38. Endocrine System Flashcards
What is the endocrine system?
Internal regulatory system
Maintains internal environment of body
Organs are endocrine glands (spread throughout body and secrete hormones into bloodstream to target cells/tissues)
Similar to nervous system but acts more slowly and affects many body tissues
What stimulates hormone secretion
Ion or nutrient concentrations in blood
Neuronal control
In response to other hormones
Types of feedback loops
Negative: effect of hormone halts more secretion of hormone, maintains hormone within certain range
Positive: effect of hormone increases more secretion of hormone
Types of endocrine glands
Hypothalamus
Pituitary gland
Thyroid gland
Parathyroid glands
Adrenal glands
Pancreas
Gonads (ovary or testis)
Difference between exocrine and endocrine glands
Exocrine glands: synthesize substances released through ducts
Endocrine glands: synthesize substances (hormones) released into bloodstream to reach target tissue to signal physiological response
Characteristics of the Pituitary gland
Located underneath brain, suspended from hypothalamus by infundibulum
Divided structurally and functionally into anterior and posterior parts
Characteristics of anterior pituitary and types of hormones secreted
Controlled by hormones secreted by hypothalamus into bloodstream
Secretes: thyroid-stimulating hormone, FSH & LH, adrenocorticotropic hormone, prolactin, melanocyte-stimulating hormone, and growth hormone
Function or thyroid stimulating hormone (TSH)
Stimulates thyroid gland to release thyroid hormone
Control metabolism
Function of FSH and LH
Acts on gonads to stimulate sperm and oocyte production and release of sex hormones
Function of adrenocorticotropic hormone
Acts on adrenal cortex to cause released of corticosteroids
Function of prolactin
Acts on mammary glands of breast for growth and milk production
Function of melanocytes stimulating hormone
Acts on melanocytes in skin to produce melanin
Function of growth hormone
Acts on all body tissues (especially muscles and bones) to stimulate growth of body
Characteristics and hormones secreted by posterior pituitary gland
Structurally part of brain.
Special neurons from hypothalamus extend into posterior pituitary
Hormones stored and released are antidiuretic hormone and oxytocin
Function of anti diuretic hormone
Stimulates kidneys to resorb more water when dehydrated, helps body retain water
Also tells blood vessels to constrict when blood pressure is low to return it to normal
Function of oxytocin
Stimulates ejection of milk from breast during breastfeeding
Induces contraction of smooth muscles in reproductive organs
Characteristics of thyroid gland
Largest endocrine gland
Located in lower neck anterior to trachea
Right and left lobes connected by isthmus
Follicular cells in thyroid produce thyroid hormone (increases basic metabolic rate and release stimulated by TSH from anterior pituitary)
Iodine is essential nutrient for thyroid hormone production
What is hyperthyroidism
Over-active thyroid gland
Many disorders can result in hyperthyroidism, most common is Graves’ disease
Autoimmune disease where antibodies stimulate thyroid hormone secretion
Most common in middle aged women
Symptoms are elevated metabolic rate, rapid heart rate, weight loss, and protruding eyes from edema
What is goiter
Insufficient secretion of thyroid hormone is hypothyroidism
Can be due to lack of iodine in diet
Thyroid gland produces precursor to TH
Thyroid gland enlarges as pituitary continues to release TSH and precursor is produced
Enlargement of thyroid gland is a goiter
Iodized salt has greatly reduced incidence of goiters
Characteristics of parathyroid glands
4 glands located on posterior of thyroid gland
Produce parathyroid hormone (PTH) to regulate calcium levels in blood
Not under control of hypothalamus
PTH released into blood when calcium levels are low and cause osteoclasts to release calcium from bone, decrease excretion of calcium by kidney, and cause small intestines to absorb more calcium
Characteristics of adrenal glands
Located superior to kidneys
2 endocrine glands in 1: cortex and medulla
Different hormones, but both help to cope with stress and extreme situations
Characteristics of adrenal medulla
Acts as part of sympathetic nervous system
Chromaffin cells are modified postsynaptic sympathetic neurons
Release epinephrine and norepinephrine into bloodstream
Responsible for short term stress response
Characteristics of adrenal cortex
Produces and releases corticosteroids
Stimulates by adrenocorticotropic hormone from anterior pituitary
Responsible for long-term stress response
Has 3 layers:
Zona glomerulosa- outer, produce aldosterone
Zona fasciculata- middle, produce cortisol
Zona reticularis- inner, produce androgens
Function of aldosterone
Stimulate resorption of sodium and water by kidneys to increase blood volume and pressure
Function of cortisol
Increase glucose levels in blood, breakdown protein and fats for enefgy
Function of androgens
Not fully understood, thought to boost immunity
Characteristics of pancreas
Located behind stomach, within C-shape of duodenum
Exocrine function: apical cells that secrete digestive enzymes into duodenum via pancreatic duct
Endocrine function: islets of Langerhans consists of alpha and beta cells to produce glucagon and insulin respectively
What is diabetes mellitus
Metabolic condition marked by inadequate uptake of glucose from blood by tissues
Results in high amounts of glucose in urine
Chronically elevated blood glucose damages small arterioles, kidney failure, and amputation
Type 1 or 2
Characteristics of type 1 diabetes
Occurs in children
Diminished or absent production of insulin by beta cells
Auto immune response destroys beta cells
Glucose cannot be delivered to tissues
Requires insulin injections
Characteristics of type 2 diabetes
90% of diabetes cases
Usually occurs in adults
Associated with obesity
Decreased insulin release from beta cells or diminished effectiveness of insulin
Requires dietary changes, exercise, medication
Characteristics of testes
Interstitial (Leydig) cells produce testosterone
Maintain male reproductive organs and secondary sex characteristics
Promote formation of sperm
Characteristics of ovaries
Granulosa cells produce estrogen - maintain female reproductive organs and secondary sex characteristics
Corpus luteum produces progesterone - prepares endometrium for implantation
