Module 09: Endocrine System Flashcards
This system is composed of endocrine glands and specialized endocrine cells located throughout the body.
Endocrine System
Endocrine glands and cells secrete very small amounts of chemical messengers called ____________into the extracellular fluid. These diffuse into the blood to be transported to their target. They also circulate through the bloodstream to specific sites called target tissues or effectors. At their target tissues, they stimulate a specific response.
Hormones
These are the specific sites in the bloodstream where the hormones circulate and stimulate their specific response.
Target Tissues
Where is the term endocrine derived from?
derived from the Greek words endo, meaning “within,” and krino, “to secrete”-appropriately describes this system.
What makes exocrine glands different from endocrine glands?
Exocrine glands have ducts that carry their secretions to the out- side of the body, or into a hollow organ, such as the stomach or intestines. Examples of exocrine secretions are saliva, sweat, breast milk, and digestive enzymes.
This is where coordination to maintain the body’s homeostasis occurs. These allow cells to communicate with each other to regulate body activities.
Chemical Messengers
What are the four (4) chemical messengers in the endocrine system?
(1) Autocrine chemical messengers
(2) Paracrine chemical messengers
(3) Neurotransmitters
(4) Endocrine chemical messengers
This chemical messenger stimulates the cell that originally secreted it. Good examples of these chemical messengers are those secreted by white blood cells during an infection that have the capacity to replicate.
Autocrine chemical messengers
These chemical messengers are secreted by cells in a local area, which influences the activity of the same cell or cell type from which it was secreted.
Autocrine chemical messengers
What are some examples of Autocrine chemical messengers?
(1) Eicosanoids (prostaglandins, thromboxane, prostacyclin, and leukotrienes)
These chemical messengers act locally on neighboring cells. These chemical messengers are secreted by one cell type into the extracellular fluid and affect surrounding cells.
Paracrine chemical messengers
These chemical messengers are produced by a wide variety of tissues and secreted into extracellular fluid; has a localized effect on other tissues
Paracrine chemical messengers
What are some examples of Paracrine chemical messengers?
Somatostatin, histamine, eicosanoids
These stimulates vasodilation in nearby blood vessels.
Histamine
These chemical messengers are secreted by neurons that activate an adjacent cell, whether it is another neuron, a muscle cell, or a glandular cell. These are secreted into a synaptic cleft, rather than into the bloodstream
Neurotransmitters (neurotransmitters are paracrine chemical messengers)
These chemical messengers are produced by neurons; secreted into a synaptic cleft by presynaptic nerve terminals; travels short distances; influences postsynaptic cells
Neurotransmitters
What are some examples of neurotransmitters?
Acetylcholine, epinephrine
These chemical messengers are secreted into the bloodstream by certain glands and cells, which together constitute the endocrine system. These chemical messengers travel through the blood to their target cells.bo
Endocrine chemical messengers
These chemical messengers are secreted into the blood by specialized cells; travels some distance to target tissues; results in coordinated regulation of cell function
Endocrine chemical messengers
What are some examples of Endocrine chemical messengers?
Thyroid hormones, growth hormone, insulin, epinephrine, estrogen, progesterone, testosterone, prostaglandins
What is the function of hormones’?
Hormones of the endocrine system are secreted in response to humoral, neural, or hormonal stimuli to regulate homeostasis.
What are the main regulatory functions of the endocrine system?
(1) Regulation of metabolism.
(2) Control of food intake and digestion.
(3) Modulation of tissue development
(4) Regulation of ion levels.
(5) Control of water balance
(6) Regulation of cardiovascular functions.
(7) Control of blood glucose and other nutrients.
(8) Control of reproductive functions.
(9) Stimulation of uterine contractions and milk release.
(10) Modulation of immune system function.
This function of the endocrine system pertains to the act of controlling the rate of nutrient utilization and energy production.
Regulation of metabolism.
This function of the endocrine system pertains to the act of regulating the level of satiation (fullness) and the breakdown of food into individual nutrients.
Control of food intake and digestion.
This function of the endocrine system pertains to the act of influencing the development of tissues, such as those of the nervous system
Modulation of tissue development
This function of the endocrine system pertains to the act of helping to monitor blood pH, as well as Na, K, and Ca2+ concentrations in the blood.
