Endocrine System Flashcards
Endocrine System in homeostasis
- Hormones released into the bloodstream travel throughout the body
- results may take hours but the effects last longer
Nervous System in homeostasis
- Release neurotransmitters locally to excite or inhibit nerve, muscle and gland cells
- Results appear in milliseconds but only brief duration of effects
Exocrine Glands
( exit the body, exo)
- Secrete their products into ducts that carry the secretions into body cavities or body surface
- Include sweat, oil mucus, and digestive glands
Endocrine Glands
(enters body, endo)
- Secret ( hormones) into interstitial fluid surrounding the cell instead of into ducts
- Includes pituitary, pineal glands thyroid, parathyroid, adrenal
- not endocrine but secrete hormones: Hypothalamus, thymus, pancreas, ovaries, testes, kidneys, stomach, liver, small intestine, skin, heart, and placenta
General functions of hormones
Help regulate:
- extracellular fluid
- metabolism
- biological clock
- contraction of cardiac and smooth muscle
- glandular secretion
- some immune functions
- growth and development
- reproduction
The role of hormone receptors
- Hormones attach/bind to ONLY their receptors
- like little flags that bind only to their specific hormone, will not bind to any other receptors besides their cells receptors
- Constantly being synthesized and broken down in response to hormone levels or effect
Circulating Hormones
- Most endocrine are circulating hormones
Use blood as a highway - act on distant targets
- travel and linger in the blood
Linger in the body and effects last minutes to hours
Local Hormones
Act locally on neighboring cells or same cell that secreted them without entering the bloodstream
two types
- paracrines and autocrines
Inactivated quickly
Chemical class of hormones
Soluble in lipids and soluble in water
Solubility affects the drug delivery, mechanism of action, and need for transport proteins
Liquid- soluble hormones
Most bind to transport proteins to be carried in blood
this makes them temporarily water soluble, this increases their solubility in blood
-Has carbon rings
-usually end in -one or -ol
Steroids: Aldosterone, androgens, calcitriol, cortisol, estrogens,proestrogene testosterone
Thyroid: T3 and T4
Nitric oxide: NO gas
Water-soluble hormones
Most circulate in plasma in a free unattached form
Amine hormones:
Peptide and Protein
Eicosanoids
Hormone transporting the blood
water-soluble hormones circulate in watery blood plasma.
Lipid- soluble hormones ( steroids and thyroid) must attach to transport proteins synthesized by the liver
What are the general mechanisms of hormone action
Hormones bind to cell surface or receptors inside target cell
Cells then:
-synthesize new molecules
-change permeability of membrane
-alter rates of reactions
Each target cell responds to hormones differently
Actions of lipid soluble hormones
Steps
- Diffuse through membrane
- Bind to the receptor( that is inside of target cells) in cytosol/nucleus turning on/off specific genes, aka alters gene expression
- forms new RNA that directs synthesis of new proteins
- New protein alters cells activity and causes response
Action of water soluble hormones
steps
- Can’t diffuse through plasma membrane
- the hormone acts as the first messenger
- Receptor proteins activate g-protein “gets the ball rolling”
- g-protien activates adenylate cyclase to convert atp to cAMP (energy)
- cAMP now the second messenger, activates kinases in the cytosol to speed up/slow down physiological responses
- Phosphodiesterase inactivates cAMP quickly and the cell response is turned off unless new hormone molecules arrive
Permissive effect
A second hormone strengthens the effects of the first
you pushing a wall and someone coming to push it too
Synergistic effect
Two hormones acting together for greater effect
working together
Antagonistic effects
Two hormones with opposite effects
one turns something off the other turns it off, one enhances the other decreases the action
Negative feedback control
Most common
Change is reversed, restoring homeostasis
Positive feedback control
The change produced by the hormone causes more hormone to be released
Hypothalamus
- master endocrine gland, the puppeteer
- located in the brain above the pituitary gland and controls it
