Prelims - Neurophysiology.pdf

)1 NEUROPHYSIOLOGY Organization of the Nervous...

)1 NEUROPHYSIOLOGY Organization of the Nervous System and Physiology of GRADING SYSTEM Synapses 5 Shifting Exam (30 pts) Post-Lab Quiz (15 pts) LECTURE Medical Correlations Continuation of Lecture SGDs Quizzes and Asynchronous Activities 15% 6 MAJOR PRELIM EXAMINATIONS Shifting and Long Examinations 20% 7 Sensory Physiology: Sensory physiology: Tactile Attendance 5% Receptors, Afferent Nerve and Positional Sensations FIbers, Pathway and Recitation 5% Cortex Moodle Lesson and Course Manual 15% 8 Post-Lec Quiz (15 pts) Sensory Physiology: Pain and Laboratory Experiment: Thermal Sensations Major Written Examination 40% General Sensations and Associated Medical TOTAL 100% COnditions LABORATORY 9 Post-Lec Quiz (15 pts) Continuation of Lecture Laboratory Conference Quizzes and Asynchronous Activities 20% 10 Shifting Exam (30 pts) Physiology of Vision Laboratory Experiment: Laboratory Conference Written Report and 35% Visual Reflexes, Tests, Documentation and Associated Medical Research Work Conditions Attendance 5% 11 Post-Lab Quiz (15pts) Physiology of the Vestibular Laboratory Conference System Major Written Examination 40% 12 MAJOR MIDTERM EXAMINATIONS TOTAL 100% 13 Laboratory Experiments: Cognition, Learning, LABORATORY CONFERENCE - ORAL REPORTING Tests for Hearing, Consciousness, and Memory Balance, Taste and Smell, and Associated Medical Groups Preparation Organization and Distribution 30% Conditions of Report 14 Post-Lec Quiz (15pts) Autonomic Nervous SYstem Individual Experiment Performance and Oral 50% Laboratory Conference Report 15 Post-Lec Quiz (15 pts) Motor Functions of the Spinal Peer Evaluation 5% Laboratory Experiment: Cord and Reflex Physiology Reflexes in Man Recitation and Student Critique 15% 16 Shifting Exam (30 pts) Motor Functions of the Cortex TOTAL 100% Laboratory Conference and Brainstem, Descending Pathways WK LABORATORY LECTURE 17 Pots-Lab Quiz (15 pts) Lecture Continuation Post-Lec Quiz (15 pts) 1 Course Orientation Intro to Endocrine Physiology 18 MAJOR FINAL EXAMINATIONS 2 FOUNDATION WEEK 3 Post-Lec Quiz (15 pts) Reproductive Physiology and Overview Endocrine Sexual Response Function 4 Bone Physiology Post-Lec Quiz (15 points) NEUROPHYSIOLOGY  )2 ○ Calcium ions sticks to the vesicles where acetylcholine is stored and the vesicles undergoing exocytosis ○ Acetylcholine in neurons - Inhibitory and Excitatory neurotransmitters The most common inhibitory neurotransmitter is the gamma amino butyric acid The most abundant excitatory neurotransmitter is the glutamate ENDOCRINE PHYSIOLOGY ○ Acts locally to control nerve cell functions Endocrine Hormone Nervous System vs. Endocrine System ○ Released by glands or specialized cells into the Nervous system controls the whole body, while endocrine circulating bloodstream system controls the major processes of the body ○ They influence the functions of cells at another location Mediator Molecules of the body ○ Neurotransmitters - acetylcholine between the Neuroendocrine Hormones neuromuscular junction secreted by the synaptic end ○ Secreted by neurons into the circulating blood bulbs, the alpha motor neurons innervated by the ○ Influence the function of cells at another location in the muscles. Its route is in the ECF, in the synaptic cleft body between the synapses and motor end plate ○ Adrenal Medulla - a clump of neurons within that, it ○ Endocrine Hormones - these are chemical route in synthesizes catecholamines, the norepi and epi the interstitial fluid, in the bloodstream ○ Hypothalamus - a neural organ or tissue secreting the Site of Mediator Action releasing and inhibiting hormones for the pituitary ○ Synapses - where neurotransmitters act. gland Acetylcholine will bind with the motor end plate at the Paracrines nicotinic motor end plate where beside it are sodium ○ Secreted by cells into the extracellular fluid channels ○ However, their site of actions are the nearby cells of ○ Far from the site of release - almost all tissues, different type, affecting cell of a different type cardiac, muscles, it is widespread. For the Pituitary ○ Clotting Factors and growth factors Gland, LH and FSH are released at the ovaries ○ Endothelial Cells - in the endothelial membrane of the Types of Target Cells blood vessels, tunica intima with a base and ○ Muscle fibers of the skeletal, cardiac, and smooth; endothelial layers. If lesion occurs, your endothelial glands of the smooth muscles; and other neurons cells secretes endothelin in the smooth muscle causing ○ Cells throughout the body as long as there is a receptor local vasoconstriction Time of Onset of Action Autocrines ○ Milliseconds due to the short distance ○ Secreted by cells into the extracellular fluid ○ Seconds to hours or days - it is long ○ However, it affects the function of the same cells that Duration of Action produced them by binding to cell surface receptors ○ Shorter because it travels in the synapses ○ Take note that your receptors require chemicals. If the ○ Longer due to its distance and concentration chemical binds to the receptor it changes the inside of the cells Exocrine Glands vs. Endocrine Glands ○ Seen in the immune system - T Lymphocytes excites Exocrine Glands itself and the other cells of the same type ○ These secretes products into ducts, it has a tube that Cytokines connects the glands in a hollow organ ○ Chemical messengers used in chemotaxis ○ Gallbladder has a hepatic duct connecting to the ○ Humihingi ng tulong yung cells for chemotaxis duodenum ○ Migration or attraction of cells in the site of lesion ○ Pancreas is both an endocrine and exocrine ○ These are peptides secreted by cells into the ECF Exocrine - the acini secretes the pancreatic ○ Can function as autocrines, paracrines, or endocrine digestive enzymes to the main and accessory hormones pancreatic duct ○ Secreted by the helper cells Endocrine Glands ○ Adipokines - cytokine hormone, the leptin produced by ○ No ducts, no tubes the adipocytes ○ All they need is circulation, they need a rich blood supply Chemical Structure and Synthesis of Hormones ○ Secretes products in the interstitial fluid and to the Three General Classes of Hormones bloodstream Proteins and Polypeptides ○ It should be vascularized - they need a good blood ○ Anterior and posterior pituitary hormones, pancreatic supply hormones, parathyroid hormones ○ Pancreas - Pancreatic Islets have blood vessels Steroids releasing insulin and glucagon to the bloodstream ○ They’re derived from fat, lipid, and cholesterol ○ The sterons and sterols Chemical Messengers ○ Lipid soluble can easily enter the cells that can Neurotransmitters influence the DNA and genes directly ○ Stored within your vesicles and is released by axon ○ Testosterone and estrogen, as well as cortisol terminals of neurons into the synaptic junctions Amino Acid Tyrosine Derivatives ○ Triggered by calcium ions then the action potential ○ Also lipid soluble, but are derived from the protein of causes the voltage gated calcium channels to open Tyrosine NEUROPHYSIOLOGY  )3 ○ Thyroxine and Triiodothyronine - T3 and T4 Concentration is required to control most metabolic functions. It only needs small concentration because hormones are very potent (meaning great effect) ○ High concentration = High Stimulus = High Effect Proteins and Polypeptides The rate of secretion is also very small because hormones Pituitary hormones, pancreatic hormones, parathyroid are very potent, it can even cause atrophy of an organ hormones In testes, due to high hormones, it will eventually stop Stored in the secretory vesicles until needed