Chapter 2. Neuroanatomy Overview and Basic Definitions
The human nervous system can be divided into:
The central nervous system (CNS): the brain and spinal cord;
The peripheral nervous system (PNS): everything else.
During embryological development the CNS arises from a sheet of ectodermal cells that folds over to form the neural
tube. The neural tube forms several swellings and outpouchings in the head that eventually develop into the brain, while the
part of the neural tube running down the back of the embryo forms the spinal cord (Figure 2.2A,B).The fluid-filled cavities
within the neural tube develop into the brain ventricles, which contain cerebrospinal fluid (CSF).
The developing brain has 3 main divisions:
The forebrain (prosencephalon). Subdivided in the:
o Telencephalon (―end brain‖). Composed of the cerebral hemi‘s, cerebral cortex, white matter and basal
ganglia.
o Diencephalon. Composed of the thalamus, hypothalamus en epithalamus.
The midbrain (mesencephalon). Connecting the forebrain and the hindbrain.
The hindbrain (rhombecephalon). Composed of:
o Metencephalon: pons and cerebellum.
o Myelencephalon: medulla.
The brainstem: consists of the midbrain, pons and medulla (not the cerebellum). It controls many of the most basis bodily
functions necessary for survival such as aspiration, blood pressure and heart rate.
Cerebrospinal Fluid (CSF): is formed mainly by the choroid plexus in the ventricles (not only in the lateral but in all
ventricles). CSF circulates from the lateral ventricle, to the third ventricle, to the fourth ventricle en leaves the ventricles trough
the via foramina to percolate around the outside surface of the brain and spinal cord.
Meninges: from inside to outside PAD
Pia
Arachnoid
Dura
CSF travels in the space between the arachnoid and pia and is reabsorbed into the venous system by the arachnoid
granulations.
For structures above the midbrain the orientation of the NS is the same with respect to the ground as in reptiles. At the
midbrain and below, however, there is a rotation of 90 degrees since in the standing position the spinal cord is perpendicular
to the ground in humans.
,Planes of section:
Horizontal/transverse plane
Coronal plane
Saggital plane
o Midsaggital: saggital sections passing through the midline
o Parasaggital: when they are just off the midline.
The nervous system is composed of:
Neurons/nerve cells. Contains cell body, dendrites and axons.
o Multipolar: they have several dendrites and several axons.
o Bipolar: a single dendrite and a single axon arising from the cell body
(often sensory!)
o Pseudo-unipolar: their processes are initially fused and then split to
produce two long axons.
o Unipolar: both axons and dendrites arise from a single process coming off
the cell body (mainly in invertebrates).
Communication takes place at synapses. At chemical synapses, chemical
neurotransmitter molecules, stored in synaptic vesicles, are released from
presynaptic terminals. Then they bind to receptors on the postsynaptic neuron,
giving rise to either excitation or inhibition of the neuron. An action potential
occurs (60 m/sec.) They trigger release of NT molecules from the synaptic vesicles.
Axons are insulated by lipid myelin sheath.
o In the CNS: oligodendrocytes.
o In the PNS: Schwann cells.
Between myelin: nodes of Ranvier. Leads to saltatory conduction.
Glial cells/glia: support cells.
Chemical NT have 2 functions:
Communication between neurons:
o Excitatory postsynaptic potentials (EPSP‘s)
o Inhibitory postsynaptic potentials (IPSP‘s)
The postsynaptic neuron summates the EPSP‘s and IPSP‘s arising from many presynaptic inputs.
Neuromodulation: cellular mechanisms like neuronal growth.
Some of the most important NT:
Glutamate: excitatory neurotransmission, modulation of synaptic
plasticity and activation of second messenger systems.
GABA: inhibitory neurotransmission.
Acetylcholine: muscle contraction, autonomic functions,
parasympathetic functions, neuromodulation.
Norepinephrine: sympathetic functions and neuromodulation.
Dopamine: neuromodulation.
Serotonin: neuromodulation.
Histamine: excitatory neuromodulation.
Glycine: inhibitory neurotransmission.
Peptides: neuromodulation.
In the CNS: glutamate and GABA. In the PNS: acetylcholine and
Norepinephrine.
Central Nervous System is made of:
White matter: myelinated axons.
Gray matter: cell bodies.
