Ch. 18: The Endocrine System

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Almost everything you need to know about the endocrine system

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Question Answer
What are some characteristics of the Nervous System? - Works using neurons to send action potentials which secrete a neurotransmitter to a postsynaptic membrane - Briefer response - Shorter effect
What are the target cells for the Nervous System? - Muscle cells - Gland cells - Other neurons
What are some characteristics of the Endocrine System? - Controls functions of the body using hormones - Hormones are at 1 part of the body but regulates the activity of another part of the body - Longer time to respond - Longer effect
What are the target cells for the Endocrine System? Every target cell in the body
How do hormones travel? Through the bloodstream
What are the 2 types of Glands? - Exocrine Glands - Endocrine Glands
What are exocrine glands? Glands that secrete products into ducts and take those products to the lumen of organ, body cavity, or outer surface of the body
What are some examples of exocrine glands? - Sweat glands - Sebaceous glands - Digestive glands - Mucous glands
What are endocrine glands? Endocrine glands do NOT use ducts. They take contents DIRECTLY to interstitial fluid where it's diffused into the bloodstream
What are some examples of endocrine glands? - Pituitary gland - Pineal gland - Adrenal gland - Thyroid gland
What are endocrine glands very dependent on? The cardiac system, that is why they are so VASCULAR.
What does a hormone absolutely need for it to bind to a target cell? Receptors
Why are receptors so necessary? Because that is the middle man between the hormone and what it wants to effect. There must be receptors to connect the hormone to the target cell.
What is down-regulation? When there is too much of a hormone, the number of receptors DECREASE.
What does it mean when there is a down-regulation of a hormone? The target cells are LESS SENSITIVE to a hormone
What do synthetic hormones do? Block the receptor that disallows the hormone to go through the normal functions
What are circulating hormones? Hormones that go from secretory cells --> ISF --> Blood
How are circulating hormones inactivated and excreted? Inactivated by the LIVER Excreted by the KIDNEYS
What are local hormones? Hormones that either act on neighboring cells or on the SAME cell that secreted it
What piece of information stands out about local hormones? They do NOT immediately enter the bloodstream
What are paracrine hormones? Hormones that act on neighboring cells
What are autocrine hormones? Hormones that act on the same cell that secreted it
What types of hormones have a larger abundance? Circulating hormones
Which type of hormones stay in effect longer? Circulating hormones
Which type of hormones are inactivated quickly? Local hormones
What are 3 types of lipid-soluble hormones? - Steroid hormones - Thyroid hormones - Nitric oxide
What are steroid hormones? They are derived from cholesterol so they are very unique due to the different chemical attachments?
What is the result of steroid hormones having different chemical attachments? Steroid hormones have several different functions
What is the difference b/w the Nervous and Endocrine systems regarding their target? - The nervous system has a specific target while the endocrine system's target is a lot more broad
What characteristic makes a hormone a hormone? For a chemical to be a hormone it has to travel in the BLOOD
What is a characteristic about hormone receptors? They are very SPECIFIC to each and every hormone
What are natriuretic peptides? They are responsible of stretching the heart walls to lower BP
What kind of hormone is histamine? Circulating Hormone
What is a Thyroid hormone? (T3&T4) Synthesized by attaching iodine to tyrosine
What are thyroid hormones responsible for? Elevating all metabolic activity
What is a characteristic of lipid-soluble hormones? They can go straight through the phospholipid bi-layer
Why can the ability of lipid-soluble hormones being able to go straight through the lipid-bilayer be a potential problem? Because then cells become very susceptible to changes like organelle change and basically it has the ability to completely transform cells
What are the different types of water soluble hormones? - Amine - Peptide - Protein - Eicosanoid
