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Neuroanatomie niet duidelijk? Probeer deze volledige aantekeningen (in het engels)
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Aantekeningen van alle colleges over neuroanatomie in het engels.
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NeuroanatomyTerminology
The brain is a black box. This means that the information is going in (afferent), processed and
followed by an action. The afferent information is generated in sensor nerves. It goes to the brain
using afferent nerves. The black box processes the information and the command is conveyed with
efferent axons until it ends up in effector nerves.
The sense of touch is the most complicated and largest. It is sensed at 2 levels which are somatic and
visceral. They are two effector systems
• Somatomotor --> striated muscles
• Visceromotor --> smooth muscles and glands
The nervous system consist of neurons. It has dendrites to receive info, and the info is processed in
the soma. The axon then conveys an action potential to terminal trees. At the end of those trees we
have buttons and then synapses which contact another neuron etc.
Very important difference between neuron and other parts of the rest of the body: if you cut an
axon the part that is cut from the cell body (soma) will die because they have no proteins. It might
regrow, but it can’t be reattached. This has an important consequence on the nervous system.
Regeneration is necessary and takes months if not years.
A picture is not a mirror image! SO left side is right etc.
The left side of the brain controls the right side of the body and vice versa. When its transversal, you
look upwards as if you’re at the foot of the bed.
At the end of neuron tube (in the head) is the rostral side. At the legs we have the caudal side. We
have to keep track of where we are in the body in order to correctly situate ourselves in the brain.
The nervous system is subdivided in 2 parts:
• Central nervous system --> brain + spinal cord
• Peripheral nervous system --> mainly nerves that can be cranial or spinal. We can also find
clumps of neurons (these are called ganglia).
We also have a functional subdivision of the nervous system:
• Somatic --> voluntary control
• Autonomic --> regulates bodily function without us being conscious. The visceromotor
function is again subdivided between sympathetic (switch on for rigorous action such as
fight; flight or fight (FFF)) and parasympathetic (switch on for digestion etc).
The telencephalon becomes the two
hemisphere. The rhombencephalon
becomes the metencephalon, which
gives the cerebellum and pons, and the
myelencephalon, which gives the
medulla oblongata.
The neural tube is hollow and the lumen
gives the ventricles.
,The brain itself is also subdivided:
1 – separate hemisphere The cortex has a convoluted surface with lobes. They are named
2 – corticocollosum after the part of the skull behind which they are located. Most of
the cortex is inside the convolution. The central sulcus seperated
3 – diencephalon frontal and parietal lobes. Lateral sulcus separates temporal with
the rest. The difference between sulcus and fissure is that the
4 – mesencephalon fissure is deep and that the sulcus is boarded by neocortex while
5 – pons fissure is lined by other types of cortex. We also have the precentral
and postcentral gyrus that board the central sulci in frontal and
6 – medulla oblongata parietal lobes respectively. These are areas of the cortex. The cortex
has specific functions according to areas.
7 – cerebellum Nerves are bundles of axons.
, Neurocytology
The neuron is the most important cell in de nervous system. It has a dendrite (receptive portion), a
cell body called perikaryon connected to an axon, which conveys an action potential to telodendria
and then to a vesicle that conveys it to another portion called terminals. This vesicle is called a
synapse.
All the changes of membrane potential are accumulated at the axon hillock and lead to an action
potential if they are above a certain threshold. The action potential is all or none signal. A neuron
always makes the same action potential. The myelin sheath makes it that only parts of the axon are
electrically active so the signal jumps in a saltatory conduction. It increases the speed.
At the synapse, the neurotransmitters are diffused in synaptic cleft and bind ion channels to either
close or open them. There is an ion flow that leads to change of membrane potential. This leads to
postsynaptic potential.
The action potential does not diminish when it travels but postsynaptic potential does.
A lesion in afferent flow leads to loss of sensory function. You won’t be able to feel a limb or hear
etc. In the efferent system you have an effector deficit so somato- or visceromotor functions. A
lesion in the black box leads to hindered processing so changes in cognitive functions. Usually we
have combined damage with afferent and efferent both affected, because they are usually located
near eachother.
The neurons works with membrane potential and need to be shielded from the rest of the body (this
constitutes the blood-brain barrier). This is done by astrocytes. They make the blood brain barrier
together with vascular cells. It guards the entrance to the brain. The entire outside of the brain is
covered by end feet of astrocytes. The same can be seen in the ventricles. This constitutes the brain
liquor barrier.
The outside of a neuron is also always covered. The cell body is covered with astrocytes. They also
control levels of ion present in extracellular space (especially K+).
Oligodendrocytes create the myelin sheats of axons. For axons which are not covered with
myelinated sheats these are covered with end feet of astrocytes and have no saltatory conduction,
so a slower rate of action potential.
The ventricles are covered by ependymal cells on the inside. These create fluid (cerebral spinal fluid)
which is a filtrate of the blood with extra stuff. These cells also allow the circulation of the CSF using
their cilia. The production is done at the choroid plexus. The CSF plays a role in metabolic function
and covers the outside in a shock absorbing way (mechanical function).
All these cells emerge from neuro ectoderm with the neurons.
Microglial cells, which are mononuclear phagocytes, clean the waste up and are present everywhere
in the body, but they are not originating from the same source (ectoderm). These cells can lead to
multiple pathology because they have an activating and deactivating system which can be faulty.
In the peripheral nervous system we have satellite cells which cover the outside of neurons so they
do the same as astrocytes.
Schwann cells exist in a myelinating form (similar to oligodendrocytes) and unmyelinating form. In
the latter they form grooves where the axons are sunk. This is not electrical insulation so no
saltatory conduction but it we have an environmental insulation.
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