The service of the hemi‘s is coved by a mantle of gray matter called cerebral cortex. Gray matter is also found in large clusters
of cells called nuclei located deep within the hemi‘s and brainstem: basal ganglia, thalamus and cranial nerve nuclei.
Several different names with similar meaning are used for white matter pathways including: tracts, fascicle,
lemniscus, bundle.
A white matter pathway that connect structures on the right and left side of the CNS is called a commissure.
Axons in the PNS form bundles that are called peripheral nerves.
Clusters of cell bodies are called ganglia.
Pathways:
Carrying signals toward a structured: afferent (‗arive‘)
Carrying signals away from a structure: efferent (‗exit‘).
, Nerves:
Brainstem: cranial nerves (12 pairs).
Spinal cord: spinal nerves.
Cervical cord (C1 t/m C8)
Thoracic cord (T1 t/m T12)
Lumbar cord (L1 t/m L5)
Sacral cord (S1 t/m S5)
Motor systems tend to be more ventral (or anterior) and sensory systems more dorsal (or posterior). During
development, the bony vertebral canal increases in length faster than the spinal cord, therefor the spinal
cord ends at the level of the first or second lumbar bones.
Cauda equine: collection of nerve roots below the spinal cord.
Nerves controlling the extremities give rise to elaborated meshworks referred to a the brachial plexus for
the arms and the lumbosacral plexus for the legs. In addition, the spinal cord contains a relatively
increased amount of gray matter in these segments, causing the overall thickness of the cord to be greater:
cervical enlargement and lumbosacral enlargement.
The PNS consists of:
Autonomic nervous system.
o Sympathetic nervous system: from thoracic and lumbar.
o Parasympathetic nervous system: from cranial en sacral.
Cerebral cortex:
Infoldings on the cortex: sulci (1 sulcus)
Bumps and ridges of the cortex: gyri (1 gyrus)
Deep sulci: fissure.
Additional region: insular cortex. Is covered by the lip
of frontal cortex and parietal cortex: the frontal
operculum and parietal operculum.
The two cerebral hemispheres are separated in the
midline by the interhemispheric fissure, also known
as the sagittal or longitudinal fissure.
A large, C-shaped band of white matter called the
corpus callosum (meaning ―hard body‖) connects both
homologous and heterologous areas in the two
hemispheres.
The human nervous system can be divided into:
The central nervous system (CNS): the brain and spinal cord;
The peripheral nervous system (PNS): everything else.
During embryological development the CNS arises from a sheet of ectodermal cells that folds over to form the neural
tube. The neural tube forms several swellings and outpouchings in the head that eventually develop into the brain, while the
part of the neural tube running down the back of the embryo forms the spinal cord (Figure 2.2A,B).The fluid-filled cavities
within the neural tube develop into the brain ventricles, which contain cerebrospinal fluid (CSF).
The developing brain has 3 main divisions:
The forebrain (prosencephalon). Subdivided in the:
o Telencephalon (―end brain‖). Composed of the cerebral hemi‘s, cerebral cortex, white matter and basal
ganglia.
o Diencephalon. Composed of the thalamus, hypothalamus en epithalamus.
The midbrain (mesencephalon). Connecting the forebrain and the hindbrain.
The hindbrain (rhombecephalon). Composed of:
o Metencephalon: pons and cerebellum.
o Myelencephalon: medulla.
The brainstem: consists of the midbrain, pons and medulla (not the cerebellum). It controls many of the most basis bodily
functions necessary for survival such as aspiration, blood pressure and heart rate.
Cerebrospinal Fluid (CSF): is formed mainly by the choroid plexus in the ventricles (not only in the lateral but in all
ventricles). CSF circulates from the lateral ventricle, to the third ventricle, to the fourth ventricle en leaves the ventricles trough
the via foramina to percolate around the outside surface of the brain and spinal cord.
Meninges: from inside to outside PAD
Pia
Arachnoid
Dura
CSF travels in the space between the arachnoid and pia and is reabsorbed into the venous system by the arachnoid
granulations.
For structures above the midbrain the orientation of the NS is the same with respect to the ground as in reptiles. At the
midbrain and below, however, there is a rotation of 90 degrees since in the standing position the spinal cord is perpendicular
to the ground in humans.
,Planes of section:
Horizontal/transverse plane
Coronal plane
Saggital plane
o Midsaggital: saggital sections passing through the midline
o Parasaggital: when they are just off the midline.
