65 Cards in this Set
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Endocrine system
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the body's second great regulatory system
* An integrated system of small organs that involve the release of extracellular signaling molecules known as hormones
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What does the endocrine system do?
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-regulates cellular activities by means of chemical messengers called hormones
-these hormones can act at site independent of secretion and have short and long-term regulatory functions
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How does this differ from the nervous system?
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1. neurons directly innervate tissue
2.stimulation is direct and immediate
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Major endocrine organs
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1. Hypothalamus: has neural and endocrine functions and releases hormones
2.Pituitary Gland: storage and regulation site for secretion of other hormones
3.Thyroid and Parathyroid
4.Pancreas
5. Adrenal Glands
6. Gonads
7. Other Tissues
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Other Tissues and Organs that produce hormones
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adipose cells
pockets of cells in wall of small intestine (leptin and secretin)
stomach (gastrin and HCL)
kidneys
Heart
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Hormones
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chemical messengers secreted by cells into extracellular fluids that affect other parts of the body
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Hormones Function
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1. alters membrane permeability
2. regulates metabolic activity
3. Activates/deactivates/ inhibits
4. enzyme activity
5. Stimulates mitosis
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Characteristics of Hormones
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-lag times ranging from seconds to hours
-Tend to have prolonged effects
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Classification of Hormones
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1. Amino acid-based: 1 or more amino acids (most are water soluble except thyroid hormones)
2. Steroids: derived from cholesterol (no WS ex: adrenal and gonadal glands)
3.Eicosanoids: biologically active lipids with LOCAL hormones-like activity
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Autocrines and Paracrines
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autocrines: chemicals (not hormones) that exert effects on the same cells that secrete them
Paracrines: locally acting chemicals (not hormones) that affect cells other than those that secrete them
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Amino Acids
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Amines
Peptides
Protein hormones
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Steroids
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gonadal (ex: testosterone)
adrenocortical hormones
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Eicosanoids (not really hormones)
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leukotrienes
prostaglandins
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How do hormones exert a biological effect of tissue?
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RECEPTORS are vital for activation
1. membrane bound (surface): water soluble
2.Intracellular (inside cell): not soluble
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Why do the same hormones affect some tissues/organs differently ?
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Target Cell Specificity
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How do we regulate Hormones activity
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1. Hormones concentration: rate of release and inactivation and removal based on volume
2. Receptor Concentration: cells can increase or decrease the number of receptors expressed
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1/2 life
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the time required for a hormone's blood level to decrease by half
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How are hormones removed from blood?
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degrading enzymes
-kidneys and liver
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Three Types of Hormone Interaction
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1. Permissiveness: one hormone cannot exert effects w/o another (ex: GH and thyroid hormone)
2.Synergism: more than one hormone produces same effect on target cells
3. Antagonism: one or more hormones opposes action of another (insulin and glycogen)
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How are Endocrine Hormones regulated?
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1. Humoral Stimulus: capillary blood (Ca2+/ glucose) stimulates secretion of hormones (PTH increases Ca2+ levels/liver> glucose/ pancreas> insulin)
2. Neural stimulation: regulated by direct nervous system input (adrenal medulla--> E and NE)
3.Hormonal regulation: regulated by hormones …
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Hypothalamus
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-midbrain
-connects to pituitary gland by infundibulum (stalk) and is located within cave-like bone called ?
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Neurohypophysis
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1. posterior lobe (neural tissue)
2. and infundibulum
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How does hypothalamus connect to posterior/ anterior pituitary gland?
