Flashcards in 3 Veterinary Term: Endocrine System (not done) Deck (95):
What is the endocrine system?
is an information signaling system similar to the nervous system.
However, the nervous system uses nerves to conduct information, whereas the endocrine system uses blood vessels as information channels.
What are hormones?
(from the Greek word hormon, meaning urging on), which regulate the many and varied functions of an organism.
specific chemical messengers released into the bloodstream by Glands located in many regions of the body
Give some Examples of functions of hormones
one hormone stimulates the growth of bones
another causes the maturation of sex organs and reproductive cells
and another controls the metabolic rate (metabolism) within all the individual cells of the body.
A powerful endocrine gland below the brain secretes what?
a wide variety of different hormones that travel through the bloodstream and regulate the activities of other endocrine glands.
Hormones produce their effects by doing what?
binding to receptors, which are recognition sites in the various target tissues on which the hormones act.
The receptors initiate specific biologic effects when the hormones bind to them.
Each hormone has its own receptor, and binding of a receptor by a hormone is much like the interaction of a key and a lock.
Endocrine glands, no matter which hormones they produce, secrete their hormones where?
directly into the bloodstream
Exocrine glands send chemical substances (tears, sweat, milk, saliva) via?
ducts to the outside of the body.
Examples of exocrine glands are sweat, mammary, mucous, salivary and lacrimal glands.
The ductless, internally secreting endocrine glands are:
1. Thyroid gland
2. Parathyroid glands
3. Adrenal glands
5. Pituitary gland
6. Ovaries in female
7. Testes in male
8. Pineal gland
9. Thymus gland
Hormones can also be secreted by what?
endocrine tissue apart from the major glands.
Examples are erythropoietin (kidney) and cholecystokinin (gallbladder).
What are Prostaglandins and what do they do?
are hormone‐like substances that affect the body in many ways.
They stimulate the contraction of the uterus, regulate body temperature, platelet aggregation and acid secretion in the stomach and have the ability to lower blood pressure.
What is The thyroid gland composed of?
a right and a left lobe on either side of the trachea.
What are Two of the hormones secreted by the thyroid gland?
thyroxine or tetraiodothyronine (T4) and triiodothyronine (T3)
thyroxine or tetraiodothyronine (T4) and triiodothyronine (T3) are synthesized in the thyroid gland from what?
from iodine, which is picked up from blood circulating through the gland, and from an amino acid called tyrosine.
T4 is much more concentrated in the blood, whereas T3 is far more potent in affecting the metabolism of cells.
Most thyroid hormone is bound to what as it travels in the bloodstream?
T4 and T3 are necessary in the body because?
maintain a normal level of metabolism in all body cells.
Cells need oxygen to carry on metabolic processes, one aspect of which is burning food to release the energy stored within it.
Thyroid hormone aids cells in what?
their uptake of oxygen and thus supports the metabolic rate in the body.
Injections of thyroid hormone does what?
raises the metabolic rate
removal of the thyroid gland does what?
diminishes thyroid hormone content in the body, resulting in a lower metabolic rate, heat loss and poor physical and mental development.
A more recently discovered hormone produced by the thyroid gland is?
When is Calcitonin secreted?
secreted when calcium levels in the blood are high.
What does Calcitonin stimulate?
stimulates calcium to leave the blood and enter the bones, thus lowering blood calcium back to normal.
The parathyroid glands are located where?
on the dorsal aspect of the thyroid gland.
What do the parathyroid glands secrete?
Parathyroid hormone (PTH)
What is the function of Parathyroid hormone (PTH)?
mobilizes calcium from bones into the bloodstream, where calcium is necessary for proper functioning of body tissues, especially muscles.
calcium in the food we eat is absorbed from where?
the intestine and carried by the blood to the bones, where it is stored.
example of the way hormones in general control the homeostasis (equilibrium or constancy in the internal environment) of the body
The adjustment of the level of calcium in the blood
If blood calcium decreases (as in Vitamin D deficiency or pregnancy) what happens?
parathyroid hormone secretion increases, causing calcium to leave bones and enter the blood stream.
Thus blood calcium levels are brought back to normal.
What are the adrenal glands?
are two small glands, one on top of each kidney.
The adrenal glands consist of what two parts?
an outer portion, the adrenal cortex, and an inner portion, the adrenal medulla.
The adrenal cortex and adrenal medulla are two glands in one, secreting different hormones.
What does The adrenal cortex secrete?
steroids or corticosteroids
What does the adrenal medulla secrete?
The adrenal cortex secretes what three types of corticosteroids?
Sex hormones: Androgens (testosterone) and estrogen
What are Glucocorticoids?
These steroid hormones have an important influence on the metabolism of sugars, fats, and proteins within all body cells and have a powerful anti‐inflammatory effect.
Cortisol helps regulate glucose, fat and protein metabolism. It raises blood glucose as part of a response to stress.
What are Mineralocorticoids?
The major mineralocorticoid is aldosterone.
It regulates the concentration of mineral salts (electrolytes) in the body.
Aldosterone acts on the kidney to reabsorb sodium (an important electrolyte) and water and to excrete potassium.
Thus it regulates blood volume and pressure and electrolyte concentration.
What are Sex hormones?
Androgens (testosterone) and estrogens are secreted in small amounts and influence sex characteristics.