and are secreting hormones synthesized in the rough endoplasmic reticulum Synthetic steroid facilitates growth of blood vessels with a Ribosomes are the ones who make proteins small testes Secreted through exocytosis within your vesicles Stimulus is the increased calcium concentration due to Control of Secretion depolarization Negative Feedback Mechanism In the RER starts at the prehormones, when it passes ○ Prevents overactivity of hormone systems through the RER it becomes prohormones. Outside the ○ It ensures a proper level of hormone activity at the golgi apparatus becoming the hormones target tissue Peptide hormones are water soluble ○ Controlled variable controls the degree of activity of Carrier protein-receptor is inside target tissue Surface receptors are usually the case which can influence ○ For example, you trigger an organ, it secretes a the target cells through surface receptors since they cannot hormone, to stop the hormone secretion, it depends on easily pass through the cell membrane the concentration. The hormone itself will cause inhibition of the secretion of the endocrine gland Steroids ○ It acts on the effect of the organ Lipid hormones and steroid hormones are manufactured ○ It can lessen or negate the hormone causing the and secreted as they are needed change on that organ Derived or synthesized and has similar structure with cholesterol It is lipid soluble and it consists of three cyclohexyl rings and one cyclopentyl ring ○ They can easily enter and exit the cell without the need for carrier proteins ○ Receptors are inside the cell - organelle, nucleus, DNA or genes A large percentage will be cleared - destroyed and excreted as waste products It can also be “stored” - the hormone binds with plasma proteins (albumin). The steroid hormones when secreted are transported by plasma proteins. Through this, they are exported through blood If they are not used, they stay with your plasma proteins. That’s why your plasma proteins acts as a reservoir Large storage of cholesterol esters can be rapidly mobilized Positive Feedback Control for steroid synthesis ○ Surges of hormones occur as long as there is the Androgen Hormone from adrenal cortex is made and trigger or stimulus synthesized to become your estrogen ○ Best example is labor or parturition - the stretch of cervix is the stimulus to release oxytocin to promote the Amine Hormones contraction of the uterus. It won’t stop until the baby is Tyrosine is an amino acid out, once the cervix is relaxed Two Types ○ Oxytocin inhibits relaxin ○ Adrenal Medullary Hormones - epi and norepi ○ Biological action of the hormones causes additional ○ Thyroid Hormones secretion of the hormone Formed by the action of enzymes in the cytoplasmic compartment Your tyrosine is bound to a specific chemical or element. It is only inside the thyroid gland. Tyrosine is bound with iodine from the salt to become thyronine. Then depending on the thyronine bound - three becomes triiodothyronine ○ Three for T3 - Four for T4 They are also lipid soluble, especially your thyroid hormones Secretion, Transport, and Clearance of Hormones Each different hormones has its own characteristic onset and duration of action Depending on the stimulus and feedback NEUROPHYSIOLOGY  )4 Plasma Protein-Bound Hormones = Slower Clearance ○ They will do their function once they are released from the plasma proteins, and are not cleared Mechanisms of Action of Hormones - Steps Cyclical Variations Binding to a Specific Cell Receptor ○ It depends on many factors ○ Insulin receptors are present in muscles and bones ○ Periodic variation of hormone release ○ You don’t have insulin receptors in the brain because ○ Example is menstruation - cyclical, it depends on time it can utilize glucose directly You have a time where LH and FSH is high ○ Receptors Can Be Found causing the development of egg cells In or on the surface of the cell membrane Its peak happens at ovulation day Majority are protein and peptide hormones ○ Another example is the time of the day and catecholamines - water-soluble In the morning, cortisol levels are low, in the In the cell cytoplasm afternoon or at night, cortisol levels are high Lipid hormones, specifically the steroids ○ Influenced by In the cell nucleus Seasonal changes Lipid hormones, specifically the thyroid Stage of developmental changes triggered by a hormones sudden surge ○ Number of the receptors do not remain constant Emotions - it can be cyclical Down Regulation - happens due to too much ○ Superimposed on the negative and positive feedback concentration and if the hormones are not cleared control - it is more followed by the body than the easily positive and negative feedback control Inactivation of some receptor molecules Inactivation of some intracellular protein Transport of Hormones in Blood signaling molecules Water-Soluble Hormones Temporary sequestration of the receptor to ○ Protein and peptide hormones the inside of the cell, away from the site of ○ If it is secreted in the blood, it will dissolve in the plasma action hormones - temporary tinatago and transported to target tissues Destruction of receptors by lysosome ○ If they are released, they diffuse out of the capillaries Decrease production of receptors to the interstitial fluid and to the target cells Up Regulation - kabaliktaran ng down ○ Much faster clearance than lipid-soluble Activation of some receptor molecules Lipid-Soluble Hormones Activation of some intracellular protein ○ Steroid hormones and Amine Hormones signaling molecules ○ They will bind to your plasma proteins Temporarily available or open ○ Circulate in the blood being mainly bound to plasma Building up of receptors by lysosome proteins Increase production of receptors ○ Protein-bound hormones cannot easily diffuse across capillaries and gain access to the target cells because Down regulation of insulin receptors is caused by Type 2 it is still bound to the protein ○ The plasma proteins acts as the reservoir Diabetes. For example, you eat a lot of carbohydrates and eventually become glucose. Your liver decreases glucose by ○ Reservoir function storing it into glycogen. Your liver has its limit for the number Clearance of Hormones of glycogen. The excess glucose is converted to fats. Now, if the glucose is at its chronic level, the pancreas is stimulated Two factors that increase or decrease concentration of hormones in blood to release insulin to activate cells to accept glucose, since glucose cannot easily diffuse into your cell. Normally blood ○ Rate of hormone secretion ○ Rate of hormone removal glucose is decreased after meals. If it's chronic, the cells will Higher Concentration = Lower Metabolic Clearance Rate down regulate the insulin receptors. The insulin is still high, because insulin knows there is a high glucose in your blood. Water has high clearance rate but are very potent Hyperinsulinemia and Hyperglycemia, leading to Diabetes Intracellular signaling after the hormone-receptor activation ○ It will trigger an effect inside your cells Ways Hormones can be Cleared from the Blood ○ It can induce its effect or create another messenger Metabolic destruction by the tissues and cause a cascade of enzymatic reactions Binding with the tissues ○ Hormone + Receptor = Hormone-receptor complex Excretion by the liver into the bile ○ Types of Cell Receptors Excretion by the kidneys into the urine Ion Channel-Linked Receptors G Protein-Linked Receptors Degradation of hormones at the target cells through Enzyme-Linked Receptors enzymatic process to endocytosis of hormone-receptor Intracellular Receptors and Gene Activation complex Peptide