Condensed Endocrine - HAPS Anatomy & Physiology PDF

HAPS Anatomy & Physiology LOs: Endocrine Part 1  Compare and contrast how the nervous and endocrine systems control body functions, the anatomical pathways by which the signals reach their targets, what determines the target of the pathway, the speed of the target response(s), the dura...

HAPS Anatomy & Physiology LOs: Endocrine Part 1  Compare and contrast how the nervous and endocrine systems control body functions, the anatomical pathways by which the signals reach their targets, what determines the target of the pathway, the speed of the target response(s), the duration of the response.  Relate the terms hormone, endocrine gland, endocrine tissue and target cells.  Compare and contrast the structure and transport of protein and steroid hormones as well as the locations of their target receptors.  Describe the possible cellular mechanisms of signal transduction resulting from hormone:receptor binding (signaling cascade vs transcription factor).  Describe and give example of each of the three types of stimuli controlling hormone release (humoral, neural, and hormonal).  Review a simple endocrine pathway in which the response is the negative feedback signal (review parathyroid hormone (bone unit), introduce insulin (digestive).  The Endocrine System Communication/Control System – Fills in gaps in the other communication system- the Nervous System – Produces, secretes, and transports hormones Endocrine Glands/Tissues – Hypothalamus, Pituitary Gland – Thyroid – Thymus – Adrenals – Adipose Endocrine Organs in Other Body Systems – Digestive Pancreas, Stomach, Duodenum – Reproductive Gonads (testes, ovaries), Placenta – Bone Parathyroid Nervous vs Endocrine System Nervous Endocrine – Monitors specific – Widespread Need receptors cells Anatomical limits – Communication (chemical; via blood) – Communication Paracrine/Autocrine (local) (electrical; via Endocrine (global) nerves) – Slower long-term Direct processes Synaptic Growth/Development – Fast, short-term Reproduction processes Reflexes  Hormones Chemical signals produced by endocrine glands that provide instruction Travel through the blood stream Exert their effects on cells with specific receptors – Usually regulate protein synthesis Produced in small quantities, but have an amplified effect Types of hormones: – Amino acid/Peptide-based, water soluble – Steroid-based, lipid soluble Peptide/Amino Acid Hormones Water Soluble- Hydrophilic Free floating hormones that travel through the bloodstream and diffuse through capillary walls Interact with surface receptors on the plasma membrane of target cells Amplified via secondary messengers because they can’t cross the plasma membrane by themselves Examples: Insulin and Oxytocin Second Messenger Systems Intracellular signaling molecules help relay signals from receptors on the cell surface to target molecules inside the cell Hormone binds to receptor  signaling cascade  amplification of signal Two common systems – Cyclic adenosine monophosphate (cAMP) – Diacylglycerol & Inositol triphosphate (IP3)  Steroid-based Hormones Lipid Soluble- Hydrophobic Bound hormones that need help traveling through the blood stream and bind to hydrophilic transport proteins (albumin or globulins) Bond breaks when hormone reaches target cells and hormones enter the cell and activate receptors inside the target (nuclear receptors) Act as transcription factors and interact directly with DNA to either increase or decrease the transcription of certain genes  Specificity and Affinity Hormones bind to receptors, based on their shape- lock and key mechanism Receptors are specific, but not 100% exclusive – Examples: Estrogen receptors (ER)s can bind 3 types of biological estrogen Androgen Receptors (AR)s can bind testosterone and dihydrotestosterone The binding affinity (fit of lock and key) will vary, and usually translates to variation in strength of hormone signal Estradiol (100%) Estriol (10%) Estrone (1%)  Sensitivity Up-regulation Down-regulation – Increases # of – Reduces # of receptors receptors – Greater sensitivity – Less sensitive to to hormone hormone – E.g. Oxytocin – E.g. Insulin receptors during receptors during childbirth diabetes  Degradation and Excretion Degraded by enzymes in target cell Most removed from blood by enzyme systems in the kidney and liver Excreted in Urine Rate of degradation referred to as “Half-Life” – Peptide (hydrophilic) » Short half life » Enzymes in blood/liver » Filtered in kidney – Lipid/Steroid (hydrophobic) » Long half life » Protected by protein carrier  Hormone Regulation All hormones are tightly regulated by negative feedback. 