BRAINSTEM The Brainstem lies at the base of the brain and the top of the spinal cord. The brainstem is located in the posterior cranial fossa. The brainstem is the structure that connects the cerebrum of the brain to the spinal cord and cerebellum. Provides a pathway for tracts running between higher and lower neural centers. Divided into 3 major divisions: midbrain, pons, and medulla oblongata. It is responsible for many vital functions of life, such as breathing, consciousness, blood pressure, heart rate, and sleep. It contains many critical collections of white and grey matter. The grey matter within the brainstem consists of nerve cell bodies and form many important brainstem nuclei. Ten of the twelve cranial nerves arise from their cranial nerve nuclei in the brainstem. The white matter tracts of the brainstem include axons of nerves traversing their course to different structures. These tracts travel both to the brain (afferent) and from the brain (efferent) such as the somatosensory pathways and the corticospinal tracts, respectively. Mid Brain The midbrain is continuous with the cerebral hemisphere. The upper posterior (i.e. rear) portion of the midbrain is called the tectum, which means "roof." The surface of the tectum is covered with four bumps representing two paired structures: the superior and inferior colliculi. The superior colliculi are involved in eye movements and visual processing, while the inferior colliculi are involved in auditory processing. Another important nucleus, the substantia nigra, is located here. The substantia nigra is rich in dopamine neurons and is considered part of the basal ganglia. Pons An important pathway for tracts that run from the cerebrum down to the medulla and spinal cord, as well as for tracts that travel up into the brain. It also forms important connections with the cerebellum via fibre bundles known as the cerebellar peduncles. Posteriorly, the pons and medulla are separated from the cerebellum by the fourth ventricle. Home to several nuclei for cranial nerves. Medulla The point where the brainstem connects to the spinal cord. Contains a nucleus called the nucleus of the solitary tract that is crucial for our survival (receives information about blood flow, along with information about levels of oxygen and carbon dioxide in the blood, from the heart and major blood vessels). When this information suggests a discordance with bodily needs (e.g. blood pressure is too low), there are reflexive actions initiated in the nucleus of the solitary tract to bring things back to within the desired range. Blood Supply The brain stem receives its blood supply exclusively from the posterior circulation, including the vertebrae and basilar artery. The medulla receives its blood supply from the vertebral via medial and lateral perforating arteries. The pons and midbrain receive their blood from the basilar via the medial and lateral perforating arteries.

1. BRAINSTEM
Presented by: Himani Kaushik (MPT Neurology)

2. INTRODUCTION
❖ The Brainstem lies at the base of the brain and the top of the spinal cord.
❖ The brainstem is located in the posterior cranial fossa.
❖ The brainstem is the structure that connects the cerebrum of the brain to
the spinal cord and cerebellum.
Provides a pathway for tracts running between higher and lower neural
centers.
❖ Divided into 3 major divisions:
➢ midbrain,
➢ pons, and
➢ medulla oblongata.

4. ❖ It is responsible for many vital functions of life, such as breathing,
consciousness, blood pressure, heart rate, and sleep.
❖ It contains many critical collections of white and grey matter.
➢ The grey matter within the brainstem consists of nerve cell bodies and
form many important brainstem nuclei. Ten of the twelve cranial nerves
arise from their cranial nerve nuclei in the brainstem.
➢ The white matter tracts of the brainstem include axons of nerves
traversing their course to different structures. These tracts travel both to
the brain (afferent) and from the brain (efferent) such as the
somatosensory pathways and the corticospinal tracts, respectively.

5. MIDBRAIN (or Mesencephalon)
❖ The midbrain is continuous with the cerebral hemisphere.
❖ The upper posterior (i.e. rear) portion of the midbrain is called the tectum,
which means "roof."
The surface of the tectum is covered with four bumps representing two
paired structures: the superior and inferior colliculi.
The superior colliculi are involved in eye movements and visual
processing, while the inferior colliculi are involved in auditory processing.

11. ❖ Another important nucleus, the substantia nigra, is located here.
The substantia nigra is rich in dopamine neurons and is considered part of
the basal ganglia.
In Parkinson's disease, neurodegeneration occurs in the substantia nigra,
and this neurodegeneration is associated with the hallmark movement
dysfunction we see in Parkinson's.

12. PONS (part of the metencephalon)
❖ An important pathway for tracts that run from the
cerebrum down to the medulla and spinal cord, as well as
for tracts that travel up into the brain.
It also forms important connections with the cerebellum
via fibre bundles known as the cerebellar peduncles.
❖ Posteriorly, the pons and medulla are separated from the
cerebellum by the fourth ventricle.
❖ Home to several nuclei for cranial nerves.

16. ❖ Nerves that carry information about sensations of touch, pain, and
temperature from the face and head synapse in a nucleus in the pons.
❖ Motor commands dealing with eye movement, chewing, and facial
expressions also originate in the pons.
❖ Additionally, cranial nerve nuclei in the pons are involved in several other
functions, including swallowing, tear production, hearing, and maintaining
balance/equilibrium.

17. MEDULLA (AKA Medulla Oblongata (myelencephalon)
❖ The point where the brainstem connects to the spinal cord.
❖ Contains a nucleus called the nucleus of the solitary tract that is
crucial for our survival (receives information about blood flow,
along with information about levels of oxygen and carbon
dioxide in the blood, from the heart and major blood vessels).
When this information suggests a discordance with bodily needs
(e.g. blood pressure is too low), there are reflexive actions
initiated in the nucleus of the solitary tract to bring things back to
within the desired range.

21. ❖ Essential to our survival because it ensures vital systems e.g
cardiovascular and respiratory systems are working properly.
❖ Responsible for several reflexive actions, including vomiting, swallowing,
coughing, and sneezing. Several cranial nerves also exit the brainstem at
the level of the medulla.
❖ Pyramidal decussation is the crossing of the fibers of the corticospinal
tracts from one side of the central nervous system to the other near the
junction of the medulla and the spinal cord.
"Bulb" is an archaic term for the medulla oblongata, 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.

22. BLOOD SUPPLY
❖ The brain stem receives its blood supply exclusively from the posterior
circulation, including the vertebrae and basilar artery.
❖ The medulla receives its blood supply from the vertebral via medial and
lateral perforating arteries.
❖ The pons and midbrain receive their blood from the basilar via the medial
and lateral perforating arteries.

25. FUNCTIONS
The brainstem has three broad functions:
❖ 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.
❖ Contains the nuclei of Cranial Nerves III to XII.

26. ❖ Contains important reflex centres associated with the control of:
➢ respiration e.g breathing
➢ cardiovascular system e.g BP
➢ Consciousness
➢ autonomic functions such as digestion, salivation, perspiration,
dilation or contraction of the pupils, urination, etc.

27. THANK YOU!