Hormones and Catecholamines = Faster Ion Channel-Linked Receptor Clearance When your hormone binds with the receptor, their is ○ Due to their solubility to water opening or closing of one or more ion channels NEUROPHYSIOLOGY  )5 Example: The acetylcholine and norepinephrine ○ They combine in the postsynaptic membrane, changes Calcium-Calmodulin System occur in the receptor, the link will either open or close ○ Calcium ions enter the cell through G-Protein Linked Receptors Calcium voltage gated channels needing an action Gamma Beta Alpha are the G Proteins potential When your hormone binds with the receptors it activates the Hormone + receptors, an example of an ion linked G protein, a part of g proteins separates from it channel One of the component of the trimeric gene protein ○ Calcium + Calmodulin = Inhibition or activation of separates and activate another site from the cell protein kinase ○ Example: Activate myosin light chain kinase Enzyme-Linked Receptor Acts on myosin of smooth muscle for contraction When your hormone binds with a receptor it activates or inactivates an enzyme Hormones that Act on Genes - Steroid Hormones Example: Activating other intracellular enzyme pathway Can easily enter cells and majority of its receptor is located inside of cells Intracellular Receptors and Gene Activation Their aim is to induce protein synthesis - the final What if the receptor is inside the cell? destination The hormone should be lipid soluble When the hormone goes inside your cell, they will bind with Once the hormone with the intracellular receptor, you now the receptor inside the cell or cytoplasm or it can enter have a changes in your DNA directly into the nucleus Activates a regulator sequence of DNA - once activated It binds to a specific site on a DNA strand and undergo produces mRNA transcription and create mRNA and it diffuses into the ○ If something is binded to the regulator sequence, it cytoplasm to undergo protein synthesis creates mRNA The new proteins will induce the effect of the hormone This influences your DNA expression Thyroid Hormones have receptors inside the DNA Hormone Interactions - Factors that Determine the ○ Ribosome translates the message and undergoes Responsiveness of the Target Cell to a Hormone protein synthesis Hormone concentration in blood ○ It is now transported to the ER then to the golgi ○ The greater the concentration, increase in apparatus responsiveness Many different tissues have identical intracellular receptors ○ Applies in hypersecretion or hyperproduction disorders ○ One hormone can influence many kinds of tissues ○ Hyperthyroidism - increase temperature and ○ Thyroid hormones can influence almost all metabolism, with diarrhea Can activate a gene response only if appropriate or specific ○ Gigantism gene regulatory protein is present Beyond 7-8ft, excessive growth and development ○ Many of this is specific It becomes dangerous, because you have closed Responses of different tissues to a hormone growth plates but you still continue to grow ○ Specificity of receptors to a hormone Due to diabetogenic effect, you experience obesity ○ Expression of genes that the receptor regulates The abundance of target cells’ hormone receptors ○ No matter what the concentration, it should also be Second Messenger Mechanisms enough Hormone binds with the receptor, activating it. Instead of a ○ Diabetes Mellitus Type II - lesser insulin receptors, an direct effect, you create another messenger increase in blood glucose, pancreas increases insulin Adenyl Cyclase-Camp causing hyperinsulinemia ○ When the hormone bind switch the receptor, alpha G ○ Insulinemia - pangingitim ng balat protein goes away and binds with the adenyl cyclase ○ Hyperglycemia - malapot na dugo, blocking small ○ It will utilize ATP to create cAMP, the second blood vessels messenger ○ When you have diabetes, you have neuropathy, you ○ cAMP activates everything cAMP-dependent protein have numbness - you can’t feel your wounds kinase which proceeds to the phosphorylation of If infections reaches your bone, you have to specific cell proteins undergo amputation ○ Resulting to a biomechanical reactions The influences exerted by other hormones ○ Presence of cAMP inside the cells activates a cascade ○ You need other hormone to induce another effect of enzymes ○ Permissive, synergistic, and antagonistic effect Few molecules of activated adenylyl cyclase can cause many enzymes to be activated and so forth Permissive Effect The slightest amount of hormones initiates A second hormone that may do the following cascading activating force for entire cell Strengthens the effect of the first hormone ○ If the hormone receptor is coupled with inhibitory G Increases the number of receptors for the first hormone, proteins results to an inhibition of Adenylyl Cyclase increasing sensitivity then its effect Cell Membrane Phospholipids Promotes synthesis of an enzyme required for the ○ The one that acts as the secondary is the phospholipid expression of the first hormone’s effects C, this enzyme catalyzes breakdowns of phospholipids The effect of the first hormone is strengthened Synergistic Effect NEUROPHYSIOLOGY  )6 The effects of two or more hormones combined to create a Posterior Lobe or Neurohypophysis greater effect Occur due to the hormones activate pathways that lead to Control of Secretion by the Hypothalamus the formation of the same type of secondary messenger Part of the diencephalon containing several nuclei They add up to each other Anterior Pituitary Gland Both of the hormones may have similar effects or have ○ Controlled by five releasing and two inhibiting different effects but the end product is the same. However, hormones produced and released by the arcuate it has a stronger effect nucleus of the hypothalamus Posterior Pituitary Gland Antagonistic Effect ○ Controlled by neural control Contradicting effect ○ It came from the hypothalamus specifically from One hormone opposes the actions of another hormone paraventricular nuclei and preoptic nuclei Happens in negative feedback ○ Acts as a storage area Insulin and somatostatin, or insulin and glucagon ○ Response from the impulses from the two nucleic ○ They are not contradicting to each other, but are just whenever oxytocin or ADH is needed different of effects Paraventricualr contains osmoreceptors, Occur due to the activation of pathways that cause opposite detecting the amount of solutes in your blood - cellular responses or one hormone decrease the number of high solutes in blood, low blood volume, stimulates receptors for the other hormone your posterior pituitary gland, releasing ADH to increase blood volume Control of Hormone Secretion Hormone release occurs in short bursts Negative Feedback Mechanism ○ When a hormone is released, it is not continuous You stop releasing ADH when the blood level is normal, outburst, it squirts at intervals osmoreceptors are deactivated How do they increase concentration if the release occurs in It also deactivates neural impulses a short burst? The most common for all endocrine system ○ You increase the frequency of the burst ○ Endocrine glands will release its hormone in more Hypothalamic Releasing and Inhibiting Hormones frequent bursts when stimulated, increasing Releasing hormones concentration in blood ○ Thyrotropin-releasing Hormone Regulation of Secretion - in order to maintain homeostasis, ○ Gonadotropin-releasing Hormone in order to prevent overproduction or underproduction ○ Corticotropin-releasing Hormone ○ Growth-releasing Hormone Ways of Hormone Regulation Inhibiting Hormones Signals from the nervous system ○ Growth-inhibiting