module 11

receptor kinases

-For some peptide hormones (like insulin) the receptor itself is a kinase ---Can directly phosphorylate intracellular proteins that alter cellular activity - For other peptide hormones (like growth hormone) the receptor itself is not a kinase -Rather it activates intracellular kinases the hormone-bound receptor recruits and activates intracellular kinases, which then initiate the cellular response. when a receptor is a kinase.

Transport and receptor binding

1. hormone passes through plasma membrane 2. inside target cell the hormone binds to a receptor protein in the cytoplasm or nucleus. 3. hormone-receptor complex binds to hormone response element on DNA regulating gene transcription 4. protein sysnthesis 5. change in protein synthesis is cellular response.

hypothalamic production of the neurohormones

ADH and oxytocin are actually produced by neuron cell bodies located in the hypothalamus. These two neurohormones are transported along the axon tract that runs from the hypothalamus to the posterior pituitary, where they are stored. Because this reflex control involves both the nervous and the endocrine systems, ADH and oxytocin are said to be secreted by a neuroendocrine reflex.

An example of positive feedback: ovulation

As the oocyte grows, follicle cells surrounding it produce increasing levels of the steroid hormone estrogen., resulting in a progressive rise in estrogen in the blood. peak estrogen levels signal the hypothalamus that the oocyte is ready to be ovulated. page 950

Pheromones

Chemical signals released by an animal that communicate information and affect the behavior of other animals of the same species. do not participate in a normal regulation of the body.

Antidiuretic hormone

In the early 1950s investigators isolated a peptide from the posterior pituitary, ADH. ADH stimulates water reabsortpion by the kidneys and in doing so inhibits urine production. When ADH is missing, as it was in the shooting victim, the kidneys do not reabsorb as much water, and excessive quantities of urine are produced.

second-messenger systems

Many hydrophilic hormones, such as epinephrine, work through second-messenger systems. the interaction between the hormone and its receptor activates the mechanisms in the plasma membrane that increase the concentration of the second messengers within the target cell cytoplasm. the hydrophilic hormone activates a g protein which activates an enzyme that produces a second messenger that activates a protein kinase in order to effect the target protein.

Vitamin D

Produced in the skin from a cholesterol derivative in response to ultraviolet light.

The anterior pituitary produces seven hormones

The anterior pituitary is not part of the nervous system. it is an independent endocrine gland. The hormones produced and secreted by different cell types in the anterior pituitary can be categorized into three structurally similar families: the anterior pituitary is regulated nuero hormones of two classes from the hypothalamus: releasing hormones inhibitory hormones the peptide hormones, the protein hormones, and the glycoprotein hormones.

thyroid related disorders

Thyroid hormones work by binding to nuclear receptors located in most cells in the body, influencing the production and activity of a large number of cellular proteins. thyroid hormones regulate enzymes controlling carbohydrate and lipid metabolism in most cells, promoting the appropriate use of these fuels for maintaing the body's basal metabolic rate. some of the most dramatic cells of thyroid hormones are observed in their regulation of growth and development. in humans the thyroid hormones promote growth of neurons and stimulate maturation of the CNS.

Prostaglandins

a particularly diverse group of paracrine regulators. a 20-carbon long fatty acid that contains a five membered carbon ring.

neurohormones

a type of hormone released into the blood stream by neurons. allowing the nervous system to control cells that are not directly linked to it.

The hormones epinephrine and norepinephrine, which constitute the "alarm" response of the body to stress, are secreted by the

adrenal medulla

The major peripheral endocrine glands

adrenal medulla and the pancreas are independent of pituitary control.

feedback

an important part of endocrine regulation. negative feedback example page 949. thyroxin.

the posterior pituitary is responsible for the release of only two hormones.

antidiuretic hormone and oxytocin. neither are tropic and both are peptides. Antidiuretic hormone causes water to be reabsorbed into the kidneys and then into the blood, which decreaes urine production. oxytocin - reduces social anxiety and enhances positive emotion when released during a social situation. oxytocin stimulates uterine contractions during childbirth, milk let down during breast feeding. and maternal bonding between mother and child.

The hypothalamus and pituitary glands

are vital to the maintenance to homeostasis.

The signals of the endocrine system are transmitted to the appropriate target organ via

blood

calcium homeostasis is regulated by several hormones

calcium is a vital component of the vertebrate body both because of its being a structural component of bones and because of its role in ion-mediated processes such as muscle contraction. the thyroid and para thyroid glands act with vitamin D to regulate calcium homeostasis.

