endocrine signaling

Examples of endocrine signaling in the following topics:

• Forms of Signaling

  • The major types of signaling mechanisms that occur in multicellular organisms are paracrine, endocrine, autocrine, and direct signaling.
  • There are four categories of chemical signaling found in multicellular organisms: paracrine signaling, endocrine signaling, autocrine signaling, and direct signaling across gap junctions .
  • Signals from distant cells are called endocrine signals; they originate from endocrine cells.
  • In chemical signaling, a cell may target itself (autocrine signaling), a cell connected by gap junctions, a nearby cell (paracrine signaling), or a distant cell (endocrine signaling).
  • Paracrine signaling acts on nearby cells, endocrine signaling uses the circulatory system to transport ligands, and autocrine signaling acts on the signaling cell.

• Comparing the Nervous and Endocrine Systems

  • The nervous system and endocrine system both use chemical messengers to signal cells, but the speed of transmission is different.
  • If you see a bear, your eyes send signals through your brain that eventually lead to the release of hormones, including adrenaline, from the endocrine system.
  • Both the nervous system and the endocrine system use chemical messengers to signal cells, but the speed at which these messages are transmitted is different.
  • The endocrine system relies on hormones to elicit responses from their target cells.
  • This process takes significantly longer than that of the nervous system, as endocrine hormones must first be synthesized, transported to their target cell, and enter or signal the cell.

• The Endocrine System

  • Both the nervous and endocrine systems send messages everywhere inside the human body.
  • In the nervous system, signals travel very quickly, leading to instantaneous responses.
  • However, within the endocrine system, signals move slowly but last longer.
  • Hormones are chemicals within the endocrine system that affect physiological activity.
  • There are eight major endocrine glands, each with a different function.

• Hormone Functions

  • The endocrine system plays a role in growth, metabolism, and other processes by releasing hormones into the blood.
  • Target cells, those having a receptor for a signal, respond to a hormone when they express a specific receptor for that hormone.
  • Different tissue types may also respond differently to the same hormonal signal.
  • In humans, common endocrine system diseases include thyroid disease and diabetes mellitus.
  • In organisms that undergo metamorphosis, the process is controlled by the endocrine system.

• Hypothalamic-Pituitary Axis

  • The endocrine system uses chemical signals to communicate and regulate the body's physiology.
  • The collection of these glands makes up the endocrine system.
  • The hypothalamus in vertebrates integrates the endocrine and nervous systems.
  • The posterior pituitary receives signals via neurosecretory cells to release hormones produced by the hypothalamus.
  • They are released into the circulatory system via neural signaling from the hypothalamus.

• Target Cell Specificity

  • In essence, it is a chemical messenger that transports a signal from one cell to another.
  • Endocrine hormone molecules are secreted (released) directly into the bloodstream or simply diffuse through the interstitial spaces to nearby target tissues.
  • Receptors are protein molecules to which one or more specific kinds of signaling molecules may attach.
  • Endocrine action: the hormone is distributed in blood and binds to distant target cells.

• Control of the Pituitary Gland by the Hypothalamus

  • Whilst the pituitary gland is known as the 'master' endocrine gland, both of the lobes are under the control of the hypothalamus; the anterior pituitary receives its signals from the parvocellular neurons and the posterior pituitary receives its signals from magnocellular neurons.
  • It allows endocrine communication between the two structures.
  • Using these, the anterior pituitary is able to fulfill its function of regulating the other endocrine glands.

• Glandular Epithelia

  • Glandular epithelium contains glands, either exocrine or endocrine, allowing for secretory function.
  • Exocrine and endocrine epithelial cells are highly vascular.
  • There are two major classifications of glands: endocrine glands and exocrine glands.
  • An endocrine gland is its counterpart.
  • It secretes its essential product without the use of a duct directly into the bloodstream or else by diffusion into its surrounding tissue (paracrine signaling) where it often affects only target cells near the release site.

• Humoral, Hormonal, and Neural Stimuli

  • Insulin causes blood glucose levels to drop, which signals the pancreas to stop producing insulin.
  • A number of endocrine glands release hormones when stimulated by hormones released by other endocrine glands.
  • The anterior pituitary, in turn, releases hormones that regulate hormone production by other endocrine glands.
  • In some cases, the nervous system directly stimulates endocrine glands to release hormones, which is referred to as neural stimuli.
  • Here, neuronal signaling from the sympathetic nervous system directly stimulates the adrenal medulla to release the hormones epinephrine and norepinephrine in response to stress.

• Mechanisms of Hormone Action

  • Hormones are secreted by the glands of the endocrine system and they serve to maintain homeostasis and to regulate reproduction and development.
  • Glands of the endocrine system secrete hormones directly into the extracellular environment.
  • Hormone cells are typically of a specialized cell type, residing within a particular endocrine gland, such as thyroid gland, ovaries, and testes.
  • As a result, hormonal signaling is elaborate and hard to dissect.
  • Relay and amplification of the received hormonal signal via a signal transduction process