Regulation of ion levels.
This function of the endocrine system pertains to the act of regulating water balance by controlling the solute concentration of the blood as well as controlling membrane
Control of water balance
This function of the endocrine system pertains to the act of helping to regulate the heart rate and blood pressure and prepare the body for physical activity.
Regulation of cardiovascular functions.
This function of the endocrine system pertains to the act of regulating the levels of glucose and other nutrients in the blood.
Control of blood glucose and other nutrients.
This function of the endocrine system pertains to the act of controlling the development and functions of the reproductive systems in males and females.
Control of reproductive functions
This function of the endocrine system pertains to the act of regulating uterine contractions during delivery and stimulates milk release from the breasts in lactating females
Stimulation of uterine contractions and milk release
This function of the endocrine system pertains to the act of helping the control the production of immune cells.
. Modulation of immune system function.
What are the two chemical categories of hormones?
(1) lipid-soluble hormones and
(2) water-soluble hormones
What is the basis of hormone metabolism?
its transport in the blood, its interaction with its target, and its removal from the body
These hormones are derived from cholesterol.
Steroid hormones
These hormones’ are derived from amino acid tyrosine,
thyroid hormones (other hormones are categorized as amino acid derivatives, peptides, or proteins.)
This chemical category of hormones are nonpolar, and include steroid hormones, thyroid hormones, and fatty acid derivative hormones, such as certain eicosanoids.
Lipid-soluble hormones (can last for several days to weeks)
What are the three mechanism that could potentially result in the removal of lipid-soluble hormones from the body?
Lipid-soluble hormones’ are unprotected and may not effectively regulate.
(1) breakdown by enzymes in the liver or enzymes in the lungs.
(2) excretion into urine by the kidneys or bile from the liver, and
(3) breakdown by enzymes in the bloodstream.
Lipid soluble hormones are bounded in these. These are the “chaperone” the hormone. And helps in reducing the rate at which lipid-soluble hormones are degraded or removed from the blood.
Binding proteins
This chemical category of hormones are polar molecules; they include protein hormones, peptide hormones, and most amino acid derivative hormones.
Water-soluble hormones
How are water soluble transported?
(1) Most of them dissolve directly into the blood and are delivered to their target tissue without attaching to a binding protein
(2) Due to their size, they do not readily diffuse through the walls of all capillaries; therefore, they tend to diffuse from the blood into tissue spaces more slowly
These limit the length of time they are active, and body processes change quickly when hormones are secreted and remain functional for only short periods.
destruction and elimination of hormones
How long do water soluble hormones last?
have relatively short half-lives because they are rapidly broken down by enzymes within the bloodstream but they have concentrations that change rapidly within the blood and tend to regulate activities that have a rapid onset and short duration.
What are the three (3) modifications made to hormone molecules that help protect them from being destroyed?
- Having a carbohydrate attached to them.
- Having a terminal end protected from protease activity,
- Having binding proteins
These hormones circulate in the plasma longer than free water-soluble hormones do.
Bound Hormones
What are the three (3) types of stimuli regulate hormone release
(1) humoral,
(2) neural, and
(3) hormonal
In this, the blood level of most hormones fluctuates.
homeostatic range
Molecules and ions in the bloodstream can directly stimulate the release of some hormones. These chemicals are referred to as __________________. The cells that secrete these hormones have receptors for certain substances in the blood.
humoral stimuli.
This word pertains to body fluids, including blood
humoral
Examples:
(1) hormone (PTH) is released in response to the chemical’s concentration.
(2) elevated blood glucose levels directly stimulating the pancreas to secrete the hormone insulin,
(3) elevated blood potassium levels directly stimulating the adrenal cortex to secrete the hormone aldosterone.
This hormone regulation involves neural stimuli of endocrine glands. In this, following action potentials, neurons release a neurotransmitter into the synapse with the cells that produce the hormone In some cases, the neurotransmitter stimulates the cells to increase hormone secretion.
Neural stimuli
Give an example of neural stimuli.
For example, the sympathetic nervous system stimulates the secretion of epinephrine and norepinephrine, from the adrenal gland during exercise. Epinephrine and nor- epinephrine increase heart rate and, in turn, increase blood flow through the exercising muscles.