The adrenal medulla secretes what two types of catecholamine hormones?
What is Epinephrine (adrenaline)?
Increases heart rate and blood pressure, dilates bronchial tubes, and releases glucose from glycogen when the body needs it for more energy.
What is Norepinephrine (noradrenaline)?
Constricts blood vessels to raise blood pressure.
Both epinephrine and norepinephrine are what and why?
sympathomimetic agents because they mimic the actions of the sympathetic nervous system. They are released to help the body meet the challenges of stress in response to stimulation by the sympathetic nervous system.
Where is The pancreas located?
near and partly behind the stomach
The endocrine tissue of the pancreas consists of what?
specialized hormone‐producing cells called the islets of Langerhans.
More than 98% of the pancreas consists of what?
exocrine cells (glands and ducts).
These cells secrete digestive enzymes into the GI tract.
What do The islets of Langerhans produce?
insulin and glucagon
Both play a role in regulating blood glucose levels.
When blood glucose rises, insulin does what?
lowers blood glucose by promoting its entrance into body cells and use as fuel for energy. Also, insulin lowers blood sugar by causing conversion of glucose to glycogen in the liver.
When blood glucose levels fall, glucagon does what?
acts on liver cells to promote conversion of glycogen back to glucose, so that blood sugar rises.
What is the pituitary gland?
also called the hypophysis, is a small, pea‐sized gland located at the base of the brain in a small, pocket‐like depression of the skull called the sella turcica.
It is a well‐protected gland, with the entire mass of the brain above it and the nasal cavity below.
The ancient Greeks incorrectly imagined that its function was to produce pituita or nasal secretion.
The pituitary consists of two distinct parts...what are they?
an anterior lobe or adenohypophysis and a posterior lobe or neurohypophysis.
What is the hypothalamus?
is a region of the brain under the thalamus and above the pituitary gland.
Signals transmitted from the hypothalamus control what?
control secretions by the pituitary gland.
Special secretory neurons in the hypothalamus send what?
send releasing and inhibiting factors (hormones) via capillaries to the anterior pituituary gland.
These factors stimulate or inhibit secretion of hormones from the anterior pituitary.
The hypothalamus also produces and secretes hormones directly to the what?
posterior pituitary gland, where the hormones are stored and then released.
What are The major hormones of the anterior pituitary gland?
Growth hormone (GH) or somatotropin (STH)
Thyroid‐stimulating hormone (TSH)
Adrenocorticotropic hormone (ACTH)
Gonadotropic hormones: follicle‐stimulating hormone (FSH) and luteinizing hormone (LH)
What are Growth hormone (GH) or somatotropin (STH)?
Promotes protein synthesis that results in the growth of bones, muscles and other tissues.
GH also stimulates the liver to make insulin‐like growth factor, which stimulates the growth of bones.
It increases blood glucose levels and is secreted during exercise, sleep and hypoglycemia.
What is Thyroid‐stimulating hormone (TSH)?
Stimulates the growth of the thyroid gland and secretion of thyroxine and triiodothyronine.
What is Adrenocorticotropic hormone (ACTH)?
Stimulates the growth of the adrenal cortex and increases its secretion of steroid hormones.
What are Gonadotropic hormones?
Several gonadotropic hormones influence the growth and hormone secretion of the ovaries in females and the testes in males. In the female, follicle‐stimulating hormone (FSH) and luteinizing hormone (LH) stimulate the growth of eggs in the ovaries, the production of hormones, and ovulation.
In the male, FSH influences the production of sperm, and LH stimulates the testes to produce testosterone.
What is Prolactin?
Stimulates breast development during pregnancy and sustains milk production after birth.
The posterior pituitary gland stores and releases two important hormones that are synthesized in the hypothalamus...what are they?
Antidiuretic hormone (ADH)
What is Antidiuretic hormone (ADH)?
also called vasopressin: Stimulates the reabsorption of water by the kidney tubules. In addition, ADH also increases blood pressure by constricting arterioles.
What is Oxytocin?
Stimulates the uterus to contract during childbirth and maintains labor during parturition.
Oxytocin is also secreted during suckling and causes the production of milk from the mammary glands.
What are the ovaries?
are two small glands located in the lower abdominal region of the female.
What do The ovaries produce?
the female gamete, the ovum, as well as hormones that are responsible for female sex characteristics and regulation of the menstrual cycle.
What are The ovarian hormones?
estrogens and progesterone
What do Estrogens stimulate?
development of ova and development of female secondary sex characteristics.
What is Progesterone responsible for?
the preparation and maintenance of the uterus in pregnancy.
What are the testes?
are two small, ovoid glands suspended from the inguinal region of the male by the spermatic cord and surrounded by the scrotal sac.
What do The testes produce?
the male gametes, spermatozoa, as well as the male hormone called testosterone.
What does Testosterone stimulate?
is an androgen that stimulates development of sperm and secondary sex characteristics in the male
Ex: Gonadotropin (Here, ‐tropin means to act on. Gonadotropins act on gonads)
Pituitary gland, hypophysis
Cortex, outer regions
Ex: Glucagon (in this term‐agon means to assemble or gather together)
Ex: Homeostasis (the suffix –stasis means to control)
Assemble, gather together
Stimulating the function of
Deficient; below; under; less than normal