Bio102 chpt 45 endocrine system

what happens in endocrine signaling

In endocrine signaling, hormones secreted into extracellular fluid by endocrine cells reach target cells via the bloodstream (or hemolymph)

feedback regulation

the regulation of a process by its output or end product (often involves negative feedback and positive feedback)

what happens in a simple neuroendocrine pathway

the stimulus is received by a sensory neuron rather than endocrine tissue. The sensory neuron in turn stimulates a neurosecretory cell. In response, the neurosecretory cell secretes a neurohormone. Like other hormones, the neurohormone diffuses into the bloodstream and travels in the circulation to target cells. As an example of a simple neuroendocrine pathway, consider the regulation of milk release during nursing in mammals When an infant suckles, it stimulates sensory neurons in the nipples, generating nerve impulses that reach the hypothalamus. This input triggers the secre- tion of the neurohormone oxytocin from the posterior pitu- itary gland. Oxytocin then causes contraction of mammary gland cells, forcing milk from reservoirs in the gland.

why does the stomach contain isolated endocrine cells

the stomach contains isolated endocrine cells that help regulate digestive processes by secreting the hormone gastrin.

signal transduction

- The chain of events that converts the extracellular chemi- cal signal to a specific intracellular response - The linkage of a mechanical, chemical, or electromagnetic stimulus to a specific cellular response.

Nitric oxide (NO)

-A gas produced by many types of cells that functions as a local regulator and as a neurotransmitter.

pheromones

-chemicals that are released into the external environment -In animals and fungi, a small molecule released into the environment that functions in communication between members of the same species. In animals, it acts much like a hormone in influencing physiology and behavior.

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steps for the Regulation of insect development and metamorphosis.

1) Neurosecretory cells in the brain produce prothoracicotropic hormone (PTTH), which is stored in the corpora cardiaca until release 2) PTTH signals its main target organ, the prothoracic gland, to produce the hormone ecdysteroid. 3) Ecdysteroid secretion from the prothoracic gland is episodic, with each release stimulating a molt 4) Juvenilehormone(JH),secretedby the corpora allata, determines the result of the molt. At relatively high concentrations, JH suppresses metamorphosis. Under these conditions, molting stimulated by ecdysteroid produces another larval stage. When JH drops below a certain concentration, a pupa forms at the next ecdysteroid-induced molt. The adult insect emerges from the pupa.

diff btw Water-soluble and lipid-soluble hormones in their response to pathways

1) One key difference is the location of the receptor proteins in target cells. Water-soluble hormones are secreted by exocytosis and travel freely in the bloodstream. Being insoluble in lipids, they cannot diffuse through the plasma membranes of target cells. Instead, these hormones bind to cell-surface receptors, inducing changes in cytoplasmic molecules and sometimes altering gene transcription In contrast, lipid-soluble hormones exit endocrine cells by diffusing out across the membranes. They then bind to transport proteins, which keep them soluble in blood. After circulating in the blood, they diffuse into tar- get cells and typically bind to receptors in the cytoplasm or nucleus The hormone-bound receptor then triggers changes in gene transcription.

Hormones fall into what three major chemical classes:

1) polypeptides, 2) steroids, and 3) amines

Communication between animal cells via secreted signals is often classified by two criteria:

1) the type of secreting cell and 2) the route taken by the signal in reaching its target

endocrine glands

A ductless gland that secretes hormones directly into the interstitial fluid, from which they diffuse into the bloodstream.

negative feedback

A form of regulation in which accumulation of an end product of a process slows the process; in physiology, a primary mechanism of homeostasis, whereby a change in a variable triggers a response that counteracts the initial change. - feedback in which the response reduces the initial stimulus.

positive feedback

A form of regulation in which an end product of a process speeds up that process; in physiology, a control mechanism in which a change in a variable triggers a response that reinforces or amplifies the change. - Whereas negative feedback dampens a stimulus, positive feedback reinforces a stimulus, leading to an even greater response.

how can A hormone can elicit distinct responses in particular target cells

A hormone can elicit distinct responses in particular target cells if those cells differ in receptor type or in the molecules that produce the response. In this way a single hormone can trigger a range of activities that together bring about a coordinated response to a stimulus.

