Chapter 45 (1)

A caterpillar's complete change of body form, called __ is one of many biological processes controlled by hormones.
- In animals, a __ is a molecule that is secreted into the extracellular fluid, circulates in the blood or hemolymph, and communicates regulatory messages throughout the body.

Although teh circulatory system allows a hormone to reach all cells of the body, only its __ cells have receptors that enable a response.
- A hormone elicits a specific response from its __ cells, whereas cells lacking a receptor for that particular hormone are unaffected.

Chemical signaling by hormones is the function of the __, one of the two basic systems for communication and regulation throughout the body. Hormones secreted by these ccells regulate reproduction, development, energy metabolism, growth and behavior.

The other major communication and control system is teh __, a network of specialized cells-neurons- that transmit signals along dedicated pathways. These signals in turn regulate other cells, including 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.

Hormone ssecreted into extracellular fluids by endocrine cells reach target cells via the __. Some endocrine system cells are found in organs that are part of other organ systems.
- Other endocrine cells are grouped in ductless organs called __.

Like isolated endocrine cells, __ secrete hormones directly into the surrounding fluid. __ thus contrast with __, such as salivary glands, which have ducts that carry secreted substances onto body surfaces or into body cavities.
The Greek __ (within) and __ (out of) reflect secretion into or out of body fluids, while __ (seperate) reflects movement away from the secreting cell.

Hormones serve a range of functions in the body. They maintain __; mediate responses to environmental stimuli; and regulate growth, development, and reproduction. They also control appearances of characteristics that distinguish a juvenile from an adult.

Many types of cells produce __, secreted molecules that act over short distances and reach their target cells solely by diffusion.

Local regulators function in __ and __ signaling.
o In __, target cells lie near the secreting cell.
o In __, the secreted molecules act on the secreting cell itself.

SOme secreted molecules have both __ and __ activity. Although the definition of hormones can be broadened to include lcoal regulators, we use hormones to refer to chemicals that reach target cells through the bloodstream.

Secreted molecules also have a critical role in the transmission of info by neurons. Neurons communicate with target cells, like neurons and musc cle cells, at specialized junctions known as __.

At many __, neurons secrete molecules called __ that diffuse a very short distance to bind receptors on the target cell. __ are central to sensation, memory, cognition and mvement.

In __, __, specialized neurons typiccally found in the brain, secrete moleculess that diffuse from nerve cell endings into the bloodstream. These molecules, which travel through the bloodstream to reach target cells, are a class of hormones called __.

Not all secreted signaling molecules act w/in the body. Members of the same animal species sometimes communicate with __, chems that are released into the external environment. __ serve many functions, like marking trails leading to food, defining territories, warning predators, and attracting potential mates.

Based on hormone's structure and pathway for synthesis, hormones are divided into three groups: __, __, and __.

the polypeptide hormone __ is made up of two polypeptide chains. Like most hormones in this group, __ is formed by cleavage of a longer protein chain.

Epinephrine and thyroxine are__ hormones, which are synthesized from a single amino acid, eithre tyrosine or tryptophan.

__ hromones, like cortisol, are lipids that contain four fused carbon rings. All are derived from the steroid __.

Hormones vary in their solubility in aqueous and lipid-rich environments.
o Which are water-soluble?
- Being insoluble in lipids, these hormones cannot pass through the plasma membranes of cells.
o Which are lipid-soluble?
- They can pass through cell membranes readily.

In frogs, __ controls the location of pigment granules in skin cells.

Receptor location is one of several difference sbetween the response pathways for water soluble and lipid-soluble hormones.
o __hormones are secreted by __, travel freely in the bloodstream, and bind to cell-surface signal receptors. Binding of such hormones to receptors induces changes in cytoplasmic moleucles and sometimes alters __ (synthesis of mRNA molecules.)

In contrast, __ hormones diffuse out across the membranes of endocrine cells and travel in the bloodstream bound to transport proteins. Upon diffusing into target cells, they bind to intracellular signal receptors and trigger changes in __.

The binding of a __ hormone to a signal receptor protein triggers events at the plasma membrane that result in a cell response. 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.

True or Flase:
In addition, some cell surace receptors cause proteins in the cytoplasm to move into the nucleus and alter transcription of specific genes.
True False

The series of changes in cell proteins that converts the extracellular chemical signal to a specific intracellular response is called __. A __ typically invlolves multiple steps, each involving specific molecular interactions.