The adrenal gland releases both

catecholamine and steroid hormones

target cells

cells that have receptors for a particular hormone

releasing hormones

chemical that stimulates other glands to release their hormones

Pheromones

chemicals secreted by animal species that influence the behavior of other animals of the same species

some molecules act as both...

circulating hormones and neurotransmitters. A molecule produced by an endocrine gland and used as a hormone may also be produced and used as a neurotransmitter by neurons. the hormone norepinephrine is secreted into the blood by the adrenal glands but is also released as a neurotransmitter by sympathetic nerve endings.

the hypothalamus...

controls the hormonal secretions of the anterior-pituitary gland, and produces the hormones of the posterior pituitary.

An example of a hormone that exerts its action within the target cell only by interacting with cell-surface receptors is

cortisol

There four mechanisms of cell communication:

direct contact, synaptic signaling, endocrine signaling, and paracrine signaling.

positive feedback

drives more change to occur.

neurohormones.

hormones secreted by neurons that are carried by blood.

hydrophilic hormones activate receptors on target cell membranes

hormones that are too large or too polar to cross the plasma membranes of their target cells include all of the peptide, protein, and glycoprotein hormones, as well as the catecholamine hormones. by regulating protein kinases, hydrophilic hormone receptors exert a powerful influence over the broad range of intracellular functions.

inhibitory hormones

inhibit the release of hormones from the anterior pituitary. these neural hormones are released from neuron cell bodies of the hypothalamus. they travel down the axons to a capillary bed called the primary capillaries in the stalk that connects the hypothalamus to the pituitary. these capilaries carry the hormones into portal veins. then enter the secondary capillary bed in the anterior pituitary. this is transportation is called the hypothalamohypophyseal portal system. when the neural hormones reach the anterior pituitary, the pituitary responds by releasing or stopping the release of hormones into the blood stream.

hormone

is a regulatory chemical that is secreted into extracellular fluid and carried by the blood. the highly specific interaction between hormones and their receptors enable hormones to be active at remarkably small concentrations.

Actions of lipophilic vs hydrophilic hormones.

lipophilic hormones activate intracellular receptors. the lipophilic hormones include all of the steriod hormones and thyroid hormones as well as other lipophilic regulatory molecules. Lipophilic hormones can enter cells because the lipid portion of the plasma membrane does not present a barrier.

Hormones can be categorized as

lipophilic or hydrophilic

adrenal glands

located just above each kidney. Each gland is composed of an inner portion, the adrenal medulla, and an outer layer, the adrenal cortex.

gonadotropins are

luteinizing hormones and follicle-stimulating hormones

Unlike other hormones, the hormones of the posterior pituitary gland are transported to the hypothalamus by

neuron axons

The molecule that can act as both a neurotransmitter and a hormone is

norepinephrine

Only certain organs called the target organs respond to the presence of a specific hormone because

only those organ cells have the appropriate receptors

endocrine glands

organs that are specialized to secrete hormones.

hypothalamus

part of the central nervous system and helps to integrate neural and endocrine activities. primarily acts in controlling the production and secretion of hormones from the pituitary.

paracrine regulators

produced in one tissue and regulate a different tissue of the same organ

Antidiuretic hormone (ADH) and oxytocin

produced in the hypothalamus and neuron cell bodies. the axons of these cells extend down into the posterior pituitary. these two hormones are stored in the posterior pituitary.

the thyroid gland

regulates basal metabolism and development. the thyroid gland secretes three hormones: primarily thyroxine, smaller amounts of triiodothyronine, and calcitonin.

paracrine regulators are

released into the extracellular space and effect only cells that are nearby. this allows tissues and organs to regulate themselves internally.

exocrine glands

secrete chemicals into a duct, that empties into the outside of the body or into the digestive tract.

endocrine glands

secrete chemicals into the extracellular space, where it diffuses into the blood.

when a hormone binds to a receptor on or inside a cell

signal transduction pathways are activated inside the cell that lead to the appropriate response of the hormone.

major peripheral endocrine glands

the thyroid gland regulates metabolism and development in production of three hormones. thyroxine, triiodothyronine, calcitonin. these first two hormones are known as thyroid hormones and regulate the metabolism of lipids and carbohydrates. calcitonin regulates the amount of calcium in the blood. parathyroid gland are four small glands attached to the thyroid gland. the parathyroid hormone helps regulate blood calcium levels by causing bones to release calcium. parathyroid hormones also act in the activation of vitamin D. The adrenal glands have two portions: the inner layer called the adrenal meduall and the outer layer called the adrenal cortex. the adrenal medulla secretes epinephrine and norepinephrine. which act in the fight or flight response. cortisol are steroids from the adrenal cortex.

autocrine signaling

those signals that cell releases and that bind to a receptor of the very same cell, so that it regulates itself. this is common in the cells of the immune system.

