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84 Cards in this Set

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  • Back
What is paracrin communication?
The use of chemical messengers to transfer information from cell to cell within a single tissue.
What are hormones?
Chemical messengers that released in one tissue and transported in the bloodstream to reach specific cells in other tissues (the target cells).
What is endocrine communication?
The use of hormones to coordinate cellular activities in tissues in distant portions of the body.
What is included in the endocrine system?
All endocrine cells and tissues of the whole body which release hormones.
What are endocrine glands?
-"ductless" glands
-Many are made of glandular epithelium whose cells manufacture and secrete hormones
-Some made of neurosecretory tisssue
-located throughout the body
What three groups can hormones be divided into?
-amino acid derivatives
-peptide hormones
-lipid derivatives
Describe Amino acid derivatives.
-small molecules structurally related to amino acids
-synthesized from the amino acids tyrosine and tryptophan
What are the tyrosine derivatives?
-Thyroid hormones
-epinephrine
-norepinephrine
-dopamine (aka catecholamines)
What are the tryptophan derivatives?
-melatonin
What are peptide hormones?
-chains of amino acids
-2 groups (glcoproteins, short polypeptides)
What are the different glycoproteins?
*>200 amino acids long, with carb side chain
-TSH: thyroid-stimulating hormone
-LH: Luteinizing hormone
-FSH: Follicle stimulating hormone
What are the short polypeptides?
*under 200 amino acids long
-All hormones secreted by hypothalamus, heart, thymus, digestive tract, pancreas, and pituitary gland.
What are the two classes of lipid derivatives?
1) eicosanoids
2) steroid hormones
What are eicosanoids?
-derived from arachidonic acid
-include prostaglandins
What are steroid hormones?
-derived from cholesterol
-released by:
+reproductive organs
+adrenal glands
+kidneys
How can hormones move through the blood?
-freely
-bound to transport proteins
How long are free hormones active for and how do they move?
about an hour or more
-diffues out of bloodstream and bind to receptors in target tissues
-absorbed and broken down by cells of the liver or kidneys
-broken down by enzymes in the plasma or interstitial fluids
What are target cells?
Speceific receptor cells that determine hormonal sensitivity.
How is hormonal sensitivity determined?
Presence or absense of specific receptor (target) cells.
What is a receptor?
A protein molecule to which a particular molecule binds strongly in a "lock-and-key" mechanism.
What are the steps of hormones acting on target cells (and what is each one)?
-receptor activation (by input signal: the hormone)
-conversion (of input signal to biochemical change in cell)
-response (synthesis, transport, secretion, contraction, breakdown)
What are the combined hormone actions (3)?
-synergism
-permissiveness
-antogonism
How are the combined hormone actions determined?
Differernt tissues have different combinations of receptors for various hormones.
What is synergism?
Combinations of hormones acting together have a greater effect on a target celll than the sum of the effects that each woiuld have if acting alone.
What is permissiveness?
A small amount of one homrone allows a second one to have its full effects on a target cell.
What is antagonism?
One hormone produces the apposite effects of another hormone; used to "fine tune" the activity of target cells with great accuracy.
Describe catecholamines and peptide hormones.
-not lipid soluble
-unable to penetrate cell membrane
-bind to receptor proteins at outer surface of cell membrane (extracellular receptors)
Describe eicosanoids and steroid hormones.
-lipid soluble
-diffuse across membrane to reach reveptor proteins on inner surface of membrane (intracellular membranes)
Describe thyroid hormones
-enter cell by transport proteins
-bind to reveptors in cytoplasm, on mitochondria membrane, or in the nucleus.
What are the different types of locations for hormone receptors?
-catecholamines and peptide hormones
-eicosanoids and steroid hormones
-thyroid hormones
How is the effect of a hormone on a target cell altered?
-through amplification
What is a second messenger?
-It functions IN a cell as an enzyme activator, inhibitor, or cofactor.
What are the mechanisms through 'cell membrane' receptors?
hormone (first messenger), G protein, second messenger
What are some common second messengers (and derivatives)?
-cyclic AMP (cAMP; derivatives of ATP)
-cyclic GMP (cGMP; derivatives of GTP)
-calcium ions
What are the mechanisms through 'intracellular receptors'?
-steroid and thyroid hormones cross cell membrane
-bind to receptors in cytoplasm or nucleus
How does intracellular receptor bonding affect cytoplasm or nucleus?
-alter rate of DNA transcription in nucleus (change patterns of protein synthesis)
-directly affect metabolic activity and structure of target cell
What is a simple negative feedback mechanism?
A stimulus tiggers the production of a hormone whose direct or indeirect effects reduce the intensity of the stimulus.
How are endocrine reflexes usually controlled?
Through negative feedback mechanisms (they are the counterparts of neural reflexes)
Describe the hypothalamus.
-the highest level of endocrine control
-controls more-complex endocrine functions
-integrates activities of nervous and endocrine system in 3 ways
What are the three ways the hypothalamus controls nervous and endocrine systems?
1) secretes regulatory hormones (control endocrine cells in pituitary gland which in turn controls activities of other endocrine organs)
2) acts as an endocrine organ (release of ADH and Oxytocin)
3) contains autonomic centers (exert direct neural control over endocrine cells of adrenal medullae)
Describe what the pituitary gland looks like (what is is called?).
Hypophysis:
-small oval gland
-located on ventral surface of brain, under hypothalamus
-has infundibulum (connects pituitary to hypothalamus)
-made of two separate glands (anterior p.g= adenohypophysis and posterior p.g= neurohypophysis)
Describe they anterior pituitary gland.
-Three regions: pars distalis, pars tuberalis, pars intermedia
-median eminence
What is median eminence?
