Chapter 17 - Endocrine System Flashcards
the endocrine system influences metabolic activities via _______ transported in blood
hormones
the study of hormones and endocrine organs
endocrinology
which system responds slower but lasts longer: endocrine or nervous
endocrine
the endocrine system controls and integrates what 5 things
- reproduction
- growth and development
- maintenance of electrolyte, water and nutrient balance of blood
- regulation of cellular metabolism and energy balance
- mobilization of body defenses
- non-hormonal substances (sweat, saliva)
- have ducts to carry secretion to membrane surface
- release outside the blood
exocrine glands
- produce hormones
- lack ducts (ductless)
- release insdie the blood
endocrine glands
what are the endocrine glands
pituitary, thyroid, parathyroid, adrenal and pineal glands
what is the neuroendocrine organ
hypothalamus
what glands have exocrine and endocrine functions
pancreas, gonads, placenta
what tissues and other organs produce hormones
adipose cells, thymus cells in walls of small intestine stomach kidneys heart
2 main classes of hormones
amino acid based hormones
steroids
what do amino acid based hormones consist of
-amino acid derivatives, peptides and proteins
these are synthesized from cholesterol
gonadal and adrenocortical hormones
steroids
long distance chemical signals; travel in blood or lymph
hormones
chemicals that exert effects on same cells that secrete them
*not formal endocrine system
autocrines
locally acting chemicals that affect cells other than those that secrete them
*not formal endocrine system
paracrines
what are not considered hormones (2)
autocrines and paracrines
what are local chemical messengers
autocrine and paracrine
tissues with receptors for specific hormones
target cells
though hormones circulate systemically, only cells with ______ for that hormone are affected
receptors
mechanisms on hormone action on target cells may be able to: (5)
- alter plasma membrane permeability or membrane potential by opening or closing ion channels
- stimulate synthesis of enzymes or other proteins
- activate or deactivate enzymes
- induce secretory activity
- stimulate mitosis
hormones act at receptors in 1 of 2 ways, depending on chemical nature and receptor location
- water soluble hormones (all amino acid based hormones except thyroid hormone)***
- lipid soluble hormones (steroid & thyroid hormones)
***know for test
what hormones cannot enter the cell
water soluble hormones (all amino acid based hormones except thyroid hormone)
what hormones can enter the cell
lipid soluble hormones (steroid and thyroid hormones)
- act on plasma membrane receptors
- act via G protein second messengers
water soluble hormones
-act on intracellular receptors that directly activate genes
lipid soluble hormones
cAMP signaling mechanism steps - 5
- hormone (first messenger) binds to receptor
- receptor activates G protein
- G protein activates adenylate cyclase
- adenylate cyclase converts ATP to cAMP (second messenger)
- cAMP activates protein kinases that phosphorylate proteins
- activated kinases phosphorylate various proteins, activating some and inactivating others
- is rapidly degraded by enzyme
- intracellular enzymatic cascades have huge amplification effect
cAMP signaling mechanism
what does PIP2 stand for
phosphatidyl inositol biphosphate
-involves G protein and membrane bound effector phospholipase c
PIP2 - calcium signaling mechanism
what splits PIP2 into two second messengers
phospholipase c
what are the two second messengers formed from PIP2 when it splits
diacylglycerol (DAG) and inositol trisphosphate (IP3)
DAG activates protein ______; IP3 causes ____ release
kinase ; CA2+
what ions act as second messenger for PIP2
calcium
cGMP acts as second messengers for some hormones. what does cGMP stand for
cyclic guanosine monophosphate
intracellular receptors and direct gene activation for steroid hormones and thyroid hormone (5)
- diffuse into target cells and bind with intracellular receptors
- receptor-hormone complex enters nucleus; binds to specific region of dna
- prompts dna transcription to produce mRNA
- mRNA directs protein synthesis
- promote metabolic activities, or promote synthesis of structural proteins or protein for export from cell
target cells must have ______ _______ to which hormone binds
specific receptors
examples of specific receptors are:
ACTH receptors found only on certain cells of adrenal cortex
thyroxin receptor found on nearly all cells of body
Direct gene activation mechanism of lipid soluble hormones ( 5 steps)
- steroid hormone diffuses through the plasma membrane and binds an intracellular receptor
- receptor hormone complex enters nucleus
- receptor hormone complex binds specific DNA region
- binding initiates transcription of gene to mRNA
- mRNA directs protein synthesis
what 3 factors do target cells activation depend on
- blood levels of hormone