oxytocin

A hormone produced by the hypothalamus and released from the posterior pituitary. It induces contractions of the uterine muscles during labor and causes the mammary glands to eject milk during nursing.

insulin

A hormone produced by the pancreas or taken as a medication by many diabetics -is a polypeptide that contains two chains in its active form.

neurotransmitters

A molecule that is released from the synaptic terminal of a neuron at a chemical synapse, diffuses across the synaptic cleft, and binds to the postsynaptic cell, trig- gering a response.

neurohormone

A molecule that is secreted by a neuron, travels in body fluids, and acts on specific target cells, changing their functioning. this happens in neuroendocrine signaling Many neurohormones regulate endocrine signaling

local regulators,

A secreted (many cells produce and secrete it) molecule that influences cells near where it is secreted. -molecules that act over short distances, reach their target cells solely by diffusion, and act on their target cells within seconds or even milliseconds

Testes (in males)

Androgens*: Support sperm formation; promote development and maintenance of male secondary sex characteristics

what kinds of molecules are secreted at most synapses

At most synapses, neurons secrete molecules called neurotransmitters that diffuse a very short distance (a fraction of a cell diameter) and bind to receptors on the target cells (

how does negative feedback prevent excessive pathway activity.

By decreasing hormone signaling, negative- feedback regulation prevents excessive pathway activity.

what is the function of the endocrine system

Chemical signaling by hormones is the function of the endocrine system

two types of signaling by local regulators

Depending on the target cell, signaling by local regulators can be either paracrine or autocrine.

what is the purpose of drugs that block prostaglandin synthesis, such as aspirin and ibuprofen,

Drugs that block prostaglandin synthesis, such as aspirin and ibuprofen, prevent these activities, producing both anti-inflammatory and pain-relieving effects.

A simple endocrine pathway.

Endocrine cells respond to a change in some internal or external variable—the stimulus— by secreting hormone molecules that trigger a specific response by target cells. In the case of secretin signaling, the simple endocrine pathwayis self-limiting because the response to secretin (bicarbonate release) reduces the stimulus (low pH) through negative feedback.

what happens with target cells in autocrine signaling

In autocrine signaling (from the Greek auto, self), the secreting cells themselves are the target cells

Adrenal glands (atop kidneys) Adrenal medulla

Epinephrine and norepinephrine: Raise blood glucose level; increase metabolic activity; constrict or dilate blood vessels

Ovaries (in females)

Estrogens*: Stimulate uterine lining growth; promote development and maintenance of female secondary sex characteristics Progesterone*: Promotes uterine lining growth

Anterior pituitary

Follicle-stimulating hormone (FSH) and luteinizing hormone (LH): Stimulate ovaries and testesThyroid-stimulating hormone (TSH): Stimulates thyroid gland Adrenocorticotropic hormone (ACTH): Stimulates adrenal cortex Prolactin: Stimulates mammary gland growth and milk synthesis in mammals Growth hormone (GH): Stimulates growth and metabolic functions Melanocyte-stimulating hormone (MSH): Affects color of melanocytes, a type of skin cell

example of positive feedback

For example, in the oxytocin pathway, the mammary glands secrete milk in response to circulating oxytocin. The released milk in turn leads to more suckling and therefore more stimulation. Activation of the pathway is sustained until the baby stops suckling. Other functions of oxytocin, such as stimulating contractions of the uterus during birthing, also exhibit positive feedback.

example of negative feedback

For instance, bicarbonate released in response to secretin increases pH in the intestine, eliminat- ing the stimulus and thereby shutting off secretin release

Adrenal cortex

Glucocorticoids: Raise bloodglucose levelMineralocorticoids: Promote reabsorption of Na+ and excretion of K+ in kidneys

For suggested answers, see Appendix A. Hypothalamus

Hormones released fromposterior pituitary (see below) Releasing and inhibiting hormones: Regulate anterior pituitary

hormones do what

In animals, hormones are secreted into the extracellular fluid, circulate in the blood (or hemolymph), and communicate regulatory messages throughout the body.