- It’s hormones control other endocrine glands
- Involved in behavior (rage, hunger, thirst, fear, sex)
- Controls all aspects of growth, development, metabolism, and homeostasis
- Receives input from the cerebral cortex, thalamus, limbic system, and internal organs
Hypothalamus role with Pituitary Gland
- Controls pituitary gland
- synthesizes 9 different hormones
- All hormones act on anterior pituitary EXCEPT the posterior pituitary hormones
What 9 hormones does the hypothalamus synthesize in the pituitary
- Posterior pituitary
- releasing
- inhibiting
posterior: OT and ADH: Stored and released from posterior pituitary
releasing: GHRH, TRH, GnRH, PRH, CRH: Control release of hormones by the anterior pituitary
inhibiting: GHIH and PIH: inhibit the release of hormones by the anterior pituitary
Pituitary Gland
- Pea shaped
- In sella turcica of the sphenoid bone
- Has 2 lobes, anterior and posterior
- Secretes several hormones that control other endocrine glands
How does blood flow to the Anterior Pituitary
- The controlling hormones enter the blood, RH and IH
- They travel through portal veins
- Enter the anterior pituitary at the capillaries
Hormones of the Anterior Pituitary gland and the cells that produce them
- Human growth hormone secreted by somatrophs
- Thyroid-stimulating hormone secreted by thyrothrops
- Follicle-stimulating hormone & Luteinizing hormone secreted by gonadotrophs
- Prolactin secreted by lactotrophs
- Adrenocorticotropic hormone & Melanocyte-stimulating hormone secreted by corticotrophs
What is the human growth hormone
-common target cells
Increases the synthesis of insulin-like growth factors that are local or that enter the bloodstream
- stimulate the breaking of fat used for ATP
- Common target cells are the liver, skeletal muscle, cartilage and bone
Regulation of hGH
- If the cell growth is too much:
GHRH decreases and GHIh increases
-If the cell growth is too slow:
Increase GHRH
Steps of Excess of Growth hormone ( Diabetogenic )
- raises blood glucose concentration
- pancreas releases insulin continuously
- results in pancreas getting tired of doing so, so beta-cell burnout occurs ( stops making insulin)
Diabetogenic effect
When beta-cell burnout occurs, insulin stops being created so this causes one to have diabetes Mellitus( type 2 ) due to no insulin activity.
Posterior Pituitary and 2 hormones
- Smaller portions
- Does NOT synthesize hormones but does store and release them
- Consists of axon terminals of hypothalamic neurons
- Relaesed by exocytosis
- Store and relases only 2 hormones: Oxycotin (OT) and Antidiuretic Hormone (ADH)
Oxycotin (OT)
- Two target tissues in pregnant women
- Uterus and mammary glands
- Enhances uterine muscle contraction during delivery
- Causes muscle contraction and milk ejection after delivery
- Regulated by positive feedback
Antidiuretic Hormone ( ADH)
-Known as vasopressin
-Functions include:
Stimulates water reabsorption by the kidneys
Decrease urine productions/volume & conserve water aka sweating
Increases BP by causing smooth muscle contraction in blood vessels
Regulation of ADH
Negative feedback
Dehydration, stress, pain, trauma, anxiety, Ach, Nicotine, Morphine, Overhydration, alcohol, caffeine
Thyroid gland Histology
Butterfly shaped
Above the larynx
4 Main parts
Colloid: The fluid inside of the cell
Follicular cells: surround the colloid, produce t3 and t4
Parafollicular cells: In between the follicular cells, produce calcitonin
Follice: The sac of stored hormone, (Overall cell)
Lined witht he follicular cells and is filled with colloid
Formation of Thyroid Hormone T3 and T4
- Make TGB in cell
- Iodinize Colloid
- Add Iodine to TGB to make t3 and t4
Thyroid Hormones
T3 and T4 - Responsible for increasing: Protein synthesis lipolysis metabolic rate regulate oxygen use and basal metabolic rate, cellular metabolism, and growth and development
Calcitonin ( CT ) & Secretion
Responsible for lowering blood levels of calcium and phosphates
builds bone
Secretion is controlled by calcium levels in the blood
Parathyroid gland
Found on Posterior side of Thyroid
Has 2 main parts
Oxyphill cells: Surround the principal/chief cells
Principal/Chief cells: Produce PTH hormone, darker ones
Parathyroid Hormone
Regulates homeostasis of calcium and phosphate by Increases blood calcium levels and decreasing blood phosphate level
