The Endocrine System chapter 16

Endocrine System: Definitions Endocrine – releasing substances into blood Endo = within or internal Contrast with Exocrine – releasing substances outside the body Hormone – a chemical that influences the function of a remote tissue (acts at a distance)

Endocrine System: Overview 9 glands in total Endocrine glands pituitary thyroid parathyroid adrenal pineal thymus Mixed glands produce both hormones and exocrine products pancreas gonads produce hormones and has neural functions hypothalamus

Pineal gland Hypothalamus Pituitary gland Thyroid gland Parathyroid glands (on dorsal aspect of thyroid gland) Thymus gland Adrenal glands Pancreas Ovary (female) Testis (male)

Hormones How they work Regulate the metabolic function of other cells Have lag times ranging from seconds to hours Tend to have prolonged effects Are classified as amino acid-based hormones, or steroids

2 M ain Types of Hormones Amino acid based Steroids Water-soluble Do not enter the cell e.g., insulin, norepinepherine, epinephrine Steroids Lipid soluble Act intracellularly and activate genes e.g., testosterone, estrogen, cortisol

Mechanism of Hormone Action Act on receptors in the plasma membrane Amino acid–based hormones e.g., epinephrine- binds to smooth muscle cells in blood vessels - causing contraction Direct gene activation Steroid hormones, thyroid hormones e.g., growth hormone - stimulates cells to increase in size and divide The precise response depends on the type of the target cell The ONLY tissue to respond is the Target Tissue (may be very specific (1) tissue, or multiple tissues)

Hormone Blood Concentrations Concentrations of circulating hormone reflect: Rate of release Speed of inactivation and removal from the body Hormones are removed from the blood by: Degrading enzymes The kidneys Liver enzyme systems

Hypothalamic Control Hypothalamus “releasing hormones” and “inhibiting hormones” tells of central control by brain GHRH (growth hormone RH) and GHIH (growth hormone IH) control GH from Ant. Pituitary PRH (prolactin RH) and PIH control PL from Ant. Pit. TRH  thyrotropin RH – release of TSH from Ant. Pit. CRH  corticotropin releasing hormone – release of hormones from adrenal cortex  Stress GnRH  gonadotropin RH – release of gonadal hormones from Ant. Pit.  LH and FSH

Pituitary (Hypophysis) Pituitary gland two-lobes secretes 9 major hormones Connected to the hypothamus by Posterior Lobe Neurohypophysis – neural tissue) and the infundibulum Receives, stores, and releases hormones from the hypothalamus Anterior Lobe Adenohypophysis – made up of glandular tissue Synthesizes and secretes a number of hormones

Pituitary (Hypophysis) Figure 16.6

Anterior Pituitary Hormones regulate other endocrine glands GH – growth hormone TSH – thyroid stimulating hormone ACTH – adrenocorticotrophic hormone FSH – follicle stimulating hormone LH – luteinizing hormone PRL - prolactin (latter 3 are called gonadotropins)

Growth Hormone (GH) Underproduction in children  dwarfism Overproduction in children  gigantism Overproduction in adults  acromegaly

Posterior Pituitary Hormones stores antidiuretic hormone (ADH) and oxytocin ADH and oxytocin are synthesized in the hypothalamus Oxytocin stimulates smooth muscle contraction in breasts and uterus “cuddle hormone” Both are amino acid based Receptor location?

Pancreas both exocrine and endocrine cells, Acinar cells  enzyme-rich juice used for digestion (exocrine product) Pancreatic islets (islets of Langerhans) produce hormones (endocrine products) The islets contain two major cell types: Alpha () cells that produce glucagon Beta () cells that produce insulin Class 05

Regulation of Blood Glucose Levels hyperglycemic  glucagon  glucose uptake hypoglycemic  insulin  glucose release Figure 16.18

Diabetes Mellitus (DM) Results from hyposecretion or hypoactivity of insulin The three cardinal signs of DM are: Polyuria – huge urine output Polydipsia – excessive thirst Polyphagia – excessive hunger and food consumption

Thyroid Gland thyroid hormone calcitonin metabolism, BP, growth T3 (10x) T4 calcitonin response to rising blood calcium – inhibit gut absorption and kidney reabsorption of Ca++

Thyroid Disorders Hypothyroidism Thyroid gland defect, inadequate TSH, lack of iodine Low metabolic rate, feeling chilled Goiter formation ( if cause is lack of iodine) Cretinism = Hypothyroidism in infants Stunted growth, low mentality can be prevented by hormone replacement therapy

Grave’s Disease Hyperthyroidism Autoimmune disease- body attacks and stimulates the thyroid cells - increased thyroid hormone High BMR, Weight loss, Increased heart rate, Protrusion of the eyeballs, goiter Treated by surgical removal of the thyroid gland

Parathyroid Glands PTH (parathormone) response to falling calcium in blood – promotes gut absorption and kidney reabsorption of Ca++ Question: what two hormones regulate calcium in blood?

Adrenal (Suprarenal) Glands Adrenal glands cope with stressful events Structurally and functionally, they are two glands in one Adrenal cortex – glandular tissue Adrenal medulla – neural tissue that acts as part of the SNS

Adrenal Cortex Hormones Aldosterone - dehydration causes kidney to reabsorb Na+  reabsorb water stimulated by angiotensin (remember Renin) Cortisol - stress increases blood glucose levels & reduces edema of tissues prolonged high levels  changes in neural and circulatory function, depressed bone/cartilage growth, suppressed immune response

Adrenal Cortex Hormones Androgens (masculinizing hormones) most important is testosterone the onset of puberty secondary sex characteristics sex drive in females testosterone can be converted to estrogen in females after menopause

Disorder Addison’s disease Cushings disease Hyposecretion of the adrenal cortex Deficiency in cortisol and aldosterone Low BP Hypoglycemia Cushings disease Hypersecretion of adrenal cortex (tumor of the adrenal cortex) Hyperglycemia “buffalo hump” (fat on upper back)

Adrenal Medulla secretes the catecholamines epinephrine norepinephrine “Fight or Flight” secretion causes: blood glucose levels to rise blood vessels to constrict faster heart rate blood diversion to brain, heart, and skeletal muscle

Adrenal Medulla Epinephrine is the more potent stimulator of the heart and metabolic activities Norepinephrine is more influential on peripheral vasoconstriction and blood pressure

Stress and the Adrenal Gland Figure 16.16