Endocrine System Flashcards
Endocrine: derived from the Greek words ______ meaning _____ and _______ meaning _______.
“endo”; within
“krino”; to secrete
Composed of endocrine glands and specialized endocrine cells located throughout the body
Endocrine System
secrete chemical messengers called “hormones” into the bloodstream in order to produce a specific response to target tissues or effectors.
Endocrine glands
The 10 main regulatory functions of the endocrine system
- Metabolism
- Control of food intake and digestion
- Tissue Development
- Ion Regulation
- Water Balance
- Heart rate and blood pressure regulation
- Control of blood glucose and other nutrients
- Control of reproductive functions
- Uterine contractions and milk release
- Immune system regulation
- Endocrine chemical messengers
- derived from the Greek word “hormon” which means to set in motion
Hormones
two chemical categories of hormones
lipid-soluble and water-soluble
- Non-polar
- Small size and low solubility in aqueous fluids.
- Needs a binding protein for transport
- Diffuses across the cell membrane
- Receptor Location: Nucleus or cytoplasm
Lipid-soluble hormones
Examples of Lipid-soluble hormones
Steroid and thyroid hormones, and fatty acid derivative hormones
- polar
- Vary from small to large and soluble in blood
- Large hormones dissolve directly into the blood and are delivered to the target tissue without attaching to binding protein.
- Small hormones however need attachment to larger protein to avoid being filtered out of the blood.
- Cannot diffuse through cell membrane
- Receptor Location: Plasma membrane’s outer surface
Water-soluble hormones
Examples of water-soluble hormones
Protein and peptide hormones; amino-acid derivative hormones
The life span of __________ ranges from a few weeks to days, while _______ have relatively short half-lives because they are rapidly broken down by enzymes within the bloodstream.
lipid-soluble hormones; water-soluble hormones
three types of stimuli which regulate hormone release
- Humoral
- Neural
- Hormonal
Blood-borne chemicals which stimulate release of some hormones
Humoral stimuli
Control of Hormone Section in Humoral stimuli
When blood levels of certain substances changes, glands release hormones to maintain normal concentration of substances
Example of Control of Hormone Section in Humoral stimuli
When blood glucose level is elevated, there is a stimulation of release of insulin secreted by the pancreas to normalize blood glucose level
Inhibition of Hormone Release in humoral stimuli
A companion hormone exists to oppose those of the secreted hormone and its actions
Example of inhibition of Hormone Release in humoral stimuli
To raise blood pressure, the adrenal cortex secretes the hormone aldosterone in response to low blood pressure. However, if blood pressure rises, the atria of the heart releases the hormone atrial natriuretic peptide (ANP), which lowers blood pressure.
Control of Hormone Section in Neural stimuli
Following an action potential, neurons release a neurotransmitter into the synapse. Neurotransmitters will allow stimulation of the gland to release hormone where it will travel to its target
Example of Control of Hormone Section in Neural stimuli
Release of epinephrine and norepinephrine during stressful situations
Inhibition of Hormone release in neural stimuli
Neurons inhibit targets just as often as they stimulate targets.
- if the neurotransmitter is inhibitory, the target endocrine gland does not secrete its hormone.
Control of Hormone Section of Hormonal stimuli
It occurs when a secreted hormone stimulates the secretion of other hormones. These hormones are called tropic hormones
Example of control hormone section of hormonal stimuli
The hypothalamus secretes releasing hormones. These releasing hormones stimulate the release of hormone (tropic hormone) from the anterior pituitary. The tropic hormone travels to the target endocrine cell and stimulates the release of another hormone.