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posterior: nerves/ neurons --> strictly storage
anterior: no neural connection just VASCULAR
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Adenohypophysis
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anterior lobe made out of glandular tissue
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Hypophyseal Vein Portal System
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1. primary capillary plexus (infundibulum)
2. Hypophyseal plexus
3.Secondary capillary plexus (where anterior pituitary hormones are secreted)
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Anterior pituitary Gland
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REAL pituitary gland: synthesizes and secretes a number of hormones
1. Growth hormones
2. thyroid stimulating hormone
3. adrenocorticotropic hormone
4. Gonadotropins
5. Prolactin
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Growth Hormone
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-produced by somatotropic cells of anterior lobe
-stimulates most cell division; specifically target bone and skeletal muscle
-promotes protein synthesis and encourages use of fats for fuel
-most effects are mediated by Insulin-like growth factors (IGFs)
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GH is regulated by Antagonistic hypothalamic hormones
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-Growth hormone-releasing hormone (GHRH): stimulates anterior pituitary gland to release GH (positive biofeedback)
-Growth hormone-inhibiting hormone (GHIH): produced by hypothalamus inhibits anterior pituitary from releasing GH (neg. feedback)
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Directs effects of GH
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1. anti-insulin actions : releases glucose from liver by breaking down glycogen and stopping cells from reuptake
2. Increases lypolysis: breaking down fats for energy
3. Liver and other tissues: like insulin-growth factors (IGFs)
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Indirect effects of GH
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1.GH acts through IGFs to indirectly increase cartilage formation and skeletal bone growth
2.Increases protein synthesis and cell growth
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GH deficiency
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Infant= hypoglycemia
Childhood=pituitary dwarfism (muscles and bones)
Adult=loss of lean tissue mass (more fat) ; not as much of an effect because epiphyseal plate is closed
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GH excess
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childhood=pituitary gigantism (up to 8ft)
adults=Acromegaly (enlargement of extremities)
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Thyroid Stimulating Hormones (TSH)
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-stimulates normal development of secretory activity of thyroid
-triggered by hypothalamic peptide thyrotropin-releasing hormone (TRH)
-rising blood levels of thyroid hormone act on pituitary gland & hypothalamus to block release of TSH (neg. feedback)
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Adrenocorticotropic Hormone (ACTH)
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-stimulates adrenal cortex to release corticosteroids (cortisol)
-triggered by hypothalamic corticotropin-releasing hormone (CRH) in daily rhythm
-Internal and external factors such as fever, hypoglycemia, and stressors can trigger release of CRH
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Gonadotropins
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1. follicle stimulating hormone FSH: stimulates gamete (egg or sperm) production
2.Lutenizing hormone (LH): promotes production of gonadal hormones (estrogen and testosterone)
*triggered by gonadotropin-releasing hormone (GnRH) during/after puberty
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Negatuve feedback of gonadotropins
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testosterone, progesterone, and estrogen will inhibit the hypothalamus from releasing GnRH
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Deficiency of gonadotropins?
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failure of sexual maturation and possible infertility
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LH & FSH is females/males
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F- LH & FSH cause maturation of ovarian follicle; LH alone triggers ovulation (expulsion of egg from follicle) and promotes synthesis and release of estrogens and progesterone
M-LH stimulates interstitial cells of testes to produce testosterone
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Prolactin
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-in females stimulates milk production by breasts
-triggered by hypothalamic prolactin-releasing hormone (PRH)
-inhibited by prolactin-inhibiting hormone (PIH) or dopamine (neg. feedback)
-blood levels rise toward end of pregnancy and suckling
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Deficiency/overproduction in Prolactin
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deficiency-poor milk production
overproduction
males=impotence and breast enlargement
females=inappropriate milk production
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The Posterior Pituitary Gland
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1.oxytocin and ADH
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oxytocin
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-stimulates uterine contraction
-positive feedback mechanism
-triggers milk ejection "LET DOWN" reflex
-"cuddle hormone" --> may have role in sexual arousal
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ADH (antidiuretic hormone)
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-helps to avoid dehydration
-prevents urine formation
-osmoreceptors
-high osmolarity= ADH preserves water
-low osmolarity=ADH not released causing water loss
ALCOHOL inhibits ADH release and causes copious urine output
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Diabetes Insipidus (ADH deficiency)
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abnormal increase in urine output, fluid intake and often thirst
-symptoms: dilute urine; increased urinary frequency (nocturia ) and enuresis (involuntary urination during sleep)
Cause: death of ADH producing cells in hypothalamus
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ADH Overproduction
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-syndrome of inappropriate ADH production (SIADH)
-symptoms:hypoatremia:not enough sodium in the body fluids outside the cells; elevated urine osmolality
-excessive sodium in urine
causes: hypovolemia (low blood volume);ADH-secreting tumor
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Thyroid Gland
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-anterior neck
-butterfly shape
-very vascularized (carotid arteries)
-two lobes (isthmus connects)
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Hormones of Thyroid Gland
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1. Thyroid hormone
2. Calcitonin
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Thyroid hormone
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follicle cells-->produce thyroglobulin--> need iodine (3 atoms) to produce thyrozine (T4) and T3
parafollicular cells(outside)--> make calcitonin
1.Glucose oxidation
2.increasing metabolic rate
3. heat production
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Thyroid Hormone plays a role in ...
