Endocrine System Review PDF

Endocrine System ACTIVITY CONTROLLING MECHANISMS Nervous System Endocrine System Electrical messages Chemical messages Uses: Maintain homeostasis Maintain homeostasis Response...

Endocrine System ACTIVITY CONTROLLING MECHANISMS Nervous System Endocrine System Electrical messages Chemical messages Uses: Maintain homeostasis Maintain homeostasis Response faster slower time: Duration of shorter longer response: What Excitable tissues Target cells cells/tissues -​ Muscles -​ Cells with receptors does it -​ glands x affect: Receptors: N/A Each cell has specific receptors These two systems work together. The Nervous system can even regulate activity of the Endocrine system. GLANDS Type Ducts? Produce: Other Info (Y/N) Exocrine yes Substances such as Related to digestion and tears, sweat, saliva, sweat glands breast milk, digestive juices, etc. Endocrine no hormones Highly vascularized Some glands, like the pancreas, have both endocrine and exocrine portions. NEUROENDOCRINE LINK There is a (weak/strong) connection between the nervous and endocrine systems. The major connection between the two is the hypothalamus, which is a major regulator of the endocrine system. CHEMICAL MESSENGERS Hormones o (short/long) distance chemical messengers. o Produced in one part of the body and have their effect (at the same part/somewhere else) part of the body. Autocrine o Secretion that is produced by a cell and affects the activity of that cell (self regulating). o Very localized effects. Paracrines o A local signaling molecule. o Secreted by a cell and affects neighboring cells. ▪ (Does/Doesn’t) affect activity of the cell which produced it. Pheromones o Chemicals that are produced by one organism and affect the activity of other organisms. o Usually used as an attractant or repellant HORMONE CLASSIFICATIONS (based on biochemical makeup) Amino acid based (non-steroid) o Derived from peptides/proteins. o Most of the hormones in our body. o They are water soluble, which makes them easy to transport in the blood, but they’re unable to pass across the plasma membrane. o Receptor for these must be on the outside of the cell. Steroid o Derived from cholesterol. o They are lipid/fat soluble, which makes them a little more difficult to transport in the bloodstream, but they can pass across the plasma membrane. o Receptors can be located inside the cell. o Produced by 2 structures: ▪ gonads ▪ Cortex of the adrenal gland Eicosanoid o Not considered a true hormone. ▪ Released by cell membranes, but only have localized effects. o They are bio active lipids. o Types: ▪ prostaglandins Have multiple effects in cells. ▪ leukotrienes Generally involved in inflammatory response or related to the immune system. HORMONE ACTIONS Target cells o Any cell that has a receptor for a hormone. o Hormone will change the permeability of its target cell once it binds to the receptor. ▪ The effect of this hormone is dependent on the target cell. ▪ The same hormone can have different effects, depending on what type of cell it is interacting with. o Potential effects: 1. Open or close ion channels Changing permeability of the cell. This leads to changes in membrane potential. 2. Stimulate protein synthesis Some hormones will directly activate DNA to produce new proteins. 3. Activate or deactivate enzymes Proteins that already exist could be turned on or off. 4. Promote secretion Hormones could stimulate exocytosis by the target cell. Target cells may produce a number of things that could cause local or global changes. One hormone can cause a target cell to release a different hormone. 5. Stimulate mitosis/division Cell division and growth (replication of cells). HORMONAL MECHANISMS Mechanism Receptor location Type of Involves Activation Amino Plasma membrane indirect G protein Acid-based Secondary messenger Steroid Inside nucleus direct N/A STEROID ACTION 1.​ Hormone secreted by an endocrine gland. 2.​ Travels through the bloodstream to a target cell. 3.​ Hormone diffuses through the plasma membrane of the target cell. 4.​ Binds with intracellular receptor. ○​ Receptor usually located in the nucleus. 5.​ Activated steroid/receptor complex acts as a primer and binds to a specific receptor protein on DNA. ○​ Different steroid hormones could activate different genes and cause different proteins to be produced. 6.​ Transcription initiated. 7.​ DNA translated. 8.​ proteins produced (could be enzymes, structural proteins, or export proteins). NON-STEROID ACTION Two mechanisms: 1.​ AMP mechanism 2.​ PIP-calcium mechanism ❖ CYCLIC AMP MECHANISM 1.​ Hormone secreted by an endocrine gland. 2.​ Travels through the bloodstream to a target cell. 3.​ Hormone binds to a specific membrane receptor on the outside surface of the cell. 4.​ Modified receptor binds with G protein. (which is an internal peripheral protein) 5.​ G protein is activated. 6.​ Activated G protein activates an enzyme called adenylate cyclase. 7.​ Adenylate cyclase generates cAMP from ATP. 8.​ cAMP stimulates another enzyme, called protein kinase, to react. 9.​ Protein kinases causes proteins to be phosphorylated (add phosphate to existing proteins) – this can either activate or deactivate them. 10.​Phosphodiesterase degrades cAMP and shuts the cycle off. ❖ PIP-CALCIUM MECHANISM 1. Hormones secreted by an endocrine gland. 2. Travels through the bloodstream to a target cell. 3. Hormone binds to membrane receptor. 4. Modified receptor binds with G protein. 5. G protein is activated. 6. Activated G protein activates phospholipase. 7. Phospholipase splits PIP2 into DAG and IP3. 8. DAG activates protein kinases (just like cAMP in other mechanism), which causes phosphorylation of existing proteins (activating or deactivating them).  