Some neurons secrete chemical messengers directly into the blood when they are stimulated, making these chemical messengers hormones, which are called _______________. They stimulate the secretion of releasing hormones.
neuropeptides
Specialized neuropeptides stimulate hormone secretion from other endocrine cells and are called _______________ a term usually reserved for hormones from the hypothalamus and travel in the blood to the anterior pituitary gland.
releasing hormones, (stimulating hormones)
This type of hormonal regulation occurs when a hormone is secreted that, in turn, stimulates the secretion of other hormones.
Hormonal Stimuli
These are hormones in the hypothalamus and anterior pituitary land that stimulate the secretion of another hormone.
Tropic hormones
What regulates the releasing hormones, (stimulating hormones)?
Hormonal Stimuli
What do the releasing hormones stimulate?
Releasing hormones stimulate the release of hormones from the anterior pituitary that travel in the blood to their target endocrine cell. The target endocrine cell secretes its hormone into the blood, where it travels to its target and produces a response.
How does the humoral stimuli inhibits hormone release?
In this the companion hormone’s effects oppose those of the secreted hormone and counteract its effect or action.
How does the neural stimuli inhibits hormone release?
Neurons inhibit targets just as often as they stimulate targets. If the neurotransmitter is inhibitory, the target endocrine gland does not secrete its hormone.
How does the hormonal stimuli inhibits hormone release?
hormones prevent the secretion of other hormones, which is a common mode of hormone regulation.
These hormones from the hypothalamus prevent the secretion of tropic hormones from the anterior pituitary gland.
Inhibiting hormones.
What are the two major mechanisms maintain hormone levels in the blood within a homeostatic range?
(1) negative feedback and
(2) positive feedback
In this mechanism, the hormone’s secretion is inhibited by the hormone itself once blood levels have reached a certain point and there is adequate hormone to activate the target cell.
Negative Feedback Mechanism
Why is the Negative Feedback Mechanism known as the self-limiting system?
Because the hormone may inhibit the action of other, stimulatory hormones to prevent the secretion of the hormone in question
How does the thyroid hormones inhibit the secretion of their releasing hormone?
(1) The anterior pituitary gland secretes a tropic hormone, which travels in the blood to the target endocrine cell.
(2) The hormone from the target endocrine cell travels to its target.
(3) The hormone from the target endocrine cell also has a negative- feedback effect on the anterior pituitary and hypothalamus, which decreases secretion of the tropic hormone.
This mechanism promote the synthesis and secretion of the tropic hormone in addition to stimulating their target cell. In turn, this stimulates further secretion of the original hormone.
Positive Feedback Mechanism
The Positive Feedback Mechanism is also known as what?
Self-Propagating System
Cite an example of a positive feedback mechanism.
prolonged estrogen stimulation promotes a release of the anterior pituitary hormone responsible for stimulating ovulation.
This bodily system consists of ductless glands that secrete hormones into the interstitial fluid The hormones then enter the blood.
Endocrine system
It is a small gland about the size of a pea. It is housed in a depression of the sphenoid bone inferior to the hypothalamus of the brain.
Pituitary Gland
This serves as a control center for the autonomic nervous system as well as the endocrine system lies superior to the pituitary gland. It is a region of the diencephalon, located inferior to the thalamus.
Hypothalamus
The pituitary gland lies posterior to the optic chiasm and is connected to the hypothalamus by a stalk called the ____________.
infundibulum
The pituitary gland can be divided into two parts, namely:
(1) Anterior Pituitary Gland
(2) Posterior Pituitary Gland
This part of the pituitary gland is made up of epithelial cells derived from the embryonic oral cavity.
Anterior Pituitary Gland
This part of the pituitary gland is n extension of the brain and is composed of neurons.
Posterior Pituitary Gland
Why was the pituitary gland known as the master gland?
Hormones from the pituitary gland control the functions of many other glands in the body, such as the ovaries, the testes, the thyroid gland, and the adrenal cortex.
How does the hypothalamus control the pituitary gland?
(1) hormonal control and
(2) direct innervation.
