Bio 257 Day 23 Today’s topic  Ch 10 Endocrine System

Objectives: Define endocrine gland, hormone and target tissue. Define endocrine gland, hormone and target tissue. List the chemical types of hormones List the chemical types of hormones Characterize control of hormone Characterize control of hormone secretions. secretions.

Objectives: Describe the structure of the pituitary gland, thyroid gland, parathyroid glands, pancreas, and adrenal glands. Describe the structure of the pituitary gland, thyroid gland, parathyroid glands, pancreas, and adrenal glands.

List hormones, describe their actions and name the target tissues of the major endocrine glands. List hormones, describe their actions and name the target tissues of the major endocrine glands. Objectives:

Organs: –Endocrine glands = ductless glands, which secrete hormones into body fluids (blood)

Similarity and Differences b/w Nervous and Endocrine Systems control over organs it is in direct contact with indirectly affect many organs of the body at a distance by secreting chemicals into the blood

General Function of the Endocrine System : –Coordinates & regulates body systems to maintain homeostasis

Organs: –Hormone(s) = organic compound, that exerts specific effects on certain organs (target organs) at some distance away

Hormone receptors Sites on or in the target tissue (organ) to which a chemical (e.g. hormone) binds to similar to a lock-n-key.

Receptors Membrane-Bound Receptor Responses –Alter membrane permeability by directly opening or closing membrane channels –Activate G proteins that in turn can open or close membrane channels or activate enzymes that produce intracellular chemical signals (2 nd messenger) –Alter the activity of enzymes directly leading to an increase or decrease in the level of intracellular chemical signals or add phosphate groups to cellular proteins

Cytoplasm Polar hormone in blood ATP E receptor

Receptors Intracellular receptors: –Located in the cytoplasm or nuclei –Regulate the synthesis of specific messenger RNA molecules  Protein Synthesis

Lipid Soluble Hormone

Overview of Types of Chemical Signals Intracellular- produced in one part of a cell and travel to another part of the same cell and bind to either cytoplasmic or nuclear receptors. –Often produced at the level of the cell membrane

Overview of Types of Chemical Signals Intercellular chemical signals –Autocrine- released by cells and have a local effect on the same cell or cell type  eicosanoids released from smooth muscle and platelets lead to blood vessel dilation and platelet aggregation –Paracrine- released by cells that have effects on other cell types near the cells from which they are released (e.x. somatostatin inhibits release of insulin in the pancreas)

Overview of Types of Chemical Signals Intercellular chemical signals –Neuromodulators and neurotransmitters-secreted by nerve cells function in the nervous system –Pheromones-secreted into the environment may modify the behavior and physiology of other individuals (pheromones produced by humans not fully understood) –Hormones-secreted by endocrine glands into the circulatory system, transported and act on tissues distant from the site of release in a specific way Neurohormones-hormones secreted from cells of the nervous system

Localized chemical signal Hormone

Hormone Effects on Target Organs REGULATE: Growth Stress pH of body Reproduction system Use of food sources (metabolism) Water Balance Uterine contractions/milk release Heart rate and blood glucose control Immune system

Chemistry of Hormones 2 classes: – Synthesized from amino acids (AA) Proteins or peptides (insulin, ADH, oxytocin) Thyroid hormones derived from AA Tyrosine (throxine, triiodothyronine) Amines (catecholamines)  epinephrine and norepinephrine) –Epinephrine released from the adrenal medulla (ie (Endocrine fxn) –Norepinephrine released more from neurons (not much from adrenal medulla) –Synthesized from cholesterol Steroids (lipid-like)  cortisol, estrogen, testosterone

Mechanism of Hormone Action 1. Hormones are released on demand and determined by the body’s need 1. Hormones are released on demand and determined by the body’s need

2. Hormone’s principle action site is its target tissue or organ. 3. The target tissue contains specific contains specific receptors, which the hormone binds. receptors, which the hormone binds.