nervous system,

In animals, the fast-acting internal system of communication involving sensory receptors, networks of nerve cells, and connections to muscles and glands that respond to nerve signals; functions in concert with the endocrine system to effect internal regulation and maintain homeostasis. a network of specialized cells—neurons—that transmit sig- nals along dedicated pathways--> These signals in turn regulate neurons, muscle cells, and endocrine cells. Because signaling by neurons can regulate the release of hormones, the nervous and endocrine systems often overlap in function.

endocrine system

In animals, the internal system of communication involving hormones, the ductless glands that secrete hormones, and the molecular receptors on or in target cells that respond to hormones; functions in concert with the nervous system to effect internal regulation and maintain homeostasis.

how does nitric oxide affect human males

In human males, NO's ability to promote vasodilation enables sexual function by increasing blood flow into the penis, producing an erection. -The drug Viagra (sildenafil citrate), a treatment for male erectile dysfunction, sustains an erection by prolonging activity of the NO response pathway.

hormones

In multicellular organisms, one of many types of secreted chemicals that are formed in specialized cells, travel in body fluids, and act on specific target cells in other parts of the organism, changing the target cells' functioning.

What do neurosecretory cells do?

In neuroendocrine signaling, neurons called neurosecretory cells secrete neurohormones, which diffuse from nerve cell endings into the bloodstream

prostaglandins do what

In the immune system, for example, prostaglandins promote inflammation and the sensation of pain in response to injury. -Prostaglandins also help regulate the aggregation of plate- lets, one step in the formation of blood clots. Because blood clots in vessels that supply the heart can block blood flow, causing a heart attack some physicians recommend that people at risk for a heart attack take aspirin on a regular basis.

Pancreas

Insulin: Lowers blood glucose level Glucagon: Raises blood glucose level

for lipid-soluble hormones, what performs the entire task of transducing a signal within a target cell.

Intracellular receptors -The hormone activates the receptor, which then directly triggers the cell's response.

Where are endocrine cells located?

Islets of Langerhans?? Some endocrine cells are found in organs that are part of other organ systems. i.e stomach , endocrine glands such as the thyroid and parathyroid glands and the gonads, either testes in males or ovaries in females

how do Local regulators play roles in many physiological processes

Local regulators play roles in many physiological processes, including blood pressure regulation, nervous system function, and reproduction.

Pineal gland

Melatonin: Participates in regulation of biological rhythms

what triggers molting in moths

Neurosecretory cells in the brain produce PTTH, a polypep- tide neurohormone. When PTTH reaches an endocrine organ called the prothoracic gland, it directs release of a second hormone, ecdysteroid. Bursts of ecdysteroid trigger each successive molt.

Nitric oxide (NO), a gas, functions in the body as a what

Nitric oxide (NO), a gas, functions in the body as both a local regulator and a neurotransmitter.

antidiuretic hormone

One example of a neurohormone -functions in kidney function and water balance as well as courtship behavior. Many neurohormones regulate endocrine signaling

prostaglandins

One group of local regulators with diverse and widespread functions are the prostaglandins. -One of a group of modified fatty acids that are secreted by virtually all tissues and that perform a wide variety of functions as local regulators.

pituitary gland Posterior pituitary

Oxytocin: Stimulates contraction of uterus and mammary gland cells Vasopressin, also called antidiuretic hormone (ADH): Promotes retention of water by kidneys; influences social behavior and bonding

Parathyroid glands

Parathyroid hormone (PTH): Raises blood calcium level

what molecule are prostaglandins

Prostaglandins are modified fatty acids

Classes of Local Regulators

Prostaglandins are modified fatty acids. Many other local regulators are polypeptides, including cytokines, which enable immune cell communication and growth factors, which promote cell growth, division, and development. Some local regulators are gases.

paracrine

Referring to a secreted molecule that acts on a neighboring cell.

autocrine

Referring to a secreted molecule that acts on the cell that secreted it.

