A&P Final Part 2 (Hormones) Flashcards
Exocrine glands
secrete products into ducts which empty into body cavities or body surface
sweat, oil, mucous, & digestive glands
endocrine glands
secrete products (hormones) into bloodstream pituitary, thyroid, parathyroid, adrenal, pineal other organs secrete hormones as a 2nd function hypothalamus, thymus, pancreas, ovaries, testes, kidneys, stomach, liver, small intestine, heart & placenta
Components of endocrine system
hormone, target cells, endocrine glands, and endocrine system
Hypothalamus
master gland that secretes regulatory hormones that control pituitary
ex: ADH and oxytocin (both stored and released by posterior pituitary)
Anatomy of pituitary gland
Pea-shaped gland found in sella turcica of sphenoid
Anterior lobe = 75%
adenohypophysis
Posterior lobe = 25%
Hypothalamus –> Pituitary Anterior Lobe
Releasing hormones and their effects Thyrotropin releasing hormone (TRH) Promotes secretion of TSH and PRL Corticotrophin releasing hormone (CRH) Promotes secretion of ACTH Gonadotrophin releasing hormone (GnRH) Promotes secretion of FSH and LH Growth hormone releasing hormong (GHRH) Promotes secretion of GH
Inhibiting hormones and their effects Prolactin inhibiting hormone (PIH) Inhibits secretion of prolactin Somatostatin Inhibits secretion of GH and TSH
Follicle Stimulating Hormone (FSH)
Releasing hormones from hypothalamus, released by anterior pituitary
initiates the formation of follicles within the ovary
stimulates follicle cells to secrete estrogen
stimulates sperm production in testes
Luteinizing Hormone (LH)
Releasing hormones from hypothalamus, anterior pituitary produces
in females, stimulates secretion of estrogen,
ovulation of oocyte,
formation of corpus luteum, and
secretion of progesterone
In males, stimulates interstitial cells to secrete testosterone
Thyroid stimulating hormone (TSH)
Anterior Pituitary –> thyroid
Hypothalamus regulates these cells
Released from anterior pituitary (thyrotroph cells produce TSH)
Stimulates synthesis and secretion of T3/T4 (thyroid hormones)
without this hormone, thyroid is inactive
Adrenocorticotrophic Hormone (ACTH)
Regulates stress response
Hypothalamus releasing hormones (CRH)
Anterior pituitary secretes this
Hormone stimulates cells of adrenal cortex that produce glucocorticoids
Prolactin (PRL)
Hypothalamus regulates lactotroph cells (PIH)
which produce hormone under right conditions,
–> causes milk production
Suckling reduces levels of hypothalamic inhibition, hormone levels rise along with milk production
Growth Hormone (GH)
Secreted by anterior pituitary in response to GHRH from hypothalamus
Promotes tissue growth
directly affects mitosis and cellular differentiation
indirectly stimulates liver to produce IGF (insulin like growth factors) –>
IGF increases uptake of amino acids and incorporation into new proteins in skeletal muscle and lasts longer than GH
Functions of GH
Stimulates stem cell divisions and differentiation of daughter cells
Growth Hormone and Aging
increases through childhood and adolescence, causing bone, cartilage, and muscle growth
when you old, GH declines
GH levels:
higher during first 2 hours of deep sleep, after high protein meals, vigorous exercise, stress, and trauma
Melanocyte-stimulating hormone
Secreted by pars intermedia (boundary between anterior and posterior pituitary)
MSH influences pigmentation of skin, hair, and feathers in animals (and human fetus)
Stimulates melanocytes to produce melanin
In adult humans circulating blood does not contain MSH
Produced locally in sun exposed skin
Posterior Pituitary
Does not synthesize hormones
Stores and releases
Antidiuretic hormone
Oxytocin
Released into blood at the posterior pituitary
Oxytocin
Neuroendocrine reflex caused in two target tissues
During delivery
baby’s head stretches cervix
hormone release enhances
uterine muscle contraction
baby & placenta are delivered
After delivery
suckling & hearing baby’s cry stimulates milk ejection
hormone causes muscle contraction & milk ejection
Males and females – emotional bonding, empathy, maternal behavior
Antidiuretic Hormone (ADH)
Functions
decrease urine production
decrease sweating
increase BP
Causes vasoconstriction but only in extremely high concentrations
Alc inhibits ADH –> that’s why it’s dehydrating
Pineal Gland
Function is not well understood
Peak secretion and size in 1-5 yr. olds, by puberty 75% less
Involution (shrinkage) occurs after age 7
Produces serotonin by day, converts it to melatonin at night
May regulate timing of puberty in humans and set circadian rhythms
Melatonin increases in SAD (seasonal affective disorder) + PMS, decreases with phototherapy
Effect of light on pineal gland
melatonin secretion decreases with light exposure because sympathetic ganglion is excited
SAD
you’re sad during winter because too much melanin –> it’s too dark
Thymus
Location: mediastinum, superior to heart
