chapter 18 Flashcards
the pineal gland
. Melatonin functions to support the
body’s “biologic clock” and is thought to induce sleep. The pineal gland has been linked
to a mental condition, seasonal affective disorder (SAD)
diologic landmark when x-rays of the brain are examined.
Hormones are also secreted by endocrine tissue in other organs apart from the major
endocrine glands.
erythropoietin (kidney), human chorionic gonadotropin
(placenta), and cholecystokinin (gallbladder
Prostaglandins
are hormone-like substances
that affect the body in many ways. First found in semen (produced by the prostate gland)
but now recognized in cells throughout the body, prostaglandins have three functions:
(1) stimulate the contraction of the uterus; (2) regulate body temperature, platelet
aggregation, and acid secretion in the stomach; and (3) have the ability to lower blood
pressure
isthmus
a narrow strip of glandular
tissue that connects the two lobes on the ventral (anterior) surface of the trachea
Two of the hormones secreted by the thyroid gland
thyroxine or tetraiodothyronine
(T4) and triiodothyronine (T3). These hormones are synthesized in the thyroid gland from
iodine, which is picked up from the blood circulating through the gland, and an amino
acid called tyrosine. T4 (containing four atoms of iodine) is much more concentrated in
the blood, whereas T3 (containing three atoms of iodine) is far more potent in affecting
the metabolism of cells. Most thyroid hormone is bound to protein molecules as it travels
in the bloodstream.
calcitonin
A more recently discovered hormone produced by the thyroid gland is calcitonin.
Calcitonin is secreted when calcium levels in the blood are high. It stimulates calcium to
leave the blood and enter the bones, thereby lowering blood calcium back to normal
Parathyroid hormone (PTH
) is secreted by the parathyroid glands. This hormone (also
known as parathormone) mobilizes calcium (a mineral substance) from bones into the
bloodstream, where calcium is necessary for proper functioning of body tissues, especially
muscles
The adrenal cortex secretes steroids or corticosteroids (complex chemicals derived from cholesterol);
; the adrenal medulla secretes catecholamines
chemicals derived from amino acids
The adrenal cortex secretes three types of corticosteroid
Glucocorticoids - Cortisol Increases blood glucose Mineralocorticoid - Aldosterone Increases sodium reabsorption; regulates blood pressure Sex hormones - Androgen Estrogen Sexual characteristics
The adrenal medulla secretes two types of catecholamine hormones:
- Epinephrine (adrenaline)—Increases heart rate and blood pressure, dilates bronchial
tubes, and releases glucose (sugars) from glycogen (storage substance) when the body
needs it for more energy. - Norepinephrine (noradrenaline)—Constricts blood vessels to raise blood pressure.
nd partly behind the stomach [2] at the level of
the first and second lumbar vertebrae. The endocrine tissue of the pancreas consists of
specialized hormone-producing cells called the islets of Langerhans [3] or islet cells
The islets of Langerhans produce insulin (produced by beta cells) and glucagon (produced
by alpha cells). Both play a role regulating blood glucose (sugar) levels.
insulin
Lowers blood sugar (glucose to glycogen)
Glucagon
Raises blood sugar
glycogen to glucose
The pituitary gland, also called the hypophysis
The pituitary consists of two distinct parts: an anterior lobe or adenohypophysis [1],
composed of glandular epithelial tissue, and a posterior lobe or neurohypophysis [2],
composed of nervous tissue. The hypothalamus [3] is a region of the brain under the
thalamus and above the pituitary gland
Special secretory neurons in the hypothalamus send
releasing and inhibiting factors (hormones) via capillaries to the anterior pituitary gland.
The hypothalamus also produces and secretes hormones directly to the
posterior lobe of the pituitary gland, where the hormones are stored and then released
anterior pituitary gland 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 (also called IGF), which stimulates the growth
of bones. It increases blood glucose levels and is secreted during exercise, sleep, and
hypoglycemia. - Thyroid-stimulating hormone (TSH), or thyrotropin—Stimulates the growth of the
thyroid gland and secretion of thyroxine (T4) and triiodothyronine (T3). - Adrenocorticotropic hormone (ACTH), or adrenocorticotropin—Stimulates the
growth of the adrenal cortex and increases its secretion of steroid hormones (primarily
cortisol). - 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 (an interstitial cell–
stimulating hormone) stimulates the testes to produce testosterone. - Prolactin (PRL)—Stimulates breast development during pregnancy and sustains
milk production after birth.