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1. maintaing BP
2.Regulates tissue growth (everywhere but RBCs)
3.Developing skeletal and nervous systems
4.maturation and reproductive capabilities
5.Permissive hormone (w/ GH)
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Cretinism (children)
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Symptoms: low metabolic rate, growth retardation, developmental delay
Caused: lack of iodine in maternal diet or genetic factors
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Myxedema (adults)
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Symptoms: low metabolic rate, skin and tissue disorder usually due to severe prolonged hypothyroidism , dry skin and extrememly tired
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Goiter
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-swollen thyroid gland due to lack of iodine in diet and over production of thyroglobulin
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Graves disease
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-hyperthyroid disorder/ autoimmune disease
-Symptoms: inflammation of tissues around eyes causing swelling and bulging (exophthalmos); high metabolic rate; sweating;rapid and irregular heart beat; nervousness; weight loss; protruding eye balls
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Calcitonin
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-regulates calcium level
-humoral stimulus
-Calcium in blood stream-->inhibits osteoclast activity which keeps calcium in bones and reduces it in the blood
-lack of calcium in blood means calcitonin won't work (neg. feedback)
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Parathyroid Gland
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-4 glands total
-cells are arranged in cords containing oxyphil and chiefs cells
-Chief cells secrete PTH
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Parathyroid Hormones
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-raises blood calcium levels (antagonistic to calcitonin)
-no connection in production just antagonistic in function
-Humoral Function (neg. biofeedback ) calcium levels up in blood then parathyroid hormone will NOT be released
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Target Organs of Parathyroid Hormone
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1. bone
2. intestine
3. Kidney: increases Ca2+ reabsorption and promotes activation of Vit D which increases calcium absorption from fluid
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Hyperparathyroidism
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rare and usually results from a parathyroid gland tumor
-calcium is leached from bones and it causes them to soften and deform
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Hypoparathyroidism
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-PTH deficiency
-usually follows parathyroid gland trauma or removal
-hypocalcemia
-results in tetany (loss of sensation, muscles twitches, and convulsions)
-Untreated can lead to paralysis and death
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Adrenal (Suprarenal) Gland
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-2 Glands in 1
1. Adrenal medulla: neural tissue that acts as part of SNS
2. Adrenal cortex: secretes steroid hormones
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Adrenal Cortex
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-Synthesizes and releases steroid hormones called corticosteroids
1. zona glomerulosa --> mineralocorticoids (aldosterone)
2. zona fasciculata --> glucocorticoids (cortisol)
3. zona reticularis--> gonadocorticoids (androgens)
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Mineralocorticoids (Aldosterone Regulation)
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*essential function is to regulate electrolyte (mineral salt) concentrations in extracellular fluids particular Na+ and K+
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Primary Regulators
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1. Blood volume/pressure is low / K+ levels are high
2. kidneys to release Renin which produces Angiotensin II
3. zona glomerulosa of adrenal cortex secretes aldosterone
4. Targets kidney tubules
5. absorp. of Na+ / increased excretion of K+
6.blood volume/pressure increases
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Other Factors: ACTH
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1. Stress
2. hypothalamus secretes MORE corticotropin-releasing hormone (CRH)
3. anterior pituitary releases ACTH into blood
4.zona glomerulosa releases aldosterone
5. kidney tubules/absorop. Na+ and excretion of K+
6. BP up (to deliver nutrients)
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Other Factors: Atrial Natruiretic Peptide (ANP)
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1. Blood pressure/volume high
2. heart
3. Atrial natriuretic peptide (ANS)-- inhibitory effect
4.zona glomerulosa of adrenal cortex releases aldosterone
5. kidney tubules
6.increased absorp. of Na+ and excretion of K+
7.BP increases
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