Seeley's Anatomy and Physiology chapter 17

hormones secreted by three methods

-action of a substance other than a hormone on an endocrine gland -neural control of endocrine gland -control of secretory activity of one endocrine gland by hormone or neurohormone secreted by another endocrine gland.

Down regulation

A phenomenon by which the number of receptors rapidly decreases after exposure to certain hormones

Conjugation

A process by which lipid-soluble hormones are removed from the circulation when certain enzymes in the liver attach water-soluble molecules to the hormones

Chemical messengers

Allow cells to communicate with each other to regulate body activities autocrine paracrine neurotransmitters endocrine chemical messengers

Hormones

Derived from the Greek word 'hormon' which means set into motion. Stability, communication, distribution produced in small quantities secreted into intercellular space transported some distance in circulatory system acts on target tissues elsewhere. hormones dissolve in blood plasma and are transported in unbound or are reversibly bound to plasma proteins. hormones are distributed quickly because they circulate in the blood.

Endocrine

Derived from the Greek words 'endo', meaning within, and 'krino', to secrete

Inhibiting hormones

Hormones from the hypothalamus that prevent the secretion of tropic hormones from the pituitary gland

Free hormones

Hormones that dissociate from their binding proteins at their target tissues

Bound hormones

Hormones that requires transport assistance bind to blood proteins called binding proteins

Humoral stimuli

Molecules that circulate in the blood; the word humoral refers to body fluids, including blood when blood Ca2+ is too low parathyroid gland increases osteoclast activity to increase Ca2+

Releasing hormones

Neuropeptides that stimulate hormone secretion from other endocrine cells

Lipid soluble hormones

Nonpolar, include steroid hormones, thyroid hormones, and fatty acid derivative hormones

Hormonal stimuli

Occurs when a hormone is secreted that, in turn, stimulates the secretion of other hormones

Water soluble hormones

Polar, include protein hormones, peptide hormones, and most amino acid derivative hormones

Membrane bound receptors

Proteins that extend across the plasma membrane, with their hormone-binding sites exposed on the plasma membrane's outer surface. interact with hormones that cannot pass through the plasma membrane. water soluble or large molecular weight hormones. attachment of hormone causes intracellular reaction. large proteins, glycoproteins, polypeptides, smaller molecules like epinephrine and norepinephrine.

Receptors

Proteins to which hormones exert their actions by binding to them

Nuclear receptors

Receptors that are most often found in the cell nucleus. lipid soluble and relatively small molecules pass through membrane. react with enzymes in the cytoplasm or DNA to cause transcription and translation. thyroid hormones, testosterone, estrogen, progesterone, aldesterone, and cortisol.

Up regulation

Results from an increase in the rate of receptor molecule synthesis in the target cells

Secretion

The controlled release of chemicals from a cell

Receptor site

The portion of each receptor molecules where a hormone binds. specific to hormone.

Specificity

The tendency for each type of hormone to bind to one type of receptor, and not to others

nervous system v. endocrine system

both systems associated with brain -hypothalamus (pituitary gland) -epithalamus (pineal gland) may use same chemical messenger as neurotransmitter and hormone -epinephrine (both neurotransmitter and hormone from adrenal gland) 2 systems are cooperative -nervous system secretes neuroendocrine peptides or neurohormones into circulatory system -some parts of endocrine system innervated directly by nervous system nervous system responses very fast but short term endocrine system responses slow but long term

ligands

more general term for chemical signals

neurotransmitter

produced by neurons and secreted into extracellular spaces by presynaptic nerve terminals. travel short distances

action of nuclear receptors

proteins in cytoplasm or nucleus. hormones bind with intracellular receptor and receptor-hormone complex activate certain genes, causes transcription of mRNA and translation. These proteins (enzymes) produce the response of the target cell to the hormone. Estrogen and testosterone produce diff proteins in cells that cause the differing secondary sexual characteristics of females and males.

paracrine chemical messengers

released by cells and affect other cell types locally without being transported in blood.

apocrine chemical messengers

released by cells and have a local effect on the same cell type from which chemical signals released. eg. prostaglandin. injured or or inflamed cells, work on same cell

half life

the length of time it takes for half a dose of substance to be eliminated from circulatory system -long half life regulate activities that remain at a constant rate through time. usually lipid soluble and travel in plasma attached to proteins -short half life: water soluble hormones as proteins, epinephrine, norepinephrine. have a rapid onset and short duration. can't go in cell and dont bind to proteins.

endocrine chemical messengers

type of intercellular signal produced by cells of endocrine glands, enter circulatory system and affect distant cells