Increases activity of osteoclasts
The opposite function of Calcitonin
Adrenal Glands
Superior to the kidneys Pyramid shaped 2 Regions to it -Adrenal cortex ( Outter part) 3 zones -Adrenal Medulla (inner part) 3 parts -Capsule: Outter layer -Cortex: Yellow second layer -zona glo., fas., ret. -Medulla: Inner layer ( the middle)
Androgens
usually have minimal effects in the male but more pronounced effects in the female]
May contribute to sex drive, still unknown
Made in Zona Reticularis
Adrenal Medulla
consists of hormone-producing cells, called chromaffin cells, which surround large blood-filled sinuses
Two major hormones
Epinephrine: Causes fight or flight behaviors
Norepinephrine: Stimulated by Ach
Pancreas
classified as both an endocrine and an exocrine gland Contains Pancreatic islets and 95% made up of acini cells 4 hormones -Insulin -Glucogon -Somatistatin Pancreaticpelipeptide
Thymus
Located behind the sternum between the lungs
Stress response
Eustress and Distress
3 stages:
initial flight or fight, slower resistance reaction and eventually exhaustion
What is a hormone
A molecule that is released in one part of the body but regulates the activity of cells in other parts of the body2
What does the Endocrone system do
Controls body activities by releasing hormones
Down regulation
if there is enough hormone present in the cell then the number of receptors decrease
Up regulation
If the hormone is deficient, the number of receptors will increase
Two types of local hormones
Paracrine: Act on neighboring cells (insulin )
Autocrine: Act on the same cell that secreted them are inactivated quickly (cells in the immune system)
Steroid Hormones
Lipid Soluble
Derived from cholesterol. Each is unique
Thyroid Hormones
Lipid soluble
T3 and T4
Synthesized by attaching iodine to the amino acid tyrosine
Nitric Oxide
Lipid Soluble
Both a hormone and a neurotransmitter.
Amine Hormones
Water soluble
serotonin, melatonin, histamine,epinephrine, norepinephrine
Peptide and Protien hormones
Water soluble
Amino Acid polymers
hypothalamic RH and IH
Eicosanoid Hormones
Water soluble
Prostaglandins and leukotrienes
Hormone Interactions
The responsiveness of a target cell to a hormone depends on the hormone’s concentration, the abundance of the target cell’s hormone receptors, and influences exerted by other hormones.
The three interactions are permissive,synergistic and antagonistic
The control of hormone secretion
Release of hormones occur in short bursts, with little or no secretion between bursts.
The regulation normally prevents overproduction or underproduction of the given hormone to help maintain homeostasis
Hormone secretion is regulated by
Signals from the nervous system, chemical changes in the blood and other hormones
GH
Growth Hormone
Stimulates general body growth and regulates aspects of metabolism
TSH
Thyroid Stimulating hormone
Regulated by TRH and GHIH from the hypothalamus
Controls the secretions and other activities of the thyroid gland
FSH & LH
Follicle stimulating hormone Regulated by GnRH; no IH and Luteinizing hormone Regulated by GnRH; no IH
Both act on the gonads.
In men, they stimulate testes to produce sperm and secrete testosterone.
In women, they stimulate the ovaries to mature oocytes and to secrete estrogen and progesterone
PRL
Prolactin
Regulated by PRH, TRH, PIH
Initiates the production of milk and mammary glands
ACTH
Adrenocorticotropic
Regulated by CRH;no IH
Stimulates the adrenal cortex to secrete glucocorticoids such as cortisol
MSH
Melanocyte Stimulating hormone
Regulated by CRH,PIH
increases skin pigmentation in frogs, unknown for humans
What controls Thyroid Hormone Secretion
Controlled by the level of iodine in the thyroid gland and by negative feedback systems involving both the hypothalamus and the anterior pituitary gland
Control of Secretion of Calcitonin and Parathyroid Hormone
Blood calcium levels directly controls the secretion go both calcitonin and parathyroid hormone via negative feedback
PTH increases the number and activity of osteoclasts, increases the rate of Calcium ions and Mg+2 from reabsorption from urine and inhibits the reabsorption of HPO4-2 so more is secreted in the urine, and promotes formation of calcitriol, which increases the absorption of calcium ions, Mg+2,and HPO4-2 from the GI tract.
