circumventricular organs

(noun)

So named because they are positioned at distinct sites around the margin of the ventricular system of the brain. They are among the few sites in the brain which have an incomplete blood-brain barrier and, as a result, can directly sense the concentrations of various compounds, particularly peptide hormones, in the bloodstream.

Related Terms

Examples of circumventricular organs in the following topics:

  • Circumventricular Organs

    • Circumventricular organs are situated adjacent to the brain ventricles and sense concentrations of various compounds in the blood.
    • Circumventricular organs (CVOs) are positioned at distinct sites around the margin of the ventricular system of the brain.
    • As a result, neurons located in circumventricular organs can directly sense the concentrations of various compounds, particularly peptide hormones, in the bloodstream without the need for specialized transport systems that move those compounds across the blood-brain barrier.
    • These organs include:
    • Vascular organ of lamina terminalis: Responsible for the homeostatic conservation of osmolarity.

  • Blood-Brain Barrier

    • Bacteriologist Paul Ehrlich observed that chemical dye injected into an animal would stain all of its organs except for the brain.
    • In a later experiment, his student Edwin Goldmann found that when dye is directly injected into the cerebrospinal fluid (CSF) of animals' brains, the brains were dyed while the rest of the organs were unaffected.
    • These include the circumventricular organs such as the area postrema, median eminence of the hypothalamus, pineal gland, and the posterior pituitary.

  • Levels of Organization

    • Living organisms are made up of four levels of organization: cells, tissues, organs, and organ systems.
    • An organism is made up of four levels of organization: cells, tissues, organs, and organ systems.
    • Most organs contain tissues such as parenchyma (used to perform the organ functions),  stroma (connective tissue specific to organs) and epithelial.
    • An organ system is a collection of organs that that work together to perform a similar function.
    • An organism contains organ systems made up of organs that consist of tissues, which are in turn made up of cells.

  • Organ Transplants

    • Organ transplantation involves moving organs between bodies (or from donor sites on patients' bodies) for the purpose of replacing recipients' damaged or absent organs.
    • Tissue transplants occur much more frequently than organ transplants.
    • Organ donors may be living or brain dead.
    • Organ trafficking is one problem.
    • Organ transplants are not regulated by the FDA.

  • Plant Tissues and Organ Systems

  • Formal Structure

    • Formal structure of an organization or group includes a fixed set of rules for intra-organization procedures and structures.
    • Practical experience shows no organization is ever completely rule-bound: all real organizations represent some mix of formal and informal characteristics.
    • Tended effectively, the informal organization complements the more explicit structures, plans, and processes of the formal organization.
    • This deviation was referred to as informal organization.
    • A formal organization is a fixed set of rules of intra-organization procedures and structures.

  • Flat versus tall organizations

    • By definition, a small business is typically a flat, centralized organization.
    • Flat organizations follow the decentralized approach, or organic system.
    • More decisions are made at the middle levels of the organization.
    • Internally, the organization as a whole encourages more participation between all levels of the organization.
    • A tall structure is a more formal, bureaucratic organization or mechanistic system.

  • Tissues in Levels of Organization

    • The next level is the organ system level.
    • Many organs working together to accomplish a common purpose create an organ system.
    • Cells form tissues, and tissues form organs.
    • Organs that fulfill related functions are called organ systems.
    • An organism is made up of interconnected organ systems.

  • Layers in an Organization: Tall vs Flat Organizations

    • A tall organization is a more formal bureaucratic or mechanistic organizational structure and management system.
    • Tall organizations have several tiers in their structural hierarchy and multiple levels of management control with regard to the daily operations of the organization.
    • Flat organizations follow the decentralized approach or organic system of organization and management.
    • Internally, the organization as a whole encourages more participation between all levels within the organization, promoting closer working relationships that potentially lead to better communication and creativity.
    • Various factors, both internal (i.e. management style, culture, etc.) and external (i.e. competition, regulation, etc.) to the organization, influence what type of structure an organization assumes.

  • Development of Human Resources

    • Human resources development (HRD) as a theory is a framework for the expansion of human capital within an organization through the development of both the organization and the individual to achieve performance improvement.
    • Groups within organizations use HRD to initiate and manage change.
    • Organization development (OD), empowering the organization to take advantage of its human resource capital.
    • TD alone can leave an organization unable to tap into the increase in human, knowledge, or talent capital.
    • HRD does not occur without the organization, so the practice of HRD within an organization is inhibited or promoted upon the platform of the organization's mission, vision, and values.