Hormone ○ Your endocrine system is still influence by the nervous ○ Prolactin-inhibiting Hormone system, especially your hypothalamus and pituitary Releasing and inhibiting hormones came from the gland, or your limbic system hypothalamus controlling your anterior pituitary gland, Chemical changes in the blood specifically from arcuate nuclei ○ The amount of ions, acidosis or alkalosis ○ Hypoxemia increases erythropoietin When hypothalamus is removed, prolactin-inhibiting Other hormones Most common is still the negative feedback mechanism hormone increases its secretion. Galactorrhea is the excessive milk production, the effect of removing the Hypothalamus. Gynecomastia is the breast development of males. HYPOTHALAMUS AND PITUITARY GLAND Cells and Hormones of the Anterior Pituitary Gland Somatotrophs - somatotropin or growth hormones Hypothalamus and Pituitary Gland Corticotropin - adrenocorticotropic hormone, melanocyte- Pituitary gland has two lobes - anterior and posterior stimulating hormone Anterior Pituitary Gland or Adenohypophysis Thyrotropes - thyroid-stimulating hormone Posterior Pituitary Gland ro Neurohypophysis Gonadotropes - follicle-stimulating hormone, luteinizing Posterior pituitary gland is a direct continuation of hormone hypothalamus via infundibulum or stalk, while the Anterior Lactotropes or Mammotropes - prolactin Pituitary Gland is the true endocrine gland The blood vessel system that surround both posterior and Anterior Pituitary Gland Hormones anterior pituitary gland 1. Growth Hormone or Somatotropin ○ More so connected from hypothalamus down to 2. Thyroid-Stimulating Hormone Adenohypophysis or Anterior Pituitary Gland 3. Follicle- Stimulating Hormone ○ Hypophyseal Portal System 4. Luteinizing Hormone Once hypothalamus releases inhibitory hormones it goes to 5. Adrenocorticotropic Hormone the hypophyseal portal system 6. Prolactin Posterior is control by the neural connections 7. Melanocyte-Stimulating hormone 8. B-Lipoprotein Pituitary Glands Growth Hormone or Somatotropin Anterior Lobe or Adenohypophysis NEUROPHYSIOLOGY  )7 Target tissue is liver and other tissues in the body, the cells that are capable of growth Posterior Pituitary Gland Hormones Function for the liver, muscle, cartilage, bone and other 1. Antidiuretic Hormone or Vasopressin tissues to synthesize and secrete insulin-like growth factors 2. Oxytocin or IGFs IGFs facilitates the growth, promoting growth of body Antidiuretic Hormone ADH or Vasopressin tissues, not the growth hormone itself Target tissue are the kidneys, sudoriferous or sweat glands, ○ Growth hormone is water-soluble, it is easily wash out and arterioles so it needs the IGFs to prolong the effect of GH Function ○ Glucose uptake is used for growth and development ○ Decrease urine volume Enhance lipolysis and decrease glucose uptake - ○ Decrease water loss through perspiration breakdown of fats from adipose tissues to create fatty acids ○ Raises blood pressure by constricting arterioles ○ This gives the ketogenic effect Dehydration, loss of blood volume, pain and stress ○ Glucose increase with the decrease glucose uptake activates ADH GH is stimulated by your Growth-releasing hormone, Helps in the constriction of arterioles hypoglycemia caused by physical activity, decrease fatty acid, and deep sleep Oxytocin ○ REM sleep - rapid eye movement, nananaginip, the Target tissue uterus, mammary glands, also the brain first stages of sleep or before you wake up; inhibits the Function release of GH ○ Stimulates contraction of smooth muscles cells of the ○ Deep Sleep - wala kang malay talaga, stimulates GH uterus during childbirth Inhibits GH secretion - REM sleep, emotional deprivation, ○ Stimulates contraction of myoepithelial cells in low thyroid levels, negative feedback mechanism mammary glands to cause milk ejection Gigantism happens before puberty, Acromegaly is the The suckling reflex of the baby stimulates the release of thickening if bones and enlargement of head and face oxytocin Thyroid-Stimulating Hormone TSH Thyroid Gland Target Tissue is the thyroid gland Located inferior to the larynx or around the thyroid cartilage Function is to stimulate synthesis and secretion of thyroid Composed of right and left lateral lobes, connected by an hormones by thyroid gland isthmus Inhibition is the negative feedback mechanism 50% have the Pyramidal Lobe Produces T3 and T4, and Calcitonin Follicle-Stimulating Hormone FSH It contains Thyroid Follicles surrounding the follicular cells Target tissue is the ovary and testis ○ Spherical cells that composes the thyroid glands Function Follicular Cells ○ Females - initiates the development of oocytes and ○ Makes up the walls of the thyroid follicles, surround by includes ovarian secretion of estrogen basement membrane ○ Males - stimulates testes to produce sperm Parafollicular Cells ○ Produces calcitonin hormones Luteinizing Hormone LH Target tissue is the ovary and testis Thyroid Gland Hormones Function is for 1. Triiodothyronine and Thyroxine ○ Females - stimulate secretion of estrogen and 2. Calcitonin progesterone, ovulation, and formation of corpus luteum Triiodothyronine and Thyroxine - T3 and T4 ○ Males - production of testosterone from leydig cells T3 is more potent and the one who binds with the receptor (counterpart of leydig are mara cells, the one that T4 removes one compound, becoming T3 to enter a cell surrounds the egg cells while developing) Target cells are almost all body cells It acts on target cells by inducing gene transcription and Adrenocorticotropic Hormone ACTH protein synthesis Targets the adrenal cortex Functions Function is to stimulates the adrenal cortex to release ○ Increase BMR - rate of metabolism at rest at asleep glucocorticoids, as well as the release of androgens ○ Enhance action of catecholamines ○ Regulate development and growth of nervous tissues Prolactin and bones Target tissue are mammary glands ○ In childhood, we have high levels of thyroid hormones Function in females - stimulates mammary glands to and GH produce milk It is important for the development of nervous system Melanocyte-Stimulating Hormone MSH When deprived, there is a mental retardation, as Target tissue is the brain and skin well as retardation of bones - they look old, No exact role is known in humans Cretinism When present in excess is to darken the skin and protect the skin for UV rays Calcitonin B-Lipoprotein Target cells are osteoclast cells Target tissue is the brain, no exact role is known NEUROPHYSIOLOGY  )8 It decreases the level of calcium of blood by inhibiting the activity of osteoclast cells for bone resorption If they are inhibited, osteoblast cells for bone building decreased calcium in blood The amount of calcitonin produced by the thyroid hormone is insignificant ○ The one who release calcium are the Parathyroid Glands Parathyroid Glands Very small round masses partially embedded in the posterior surface of the lateral lobes Contains two kinds of epithelial cells ○ Chief Cells - secretes parathyroid hormones ○ Oxyphil Cells - unknown function Parathyroid Hormone PTH Target cells are the osteoclasts cells Glucocorticoids It increases the calcium levels Main hormones In blood calcium levels, it increases here ○ Cortisol is the most abundant - the stress hormone, ○ It is decreased by calcitonin due to increase bone higher in the afternoon resorption and deposition, because osteoclasts are ○ Corticosterone inhibited calcitonin is secreted in small amounts ○ Cortisone Increase blood calcium levels by stimulating osteoclasts for Target Cells or Tissues bone resorption releasing calcium and phosphate in your ○ Muscle fibers to release amino acids in blood blood to increase calcium ○ Liver cells release glucose in blood Target cells are also kidneys ○ Adipose tissue - glycolysis to increase fatty acids in Function blood ○ Increase the number and activity of osteoclasts ○ Blood vessels facilitates vasoconstriction ○ Decrease levels of HPO4 in blood, increase Ca ions ○ White blood cells suppresses or inhibit its action and Mg ions levels in blood Functions HPO4 increases secretion to urine; Ca and Mg ○ Protein breakdown, Glucose formation, and Lipolysis decreases secretion in urine Increases amino acids, glucose, and fatty acids in Blood levels of HPO4 decreases with increase the blood to increase the sources of energy secretion, Ca and Mg increases with decrease ○ Resistance to stress secretion Increase blood glucose levels for stressful ○ Promote formation of calcitriol - the active form of situations Vitamin D ○ Anti-inflammatory effects Allows absorption of Ca and Mg in the GI tract Anything from glucocorticoids can suppress your HPO4 in the GI tract is the tagasundo of Calcium, immune system no calcitriol, no calcium - causing rickets in Corticosteroids decrease rate of inflammation children, and osteomalacia in adults ○ Depression of immune responses Mabilis ka magkasakit when stressed Adrenal Glands Adverse effects of corticosteroids is obesity Located in your kidney Three layers - capsule, adrenal cortex, and adrenal medulla Adrenal Cortex Hormones Adrenal medulla contains chromatin cells Main Hormone is the Dehydroepiandrosterone (DHEA), a Adrenal Cortex Zones and Hormones major glucocorticoids ○ Glomerulosa - mineralocorticoids Target cells or tissues are the brain or ovaries ○ Fasciculata - glucocorticoids A precursor of testosterone ○ Reticulata - androgens Functions ○ Males Mineralocorticoids Insignificant effects due to normal production of Main Hormones testosterone by the testes ○ Aldosterone - major mineralocorticoid Development of male organ Target Cells or Tissues ○ Females ○ Renal Tubules of Kidneys Promotes libido or sex drive by amygdala and ○ Sweat Glands other primitive areas in the brain Function Converted into estrogen ○ Regulates homeostasis of Na and K ions Source of estrogen after menopause - estrogen ○ Helps adjust blood pressure and blood volume have protective effects to osteoblasts and an ○ Promotes excretion of H ions in the urine inhibitory effect to osteoclasts Once menopause happens, risk to osteoporosis increases RAAS System ○ Both males and females Stimulate axillary and pubic hair growth NEUROPHYSIOLOGY  )9 Prepubertal growth spurt Ovaries - estrogens (estradiol and estrogen), progesterone, inhibin, and relaxin Adrenal Medulla Testes - testosterone Inner region of adrenal gland Modified sympathetic ganglion of the ANS because it lacks Estrogen and Progesterone axons, no nervous connection Target cells are most cells in the body Its function is to add on the sympathetic function Function with FSH and LH Chromaffin Cells are innervated by Sympathetic ○ Regulate female reproductive cycle preganglionic neurons ○ Maintain pregnancy ○ Prepare mammary glands for lactation Adrenal Medulla Hormones ○ Promote development of secondary female Norepinephrine and Epinephrine characteristics Target cells are the blood vessels and most tissues Goes through the bloodstream Relaxin Function is to enhance effects of sympathetic division of Target cells are uterus or cervix and pelvis autonomic nervous system during stress Function Activates fight or flight response ○ Increase flexibility of pubic symphysis during pregnancy Pancreas ○ Helps dilate uterine cervix during labor and delivery Both an endocrine and exocrine gland Located in the curve of the duodenum and consists of a Inhibin head, a body, and a tail Target cells are pituitary gland 99% of the pancreas are arranged in clusters Function ○ Acini - produce digestive enzymes to flow into the GI ○ Inhibits secretion of follicle-stimulating hormone tract through ducts Cells of the Islets of Langerhans and its Hormones Testosterone ○ Alpha Cell - glucagon increases Target cells are most cells in the body ○ Beta Cell - insulin increase uptake of glucose Function Insulin is a polypeptide, water soluble ○ Stimulates descent of testes before birth ○ Delta Cell - somatostatin inhibits insulin and glucagon ○ Regulates sperm production ○ F Cell - pancreatic polypeptide inhibits delta ○ Promotes development and maintenance of male secondary sex characteristics Glucagon Target cells are liver cells Pineal Gland Function increases blood glucose by Small pinecone-shaped body that projects posteriorly from ○ Glycogenolysis the posterior end of the roof of the 3rd ventricle ○ Gluconeogenesis - glucose from amino acids Pinealocytes are secretory cells that secretes melatonin ○ Release of glucose in blood Melatonin Insulin Amine hormone derived from serotonin Target cells are liver cells, muscle, cells in the body except ○ Serotonin, oxytocin, and dopamine for joy brain tissue Functions Lowers blood glucose level by ○ Contribute to the setting of the body’s biological clock - ○ Accelerating glucose transport into cells suprachiasmatic nucleus ○ Glycogenesis ○ Promote sleepiness ○ Decreasing glycogenolysis and gluconeogenesis ○ Potent antioxidant ○ Increase lipogenesis ○ Inhibition of releasing hormones from the ○ Stimulate protein synthesis hypothalamus Stimulus is the darkness Somatostatin Target cells are pancreas and intestines Thymus Gland Function Located behind the sternum between the lungs ○ Inhibits secretion of insulin and glucagon Hormones - promote maturation of T cells ○ Slow absorption of nutrients from GI tract ○ Thymosin Happens some time after you eat, somatostatin stops the ○ Thymic Humoral Factor function of insulin and glucagon ○ Thymic Factor It slows down in order to absorbs all the possible nutrients ○ Thymopoietin Pancreatic Polypeptide Target cells are pancreas Function ○ Inhibits secretion of somatostatin, gallbladder contraction, and secretion of pancreatic digestive enzymes The one who tells you na busog ka na Ovaries and Testes NEUROPHYSIOLOGY  )10 TSH - Thyroid gland HYPOTHALAMIC - PITUITARY AXIS FSH and LH - Estrogen and Progesterone LH - Testosterone Hypothalamic - Pituitary Axis ACTH - Cortisol and other Glucocorticoids The hypothalamus and pituitary gland form a complex interface between the nervous system and endocrine Anterior pituitary hormones exert important growth effect system on target tissues, keeping them healthy and functional The brain can influence the activity of neurosecretory cells, FSH and LH are produced by the same type of cells and hormones can influence release of other hormones Each of the other anterior pituitary hormones is secreted by a different type of cell Pituitary Gland or Hypophysis This follows the pattern we’ve observed for other endocrine Lies beneath the hypothalamus gland and tissues that produces more than one hormones It is attached to the hypothalamus by a stalk called the infundibulum Understanding the pituitary gland requires careful study of the vascular supply. The six classic anterior pituitary hormones are released directly into the systemic circulation In humans, it consists of two lobes ○ The anterior lobe is endocrine tissue The anterior lobe and a small portion of the infundibulum make up the adenohypophysis ○ The posterior lobe is neural tissue The posterior lobe and most of the infundibulum The ventral hypothalamic hormones - TRH, GnRH, CRH, make up the neurohypophysis GHRH, SST, DA - regulate the function of the anterior pituitary cells. They are produced in neurons,a dn travel The