A simple neuroendocrine pathway

Sensory neurons respond to a stimulus by sending nerve impulses to a neurose- cretory cell, triggering secretion of a neurohormone. Upon reaching its target cells, the neurohormone binds to its receptor, triggering a specific response. In oxytocin signaling, the response increases the stimulus, forming a positive-feedback loop that amplifies signaling.

structure of Steroid hormones

Steroid hormones, such as cortisol, are lipids that contain four fused carbon rings; all are derived from the steroid cholesterol

why do all secreted signaling molecules act within the body.

THEY DONT!!!!!! pheromones for example help Members of a particular animal species sometimes commu- nicate with each other

how do endocrine cells affect the duodenum

The activity of endocrine cells in the duodenum, the first part of the small intestine, provides a useful example of a simple endocrine pathway. During digestion, the partially processed food that enters the duodenum contains highly acidic digestive juices secreted by the stomach. Before further digestion can occur, this acidic mixture must be neutralized. - The low pH of partially digested food entering the small intestine is detected by S cells, which are endocrine cells in the lining of the duodenum. In response, the S cells secrete the hormone secretin, which diffuses into the blood. Traveling throughout the circulatory system, secretin reaches the pancreas. Target cells in the pancreas have receptors for secretin and respond by releasing bicarbonate into ducts that lead to the duodenum. In the last step of the pathway, the bicarbon- ate released into the duodenum raises the pH, neutralizing the stomach acid.

how does the Y chromosome of a male lead to. male size, shape, and behavior

The answer to this and many other questions about biological processes involves signaling molecules called hormones

what kind of cellular response does The binding of a water-soluble hormone to a cell-surface receptor protein trigger

The response may be the activation of an enzyme, a change in the uptake or secretion of specific molecules, or a rearrangement of the cytoskeleton - In some cases, cell-surface receptors cause proteins in the cytoplasm to move into the nucleus and alter the transcription of specific genes.

what happens once Binding of a steroid hormone to its cytosolic receptor forms a complex that moves into the nucleus

There, the receptor portion of the complex alters transcription of particular genes by interacting with a specific DNA-binding protein or response element in the DNA. (In some cell types, steroid hormones trigger additional responses by interacting with other kinds of receptor proteins located at the cell surface).

Thyroid gland

Thyroid hormone ( T3 and T4 ): Stimulates and maintains metabolic processes Calcitonin: Lowers blood calcium level

hormones that are not steroids typically have receptors where

Thyroxine, vitamin D, and other lipid-soluble hormones that are not steroids typically have receptors in the nucleus.

how does nitric oxide function as a local regulator and a neurotransmitter

When the level of oxygen in the blood falls, endothelial cells in blood vessel walls synthesize and release NO. After diffusing into the sur- rounding smooth muscle cells, NO activates an enzyme that relaxes the cells. The result is vasodilation, which increases blood flow to tissues.

In most cases, the response to a lipid-soluble hormone is what

a change in gene expression.

Binding of a steroid hormone to its cytosolic receptor forms what

a complex that moves into the nucleus

Water-soluble hormones are secreted how

by exocytosis and travel freely in the bloodstream.

are hormones polar or nonpolar

can be either - hormones vary in their solubility in aqueous and lipid-rich environments. Polypeptides and most amine hormones are water-soluble, whereas steroid hor- mones and other largely nonpolar (hydrophobic) hormones, such as thyroxine, are lipid-soluble.

endocrine glands secrete hormones to where

directly into the surrounding fluid

what are the 2 basic systems for communication and regulation in the animal body.

endocrine and nervous system

what happens in a simple endocrine pathway

endocrine cells respond directly to an internal or environmental stimulus by secreting a particular hormone. The hormone travels in the bloodstream to target cells, where it interacts with its specific receptors. Signal trans- duction within target cells brings about a physiological response.

tissues with ducts secrete what

enzymes and bicarbonate.

exocrine glands

gland that releases its secretions through tubelike structures called ducts

secrete hormones to where

have ducts that carry secreted substances, such as sweat or saliva, onto body surfaces or into body cavities

Ductless tissues secrete what

hormones

Most steroid hormone receptors are located where

in the cytosol prior to binding to a hormone.

