Endocrine Control


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Endocrine Control

  1. 1. Chemical Control of Brain and Behavior The Neuroendocrine Link
  2. 2. Patterns of Communication <ul><li>Communication in the nervous system can be: </li></ul><ul><li>Point-to-point </li></ul><ul><ul><li>How most of the nervous system is wired </li></ul></ul><ul><ul><li>Specific connections for specific functions </li></ul></ul><ul><li>Neurosecretion into the bloodstream </li></ul><ul><ul><li>The hypothalamus is the key player </li></ul></ul><ul><ul><li>Targets are distributed </li></ul></ul><ul><ul><li>Hormones (blood-borne neurotransmitters) reach their targets through the circulatory system </li></ul></ul><ul><li>Subnetworks controlled from the CNS </li></ul><ul><ul><li>Autonomic nervous system </li></ul></ul><ul><li>Diffuse modulatory systems </li></ul>
  3. 3. Types of Hormones <ul><li>Steroids </li></ul><ul><ul><li>fat-like organic compounds (sex hormones, corticoids ) </li></ul></ul><ul><ul><li>Steroids pass through target cell membranes, combine with receptor molecules, move into cell nucleus, then helps determine manufacture of specific proteins </li></ul></ul><ul><li>Protein hormones </li></ul><ul><ul><li>all others </li></ul></ul><ul><ul><li>affect target cells in 2 step process = 2nd messenger system: </li></ul></ul><ul><ul><li>1st messenger, hormone, combines with receptor on target cell membrane </li></ul></ul><ul><ul><li>activates an enzyme on the membrane's inside wall </li></ul></ul><ul><ul><li>That enzyme changes ADP to cyclic AMP (the 2nd messenger) </li></ul></ul><ul><ul><li>Which triggers enzymes that produce the effect </li></ul></ul>
  4. 4. Hormone Actions
  5. 5. The Hypothalamus <ul><li>Above pituitary and below thalamus </li></ul><ul><li>Three zones: </li></ul><ul><ul><li>lateral </li></ul></ul><ul><ul><li>medial </li></ul></ul><ul><ul><li>periventricular </li></ul></ul><ul><li>Master switchboard of the endocrine system </li></ul><ul><li>Receives signals from the entire body through the nervous system </li></ul><ul><li>Sends signals to stimulate or inhibit hormone secretion by other glands (eg. pituitary) </li></ul>
  6. 6. Locating the Hypothalamus
  7. 7. The Periventricular Zone <ul><li>Suprachiasmatic nucleus - synchronize circadian rhythms with light-dark cycles </li></ul><ul><li>Control neurons for the autonomic nervous system </li></ul><ul><li>Neurosecretory neurons </li></ul><ul><ul><li>extend axons down the talk of the pituitary </li></ul></ul>
  8. 8. Tropic Hormones <ul><li>Tropic hormones stimulate or inhibit hormone secretion </li></ul><ul><li>Releasing hormones = those that stimulate </li></ul><ul><li>Inhibiting hormones = those that slow secretion </li></ul><ul><li>At least 9 are made by the hypothalamus </li></ul><ul><ul><li>These control TSH, GH, LH, FSH, ACTH & prolactin </li></ul></ul>
  9. 9. The Hypothalamus & Homeostasis <ul><li>Homeostasis is the regulatory process that maintains body's internal environment within a narrow physiological range </li></ul><ul><li>Supervised by neurons in the hypothalamus </li></ul><ul><li>Includes temperature regulation, regulation of blood volume, regulation of blood pressure, salinity, acidity, oxygenation, and glucose concentration </li></ul>
  10. 10. The Pituitary <ul><li>At the base of the brain </li></ul><ul><ul><li>Suspended from hypothalamus by a stalk </li></ul></ul><ul><ul><li>about the size of a bean </li></ul></ul><ul><li>Acted on by hypothalamus </li></ul><ul><li>2 sections: </li></ul><ul><ul><li>Anterior Lobe </li></ul></ul><ul><ul><li>Posterior Lobe </li></ul></ul>
