Chapter 11- Endocrine system Flashcards
List the major endocrine glands
hypothalamus.
pituitary.
thyroid.
parathyroids.
adrenals.
pineal body.
the ovaries.
the testes.
Peptide hormones
Consist of chains of a few to 200 or more amino acids arranged like pearls in a necklace
- they are hydrophilic
Steroid hormones
Are lipids that are synthesized from cholesterol. They are hydrophobic
Monoamine hormones
Catecholamines (epinephrine and noreprinephrine)
Describe the structure and function of the pituitary gland
Called the master endocrine gland/Hypophysis
Two separate glands with different embryological origins, different structures, different functions
Anterior pituitary = adenohypophysis
* Produces hormones when stimulated
* Produces Stimulating hormones
–(“Trophic hormones” or Tropins”)
—–Prolactin
—- Thyroid stimulating hormones
—— Luteinizing
—- ACTH
—— Growth hormones
Posterior pituitary = neurohypophysis
* Stores and releases hormones
Growth hormone
Also known as somatotropin and somatotropic hormone
Promotes body growth in young animals
Helps regulate metabolism of proteins, carbohydrates, and lipids in animal’s cells
*Anabolism – proteins
* Catabolism – fats, carbohydrates
Anterior pituitary
Adrenocorticotropic hormone
Regulates response to STRESS!!!
Stimulates adrenal cortex
Regulated by feedback from hormones of adrenal
cortex
ACTH can also be released quickly as a result of
stimulation of hypothalamus by other parts of brain
Anterior pituitary
follicle stimulating hormone
Named for effect on females
Effects in the female
*Stimulates oogenesis
*Stimulates production and secretion of estrogen
Effects in the male
*Stimulates spermatogenesis
Anterior pituitary gland
luteinizing hormone
Luteinizing Hormone (LH)
Completes process of follicle development in ovary
LH levels reach peak when follicle is fully mature
* Usually causes ovulation
* Causes development of corpus luteum
LH in males stimulates interstitial cells to produce
testosterone
Anterior pituitary
melanocyte stimulating hormone
Associated with control of color changes in pigment cells of reptiles, fish, and amphibians
* Rapid changes of colors and color patterns
Administration of artificially large amounts to higher mammals
* Can cause darkening of skin by melanocyte stimulation
oxytocin
Effect on uterus
* Induces uterine contractions at
breeding and parturition
Effect on active mammary
glands
* Stimulation of teat by nursing or
milking causes oxytocin to be
released
* Causes movement of milk down
to lower parts of the mammary
gland (milk letdown)
Hypothalamus
Thyroid gland
2 lobes on either side of larynx
Lobes may be connected by isthmus
2 hormones produced in follicles:
-Thyroid hormone
-Calcitonin
Thyroid Stimulating hormone
Thyroid-Stimulating Hormone (TSH)
Also known as thyrotropic hormone
Stimulates growth and development of thyroid
gland
Causes thyroid gland to produce its hormones
Secretion regulated by:
* Feedback from thyroid
*Interaction among hypothalamus, anterior
pituitary, and thyroid glands
calcitonin
Produced by C cells located between thyroid
follicles
Helps maintain blood calcium levels
Prevents hypercalcemia by encouraging excess
calcium to be deposited in bones
Parathyroid hormone is the other hormone involved
in maintaining blood calcium levels
parathormone
A substance made by the parathyroid gland that helps the body store and use calcium
list three categories of hormones produced by the adrenal cortex
glucocorticoid
mineralocorticoid
sex hormones
list the hormones produced by the pancreatic islet cells
insulin, glucagon and somatostatin
Insulin
Essential for life
causes glucose, amino acids and fatty acids in the blood stream to be absorbed through cell membranes
produced by the pancreas
glucagon
Opposite effect of insulin
stimulates liver cells to convert glycogen to glucose
stimulates gluconeogenesis
somatostatin
Somatostatin from the hypothalamus inhibits the pituitary gland’s secretion of growth hormone and thyroid stimulating hormone.
