Endocrinology Flashcards
What are the 4 principal mechanisms of communication between cells?
– Gap junctions
* Pores in cell membrane allow signaling molecules, nutrients,
and electrolytes to move from cell to cell
– Neurotransmitters
* Released from neurons to travel across synaptic cleft to
second cell
– Paracrines
* Secreted into tissue fluids to affect nearby cells
– Hormones
* Chemical messengers that travel in the bloodstream to other
tissues and organs
What is the endocrine system?
glands,tissues, and cells that secrete
hormones
What are endocrine glands?
organs that are traditional sources of
hormones
What are hormones?
chemical messengers that are transported
by the bloodstream and stimulate
physiological responses in cells of
another tissue or organ, often a
considerable distance away
What are the features of exocrine glands?
– Have ducts; carry secretion to an epithelial surface or the mucosa
of the digestive tract: “external secretions”
– Extracellular effects (food digestion)
What are the features of endocrine glands?
– No ducts
– Contain dense, fenestrated capillary networks which allow easy
uptake of hormones into bloodstream
– “Internal secretions”
– Intracellular effects such as altering target cell metabolism
Compare the nervous and endocrine systems?
- Both systems serve for internal communication
- Speed and persistence of response
– Nervous: reacts quickly (ms timescale), stops quickly
– Endocrine: reacts slowly (seconds or days), effect may
continue for days or longer - Adaptation to long-term stimuli
– Nervous: response declines (adapts quickly)
– Endocrine: response persists (adapts slowly) - Area of effect
– Nervous: targeted and specific (one organ)
– Endocrine: general, widespread effects (many organs)
What is a target organ/cell?
those organs or cells
that have receptors for a hormone and can respond to it
– Some target cells possess enzymes that convert a
circulating hormone to its more active form
What are the 2 parts of the pituitary gland?
Adenohypophysis (anterior) and neurohypophysis (posterior)
How big is the anterior pituitary and how is it linked to the hypothalamus?
it is 3/4 of the pituitary and is linked by the hypophyseal portal system
What is the hypothalamus’s target?
pituitary
How many hormones does the hypothalamus secrete? Where do they go?
8; 6 go to anterior, 2 go to posterior. All release or inhibit
What are the hypothalamic hormones?
Gonadotropin-releasing hormone (GnRH), Thyrotropin-releasing hormone (TRH), Corticotropin Releasing hormone (CRH), Prolactin-inhibiting hormone (PIH), Growth hormone-releasing hormone (GHRH), and Somatostatin (GHIH)
What are the anterior pituitary hormones?
Follicle-stimulating hormone (FSH), Luteinizing hormone (LH), Thyroid-stimulating hormone (TSH), Adrenocorticotropic hormone (ACTH), Prolactin (PRL), Growth Hormone (GH)
What are the posterior pituitary hormones?
Oxytocin (OT) & Antidiuretic hormone (ADH)
How is the posterior pituitary connected to the hypothalamus?
Hypothalamo-hypophyseal tract
What produces OT and ADH?
Paraventricular nuclei- OT
Supraoptic nuclei - ADH
What do each of the anterior pituitary hormones do?
– Follicle-stimulating hormone (FSH)
* Stimulates secretion of ovarian sex hormones,
development of ovarian follicles, and sperm production
– Luteinizing hormone (LH)
* Stimulates ovulation, stimulates corpus luteum to secrete
progesterone, stimulates testes to secrete testosterone
* Thyroid-stimulating hormone (TSH)
– Stimulates secretion of thyroid hormone
* Adrenocorticotropic hormone (ACTH)
– Stimulates adrenal cortex to secrete glucocorticoids
* Prolactin (PRL)
– After birth, stimulates mammary glands to synthesize milk
* Growth hormone (GH)
– Stimulates mitosis and cellular differentiation
What does somatostatin do?
inhibit GH and TSH
What do the posterior pituitary hormones do?
- ADH (antidiuretic hormone)
– Increases water retention, thus reducing urine volume,
and preventing dehydration
– Also called vasopressin because it can cause
vasoconstriction - Oxytocin (OT)
– Surge of hormone released during sexual arousal and
orgasm
– Promotes feelings of sexual satisfaction and emotional
bonding between partners
– Stimulates labor contractions during childbirth
– Stimulates flow of milk during lactation
– May promote emotional bonding between lactating
mother and infant
How does negative feedback work for hormones?
increased target organ
hormone levels inhibit
release of hypothalamic
and/or pituitary hormones
– Example: thyroid hormone+
inhibits release of TRH by
hypothalamus and of TSH by
anterior pituitary
How does positive feedback work for hormones? Which hormone does this?