In the case of the pancreas, endocrine and exocrine tissues are found where

in the same gland: Ductless tissues secrete hormones, whereas tissues with ducts secrete enzymes and bicarbonate.

In animals, hormones are secreted into what part of the body

into the extracellular fluid, circulate in the blood (or hemolymph)

lipid-soluble hormones are secreted how?

lipid-soluble hormones exit endocrine cells by diffusing out across the membranes. They then bind to transport proteins, which keep them soluble in blood. After circulating in the blood, they diffuse into tar- get cells and typically bind to receptors in the cytoplasm or nucleus The hormone-bound receptor then triggers changes in gene transcription.

functions of endocrine signaling

maintain homeostasis. - Hormones regulate properties that include blood pressure and volume, energy metabolism and allocation, and solute concentrations in body fluids. Endocrine signaling also mediates responses to environmental stimuli, regulates growth and development, and, as discussed above, triggers physical and behavioral changes underlying sexual maturity and reproduction.

functions of pheromones

marking trails leading to food, defining territories, warning of predators, and attracting potential mates -

are synthesized from

monomers by dehydration reactions. - Epinephrine and thy- roxine are amine hormones, each synthesized from a single amino acid, either tyrosine or tryptophan.

hormone pathways involved in homeostasis typically exhibit what kind of feedback

negative feedback -Often such pathways are paired, providing even more balanced control. For example, blood glucose levels are regulated by the opposing effects of insulin and glucagon

how does neuroendocrine signaling work

neurohormones diffuse into the bloodstream and trigger responses in target cells anywhere in the body.

how does synaptic signaling work

neurotransmitters diffuse across synapses and trigger responses in cells of target tissues (neurons, muscles, or glands).

In vertebrates, coordination of endocrine signaling relies heavily on what

on the hypothalamus

which kind of feedback helps restore a preexisting state

only negative feedback helps restore a preexisting state.

hypothalamus does what

receives information from nerves throughout the body and, in response, initiates neuroendocrine signaling appropriate to environmental conditions.

how does endocrine signaling work

secreted molecules diffuse into the blood- stream and trigger responses in target cells anywhere in the body.

how does autocrine signaling work

secreted molecules diffuse locally and trigger a response in the cells that secrete them.

how does paracrine signaling work

secreted molecules diffuse locally and trigger a response in neighboring cells.

synaptic signaling is imp for what bodily functions

sensation, memory, cognition, and movement

Estrogen is what kind of hormone?

steroid hormone - Among the best-characterized steroid hormone receptors are those that bind to estrogens, steroid hormones neces- sary for female reproductive function in vertebrates. For example, in female birds and frogs, estradiol, a form of estro- gen, binds to a cytoplasmic receptor in liver cells. Binding of estradiol to this receptor activates transcription of the vitellogenin gene (Figure 45.7). Following translation of the messenger RNA, vitellogenin protein is secreted and trans- ported in the blood to the reproductive system, where it is used to produce egg yolk.

examples of endocrine glands

such as the thyroid and parathyroid glands and the gonads, either testes in males or ovaries in females

what happens with target cells in paracrine signaling

target cells lie near the secreting cell

hormones that are steroids typically have receptors where

the cytosol

duodenum

the first part of the small intestine

how do hormones that are not steroids function

they bind to receptors in the nucleus These receptors bind to hormone molecules that diffuse from the bloodstream across both the plasma membrane and nuclear envelope. Once bound to a hormone, the recep- tor binds to specific sites in the cell's DNA and stimulates the transcription of specific genes.

how do Neurons communicate with target cells, suchas other neurons and muscle cells

via specialized junctions called synapses.

when seals, humans, and other mammals are stressed, are dehydrated, or have low blood sugar levels, how do hormones respond to this

when seals, humans, and other mammals are stressed, are dehydrated, or have low blood sugar levels, hormones coordinate the physiological responses that restore balance in our bodies.

Are hormones specific?

yes each hormone binds to specific receptors in the body. Although a given hormone can reach all cells of the body, only some cells have receptors for that hormone. A hormone elicits a response—such as a change in metabolism—in specific target cells, those that have the matching receptor. Cells lacking a receptor for that hormone are unaffected.