Androgens
Male sex hormones
promote the development of male characteristics.
estrogens
Follicle cells produce and release estrogens
* FSH stimulates ovarian follicles to develop
* Follicle grows
*Amount of estrogen produced increases
*Anterior pituitary reduces FSH and increases LH
production
* LH peaks when follicle is fully mature
*Increasing estrogen levels accelerate physical and
behavioral change
* Ovulation occurs
progestins
Group of hormones produced by corpus luteum (ovary)
*Principal progestin = progesterone
In pregnant female
* Corpus luteum produces progesterone, necessary for pregnancy to be maintained
If no pregnancy occurs
* Lack of hormone causes corpus luteum to shrink and disappear
less important-
Progestin-related drugs used therapeutically
hormone produced by the kidneys
Produce erythropoietin
*Stimulated by hypoxia
*Effect is to increase production of red blood cells
*Increased oxygen level slows down production
Deficiency of erythropoietin
*Anemia often accompanies kidney disease or failure
Erythropoietin
Hormone produced by kidney that stimulates red bone marrow to increase production of red blood cells
Gastrin
Produced by the stomach
stimulates production of gastric juices
Secretin
Hormone produced by the small intestine
Stimulates bicarbonate secretion
cholecystokinin
Produced in small intestine
stimulates pancreas to release digestive enzymes into the duodenum
Placental hormones
*Estrogen
*Progesterone
* Chorionic gonadotropin (some species)
* Relaxin (some species)
Differences nervous system and endocrine gland
Nervous system
* Uses chemicals to carry messages
* Neurotransmitters produced by neurons
* Travel short distances across synapses
*Allows system to react quickly
Endocrine system
* Uses chemicals to carry messages
* Hormones secreted directly into bloodstream
* Travel long distances to reach targets
*Body reacts more slowly to changes
Hormones
Hormones are chemical messengers
* Produced by endocrine gland or modified neurons
*Travel via bloodstream
*impact target organs
Produce effects only when they bind to their specific receptors in or on cells
Cell that has receptors for a particular hormone is a target of that hormone
controlled by negative feedback system
Endocrine physiology
Homeostasis!
Level of hormone in blood directly or indirectly
“feeds back” to the gland that produced it
Activity of gland is affected
* Negative feedback system
*Activity decreased by rising levels of hormone
*Positive feedback system
*Activity increased by falling levels of hormone
Negative Feedback system
When the level of a specific hormone drops below
needed levels, the appropriate endocrine gland is
stimulated to produce more hormone.
Once the proper hormone level is present in the
bloodstream, stimulation of that endocrine gland is
reduced and production of that hormone is
reduced.
Homeostasis examples
Body temperature
Heart rate
Blood pH
Levels of hormones
Blood pressure
Is pancreas endocrine or exocrine
Both!!!!!
Hypothalamus
Part of the diencephalon of
the brain – nervous tissue
Links conscious mind with rest of body
Links cerebrum with endocrine system by regulating pituitary gland
Controls activities of the pituitary gland
Portal system of blood vessels links to anterior portion of pituitary gland
Modified neurons also secrete antidiuretic hormone (ADH) and oxytocin
Transported to posterior pituitary for storage
Released into bloodstream by nerve impulses from hypothalamus
antidiuretic hormone
ADH
Helps prevent diuresis
Released when hypothalamus receptors detect dehydration
* More-concentrated urine is produced
*ADH travels to the kidney – causes kidneys to reabsorb more water (WHERE?) from the urine and return it to the bloodstream
ADH deficiency causes diabetes insipidus
*Polydipsia and polyuria
hypothalamus
Anterior Pituitary Hormones
Growth hormone
Prolactin
Thyroid-stimulating hormone (TSH)
Adrenocorticotropic hormone (ACTH)
Follicle-stimulating hormone (FSH)
Luteinizing hormone (LH)
Melanocyte-stimulating hormone
Prolactin
Helps trigger and maintain lactation
Production and release continues as long as teat
continues to be stimulated by nursing or milking
Without stimulation from prolactin:
* Milk production stops
* Mammary gland shrinks back to non-lactating size
No known effect in male mammals
Anterior pituitary
Thyroid hormones
T4 = tetra-iodothyronine = thyroxine
*A prohormone, a circulating reservoir
T3 = tri-iodothyronine
* The active hormone
Hormones are produced when TSH from anterior pituitary stimulates the thyroid gland
Effect every cell in the body
Effects of thyroid hormones
Regulates metabolic rate of all body’s cells
* Calorigenic effect
*Allows animals to maintain constant internal body
temperature
Affects metabolism of proteins, carbohydrates,
and lipids
*Anabolism or synthesis of proteins, depending on
animal’s diet
* Maintains homeostasis of blood glucose level