How are water-soluble hormones transported in the blood? They flow freely
How are lipid-soluble hormones transported in the blood? They are bound to transport protein
What organ synthesizes the transport protein? Liver
What hormones can be taken by the mouth and why? Steroid and thyroid hormones because since they are lipid-soluble they don't break down during digestion
What hormones must be injected directly to the blood stream? Protein and peptide hormones (insulin) because the digestive enzymes would break down the peptide bonds b/c they're water-soluble hormones
The response to a hormone depends on what? The hormone and the target cell
What is a characteristic about target cells? That they can respond differently to the same hormone
What are the different effects of a hormone? - They can make new molecules - Change permeability of plasma membrane - Transport substance in or out of target - Alter rate of metabolic rate - Contract smooth or cardiac muscle
How does a hormone announce its arrival? It binds to its receptors
Where are the receptors for lipid-soluble hormones? Inside target cells
Where are the receptors of water-soluble hormones? They are part of the plasma membrane of the target cells
What is the 1st step of an lipid-soluble hormone acting on a target cell? The hormone diffuses out of blood, into ISF and into the plasma membrane of the target cell
What is the 2nd step of a lipid-soluble hormone acting on a target cell? The hormone binds to receptor in cytosol and hormone-receptor complex alters gene expression
How does the hormone-receptor complex alter gene expression? By turning some genes of the Nuclear DNA on and some off
What is the 3rd step of a lipid-soluble hormone acting on a target cell? The DNA is transcribed, mRNA leaves nucleus and finds ribosomes to produce new proteins
What is the 4th step of a lipid-soluble hormone acting on a target cell? The new proteins alter the cell's activity to that of the hormone
What is the difference with water-soluble hormones? Because they CANNOT cross a lipid-bilayer they have to bind to receptors on the outer surface of the target cell's plasma membrane
What is the 1st messenger? When the hormone binds to a receptor at the outer surface of the plasma membrane
What is the 2nd messenger? cAMP
What is the 1st step of a water-soluble hormone acting on a target cell? Hormone diffuses out of blood and attaches to receptor on outer surface of membrane. Hormone-receptor complex activates G protein which in turn activates adenylate cyclase
What is the 2nd step of a water-soluble hormone acting on a target cell? Adenylate cyclase converts ATP into cAMP
What is the 3rd step of a water-soluble hormone acting on a target cell? cAMP (2nd messanger) activate protein kinases
What is the 4th step of water-soluble hormone acting on a target cell? The protein kinases phosphorylate cellular proteins which turn some proteins on and some off (ATP donates the phosphate groups and converts to ADP)
What is the 5th step of a water-soluble hormone acting on a target cell? Phosphorylated proteins cause reactions that produce physiological responses
What is the 6th step of a water-soluble hormone acting on a target cell? Phospodiesterase deactivate cAMP which turns off the cell's response
How does the hormone response stop? G protein is not being any further stimulated b/c hormone molecules are NOT binding to receptor, the G protein slowly inactivates which inactivates andenylate cyclase and the hormone response is stopped
What are cascades/chain reactions? Hormones that still have effects even in low concentrations b/c there are steps that amplify the effect
The responsiveness of a target cell depends on what things? - Hormone concentration in blood - Abundance of hormone receptors - Influences of other hormones
What 2 factors give a hormone a more vigorous effect? - A higher level of hormones - Increase in receptors
What is a permissive effect? The exposure to a hormone is required for another hormone to exert its full effects on a target cell
What is a synergistic effect? When 2 hormones act together to establish a greater effect
What is an antagonistic effect? 1 hormone opposes the effect of the other hormone (but it depends on what receptors you activate)
What is the difference between permissive and synergistic? In a permissive effect, only that 1 hormone needs the other. With synergistic effects, both hormones need each other.
