Flashcards in Endocrine System Deck (43):
Where do endocrine glands secrete hormones to?
-Directly into circulatory system
Where do exocrine glands substances go?
-Transport by ducts
What determines the specificty of hormonal action?
-Specific receptors on/in target cells
What secretes adrenocortical steroids (corticosteroids)?
-Stimulated by ACTH produced by anterior pituitary
How do corticosteroids function?
-Determine which genes of target cell are transcribed and at what rate
How are corticosteroids transported in bloodstream?
What are the 3 major classes of corticosteroids?
-Cortical sex hormones
-Raise blood glucose levels (protein breakdown/ gluconeogenesis/ lower protein syn)
-Increase plasma glucose levels
-Release amino acids (skeletal muscle) and lipids (adipose)
What is an example of mineralocorticoids?
-Aldosterone - regulates plasma Na+/K+ levels
-Active reabsorption of Na+/passive reabsorption of H2O
-Increase blood volume/pressure
What stimulates mineralocorticoids? Inhibits?
Where are most androgens produced in men?
What produces catecholamines?
-E.g. Neurotransmitters: Epinephrine and Norepinephrine
What are the effects of epinephrine?
-Increase glycogen --> glucose (liver/muscle)
-Increase basal metabolic rate
-Dilate/constrict blood vessel (>blood flow to skeletal muscle/heart/brain)
-Release lipids by adipose
What connects the pituitary gland to hypothalamus?
What regulates anterior pituitary gland secretions?
-Releasing hormones from hypothalamus
What type of hormones does the anterior pituitary secrete?
-Direct and tropic hormones
What are the direct hormones of the anterior pituitary?
-Growth Hormone (GH, somatotropin)
What is acromegaly?
-Overproduction of GH in adults
What are the tropic hormones of the anterior pituitary?
-Adrenocorticotropic hormone (ACTH)
-Thyroid-Stimulating Hormone (TSH)
-Luteinizing hormone (LH) - ovulation/corpus luteum or testes to produce testosterone
-Follicle-Stimulating Hormone (FSH) -maturation of ovarian follicles/seminiferous tubules and sperm production
-Melanocyte-stimulating Hormone (MSH) - darken frog
-Endorphins - Neurotransmitters
What is the role of the posterior pituitary?
-Store/release peptide hormones, oxytocin and ADH
When is ADH released?
-Plasma osmolarity increases (sense by osmoreceptors in hypothalamus)
-Blood volume decreases (sense by baroreceptors in circulatory system)
What do the neurosecretory cells of the hypothalamus regulate? How?
-Pituitary gland secretions by negative feedback
-Use of Inhibiting/releasing hormones
What does GnRH do?
-Stimulate anterior pituitary to secrete FSH/LH
How do releasing hormones function?
-Secreted into hypothalamic-hypophyseal portal system
-Blood from capillary bed in hypothalamus --> portal vein --> anterior pituitary --> secondary capillary network
Neurosecretory cells in hypothalamus synthesize...
...oxytocin and ADH
How do hormones of hypothalamus reach posterior pituitary?
-Via hypothalmus axons
What are the thyroid hormones?
-Thyroxine (T4) and triiodothyronine (T3)
-Formed from glycoprotein thyroglobulin
Which thyroid hormone is more potent?
T3 (only 30% produced by thyroid vs 100% of T4)
How are T3 and T4 transported?
-Bound to plasma proteins
Hypothyroidism is characterized by...
-Slow HR/breathing, fatigue, cold, weight gain
-Cretinism (young) retardation/short
Hyperthyroidism is characterized by...
-High metabolic rate, warmth, sweating, palpitations, weight loss, protruding eyes
What is the role of calcitonin?
-Decrease plasma Ca++ by inhibiting release from bone
-Antagonistic to parathyroid hormone
Why is the pancreas both endocrine and exocrine organ?
-Secreted digestive enzymes (exocrine)
-Islets of Langerhans (endocrine)
What do alpha cells produce/secrete?
-Glucagon - protein/fat degradation, glycogen --> glucose, gluconeogenesis
-Increase blood glucose levels
-Antagonistic to insulin
What do beta cells produce/secrete?
-Insulin - uptake glucose by muscle/adipose, store glucose as glycogen, synthesize fats from glucose, uptake aa
What does parathyroid hormone do?
-Regulate plasma Ca++ by increasing release from bone, decrease excretion by kidneys
-Ca++ in bone bound to phosphorus so breakdown also increases phosphorus
-Increase excretion of phosphorus in kidneys
What does renin do?
-Produced by kidneys
-Enzyme converts plasma protein angiotensinogen to angiotensin I which is converted to angiotensin II stimulates secretion of aldosterone
What does EPO stimulate?
-Produced by kidneys
-Stimulates RBC production
What does the pineal gland secrete?
-May help regulate circadian rhythms
-Antagonist to MSH in primitive vertebrates
Which type of hormone is first messenger?
-Bind to specific receptors on surgace og target and trigger rxns
Where are steroid hormones produced?
-Testes, ovaries, placenta, adrenal cortex
Which hormones can cross the phospholipid bilayer?
-Steroid --> enter and target cells directly to bind receptor proteins in cytoplasm
-Directly activates expression of certain genes