4. Hormones only affect those organs w/ the 4. Hormones only affect those organs w/ the specific target receptor specific target receptor

5. When a hormone binds to its target tissue receptor, a chain of events are produced that alter the target cell activities

Polar Hormone

Control of HormoneSecretions 3 Mechanisms control secretion of hormones  all use negative feedback 3 Mechanisms control secretion of hormones  all use negative feedback 1.Hypothalamus/anterior pituitary 2.Nervous system 3.Glands responding to changes in internal environment

How do hormones work? Negative feedback mechanisms –Effects of the hormone on the target gland are “fed back” to the endocrine gland which then decreases the secretion of that hormone

How do hormones work? Many work together = synergistic effects (synergism) Many work in opposition = antagonistic effects (antagonism) Hypersecretion = oversecretion of hormone Hyposecretion = under secretion of hormone

Pituitary Gland Sits in sella turcica Extends from hypothalamus Consist of 2 lobes (anterior lobe & posterior lobe)

Pituitary gland

Relationship of Hypothalamus to Pituitary gland

anterior lobe posterior lobe infundibulum

Posterior Pituitary

Hypothalamus/Posterior Pituitary 1.Neural stimulation of hypothalamic neurons 2.AP carried by axons from hypothalamus to posterior pituitary. The neuron terminal in the posterior pituitary stores hormones 3.AP cause the release of hormones from the axons into the circulatory sytem 4.The hormones pass through the circulatory system and influence the activity of their target tissue

Posterior Lobe of Pituitary Gland 2 hormones (peptide) 1.Oxytocin  stimulates contraction of uterine smooth muscle  Stimulates milk ejection or milk let-down from mammary glands –target: uterus & mammary glands

Posterior Lobe of Pituitary Gland 2 hormones (peptide) 2. ADH (antidiuretic hormone or vasopressin) = increases reabsorption of water by kidneys resulting in decreased urine output (ie less water lost as urine) target: kidneys

Anterior Pituitary

Anterior Pituitary Hormones MSH Melanocytes in skin

Anterior Lobe of Pituitary Gland Hormones are called tropic hormones 7 hormones

Anterior Lobe of Pituitary Gland 1. GH (growth hormone) –stimulates growth (increase in cell size & mitosis) by increasing protein synthesis –Increases breakdown of lipids  increase in free fatty acids –Increases blood glucose levels target: most body tissues,

Anterior Lobe of Pituitary Gland 2. TSH (thyroid stimulating hormone) –stimulates thyroid gland hormone secretions & growth target: thyroid gland

Regulation of Thyroid Hormone Secretion

Anterior Lobe of Pituitary Gland 3. ACTH (adrenocorticotropic hormone) –stimulates adrenal gland (cortex) secretions Glucocorticoids  cortisol target: adrenal cortex of adrenal gland

Regulation of Cortisol Secretion

Anterior Lobe of Pituitary Gland 4. Prolactin –stimulates milk production by mammary glands –prolongs progesterone secretion following ovulation/during pregnancy target: mammary glands/ovaries

Anterior Lobe Gonadotropins = hormones whose target organs are gonads 5. FSH (follicle-stimulating hormone)  stimulate the production of gametes (sperm cells & oocytes) & estrogen target:  ovaries  follicles in ovary  testis  seminiferous tubules

Anterior Lobe Gonadotropins 6. LH (luteinizing hormone)  stimulates the releases of egg (oocyte) from ovary (ovulation) and progesterone production in ovary.  testosterone production from testis target: ovaries & testis

Anterior Lobe 7. MSH (melanocyte stimulating hormone)  stimulates production of melanin by melanocytes  makes the skin darker

Pineal Gland Between cerebrum & cerebellum (epithalamus) 1 hormone: melatonin = regulates sleep wake cycles, produced at night. may prevent onset of puberty  higher amounts in pre- adolescence children

thyroidgland isthmus larynx trachea

Thyroid Gland Lateral to trachea & inferior to larynx (neck) 2 lobes connected by narrow band of tissue (isthmus) 3 hormones (thyroxine-T 4, triiodothyronine-T 3, & calcitonin)