Chapter 15: Endocrine Flashcards
What is the Endocrine System?
-works together with nervous system to maintain homeostasis -PRIMARY FUNCTION: produce hormones -hormones act on specific target cells to produce specific effects -no ducts
Pancreas
-Exocrine: digestive enzymes -Endocrine: insulin, glucagon
Ovary
-Exocrine: egg -Endocrine: estrogen, progesterone
Testes
-Exocrine: sperm -Endocrine: testosterone
Kidney
-Exocrine: urine -Endocrine: erythropoietin
General Function
-Endocrine: maintain homeostasis -Nervous: maintain homeostasis
Reaction to Stimuli
-Endocrine: slow -Nervous: rapid
Duration of Effect
-Endocrine: long -Nervous: short
Target Tissue
-Endocrine: entire body -Nervous: muscles and glands
Chemical Messenger
-Endocrine: hormone -Nervous: neurotransmitter
Messenger Producing Cell
-Endocrine: endocrine gland -Nervous: neurons
Distance to Target Cell
-Endocrine: long (via bloodstream) -Nervous: short (across synaptic space)
What are Hormones?
-chemical messengers produced by endocrine glands -secreted into interstitial fluid and absorbed into blood vessels -contact all cells in body -produce effects only on cells containing specific receptors -target cell -growth hormone: all cells -Prolactin: mammary tissue
What happens if the Hormone Level is Low?
Appropriate endocrine gland is stimulated to produce more hormone
What happens if the Hormone Level is High?
Stimulation of endocrine gland is reduced and production of the hormone is stopped/reduced
What is the “fight or flight” control of hormone secretions?
Secretion of some hormones is stimulated by sympathetic nerve impulses when an animal feels threatened
What is the Hypothalamus?
-controls pituitary gland -part of Diencephalon section of brain -controls activity of pituitary gland -modified neurons in hypothalamus secrete releasing and inhibiting hormones into portal blood vessels
What are Pituitary Glands?
-2 separate glands with different structures, functions and embryological origins
What are the 2 Pituitary Glands?
-anterior pituitary -posterior pituitary
What is the Anterior Pituitary?
-adenohypophysis -rostral position -stimulated by hypothalamus (portal system) and direct (neg) feedback from target tissues to produce hormones
What is the Posterior Pituitary?
-neurohypophysis -caudal portion -stores and releases hormones produced in hypothalamus (oxytocin, ADH)
What is Growth Hormone?
-aka:somatotropin and somatropic hormone -promotes body growth in young animals -helps regulate metabolism of proteins, carbs and lipids in all body cells
What is the effect of Growth Hormone on protein metabolism?
Encourage anabolism (synthesis of proteins by body cells)
What are the effects of Growth Hormone on carb and lipid metabolism?
-while lipids are broken down via catabolism for energy production, the use of carbs as energy source is discouraged -less glucose is removed from the blood and hyperglycemia occurs -
What is the Hyperglycemia Effect?
Less glucose is removed from the blood and hyperglycemia occurs
What is Prolactin?
-helps trigger and maintain lactation in females -secretion of milk by mammary glands -production continues as long as teat/nipples are stimulated by nursing or milking
What happens when Prolactin stimulation stops?
-milk production stops - mammary gland shrinks to original/ nonlactating size
What is Thyroid Stimulating Hormone (TSH)?
-AKA: thyrotropin/thryropropic hormone -stimulates growth/development of thyroid gland and causes thyroid to produce its hormones
How is secretion of TSH regulated?
-feedback (neg) from thyroid gland -thyroid levels too low: TSH production increases -thyroid levels too high: TSH stops production
What is Adrenocroticotropic Hormone (ACTH)?
-stimulates growth/development of adrenal cortex and the release of some of its hormones
How is ACTH regulated?
-release of CRF from hypothalamus to anterior pituitary through portal system -neg feedback from adrenal hormones and administered cortisones -during sudden stress, ACTH can quickly be released after the hypothalamus is stimulated to send out ATCH-releasing factor to the anterior pituitary via the portal system
What is Follicle Stimulating Hormone (FSH)?
-females: stimulates growth/development of ovarian follicles (where oogenesis occurs) -males: stimulates spermatogenesis in the testes -also stimulates the cells lining the follicles to produce/secrete estrogen -used to super ovulate
What is Lutenizing Hormone (LH)?