The nervous system is composed of:
Neurons/nerve cells. Contains cell body, dendrites and axons.
o Multipolar: they have several dendrites and several axons.
o Bipolar: a single dendrite and a single axon arising from the cell body
(often sensory!)
o Pseudo-unipolar: their processes are initially fused and then split to
produce two long axons.
o Unipolar: both axons and dendrites arise from a single process coming off
the cell body (mainly in invertebrates).
Communication takes place at synapses. At chemical synapses, chemical
neurotransmitter molecules, stored in synaptic vesicles, are released from
presynaptic terminals. Then they bind to receptors on the postsynaptic neuron,
giving rise to either excitation or inhibition of the neuron. An action potential
occurs (60 m/sec.) They trigger release of NT molecules from the synaptic vesicles.
Axons are insulated by lipid myelin sheath.
o In the CNS: oligodendrocytes.
o In the PNS: Schwann cells.
Between myelin: nodes of Ranvier. Leads to saltatory conduction.
Glial cells/glia: support cells.
Chemical NT have 2 functions:
Communication between neurons:
o Excitatory postsynaptic potentials (EPSP‘s)
o Inhibitory postsynaptic potentials (IPSP‘s)
The postsynaptic neuron summates the EPSP‘s and IPSP‘s arising from many presynaptic inputs.
Neuromodulation: cellular mechanisms like neuronal growth.
Some of the most important NT:
Glutamate: excitatory neurotransmission, modulation of synaptic
plasticity and activation of second messenger systems.
GABA: inhibitory neurotransmission.
Acetylcholine: muscle contraction, autonomic functions,
parasympathetic functions, neuromodulation.
Norepinephrine: sympathetic functions and neuromodulation.
Dopamine: neuromodulation.
Serotonin: neuromodulation.
Histamine: excitatory neuromodulation.
Glycine: inhibitory neurotransmission.
Peptides: neuromodulation.
In the CNS: glutamate and GABA. In the PNS: acetylcholine and
Norepinephrine.
Central Nervous System is made of:
White matter: myelinated axons.
Gray matter: cell bodies.
The service of the hemi‘s is coved by a mantle of gray matter called cerebral cortex. Gray matter is also found in large clusters
of cells called nuclei located deep within the hemi‘s and brainstem: basal ganglia, thalamus and cranial nerve nuclei.
Several different names with similar meaning are used for white matter pathways including: tracts, fascicle,
lemniscus, bundle.
A white matter pathway that connect structures on the right and left side of the CNS is called a commissure.
Axons in the PNS form bundles that are called peripheral nerves.
Clusters of cell bodies are called ganglia.
Pathways:
Carrying signals toward a structured: afferent (‗arive‘)
Carrying signals away from a structure: efferent (‗exit‘).
, Nerves:
Brainstem: cranial nerves (12 pairs).
Spinal cord: spinal nerves.
Cervical cord (C1 t/m C8)
Thoracic cord (T1 t/m T12)
Lumbar cord (L1 t/m L5)
Sacral cord (S1 t/m S5)
Motor systems tend to be more ventral (or anterior) and sensory systems more dorsal (or posterior). During
development, the bony vertebral canal increases in length faster than the spinal cord, therefor the spinal
cord ends at the level of the first or second lumbar bones.
Cauda equine: collection of nerve roots below the spinal cord.
Nerves controlling the extremities give rise to elaborated meshworks referred to a the brachial plexus for
the arms and the lumbosacral plexus for the legs. In addition, the spinal cord contains a relatively
increased amount of gray matter in these segments, causing the overall thickness of the cord to be greater:
cervical enlargement and lumbosacral enlargement.
The PNS consists of:
Autonomic nervous system.
o Sympathetic nervous system: from thoracic and lumbar.
o Parasympathetic nervous system: from cranial en sacral.
Cerebral cortex:
Infoldings on the cortex: sulci (1 sulcus)
Bumps and ridges of the cortex: gyri (1 gyrus)
Deep sulci: fissure.
Additional region: insular cortex. Is covered by the lip
of frontal cortex and parietal cortex: the frontal
operculum and parietal operculum.
The two cerebral hemispheres are separated in the
midline by the interhemispheric fissure, also known
as the sagittal or longitudinal fissure.
A large, C-shaped band of white matter called the
corpus callosum (meaning ―hard body‖) connects both
homologous and heterologous areas in the two
hemispheres.