How is the ONLY way that hormones can be released? By stimulation
How is hormone secretion regulated? - Signals from NS - Chemical changes in blood - Other hormones
Most regulatory responses are based on what type of feedback? Negative
What is the hypothalamus It is the major link between the Nervous and Endocrine System
Why is the hypothalamus considered the "Master Gland"? Because it synthesizes 9 hormones
What is the pituitary gland? Pea-shaped structure attached to the hypothalamus by the infundibulum and is considered as a half neural and half endocrine gland
What is) the pituitary gland split up into? - Anterior pituitary (adenohypophysis) - Posterior hypophysis (neurohypophysis)
Why is there a hypophyseal portal system only for the adenohypophysis? Because the hypothalamus has releasing and inhibiting hormones that are responsible for stimulating or inhibiting hormones of the anterior pituitary gland
What are somatotrophs? - Human growth hormone - Insulin-like growth factors
What are thyrotrophs? TSH
What are gonadotrophs? - FSH - LH
What are lactotrophs? PRL
What are corticotrophs? - ACTH - MSH (melanocyte-stimulating hormone)
How are the anterior pituitary gland hormones released? They are stimulated by the releasing and inhibiting hormones of the hypothalamus
How are hypothalamic hormones sent to the anterior pituitary? The hypothalamic hormones are in neurosecretory cells that get transported to the ant. pit. by the hypophyseal portal system
What are tropic hormones? Anterior pituitary hormones that act on other endocrine glands
What are the hormones of the Anterior Pituitary gland? - HGH - PRL - LH - FSH - ACTH - TSH -MSH
What does the HGH do? Stimulates secretion of insulin-growth factors (IGFs) that promote, protein synthesis, transcription and translation
What does the TSH do? Stimulates the synthesis and secretion of thyroid hormones in the thyroid gland
What does FSH do? For women: ovaries start development of oocytes For men: testes start testosterone production
What does LH do? For women: ovaries stimulate ovulation For men: stimulate testosterone production
Why can TSH go through lipid bi-layers? Because of its proteinaceous shape
What is dwarfism? Cannot produce or release HGH
What is gigantism? When there is too much HGH secreted before the epiphyseal plate closes?
What is acromegaly? When there is too much HGH being secreted AFTER the epiphyseal plate has closed
What is PRL? Promotes milk secretion by mammary glands
What hormone allows milk to actually be released from the breast? Oxytocin
What does ACTH do? Stimulates the adrenal cortex hormones
What does MSH do? Releases melanin to darken the skin to protect it from harmful UV rays
What does cortisol do? Helps the body deal with stress
How does cortisol get released? The hypothalamus stimulates a corticotropin releasing hormone that gets sent to the Pituitary gland and stimulates the ACTH to stimulate the andrenal glands to secrete cortisol
What is cushing's syndrome? When there is either too much: - CRH - ACTH - Cortisol
What are symptoms of Cushing's Syndrome? - Moon face - Red striations - Thin skin - Poor wound healing
What is Addison's Disease? Defiency in either: - CRH - ACTH - Cortisol - Means they cannot deal with stress properly
What is special about the posterior pituitary hormones? The posterior pituitary gland does NOT produce its own hormones, it just stores and releases the hormones that the HYPOTHALAMUS produced
What are the 2 hormones that are produced by the hypothalamus and released by the posterior pit. gland? Oxytocin and ADH
What does Oxytocin do? - Establish emotive attachment - Enhances smooth muscle contraction in wall of uterus (+ feedback) - Stimulates milk EJECTION from mammary glands
What does ADH do? - Decreases urine production by causing the kidneys to return more water to the blood - Decreases water lost through sweating and contraction of arterioles which increases BP
What stimulates oxytocin? Stretching of the uterus
The thyroid gland contains ______ that produces _______? Thyroid follicles, T3&T4
What do the thyroid hormones do? - Increase BMR - Stimulate protein synthesis - Increase use of fatty acids and glucose for ATP production
T3 and T4 are what kind of hormones? Lipid-soluble hormones
What is the other kind of follicular cells? Parafollicular cells (C cells) that secrete Calcitonin which build bone and lower blood calcium levels (osteoblasts take Calcium make bone)
What are the 2 lobes of the thyroid gland connected by? The isthmus
What does the bird flu cause? A hyperrelease of thyroxin's
What type of effect would the thyroid hormones be considered as? Permissive effect
What does vasodilation do in regards to ADH secretion? Allows evaporation and gets rid of the heat due to perspiratoin
How is the secretion of the thyroid hormone controlled? - Thyrotropin-releasing hormone from the hypothalamus - TSH from the ant. pit. - Situations where an increase ATP demands increase in thyroid hormones (thyroid hormones is what puts the ATP to use)