-completes follicle development in ovary -increasing amounts of estrogens feedback to the anterior pituitary and caused reduced production of FSH and reduced production FSH and increased production of LH
What happens when LH reaches a peak?
-reaches a peak when fully mature -usually causes ovulation
What happens after ovulation? (LH)
-LH stimulates cells in empty follicle to multiply and develop into corpus luteum (CL) -CL produces progesterone necessary for maintenance of pregnancy
What is Luteinizing Hormone (LH)?
-males: LH stimulates interstitial cells to produce testosterone
What is Melanocyte Stimulating Hormone (MSH)?
-controls color changes in pigment cells of reptiles fish and amphibians -administration of artificially large amounts of MSH to higher mammals can cause darkening of skin from Melanocyte stimulation
What is Posterior Pituitary?
-stores (does not produce)2 hormones produced in hypothalamus -anti diuretic hormone (ADH) and oxytocin -transported from hypothalamus to post pituitary along axons and stored in nerve endings
What is Antidiuretic Hormone (ADH)?
-helps prevent dieresis -receptors in hypothalamus detect changes in osmotic pressure of blood -generates nerves impulses from hypothalamus
What is Oxytocin?
-uterus: causes concentration of myometrium at breeding and at birth -induces contractions of sperm to eggs -stimulates uterine contractions to help birthing -mammary glands: causes milk letdown to lower parts of gland -stimulation of teat/nipple by nursing or milking causes oxytocin release into blood stream -causes contractions of cells around mammary gland - forces milk into lower parts of gland
What is the Thyroid Gland?
- consists of 2 lobes on each side of larynx
- composed of lots of follicles
- each is a sphere of cuboidal gladular cells surround colloid, which contains thyroid precursor for later use
- Produces 2 hormones: Thyroid hormone and Calcitonin
What is the Thyroid Hormone?
- actually 2 hormones
- T3 (triiodothyronine
- T4 (thyroxine)
- produced when TSH from anterior pituitar reaches thyroid gland
- T4 produced in greater amounts, but mostly convereted to T3
- T3 is more potent and main thyroid hormone
What are the effects of Thyroid Hormones?
- Calorgenic effect: regulates metabolic rate (BMR)
- allows animal to generate heat and maintain internal body temp
- increases with exposure to cold
- increases metabolic rate, generates more heat
What effects do the Thyroid Hormones have on Proteins?
- encourages synthesis of proteins
- if energy sources arent enough, they can catabolize proteins
What effects do the Thyroid Hormones have on Carbs?
- hyperglycemic effect
- helps maintain homeostasis of blood glucose level by preventing it from dropping too low
What effect does the Thyroid Hormone have on Lipids?
-encourages their catabolism
What is Hypothyroidism?
- inadequate amount of hormone produced
- occurs in middle age dogs
What are the symptoms of Hypothyroidism?
- alopecia
- dry skin
- lethargy
- reluctance to exercise
- weight gain/decreased metabolism
- seeking out sources of heat
What is Hyperthyroidism?
- too much thyroid hormone produced
- most common in cats
What are symptoms of Hyperthyroidism?
- nervousness/irritability/excitability
- weight loss
- polyphagia, but no weight gain
- tachycardia
- vomiting
- diarrhea
- polyuria
- polydipsia
How is Hyperthyroidism treated?
- surgically by removing thyroid gland
- radioactive treatment
- drugs to supress thyroid production
What is a Goiter?
- non cancerous, non inflammatory enlargement of the thyroid gland
- result from iodine-deficent diet
- anterior pituitary tries to compensate by making more TSH, but overstimulates gland
- can be treated with iodine supplements
What is Calcitonin?
- produced by C cells (parafollicular cells) located between thyroid follicles
- maintains homeostasis of blood calcium levels
- prevents hypercalcemia by decreasing blood calcium levels
- encourages excess calcium to be deposited in bones
What is Parathyroid Hormone (PTH)?
- produced by parathyroid glands (small, pale nodules in, on, or near thyroid glands)
- helps maintain blood calcium levels by producing the opposite effect of calcitonin
- prevents hypocalcemia by increasing blood calcium if it gets too low
What is Hypocalcemia?
- milk fever (when parathormone is overwhelmed in lactating animals)
- called eclampsia in small animals
- can cause muscle weaknesss and tremors
- treated by supplementing calcium rapidly into system
What is the Adrenal Cortex?