Where hypothalamic neurons release regulatory factors into:
-interstitial fluids
-through fenestrated capillaries
What are fenestrations?
Small openins or holes in the walls of the glomerular capillaries allowing certain molecules to leave that would normally be too large to leave.
What does the hypophyseal portal system do?
Ensures that regulatory factors reach intended target cells before entering general circulation.
What are portal vessels?
-blood vessels that link 2 capillary networks (entire complex is the portal system).
What are the two hormones secreted by the hypothalamus to control the anterior pituitary?
Both regulatory hormones:
-releasing hormone (RH)
-inhibiting hormone (IH)
What do RH's do?
-stimulates synthesis and secretion of one or more hormones
-transported by hypophyseal portal system
-rate of secretion by hypothalamus controlled by negative feedback
What do IH's do?
-prevent syntheiss and secretion of hommones
What are 7 hormones secreted by the anterior pituitary?
1) thyroid-stimulating hormone (TSH)
2) andrenocorticotropic hormone (ACTH)
3) gonadotropin (FSH)
4) gonadotropin (LH)
5) prolactin (PRL)
6) growth hormone (GH)
7) melanocyte stimulating hormone (MSH)
What does TSH do?
-triggers release of thyroid hormones
-aka: thyrotropin
What does ACTH do?
-stimulates release of glucocorticoids by adrenal cortex
What does FSH do?
-stimulates follicle development and estrogen secretion in females
What does LH do?
-cuases ovulation and progestin production in females
-causes androgen production in males
What does PRL do?
-stimulates development of mamary glands
What does GH do?
-stimulates cell growth and replication
What does MSH do?
-stimulates melanocytes to produce melanin.
SEE page 20 for placement chart of anterior pituitary hormones.
Location, target, effect.
Describe the posterior pituitary gland.
-contains unmyelinated axons of hypthalamic neurons
-supraoptic and paraventricular nuclei manufacture:
antifiuretic hormone (ADH)
ocytocin (OT)
What does ADH do?
-targets kidneys
-stimulates reabsorption of water
-stimulates elevation of blood volume and pressure
What does OT do in females?
-targets uterus, mammary glands
-stimulates labor contractions
-stimulates milk ejection
What does OT do in males?
-targets vas deferens and prostate gland
-stimulates contractions of ductus deferens and prostate
Describe the thryoid gland
-lies near thyroid cartilage of the larynx
-consists of two lobes, which may be connected by the isthmus (depends on species)
What cells produce what in the thyroid gland?
-thryroid follicle cells release thyroid hormones
-clear (c) cells produce calcitonin
What is in the follicle cavity?
a viscous colloid
What are the two different thyroid hormones?
-tetraiodothyronine (T4), or thyroxine
-triiodothyronine (T3)
What happens with T3 and T4 production/release?
-attach to globulin molecules, forming thyroglobin complexes
-stored in colloid of follicles
-detach from globulin and enter bloodstream
-travel as hormone-globulin complex through blood
(I though they detached from globulin?)
What are the functions of the thyroid hormones?
-enter target cells by transport system
-affect most cells in body (a "general" target)
-bind to reveptors in cytoplasm, surfaces of mitochondria, and nucleus
-increase metabolic rate of all cells and cell growth and tissue differentiation
Describe calcitonin.
-produced by thyroid gland in the C cells
-aids in regulation of Ca2+ concentration in body fluids
-antagonist to parathyroid hormones
-control of calcitonin secretion is a direct endocrine regulation
How does calcitonin regulate reduction of Ca2+ concentration in body fluid?
-inhibition of osteoclasts, which slows the rate of Ca2+ release from bone
-stimulates excretion of Ca2+ at the kidneys.
Describe the parathyroid glands.
-4 to 5 parathyroid glands embedded in the posterior surfave of the thyroid's lateral lobes
-chief cells produce parathyroid hormone (PTH)
-regulated by direct negative feedback by blood Ca2+ levels (like calcitonin)
What are the functions of PTH?
Increase Ca2+ concentration in body fluids (antagonist to calcitonin) by:
-stimulating osteoclasts
-inhibiting osteoblasts
-enhancing the reabsorption of Ca2+ at the kidneys
Describe the adrenal glands.
-lLocated on top of kidneys, like caps
-made of two portions (adrenal cortex and medulla)
Describe the adrenal cortex.
-composed of endocrine tissue
-all corticalhomrones are steroids and known as corticosteroids
-three layers from outer to inner: zona glomerulosa, zona fasciculata, zona reticularis
What type of tissue makes up the adrenal medulla?
-neurosecretory tissue
Look at page 26 for Adrenal homrones.
Hormones, targets, effects.
Look at page 27 for pancreas hormones.
Hormones, targets, effects.
Describe the pancreas structure.
-elongated gland (head lies in duodenum, extends horizontally behind stomach and then touches spleen)
-composed of endocrine and exocrine tissues
Describe the endocrine tissue portion of pancreas.
1% Pancreatic islets (islets of Langerhans) which contain four cell types (alpha, beta, delta, F cells).
Describe the exocrine portion of pancreas.
99% acini which secretes a serous fluid containing digestive enzymes into ducts draining into the small intestine
Describe the testes
-paired organs within the scrotum in the male
-composed mainly of coils of sperm-producing seminiferous tubules and scattering of endocrine interstitial cells between the tubules
Describe the ovaries
-primary sex organ in female
-set of paired glands in pelvis
-contain follicles (lining cells secrete estrogen) which produce oocytes
-formation of corpus luteum after ovulation which produces progesterone
See page 29 for other endocrine tissues.
hormones, targets, effects.
What are the two categories of endocrin disorders?
1) abnormal hormone production
2) abnormal cellular sensitivity to hormones