Chr. 18 - The Endocrine System Flashcards
[18.1] What is a hormone?
A molecule released in one part of the body regulating activity of cells in other parts of the body.
[18.2] What is an exocrine gland?
A gland secreting into ducts carrying hormones to body cavities, lumen of organs, or outer surface of body.
[18.2] What is an endocrine gland?
A gland secreting hormones into interstitial fluid surrounding the secretory cells, diffusing into blood stream and travelling to target cells.
[18.3] What is down-regulation?
A decrease in protein receptors in cells in response to a large amount of hormone.
[18.3] What is up-regulation?
An increase in protein receptors in cells in response to a deficiency in a hormone.
[18.3] What are circulating hormones?
Hormones that are releasing into interstitial fluid and travel into the blood. Inactivated over a long duration due to their nature of lingering in blood.
[18.3] What are local hormones?
Hormones that act on neighbouring cells, or the cell that secreted them. Inactivated quickly.
[18.3] What are paracines?
Local hormones acting on neighbouring cells.
[18.3] What are autocrines?
Local hormones acting on the secreting cell.
[18.3] What are the chemical classes of hormones?
Lipid-soluble and water-soluble.
[18.3] What are the classes of lipid-soluble hormones?
Steroid, thyroid, and nitric oxide.
[18.3] What are steroid hormones?
Unique hormones each derived from cholesterol
[18.3] What are thyroid hormones?
T3 and T4, synthesized from tyrosine and iodine.
[18.3] What are the classes of water-soluble hormones?
Amine, peptide/protein, and eicosanoid.
[18.3] What are amine hormones?
Hormones derived from amino acids.
[18.3] What are peptide hormones?
Amino acid polymers acting as hormones, including protein and glycoprotein hormones.
[18.3] What are eicosanoid hormones?
Hormones derived from arachidonic acid.
[18.3] What are the classes of eicosanoid hormones?
Prostaglandins and leukotrienes.
[18.3] What are transport proteins in relation to hormones?
Proteins synthesized in the liver transporting lipid-soluble hormones in blood.
[18.3] List the functions of transport proteins in relation to hormones.
- Turning lipid-soluble hormones temporarily water-soluble for travel in blood.
- Partially inhibit hormone molecules from being filtered in kidneys.
- Provide a reserve of hormones in blood.
[18.3] What is the free faction?
The percentage (0.1% - 10%) of lipid-soluble hormone not bound to transport proteins.
[18.4] List the steps in the mechanism of action for lipid-soluble hormones.
- Lipid-soluble hormones diffuse from blood through lipid bilayer of cell.
- Hormone binds to receptors within cytosol or nucleus altering gene expression.
- New mRNA forms and paths to the ribosome for synthesize of proteins.
- Proteins generated from new mRNA alter activity of the cell and cause a response.
[18.4] List the steps in the mechanism of action for water-soluble hormones.
- Hormone diffuses from blood to exterior receptor in target cells plasma membrane, activating adenylyl cyclase.
- Adenylyl cyclase converts ATP to cAMP within the cell.
- cAMP activates protein kinases in cytosol.
- Activated protein kinases phosphorylate proteins, activating or deactivating based on protein.
- Phosphorylated proteins cause reactions producing physiological responses.
- Phosphodiesterase inactivates cAMP, turning off cell’s response until a new hormone molecule binds.
[18.4] What are the factors affecting the responsiveness of a target cell?
- Hormones concentration
- Abundance of hormone receptors
- Influence from other hormones.
[18.4] What is the permissive effect?
An effect produced by a hormone allowing another, primary hormone to have an effect.
[18.4] What is a synergistic effect as it relates to hormones?
When two hormones act together produce a response greater than the sum of their individual effect.
[18.4] What is an antagonistic effect as it relates to hormones?
When a hormone’s effect opposes the effects of another hormone.
[18.5] List the ways hormone secretion is regulated.
- Signals from nervous system
- Chemical changes in blood
- Other hormones
[18.6] What is the pituitary gland?
A pea-shaped structure on the (hypophyseal fossa of the sella turcica of the) sphenoid bone, attached to the hypothalamus, and releases hormones controlling other endocrine glands.
[18.6] What is the infundibulum?
The stalk attaching the pituitary gland to the hypothalamus.
[18.6] What are the two portions of the pituitary?
The anterior pituitary lobe and the posterior pituitary lobe.
[18.6] What are the two parts of the anterior pituitary lobe?
The pars distalis and pars tuberalis.
[18.6] What are the two parts of the posterior pituitary lobe?
The pars nervosa, and the pars intermedia.
[18.6] What are the types of anterior pituitary cells?
Somatotrophs, thyrotrophs, gonadotrophs, lactotrophs, and corticotrophs.
[18.6] Describe somatotrophs.
Cells secreting growth hormone.
[18.6] What is the function of growth hormone?
Stimulates general body growth and regulates aspects of metabolism.
[18.6] Describe thyrotrophs.
Pituitary cells secreting thyroid-stimulating hormone (TSH)
[18.6] What is the function of thyroid-stimulating hormone?
Controls secretions and other activities of thyroid gland.
[18.6] Describe gonadotrophs.
Pituitary cells secreting follicle-stimulating hormone and luteinizing hormone.
[18.6] What is the function of follicle-stimulating hormone and luteinizing hormone?
In men, stimulate production of sperm and secretion of testosterone.
In women, stimulate maturation of oocytes and secretion of estogen and progesterone.
[18.6] Describe lactotrophs.
Pituitary cells secreting prolactin.
[18.6] What is the function of prolactin?
Initiation of milk production in mammary glands after the glands are primed by other hormones.
[18.6] Describe corticotrophs.
Pituitary cells secreting adrenocorticotropic hormone and melanocyte-stimulating hormone.
[18.6] What is the function of adrenocorticotropic hormone?
Stimulate the adrenal cortex to secrete glucocorticoids.
[18.6] How does the hypothalamus control the anterior pituitary?
By secreting releasing hormones.
[18.6] What are the hormones released by the hypothalamus to control the anterior pituitary?
- Growth hormone releasing hormone.
- Thyrotropin releasing hormone
- Corticotropin releasing hormone
- Prolactin releasing hormone
- Gonadotropin releasing hormone
[18.6] What are the inhibitng hormones released by the hypothalamus?
- Growth hormone inhibiting hormone.
- prolactin inhibiting hormone
[18.6] What is the hypophyseal portal system?
A blood flow system from capillaries in the hypothalamus into veins carrying blood to the capillaries of the anterior pituitary.
[18.6] List the steps of the regulation of anterior pituitary secretion.
- Neurosecretory cells synthesize hypothalamic hormones and store in axon terminals.
- When excited, these neurosecretory cells release vesicles containing the hormones into the blood of the hypophyseal portal system.
- The hormones are transported to and stimulate the anterior pituitary to release the hormones of the anterior pituitary.
- Hormones of the anterior pituitary are released into the blood stream.
[18.6] What are tropic hormones?
Hormones acting on other endocrine glands.