Ch 49 Flashcards
endocrine regulation
hormone signaling within the body
What type of signal are hormones?
Chemical signals, hormones are the way cells communicate and talk to each other
How are hormones moved throughout the body?
they are secreted into the interstitial fluid and typically transported by the blood
What do endocrine glands do?
secrete and produce hormones
hormones
chemical messengers that regulate many physiological processes, hormones excite or stimulate changes in specific tissues
endocrine glands vs exocrine glands
NOT THE SAME THING, endocrine secrete hormones within interstitial fluid or blood, exocrine release their secretions into ducts
target cells
the cells influenced by a particular hormone, target cells may be in another endocrine gland or in an entirely different type of organ, target cells may be located far from the endocrine gland (ex. thyroid gland secretes hormones that stimulate metabolism in tissues throughout the body)
Which responds more quickly, the endocrine system or the nervous system?
The nervous system responds more quickly but the results of the endocrine system are longer lasting
How are hormones removed from the blood?
by the liver which inactivates them and by the kidneys which excrete them
How is most endocrine action regulated?
by negative feedback systems which are regulatory systems in which a change in some steady state triggers a response that counteracts, or reverses, the change, restoring homeostasis
How does the body respond when the concentration of calcium in the blood is below the homeostatic level?
a decrease in calcium concentration in the plasma signals the parathyroid glands to release more parathyroid hormone, this hormone increases the concentration of calcium in the blood, when the calcium concentration rises above normal limits, the parathyroid glands slow their output of hormone, both responses are negative feedback systems, an increase in calcium concentration results in decreased released of parathyroid hormone, whereas a decrease in calcium leads to increased hormone secretion, in each case the response counteracts the inappropriate change, restoring the steady state
How do the nervous and endocrine systems work together?
the nervous system responds rapidly to stimuli by transmitting electrical and chemical signals, neurons signal other neurons, muscle cells, and gland cells, including endocrine cells, the nervous system helps regulate many endocrine responses, the endocrine system will then release certain hormones that could potentially effect which neurotransmitters are released
What are four major chemical groups to which hormones are assigned? Give two examples for each group.
fatty acid derivatives: prostaglandins and the juvenile hormones of insects; steroids: the molting hormone of insects, anything from the adrenal cortex, testis, ovary and placenta such as testosterone, or estrogen; amino acid derivatives: thyroid hormones such as epinephrine and norepinephrine; peptides/proteins: glucagon and antidiuretic hormone (ADH)
What is the basic structure of each of the four major chemical groups of hormones?
fatty acids: have long hydrocarbon chains, steroids: have a lot of rings of carbon and hydrogen, amino acids: their names end with -ine, peptides: peptide means protein, amino acids hooked in short chains, are specialized for moving through blood
classical endocrine signaling
hormones are secreted by endocrine glands and are transported by the blood to target cells
neuroendocrine signaling
neuroendocrine cells produce neurohormones that are transported dwn axons and released into the interstitial fluid, they typically diffuse into capillaries and are transported by the blood, invertebrate endocrine systems are largely neuroendocrine, in vertebrates the hypothalamus produces neurohormones that link the nervous system with the pituitary gland, an endocrine gland that secretes several hormones, this is almost exactly like classical except the only difference is which cell makes it (neuron)
autocrine regulation (signaling)
auto=self, the cell signals itself
paracrine regulation (signaling)
para=nearby, it secretes a hormone into the interstitial fluid to a neighboring cell, the cell doesn’t get picked up by the blood,
local regulator
a signaling molecule that diffuses through the interstitial fluid and acts on nearby cells, most endocrinologists include at least certain local regulators as hormones
Steroid and thyroid hormones
both are hydrophobic which means that they can pass through the plasma membrane and get into the cell, once in the cell they combine with receptors within the target cell, the hormone-receptor complex may activate or repress transcription of messenger RNA coding for specific proteins
How does a hormone change the action of a cell?