Explain the hypothalamic control of the anterior pituitary gland
(!) Neurons of the hypothalamus produce neuropeptides and secrete them into a capillary bed in the hypothalamus. Stimuli within the nervous system regulate the secretion of releasing hormones and inhibiting hormones (circles) from neurons of the hypothalamus.
(2) Releasing hormones and inhibiting hormones pass through the hypothalamohypophysial portal system to the anterior pituitary.
(3) Once the neuropeptides arrive at the anterior pituitary gland, they leave the blood and bind to membrane-bound receptors involved with regulating anterior pituitary hormone secretion. The capillary beds and veins that transport the releasing and inhibiting hormones are called the hypothalamic-pituitary portal system. The hypothalamic neuropeptides function as either releasing hormones or inhibiting hormones. Each releasing hormone stimulates the production and secretion of a specific hormone by the anterior pituitary. Each inhibiting hormone reduces the production and secretion of a specific hormone by the anterior pituitary.
(4) In response to releasing hormones, anterior pituitary hormones (squares) travel in the blood to their target tissue, which in some cases, are other endocrine glands.
The capillary beds and veins that transport the releasing and inhibiting hormones are called the ________________________.
hypothalamic-pituitary portal system
Explain the hypothalamic control of the posterior pituitary gland
(1) Stimulation of neurons within the hypothalamus controls the secretion of the posterior pituitary hormones.
(2) Action potentials are conducted by axons of the hypothalamic neurons through the hypothalamohypophysial tract to the posterior pituitary. The axon endings of neurons store hormones in the posterior pituitary.
(3) In the posterior pituitary gland, action potentials cause the release of hormones (circles) from axon terminals into the circulatory system.
(4) The hormones pass through the circulatory system and influence the activity of their target tissues.
The hormones secreted from the anterior pituitary are _____________. They are transported in the blood, have a life span measured in minutes, and bind to membrane-bound receptors on their target cells.
Proteins
This hormone in the anterior pituitary gland stimulates the growth of bones, muscles, and other organs by increasing gene expression. It also slows protein breakdown (protein synthesis) during periods of food deprivation and favors lipid breakdown (for energy metabolism) and release in the cells. It also encourages the increase in blood glucose levels
Growth Hormone
How does the GH increase blood glucose levels?
By reducing glucose utilization (insulin antagonist)
Too little growth hormone secretion can result from abnormal development of the pituitary gland. A young person suffering from a deficiency of growth hormone remains small, although normally proportioned, and is called a _________________.
pituitary dwarf (dwarf)
How can GH be administered?
The gene in the bacteria causes GH synthesis, and the GH can be extracted from the medium in which the bacteria are grown.
What is the target tissue of the GH?
Most Tissues
The person becomes abnormally tall, a condition called ____________-.
Giantism
If excess hormone is secreted after growth in bone length is complete, growth continues in bone diameter only. As a result, the facial features and hands become abnormally large, a condition called _______________.
acromegaly
What are the two (2) hormones that controls the secretion of growth hormone?
(1) A releasing hormone stimulates growth hormone secretion, and
(2) an inhibiting hormone inhibits its secretion.
Part of the effect of growth hormone is influenced by a group of protein hormones called _______________.
insulin-like growth factors (IGFs), or somatomedins
What is the relationship of GH and the insulin-like growth factors (IGFs), or somatomedins?
Growth hormone increases IGF secretion from tissues such as the liver, and the IGF molecules bind to receptors on the cells of tissues such as bone and cartilage, where they stimulate growth. The IGFs are similar in structure to insulin and can bind, to some degree, to insulin receptors. Also, insulin, at high concentrations, can bind to IGF receptors.
This hormone in the anterior pituitary gland binds to membrane-bound receptors on cells of the thyroid gland and stimulates the secretion of thyroid hormone. This can also stimulate growth of the thyroid gland.
Thyroid-stimulating hormone (TSH)
This triggers the pituitary gland to release Thyroid-stimulating hormone (TSH).
Thyrotropin releasing hormone
How is the rate of TSH regulated?
The rate of TSH secretion is regulated by a releasing hormone from the hypothalamus
What is the target tissues of the Thyroid-stimulating hormone (TSH)?
Thyroid Gland