What is the process of Thyroid hormone regulation? 1.) If T3&T4 levels are low or BMR is low, TRH is stimulated from the hypo 2.) Travels to ant. pit. to stimulate TSH 3.) TSH travels to follicular cells of thyroid glands (endocytosis) 4.) That stimulates the T3&T4 hormones to be produced and sent to the blood (exocytosis) 5.) Elevated levels of thyroid hormones inhibit TRH and TSH
What kind of feedback would thyroid regulation be considered as? Indirect feedback
What is needed for thyroid hormones? Iodine is needed to be transported to the follicles in order to make the thyroxins
What are some iodine deficiency disorders? - Cretinism - Goiter - Exophthalmia
What does the PTH do? - Regulates calcium phosphate and magnesium ions in the blood - Increases number and activity of osteoclasts - Elevates reabsorption of blood calcium - PTH BREAKS DOWN BONE
What happens if there is too much secretion of PTH? - Not enough ossification, body becomes cartilaginous - Also causes osteoporosis
What are oxyphil cells? Cells within the parathyroid glands that have no known function
What are the chief cells? Cells in the parathyroid gland that get stimulated to release PTH
What happens when there is a high level of blood calcium levels? 1.) Thyroid gland gets stimulated to secrete Calcitonin from its parafollicular cells 2.) It inhibits osteoclasts and stimulates osteoblasts to take the Ca+ and put it toward bones
What happens if there is a low level of blood calcium? 1.) The parathyroid hormone will be stimulated to secrete PTH 2.) Will inhibit osteoblasts and stimulate osteoclasts to break down bone and increase blood Ca levels 3.) PTH also stimulates the release of Calcitriol from the kidneys which reabsorbs Ca from food
The adrenal cortex (outer region of adrenal gland) secretes what hormones? - Aldosterone - Cortisol - Androgens
What does Aldosterone do? Retains Na by dumping K to elevate BP
What does cortisol do? Deals with stress
What are androgens? Sex hormones that more readily build testosterone and have masculinizing effects
What is DHEA and what does it do? It is meant for females to give them some testosterone if they are deficient
What happens if a man uses DHEA? He can lose his hair
What does the adrenal medulla consist of? Epinephrine and Norepinephrine which intensifies sympathetic responses
What are glucocorticoids? Steroid hormones in the adrenal medulla that help with glucose homeostasis
What are mineralcorticoids? Help with mineral homeostasis
What is Addison's disease? When there is a deficiency in secretion of adrenal hormones
What is precocious puberty? When young children develop secondary sex characteristics
What is the pancreas? Both an endocrine and exocrine hormone
What do 99% of pancreatic cells produce? Digestive enzymes
What kind of cells does the Islets of Langerhans produce? - Alpha cells - Beta cells - Delta cells - F cells
What do alpha cells do? They secrete glucagon which RAISES blood sugar
What do beta cells do? They secrete insulin, which LOWERS blood sugar
What do delta cells do? - Secrete somatostatin - Inhibit both insulin and glucagon
What do F cells do? - Secretes pancreatic polypeptide - Inhibits somatostatin and secretion of digestive enzymes
What is the exocrine function of the islets of Langerhans? Contains acini which contains digestive enzymes to breakdown food
What is the endocrine function of the pancreas? Pancreatic islets that contain insulin and glucagon
What do hormones FSH and LH do? - Regulate menstrual cycle - Maintain pregnancy - Prepare mammary glands for lactation - Maintains female secondary sex characteristics
What does inhibin do? Inhibits FSH
What hormone is produced during pregnancy and what does it do? Relaxin- allows pubic symphysis to become stretchy
What does the pineal gland secrete? Melatonin which contributes to circadian rhythm
When is more melatonin liberated? During darkness
What helps an individual get more melatonin? Being in contact with full spectrum light
What is Seasonal Affective Disorder? Causes an individual to have depression due to the low amount of melatonin in their system which causes them not to get enough sleep
What does the thymus do? It secretes different thymosins that help with T cell maturation and helps with immune response
What happens to the thymus as a person gets older? It involutes meaning it gets smaller and loses its function
What are the 2 kinds of stress? - Eustress- helpful stress - Distress- bad stress
What happens when a person is going through stressful conditions? The body initiates a stress response called general adaption syndrome (GAS)
What is the first stage of GAS? Initial fight or flight response where Epinephrine, norepinephrine, and cortisol are secreted
What is the second phase of GAS? Slower resistance reaction; the body begins to run out of cortisol
What is the 3rd phase of GAS? Eventual exhaustion; the body completely runs out of cortisol and there is a homeostatic imbalance, potentially causing death