Chapter 13: The Endocrine System Flashcards
negative feedback
control mechanism in which rising level of a hormone leads to a decrease in hormone secretion
3 methods of negative feedback
- tropic hormones
- nervous system control
- changes in composition of internal environment
tropic hormones
act on other glands, to regulate their hormone secretion
nervous system control
nervous system directly stimulate some glands to secrete their hormones
changes in composition of internal environment
changes levels of specific substances in the blood stimulates or inhibits secretion of certain hormones
what controls hormone secretion?
various negative feedback mechanisms
pituitary gland
- lies at the base of brain, in sella turcica of sphenoid bone
- attached to hypothalamus by pituitary stalk
pituitary stalk is also called…
infundibulum
2 portions of pituitary gland
- anterior (adenohypophysis)
- posterior (neurohypophysis)
does the posterior portion of the pituitary gland produce hormones?
no
anterior lobe regulation
hypothalamic releasing hormones are transported through the Hypophyseal Portal System, and stimulate cells of anterior lobe to release hormones
posterior lobe regulation
nerve impulses from hypothalamus travel through the infundibulum & stimulate nerve endings in posterior lobe to release hormones
anterior pituitary hormones
released in response to a releasing hormone from the hypothalamus; some inhibited by inhibiting hormones from the hypothalamus
examples of anterior pituitary hormones
- growth hormone (GH)
- prolactin (PL)
- thyroid stimulating (TSH)
- adrenocorticotropic (ACTH)
- follicle stimulating (FSH)
- luteinizing (LH)
gigantism
excess GH while growth plates open
dwarfism
inadequate GH while growth plates open`
thyroid hormone
controls metabolism
how is TSH secretion controlled?
- by the level of thyrotropin releasing hormone (TRH) from the hypothalamus
- negative feedback by thyroid hormones, the final hormones
posterior pituitary hormone
2 hormones are produced by neurons in the hypothalamus, and stored and released by posterior pituitary gland
how are the hormones produced in hypothalamus transported to posterior pituitary gland?
pituitary stalk; infundibulum
two types of posterior pituitary hormones
- antidiuretic hormone (ADH)
- oxytocin (OT)
antidiuretic hormone
decreases urine production by removing volume of H2O the kidneys excrete; also causes vasoconstriction to increase blood pressure
oxytocin
also called the love hormone; causes muscle contraction in uterine wall during childbirth, milk ejection during lactation, and boosts testosterone in men
thyroid gland
- has two lateral lobes, connected by isthmus
- lies below larynx, anterior & lateral to trachea
- has special ability to remove iodine from blood
- produces 3 hormones
three hormones produced by thyroid gland
- T4
- T3
- calcitonin
T4
thyroxine
T3
triiodothyronine
petocin
used to induce women into labor
what cells produce T3 & T4
follicular cells
what cells produce calcitonin?
extra or parafollicular cells
what is the thyroid gland made of?
follicles
follicles
round secretory units
what surrounds each follicle?
a single layer of follicular cells
what fills follicle cavities?
vicious colloid
what lies outside follicles?
extra follicular (c) cells
calcitonin
lowers blood calcium
hyperthyroid
increased metabolism; hyperthyroidism, graves disease
hypothyroid
decreased metabolism; hypothyroidism, Hashimoto’s, simple goiter