*Encourages catabolism of lipids
Parathyroid
4 small glands posterior to thyroid gland
Parathyroid hormone (parathormone)
* Opposite effect ofcalcitonin
*Prevents hypocalcemia
Parathyroid hormone
Also called parathormone
Produced by the parathyroid glands
*Small, pale nodules in, on, or near the thyroid
glands
Helps maintain blood calcium levels
Prevents hypocalcemia
* Causes kidneys to retain calcium and intestine to
absorb calcium from food; withdraws calcium from
bones
*Exerts the opposite effect of calcitonin
Adrenal glands
Located near cranial ends of kidneys
Consist of two glands:
*Adrenal cortex
*Adrenal medulla
Adrenal cortex
The Adrenal Cortex
Produces numerous hormones:
Glucocorticoids (cortisone, cortisol, corticosterone)
* Cause general hyperglycemic effect
* Help maintain blood pressure
* Help body resist effects of stress
Mineralocorticoids (e.g. aldosterone)
* Regulate levels of electrolytes
Sex hormones (androgens, estrogens
Glucocorticoids
Cortisone, cortisol
Gluconeogenesis
* Hyperglycemic effect
Helps maintain blood
pressure
Helps animal’s body resist
effects of stress
Produced in the adrenal cortex
Mineralocorticoids
Aldosterone
* Works with ADH
Electrolyte homeostasis
* Regulate levels of important electrolytes (mineral
salts) in animal’s body
Targets kidneys to Na+
retention, reduce urine
volume
Adrenal gland
Adrenal Medulla
Resembles nervous tissue
2 hormones produced
*Epinephrine and norepinephrine
*Secretion controlled by sympathetic portion of autonomic nervous system
functions
* “Fight or flight” response
Increases heart rate and output, increases blood
pressure, dilates air passageways in lungs, and
decreases GI function
Pancreas
Long, flat organ located in theabdomen near the duodenum. Has both exocrine and endocrine functions
Only gland in body with exocrine and endocrine function
Exocrine – digestive enzymes
Endocrine – small % of pancreas
* Hormones regulating glucose
*Islets of Langherhans
*Pancreatic islets, or islets of Langerhans
*Alpha cells – produce glucagon
*Beta cells – produce insulin
* Delta cells – produce somatostatin
Pancreatic hormones
Insulin
Lowers blood glucose levels
* Causes glucose, amino acids, and fatty acids in blood to be absorbed into body cells
Glucagon
Raises blood glucose levels
*Stimulates liver cells to convert glycogen toglucose
*Stimulates glycogenesis (gluconeogenesis)
Testes
2 testes housed in
scrotum
Seminiferous tubules
*Spermatogenesis
Interstitial cells
* Clumps of endocrine cells
* Produce androgens when stimulated by LH
Testosterone
* Primary androgen
* Provides for development of male secondary sex characteristics and accessory sex glands
* Activates spermatogenesis
Testosterone
Androgens
*Anabolic effect
Made in the testes
Ovaries
Produce ova and hormones in cycles
Cycles controlled by FSH and LH
Hormone groups produced:
*Estrogens
–From ovarian follicles
*Estradiol and estrone
*Progestins
– From corpus luteum
–Equine – used to synchronize estrous
periods in mares
* Relaxin
Relaxin
Effects of hormone
* Relaxation of ligaments surrounding birth canal
* Mammary development
Cholesterol is the building block for what hormones
Progesterone, estrogen, cortisol, testosterone, aldosterone
Stomach’s hormone production
Gastrin: produced by cells in the wall of the stomach
Secretion stimulated by presence of food in the stomach
Stimulates gastric glands to secrete hydrochloric acid and digestive enzymes
Encourages muscular contractions of the stomach wall
Small intestine hormone production
Secretin and cholecystokinin produced by cells in lining of small intestine in response to presence of chyme in duodenum
Secretion occurs in response to presence of chyme in duodenum
Secretin stimulates pancreas to secrete fluid to neutralize acidic chyme after it passes out of the stomach
Cholecystokinin stimulates pancreas to release digestive enzymes into the duodenum
Thymus hormone production
Extends cranially from the level of the heart up into neck region along both sides of the trachea
Large in young animals, atrophies later in life
Function involves hormones or hormone-like chemical substances (e.g., thymosin and thymopoietin)
Seems to cause certain cells to be transformed into T-lymphocytes
Pineal Body hormone
A part of the brain
Influences the body’s biological clock
Produces the hormone melatonin
*Affects moods and wake-sleep cycles
*“Jet Lag”?
* May also have role in timing of seasonal estrus
cycles
Prostaglandins
Hormone-like substances (“tissue hormones”) derived from unsaturated fatty acids
Produced in a variety of body tissues (skin, intestine, brain, kidney, lungs, reproductive organs, and eyes)
Influence blood pressure, blood clotting, inflammation, GI, respiratory, reproductive, and kidney function
Non-steroidal anti-inflammatory drugs (NSAIDS)
* Inhibit synthesis of certain prostaglandins
* Side effects (Rimadyl, Deramaxx, Metacam)