Nonpolar hormones pass through the plasma membranes of intestinal epithelial cells without being digested and therefore can be taken orally as pills. Because of this fact, which of the following are available as oral pills for human consumption?

thyroid hormone and steroid hormones

amphibians need thyroid hormones

thyroid hormones direct the metamorphism of tadpoles into frogs. if the thyroid gland is removed from a tadepole, it will not change into a frog.

The hormone ________ sets the body's basal metabolic rate.

thyroxin

the posterior pituitary stores and releases

two neurohormones. the posterior pituitary appears fibrous because it contains axons that originate in cell bodies within the hypothalamus and that extend along the stalk of the pituitary as a tract of fibers.

pituitary

unusual structure formed from tissue of different origins during development.

Autocrine signaling

when cells release signaling that affects their own behavior. an example of this would be cancer cells, where they release growth factors that stimulate their own growth.

Parathyroid hormone (PTH)

A hormone secreted by the parathyroid glands that raises blood calcium level by promoting calcium release from bone and calcium retention by the kidneys.

The action of G proteins

the binding of the hormone to its receptor causes the G protein to shuttle within the plasma membrane from the receptor to the second-messenger generating enzyme. when the G protein activates the enzyme, the result is an increase in second-messenger molecules inside the cell.

Activation versus inhibition

the cellular response to a hormone depends on the type of G protein activated by the hormone's receptor. As a result, some hormones stimulate protein kinases in their target cells, and others inhibit their targets. Furthermore, a single hormone can have distinct actions in two different cell types if the receptors in those cells are linked to different G proteins.

paracrine regulation of blood cells.

the gas nitric oxide (NO), which can function as a neurotransmitter, is also produced by the endothelium of blood vessels. It is a paracrine regulator because it diffuses to the smooth layer of the blood vessel and promotes vasodilation. the endothelium of blood vessels is a rich source of paracrine regulators which help control blood pressure.

paracrine regulators exert powerful effects within tissues

growth factors - proteins that promote growth and cell division in specific organs, are among the most important paracrine regulators. cytokines - are growth factors specialized to control cell division and differentiation in the immune system. neurotropins - growth factors that regulate the nervous system.

The pancreas

has both exocrine and endocrine functions. in its exocrine role it releases digestive enzymes and bicarbonate enzymes into the small intestine. in its endocrine role it is important in regulating carbohydrates in the blood. the pancreas produces insulin and glucagon.

Duration of hydrophilic hormone effects

The binding of a hydrophilic hormone to its receptor is reversible and usually very brief; hormones soon dissociate from receptors or are rapidly deactivated by their target cells after binding. as a result, hydrophilic hormones are capable of stimulating immediate responses within cells, but often have a brief duration of action.

Endocrine glands produce three chemical classes of hormones.

The endocrine system includes all of the organs that secrete hormones - the thyroid gland, pituitary gland, adrenal glands, and so on. hormones are referred to as endocrine secretions. three primary chemical categories of molecules meets the two requirements for being a hormone. 1. Amino acid derivatives - (aka amine hormones). produced by the modification of certain amino acids. hormones manufactured by enzymatic modification of specific amino acids. 2. Peptides and proteins - composed of amino acids. 3. Steroids - lipids manufactured by enzymatic modifications of cholesterol.

Activation of transcription in the nucleus

The hormone receptor, activated by binding to the hormone, is now also able to bind to specific regions of the DNA. These DNA regions, located in the promoters of specific genes, are known as hormone response elements. receptors therefore function as hormoneactivated transcription factors.

effects of growth hormone

The importance of the anterior pituitary is illustrated by a condition known as gigantism. gigantism is caused by an excess secretion of GH in a growing child. GH stimulates protein synthesis and growth of muscles and connective tissues.

endocrine system

The organs and tissues that produce hormones.

peptide hormones

The peptide hormones of the anterior pituitary are cleaved from a single precursor protein, and therefore they share some common sequence. ACTH, MSH Protein hormones - the protein hormones each comprise of a single chain of approximately 200 amino acids, and they share significant structural similarities., GH, PRL Glycoprotein hormones -the largest and most complex hormones known. the glycoprotein hormones are dimers, containing alpha and beta subunits, each around 100 amino acids in size. TSH, LH, FSH.