  11. 11. The Anterior Lobe <ul><li>Parvocellular neurosecretory cells in the hypothalamus release into a specialized capillary bed called the hyopthalamo-pituitary portal circulation </li></ul><ul><li>Hypophysiotropic or releasing hormones are secreted </li></ul><ul><li>These bind to receptors on cells in anterior lobe of pituitary and increase or decrease their secretion of other hormones </li></ul>
  12. 12. Anterior Pituitary Hormones <ul><li>Tropic (affect other glands): </li></ul><ul><ul><li>FSH ( follicle stimulating hormone ) </li></ul></ul><ul><ul><li>LH ( lutenizing hormone ) - acts on gonads </li></ul></ul><ul><ul><li>TSH ( thyroid stimulating hormone ) - stimulates thyroid to produce thyroxin </li></ul></ul><ul><ul><li>ACTH ( corticotropic hormone ) - affects adrenal cortex </li></ul></ul><ul><ul><li>MSH (melanocyte stimulating hormone) </li></ul></ul><ul><ul><li>endorphins </li></ul></ul><ul><li>Nontropic: </li></ul><ul><ul><li>Somatotropin (or growth hormone - GH) </li></ul></ul><ul><ul><li>Prolactin - stimulates milk production </li></ul></ul>
  13. 13. Tropic Hormone Function <ul><li>Example: </li></ul><ul><li>CRH (corticotropin-releasing hormone is secreted by the parvocellular neurosecretory neurons into the portal system. </li></ul><ul><li>where it triggers the release of corticotropin. </li></ul><ul><li>Corticotropin triggers the release of cortisol from the adrenal cortex. </li></ul><ul><li>Cortisol has many effects </li></ul><ul><li>One of which is to inhibit the release of CRH from the hypothalamus - the system is self regulating </li></ul>
  14. 15. Anterior Pituitary Cascade
  15. 16. Posterior Pituitary <ul><li>Does not produce hormones, but stores 2 made by the hypothalamus </li></ul><ul><li>Magnocellular neurosecretory cells in hypothalamus release two peptide hormones </li></ul><ul><li>ADH (antidiuretic hormone or vasopressin) </li></ul><ul><ul><li>keeps blood volume constant by controlling reabsorbtion of H 2 0 in kidneys </li></ul></ul><ul><li>Oxytocin stimulates contractions of uterus at childbirth </li></ul>
  16. 17. Posterior Pituitary Cascade
  17. 18. Vasopressin Function <ul><li>At Low blood volume and blood pressure the kidneys secrete renin </li></ul><ul><li>Renin converts angiotensinogen from the liver into angiotensin I and then to angiotensin II </li></ul><ul><li>Angiotensin II has direct effects on the kidney and blood vessels to increase blood pressure </li></ul><ul><li>Angiotensin II is also detected by the subfornical organ in the telencelphalon which is outside the blood brain barrier </li></ul><ul><li>Subfornical organ neurons project to magnocellular neurosecretory neurons </li></ul><ul><li>Vasopressin is released to increase water retention in kidney </li></ul>
  18. 19. Endocrine Overview
  19. 20. The Thyroid <ul><li>On the trachea </li></ul><ul><li>Secretes thyroxine </li></ul><ul><ul><li>regulates rate of cellular respiration </li></ul></ul><ul><ul><li>controls metabolic activities including production of proteins & ATP necessary for proper development of nervous system & growth </li></ul></ul><ul><li>Need iodine to produce thyroxine </li></ul><ul><ul><li>Too little iodine = enlarged thyroid = goiter </li></ul></ul>
  20. 21. The Parathyroids <ul><li>On the back of the thyroid </li></ul><ul><ul><li>4 tiny glands </li></ul></ul><ul><li>Secrete PTH ( parathyroid hormone ) </li></ul><ul><ul><li>regulates level of calcium ions & phosphate ions in the blood (necessary for bones, muscles, nerves) </li></ul></ul>
  21. 22. Hormonal Regulation of Calcium
