Endocrine System Flashcards
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)?
- Adrenal cortex
- 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?
-Transcortins
What are the 3 major classes of corticosteroids?
- Glucocorticoids
- Mineralocorticoids
- Cortical sex hormones
Glucocorticoids include…
- Cortisol/Cortisone
- Raise blood glucose levels (protein breakdown/ gluconeogenesis/ lower protein syn)
- Increase plasma glucose levels
- Release amino acids (skeletal muscle) and lipids (adipose)
- Anti-inflammatory
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?
- Angiotensin II
- ANP
Where are most androgens produced in men?
-Testes
What produces catecholamines?
- Adrenal medulla
- 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?
-Infundibulum
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)
- Prolactin
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…
- TH low
- Slow HR/breathing, fatigue, cold, weight gain
- Cretinism (young) retardation/short
Hyperthyroidism is characterized by…
- Overstimulated thyroid
- 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?
- Melatonin
- May help regulate circadian rhythms
- Antagonist to MSH in primitive vertebrates
Which type of hormone is first messenger?
- Peptide hormones
- 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
-What are some of the releasing hormones of the hypothalamus?
-GnRH, GHRH, CRF, Somatostatin (inhibits GH), dopamine (inhibits prolactin)
