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Endocrine System
- Series of ductless glands that secrete hormones
- Hormones travel to regions of body and signal physiological responses
- Slower response than nervous system
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Endocrinology
- The study of hormones and endocrine glands
- Endocrine organs and hormones = system
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Exocrine Glands
- Have ducts
- Secrete onto body surface or into cavity
- Secretions travel directly onto target
- Secretions are fluids, lubricants, enzymes
- Sweat, salivary, mucous
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Endocrine Glands
- Ductless
- Secrete hormones
- Function id regulation, homeostasis
- Hormones dumoed right into bloodstream, act on target cells
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Pure endocrine Organs
Pituirtary Gland, pineal gland, thyroid gland, parathyroid glands, and adrenal gland
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Endocrine organs together in body systems
Pancreas, thymus, gonads, and hypothalamus
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Hormone Classes
Amino Acid (protein) or steroid (lipid)
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Hormone Action
- Circulate through bloodstream and affect only the target cells
- Hormones themselves are just triggers
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Hormone secretion control
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Humoral Stimuli
Respond to changing levels of ions/nutrients in blood
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Neural Stimuli
Respond to nervous system
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Hormonal Stimuli
Respond to hormones from other glands
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Feedback Loops
- Negative= more hormone secretion if level drops
- Positive= more hormone secreted if levels increase
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Pituitary Gland
- 9 major proteins from 2 portions
- All protein hormones
- Small/ round structure
- On stalk below hypothalamus
- 2 glands- anterior (adenohypophysis), posterior (neurohypophysis)
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Adenohypoophysis
- Location- ventral portion under hypothalamus
- Secretions- hormones that regulate growth and secretion of other glands, tissues
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Growth Hormone
Regulates growth of all body cells, promotes cell division
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Melanocyte Stimultaing Hormone
Causes darkening of skin by stimulating melanin
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Follicle Stimulating Hormone
- In females, it regulates monthly development of follicle and egg and secretion of estrogen
- In males, it stimulates testes to create sperm
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Luteinizing Hormone
- Works with FSH
- Females- helps bring out ovulation, formation of progesterone
- Males- stimulates testosterone development and secretion
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Thyroid Stimulating Hormone
Regulates thyroid gland, but hypothalamus alos partially controls
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Adrenocorticotropic Hormone
Promotes functioning of adrenal cortex
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Prolactin
Secreted in both males and females, but functions more in females after birth- response for milk production
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Neuropophysis
- Location- Dorsal
- Is considered part of the brain- has nervous tissue
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Secretions- Pituitary Gland
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Targets/Effects of Pit. Gland
- ADH- kidney= helps to retain water, constricts blood vessels
- Oxytocin- Uterus= contractions, delivery, breast= lactation
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Thyroid Gland
- Location- in anterior neck, inferior to the larynx- just below adam's apple
- Wraps around front of trachea, 2 lobes connected by isthmus, many BVs around it
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Thyroid gland secretions
- Thyroid Hormone- Thyroxine= T4, Triiodothyronine= T3
- Peptide hormone- contains iodine, needed for function
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Secretions cont'd
Calcitonin- targets bones, retains calcium, inhibits osteoclasts
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Parathyroid Glands
Location- 4 tiny glands at top and bottom of posterior surface of each lobe of the thyroid gland
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Parathyroid Secretion
Parathyroid Hormone- protein hormone made by chief cells
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Parathyroid targets
- Bones- increases Ca release
- Small Intestine- increases Ca absorption
- Kidneys- decreases Ca excretion
- Increases Ca in bloodstream, decreases amount in bones
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Adrenal Cortex
- Bulk of gland, controlled by ACTH from anterior pit.
- Secretsover 30 hormones, called corticosteroids
- Location= Cortex
- Secrtes- Aldosterone=mineralocorticoid and Cortisol= glucocorticoid
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Adrenal Cortex Target
- Cortisol targets, liver, muscles
- Aldosterone targets kidney
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Adrenal Medulla
- Controlled by sympathetic NS
- Location- inside portion of gland
- Secretion- Epi. and NE
- Targets all sympathetic target organs
- Effects- reinforces sympathetic mass activation, fight or flight
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Pineal Gland
- Shaped like a pine cone
- Function?
- Location- Roof of 3rd venticle, dorsal to thalamus. dorsal/superior to midbrain(striaight back from eyes)
- Secretes melatonin
- Targets hypothalamus
- Effect- helps regulate circadian rhythms, sleep
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Pancreas
- Both endocrine and exocrine
- Posterior abdominal wall, middle left side
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Pancreas Secretions
- Protein hormones
- Pancreatic islets- responsible for endocrine function (alpha, beta= cell types)
- Glucagon- helps to release fuel into bloodstream- from alpha islets
- Insulin- helps to store glucose/fuel- from beta islets
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Pancreas Targets/Effects
Glucagon signals liver to release glucose from stored glycogen- insulin signals liver to store glucose as glycogen
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Thymus
- Location- farther down trachea from thyroid, rests on top pf preicardial sac in the mediastinum
- In front of aorta, behind sternum
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Thymus Secretion
Thymic hormone- peptide hormone
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Thymus Target
- Lymphoid tissues
- Effect- increase lymphocyte production, especially T cells- help maintain imunity- gland is much larger than in children, regresses in size after puberty
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Gonads
- Females- Ovaries
- Upper pelvic cavity, one on each side of uterus, oval shaped
- Secretes not purely endocrine gland- also produces egg cells, estrogen, progesterone
- Targets most body tissues and growth and development, sex drive
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Gonads
- Males- Testes
- Scrotum
- Secretes androgens
- Produces sperm
- Targets/effects most body tissues, growth and development, sex drive
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Heart
- ANP (atrial natriuretic peptide) decreases excess blood volume, high BP, and Na concentration
- Stimulates kidney for salt secretion
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GI Tract
- Gastrin- released by stomach- stimulates HCI
- Secretin- released by small intestine- stimulates water and bicarbonate
- CCK- released by small intestine- stim. gallbladder, pancreatic juices
- GIP- released by small intestine- inhibits gastric emptying, acid secretion
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Placenta
Influences pregnancy
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Kidneys
- Secrete erythropoietin
- Target/Effect- red bone marrow, stimulates RBC prod.
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Skin
- Precursor to vitamin D
- Produced by modified cholesterol molecules after UV exposure
- Signals Ca absorption from small intestine
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Gigantism (pituitary)
Tumor causes hypersecretion of GH in children
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Acromegaly (pituitary)
Excessive GH secretion after epiphyseal growth plates fuse
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Diabetes Mellitus (pancreas)
- Insufficient insulin OR inability of cells to react to insulin
- Blood sugar is high
- -Type I need insulin injected
- -Type II "adult onset" reduced insulin sensitivity
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Graves Disease (thyroid)
Oversecretion of thyroid hormone (sympathetic)
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Hypothyroidism (thyroid)
Hyposecretion of thyroid hormone (low metabolism)
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Goiter (thyroid)
enlarged thyroid gland due to lack of iodine
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