- located near cranial ends of kidney
- produce:
- glucocorticoid hormones (cortisol)
- mineralcorticoid hormones (aldosterone)
- sex hormones (adrogens and estrogens)
What are Glucocorticoid hormones?
- cortisol
- causes blood glucose levels to rise due to protein and lipid catabolism causing gluconeogensis
- increaes body’s resistance to stress, decrease immune response, and decrease inflammation
What are Mineralcorticoid hormones?
- aldosterone
- affects the levels of Na, K and H in body
- increase sodium reabsorption and potassium/hydrogen excretion in the kidneys
What are Sex Hormones?
-androgens and estrogens
What is Cushing’s Disease?
-too much cortisol in system
What are symptoms of Cushing’s Disease?
- PU/PD/PP
- hair loss
- muscle wasting
- pot belly
- slow wound healing
- caused by pituitary tumor
What is Addison’s Disease?
- deficiency of adrenocortical hormones
- Hypoadrenocorticism
–lack of minearlcorticoids and or glucocorticoids
What are symptoms of Addison’s Disease?
- weakness
- lethargy
- vomiting
- diarrhea
- weight loss
- can be caused by sudden withdrawl of corticosteroid drugs
What is the Adrenal Medulla?
- resembles nervous tissue
- controlled by sympathetic portion of nervous system
- produces: epinephrine and norepinehrine
- increases HR, CO and BP, dilates air passageways in lungs, decreases GI function
What is the Pancreas?
- located near duodenum
- both exocrine and endocrine functions
- pancreatic islets (islets of Langerhans): groups of cells scatterd through pancreas
- alpha cells:glucagon
- beta cells: insulin
- delta cells:somatostatin
What are Pancreatic Hormones?
- Insulin
- glucogen
- somatostatin
What is Insulin?
- lowers blood glucose
- causes glucose, amino acids and fatty acids to be absorbed into body cells
What is Glucagon?
- raises blood glucose
- stimulates liver cells to convert stored glycogen to glucose
- stimulating gluconeogensis
What is Somatostatin?
inhibits release of insulin, glucagon and GH and decreases GI activity
What is Diabetes Mellitus?
- pancreatic dysfunction
- caused by deficency of insulin
- results from build up of glucose
What are symptoms of Diabetes Mellitus?
- polyuria
- polydipsia
- polyphagia
- weight loss
- weakness
- not curable but treatable
What are Ovaries?
- produces ovas (eggs) and hormones in cycles
- controlled by FSH and LH (from anterior pituitary)
- Hormones produced in ovaries : Estrogens and Progesterones
What is Estrogen?
- FSH stimulates ovarian follicles to develop
- increasing estrogen levels cause physical and behavioral changes
- when follicle is fully mature, LH levels peak
What is Progestins?
- group of hormones produced by corpus luteum
- prepares uterus to recieve fertilized ovum
- needed to maintain pregnancy
What are the Kidneys?
- produce erythropoietin: stimulates red bone marrow to increase production of RBC’s
- stimulated by hypoxia
- As RBC production increases, more oxygen is delivered to kidneys
- lack of production may result in anemia
What is the Stomach?
- gastrin is produced by G-cells in the wall of the pyloric antrum
- stimulated by the presence of food
- causes HCL secretion, digestive enzyme secretion and encourages contraction of the stomach
What are the Small Inestines?
- chyme entering the small intestines cause Secretin and CCK to be released
- cause stomach motility
- Secretin stimulates the pancreas to secrete biocarbonate
- CCK stimulates the gallbladder
What is Placenta?
- surrounds developing fetus during pregnancy
- acts as interface with maternal circulation
- produces hormones to support and maintain pregnancy
What is the Thymus?
- located in cranial mediastinum
- important during eary development, will shrink
- important in immune system development
–produces:Thymosin and Thymopoietin
What is the Pineal Body?
- influences body’s biological clock
- melatonin:hormone like substance that affects moods and wake/sleep cycles
What are Prostaglandins?
- derived from unsaturated fatty acids
- sometimes called tissue hormones
- travel short distances
- prodced in variety of body tissues: skin, intestines, brain, kidneys, lung, reproductive organs, eye
What are the effects of Prostaglandins?
- influence blood pressure
- GI function
- respiratory function
- kidney function
- blood clotting
- inflammation
- reproductive functions
