Ch 5: hormonal responses to exercise

neuroendocrinology

branch of physiology focused on control systems

nervous system releases _______ to relay messages from nerve to nerve or from nerve to tissues

neurotransmitters

endocrine system released hormones from _________ in the blood to reach target tissues

endocrine glands

hormones (______) bind to specific proteins (____) on target tissues and alter the activity of those tissues

ligands; receptors

ligand-receptor interaction causes a response in the target cell called

signal transduction

classes of hormones: hormones can be divided based on chemical make up into:

amino acid derivatives

peptides

proteins

steroids

the structure of a hormone determines its mechanisms of

transport and signal transduction (how it exerts its effects)

the most important chemical characteristic is whether the hormone can

dissolve in water or cross the plasma membrane (lipid bilayer)

lipophilic hormones

lipid-soluble; cross membrane easily, don’t dissolve in water

lipophobic hormones

water-soluble; don’t cross membrane, do dissolve in water

hormone effectiveness: hormone effect on a tissue is influenced by

the number of receptors available for binding and the plasma concentration of the hormone

plasma concentration of a hormone is determined by:

rate of secretion of hormone from the endocrine gland

rate of metabolism or excretion of hormone

quantity, capacity, and affinity of transport proteins

changes in plasma volume

rate of secretion of hormone from the endocrine gland includes

the magnitude of the input; excitatory or inhibitory input

rate of metabolism or excretion of hormone

hormone inactivation at the receptor and/or removal by liver and kidneys

quantity, capacity, and affinity of transport proteins

steroids and thyroid hormones are transported bound to a protein but to exert their effects they need to be “free” to interact with the receptor

changes in plasma volume

during exercise, plasma volume decreases which causes a slight increase in hormone concentration in plasma

____________ release hormones directly into the blood to alter the activity of tissues possessing receptors to which that hormone can bind

endocrine glands

the _____________ and _____________ determine the magnitude of the hormone effect at the tissue level

number of receptors available; plasma concentration of the hormone

the plasma hormone concentration can be changed by altering the rate of ______ or ______ and ______ of the hormone, the quantity, capacity and affinity of _______________, and the plasma __________.

secretion; metabolism; excretion; transport proteins; volume

increased plasma glucose ________________ pancreatic islet beta cells, increased insulin secretion

excites

increased plasma amino acids _________ pancreatic islet beta cells, increased insulin secretion

excites

incretins (from our gut and increases when we eat) ________________ pancreatic islet beta cells, increased insulin secretion

excites

sympathetic activity/plasma epinephrine ________________ pancreatic islet beta cells, increased insulin secretion

inhibits

increased parasympathetic activity ________________ pancreatic islet beta cells, increased insulin secretion

excites

many hormones are _______________ upon binding

altered or destroyed

excess hormones are removed form the blood by

liver and kidneys

liver removing excess hormones from the body

metabolizes hormones (major site of hormone metabolism)

kidneys removing excess hormones from the blood

metabolize or excrete excess hormones into the urine

during exercise what happens to blood flow to the liver and kidneys

blood flow decreases, redirected to muscles

how might redirection of blood flow during exercise impact the rate of hormone metabolism and excretion during exercise

high intensity exercise, decrease VO2 max

how would the redirection of blood flow during exercise impact blood hormone concentrations levels during exercise

decrease

hormone-receptor interactions: hormones are carried to all tissues but only affect

tissues with specific receptors (proteins) capable of binding those hormones

magnitude of the effect of hormone-receptor interactions depends on

concentration of the hormone, number of receptors on the cell, affinity of the receptor for the hormone

downregulation

decrease in receptor number in response to chronically high concentration of hormone

upregulation

increase in receptor number in response to chronically low concentraqtion of hormone

chemicals with similar shape as a hormone will

compete for the limited receptor sites

receptors can be located in various parts of the cell such as

membrane, cytoplasm, nucleus

aging results in

higher sympathetic activity and higher epinephrine/norepinephrine levels

altering activity of DNA to modify protein synthesis

steroid hormones

activating second messengers via G protein involves

cyclic AMP, Ca2+, inositol triphosphate, diacylglycerol

altering membrane transport

insulin via tyrosine kinase

mechanisms of hormone action

altering activity of DNA to modify protein synthesis, activating second messengers via G protein, altering membrane transport

altering activity of DNA in the nucleus involves

lipophilic hormones

examples of lipophilic hormones

steroids and thyroid hormones

lipophilic hormone receptor is in

cytoplasm (translocation - to the nucleus) or in the nucleus

effects of lipophilic hormones

slow acting, longer lasting effects

mechanism of steroid hormone action

1. hormone passes through plasma membrane

2. inside target cell the hormone binds to a receptor protein in the cytoplasm or nucleus

