Endocrinology PDF - Anatomy & Physiology PHAS5001

Anatomy & physiology PHAS5001 Endocrine system Faye Staniforth (PA-R) Learning outcomes Why do we have an endocrine system? What are hormones and what do they do? What are the main organs that make up the endocrine system? What are the functions of these organs ? How can we start to...

Anatomy & physiology PHAS5001 Endocrine system Faye Staniforth (PA-R) Learning outcomes Why do we have an endocrine system? What are hormones and what do they do? What are the main organs that make up the endocrine system? What are the functions of these organs ? How can we start to relate this to disease processes? What do you already know? https://create.kahoot.it/v2/share/end ocrine-quiz/7a6305eb-cce0-4c32-a2c e-13dcb035087f Endocrine system - function Overall function of the endocrine system is to maintain homeostasis Chemical messages –hormones, enable cells to communicate and achieve homeostasis Homeostasis : to maintain a stable internal state for optimal functioning  Endocrine system -function Short term Long term Blood pressure Growth pH of blood Reproduction Respiration – Metabolism respiratory drive depending how much oxygen is needed  Hormones A hormone is released in response to a stimulus/signal The action of the hormone restores equilibrium directly or indirectly  Hormone Activity Hormones affect only specific target tissues with specific receptors Water soluble hormones have receptors on cell surface Lipid soluble hormones have intracellular receptors - because of lipid cell membrane hence the lipid soluble hormones can pass through membrane Receptors constantly synthesized and broken Positive and negative feedback – example: negative is increase of blood sugar levels and positive is regulating this.  Hormones Ways cells communicate using hormones : Endocrine – transmitted by the circulatory system (distant) – by blood Paracrine – produced by endocrine tissue and transmitted in extracellular fluid (local) – locally in fluid only Autocrine – act on the same cell Neuroendocrine – secreted from nerve cells image from : https://yaledailynews.com/blog/2018/ 02/13/study-shows-how-cell-types- communicate/ Classes of hormones : Polypeptides – cannot pass through cell membranes (water soluble) Steroids – Can cross the cell membrane (lipid soluble) Hormone types – Circulating – circulate in blood throughout body (e.g. insulin) – Local hormones – act locally Paracrine – act on neighboring cells Autocrine – act on the same cell that secreted them (e.g interleukin-1)  Mechanisms of Hormone Action Lipid-soluble hormones bind to receptors inside target cells Water-soluble hormones bind to receptors on the plasma membrane Activates second messenger system Amplification of original small signal Endocrine system image from :https://www.rn.c om/clinical-insights/endocrine Endocrine system image from :https://www.rn.c om/clinical-insights/endocrine Hypothalamic-pituitary axis Considered the central regulatory component of the endocrine system - communicates with AP,PP because of the closeness Hypothalamus is sensitive to neural and hormonal stimuli The hypothalamus integrates these stimuli and sends signals to the pituitary  Hypothalamus Location: the base of the forebrain ( diencephalon) Structure: pituitary stalk which is continuous with the posterior pituitary gland. - has a network of anterior capillaries so continues link Functions: receives inputs from the circulation (temp , BM, hormones ) and neuronal inputs (autonomic and emotional). Based on these inputs hormones are secreted, which target the anterior or posterior pituitary. Blood supply: superior hypophyseal artery , hypophyseal portal vessels to the anterior pituitary (high hormones concentration), drained by the cavernous sinus Image from : https://www.the scienceofpsychotherapy.com/ Image from : https://teachme anatomy.info/neuroanatomy/s  Anterior Pituitary Location – lies in the sella turnica. The optic chiasma lies directly superior (pituitary gland tumours can cause visual changes due to compression) Function – release hormones after receiving stimulus from hypothalamus. Hormones act on other endocrine organs. Blood supply – superior hypophyseal artery, hypophyseal portal vessels from the hypothalamus , drained by the cavernous sinus (hormones enter circulation)  Posterior pituitary Location – posterior to anterior pituitary Structure – connected to the hypothalamus by the pituitary stalk Function – release ADH (acts on the collecting ducts of the kidney) and oxytocin Blood supply – inferior hypophyseal artery. Drained by the cavernous sinus (hormones enter circulation )  Example Hypothalamu Anterior Low Thyroid s - Thyrotrophin pituatry hormones (T4 , - releasing TSH( thyroid T3) hormones stimulating (TRH) hormone) Hypothalamus Posterior pituitary Anterior pituitary GHRH ADH GH GHRIH Oxytocin TSH CRH ACTH GnRH LH TRH FSH PRF PRL Dopamine Small peptides Small peptides Large peptides and (Except dopamine) glycopeptides  Thyroid gland Location - anterior to the trachea on the lower aspect of the neck Structure - butterfly shaped, two lobes 5cm long , connected by the isthmus. Attached to the trachea. (when patient swallows the thyroid gland moves upwards) Function – releases calcitonin (calcium homeostasis), T3 and T4 which regulate the metabolism of most of the cells. Iodine store (iodine is needed to make thyroid hormones) thyroglobin store( used for thyroid hormone synthesis Regulated by – the anterior pituitary gland (TSH) Blood supply - superior and inferior thyroid arteries (thyroid ima artery supplying the isthmus in some people), drained by the superior and middle thyroid vein, into the internal jugular vein and the inferior thyroid veins into the brachiocephalic vein. Not enough T3 and T4 due to – disease ,Cold , pregnancy (oestrogen) , low t3 t4 , adrenaline T4 is converted to T3 which only T3 will be fed to tissues If theres too much T3 this will send negative feedback to stop/decrease this production  Actions of Thyroid Hormones: Increase basal metabolic rate Increase body temperature (calorigenic effect) Increase the use of glucose and fatty acids Stimulate lipolysis Regulate development and growth of nervous tissue and bones Disorders of the thyroid TSH high TSH low T3 low T3 high T4 low image from :https://www.pint T4 high erest.co.uk/pin/16325617382  Parathyroid Located – one pair on the posterior surface of each lobe of the thyroid gland(total 4) (number can vary 2-6) Structure – 5mm in diameter , chief cells, oxyphil cells and adipocytes Function - calcium and phosphate homeostasis Regulated by – negative feedback , calcium levels Blood supply – inferior thyroid arteries  Adrenal glands Location -Paired retroperitoneal glands situated over the superior pole of each kidney Structure- Right gland is pyramidal in shape, contrasting with the semi-lunar shape of left gland. Separated into medulla and cortex Function- Secrete steroid and catecholam ine hormones directly into blood Regulated by – adrenal cortex – pituitary gland (ACTH) ,adrenal medulla – sympathetic nervous system  cortex -glucocorticoids – in response to stress (cortisol) -mineralcorticoids- regulate blood volume (aldosterone) -Androgens (sex hormone) medulla -catecholamines -adrenaline and noradrenaline  Blood supply - Superior adrenal artery – arises from inferior phrenic artery - Middle adrenal artery – arises from abdominal aorta - Inferior adrenal artery – arises from renal arteries - Right and left adrenal veins drain the glands. Right adrenal vein drains into inferior vena cava, whereas left adrenal vein drains into left renal vein  principal mineralocorticoid Aldosterone: It regulates the homeostasis of 2 mineral ions: K+ and Na+  regulation of blood pressure enin-angiotensin-aldosterone pathway Renin-angiotensin-aldosterone pathway -Stimuli: dehydration, haemorrhage, Na+ deficiency -Decrease blood volume  decrease blood pressure -Stimulation of kidney cells to secrete RENIN  converts ANGIOTENSINOGEN into ANGIOTENSIN I -ANGIOTENSIN I is converted into ANGIOTENSIN II by ACE( ACE Inhibitors) -ANGIOTENSIN II (ARB) stimulates the adrenal cortex to secrete ALDOSTERONE Glucocortic - Cortisol the most oids: abundant. Released in response to stress They have the following effects: 1. Protein breakdown: increase the rate of protein breakdown in the in muscle fibres liberating AA for synthesis new proteins 2. Glucose formation: liver cells convert AA or lactic acid into glucose 3.Lipolysis: breakdown of triglycerides and release fatty acids from adipose tissue for energy 4.Resistance to stress: providing substrates for energy production make the body ready to react 5.Anti-inflammatory effects: inhibits inflammatory response by supressing the immune function (used in treatment of inflammatory Catecholamines Epinephrine/adrenaline 80% Norepinephrine/noradrenaline 20% Fight or flight response - Increases HR - More blood to heart, liver and muscles - Dilates airways  PANCREAS Endocrine- into blood stream (Islets of Langerhans) Exocrine – via ducts (acini) gland  Pancreas Location – retroperiotoneal gland , posterior and inferior to the stomach Structure – islets of langerhans, containing 4 types of cells Function – endocrine and exocrine function Blood supply -body and the tail are supplied by branches of the splenic artery. - The uncinate and head are supplied by the creaticoduodenal artery.  Endocrine Each pancreatic islet includes 4 types of hormone-secreting cells: Alpha or α cells17% cells GLUCAGON = raises BG Beta or β cells 70% cells INSULIN = lowers BG SOMATOSTATIN = Delta or δ cells 7% cells inhibits both glucagon and insulin release F or pp cells The remaining PANCREATIC POLYPEPTIDE = cells inhibits somatostatin and digestive enzymes  Exercise – match the condition to the gland Addisons Adrenal gland Hypothyroidism Thyroid gland Cushings disease Pituitary Diabetes Hypothalamus Conns disease Pancreas Graves disease Acromegaly – too much growth hormone  Answers Condition Gland Addisons Adrenal insufficiency Hypothyroidism Thyroid gland , low T3 and T4 Cushing disease Adrenal – raised cortisol ( or too much steroid medication) Diabetes Pancreas Conns disease Adrenal – too much aldosterone Graves disease Thyroid – autoimmune , raised T3 and T4 Acromegaly Pituitary – too much growth hormone  Final Quiz https://create.kahoot.it/v2/share/end- of-endocrinology-quiz/a02471e4-782 7-4a18-9c5a-59f560d47f38  Further reading Crash course in Edocrinology – O'Neil Murphy (if interested)