The central nervous system is divided into three
sections: hindbrain, midbrain, and forebrain. We
will discuss the hindbrain and midbrain and their
structures in this section, and we will discuss the
forebrain in the next section.
Picture showing the forebrain, midbrain, and hindbrain. In the small
drawings at the bottom, the forebrain, midbrain, and hindbrain areas
are shown in orange.
The hindbrain is at the back of the brain. The
structures in the hindbrain include the medulla,
the pons, and the cerebellum.
The medulla is a very important structure just
above the spinal cord. It controls vital reflexes
such as breathing, heart rate, vomiting, salivation,
coughing and sneezing. It accomplishes this
through the cranial nerves. The cranial nerves
control feelings from the head, muscle
movements in the head, and a lot of the
parasympathetic output to the organs, Some
cranial nerves have both sensory and motor
components. If the medulla is damaged, people
very often die.
The pons has many axons that cross from one
side of the brain to the other, and it also contains
neurons from the cranial nerves. Because of this
crossing over, the left side of the brain controls
muscles on the right side of the body and the
right side of the brain controls muscles on the left
side of the body.
The cerebellum is important for movement, for
balance, and for coordination. The cerebellum
has many other important functions, including
controlling the ability to shift attention between
sound and sight stimuli. It also is associated with
timing, so that a person who has damage to the
cerebellum would not be able to judge if one
rhythm is faster than another.
The midbrain is right in the middle of the brain.
The structures in the midbrain include the
superior colliculus, the inferior colliculus, the
tectum, and the substantia nigra,
The superior colliculus and the inferior colliculus
are both important routes of sensory information
to the brain.
The tectum is the roof of the midbrain.
The substantia nigra has the dopamine pathways.
Dopamine is a neurotransmitter important for
such things as eating regulation, depression, and
addictive behavior. The substantia nigra pathways
break down in people with Parkinson’s disease.