  22. 23. The Adrenals <ul><li>Located on top of each kidney </li></ul><ul><li>Each is like 2 separate glands </li></ul><ul><li>Inside = Adrenal medulla </li></ul><ul><li>Outside = Adrenal Cortex </li></ul>
  23. 24. The Adrenal Medulla <ul><li>In response to nerves signals from the sympathetic division of the autonomic nervous system, secretes epinephrine & norepinephrine </li></ul><ul><li>Fight or flight - like stepping on the accelerate with the brake on </li></ul><ul><li>Response to stress: </li></ul><ul><ul><li>increases blood pressure, heart rate, breathing, dilates pupils, increases metabolism </li></ul></ul>
  24. 25. Stress & the Adrenal Gland
  25. 26. Adrenal Cortex <ul><li>Secretes more than 50 hormones </li></ul><ul><ul><li>corticoids </li></ul></ul><ul><li>Include: </li></ul><ul><li>Aldesterone </li></ul><ul><ul><li>controls reabsorbtion of Na+ & K+ by the kidney </li></ul></ul><ul><li>Cortisol (hydrocortisone) </li></ul><ul><ul><li>controls glucose uptake by cells </li></ul></ul><ul><li>Androgens </li></ul><ul><ul><li>sex hormones </li></ul></ul>
  26. 27. The Pancreas <ul><li>Also an exocrine gland </li></ul><ul><ul><li>produces digestive enzymes </li></ul></ul><ul><li>Islets of Langerhans </li></ul><ul><ul><li>a group of cells within the pancreas, function as endocrine glands </li></ul></ul><ul><li>Secrete insulin and glucagon which have opposite effects: </li></ul><ul><li>Insulin </li></ul><ul><ul><li>lowers level of glucose in blood; without it glucose cannot enter body cells </li></ul></ul><ul><li>Glucagon </li></ul><ul><ul><li>triggers breakdown of glycogen to glucose . </li></ul></ul>
  27. 28. Blood Glucose Regulation
  28. 29. The Gonads <ul><li>Gamete producing organs, also produce hormones </li></ul><ul><li>female = estrogen </li></ul><ul><li>male = androgen, testosterone </li></ul><ul><li>both produce secondary sex characteristics, involved in reproduction </li></ul>
  29. 30. The Autonomic Nervous System <ul><li>Three divisions: </li></ul><ul><ul><li>Sympathetic </li></ul></ul><ul><ul><li>Parasympathetic </li></ul></ul><ul><ul><li>Enteric </li></ul></ul>
  30. 31. Sympathetic Division <ul><li>Disynaptic pathway: </li></ul><ul><ul><li>releases acetylcholine onto sympathetic ganglion and norepinephrine postsynaptically </li></ul></ul><ul><li>Sympathetic ganglia form sympathetic chain along side the spinal cord </li></ul><ul><li>Functions </li></ul><ul><ul><li>Dilates pupil </li></ul></ul><ul><ul><li>Inhibits salivation and tearing </li></ul></ul><ul><ul><li>Constricts blood vessels </li></ul></ul><ul><ul><li>Accelerates heart rate </li></ul></ul><ul><ul><li>Stimulates glucose release from liver </li></ul></ul><ul><ul><li>Inhibits digestion </li></ul></ul><ul><ul><li>Stimulates orgasm </li></ul></ul>
  31. 32. Adrenal Organogenesis
  32. 33. Parasympathetic Division <ul><li>Disynaptic pathway: </li></ul><ul><li>releases acetylcholine onto parasympathetic ganglion and acetylcholine postsynaptically </li></ul><ul><li>Ganglia are scattered all over the place </li></ul><ul><li>Functions: </li></ul><ul><ul><li>Constricts pupil </li></ul></ul><ul><ul><li>Stimulates salivation and tearing </li></ul></ul><ul><ul><li>Slows heart rate </li></ul></ul><ul><ul><li>Stimulates digestion </li></ul></ul><ul><ul><li>Stimulates release of insulin from pancreas </li></ul></ul><ul><ul><li>Stimulates sexual arousal </li></ul></ul>
  33. 34. Yin & Yang <ul><li>These two divisions generally oppose each other in effect </li></ul><ul><li>Only one is activated at a time </li></ul><ul><li>Sympathetic division is activated during a crisis: </li></ul><ul><ul><li>fight/flight/fright/sex - the 4 F's </li></ul></ul><ul><li>Parasympathetic division is active over long periods of time </li></ul>