by changing the genes it uses, some parts of the cell’s DNA aren’t used until a hormone ‘turns it on’ inside the cell
peptide hormones
are hydrophilic which means they cannot enter the target cells, since they can’t enter the cell they combine with receptors on the plasma membrane of target cells rather than inside of the cell, many of these hormones bind to G protein-linked receptors or receptor tyrosine kinases, they act via signal transduction, hormones are primary messengers in this case that affect secondary messengers, since these hormones can’t get into the cell themselves the second messengers alter the activity within the cell
kinases and phosphotase
Kinases are enzymes that phosphorylate (add phosphate groups to things), Phosphotase is an enzyme that removes phosphate groups from things
Examples of second messengers used with peptide hormones
cyclic AMP (cAMP), calcium ions, kinases, and phospho-proteins
Receptor tyrosine kinases
enzyme-linked receptors, bind growth factors including insulin and nerve growth factors, receptor itself activates second messengers
signal amplification
occurs as each hormone receptor complex stimulates the production of second messenger molecules, second messengers activate protein kinase molecules that activate protein molecules
growth factors
stimulate cell division and normal development in specific types of cells
local regulators as hormones
some local regulators are considered hormones, they use autocrine or paracrine signaling, local regulators include growth factors, peptides that stimulate cell division and development, and prostaglandins, a group of local hormones that help regulate many metabolic processes
What are hormone receptors?
large proteins, or glycoproteins
Receptor down-regulation and receptor up-regulation
down-regulation decreases the sensitivity of target cells to the hormone, so it dampens the hormone’s ability to carry out its function, up-regulation occurs when the concentration of a particular hormone is too low, increasing the number of receptors on the plasma membrane increases the hormone’s effect on the cell
Hormone-receptor complex
formed when specific protein receptors in the cytoplasm or in the nucleus bind with the hormone
Two main types of cell-surface receptors that bind hormones
G protein-linked receptors and enzyme-linked receptors
What are the steps involved in a hydrophobic molecule changing a cell’s processes?
1: hormone molecules pass through plasma membrane, 2: hormone moves through cytosol, 3: hormone passes through nuclear envelope and binds with receptor in nucleus, 4: activated receptor is transcription factor that binds to and activates (or represses) specific genes, 5: specific proteins are synthesized, 6: proteins alter cell processes
G protein-linked receptors
transmembrane proteins that initiate signal transduction, they convert an extracellular hormone signal into an intracellular signal that affects some cell process, the hormone does not enter the cell, rather it serves as the first messenger and relays information to a second messenger which then signals effector molecules that carry out the action, G protein-linked receptors activate G proteins
G proteins
activated by G protein-linked receptors, are a group of integral regulatory proteins, the G indicates that they bind guanosine triphosphate (GTP) which, like ATP, is an important molecule in energy reactions
What is the process by which hydrophilic hormones change cell processes?
1) peptide hormone (first messenger) binds with G protein-linked receptors in plasma membrane of target cell, G protein is activated and activates the enzyme adenylyl cyclase, 2) adenylyl cyclase converts ATP to cAMP (second messenger), 3) cAMP relays signal and activates protein kinase or some other protein that leads to a response, some cell activity is altered, look on page 1059, figure 49-5 for help with this
enzyme-linked receptors
are transmembrane proteins with a hormone-binding site outside the cell and an enzyme site inside the cell, these receptors are not linked to G proteins, they function directly as enzymes or are directly linked to enzymes, most enzyme-linked receptors are receptor tyrosine kinases that bind growth factors and other signal molecules, including insulin, when the receptor is activated, it phosphorylates the amino acid tyrosine in specific signaling proteins inside the cell
Functions of hormones in invertebrates
help regulate: metabolism, growth and development, regeneration, molting, metamorphosis, reproduction and behavior
How do hormones regulate insect development?
hormones control development in insects, when stimulated by some environmental factor, neuroendocrine cells in the insect brain secrete brain hormone (BH), which is transported down axons and stored in the paired corpora cardiac, when released from the corpora cardiac, BH stimulates the prothoracic glands, endocrine glands in the prothorax, to produce molting hormone (MH), also called ecdysone, molting hormone, a steroid hormone, stimulates growth and molting; in the immature insect, paired indocrine glands called corpora allata secrete juvenile hormone (JH), this hormone suppresses metamorphosis at each larval molt so that the insect increases in size while remaining in its immature state, after the molt, the insect is still in a larval stage, when the concentration of JH decreases below some critical level, metamorphosis occurs and the insect is transformed into a pupa, in the absence of JH the pupa molts and becomes an adult, the nervous system regulates the secretory activity of the corpora allata and the amount of JH decreases with successive molts
What is the function of juvenile hormone in insects?
