Term | Definition | |
endocrine cells | secretory cells that release hormones directly into the interstitial fluid, lymphatic system, or blood | |
hormones | chemical messengers that stimulate specific cells or tissues into action | |
amino acid derivatives | small molecules that are structurally similar to amino acids; class of hormones | e.g. derivatives of tyrosine such as thyroid hormones and catecholamines; derivatives of tryptophan such as melatonin |
peptide hormones | chains of amino acids; class of hormones | e.g. hormones released by the pituitary gland |
lipid derivatives | class of hormones that can be divided into eicosanoids and steroid hormones | |
eicosanoids | small molecules with a five-carbon ring at one end; derived from arachidonic acid; group of lipid derivatives | coordinate cellular activities and affect enzymatic processes (such as blood clotting) |
steroid hormones | group of lipid derivatives that are structurally similar to cholesterol | e.g. reproductive hormones; adrenal cortex hormones |
target cells | specific cells that have receptors needed to bind hormones and respond to their presence | |
humoral stimuli | changes in the composition of ECF; trigger endocrine activity | |
hormonal stimuli | arrival or removal of specific hormone(s); trigger endocrine activity | |
neural stimuli | arrival of neurotransmitters at neuroglandular junctions; trigger endocrine activity | |
negative feedback system | self-amplifying cycle where a physiological change leads to even greater change in the same direction | |
positive feedback system | process in which the body senses a change and activates mechanisms to reverse that change | |
hypothalamus | contains centers involved with the unconscious regulation of visceral functions, emotions, drives, and the coordination of neural and endocrine functions; makes up the floor of the diencephalon | |
pituitary gland (hypophysis) | major endocrine gland attached to the hypothalamus by the infundibulum | |
infundibulum | a tapering, funnel-shaped structure that connects the pituitary gland to the hypothalamus | |
diaphragm sellae | a dural sheet that encircles the infundibulum and holds the pituitary gland in position | |
hypophyseal portal system | capillary network that branches among endocrine cells in the anterior lobe | |
anterior lobe of the pituitary gland (adenohypophysis) | lobe of the pituitary gland made up of the pars distalis, pars tuberalis, and pars intermedia | |
pars distalis | large, anterior portion of the adenohypophysis | |
pars tuberalis | portion of the adenohypophysis that wraps around the infundibulum superior to the posterior lobe | |
pars intermedia | portion of the adenohypophysis that is adjacent to the neurohypophysis | |
thyroid-stimulating hormone (TSH) | anterior pituitary hormone secreted by thyrotropes in the pars distalis | targets the thyroid gland, triggering release of thyroid hormones T3, T4, CT |
adrenocorticotropic hormone (ACTH) | anterior pituitary hormone secreted by corticotropes in the pars distalis | targets the adrenal cortex, stimulating secretion of glucocorticoids (GC) |
follicle-stimulating hormone (FSH) | anterior pituitary hormone secreted by gonadotropes in the pars distalis | targets follicular cells in the ovaries or nurse cells in the testes, stimulating secretion of estrogens and promoting development of oocytes or sperm |
luteinizing hormone (LH) | anterior pituitary hormone secreted by gonadotropes in the pars distalis | targets follicular cells in the ovaries or interstitial cells in the testes, stimulating ovulation and promoting secretion of progestins or androgens |
prolactin (PRL) | anterior pituitary hormone secreted by lactotropes in the pars distalis | targets the mammary glands, stimulating the production of milk |
growth hormone (GH) | anterior pituitary hormone secreted by somatotropes in the pars distalis | targets all cells, stimulating growth, protein synthesis, lipid mobilization, and catabolism; in the liver, causes the release of somatomedins, which stimulate protein synthesis in cartilage and muscle cells |
melanocyte-stimulating hormone (MSH) | anterior pituitary hormone secreted by corticotropes in the pars intermedia | targets melanocytes, stimulating increased melanin production |
thyrotropes | endocrine cells in the pars distalis of the adenohypophysis that secrete TSH | |
corticotropes | endocrine cells in the pars distalis and pars intermedia of the adenohypophysis that secrete ACTH and MSH | |
gonadotropes | endocrine cells in the pars distalis of the adenohypophysis that secrete FSH and LH | |
lactotropes | endocrine cells in the pars distalis of the adenohypophysis that secrete PRL | |
somatotropes | endocrine cells in the pars distalis of the adenohypophysis that secrete GH | |
posterior lobe of the pituitary gland (neurohypophysis) | lobe of the pituitary gland that stores and releases ADH and OXT | hormones released are called neurosecretions |
antidiuretic hormone (ADH) | aka vasopressin; neurosecretion released in response to a rise in electrolyte concentration or a fall in blood pressure | targets nephrons of the kidneys, causing kidneys to retain water (preventing dehydration) and peripheral blood vessels to constrict (elevating blood pressure) |
oxytocin (OXT) | neurosecretion targeting the smooth muscle of the uterus or prostate gland and contractile cells of the mammary glands | causes uterine or prostate gland contractions, release of milk |
thyroid gland | gland located on the anterior surface of the trachea slightly inferior to thyroid and cricoid cartilages | supplied by the superior thyroid artery (from the external carotid artery) and the inferior thyroid artery (from the thyrocervical trunk) |