Final Exam - Endocrine System (parts 1, 2, and 3) Flashcards
What are the characteristics of human hormones?
- generally secreted by endocrine glands directly into circulatory system
- trigger a change in another organ’s activities
- affect only certain target cells that have the specific receptor of the hormone
What are the two main classes of hormones?
- amino acid-based hormones
- steroids
How do hormones act?
based on chemical nature and receptor location
What are the characteristics of water-soluble hormones?
- act on plasma membrane receptors
- act via G protein second messengers
- cannot enter cell
What are the characteristics of lipid-soluble hormones?
- act on intracellular receptors that directly activate genes
- can enter cell
What are the characteristics of hormone levels in the blood?
- controlled by negative feedback systems
- levels vary only within narrow, desirable ranges
What are the three types of endocrine gland stimuli?
- humoral stimuli: blood
- neural stimuli: nerve fibers
- hormonal stimuli: other hormones
How does humoral stimuli work?
changing blood levels of ions and nutrients directly stimulate secretion of hormones
How does neural stimuli work?
nerve fibers stimulate hormone release
How does hormonal stimuli work?
hormones stimulate other endocrine organs to release their hormones
What are the characteristics of nervous system modulation?
- nervous system can make adjustments to hormone levels when needed by stimulating or inhibiting endocrine glands
- can override normal endocrine controls in extreme circumstances
What three factors impact target cell activation?
- blood levels of hormone
- relative number of receptors on/in target cell
- affinity of binding between receptor and hormone
What is up-regulation, in terms of target cell receptors?
target cells form more receptors in response to low hormone levels
What is down-regulation, in terms of target cell receptors?
targets cells lose receptors in response to high hormone levels, which desensitizes the target cells
When does the nervous system tend to act vs when does the endocrine system tend to act?
- nervous system acts when an immediate or short-term response is needed
- endocrine system acts when the response can last over a longer time period
What are the characteristics of the hypothalamus?
- portion of the brain that contains a number of small nuclei with a variety of functions
- links the nervous system to the endocrine system via the pituitary gland
- connected to pituitary gland via infundibulum
What are the two lobes of the pituitary gland?
- posterior pituitary
- anterior pituitary
What is the posterior pituitary?
composed of neural tissue that secretes neurohormones
What is the anterior pituitary?
consists of glandular tissue
What are the characteristics of the pituitary-hypothalamic relationship for the posterior pituitary?
- posterior lobe is neural tissue derived from a downgrowth of the brain
- maintains neural connection to hypothalamus via hypothalamic-hypophyseal tract
- hypothalamus secretes oxytocin and ADH, which are stored in axon terminals in posterior pituitary
What are the characteristics of the pituitary-hypothalamic relationship for the anterior pituitary?
- anterior lobe is glandular
- vascular connection to the hypothalamus via hypophyseal portal system
- hypothalamus secretes releasing and inhibiting hormones to anterior pituitary to regulate hormone secretion
What are the characteristics of oxytocin?
- strong stimulant of uterine contractions
- acts as hormonal trigger for milk ejection
- neurotransmitter in brain
- positive feedback
What are the characteristics of ADH?
- hypothalamus contains osmoreceptors that monitor solute conc.
- if solute conc. is too high, posterior pituitary secretes ADH
- targets nephrons to reabsorb more water
- inhibited by alcohol and diuretics
What are the anterior pituitary hormones?
- growth hormone
- thyroid-stimulating hormone (tropic)
- adrenocorticotropic hormone (tropic)
- follicle-stimulating hormone (tropic)
- luteinizing hormone tropic)
- prolactin
What are the characteristics of growth hormone?
- has a direct action on metabolism
- indirect action on growth
- stimulates most cells to enlarge and divide, especially bone and muscle cells
What are the characteristics of thyroid-stimulating hormone?
- stimulates normal development and secretory activity of thyroid gland
- release is triggered by TRH from hypothalamus
- inhibited by rising blood levels of thyroid hormones
What are the characteristics of ACTH?
- stimulates adrenal cortex to release corticosteroids
- trigged by hypothalamic CRH
What are the characteristics of gonadotropins (FSH and LH)?
- secreted by gonadotropic cells of anterior pituitary
- FSH stimulates gamete production
- LH promotes gonadal hormone production
- triggered by gonadotropin-releasing hormone
What are the characteristics of prolactin?
- secreted by prolactin cells of anterior pituitary
- stimulates milk production in females
- regulated by prolactin-inhibiting hormone
What are the characteristics of thyroid hormone (TH)?
- body’s major metabolic hormone
- inactive form is T4 (thyroxine
- active form is T3 (triiodothyronine)
- iodine-containing amine hormones
What are the effects of thyroid hormone?
- increased basal metabolic rate and heat production
- regulation of tissue growth and development
- maintained blood pressure
What are the characteristics of thyroid hormone regulation?
- release is regulated by negative feedback
- falling TH levels stimulate release of TSH, rising TH levels prevent TSH production
- negative feedback can be overcome during pregnancy or cold exposure
What are the characteristics of the adrenal gland?
- paired, pyramid-shaped organs atop kidneys
- structurally and functionally two glands in one
- consist of adrenal cortex and adrenal medulla
What is the role of mineralocorticoids?
regulate electrolyte concentrations
What are the characteristics of aldosterone?
- most potent mineralocorticoid
- stimulates Na+ reabsorption and K+ elimination in kidneys
What are the characteristics of glucocorticoids?
- influence metabolism of most cells
- help us resist stressors
- keep blood glucose levels constant
- maintain blood pressure
What are the main glucocorticoid hormones?
- cortisol
- cortisone
- corticosterone
What are gonadocorticoids?
weak androgens converted to testosterone and estrogens in the gonads
What is the role of the adrenal medulla?
synthesize catecholamines, primary epinephrine and norepinephrine
What are the effects of catecholamines?
- vasoconstriction
- increased heart rate
- increased blood glucose levels
- blood diverted to brain, heart, and skeletal muscle
What are the stages of General Adaptation Syndrome?
- stage one: alarm reaction
- stage two: stage of resistance
- stage three: stage of exhaustion
What is the role of the pancreas?
to secrete insulin and glucagon to regulate blood glucose levels