Adrenal Cortex & hormones
has 3 zones
The zona glomerulosa (outer zone) secretes mineralocorticoids
The zona fasciculata (middle zone) secretes glucocorticoids.
The zona reticularis (inner zone) secretes androgens
Adrenal Gland Hormones
Aldosterone: made in Zona Glomerulosa
increase sodium and water reabsorption and decrease potassium reabsorption, helping to regulate sodium and potassium levels in the body
Secretion is controlled by the renin-angiotensin pathway and blood level of potassium
Cortisol: Made in Zona Fasciculata
promote breakdown of proteins, formation of glucose, lipolysis, resistance to stress, anti-inflammatory effects, and depression of the immune response.
Secretion is controlled by CRH and ACTH from the anterior pituitary
Pancreatic Islets & cell types
4 types
Alpha cells: constitute about 17% of islet cells. secrete glucagon which increases blood glucose levels.
Beta cells: Constitute about 70% of islet cells. secrete insulin which decreases blood glucose levels.
Delta cells: constitute about 7% of islet cells. secrete somatostatin, which acts as a paracrine to inhibit the secretion of insulin and glucagon.
F-cells: constitute the remainder of islet cells, secrete pancreatic polypeptide, which regulates release of pancreatic digestive enzymes.
Ovaries
located in the pelvic cavity
produce several steroid hormones, including two sex hormones (estrogens and progesterone) and inhibin and relaxin.
Estogen and Progesterone Hormone
Produced in ovaries
Regulate menstral cycle, maintain pregnancy, and prepare the mammary glands for lactation. Promote enlargement of breast and widening of the hips at puberty and help maintain female secondary characteristics
Inhibin Hormone
Produced in ovaries
Protien hormone that inhibits the secretion of FSH.
Relaxin Hormone
Produced in ovaries
Increases the flexibility of the pubic symphysis during pregnancy and helps dilute cervix for labor and delivery
Testes
Oval glands that lie in the scrotum
Produce 2 main hormones
Testosterone and Androgen
and inhibin
Testosteorne hormone
Stimulates the descent of the testes before birth, regulates the production of sperm and stimulates the development and maintenance of male secondary characteristics
Pineal gland
attached to the roof of the third ventricle, inside the brain
Secrets melatonin
Thymus Gland
Located being the sternum between the lungs
Has a large role in immunity so it secretes several hormones relating to immunity
Thymosin, thymic humoral-factor, thymic factor, and thymopoietin
Thymus gland hormones
promote the proliferation and maturation of T cells, a type of white blood cell involved in immunity
Eicosanoids
Two families
-prostaglandins
-leukotrienes
Found all over the body, except red blood cells, where they act as local hormones.
Synthesized by clipping a 20 carbon fatty acid
Prostaglandins have a wide range of biological activity in normal physiology and pathology
Growth Factors
hormones that stimulate cell growth and division
Examples: epidermal growth factor, platelet-derived growth factor, fibroblast growth factor, nerve growth factor, tumor angiogenesis factors, insulinlike growth factor, and cytokines
Fight or flight Response
The alarm reaction is initiated by nerve impulses from the hypothalamus to the sympathetic division of the autonomic nervous system and adrenal medulla
increase circulation, promote catabolism for energy production, and decrease nonessential activity
Resistance Reaction
initiated by regulating hormones secreted by the hypothalamus ( CRH,GHRH,TRH )
are long-term and accelerate catabolism to provide energy to counteract stress.
Exhaustion
results from dramatic changes during alarm and resistance reactions
caused mainly by loss of potassium, depletion of adrenal glucocorticoids, and weakened organs. If stress is too great, it may lead to death