oxytocin

The posterior pituitary also secretes oxytocin, a second peptide neurohoromone that, like ADH, is composed of nine amino acids. in mammals, oxytocin stimulates the milk ejection reflex.

hormones released by the anterior pituitary

ACTH (a peptide hormone that stimulates the adrenal gland to release corticol steroid hormones. important in glucose regulation and stress response.) a tropic hormone (it is sent to other glands to trigger the release of other hormones. MSH is not tropic. stimulates the production and dispersion of melanin which is a pigment of the hair and skin GH growth hormone stimulates the growth muscle, bone, and other tissues, and it is also essential for proper metabolic regulation. prolactin PRL - stimulates the mammory glands to produce milk. regulates ion and water transport across epithelia. TSH thyroid-stimulating hormone is a tropic hormone and it stimulates the thyroid gland to produce the hormone thyroxine, which in turn regulates development and metabolism by acting on nuclear receptors. LH luteinizing hormone - tropic hormone that stimulates the production of estrogen and progesterone by the ovaries and is needed for ovulation. also needed for sperm production in males. gonatatropins. FSH follicle-stimulating hormone - required for the development of ovarian follicles in females. in males, it is required for the development of sperm. gonatatropins.

there are two types of glands

endocrine and exocrine. the pancreas can perform both functions of the two types of glands.

other signaling mechanisms

exocrine system - creates chemical signals and glands. these differ from endocrine signals in that the gland has a duct that opens into the digestive tract or to the outside of the body. some glands have both an endocrine and exocrine function.

Molecules that function as hormones must exhibit two basic characteristics

first they must be sufficiently complex to convey regulatory information to their targets. second, hormones must be adequately stable to resist destruction prior to reaching their target cells.

posterior pituitary

forms from brain tissue. functions differently. produces Antidiuretic hormone (ADH) and oxytocin.

lipophilic hormones

non-polar and are fat soluble. includes the steroid hormones and thyroid hormones. most other hormones are hydrophilic. There lipid solubility allows them to cross cell membranes and bind to intracellular receptors. Lipophilic hormones travel in the blood attached to transport proteins. includes the steroid hormones as well as the amino acid derivatives, produced by the thyroid. lipophilic hormones tend to persist for longer periods of time before being destroyed.

The pituitary is a compound endocrine gland

the gland consists of two parts, one of which appears glandular and is called the anterior pituitary. the anterior pituitary developes from epithelial tissue from the roof of the embryo's mouth. NOT PART OF THE NERVOUS SYSTEM despite being in contact with the brain. the other portion appears fibrous and is called the posterior pituitary. these two portions of the pituitary gland have different embryonic origins, secrete different hormones, and are regulated by different control systems.

inhibitors

the hypothalamus also secretes neurohormones that inhibit the release of certain anterior-pituitary hormones.

Feedback from peripheral endocrine glands regulates anterior-pituitary hormones

the hypothalamus and the anterior pituitary are themselves partially controlled by the very hormones whose secretion they stimulate.

hypothalamic neurohormones regulate the anterior pituitary

the hypothalamus controls the production and secretion of the anterior pituitary's hormones. Neurons in the hypothalamus secrete two types of neurohormones, releasing hormones and inhibiting hormones.

The pituitary gland and hypothalamus: the body's control centers

the pituitary gland hangs by a stalk from the hypothalamus at the base of the brain posterior to the optic chiasm.

Horomones of the anterior pituitary work directly and indirectly

the pituitary gland was taken out of subjects in the early 20th century. these patients had reduced growth and development, diminished metabolism, and failure of reproduction.

insulin

the sole factor responsible for moving glucose from the blood into cells. diabetes results when there is a problem with insulin. type 1 lack insulin secreting cells. type 2 adult onset diabetes. the body cells are less sensitive to insulin than they should be. due to lifestyle factors, poor diet.

calcitonin secretion by the thyroid

the thyroid gland also secretes calcitonin, a peptide hormone that plays a role in maintaining proper levels of calcium in the blood. When the blood Calcium concentration rises too high, calcitonin stimulates the uptake of calcium into bones, thus lowering its level in the blood.

hydrophilic hormones

water-soluble. can travel un aided through the blood stream, because they water soluble. they cannot pass through the cell membrane of their target cells. the receptors for hydrophilic hormones are on the outside of the target cell membrane. brief time of action then are destroyed quickly. can't pass into the cell. they bind to receptors that are imbedded in the membrane. cause changes in protein structure that activate or deactivate the proteins inside the cell. they can activate protein kinases which activate or deactivate proteins by phosphoralation.