it suppresses metamorphosis at each larval molt
What are the endocrine glands that are present in vertebrates?
hypothalamus, posterior pituitary, anterior pituitary, thyroid gland, parathyroid gland, pancreas, adrenal medulla, adrenal cortex, pineal gland, ovary, and testis
hyposecretion vs hypersecretion
hyposecretion is an abnormally reduced output of hormones, if this occurs the target cells are deprived of needed stimulation; hypersecretion is an abnormally increased output of hormones, if this occurs the target cells may be overstimulated, any of these abnormalities leads to loss of homeostasis
What organ is most endocrine activity controlled by, either directly or indirectly?
the hypothalamus
What organ links the endocrine and nervous systems both anatomically and physiologically?
The hypothalamus
What gland is connected to the hypothalamus?
the pituitary gland is connected to the hypothalamus by the pituitary stalk
pituitary gland
because secretions of the pituitary gland control the activities of several other endocrine glands, biologists refer to it as the master gland of the body, the pituitary gland produces six peptide hormones that exert far-reaching influence over growth, metabolism, reproduction, and many other body activities, the human pituitary gland consists of an anterior and posterior lobe, but in some vertebrates an intermediate lobe is present
posterior lobe of the pituitary gland
secretes oxytocin and antidiuretic hormone (ADH), these two hormones are PRODUCED by cells in the hypothalamus but SECRETED by the posterior lobe, these hormones are enclosed within vesicles and transported down the axons of the neuroendocrine cells into the posterior lobe, they are then stored in the axon terminals until the neuron is stimulated, then they are released and diffuse into surrounding capillaries
function of antidiuretic hormone (ADH), where it comes from, and where it’s target tissue is
ADH stimulates reabsorption of water in the kidneys, it comes from the posterior pituitary and it’s target tissue is the kidneys
oxytocin: function, gland, and target tissue
oxytocin is released from the posterior pituitary, it’s target tissues are either the uterus or the mammary glands, oxytocin stimulates contraction when its target tissue is the uterus, towards the end of pregnancy the oxytocin concentration in the blood rises which stimulates strong contractions of the uterus that are needed to expel a baby, oxytocin is sometimes administered clinically to initiate or speed labor; after birth, when an infant sucks on its mother’s breast, sensory neurons signal the pituitary to release oxytocin, the hormone stimulates the ejection of milk into ducts, making it available to nursing infants; because oxytocin stimulates the uterus to contract, breastfeeding promotes the recovery of the uterus to nonpregnant size
releasing and inhibiting hormones: what gland secretes them, what is their target tissue, and what are their functions?
releasing and inhibiting hormones are released from the hypothalamus, their target tissue is the anterior lobe of the pituitary, and the regulate the secretion of hormones by the anterior pituitary
growth hormone (GH): gland it’s secreted from, target tissue, and function
secreted by the anterior pituitary gland, it’s target tissue is ‘general’, and it stimulates the growth of skeleton and muscle
prolactin: gland that secretes it, target tissue, and function
secreted by the anterior pituitary, it’s target tissue is mammary glands, and it stimulates milk production
melanocyte-stimulating hormones (MSH): gland that secretes it, target tissues, and function
secreted by the anterior pituitary gland, it’s target tissue are pigment cells in skin, and it’s function is to stimulate melanin production in some animals, but in humans it’s function is to help regulate food intake
thyroid-stimulating hormone (TSH): gland that secretes it, target tissue, and function
secreted by the anterior pituitary gland, it’s target tissue is the thyroid gland, it stimulates the secretion of thyroid hormones and helps regulate bone remodeling
adrenocorticotropic hormone (ACTH): gland that secretes it, target tissue, and function
secreted by the anterior pituitary gland, it’s target tissue is the adrenal cortex, it’s function is to stimulate the secretion of adrenal cortical hormones
gonadotropic hormones: gland that secretes it, target tissue, and function
secreted by the anterior pituitary gland, it’s target tissue is the gonads, and it’s function is to stimulate gonad function and growth
thyroxine (T4) and triiodothyronine (T3): gland that secretes it, target tissue, and function
secreted by the thyroid gland, it’s target tissue is ‘general’, and it’s function is to stimulate metabolic rate and regulate energy metabolism
