Endocrine Flashcards
What are the main functions of the pineal gland?
Regulates circadian rhythms; obtains info about light and dark cycles
What does the pineal gland secrete & what does this hormone do?
Melatonin- Release is stimulated by sympathetic neurons at night
Melatonin regulates daily body rhythms; involved in seasonal affective disorder
What is the functional unit of the thyroid?
Thyroid follicle
A thyroid follicle is_____
a mass of colloid surrounded by follicular cells
What do thyroid follicular cells produce?
Thyroid hormones T3 and T4
What is the main function of T3 and T4?
REGULATE BASAL METABOLISM!!!
What is the best combination of coffee flavors?
Raspberry and French Vanilla
Cinnamon = fail
How are thyroid hormones regulated?
Negative feedback: When T3 and T4 levels reach a certain threshold, TRH-secreting neurons in the hypothalamus are inhibited
What is Graves’ disease?
Hyperthyroidism: Excessive thyroid hormones in circulation; caused by antibodies overstimulating thyroid follicular cells (autoimmune)
What produces calcitonin and what does it do?
Made by parafollicular cells; lowers blood calcium
What is the parathyroid gland?
Small endocrine gland associated with thyroid gland; Humans have 4 of them
What is the function of the principal (aka chief) cells of the parathyroid?
Secrete PTH; PTH regulates calcium and phosphate levels in blood; causes increase in blood Ca2+ levels
What are the 3 cells found in the Islets of Langerhans?
A cells: secrete glucagon
B cells: secrete insulin
D cells: secrete somatostatin
What is the function of the 3 hormones secreted by the Islets of Langerhans?
Insulin: Uptake and storage of glucose; stimulates pancreas exocrine secretion
Glucagon: Breakdown of glycogen and release of glucose; inhibits pancreas exocrine secretion
Somatostatin: Unclear, but it does inhibit both glucose and insulin secretion
What are the three zones of the adrenal cortex?
Know these for practical
(from inside to out)
Zona Glomerulosa
Zona Fasciculata
Zona Reticularis
Describe the blood supply to the medulla of the adrenal gland
It has Dual Blood Supply: Arterial blood from medullary arterioles and venous blood from cortical sinusoidal capillaries
What does the cortex of the adrenal gland secrete?
Steroid hormones
What does the zona glomerulosa secrete?
Mineralocorticoids (Ex. aldosterone); Regulates Na and K balance and H2O homeostasis
What does the zona fasciculata secrete?
Glucocorticoids (Ex. cortisol); Regulate glucose synthesis and glycogen formation, Depress immune function and inflammation
What does the zona reticularis secrete?
Weak androgens and small amount of glucocorticoids
What are the main cells of the adrenal medulla?
Chromaffin cells
What do chromaffin cells secrete?
Catecholamines; Dense core vesicles secrete norepinephrine & smaller clear vesicles secrete epinephrine
Responsible for “adrenal rush”
Practice questions from Herron
1) Which of the following is produced by the pineal gland? Melatonin
2) What are the characteristics of someone with Graves Disease? High levels of T3 and T4
Paracrine vs. endocrine hormones?
Paracrine hormones have more local effects, and are secreted to interstitial tissues rather than into the bloodstream like endocrine hormones are
What types of molecules are hormones?
- Steroids (like gonadal, adrenocortical)
- Small peptides, proteins, glycoproteins
- Amino acid derivatives (catecholamines), iodinated aa’s (thyroid hormones), and derivatives like PGs
Alternate names for anterior and posterior pituitary?
Anterior - adenohypophysis
Posterior - neurohypophysis
What are the pituitary lobes derived from?
Anterior - from neuroectoderm
Posterior - from ectoderm (Rafke’s pouch in the mouth)
Components of the neurohypophysis?
Infundibulum, Pars nervosa
Components of the adenohypophysis?
Pars distalis
Pars intermedia
Pars tuberalis
What nuclei signal the posterior pituitary and what hormones are they responsible for?
paraventricular nucleus (ADH) supraoptic nucleus (oxytocin)
Where are pituicytes found?
They make up the majority of the pars nervosa (rest are astrocytes)
Function of the pars tuberalis?
Immunoreactive to ACTH, FSH, LH
What cells are found in the pars distalis?
- acidophils - somatotropes, lactotropes (not endocrine!)
- basophils - gonadotropes, thyrotropes, corticotropes
- chromophobes
What cells are found in the pars intermedia?
Colloid follicles, basophils, chromophils
Function of oxytocin?
Regulates smooth muscle contraction during pregnancy in the uterus and myoepithelial cells in the mammary gland
Function of ADH/vasopressin?
Control of water retention by the kidneys. Inadequacy results in diabetes insipidus
Where are Herring bodies found?
Near the axonal terminals of neurosecretory cells from PVN and SON
Function of basophils?
trophic hormones that regulate the activity of other endocrine glands
Function of acidophils?
growth hormones that act directly on target hormones (not endocrine in nature)
Describe the releasing hormones of the hypothalamus
They are stimulatory hormones released in spurts that go via the hypothalamic-pituitary portal vein to the basophils and acidophils of the anterior pituitary
What are the 2 inhibitory releasing hormones?
dopamine and somatostatin
