Flashcards in Bergdahl- Chapter 20 Deck (68):
describe the ducts of the endocrine system
no ducts ! they secrete substances directly into extracellular spaces around the gland
what is a half-life ?
time required to reduce a hormone's blood concentration by a half, and gives an indication on how long its effect persists
how are steroid hormones different from amine and peptide hormones ?
they're not soluble in blood plasma
what are 4 ways that a hormone can specifically target a cell ?
1) modify rate of intracellular protein synthesis by stimulating nuclear DNA
2) change rate of enzyme activity
3) alter plasma membrane transport with a second-messenger system
4) induce secretion
what is the first step in initiating hormone action ?
what are the three things that a target cell's activation by a hormone depends on ?
1) hormone concentration in blood
2) number of target cell receptors for hormone
3) sensitivity or strength of union between hormone and receptor
what are 3 ways that a hormone can increase enzyme activity ?
1) stimulate its production
2) combine with it to alter its shape and ability to act, increasing or decreasing its catalytic effectiveness
3) activating inactive enzyme forms, therefore increasing total amount of active enzyme
what are 4 factors that determine plasma concentration of a hormone ?
1) quantity synthesized in host gland
2) rate of catabolism or secretion in blood
3) quantity of transport proteins present
4) plasma volume changes
what does "secreted amount" mean ?
the plasma concentration of a hormone
the sum of hormone synthesis and release by host gland, in addition to uptake by tissues and removal by liver and kidneys
can changes in plasma volume alter hormone concentration ?
yeah, independent of the host organ's secretion rate
what is hormonal stimulation ?
hormones influencing secretion of other hormones (eg ACTH)
what is humoral stimulation ?
changing levels of ions and nutrients stimulate hormone release (ADH, insulin)
what is neural stimulation ?
neural activity affects hormonal release (catecholamines)
what does a mean concentration of a hormone at a given time indicate ?
not much. the half-life and the pattern of release is much more significant
what controls the 6 releasing factors (hypothalamic hormones) ?
neural input to the hypothalamus from anxiety, stress, physical activity
what is growth hormone's main mission ?
to promote cell division and cellular proliferation throughout the body
in adults, what are the 3 ways that GH promotes protein synthesis ?
1) increase aa transport through membrane
2) stimulate RNA formation
3) activate ribosomes that increase protein synthesis
what energy sources does GH promote or inhibit?
less protein and carbs, more fat utilization
how does training affect GH?
extends GH's action on target tissues
what mediates GH's effects ?
Insulin-like Growth Factors
what is thyrotropin's main role ?
thyrotropin = thyroid-stimulating hormone
controls hormone secretion by thyroid gland
what is adenocorticotropic hormone's main use ?
acts directly to enhance fatty acid mobilization and stimulate protein catabolism and increase gluconeogenesis
what are the two hormones that mediate ACTH release ?
vasopressin and corticotropin-releasing hormone
what is prolactin's main role ?
initiates and supports milk secretion from mammary glands
how do prolactin levels change in exercise ?
increase at high intensities and return to baseline within 45 min during recovery
how is prolactin involved in training adaptations ?
exercise-induced release may inhibit ovarian function and contribute to menstrual cycle alterations
what is the main role of gonadotropic hormones ? what are they called ?
stimulate male and female sex organs to grow and secrete hormones at faster rate
follicle-stimulating hormone and luteinizing hormone
what are the two posterior pituitary hormones ?
ADH and oxytocin
what is the main role of ADH
what happens to ADH during physical activity ?
stimulus for secretion in order to help conserve body fluids
what does T4 do ?
raises metabolism of all cells except brain, spleen, sex, and thyroid gland
what does T3 do ?
facilitates neural reflex activity
how do thyroid hormones influence BP ?
by provoking an increase in adrenergic receptors in blood vessels
what are 4 effects of hyperthyroidism ?
1) increased VO2 and metabolic heat production at rest
2) increased protein catabolism
3) heightened reflex ability- irritability, insomnia
4) rapid HR
what are 4 effects of hypothyroidism ?
