goes to the Hypophyseal portal vein To the secondary capillary complex Secondary Capillary complex Releasing hormones leaves the plexus & attach to the adenohypophyseal cells Somatotropic Mammotropic Thyrotropic Corticotropic Gonatotropic

Posterior Pituitary Gland

Neurohypophysis 1. Median eminence 2. Infundibular stalk 3. Pars nervosa Median eminence Infundibular stalk Pars nervosa

NEUROHYPOPHYSIS HORMONE PRODUCTION Hormone produced at neuron cell bodies located at the SUPRAOPTIC and PARAVENTRICULAR nuclei of the Hypothalamus Hormones are transported along the axons (Hypothalamic-hypophyseal Tract) Upon stimulation, stored hormones are released in the capillary bed for distribution throughout the body Hormones are stored in dilated axon terminals called HERRING BODIES ADH Oxytocin

NEUROHYPOPHYSIS: Hormones CELL TYPE HORMONE TARGET/EFFECTS Neurons from supraoptic nucleus of hypothalamus Antidiuretic hormone (ADH, vasopressin) Stimulates kidneys (distal tubules and collecting tubules) to reclaim water from urine. Raises blood pressure by constricting peripheral arterioles when blood volume is low. Neurons from paraventricular nucleus of hypothalamus Oxytocin Initiates labor through uterine contraction Facilitates milk ejection from breast

MAJOR ENDOCRINE ORGAN THYROID GLAND

THYROID GLAND located in the anterior neck; on the trachea just inferior to the larynx

PARATHYROID GLAND Located at the posterior surface of the thyroid

PARATHORMONE FUNCTION: Increase blood Calcium level

ADRENAL GLAND ADRENAL CORTEX ADRENAL MEDULLA Mineralocorticoid Balance electrolyte Concentration (Na+/K+) --Inc Na+ Reabsorption --Inc K+ excretion --Inc water reabsorption Mineralocorticoid (Aldosterone) Glucocorticoid (Cortisol) Stress control Glucocorticoid (Cortisol) Produce sex hormone precursor (DHEA) ----Dehydroepiandrosterone---

ADRENAL MEDULLA: Hormones Simulate a “fight, fright, flight response”

PANCREAS

Other Endocrine Glands Pineal Gland secretes melatonin regulates circadian rhythms Thymus Gland secretes thymosins promotes development of certain lymphocytes important in role of immunity Reproductive ovaries produce estrogens and progesterone testes produce testosterone placenta produces estrogens, progesterone, and gonadotropins

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