  34. 35. Enteric Division <ul><li>Involves little direct brain function </li></ul><ul><li>Semi-autonomous double: </li></ul><ul><ul><li>Auerbach's plexus and Meissner's plexus </li></ul></ul><ul><li>Found in esophagus, stomach, intestines, pancreas, and gall bladder </li></ul><ul><li>Functions to control digestion </li></ul><ul><li>Master control comes from the parasympathetic and sympathetic divisions </li></ul>
  35. 36. Autonomic/ Endocrine Link <ul><li>Central control of the ANS </li></ul><ul><li>Periventricular zone of hypothalamus </li></ul><ul><li>Nucleus of the solitary tract </li></ul><ul><ul><li>Integrates sensory inputs from internal organs and has outputs to the autonomic ganglia </li></ul></ul>
  36. 37. Diffuse Modulatory Systems <ul><li>General characteristics: </li></ul><ul><li>Core of each system is a small number of neurons, several thousand </li></ul><ul><li>Core neurons are in central core of brain and brainstem </li></ul><ul><li>Connections of one core neuron may affect 100,000 postsynaptic neurons widely dispersed </li></ul><ul><li>Synapses by core neurons release into extracellular fluid rather than at standard synapses </li></ul>
  37. 38. Noradrenergic System <ul><li>Core neurons are in the locus coeruleus in the pons </li></ul><ul><li>Targets are spinal cord, cerebellum, hypothalamus, thalamus, and most of neocortex </li></ul><ul><li>Noradrenalin is released </li></ul><ul><li>Functions are complex </li></ul><ul><li>Involved in regulation of attention, arousal, and sleep-wake cycles </li></ul><ul><li>Core neurons are activated by novel, non-painful sensory stimuli </li></ul><ul><li>General increase of brain responsiveness </li></ul>
  38. 39. Serotonergic System <ul><li>Core neurons are in the Raphe nuclei in the brainstem from the pons to the medulla </li></ul><ul><li>Targets are spinal cord, cerebellum, hypothalamus, thalamus, basal ganglia, and all of neocortex </li></ul><ul><li>Serotonin is released </li></ul><ul><li>Function - complex </li></ul><ul><li>Core neurons are most active when animal is awake, least active during sleep </li></ul><ul><li>Also involved in control of mood and some types of emotional behavior </li></ul><ul><li>May work together with noradrenergic system during general arousal </li></ul>
  39. 40. Dopaminergic System <ul><li>Core neurons are in the substantia nigra and the ventral tegmental area , both in the floor of the midbrain </li></ul><ul><li>Targets are the striatum and the frontal lobe of neocortex </li></ul><ul><li>Dopamine is released </li></ul><ul><li>Function: </li></ul><ul><ul><li>Part of the reward system for certain adaptive behaviors </li></ul></ul><ul><ul><li>involved in addiction </li></ul></ul><ul><li>Malfunctions may lead to psychiatric disorders </li></ul>
  40. 41. Cholinergic System <ul><li>Core neurons are in the basal forebrain complex </li></ul><ul><ul><li>basal nucleus of Meynert </li></ul></ul><ul><ul><ul><li>innervates most of neocortex </li></ul></ul></ul><ul><ul><li>Medial septal nuclei </li></ul></ul><ul><ul><li>innervate hippocampus </li></ul></ul><ul><li>Core neurons are also in the pontomesencephalo-tegmental complex </li></ul><ul><ul><li>in pons and midbrain tegmentum </li></ul></ul><ul><li>Innervate the thalamus and cortex </li></ul><ul><li>Acetylcholine is released </li></ul><ul><li>Function - largely confused </li></ul><ul><ul><li>Alzheimer's starts with these cholinergic neurons </li></ul></ul><ul><ul><li>General arousal and sleep-wake cycles </li></ul></ul><ul><ul><li>May have some role in memory </li></ul></ul>