1. Humeral Self regulated or regulated by other factors Blood glucose-pancreas, Ca2+ - parathyroid 2. Neural Neuroglandular junctions Adrenal medulla 3. Hormonal Many hormones are regulated by the hypothalamic/pituitary axis- requires tropic hormones Sex, thyroid, adrenal etc.  Humoral Stimuli Humoral Stimulus Changing blood levels of ions Hormone release caused by altered levels of certain critical ions or nutrients. and nutrients directly Capillary (low Ca2+ stimulate secretion of in blood) hormones Thyroid gland (posterior view) Example: Blood Ca2+ Parathyroid glands – Declining blood [Ca2+ ]  parathyroid glands to secrete parathyroid hormone – PTH causes [Ca2+ ] rise Parathyroid glands and stimulus is removed PTH Example: Blood Glucose – Increased blood glucose is Stimulus: Low concentration of Ca2+ in capillary blood. reduced by insulin signaling Response: Parathyroid glands secrete parathyroid hormone (PTH), which increases blood Ca2+.  Blood Calcium Levels: Parathyroid Gland Parathyroid glands are embedded in posterior surface of thyroid gland Release parathyroid hormone (PTH) when calcium levels are too low PTH increases calcium concentration in the blood Target organs include: – Bone Stimulates osteoclasts Inhibits osteoblasts – Kidney Stimulates reabsorption of calcium – Intestines Stimulates absorption of calcium from diet  Blood Glucose Levels: Pancreas Pancreas endocrine function – Endocrine cells found in Islets of Langerhans Alpha Cells – Glucagon released when “glucose is gone” – Regulates glucose release from glucose stores Beta Cells – Insulin released in response to increased glucose – Regulate glucose storage Delta – Somatostatin (growth inhibiting hormone) – Inhibits insulin and glucagon – Slows digestive system to increase absorption (protein)  Blood Glucose Levels: Pancreas Secretes hormones in response to changes in blood glucose – Low glucose: Alpha cells stimulated Target cells release energy – High glucose: Beta cells stimulated Target cells store energy Diabetes results from a dysregulation of this system – 95% of Type II cases result from over nutrition, obesity, lack of exercise  Neural Stimuli Sympathetic pre- Neural Stimulus Hormone release caused ganglionic by neural input. CNS (spinal cord) neurons synapse directly with adrenal medulla to secrete Preganglionic norepinephrine, sympathetic epinephrine fibers during a stress Medulla of response adrenal gland This happens at Capillary the neuroglandular Stimulus: Action potentials in preganglionic sympathetic fibers to adrenal medulla. junction. Response: Adrenal medulla cells secrete epinephrine and norepinephrine.  Hormonal Stimuli Tropic hormones Hormonal Stimulus Hormone release caused by another stimulate other hormone (a tropic hormone). Hypothalamus endocrine organs to release hormones End product is part of Anterior negative feedback loop pituitary gland Examples: – Hypothalamic-pituitary- Thyroid gland Adrenal Gonad cortex (Testis) target axes HPT (hypothalamus- pituitary-thyroid) HPA (hypothalamus- pituitary-adrenal) Stimulus: Hormones from hypothalamus. Response: Anterior pituitary gland secretes HPO (hypothalamus- hormones that stimulate other endocrine pituitary-ovarian) glands to secrete hormones.  HAPS Anatomy & Physiology LOs  Endocrine Part 2 Describe the locations and the anatomical relationships of the hypothalamus, anterior pituitary, and posterior pituitary, including the hypothalamic-hypophyseal portal system.  