calcitonin: gland that secretes it, target tissue, and function
secreted by the thyroid gland, it’s target tissue is bone, and it’s function is to lower the blood calcium level; calcitonin “tones up” bones
parathyroid hormone: gland that secretes it, target tissue, and function
secreted by the parathyroid glands, it’s target tissue is bone, kidneys, and digestive tract, it’s function is to regulate blood calcium levels
insulin: gland that secretes it, target tissue, and function
secreted by the pancreas, it’s target tissue is ‘general’ tissue, and it’s function is to lower blood glucose concentration
glucagon: gland that secretes it, target tissue, and function
secreted by the pancreas, it’s target tissue is liver and adipose tissue, it’s function is to raise blood glucose concentration
epinephrine and norepinephrine: gland that secretes it, target tissue, and function
secreted by the adrenal medulla, it’s target tissue is muscle, blood vessels, liver, and adipose tissue, it’s function is to help the body cope with stress, increase metabolic rate, raise blood glucose levels, and increase heart rate and blood pressure
mineralocorticoids: gland that secretes it, target tissue, and function
secreted by the adrenal cortex, it’s target tissue is the kidney tubules, and it’s function is to maintain sodium and potassium balance
glucocortoids: gland that secretes it, target tissue, and functions
secreted by the adrenal cortex, it’s target tissue is general tissue, and it’s function is to help the body cope with long-term stress and raise blood glucose levels
melatonin: gland that secretes it, target tissue, and function
secreted by the pineal gland, it’s target tissue is the hypothalamus, and it’s function is to regulate biological rhythms
estrogens: gland that secretes it, target tissue, and function
secreted by the ovary, it’s target tissue is general tissues and the uterus, it’s function is to develop and maintain sex characteristics in females and to stimulate the growth of uterine lining
progesterone: gland that secretes it, target tissue, and function
secreted by the ovary, it’s target tissue is the uterus and the breasts, it’s function is to stimulate the development of uterine lining
testosterone: gland that secretes it, target tissue, and function
secreted by the testis, it’s target tissue is general tissues and reproductive structures, it’s function is to develop and maintain sex characteristics in males and to promote spermatogenesis
What results from hyposecretion of growth hormone? Hypersecretion?
hyposecretion of growth hormone results in pituitary dwarfism, and hypersecretion results in gigantism if malfunction occurs in childhood and acromegaly if it occurs in adulthood
What results from hyposecretion of thyroid hormones? Hypersecretion?
hyposecretion results in cretinism (in children), myxedema, a condition of prounounced adult hypothyroidism, dietary iodine deficiency leads to hyposecretion and goiter; hypersecretion leads to hyperthyroidism, increased metabolic rate, nervousness, irritability, goiter, and Graves’ disease
What results from hyposecretion of parathyroid hormone? Hypersecretion?
hyposecretion results in spontaneous discharge of nerves, spasms, tetany, and death; hypersecretion results in weak and brittle bones, and kidney stones
What results from hyposecretion of insulin? Hypersecretion?
hyposecretion of insulin results in diabetes mellitus; hypersecretion results in hypoglycemia
What results from hyposecretion of hormones of the adrenal cortex? Hypersecretion?
hyposecretion results in Addison’s disease; hypersecretion results in Cushing’s Syndrome
What hormone acts antagonistically to parathyroid hormone?
Calcitonin, which is secreted by the thyroid
Where are the islets of Langerhans? What do they do?
the islets of Langerhans are located on the pancreas, they secrete insulin and glucagon
How does insulin work in the bloodstream? Glucagon?
insulin converts glucose in the bloodstream to glycogen in the cells, glucagon works oppositely by converting glycogen to glucose
What forms estrogen/testosterone in the opposite sex?
the adrenal cortex
What is the adrenal medulla made up of?
neural tissue
What’s the difference in location of the adrenal cortex and the adrenal medulla?
the adrenal cortex is the outer part of the adrenal gland whereas the adrenal medulla is on the inside
What do islets of Langerhans consist of?
beta cells, which secrete insulin, and alpha cells, which secrete glucagon
Where are receptor molecules found?
in the nucleus, cell membrane, and cytoplasm of target cells; they are NOT found in interstitial fluid
Which hormone exerts antagonistic action to insulin?
glucagon (both are made in Islets of Langerhans)