six classic anterior pituitary hormones are down the axons to terminals where they are stored 1. Thyrotropin or Thyroid Stimulating Hormone The axon terminals do not extend into the pituitary gland; 2. Gonadotropin FSH they end at the base of the hypothalamus 3. Gonadotropin LH Stimuli that induce action potentials in the ventral 4. Corticotropin ACTH hypothalamic neurons cause release of their hormones into 5. Growth Hormone a capillary bed that drains into a second capillary bed before 6. Prolactin PRL entering the systemic circulation These two capillary beds are connected by the hypophyseal They are considered as anterior pituitary hormones because portal veins - special vessels that connect capillary beds. their structures and physiologic function in humans are This design allows small amounts of ventral hypothalamic understood hormones to be present in high concentrations at the anterior pituitary cells Most of the ventral hypothalamic hormones cause the secretion of anterior pituitary hormones The tropic hormones - TSH, FSH, LH, and ACTH - cause the release of hormones from other endocrine glands NEUROPHYSIOLOGY  )11 Thyrotropin-releasing hormones acts on cells of anterior pituitary to increase secretion of thyrotropin (TSH), which in turn acts on the thyroid gland to increase secretion of T3 and T4 ○ The thyroid hormones feedback almost exclusively to the anterior pituitary to inhibit secretion of TSH TH is also essential for anterior pituitary cells to secrete Growth Hormone GH The ventral hypothalamic hormones that influence the release of tropic hormones and growth hormone are the first hormones in a series that ultimately regulate the secretion of hormones from target glands The target glands include the thyroid gland, gonads, adrenal cortex, and liver, it secretes IGF A ventral hypothalamic hormone controls secretion of an anterior pituitary hormone that stimulates secretion of hormones from a target gland. The final hormone in the chain acts on target tissues of the body This kind of complex control system provides many input sites where other hormones and neurons can act to achieve fine control over the endocrine system Corticotropin-releasing hormone acts on cells of the anterior pituitary to increase secretion of corticotropin, which acts on the adrenal cortex to increase secretion of cortisol Cortisol feeds back to both anterior pituitary to inhibit secretion of ACTH, and to the ventral hypothalamus to inhibit secretion of CRH The cortisol system is subject to far more dynamic changes, and all hormones of the cortisol series exhibits a circadian rhythm For each hormone series, negative feedback loops control circulating levels of the target gland hormones Negative feedback exerted by the target hormone can be directed at the anterior pituitary, the ventral hypothalamus, or both Target hormones from one series can also influence the secretion of hypothalamus or anterior pituitary hormones Prolactin differs from the other anterior pituitary hormones, from another hormone series in these important ways ○ Its primary ventral hypothalamic drive is inhibitory ○ It does not stimulate release of another hormone from a target gland NEUROPHYSIOLOGY  )12 Prolactin is secreted in small amounts in both males and light signals from the retina can influence the endocrine females system through these circuits The amount in adult females is slightly higher than the Neuroendocrine reflexes like the milk ejection reflex, milk amounts in males and children, because estrogen letdown, are mediated in the hypothalamus modulates its secretion Estrogen increase prolactin secretion, but blocks the effect of prolactin in milk production ○ The high levels of estrogen during pregnancy, causes large secretion in circulating prolactin ○ Prolactin, estrogen, and other hormones promote growth of the breast, but the high levels of estrogen inhibit milk production ○ Milk production begins after child birth, when estrogen levels drop due to the removal of the placenta Suckling induces release of oxytocin that causes the myoepithelial cells of the mammary glands to contract and release milk The sound of a baby crying can cause a similar letdown of milk, and the anxiety and worry can inhibit the milk ejection reflex Chemically-Sensitive Neurons In summary, endocrine control of the hypothalamic-pituitary axis can be exerted by Negative feedback from a target hormone to a hormone of its own series Modulation by a target hormone of one series to hypothalamic-pituitary hormones of another series The hypothalamus is the highest level integrating center for the autonomic nervous system and the coordinating center for neuroendocrine interactions Fibers from many parts of the brain influence the endocrine system via hypothalamic neurons The cerebral cortex is widely connected both directly and indirectly to the hypothalamus Parts of the limbic system - thalamus, basal nuclei, reticular formation of the brainstem, and the retina project to the hypothalamus Hypothalamic neurons, including the neuro secretory cells that produce vasopressin behave like osmoreceptor - they detect osmotic changes in body fluids Example: An increase in the osmolarity in body fluids, due to fluid loss, excessive sweating or diarrhea excites osmoreceptors and stimulates both synthesis and release of vasopressin Vasopressin acts on the kidney to promote water reabsorption in effort to restore normal osmolarity Strong emotions like fear, body housekeeping signals like ingestion of food, harmful stimuli that produce pain, trauma, or infection, environmental changes like extreme cold, and Circadian Rhythms NEUROPHYSIOLOGY  )13 Thyroid hormone is the most important factor controlling basal metabolic rate It increases BMR, increasing oxygen consumption, and heat production Thyroid hormone is the main regulator of metabolism, it increases carbohydrate use It is necessary for lipogenesis, amplifies fat mobilization, and increases both synthesis and breakdown of protein Thyroid hormone is essential for growth It is permissive for the secretion of GH and the action of Neurons of the hypothalamus are pacemakers that insulin-like growth factor on bone and other tissues generates circadian patterns of hormonal release by the Thyroid hormone is essential for normal development of the hypothalamic pituitary axis nervous system Circadian rhythms are approximately 24 hours long Absence of thyroid hormone during the fetal period and The timing of the rhythm is synchronize to the 24 hour earth immediate postnatal months, produce a form of mental day by external signal retardation called cretinism ○ Cortisol and hypothalamic pituitary hormones exhibits If babies who lack thyroid hormone are treated immediately a circadian that synchronized by light postnatally, the condition can be prevented If babies are untreated, the condition is permanent and Cellular Mechanism of Action irreversible Thyroid hormones enters cells by diffusion Thyroid hormone is essential for normal function of the 20x more than T4 than T3 is secreted by follicle cells nervous system in adults By converting T4 to T3, the liver and kidney produce about Absence of or low levels of thyroid hormone lead to slow 80% of the free circulating T3 mental processes Other target tissues also produce T3, the active form of the Thyroid hormone amplifies the activity of the sympathetic hormone nervous system by upregulation of receptors of epi and Nearly every cell in the body, requires thyroid hormone for norepi normal function T3 binds to nuclear receptors that alter gene expression Breakdown Thyroid hormones are broken down by