Compare and contrast negative feedback for hypothalamic-anterior pituitary- peripheral endocrine gland pathways to negative feedback for most simple endocrine pathways.  Describe major hormones secreted by the anterior pituitary (TSH, FSH, LH, ACTH, their control pathways, and their primary target(s) and effects.  Explain the role of hypothalamic neurohormones (regulatory hormones; TRH, GnRH, CRH) in the release of anterior pituitary hormones.  Identify the two hormones produced by the hypothalamus that are stored in the posterior pituitary, and the hormones’ primary targets and effects.  Explain the role of the hypothalamus in the release of hormones from the posterior pituitary.  Describe the anatomy of the thyroid gland, its location, the major hormones secreted, the control pathway(s) for hormone secretion, and the hormones’ primary targets and effects.  Describe the anatomy of the adrenal cortex, its location, the major hormones secreted, the control pathway(s) for hormone secretion, and the hormones’ primary targets and effects  Given a factor or situation (e.g., lack of iodine in the diet; anabolic steroid abuse), predict the changes that could occur in the endocrine system and the consequences of those changes (i.e., trophic hormone production, and secretion pathway inhibition).  Hypothalamus- Pituitary Hypothalamus – Regulates body temp, thirst, hunger, sleep, stress response, aggression, and sexual behavior Pituitary Gland- Anterior Lobe – Hypothalamus releases hormones to activate anterior pituitary gland via hypophyseal portal circulation – Highest level of endocrine control in tropic hormone pathways Example GnRH Pituitary Gland Posterior Lobe – Hypothalamus activates neurons (nerve cells) extending to posterior pituitary to release neurohormones Example: Oxytocin Adrenal Medulla – Hypothalamus exerts control over adrenal medulla (via sympathetic pathways)  The Master Gland- Hypophysis Anterior Pituitary (adenohypophysis) – Under hormonal control by the hypothalamus – Indirect release of hormones vis tropic hormone pathways Posterior Pituitary (neurohypophysis) – Under neural control by the hypothalamus – Direct release of hormones  Figure 18-9 Pituitary Hormones and Their Targets Hypothalamus KEY TO PITUITARY HORMONES: Indirect Control through Release Direct Release ACTH Adrenocorticotropic hormone of Regulatory Hormones of Hormones TSH Thyroid-stimulating hormone Regulatory hormones are released Sensory Osmoreceptor GH Growth hormone into the hypophyseal portal system stimulation stimulation PRL Prolactin for delivery to the anterior lobe of FSH Follicle-stimulating hormone the pituitary gland LH Luteinizing hormone MSH Melanoctye-stimulating hormon ADH Antidiuretic hormone OXT Oxytocin Posterior lobe Anterior lobe of of pituitary gland pituitary gland ADH Adrenal ACTH gland TSH GH Kidneys OXT Males: Smooth Epinephrine and Liver MSH muscle in ductus norepinephrine Thyroid PRL FSH LH deferens and gland prostate gland Somatomedins Females: Uterine smooth muscle and mammary glands Glucocorticoids (cortisol, Melanocytes (uncertain corticosterone) significance in healthy Why we adults) Bone, muscle, Ovaries other tissues Mammary Testes of female of male Thyroid glands call the hormones (T3, T4) Inhibin Testosterone Estrogen Progesterone Inhibin pituitary master! Posterior Pituitary Hormones Released in response to neural stimulation from the hypothalamus – Neuron stretches from hypothalamus to posterior pituitary – Instead of neurotransmitter release, a hormone is released 1. Paraventricular Nuclei Hormone – Oxytocin-“Bonding” hormone – Target tissues Prostate (Males) Uterus (Females) – Released during Orgasm Lactation Childbirth 2. Supraoptic Nucleus Hormone – Antidiuretic Hormone (ADH; Vasopressin) – Target tissues Kidneys Blood vessels – Released to help retain water in the body and increase BP Anterior Pituitary Hormones The anterior pituitary contains the hypophyseal portal network for releasing tropic hormones via hypothalamic-pituitary-target axes Hypothalamus releases releasing hormones to act of the anterior pituitary – Example: TRH Anterior Pituitary releases stimulating hormones to act on the endocrine organ – Example: TSH Endocrine organs release their own hormones which have influence the target cells and bind to their receptors Hypothalamus and Pituitary Gland also have receptors to complete the negative feedback loop Hypothalamus-Pituitary Common Tropic Pathway  Hypothalamus-Pituitary- Thyroid Pathway 1 1. Hypothalamus releases thyroid – (-) feedback releasing hormone (TRH) which 6 inhibition activates TRH receptors on anterior pituitary 2. Anterior Pituitary Gland releases + thyroid stimulating hormone – 4 5 (TSH) which activates receptors on thyroid 2 + 3. Thyroid releases thyroid hormones 4. Thyroid hormones (T3 and T4) influence target cells to increase metabolism (cells make energy 3 and heat) + 5. Thyroid hormones inhibit the release of TSH Stimulatory effect + 6. Thyroid hormones inhibit the Inhibitory effect release of TRH –  Thyroid Gland Anatomy: – Lies anterior to the trachea and inferior to thyroid cartilage (Adam’s Apple) – Two lobes connected by an isthmus – Follicles lined by cuboidal epithelial cells with a hollow center where TH (T3 and T4) is stored Physiology – Many tissues contain receptors for TH – Regulates metabolism Calorigenic Effect – Calor = heat – Thyroid hormone acts to increase cellular activity and increase ATP production – Thyroid hormone synthesized from Tyrosine and Iodine – Iodine is the limiting factor  Thyroid Disease Overactive thyroid (Hyperthyroidism/Grave’s Disease) – Goiters – Anxiety – Jitteriness – Heat intolerance – Exophthalmoses Treatments – Surgical removal – Ablation Radioactive iodine – Anti-thyroid drugs Hypothyroidism – Lethargy – Weight gain – Cold intolerance – Depression Treatment – Synthetic hormone  Adrenal Glands Located superior to kidneys Two Parts: Medulla and Cortex The medulla functions more like a postganglionic sympathetic neuron Neuron like Synthesizes and releases (nor)epinephrine aka (nor)adrenaline Fight or flight response The cortex functions like a true endocrine organ Adrenal Cortex Endocrine Function Under pituitary control Releases several corticosteroid hormones 3 Layers- each layer releases a different hormone – Zona glomerulosa (outer layer) Mineralocorticoid (aldosterone) – Zona fasciculata (middle layer) Glucocorticoid Hormones (cortisol) – Zona reticularis (inner layer) Secondary source of sex hormones (DHEA) Adrenal Cortex Hormones – Zona glomerulosa (outer layer) Mineralocorticoid (aldosterone) Regulates salt and water balance in the body Triggered by low blood pressure, low blood sodium levels – Zona fasciculata (middle layer) Glucocorticoid Hormones (cortisol) Promotes the breakdown of proteins and lipids to generate glucose to provide energy in response to stress Reduces inflammation and suppresses immune activity – Zona reticularis (inner layer) Secondary source of sex hormones (DHEA) contribute to the development of secondary sexual characteristics and influence libido  Figure 18-9 Pituitary Hormones and Their Targets (Part 1 of 2) Hypothalamus KEY TO HORMONES: Direct Control Indirect Control through Release ACTH Adrenocorticotropic hormone by Nervous of Regulatory Hormones CRH Corticotropin releasing hormone System Regulatory hormones are released into the hypophyseal portal system for delivery to the anterior lobe of the pituitary gland CRH Anterior lobe of Adrenal pituitary gland medulla Adrenal ACTH gland Adrenal cortex Epinephrine and norepinephrine Under pituitary control Adrenocorticotropic Glucocorticoids (cortisol, hormone corticosterone) Adrenal Hormone Imbalances Addison’s symptoms Fainting and low blood pressure – Are hormones too high or too low? » Too low! – Which ones are driving this problem? » Cortisol and Aldosterone Cushing’s symptoms Stress response Weight gain/moon face Water retention – Are hormones too high or too low? » Too high! – Which ones are driving this problem? » Cortisol Anabolic steroid abuse – Similar side effects as Cushing’s – Also liver, testicular, bone damage Hypothalamus-Pituitary Sex Hormone Tropic Pathway