Endocrine System Flashcards
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How does the endocrine system use chemicals to carry messages?
-hormones secreted directly into bloodstream
-travel long distances to reach targets
-body reacts more slowly to changes
What are hormones?
chemical messengers produced by endocrine glands and secreted directly into blood vessels
-only produce effects when they bind to their specific receptors in or on cells
Peptide hormone
-hydrophilic chains of amino acids
-receptors located on cell membrane of target cells
Steroid hormones (lipids)
-synthesized from cholesterol
-hydrophobic so attach to transport protein to make a bound protein that is hydrophilic
Monoamine hormones
-hydrophobic or hydrophilic
(derived from AA and retain in amino group)
-receptors for catecholamines located on cell membranes
-receptors for thyroid hormones located in the nucleus
What is activity of a gland affected by?
feed back regulation
Negative Feedback
activity is decreased by rising levels of hormone
Positive Feedback
activity increased by rising levels of hormone
What does the hypothalamus do?
controls activities of pituitary gland like appetite control, body temp regulation, etc
What happens in the hypothalamus?
-modified neurons secrete releasing and inhibiting factors into portal blood vessels
-along with ANTIDIURETIC HORMONE (ADH) and OXYTOCIN
What happens to ADH and oxytocin?
transported to posterior pituitary for storage then released into bloodstream by nerve impulses from hypothalamus
Pituitary Gland
“Master Endocrine Glad”
- has anterior and posterior
Anterior pituitary
produces hormones when stimulated
-embryonically from glandular tissue
-rostral
Posterior pituitary
stores and released hormones
-embryonically from nervous tissue
-caudal portion
What hormones does anterior pituitary hormones?
- Growth hormone
- Prolactin
- Thyroid-stimulating hormone
- Adrenocorticotropic hormone
- Follicle stimulating hormone
- Luteinizing hormone
- Melanocyte stimulating hormone
Growth Hormone (GH)
-promotes body growth in young animals
-helps regulate metabolism of proteins, lipids, and carbohydrate in all body cells
(encourages anabolism (synthesis) of proteins, release of lipids in storage and their catabolism, discourages cells from using carbohydrates)
Prolactin
-helps trigger and maintain lactation
Thyroid Stimulating Hormone (TSH)
-stimulates growth and development of thyroid gland -causes thyroid gland to produce its hormones
Adrenocorticotropic Hormone (ACTH)
-stimulates growth and development of adrenal cortex, and release of some of its hormones
-production regulated by feedback from hormones of adrenal cortex
-can be released quickly as result of stress
Follicle Stimulating Hormone (FSH)
female:
-simulates oogenesis
-stimulates production and secretion of estrogen
male:
-stimulates spermatogenesis
Luteinizing Hormone (LH)
-complete process of follicle development in ovary
-LH in males stimulates interstitial cells to produce testosterone
Melanocyte Simulating Hormone (MH)
associated with control of color changes in pigment cells of reptiles, fish, and amphibians
What hormones does the posterior pituitary store?
- antidiuretic hormone
- oxytocin
(hormones from hypothalamus are transported along nerve fiber, and stored in nerve endings)
Antidiuretic Hormone (ADH)
-aka vasopressin
-helps prevent diuresis
-released when hypothalamus detects dehydration
Oxytocin
uterus:
-induces uterine contractions at breeding/parturition
mammary glands:
-stimulation of teat by nursing or milking, causes oxytocin to be released
-causes movement of milk down
Thyroid gland
-2 lobes on either side of larynx (R/L); lobes may be connected by isthmus
-composed of tens of thousand tiny follicles which store thyroid hormone precursor
-only endocrine that stores large amount of hormone precursor for later use
2 hormones produced in thyroid gland follicles
-thyroid hormone
-calcitonin
Effects of thyroid hormones
-regulates metabolic rate of all body’s cells
-affects metabolism of proteins, carbs, lipids
-necessary for normal growth and development of young animals
Calcitonin
-produced by C cells b/w thyroid follicles
-helps maintain blood calcium levels
-prevents hypercalcemia by encouraging excess calcium to be deposited in bones
Parathyroid hormone
-produced by parathyroid glands
-helps maintain blood calcium homeostasis
-exerts the opposite effect of calcitonin; prevents hypocalcemia
Adrenal Glands
-located near cranial ends of kidneys
-2 glands: adernal cortex and medulla
Adrenal Cortex (Superficial)
-controlled by ACTH from anterior pituitary
produces:
1. glucocorticoids
2. mineralcorticoids
3. sex hormones
Glucocorticoids
-cause hyperglycemic effect
-help maintain blood pressure
-help body resist effects of stress
ex: cortisone, cortisol
Mineralcorticoids
regulate levels of electrolytes
ex: aldosterone
Sex hormones
androgens and estrogens
Adrenal Medulla (inner)
- resembles nervous tissue
-produces epinephrine and norepinephrine
Pancreas
-located near abdomen near duodenum
-has both exocrine and endocrine functions
Endocrine component of Pancreas
Pancreatic Islets
-alpha cells: glucagon
-beta cells: insulin
-delta cells: somatostatin
Exocrine component of Pancreas
produces digestive enzymes
Pancreatic hormones
insulin and glucagon
Insulin
lowers blood glucose levels
-causes glucose in blood to be absorbed into body cells
Glucagon
raises blood glucose levels
-stimulates liver cells to convert glycogen to glucose, glycogenesis
Somatostatin
inhibits the release of pancreatic hormones
Common disease of pancreas
- Diabetes mellitus into hyperglycemia
-cats more like type 2, can revert
-dogs more like type 1 - Pancreatitis
Gonads
reproductive organs: testes and ovaries
Testes
-seminiferous tubules: spermatogenesis
-interstitial cells: produce androgens (testosterone)
Ovaries
-produce over and hormones
-cycles controlled by FSH and LH
-hormones produced: estrogens, progestins, relaxin
Estrogens
produced by follicle cells
negative feedback loop
Progestins
-group of hormones produced by corpus luteum
-principal progestin = PROGESTERONE
Progesterone is
necessary for pregnancy to be maintained
Relaxin
-relaxes ligaments surrounding birth canal
-mammary development
-produced by CL, placenta or uterus
Kidneys produce
erythropoietin
-stimulated by hypoxia
-increases production of red blood cells
-increased O2 level slows down production
Deficiency of erythropoietin
anemia often accompanies kidney disease or failure
Stomach produces
gastrin
-produced in stomach wall and acts upon the stomach wall
-secretion stimulated by the presence of food
What does gastrin do?
-gastric stomach glands to secrete hydrochloric acid and digestive enzymes
-encourages muscular contractions of stomach wall
Small intestine produces what hormones?
- secretin: stimulates pancreas to secrete fluids to neutralize acidic chyme
- cholecystokinin: stimulates pancreas to release digestive enzymes
(in response to presence of chyme in duodenum)
both slow down movement of chyme and stimulates gall bladder to sent bile to s.i.
Placenta produces hormones
to support and maintain pregnancy
-estrogen
-progesterone
-chorionic gonadotropin
-relaxin
Thymus
large organ in young animals, atrophies later in life
Thymosin and thymopoietin
cause primitive cells in thymus to transform into T-lymphocytes
Pineal Body
-influences body’s biological clock
-produces melatonin
Prostoglandins
“tissue hormones”
hormone like substance derived from unsaturated fatty acids