When in a stressful situation, your __ glands secrete __. When this hormone reaches liver cells, it binds to a __ in the plasma membrane. The binding of hormone to receptor triggers a cascade of events involving synthesis of __ as a short-lived __. Activation of __ by __ leads to activation of an enzyme required for glycogen breakdown and inactivation of an enzyme necessary for __ synthesis. The net result is that the liver releases __ into the bloodstream, providing the fuel you need to chase the bus.

__ usually peform the entire task of transducing a signal within a target cell. The hormone activates the receptor, which then directly triggers the cell's response. In most cases, the response to a lipid-soluble hormone as a change in __.

__ hormone receptors are located in the cytosol prior to binding to a hormone. When a __ hormone binds to a cytosolic receptor, a hormone-receptor complex forms, which moves into the nucleus. There, the receptor portion of the complex interacts with DNA or with a DA-binding protein, stimulating __ of specific genes.

__ has a specific receptor in the liver cells of female birds and frogs. Binding of __ to this receptor activates transcription of teh gene for the protein __. Following translation of the mRNA, __ is secreted and transported in the blood to the reproductive system, where it is used to produce egg yolk.

__, __ and othe rlipid- soluble hormones that are not steroid hormones have receptors that are typically located in the nucleus. These receptors bind hormone molecules that diffuse from the bloodstream across both the plasma membrane and nuclear envelope. Once bound by a hormone, the receptor binds to specific sites in the cell's DNA and stimulates the transcription of specific genes.

True or False:
Many hormones elicit more than one type of response in the body. The effects brought about by a particular hormone can vary if target cells differ in the molecuels that receive or produce the response to that hormone.
True False

Consider epinephrine. How does it elicit different responses?
__ vary in their resposne to epinephrine because they vary in their receptors or __. Target cell recognition of epineprhine involves __.

The epinephrine reeptor of a liver cell is called a __ type receptor. It acts through __ to regulate enzymes in glycogen metabolism. In blood vessels supplying skeletal muscle, the same kinase activated by the same epinephrine receptor inactivates a muscle-specific enzyme. The result is smooth muscle relaxation and hence increased blood flow.

In contrast, intestinal blood vessels express an __- type epinephrine receptor. Rather than activate __, the __ receptor triggers a distinct signaling pathway involving a different __ and different enzymes. The result is smooth muscle contraction and restricted blood flow.

__ hormones often exert different effects on different target cells as well.
- In some cases, a given hormone has different effects in diffferent __.
- For ex., __ produced by the thyroid gland regulates metabolism in frogs, humans, etc. However, it has an additional and distinct effect in frogs, stimulating resorption of the tadpole's tail in its metamorphosis into an adult.

Recall that local regulators are secreted molecules that link neighboring cells (__) or that provide feedback to the secreting cell (__). Once secreted, __ act on their target cells within seconds or even milliseconds, eliciting responses more quickly than do hormones. Nevertheless, the pathways by which local regulators trigger responses are the same as those activated by hormones.

Several types of chemical compounds function as local regulators. Polypeptide local regulators include __, which play a role in immune responses and most __, which stimulate cell proliferation and idfferentiation. Many types of cells grow, divide and develop normally only when growth factors are present in their extracellular environment.

The gas __, which consists of nitrogen double-bonded to oxygen, serves in the body as both a __ and a __.
o When the level of oxygen in the blood fals, endothelial cells in the blood vessel walls synthesize and release __. __ activates an enzyme that relaxes the neighboring smooth muscle clels, resulting in __, which improves blood flow to tissues.

A group of local regulators called __ are modified fatty acids. __ are produced by many cell types and have varied activities. In semen that reaches the reproductinve tract of a female, __ stimulate the smooth muscles of the female's uterine wall to contract, helping sperm reach an egg. At the onset of childbirth, __- secreting cells of the placenta cause the nearby muscles of the uterus to become more excitable, helping to induce labor.

In the immune system, __ promote fever and inflammationa dn also intensify the sensation of pain. The anti-inflammatory and pain-relieving effects of aspirin and ibuprofen are due to the inhibiton of __ sythesis by these drugs.

__ also help reegulate the aggregation of platelets, one step in the formation of blood clots. Although docs recomment it, __ helps maintain a protective lining in the stomach, so long-term aspirin therapy can cause debilitating stomach irritation.