Inhibition of hormone release in hormonal stimuli
“inhibiting hormones” prevent the secretion of other hormones
Example of inhibition of hormone release in hormonal stimuli
Inhibiting hormones from the hypothalamus prevent thyroid hormones from the pituitary gland from secreting
Hormone release caused by a neural input
Neural stimuli
Hormone release caused by another hormone (a trophic hormone)
Hormonal stimuli
The endocrine system consists of ______, some of which are not limited to perform function to hormone secretion.
ductless glands
endocrine glands and organs:
- Pituitary gland
- Thyroid gland
- Parathyroid gland
- Adrenal glands
- Pancreas
- Testes and Ovaries
- Thymus
- Pineal Gland
- also called the hypophysis
- small gland about the size of a pea
- rests in a depression of the sphenoid bone inferior to the hypothalamus of the brain.
- secretes hormones that influence growth, kidney function, birth, and milk production by the mammary glands
- was known as the body’s master gland
pituitary gland
Two ways the hypothalamus controls the pituitary gland
- Hormonal control
- Direct innervation
- Synthesizes hormones, whose secretion is under the control of the hypothalamus
- made up of epithelial cells derived from the embryonic oral cavity
- hormones secreted are proteins, are transported in blood, have short life span, and bind to membrane-bound receptors
-most of its hormones are tropic hormones
Anterior pituitary gland
- Storage location for two hormone synthesized by special neurons in the hypothalamus
- its secretion of hormones is regulated by neural input
Posterior pituitary gland
- made up of two lobes connected by a narrow band called “isthmus.”
- One of the largest endocrine glands.
- Appears more red than surrounding tissues because it is highly vascular.
- surrounded by a connective tissue capsule
- Main function: Secretion of thyroid hormones
Thyroid gland
The three hormones that is synthesized and secreted by thyroid gland
- Triiodothyronine (T3)
- Thyroxine (tetraiodothyronine; T4)
- Calcitonin
- where thyroid hormones are synthesized and stored
- contain protein called “thyroglobulin” in which hormones are attached.
Thyroid follicles
- Thyroid hormones have a __________ effect on the hypothalamus and pituitary gland.
- Loss of negative feedback will result in ________. It causes enlargement of the thyroid. This condition is called ________.
- When the normal rate of thyroid hormone secretion is _________, growth and development cannot proceed normally.
negative feedback;
excess TSH;
goiter;
disrupted;
- lack of thyroid hormones
- In infants, it can result in cretinism.
- In adults, it can result to decreased metabolic rate, sluggishness, reduced ability to perform routine tasks and myxedema.
Hypothyroidism
elevated rate of thyroid hormones
Hyperthyroidism
a type of of hyperthyroidism that results when the immune system produces abnormal proteins that are similar in structure and function to TSH.
Grave’s disease
- Four tiny glands embedded in the posterior wall of the thyroid gland.
- These glands secrete the parathyroid hormone (PTH) which is essential in regulation of calcium level.
Parathyroid glands
Is released when there is a decrease in blood calcium
Parathyroid hormone (PTH)
1.______ increases active _________ formation through the effects of membrane-bound receptors of renal tubule cells in the kidney. Vitamin D stimulates increased _______ absorption by intestinal epithelial cells.
- PTH secretion increases blood calcium levels. PTH binds to receptors on ________. In turn, osteoblasts secrete substances that stimulate _______ to reabsorb bone.
- PTH _________ loss of calcium in the ________.
PTH
Vitamin D
calcium
osteoblasts
osteoclasts
Decreases
Urine
- low rate of PTH
- Results from injury to or the surgical removal of thyroid and parathyroid
Hypoparathyroidism
- elevated rate of PTH
- Causes softening, deformity and/or fracture of the bone.
Hyperparathyroidism
- Hormone of the posterior pituitary
- Also called vasopressin
- binds to membrane-bound receptors and increases water reabsorption by kidney tubules, resulting in less water lost as urine
- cause blood vessels to constrict when released in large amounts
Antidiuretic hormone
Binds to membrane-bound receptors and causes contraction of the smooth muscle cells of the uterus as well as milk letdown from breasts of lactating women
- its commercial preparations (Pitocin) are given to assist in childbirth and to constrict uterine blood vessels following childbirth
Oxytocin
Two small glands located superior to each kidney.
