Seeing, hearing, moving, talking, tasting, swallowing, we take it all for granted. A lot of work
is needed from the brain to perform these features.
We can divide the human nervous system into two main parts:
• The central nervous system: brain and the spinal cord.
• The peripheral nervous system: everything else, so all the nerves leaving the spinal
cord for example.
We take information from our body/outer world via our spinal cord into the brain (sensory
pathways, afferent), giving an input. In the brain, integration and association will take place
and a certain decision will be formed. This leads to an output and is send from the brain via
the spinal cord to the body (motor pathways, efferent).
Information travels via nervous cells or neurons. Because we have two pathways (sensory
and motor), we also have two types of neurons:
• Afferent or sensory neurons: detect changes in internal/external environment and
send information to central nervous system (brain + spine).
• Efferent or motor neurons: send information from central nervous system to body,
controlling muscles and glands.
The brain consists of 100 billion neurons, forming 100 trillion connections.
There are two types of matter:
• Gray matter can be found on the outside of the brain. The color comes from capillary
blood vessels and neuronal cell bodies. So, the neurons that send and receive
information are mainly located in the gray
matter. These are organized in cortical
layers (outside of the brain) and
subcortical nuclei (inside of the brain).
• White matter is mostly colored white,
because these are the axons covered in an
insulating layer of glia cells (myelin) that
are send from these neurons to the rest of
the body and within the brain. Along these
axons, information travels due to electrical
stimulations. Myelin makes these signals
travel much faster. A large collection of
axons projecting to or away from nucleus
or layer is called a tract or fiber pathway.
The Nissl staining shows that we got nice patterns within the cortex and that we got
different collections of cell bodies within the cortical layers.
,Every area in the brain has a specific function. Even
within an area, there is a clear subdivision of functions.
Every part of the brain has another job to do.
The peripheral nervous system can be further divided:
• Somatic nervous system
• Autonomic nervous system
The somatic nervous system consists of all spinal and
cranial nerves to and from sensory organs, muscles,
joints and skin. These are the nerves that receive
incoming sensory information (vision, hearing, pain,
temperature, touch, position, movement) and relay
this information to the CNS. SNS also produces
voluntary movement, as it also transmits motor signals
to the muscles. Reflexes however also fall under the
SNS.
The autonomic nervous system is more important for the involuntary movement,
controlling the body’s internal organs (heart, blood vessels, lungs, airways, intestines…). We
can again divide the autonomic nervous system into:
• Parasympathetic (calming) nervous system: ‘rest and digest’
• Sympathetic (arousing) nervous system: ‘fight or flight’
We describe anatomical
locations in respect to the
neuraxis, an imaginary line
which you can draw
through the central
nervous system (from the
spine into the brain).
We also have different
anatomical viewpoints
when looking at the brain.
,Very early in our development, the brain starts off as a small plate, called the neural plate. It
starts to fold itself, so it creates a groove, called the neural groove. The neural folds come
together until they close and form a hollow tube, called the neural tube. When this doesn’t
happen correctly, you get a Spina Bilfida (open ruggetje). The tube starts to form
enlargements, which then
form the hindbrain, the
midbrain and the
forebrain. This three-part
structure is the most basic
plan of the brain as we can
see this for most
vertebrates. The forebrain
will develop into the
telencephalon and the
diencephalon. Towards
the back you also the
development of the
cerebellum, pons and the
medulla.
, Encephalon = brain (Greek)
All these structures have different functions. These functions show a hierarchical vertical
organization. In the lower structures that are more primitive from origin, we find more basic
life support functions. If we go up towards the more newly developed structures, you find
more complex functions.
• At the telencephalon, we find high-level mental activity in cortex (conscious
sensations, reasoning, planning, language)
• At the limbic system, we see emotion, memory and instincts related functions
• At the thalamus, we find the relay center, where sensory information is processed
• At the hypothalamus, we see feeding, sexual behavior and temperature regulation
• At the cerebellum, we find fine motor control and balance
• At the brainstem, we see arousal and basic life support (breathing, heartbeat)
Anatomy & Function II
The brain begins as a tube in early development and remains hollow after the tube folds and
matures. This hollow tube will form the large internal system of chambers, called ventricles.
The ventricles are filled with cerebrospinal fluid (CSF). CSF is constantly circulating through
the ventricular system. Its two main important functions are that is acts as a shock absorber
to reduce impact of knocks and it nourishes brain tissue. Blood is highly toxic to neurons and
start dying when they make contact, so therefore we have CSF.
There are four ventricles:
• Lateral ventricle
• Third ventricle
• Cerebral ventricle
• Fourth ventricle
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