Animal Communication: Pheromones and Hormones

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Questions and Answers

What is the main function of pheromones in animal species?

To respond to hormonal signals

To regulate growth and development

To communicate with other members of the same species (correct)

To defend against predators directly

Which of the following is NOT a major chemical class of hormones?

Amines

Steroids

Nucleic acids (correct)

Polypeptides

How do lipid-soluble hormones travel in the bloodstream?

Through the process of endocytosis

Free in the bloodstream

In exocytotic vesicles

Bound to transport proteins (correct)

Where do lipid-soluble hormones bind to receptors?

In the nucleus of target cells Signup and view all the answers

What is the term for the chain of events that converts a hormone signal to an intracellular response?

Signal transduction Signup and view all the answers

What is a possible response to hormone binding in target cells?

Changes in gene transcription Signup and view all the answers

How do water-soluble hormones travel in the bloodstream?

Free in the bloodstream Signup and view all the answers

Where do water-soluble hormones bind to receptors?

On the surface of target cells Signup and view all the answers

What is a characteristic feature of endocrine glands?

They are often grouped together in ductless organs Signup and view all the answers

What is the role of secretin in the duodenum?

To decrease the acidity of the duodenum Signup and view all the answers

What determines the different effects of a hormone on target cells?

The type of hormone receptor present on the target cells Signup and view all the answers

What is a characteristic of simple endocrine pathways?

Endocrine cells respond directly to a stimulus by secreting a hormone Signup and view all the answers

What is the difference between endocrine and exocrine glands?

Endocrine glands secrete hormones into the bloodstream, while exocrine glands secrete substances onto body surfaces Signup and view all the answers

What is the role of the pancreas in the duodenum?

It secretes bicarbonate into the duodenum Signup and view all the answers

What is a characteristic of hormone pathways?

They involve feedback regulation and coordination with the nervous system Signup and view all the answers

What is the 'fight-or-flight' response?

A rapid response to stress mediated by epinephrine Signup and view all the answers

What is the function of the hypothalamus in endocrine signaling?

To initiate appropriate neuroendocrine signals in response to nerve information Signup and view all the answers

What is the role of the posterior pituitary?

To store and secrete hormones made in the hypothalamus Signup and view all the answers

Which hormone regulates physiology and behavior?

Antidiuretic hormone (ADH) Signup and view all the answers

What is the role of the anterior pituitary hormones in hormone cascades?

To control the release of hormones by target endocrine glands Signup and view all the answers

What is the function of prolactin-releasing hormone from the hypothalamus?

To stimulate the anterior pituitary to secrete prolactin Signup and view all the answers

Which of the following is an example of a hormone cascade?

Sets of hormones from the hypothalamus, anterior pituitary, and a target endocrine gland Signup and view all the answers

What is the role of oxytocin?

To regulate milk secretion by the mammary glands Signup and view all the answers

What is the relationship between the hypothalamus and the pituitary gland?

The hypothalamus regulates the pituitary gland Signup and view all the answers

What is the primary function of a neurosecretory cell in a simple neuroendocrine pathway?

To secrete a neurohormone into the bloodstream Signup and view all the answers

What is the response to the initial stimulus in a negative feedback loop?

A decrease in the stimulus Signup and view all the answers

What is the role of oxytocin in the example of a simple neuroendocrine pathway?

To cause the release of milk from the mammary glands Signup and view all the answers

What is the primary function of the endocrine organs in the brain?

To integrate the function of the endocrine system with the nervous system Signup and view all the answers

What triggers the release of ecdysteroid in the prothoracic gland?

The release of PTTH from the larval brain Signup and view all the answers

What is the response to the release of oxytocin in mammals?

An increase in suckling by offspring, leading to more oxytocin release Signup and view all the answers

What is required for metamorphosis to occur in invertebrates?

A decrease in JH levels and an increase in ecdysteroid Signup and view all the answers

What is the primary function of PTTH in invertebrates?

To direct the release of ecdysteroid in the prothoracic gland Signup and view all the answers

What is the response of the hypothalamus when thyroid hormone levels drop in the blood?

It releases thyrotropin-releasing hormone (TRH) Signup and view all the answers

What is the result of low levels of thyroid hormone due to insufficient iodine?

The pituitary continues to secrete TSH, causing the thyroid to enlarge Signup and view all the answers

What is the primary function of growth hormone (GH) in the body?

Stimulating bone and cartilage growth Signup and view all the answers

What is the consequence of an excess of growth hormone (GH) in the body?

Gigantism Signup and view all the answers

What is the primary function of parathyroid hormone (PTH) in the body?

Controlling blood calcium levels Signup and view all the answers

What is the result of the hypothalamus secreting thyrotropin-releasing hormone (TRH)?

The anterior pituitary releases TSH Signup and view all the answers

What is the only iodine-containing molecule synthesized in the body?

Thyroid hormone Signup and view all the answers

What is the consequence of a lack of growth hormone (GH) in the body?