Adrenal glands
Each adrenal gland has an inner part called the _________ and the outer part called the __________
adrenal medulla;
adrenal cortex
- The principal hormone released is epinephrine.
- also releases small amounts of norepinephrine
- Related to fight or flight reaction, stress and low blood sugar.
Adrenal medulla
- Stress, physical activity, and low blood glucose levels act as _______ to the hypothalamus, resulting in increased _________ nervous activity
- An increased frequency of ________ conducted through the sympathetic division of the ______ nervous system stimulates the adrenal medulla to secretepinephrine and some norepinephrine into the circulatory system
- Epinephrine and norepinephrine act on their target tissues to produce _______
stimuli
Sympathetic
action potentials
autonomic
responses
- secretes three classes of steroid hormones:
1) mineralocorticoids 2)glucocorticoids 3)androgens - Have unique structural and functional characteristic
Adrenal cortex
regulates blood volume and levels of potassium and sodium ion
Mineralocorticoids
- Major hormone of mineralocorticoids
- Binds to receptor molecules in the kidney, but it also affects the intestine, sweat glands and salivary glands.
- causes sodium ions and water to be retained in the body
Aldosterone
regulates blood nutrient levels.
Glucocorticoids
- major hormone of glucocorticoids
- Responds in stressful situations
- Increases the breakdown of proteins and lipids. It also increases their conversion to forms of energy the body can use.
- Reduces inflammatory and immune responses (Cortisone)
Cortisol
- Stimulate the development of male sexual characteristics.
- However, both male and female possess these hormones.
- Abnormally high level of it can exaggerate male characteristics in both male and female
Gonadocorticoids - Androgens
- Consists of the pancreatic islets (Islets of Langerhans).
- These islets secrete three hormones: 1)insulin 2)glucagon and 3)somatostatin
- These hormones help regulate levels of nutrients especially glucose.
Pancreas
______ has an essential role in maintaining homeostasis.
Blood glucose
Effect of Decreased blood glucose level
- A decreased blood glucose will cause tissues to break down lipids and proteins to provide an alternative source of energy.
- As lipids break down, the liver converts fatty acids to ketones. As a result, acidosis can occur.
Effect of Increased blood glucose level
The kidneys produce large volume of urine containing substantial amount of glucose. However, dehydration can result because of rapid loss of water in the form of urine.
- Released from the beta cells
- Major target tissues: liver, adipose tissue, muscle and satiety area of hypothalamus.
- Increases when there is elevated blood glucose level
- Increases in response to parasymphatetic stimulation associated with digestion
- Increases when there is an increased blood levels of certain amino acids
Insulin
Occurs when too little insulin is secreted from the pancreas
Type 1 Diabetes Mellitus
Occurs when lack of number of insulin receptors on target cells or defective target cells do not respond normally to insulin.
Type 2 diabetes mellitus
- Released from the alpha cells
- Binds to membrane-bound receptors of the liver, causing glycogen to convert to glucose.
- Glucose – released into the bloodstream
Glucagon
- Released from the delta cells
- Response to food intake
- Inhibit secretion of insulin and glucagon * Inhibits gastric activity.
Somatostatin
- structures of the reproductive tract which has an essential role in reproduction.
- Aside from producing sperm cells or egg cells, these structures also plays a role in the endocrine system.
Testes and ovaries
- secreted by the testes
- male sex hormone
- responsible for the growth and development of the male reproductive structures and as well as sexual characteristics
Testosterone
- female sex hormones
- These hormones work together on the growth and development of the female reproductive structures, breasts, hips, thighs and as well as sexual characteristics.
Estrogen and progesterone
- lies in the upper part of the thoracic cavity which functions in immunity.
- It secretes the hormone “thymosin” which aids in the development of the T-cells.
Thymus
- small, pinecone-shaped structure located superior and posterior to the thalamus of the brain.
- produces the hormone “melatonin” which decreases secretion of LH and FSH
Pineal gland