stepwise removal of Transport iodine atoms in peripheral tissues especially liver and The thyroid hormones are lipid soluble and therefore bind kidney to carrier proteins for transport through the circulatory system Approximately 99% of thyroid hormones are bound, and SYMPTOMS they exist in dynamic equilibrium with 1% unbound or free Scientists learn about the endocrine is to observe the hormone in the plasma symptoms of patient who secrete too much or too little of a Only the free hormones are available to leave the particular hormones - diseases associated with the thyroid bloodstream and act on target cells gland are common There is a large circulating reservoir of thyroid hormones Thyroid hormones have a long half-life in part because they Hyposecretion Hypersecretion are bound to carrier proteins Listlessness High BMR Secretion Thyrotropin or TSH controls secretion of thyroid hormone Low BMR Restlessness and promotes growth of the thyroid gland TRH is essential for secretion of TSH Feeling of no energy Hyperexcitable Thyroid releasing hormone is secreted in a circadian rhythm Stress may inhibit its release, but there are no known Feeling cold Sweating factors in adults that control its secretion A particular level of thyroid hormones seems to be required Lethargy Weight loss despite ample food for many normal physiological processes Thyroid hormone modulates physiological processes but Sleepiness Irritability does not initiate them Relatively constant levels of T3 and T4 are maintained by a Mental Sluggishness High heart rate negative feedback loop that inhibits secretion of thyroid stimulating hormones Impaired Memory Nervousness Synthesis Slowed Speech Exaggerated responses to stimuli in Thyroid hormone includes triiodothyronine T3 and thyroxine the environment T4, each is synthesized from tyrosine and stored in the thyroid follicles Slowed Reflexes Heart pounding - high force of Dietary iodine is essential for normal production for thyroid contraction hormone T3 has three iodine atoms and T4 has four iodine atoms Functions Full-blown hypothyroid syndrome in adults is called myxedema. The term comes from the edematous, puffy NEUROPHYSIOLOGY  )14 appearance of patients due to accumulation of water- Secondary Hypothyroidism holding carbohydrates in the skin Hypothyroidism is most commonly caused by an autoimmune disease called Graves’ Disease The body produces an antibody that mimics the action of thyroid-stimulating hormone The thyroid gland responds by enlarging and secreting increasing amount of thyroid hormones A unique symptoms of graves’ disease is protrusion of the eyeballs, called Exophthalmos, which results from deposits of water-holding carbohydrates behind the eyes To better understand the thyroid hormone pathologies, we need to know the hypo and hyper of the TH is a primary effect due to changes in the gland itself or whether the affect is secondary to changes in TSH It results from ○ Failure of the ant pituitary or hypothalamus In this condition, when TSH and possible also the thyrotropin releasing hormones levels are low, T3 and T4 levels diminish Because TSH levels are low, secondary hypothyroidism will not be associated with enlargement of the thyroid gland Primary Hypothyroidism It results from ○ Failure of the thyroid gland to secrete thyroid hormone ○ Failure of the thyroid gland to secrete enough thyroid hormone due to a deficiency of dietary iodine In both case, the amount of T3 and T4 secreted diminishes As plasma levels of TH fall, the inhibition to the anterior pituitary is interrupted and the anterior pituitary secretes increasing amounts of the TSH TSH stimulates growth of the thyroid gland, therefore high levels cause enlargement of the gland, called a Goiter When the hypothyroidism is associated with lack of dietary Primary Hyperthyroidism iodine, it is called an Iodine Deficient Goiter ○ Such goiter used to become imparts of the midwestern US due to low iodine concentrations in the soil ○ The introduction of iodized salt help reduce both the incidents of iodine deficient primary hypothyroidism and the number of such quarters NEUROPHYSIOLOGY  )15 RESPONSE TO STRESS Stress It results from When there is an overwhelming threat to the body, the ○ A TH-secreting tumor of the thyroid gland nervous and endocrine systems produce a well- ○ Graves’ Disease coordinated, generalized, nonspecific response designed In both cases, the amount of T3 and T4 secreted increases to ensure the survival and health of the individual As plasma levels of the thyroid hormone rise, the inhibition to the ant pituitary increases and the anterior pituitary We also have reviewed hormones associated with secretes decreasing amount of TSH situations that pose a serious risk, or physical or emotional Because of the hormone pattern observed, we expect that harm to a person. In each instance, the body responds primary hyperthyroidism will not produce a goiter In individual ways to maintain homeostasis With low TSH and the concomitant of its trophic actions of With a coordinated generalized nonspecific response called the thyroid gland, we might expect the thyroid gland in the the stress response same size or atrophy, that is the case for thyroid hormone secreting tumors Increased blood levels of the hormone epinephrine, In Graves’ Disease the body produces an antibody, called norepinephrine, and cortisol are markers that indicate an the Thyroid-Stimulating Immunoglobulin or TSI, which individual is experiencing stress mimics the actions of TSH The high levels of TSi stimulate growth of the thyroid gland Stressors include prolonged exposure to temperature extremes, and can produce a goiter heavy exercise, fright, surgery, and emotional stresses - happy Note that increase level of TH do not diminish the or unhappy production of TSI because there is no negative feedback relationship between them Hypothalamus Directs the body’s stress response Secondary Hyperthyroidism The nervous system sends information about the stressful condition to the hypothalamus, which then engages both the nervous and endocrine systems in response The hypothalamus engages the sympathetic nervous system in a neural and endocrine response, the well-known fight-or-flight response, which prepares the body for immediate physical action In a combination of direct action by the sympathetic fibers and epinephrine from the adrenal medulla, CO increases, ventilation, increases, BP rises, and is maintained to drive blood to the working organs and blood flow is directed to the GI system and other quiescent organs to skeletal muscle and the heart, sweating is stimulated It results from ○ Excess secretion by the ant pit or hypothalamus In this condition, when TSH and possible the TRH levels are high, T3 and T4 levels increase Because TSH levels are high, secondary hyperthyroidism will be associated with enlargement of the thyroid gland Epinephrine reinforces the actions of the sympathetic system, especially relaxation of the airways and dilation of blood vessels NEUROPHYSIOLOGY  )16 to skeletal muscle and the heart. Epinephrine directly stimulates tissues to meet increased metabolic needs Major Effects of Epinephrine Stimulation of glycogenolysis of liver and skeletal muscle Gluconeogenesis in the liver Lipolysis in adipose tissue Glucose and fatty acids provide fuel for working organs. The activity of the sympathetic system and epinephrine inhibit the release of insulin and stimulate glucagon. Glucagon reinforces the fasting metabolic state and the active inhibition of insulin is essential to keep plasma glucose high. The fast-acting catecholamines initiate the