Involution after puberty
Secretes hormones that regulate development and later activation of T-lymphocytes
Thyroid Gland Anatomy
Largest endocrine gland with high rate of blood flow
Anterior and lateral sides of trachea
2 large lobes connected by isthmus
Thyroid follicles
secretes 2 hormones, T3+T4
Thyroid hormone:
increases body’s metabolic rate and O2 consumption, causes
calorigenic effect (cells consume more energy increasing heat production),
increase heart rate and contraction strength, increase respiratory rate, and stimulates appetite and breakdown carbs, lipids & proteins
C Cells of thyroid
produces calcitonin that decreases blood calcium content, promotes ca2+ desposition –> bone formation (esp in kids)
Control of T3 and T4 secretion
Negative feedback
Low blood levels of hormones stimulate hypothalamus
It stimulates pituitary to release TSH
TSH stimulates gland to raise blood levels
(T4 gets converted to T3, both are responsible for metabolism but T3 is the more active of the two)
Parathyroid glands
4 pea-sized glands found on back of thyroid gland
Parathyroid hormone
Raises blood calcium levels increase activity of osteoclasts increases reabsorption of Ca+2 by kidney Reducing urinary losses Stimulates formation of calcitriol (vitamin D3) by kidney which increases absorption of Ca+2 by intestines Opposite function of calcitonin
Regulation of calcium blood levels
PTH (with calcitriol) and Calcitonin
PTH increases calcium blood level
Calcitronin (decreases calcium in blood –> calcium IN bone)
Hypocalcemia
deficiency of blood calcium
causes excessive excitability of nervous system leading to muscle spasms or tremors
calcium normally binds to cell surface contributing to resting membrane potential
with less calcium, sodium channels open more easily exciting neuron
can cause carpopedal spasm in hands and feet
Anatomy of Adrenal Glands
One on top of each kidney
Cortex produces 3 different types of hormones from 3 zones of cortex
(Adrenal) Medulla produces epinephrine & norepinephrine
Adrenal Medulla
innervated by sympathetic neurons
Chromaffin cells = modified neurons –secretory cells that release into blood stream
Situations of fear, pain, stress stimulate nerve fibers that cause chromaffin cells to release norepinephrine or epinephrine (small amounts of dopamine)
increases BP and heart rate
increases blood flow to skeletal muscle
increases pulmonary air flow
inhibits digestion and urination
Adrenal cortex
Produces 25 steroid hormones (corticosteroids)
3 categories
Mineralcorticoids - regulate electrolytes
Glucocorticoids - regulate metabolism of glucose
Sex steroids - reproductive functions (androgens)
Adrenal Cortex - Zona glomerulosa
Aldosterone- principle mineralocorticoid produced
Secreted in response to
drop in blood Na+ content
in response to Angiotensin II from the lungs
Functions
increase reabsorption of Na+ (and water) in kidneys
Maintains blood volume
Zona Fasciculata + Reticularis Glucocorticoids
Primarily secretes cortisol in response to ACTH from anterior pituitary
Functions = help regulate metabolism
Stimulates fat and protein catabolism
Stimulate release of fatty acids and glucose into the blood —provide resistance to stress by making nutrients available for ATP production
Anti-inflammatory effects (steroid creams)
Inhibit white blood cells
reduce release of histamine from mast cells
decrease capillary permeability
Androgens from Zona Fasciculata and Reticularis
Small amounts of androgens produced
Major androgen = dehydroepiandrosterone which gets converted to testosterone
Androgens are produced in large quantities in the testes of males
Thus the small amount produced in the adrenal glands are insignificant in males
Important in females (sex drive)
Estradiol = an adrenal estrogen
Minor importance in reproductive women (since ovaries produce much more)
Important after menopause = Helps to sustain bone mass
Pancreatic Hormones
1-2 Million pancreatic islets producing hormones
Clusters of endocrine cells
The other 98% of organ produces digestive enzymes (exocrine)
Pancreatic Islets
Types of cells: Alpha, Beta, Delta, PP (F), G
Alpha Cells
Glucagon raises blood glucose levels by increasing rates of: glycogen breakdown in skeletal muscle glucose release by the liver fat breakdown in adipose
Beta Cells
Insulin secreted after meal with carbohydrates raises glucose blood levels
stimulates glucose and amino acid uptake
nutrient storage effect (stimulates glycogen, fat and protein synthesis)
Stimulation of fatty acid absorption in adipocytes
Delta Cells
makes somatostatin
Inhibiting hormone (GHIH)
Secreted concurrently with insulin
May modulate secretion of alpha and beta cells
G Cells
secrete gastrin (stomach secretions, motility, and emptying)
PP (F) Cells
produce pancreatic polypeptide (PP)
inhibits gallbladder contractions and regulate production of some pancreatic enzymes