Dwarfism Signup and view all the answers

Study Notes

Signaling by Pheromones

Pheromones are chemicals released into the environment by some animal species to communicate with each other.
Pheromones serve various functions, including:
- Marking trails leading to food
- Defining territories
- Warning of predators
- Attracting potential mates

Hormone Chemical Classes

Hormones can be classified into three major chemical classes:
- Polypeptides
- Steroids
- Amines
Polypeptides and most amines are water-soluble, while steroid hormones and other non-polar hormones are lipid-soluble.

Cellular Hormone Response Pathways

Water-soluble hormones are secreted by exocytosis, travel freely in the bloodstream, and bind to cell-surface receptors.
Lipid-soluble hormones diffuse across cell membranes, travel in the bloodstream bound to transport proteins, and diffuse through the membrane of target cells.
They bind to receptors in the cytoplasm or nucleus of the target cells.

Response Pathway for Water-Soluble Hormones

Binding of a hormone to its receptor initiates a cellular response.
The response may be:
- Activation of an enzyme
- Change in uptake or secretion of certain molecules
- Rearrangement of the cytoskeleton
- Initiation of changes in transcription of certain genes
Signal transduction is the process by which the chemical signal is converted to an intracellular response.

Multiple Responses to a Single Hormone

The same hormone can have different effects on target cells that have:
- Different receptors for the hormone
- Different signal transduction pathways
For example, the hormone epinephrine has multiple effects that form the basis of the “fight-or-flight” response.

Endocrine Tissues and Organs

Endocrine cells are often grouped in ductless organs called endocrine glands, such as:
- Thyroid and parathyroid glands
- Testes or ovaries
In contrast, exocrine glands, such as salivary glands, have ducts to carry secreted substances onto body surfaces or into body cavities.

Feedback Regulation and Coordination with the Nervous System

Hormones are assembled into regulatory pathways that involve feedback regulation and coordination with the nervous system.
In a simple endocrine pathway, endocrine cells respond directly to a stimulus by secreting a particular hormone.
The hormone travels in the bloodstream to target cells, where it interacts with its specific receptors, and signal transduction within target cells brings about a physiological response.

Simple Neuroendocrine Pathways

In a simple neuroendocrine pathway, the stimulus is received by a sensory neuron, which stimulates a neurosecretory cell.
The neurosecretory cell secretes a neurohormone, which enters the bloodstream and travels to target cells.

Feedback Regulation

In a negative feedback loop, the response reduces the initial stimulus.
For example, the increase in pH in the intestine caused by secretin release shuts off further secretin release.
Positive feedback reinforces a stimulus to produce an even greater response.
For example, in mammals, oxytocin causes the release of milk, causing greater suckling by offspring, which stimulates the release of more oxytocin.

Coordination of Endocrine and Nervous Systems

In a wide range of animals, endocrine organs in the brain integrate the function of the endocrine system with that of the nervous system.
The hypothalamus coordinates endocrine signaling, receives information from nerves throughout the body, and initiates appropriate neuroendocrine signals.
Signals from the hypothalamus travel to the pituitary gland, composed of the posterior pituitary and anterior pituitary.

Posterior Pituitary Hormones

Neurosecretory cells of the hypothalamus synthesize the two posterior pituitary hormones:
- Antidiuretic hormone (ADH) regulates physiology and behavior
- Oxytocin regulates milk secretion by the mammary glands

Anterior Pituitary Hormones

The anterior pituitary controls diverse processes, such as metabolism, osmoregulation, and reproduction.
Hormones secreted by the hypothalamus control the release of all anterior pituitary hormones.
For example, prolactin-releasing hormone from the hypothalamus stimulates the anterior pituitary to secrete prolactin (PRL), which has a role in milk production.

Hormone Cascades

Sets of hormones from the hypothalamus, anterior pituitary, and a target endocrine gland are often organized into a hormone cascade.
The anterior pituitary hormones in these pathways are called tropic hormones.
Thyroid hormone regulates many functions, and low levels of thyroid hormone in the blood stimulate the hypothalamus to secrete thyrotropin-releasing hormone (TRH), causing the anterior pituitary to secrete thyroid-stimulating hormone (TSH).

Disorders of Thyroid Function and Regulation

Disruption of thyroid hormone production and regulation can result in serious disorders.
Thyroid hormone is the only iodine-containing molecule synthesized in the body.
With low levels of thyroid hormone, due to insufficient iodine, the pituitary continues to secrete TSH, causing the thyroid to enlarge, resulting in a goiter, a marked swelling of the neck.

Hormonal Regulation of Growth

Growth hormone (GH) is secreted by the anterior pituitary gland, and has tropic and nontropic effects.
The liver, a major target, responds to GH by releasing insulin-like growth factors (IGFs), which stimulate bone and cartilage growth.
An excess of GH can cause gigantism, while a lack of GH can cause dwarfism.

Parathyroid Hormone and Vitamin D: Control of Blood Calcium

Homeostatic regulation of calcium (Ca2+) in the blood is vital.
In mammals, parathyroid hormone (PTH) is released by the parathyroid glands when Ca2+ levels fall below a set point.

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Description

Learn about the role of pheromones in animal communication, including marking trails, defining territories, and attracting mates. Also, explore the chemical classes of hormones.