stress response. They produce rapid short-term changes since they are secreted rapidly from storage vesicles and act rapidly on target cells. Aldosterone Secreted from the adrenal cortex in response to increased The hypothalamus also stimulates release of CRH angiotensin (corticotropin releasing hormone) that causes secretion of Promotes retention of salt and water, to maintain blood ACTH and ultimately cortisol for a more prolonged response. volume and blood pressure Because its synthesis and release is slow, and cellular responses require transcription and translation, the response of Vasopressin (ADH) cortisol after a lag of about 30 minutes Secreted from the posterior pituitary It promotes water retention and with angiotensin directs vasoconstriction effects This response becomes more complicated as combinations of the hormones act to reinforce existing effects and add others The nervous and endocrine system maximize gas exchange, mobilize fuel, and maintain the necessary pressure to deliver blood to essential organs. These two systems work together to maintain high levels of oxygen and nutrients in the bloodstream and to ensure their delivery to essential organs. Adrenal cortical hormones maintain and amplify the effects of adrenal medullary hormones. Together the two parts of the adrenal gland act as a functional unit that first initiates, and then maintains and modulates, the response to stress Remember that cortisol is a glucocorticoid named for its effects on glucose metabolism. Cortisol mobilizes energy stores, and stimulates breakdown of protein, providing amino acids to the liver to produce glucose. The amino acids can also be used to repair damaged tissue. Review on Epinephrine Cortisol acts on the liver, to both produce and store glucose as 1. Cellular Mechanisms of Action glycogen. Cortisol stimulates breakdown of triglycerides and ○ Epinephrine binds to receptors on the cell surface adipose tissue that increases fatty acids for fuel, and glycerol for ○ The many different catecholamines receptors activate producing glucose in the liver. Fuels continue to be made G proteins that produce second messengers available, glucose for the brain, and fatty acids for other tissues, ○ Cellular responses are mediated by phosphorylation of to ensure survival at a time when an individual may not be able proteins to eat. ○ Catecholamines affect nearly every organ in the body 2. Transport In the presence of norepinephrine, cortisol enhances the ○ Epinephrine is water soluble and is transported in the constriction of blood vessels. This is an important contribution to bloodstream as dissolved particles maintaining blood pressure. Cortisol also inhibits inflammation ○ Epinephrine molecules dissolve in blood plasma and other aspects of the immune system, keeping it incheck. ○ Because dissolved particles are readily broken down and because epinephrine is rapidly removed from the NEUROPHYSIOLOGY  )17 bloodstream, it has a short half-life lasting about 10 seconds The most prominent feature in patients with a pheochromocytoma is hypertension. Catecholamines act on the 3. Secretion cardiovascular system to maximize cardiac output by increasing ○ The sympathetic nervous system controls secretion of HR and force of contraction. Catecholamines increase total epinephrine peripheral resistance increases in cardiac output and peripheral ○ Stress, exercise, hemorrhage, hypoxia, and resistance, causing blood pressure to rise. hypoglycemia all stimulate sympathetic activity The treatment of choice for a pheochromocytoma is surgical 4. Synthesis removal of the tumor. Secretion of catecholamine hormones ○ Epinephrine is synthesized from tyrosine in adrenal then returns to normal, and is again under control of the medulla cells that are modified sympathetic sympathetic nervous system. postganglionic neurons ○ Adrenal Medulla cells that make epinephrine are Review on Cortisol modified sympathetic neurons 1. Cellular Mechanism of Action ○ Epinephrine and norepinephrine are stored ○ Cortisol enters cells by simple diffusion intracellularly in storage vesicles ○ Nearly every cell in the body have receptors for the glucocorticoids 5. Functions ○ Cortisol binds to receptor in cytosol, and the nucleus ○ Generalized activation of the sympathetic nervous that alter gene expression system causes release of the neurotransmitter ○ In addition to intracellular receptors, there are plasma norepinephrine from postganglionic sympathetic nerve membrane receptors for cortisol fibers ○ Rapid inhibition or CRH by the feedback loop is ○ Released of the hormone of epinephrine and small mediated through these plasma membrane receptors amounts of norepinephrine from the adrenal medulla ○ Action of the adrenal medulla represents the effect of 2. Transport epinephrine ○ Cortisol binds to plasma proteins for transport through ○ Epinephrine reinforces the activity of sympathetic the circulatory system, since steroid hormones are lipid nerve fibers soluble ○ Because epinephrine reaches all cells of the body ○ The bound hormone exists in dynamic equilibrium with through the blood system, it can increase blood levels unbound or free hormone in the plasma of glucose and other fuel molecules and like Thyroid ○ Only the free hormone is available to leave the hormone increase metabolic rate bloodstream and act on target cells ○ The sympathetic nervous system, including epi ○ Because cortisol is bound to carrier proteins, it has a supplies adequate amount of fuel molecules and relatively long half-life lasting about 90 minutes oxygen and ensures their delivery to body cells ○ It is an integral part of the stress response 3. Secretion ○ ACTH controls secretion of cortisol and promotes the growth of the inner zones of the adrenal cortex 6. Breakdown ○ CRH stimulates secretion of ACTH ○ Epinephrine is taken up by the endothelium, heart, ○ Negative feedback from cortisol inhibits the secretion liver, and other tissues where it is broken down by of both ACTH and CRH enzymes ○ Despite the negative feedback system, blood levels of ○ Breakdown products are excreted in the urine ACTH and Cortisol vary in a circadian rhythm ○ This daily variability results from the changings Pathological changes in the secretory activity of the adrenal sensitivity of the CRH secreting cells to cortisol medulla are rare. There are no recognized pathologies that ○ The circadian rhythm may allow the nervous and cause hyposecretion of the catecholamines from the adrenal endocrine systems to anticipate the need for cortisol medulla. Because the sympathetic nervous system may replace that is associated with daily activity many of the functions of the adrenal catecholamines and ○ Stressors like pain, fear, physical trauma, infection, individuals without the adrenal medulla as long as the prolonged cold, or emotional problems elicit secretion sympathetic nervous system is intact and functioning. of CRH ○ Other hormones associated with stress, such as A rare tumor called the pheochromocytoma secretes large vasopressin, ADH increase cortisol levels amounts of the catecholamines and is not controlled by the sympathetic nervous system. Symptoms associated with a 4. Synthesis pheochromocytoma may be persistent or intermittent. Episodic ○ Cortisol is synthesized from cholesterol in adrenal symptoms can arise from probing the tumor, standing up or lying cortex cells down, or abdominal pressure. ○ The cells do not store cortisol Symptoms 5. Functions 1. Excessive sweating ○ Cortisol is important in the body’s response to stress 2. Rapid heart rate ○ It is key smoking the many hormones involved in 3. Palpitations