1) reduced metabolic rate
2) decreased protein synthesis
3) depressed reflex- sluggishness
4) slow HR
what does parathyroid hormone do ?
control blood calcium balance
decrease in calcium triggers PTH release
what hormones come out of the adrenal cortex ?
mineralocorticoids, glucocorticoid, and androgens
what does aldosterone do ?
a mineralocorticoid, regulates minerals like Na+ concentration, stimulates ion reabsorption
what does cortisol do ?
a glucocorticoid, promotes breakdown of energy sources
what are distinctly male and female hormones ?
what are the two hormones from the pancreas and where are they secreted ?
alpha cells: glucagon
beta cells: insulin
is pancreas endocrine or exocrine ?
both. islets are endocrine, acini are exocrine
how is GLUT 1 different from GLUT 4 in glucose transport ?
GLUT 1 moves glucose based on concentration difference
GLUT4 requires insulin to undergo a conformational change and transport glucose
what directly controls insulin secretion ?
blood glucose levels in pancreas
why does no excessive insulin release occur with a concentrated glucose feeding during physical activity ?
less blood flow to the pancreas since it's not a crucial organ
what does glucagon do ?
stimulates glycogenolysis and gluconeogenesis, and increases lipid use too.
does exercise training enhance GH secretion and conserve glycogen reserve ?
how is blood GH different in trained individuals ?
endurance-trained people have less of a rise in blood GH levels because there is less exercise stress
how are women's GH levels different from men's in exercise ?
they're the same
women's are higher at rest
how does training affect ACTH release ? how does this change the metabolism ?
therefore increases fat catabolism and spares glycogen
how do prolactin levels differ in trained individuals ?
at rest, they're lower in male runners than in sedentary nonrunners
how does reproductive response vary with physical activity level ?
exercise depresses reproductive hormone response
lower testosterone levels for example
lower FSH and LH in women
what is the difference in LH and FSH levels between trained and untrained men ?
there is none
there's only lower levels in trained women
how does exercise impact aldosterone levels ?
how does exercise impact cortisol levels ?
levels increase less in trained people
when can adrenal gland enlargement occur ?
with repeated bouts of intense exercise training
how does catecholamine activity differ in trained individuals ?
in general there is a reduction in HR and BP, so lower levels
HOWEVER, relatively, there is a higher response that occurs following aerobic training
if there is a greater catecholamine output at the same relative exercise intensity following training, what 3 factors could explain the greater SNS activation ?
1) greater demand for substrate use
2) increased overall cardiovascular response
3) larger muscle mass activation
how does glucagon and insulin concentration vary with training status ?
with time, trained have less and requires less
what are 3 ways that exercise can improve insulin action ?
1) translocation of GLUT 4 from endoplasmic reticulium to cell surface
2) increase in total quantity of GLUT 4
3) increase in glycogen synthase activity and therefore storage
what tissue consumes the major amount of glucose transported in blood ?
how does intense exercise improve long term glycemic control ?
a bout decreases plasma glucose for a long time
the immediate effects increase the active muscles' insulin sensitivity, which causes long-term improvement in glycemic contol
what are the two primary hormones that affect adaptations to resistance training ?
GH and testosterone
what are 3 hormonal factors responsible for exercise induced changes in muscle size and function ?
1) changes in hepatic and extrahepatic hormone clearance rates
2) differential rates of hormone secretion
3) altered receptor site activation via neurohumoral control
what are short term effects of moderate and maximal exercise on the immune system ?
MODERATE: boosts natural immune function up to several hours
EXHAUSTIVE: severely depresses the body's first line of defense due to strenuous exertion
what are long term effects of aerobic exercise on immune system ?
positively affects natural immune function during weight loss
what 2 areas of improvement of immune system in long-term aerobic exercise ?
1) enhanced functional capacity of natural cytotoxic immune mechanisms
2) diminished age-related decrease in T-cell function