Brainstem

Original Editor - Wendy Walker

Lead Editors - Lucinda hampton, Olajumoke Ogunleye, Evan Thomas, Pacifique Dusabeyezu, Wendy Walker, Kim Jackson, Garima Gedamkar, WikiSysop, Aya Alhindi, Tarina van der Stockt, Daniele Barilla and Carina Therese Magtibay

Description

The Brainstem lies at the base of the brain and the top of the spinal cord. It houses many of the control centres for vital body functions, such as swallowing, breathing, and vasomotor control.

Structure

The brainstem is generally said to be composed of three parts.

Components, from above downward:

1. Midbrain (or Mesencephalon)
2. Pons (part of the metencephalon)
3. Medulla AKA Medulla Oblongata (myelencephalon)

Midbrain:

This consists of 3 parts: the tectum, the tegmentum and paired cerebral peduncles.

The substantia nigra lies in the cerebral peduncles.

Pons:

Consists of a posterior part, the tegmentum, and an anterior basilar part.

Medulla:

The "bulb" is an archaic term for the medulla oblongata, and in modern clinical usage the word bulbar (e.g. bulbar palsy) is retained for terms that relate to the medulla oblongata. The word bulbar can refer to the nerves and tracts connected to the medulla, and also by association to the muscles thus innervated, such as those of the tongue, pharynx and larynx.

Anatomical Relations

The brainstem is located in posterior cranial fossa.

Above, the midbrain is continuous with the cerebral hemisphere.
Below, the medulla is continuous with the spinal cord.
Posteriorly, the pons and medulla are separated from the cerebellum by the fourth ventricle.

Function

The brainstem has three broad functions:
1. Serves as a conduit for the ascending tracts and descending tracts connecting the spinal cord to the different parts of the higher centres in the forebrain;
2. Contains important reflex centres associated with the control of:

• respiration
• cardiovascular system
• consciousness

3. Contains the nuclei of Cranial Nerves III to XII.

The brain stem is responsible for, and regulatory of, the following functions of the human body:
Alertness
Attention
Arousal
Breathing
Heart rate
Blood pressure
Conveys information and signals shared between the peripheral nerves and spinal cord to the upper brain
Other autonomic functions such as digestion, salivation, perspiration, dilation or contraction of the pupils, urination, etc.

Clinical Significance

A Stroke affecting the brainstem can cause severe symptoms which include:

Problems with vital functions, such as breathing - frequently resulting in death
Difficulty with chewing, swallowing, and speaking
Weakness or paralysis in the arms, legs, and/or face
Problems with balance or sensation
Hearing loss
Vision problems
Vertigo—a feeling of spinning or whirling when you are not moving
Locked-in Syndrome
Coma

Brainstem lesions frequently occur in Multiple Sclerosis, with visual problems including blurred double vision being a common early symptom of MS.

Central pontine myelinolysis is a concentrated, frequently symmetric, noninflammatory demyelination within the pons.

Recent Related Research (from Pubmed)

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References

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