- relative number of receptors on or in target cell
- affinity of binding between receptor and hormone
target cells form more receptors in response to low hormone levels
up regulation
target cells lose receptors in response to high hormone levels
down regulation
these are controlled by negative feedback systems
vary only within narrow, desirable range
blood levels of hormones
endocrine gland stimulated to synthesize and release hormones in response to (3)
hormonal stimuli
neural stimuli
humoral stimuli
nerve fibers stimulate hormone release
neural stimuli
sympathetic nervous system fibers stimulate adrenal medulla to secrete ___
catecholamines
Stimulus: action potentials in preganglionic sympathetic fibers to adrenal medulla
- what is the response
- is this humoral, neural or hormonal stimuli
response: adrenal medulla cells secrete epinephrine and norepinephrine
neural stimuli
changing blood levels of ions and nutrients directly stimulate secretion of hormones
example: ca in blood
humoral stimuli
Stimulus: low concentration of CA in capillary blood
What is the response? Is this neural, humoral or hormonal stimuli?
Response: Parathyroid glands secrete parathyroid hormone (PTH), which increases blood Ca
Humoral stimuli
hormones stimulate other endocrine organs to release their hormones
hormonal stimuli
Stimulus: Hormones from hypothalamus
What is the response? Is this humoral, neural, or hormonal stimuli?
Response: Anterior pituitary gland secretes hormones that stimulate other endocrine glands to secrete hormones
Hormonal stimuli
hypothalamic hormones stimulate release of most ____ _____ hormones
anterior pituitary
____ _____ hormones stimulate targets to secrete still more hormones
anterior pituitary
what is the hypothalamic-pituitary target endocrine organ feedback loop
hormones from final target organs inhibit release of anterior pituitary hormones
nervous system modifies stimulation of _____ _____ and their negative feedback mechanisms
endocrine glands
what can override normal endocrine controls
nervous system
what hormones circulate in blood free and which ones are bound
- steroid and thyroid hormone are attached to plasma proteins
- all others circulate without carriers
the concentration of circulating hormone reflects what two things
- rate of release
2. speed of inactivation and removal from body
what 3 things remove hormones from blood
- degrading enzymes
- kidneys
- liver
time required for hormone’s blood level to decrease by half
half life
- these are limited
- ranges from 10 secs to several hours
- effects may disappear as blood levels drop
- some persist at low blood levels
duration of hormone activity
what is the onset of hormone activity
- some are immediate
- some hours to days
- some must be activated in target cells
what hormones act on same target at same time (3)
permissiveness, synergism, antagonism
one or more hormones oppose action of another hormone
antagonism
more than one hormone produces same effects on target cell —> amplification
synergism
one hormone cannot exert its effects without another hormone being present
permissiveness
pituitary gland has two major lobes
posterior - neural tissue
anterior - glandular tissue
these are transported to and stored in posterior lobe of pituitary
neurohormones
nuclei of hypothalamus synthesize neurohormones ____ and ____
this takes place in _____ lobe of pituitary
oxytocin & antidiuretic hormone (ADH)
posterior
downgrowth of hypothalamic neural tissue
neural connection to hypothalamus
posterior lobe of pituitary
originates as outpocketing of oral mucosa
vascular connection to hypothalamus
anterior lobe of pituitary
hypothalamus controls release of hormones from posterior lobe of pituitary
(4)
- hypothalamic neurons synthesize oxytocin or antidiuretic hormone (ADH)
- oxytocin and adh are transported down axons of hypothalamic - hypophyseal tract to posterior pituitary
- oxytocin and adh are stored in axon terminals in posterior pituitary
- when hypothalamic neurons fire, action potentials arriving at axon terminals cause oxytocin or adh to be released into blood
contains primary capillary plexus, hypophyseal portal veins, secondary capillary plexus
hypophyseal portal system of anterior lobe of pituitary gland
the hypophyseal portal system carries _____ and ____ hormones to anterior pituitary to regulate hormone secretion
releasing and inhibiting hormones
The hypothalamus controls release of hormones from the pituitary gland in two different ways - anterior lobe
- when appropriately stimulated, hypothalamic neurons secrete releasing or inhibiting hormones into the primary capillary plexus
- hypothalamic hormones travel through portal veins to the anterior pituitary where they stimulate or inhibit release of hormones made in anterior pituitary
- in response to releasing hormones the anterior pituitary secretes hormones into the secondary capillary plexus. in turn this empties into general circulation.