3. hormone-receptor complex binds to hormone response element on DNA, regulating gene transcription

4. protein synthesis

5. change in protein synthesis is cellular response

hormones bind receptors located on the outer surface of the cell membrane and active ___________ in or near the membrane to increase movement of some ion or substrate from outside to inside the cell

carrier molecules

some hormones cannot easily cross cell membranes because

these hormones are too large or highly charged

too large or too highly charged molecules exert their effects by

binding to a receptor on the membrane surface and activating a G protein located in the membrane

the G protein is the link between

the hormone-receptor interaction and the subsequent events inside the cell

the G protein may activate an enzyme in the membrane or open an ion channel to callow

Ca2+ to enter the cell

example of second messenger pathway

1. hormone binds to receptor

2. activates g protein

3. g protein activates adenylate cyclase

4. cellular response and glycolysis and triglyceride breakdown commence

Calcium channel activation

g protein can activate calcium ion channels, calcium enters the cell adn activates calmodulin

calcium channel activation and activation of membrane bound phospholipase C are not independent because

changes in one can affect action of the other

activation of membrane-bound phospholipase C

phosphotidylinositol (PIP2) is hydrolyzed to:

inositol triphosphate (IP3) → intracellular calcium release

diacylglycerol → activates protein kinase C

the hormone _______ interaction triggers events in the cell

receptor

changing the _________ of the hormone, the ________ of receptors on the cell, or the _______ of the receptor for the hormone will all influence the magnitude of the effect

concentration; number; affinity

hormones bring about their effects by:

• activating/suppressing genes to alter ________

• activating ______

• modifying membrane _______

protein synthesis; second messengers; transport

hormones are secreted from

endocrine glands

major endocrine glands include

hypothalamus and pituitary gland

thyroid and parathyroid glands

adrenal glands

pancreas

testes and ovaries

growth hormone secreted by

anterior pituitary gland

growth hormone stimulates

release of insulin-like growth factors (IGFs)

IGF-1 is responsible for

muscle hypertrophy

growth hormone is essential for

normal growth of all tissues (stimulates amino acid uptake and protein synthesis, long bone growth)

growth hormone spares

plasma glucose

growth hormone spares plasma glucose: opposes ________ action, ________________________

insulin; reduces the use of plasma glucose

growth hormone spares plasma glucose: increases ___________ in the liver

gluconeogenesis

growth hormone spares plasma glucose: mobilizes ________ from adipose tissue

fatty acids

GH ___________ protein synthesis in muscle and long bine growth

increases

effects of GH increasing protein synthesis in muscle and long bone growth

used to treat childhood dwarfism, used by athletes and elderly

high doses of GH results in

more adverse effects than benefits

no evidence that GH supports

strength gains (minimal strength gains compared to resistance training alone)

GH has questionable benefits as

anti aging therapy

antidiuretic hormone (ADH) or vasopressin is secreted by

hypothalamus

ADH stored/released by

posterior pituitary gland

ADH reduces

water loss from the body to maintain plasma volume

ADH favors

reabsorption of water from kidney tubules to capillaries

ADH release is stimulated by

high plasma osmolality (low water concentration) and low plasma volume due to sweat loss and without water replacement

ADH levels ______ during exercise >60% VO2 max

increase (to maintain plasma volume)

thyroid gland stimulated by

TSH

thyroid gland hormones

triiodothyronine (T3) and thyroxine (T4)

T3 and T4 influence

resting metabolic rate

T3 and T4 as permissive hormones

permit full effect of other hormones

calcitonin is involved in

regulation of plasma calcium (blocks calcium release from bone, stimulates excretion by kidneys)

adrenal gland is ______ glands

2

adrenal medulla secretes

catecholamines

catecholamines

epinephrine and norepinephrine

epinephrine and norepinephrine

fast acting hormones, part of fight or flight response

adrenal cortex secretes

steriod hormones derived from cholesterol

mineralocorticoids

aldosterone

glucocorticoids

cortisol

sex steroids

androgens and estrogens

catecholamines: epinephrine (adrenaline) ____ and norepinephrine _____

80%; 20%

catecholamines bind _______ receptors and change cellular activities via second messengers __________

adrenergic; alpha receptors (alpha 1, alpha 2) and beta receptors (beta 1, beta 2, beta 3)

magnitude and direction (inhibitory vs excitatory) of the response depends on

which ligand binds with which receptor

beta 1 effect of E/NE

E = NE

beta 1 membrane bound enzyme

adenylate cyclase

beta 1 intracellular mediator

increase cyclic AMP 2

beta 1 effects on various tissues

increase heart rate, increase glycogenolysis, increase lipolysis