Reticular Formation

ions to major pathways of the reticular activating system can thus impair consciousness, and severe damage can cause coma or a persistent vegetative state. Original Editor - Lucinda hampton

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Introduction[edit | edit source]

Brainstem areas properly belonging to the reticular formation

The brainstem reticular formation (RF) represents the archaic core of those pathways connecting the spinal cord and the brain.[1]

The RF is a complex network of brainstem nuclei and neurons that serve as a major integration and relay center for many vital brain systems to coordinate functions necessary for survival.

The RF forms a net-like connection of nuclei and neurons which work together with other regions of the central nervous system to allow complex tasks eg the regulation of our state of consciousness, emotion processing, visual coordination, cardiovascular control, and posture. Interneurons make up the vast majority of the neurons in the RF allow this vast connectivity, receiving approximately 100,000,000 nervous impulses every single second[2].

The reticular formation does not contain distinct boundaries, and the many nuclei included in this structure do not have precise delineations of territory.[3]

Ascending and Descending Pathways[edit | edit source]

Brainstem which includes: medulla oblongata; pons; midbrain

The reticular formation has two systems, an ascending and a descending.

  1. Ascending reticular activating system (ARAS) brings sensory messages from the RF to the brain cortex and vice versa. The ARAS is the regulator of consciousness and arousal and other information eg respiration rate, cough response, cardiac rhythm, and mastication (chewing).
  2. Descending reticular system (DRS) that brings messages to and from the motor neurons of the spinal cord, the reticulospinal tracts . These tracts are the major descending pathways from the reticular formation and act on many levels of the spinal cord to coordinate movements and autonomic functions. The reticulospinal tracts project to spinal cord motor neurons and help to modulate tone, balance, posture, and coordination of body movements with the assistance of other sensory stimuli, such as visual, auditory, vestibular, and proprioceptive information.

Both systems are part of a single parallel system as they work at the same time with ther RS modulating how many messages are processed. [2][3]

Functions Include:[edit | edit source]

Pain Modulation[edit | edit source]

The reticular formation is one means by which pain signals from the lower body reach the cerebral cortex. It is also the origin of the descending analgesic pathways. The nerve fibers in these pathways act in the spinal cord to block the transmission of some pain signals to the brain, activating the endogenous opioid system.[4]

Muscle Activity[edit | edit source]


The reticulobulbar and reticulospinal tracts also allow the reticular formation to have a wide spread impact on skeletal muscles: eg

  • Coordinates the activity of the respiratory centres that control the muscles of respiration.
  • Modifies reflex activity and muscle tone
  • Aids in the process of standing by working alongside the vestibular apparatus to preserve muscle tone in the antigravity muscles (antigravity muscles help maintain an upright, balanced posture) [5].

Consciousness[edit | edit source]


The RS being is the primary regulator of arousal and consciousness, suppresses the individual’s level of consciousness during sleep. Efferent fibers from the reticular formation can convey sensory information to the cortex of a sleeping individual, which would awaken that person. With injury or pathological insult to areas of the RF periods of unconsciousness may result. Bilateral damage to the reticular formation of the midbrain may lead to coma or death[5].

Habituation[edit | edit source]

Habituation is a process in which the brain learns to ignore repetitive, meaningless stimuli while remaining sensitive to others. eg when a person can sleep through loud traffic in a large city, but is awakened promptly by the sound of a crying baby. The reticular activating system contains RF nuclei that modulate activity of the cerebral cortex, thus responsible for habituation[4].

Autonomic and Endocrine System[edit | edit source]

The autonomic and endocrine nervous system is subject to regulation by the reticular formation.

  1. The descending reticulospinal and reticulobulbar fibers are involved with the craniosacral (parasympathetic) and thoracolumbar (sympathetic) outflows.
  2. The reticular formation indirectly regulates the endocrine nervous system by acting on the hypothalamus to regulate hormonal release.[5]

References[edit | edit source]

  1. Faraguna U, Ferrucci M, Giorgi FS, Fornai F. The functional anatomy of the reticular formation. Frontiers in Neuroanatomy. 2019 May 29;13:55. Available: (accessed 26.4.2022)
  2. 2.0 2.1 Biology Dictionart RF Available: (accessed 26.4.2022)
  3. 3.0 3.1 Mangold SA, Das JM. Neuroanatomy, Reticular Formation. InStatPearls [Internet] 2021 Jul 26. StatPearls Publishing.Available: 26.4.2022)
  4. 4.0 4.1 Med libre texts Reticular Formation. Available: (accessed 26.4.2022)
  5. 5.0 5.1 5.2 Ken Hub Reticular formation Available: (accessed 26.4.2022)