hypothalamic neurons synthesize
GHRH, GHIH, TRH, CRH, GnRH, PIH
hormones that come out of the anterior lobe of pituitary
GH, TSH, ACTH, FSH, LH, PRL
- inhibits or prevents urine formation
- regulates water balance
- target kidney tubules - reabsorb more water
- release also triggered by pain, low blood pressure and drugs
ADH
- strong simulant of uterine contraction
- released during childbirth
- hormonal trigger for milk ejection
oxytocin
hormones of the anterior pituitary hormone
*KNOW FOR TEST
- growth hormone (GH)
- thyroid-stimulating hormone (TSH)
- adrenocorticotropic hormone (ACTH)
- follicle-stimulating hormone
- luteinizing hormone (LH)
- prolactin (PRL)
- produced by somatotropic cells
- direct actions on metabolism
- increases blood levels of fatty acids; encourages use of fatty acids for fuel; protein synthesis - indirect actions on growth
- mediates growth via growth-promoting proteins - insulin like growth factors
- major targets - bone and skeletal muscle
growth hormone (GH)
GH release chiefly regulated by hypothalamic hormones
- growth hormone - release hormone (GHRH)
- stimulates release
- growth hormone-inhibiting hormone (GHIH)
- inhibits release
hunger hormone also stimulates release
ghrelin
hypersecretion in children results in
gigantism
hyposecretion in children results in
pituitary dwarfism
- produced by thyrotropic cells of anterior pituitary
- stimulates normal development and secretory activity of thyroid
- release trigged by thyrotropin releasing hormone from hypothalamus
thyroid stimulating hormone
- secreted by corticotropic cells of anterior pituitary
- stimulates adrenal cortex to release corticosteroids
adrenocorticotropic hormone (ACTH)
- follicle stimulating hormone (FSH) and luteinizing hormone (LH)
- secreted by cells of anterior pituitary
- FSH stimulates gamete (egg or sperm) production
- LH promotes production of gonadal hormones
gonadotropins (FSH and LH)
regulation of gonadotropin release
- triggered by gonadotropin-releasing hormone (GnRH) during and after puberty
- suppressed by gonadal hormones
- secreted by cells of anterior pituitary
- stimulates milk production
- role in males not well understood
- regulation of PRL release
- primarily controlled by prolactin inhibiting hormone
prolactin (PRL)
regulation of ACTH release
- triggered by hypothalamic corticotropin releasing hormone in daily rhythm
- internal and external factors such as fever, hypoglycemia, and stressors can alter release of CRH
another name for prolactin-inhibiting hormone
dopamine
regulation of thyroid hormone secretion
hypothalamus —-TRH— anterior pituitary —-TSH—– thyroid gland —- thyroid hormones —- target cells