Endocrine System Flashcards
Endocrine gland
ductless organ that secretes hormones
hormone
chemical messages that travel through the blood to regulate target cells
target cell
have specific receptors to which the hormone binds, receptors may be intracellular or located on the plasma membrane
what changes can target cells trigger after hormone binding?
- alter plasma membrane permeability
- synthesis of proteins
- activate or inactivate enzymes
- stimulate cell division (mitosis)
Hypothalamus
secretes releasing hormones that control the activity of the anterior pituitary gland
Pituitary gland (hypophysis)
contains 2 functional lobes-anterior pituitary made of glandular tissue and the posterior pituitary made of nervous tissue
Posterior pituitary gland
made of nervous tissue, connected to hypothalamus by neural tissue
- Nuclei of the hypothalamus synthesize hormones that are transported to the posterior pituitary where they are stored and released
- Oxytocin-causes uterine contractions during childbirth and milk ejection reflex during nursing
- Antidiuretic hormone (ADH)-stimulates reabsorbtion of water in the kidneys leading to reduced urine volume
Anterior pituitary gland
made of glandular tissue, connected to hypothalamus by the hypophyseal portal system-capillary beds
*produces tropic hormones to stimulate growth of another gland and regulate the release of hormones from other endocrine glands
Thyroid stimulating hormone (TSH)
targets thyroid gland to produce hormones
*release stimulated by the hormone TRH from the hypothalamus
Adrenocorticotropic hormone (ACTH)
stimulates the adrenal cortex to release glucocorticoids
*release stimulated by CRH from the hypothalamus
Follicle stimulating hormone (FSH)
In females-stimulates egg maturation and estrogen production
In males-stimulates sperm development
*release stimulated by GnRH from the hypothalamus
Leutinizing hormone (LH)
In females-stimulates ovulation and progesterone production
In males-stimulates testes to produce testosterone
*Release stimulated by GnRH from the hypothalamus
Growth hormone (GH)
stimulates cell growth and division in skeletal muscle and bone, stimulates the liver to produce insulin-like growth factor (IGF)
*release stimulated by GHRH from the hypothalamus
Prolactin (PRL)
stimulates growth of the mammary gland and milk production
*release stimulated by estrogen from the ovaries
Thyroid gland
butterfly shaped gland located in the anterior cervical region
*produces T3, T4, and calcitonin
Thyroid hormones T3 and T4
increases cell metabolism, important in normal tissue growth
- produced by follicular cells
- Release stimulated by TSH from the anterior pituitary
Calcitonin
decreases blood calcium levels, stimulates osteoblasts, inhibits osteoclast
- produced by C cells of the thyroid gland (parafollicular cells)
- release stimulated by high calcium levels (hypercalcemia)
Parathyroid gland
tiny masses found on the posterior side of the thyroid
- parathyroid hormone (PTH) is secreted by chief cells (principal cells) in response to low blood calcium levels (hypocalcemia)
- stimulates osteoclasts to release calcium from bone, stimulates activation of vitamin D leading to increased absorption of Ca2+ in digestive tract, stimulates reabsorption of calcium in the kidneys
Adrenal glands
paired, pyramid-shaped organs atop the kidneys-structurally and functionally they are two glands in one (adrenal medulla and adrenal cortex)
Adrenal medulla
located in the center of adrenal glands, nervous tissue that acts as part of the sympathetic nervous system
- produces epinephrine (adrenaline) and norepinephrine
- release stimulated by preganglionic sympathetic fibers
Adrenal cortex
outer layer of adrenal gland, made of glandular tissue
- synthesizes and releases steroid hormones
- there are 3 zones- zona glomerulosa, zona fasciculata, and zona reticularis
Zona glomerulosa
superficial layer of adrenal cortex
*produces mineralocorticoids (chiefly aldosterone)-reabsorption of sodium, secretion of potassium
Zona fasciculata
middle layer of adrenal cortex
- produces glucocorticoids (chiefly cortisol)-long term stress response increases blood glucose levels by stimulating synthesis of glucose from protein, increase appetite, suppresses the immune system decreasing inflammation
- release stimulated by ACTH from the anterior pituitary
Zona reticularis
deepest layer of adrenal cortex
*produces gonadocorticoids including dehydroepiandosterone (DHEA) an adrogen (hormone that binds to the same receptor as testosterone) to stimulate maturation of hair follicles in women during puberty
Pancreas
located posterior to the stomach, functions as both an endocrine and exocrine gland
Acinar cells
Exocrine cells that produce digestive enzymes that are secreted into the duodenum
Endocrine cells of the pancreas
organized into the islets of Langerhans
alpha cells
endocrine cell that produces the hormone glucagon that triggers the breakdown of glycogen in the liver, thus increasing blood glucose levels
beta cells
endocrine cells that produce the hormone insulin that increases the uptake of glucose into the cells, thus decreasing blood glucose levels
*release stimulated by high blood glucose (hyperglycemia)
pineal gland
produces the hormone melatonin that regulates sleep and wake cycles
*release stimulated by the hypothalamus during dark hours
Thymus
located in upper thoracic cavity over the heart
*produces the hormone thymosin that regulates maturation of T-lymphocytes
Ovaries
produce steroid sex hormones
- estrogen-stimulates secondary sex characteristics at puberty, plays role in regulating ovarian and uterine cycles
- progesterone-works with estrogen to maintain uterine cycle
Testes
produces testosterone-stimulates spermatogenesis and secondary sex characteristics at puberty