9. IP3 triggers release of calcium from Endoplasmic Reticulum. 10. Calcium acts as an additional secondary messenger, catalyzing additional reactions in the body. FACTORS AFFECTING HORMONE ACTION Hormone level in bloodstream o The more in the bloodstream, the greater the activity. # of receptors in/on target cells o The more we have, the greater the activity. Receptor affinity o Some receptors have greater affinity for hormones than others. o The higher this is, the greater the activity. TYPES OF REGULATION Up Regulation o The effect of continued exposure to a hormone results in (more/fewer) receptors for that hormone, which means the cells will become (more/less) active. o If there was a stress that caused a hormone to be produced, the cells will respond by (increasing/decreasing) the response to get us back to homeostasis. o The effect of the hormone increases the number of receptors for that hormone. Down Regulation: o The continued release of a hormone results in a decrease in the number of receptors for that hormone. o Increase in level of hormone (lessens/increases) the effect of that hormone. HORMONE INTERACTIONS Permissiveness o This is where one hormone requires a second hormone in order to exert its fullest effects. o Ex. Thyroid hormone assisting reproductive function Synergism o Multiple hormones produce the same effects. o Combined effects are stronger. o Ex. glucagon and norepinephrine regulating blood glucose Antagonism o Sometimes hormones work in opposition to one another. o This helps set up feedback systems. o Ex. insulin and glucagon having opposite effects on blood sugar levels MODES OF ENDOCRINE GLAND STIMULATION Humoral o Changes in blood chemistry/concentration. Increase or decrease in ions or nutrients in the blood may be detected by the cell, and it will respond. Neural o Nervous stimulation can activate a gland to secrete a hormone. Hormonal o One endocrine gland is activated by a hormone produced by a different endocrine gland. o A “tropic” hormone is one whose target cell is another endocrine gland. All endocrine system activity has an override with the nervous system. The two systems work together. Endocrine gland stimulations are inhibited by negative feedback systems. ENDOCRINE GLANDS pituitary: an extension off of the brain. thyroid: surrounds the trachea. parathyroid: embedded within the thyroid. adrenals: on top of the kidneys pancreas: in the abdominal cavity gonads: testes in the male and ovaries in the female. pineal: in the brain. thymus: (is/is not) very active in adults. PITUITARY GLANDS (HYPOPHYSIS) Posterior pituitary (neurohypophysis) o Composed of neural tissue. o Outgrowth of the hypothalamus o Extends off of the infundibulum. o (does/does not) produce hormones. only stores and secretes them. Anterior pituitary (adenohypophysis) o Next to the posterior pituitary. o Composed of glandular tissue. ▪ (does/does not) produce secretions o An out-pocketing of the oral cavity (specifically an area called rathke's pouch). Infundibulum o Stalk extending off of the hypothalamus. o Anchors the pituitary gland. o Of neural origin. There is only a vascular connection between anterior and posterior parts of the pituitary. TROPIC HORMONES Their target tissues are other endocrine glands. Cause the production of another hormone. = HORMONES SECRETED BY POSTERIOR PITUITARY The posterior pituitary gland does not produce hormones; it only stores and secretes them. Both of these hormones are amino acid based and use the PIP calcium mechanism. 1.​ Oxytocin ○​ Stimulates smooth muscle contraction. ▪ Causes contract ▪ Also involved with milk ejection (not production) during nursing. ○​ Functions through positive feedback. ○​ also involved with sexual arousal & sexual satisfaction; known as “cuddle hormone” ○​ functions as an amnesiac, which means it helps individuals forget the past 2.​ Antidiuretic Hormone (ADH) ○​ Regulates water balance ▪ Targets the kidney tubules and causes them to reserve more water. Prevents urine formation. ▪ Helps in osmoregulation of our body. ▪ The hypothalamus monitors the solute concentration (tonicity) of the blood. It can activate secretion of ADH. ▪ Alcohol inhibits ADH. HORMONES SECRETED BY ANTERIOR PITUITARY These are produced by the anterior pituitary, but production is activated by a signal from the hypothalamus. All are amino acid based and use cAMP method. 1.​ growth hormone (GH) 2.​ thyroid stimulating hormone (TSH) 3.​ adrenocorticotropic hormone (ACTH) 4.​ Gonadotrophs ○​ FSH & LH 5.​ prolactin (PRL) 6.​ pro-opiomelanocortin (POMC) ~ not really considered a hormone yet ○​ Causes production of the body’s own opioids (related to pain suppression). ○​ Related to melanocytes, which produce melanin. ○​ The “cortin” portion means it is related to the adrenal cortex, and it has some effects with ACTH. Adenohypophyseal hormones and their effects 1.​ GROWTH HORMONES (GH) Actions: Stimulates cell growth and division, protein synthesis, fat metabolism, and glucose conservation. Most importantly involved with growth of muscles and bones. Disorders: pituitary dwarfism: o Deficiency of GH in children. o Overall small size. gigantism:shu o Excess GH in children. o Overall large size. acromegaly: o Normal levels of GH as a child, but increases as an adult. o Characteristic large faces, hands and feet. Cascade: 1.​ hypothalamus secretes GHRH (Growth Hormone Releasing Hormone). 2.​ GHRH affects somatotropic cells of anterior pituitary and they begin GH synthesis. 3.​ GH gets in the bloodstream and has both direct and indirect effects on target tissues. 4.​ Increased amount of circulating GH triggers production of GHIH (Growth Hormone Inhibiting Hormone, aka somatostatin). 5.​ GHIH shuts off production of GHRH in order to stop production of GH.