OT, – Stretching of uterus increases OT release, causes
contractions, causing more stretching of uterus, etc.
until delivery
– The suckling of an infant triggers nerve impulses from
the nipple to the hypothalamus that causes the
release of oxytocin by the posterior pituitary, which
stimulates the release of milk
What does GH do to the liver? Why?
– Insulin-like growth factors (IGF-I) or somatomedins
(IGF-II)
* Stimulate target cells in diverse tissues
* IGF-I prolongs the action of GH
Longer half-life
What does IGF-I do?
– Protein synthesis increases
– Lipid metabolism increases
– Carbohydrate metabolism
– Electrolyte balance
What is the pineal gland? What does it do?
Gland in the 3rd ventricle below corpus callosum, synthesizes melatonin
What does the thymus do? Where is it?
Mediastinum superior to heart, it matures T cells and secretes thymopoietin, thymosin, and thymulin
What does the thyroid gland secrete?
thyroxine or
tetraiodothyronine (T4 because of
four iodine atoms) and
triiodothyronine (T3) in response to
TSH
What is calcitonin secreted by? What does it do?
Parafollicular cells, treats hypercalcemia and stimulates osteoblast activity
What happens in an iodine deficiency?
goiter
What do the parathyroid glands do?
Posterior to thyroid, secrete parathyroid hormone (PTH), increases blood Ca 2+ levels
What are the adrenal glands? Where are they?
small glands retroperitoneal on top of kidneys
What is the function of the medulla of the adrenal gland? What is released here?
Endocrine gland and ganglion of sympathetic nervous system; epi, norepi, dopamine
What are the layers of the adrenal cortex? What do they do?
– Zona glomerulosa (thin, outer layer)
* Cells are arranged in rounded clusters
* Secretes mineralocorticoids—regulate the body’s
electrolyte balance
– Zona fasciculata (thick, middle layer)
* Cells arranged in fascicles separated by capillaries
* Secretes glucocorticoids and androgens
– Zona reticularis (narrow, inner layer)
* Cells in branching network
* Secretes glucocorticoids and sex steroids
What are mineralocorticoids and glucocorticoids?
– Steroid hormones that regulate electrolyte balance
– Regulate metabolism of glucose and other fuels
What is aldosterone?
Mineralcorticoid, – Aldosterone stimulates Na+ retention and K+ excretion
* Water is retained with sodium by osmosis, so blood
volume and blood pressure are maintained
* Part of the renin-angiotensin-aldosterone (RAA) system
What is cortisol?
Glucocorticoid, – Cortisol and corticosterone stimulate fat and
protein catabolism, gluconeogenesis (glucose
from amino acids and fatty acids) and release of
fatty acids and glucose into blood
What are the sex steroids?
– Androgens: set libido throughout life; large role in
prenatal male development (include DHEA,
dehydroepiandrosterone, which other tissues convert
to testosterone)
– Androgens also play a role in the formations of
characteristics of puberty (pubic hair, apocrine
glands)
– Estradiol: (adrenal estrogen) small quantity from
adrenals, but this becomes important after
menopause for sustaining adult bone mass
What does the pancreas have?
both exocrine and endocrine glands
What do the a cells in the pancreas secrete?
glucagon which raises blood sugar
What do the b cells in the pancreas secrete?
insulin, which lowers blood sugar
What are the exocrine and endocrine products of the gonads?
– Exocrine product: whole cells—eggs and sperm
(cytogenic glands)
– Endocrine product: gonadal hormones—mostly steroids
What are the different gonadal hormones?
- Ovarian hormones
– Estradiol, progesterone, and inhibin - Testicular hormones
– Testosterone, weaker androgens, estrogen, and inhibin
What is the function of inhibin?
Suppress FSH secretion
Where does inhibin come from in testes?
sustentacular cells w/ ABP
What causes diabetes insipidus?
Hyposecretion of ADH, causes polyuria
What is acromegaly?
hypersecretion of GH
What are hypoparathyroidism and hyperparathyroidism?
- Hypoparathyroidism
– Surgical excision during thyroid surgery
– Fatal tetany (spasms in larynx) in just a few days due
to rapid decline in blood calcium level - Hyperparathyroidism: excess PTH secretion
– Parathyroid tumor
– Bones become soft, fragile, and deformed
– Ca2+ and phosphate blood levels increase
– Promotes renal calculi formation
What is pathogenesis?
cells cannot absorb glucose,
must rely on fat and proteins for energy needs,
thus weight loss and weakness
What is the chronic pathology of diabetes?
– Leads to neuropathy and cardiovascular damage
from atherosclerosis and microvascular disease
* Arterial damage in retina and kidneys (common in
type 1), atherosclerosis leads to heart failure
(common in type 2)
* Diabetic neuropathy—nerve damage from
impoverished blood flow can lead to erectile
dysfunction, incontinence, poor wound healing, and
loss of sensation from area
