axis

(noun)

A line between two points that is used to give direction to an anatomical region.

Related Terms

Examples of axis in the following topics:

  • Regional Terms and Axes

    • The Dorsoventral axis (DV axis) is formed by the connection of the dorsal and ventral points of a region.
    • The Anterioposterior axis (AP axis) is the axis formed by the connection of the anterior (top) and posterior (bottom) ends of a region.
    • The AP axis of a region is by definition perpendicular to the DV axis and vice-versa.
    • The Left-to-right axis is the axis connecting the left and right hand sides of a region.
    • Axis (A) (in red) shows the AP axis of the tail, (B) shows the AP axis of the neck, and (C) shows the AP axis of the head.

  • The Stress Response

    • The body's stress response is mediated by the sympathetic nervous system and the hypothalmic-pituitary-adrenal (HPA) axis.
    • The body's stress response is mediated by interplay between the sympathetic nervous system (SNS) and the hypothalmic-pituitary-adrenal (HPA) axis .
    • A feedback loop exists among the components of the HPA axis and the SNS.
    • The paraventricular nucleus of the hypothalmus contains neuroendocrine neurons which synthesize and release vasopressin—a hormone which acts in the HPA axis as a vasoconstrictor—and corticotropin releasing hormone (CRH).
    • Glucocorticoids of the HPA axis have many important functions, including modulation of stress reactions, but in excess they may be damaging.

  • Overview of the Axial Skeleton

    • The axial skeleton consists of the 80 bones along the central axis of the human body.
    • The axial skeleton consists of the 80 bones along the central axis of the human body.
    • The word "axial" is taken from the word "axis" and refers to the fact that the bones are located close to or along the central axis of the body.

  • Body Planes and Sections

    • By imaging a patient in standard anatomical position, a radiologist can build an X-Y-Z axis around the patient to apply body planes to the images.
    • A human in the anatomical position, can be described using a coordinate system with the Z-axis going from front to back, the X-axis going from left to right, and the Y-axis going from up to down.

  • Supply of Blood and Nerves to Bone

    • The blood and nerve supply to bones are carried in Haversian canals which run along the long axis of bones.
    • These Haversian canals typically run parallel to the surface and along the long axis of the bone.

  • Embryonic Development

    • The neural tube becomes patterned along the dorsal-ventral axis to establish defined compartments of neural progenitor cells, which will give rise to distinct classes of neurons.
    • Sonic hedgehog (Shh) is a key player in patterning the ventral axis, while Bone morphogenic proteins (Bmp) and Wnt family members play an important role in patterning the dorsal axis.
    • The different combinations of expression of these transcription factors along the dorsal-ventral axis of the neural tube are responsible for creating the identity of the neuronal progenitor cells.

  • Aging and the Endocrine System

    • "Somatopause" is a term used to describe the change in GH/IGF-I axis which involves a decrease in production and sensitivity to GH and IGF-I.
    • Another hormone axis that changes with aging is the cortisol/DHEA axis.

  • Exhaustion

    • There is also some activation of the HPA axis, producing cortisol.

  • Posttraumatic Stress Disorder (PTSD)

    • These findings suggest abnormality in the hypothalamic-pituitary-adrenal (HPA) axis .
    • The HPA axis is a major biological mechanism of stress and stress response

  • Stress and Disease

    • In depression, the hypothalamic-pituitary-adrenal (HPA) axis is upregulated with a down-regulation of its negative feedback controls.
    • This leads to continual activation of the HPA axis and excess cortisol release.