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Contents:
The nervous system of the vertebrates
1. Main components
2. The mouse as a model
3. Brain and spinal cord
3.1 Evolution and development
3.2 Principles of organization
3.3 Blood and liquor system
Literature:
Dudel et al., Neurowissenschaft (Springer)
Reichert, Neurobiologie (Thieme)
Kandel et al., Principles of Neural Science (McGraw Hill)
Kahle, Taschenatlas der Anatomie, Band 3: Nervensystem und
Sinnesorgane (Thieme)
Greenstein and Greenstein, Color Atlas of Neuroscience (Thieme)
Development and anatomical organization of the
nervous system II
Increase in centralization and cephalization:
In humans, the majority of the neurons are located in the brain and about
99,999% of the nerve cells are interneurons
The nervous system of the vertebrates
Sensory
InputMotor
outputIntegration
Sensory
inputMotor
outputIntegration
The nervous system of the vertebrates: Main components
PNS: Groups of neurons (ganglia) and peripheral nerve tracks
- somatic part
- autonomous (vegetative) part - sympathic part
- parasympathic part
(Campbell et al.,
Biologie)
Central nervous system (CNS): Brain
The nervous system of the vertebrates: Main components
forebrain midbrain hindbrain
Forebrain: Telencephalon, Diencephalon (Thalamus, Hypothalamus)
Midbrain: Mesencephalon (Tectum)
Hindbrain: Metencephalon (Pons, Cerebellum), Myelencephalon
(Medulla oblongata)
Brainstem: Midbrain + Hindbrain - Cerebellum
CNS: Spinal cord
- Segmented organization (31 paired
spinal nerves in 4 major regions),
- H-like structure: gray and surrounding
white matter
- Divided into dorsal and ventral horn and
dorsal, lateral, and ventral
columns(Kandel et al., Principles of Neural
Science)
Evolution and development
Somatic nervous system:
Signals to skeletal muscle in response
to external stimuli
Autonomous (vegetative) nervous
system: signals that affect the inner
milieu (energy metabolism and
homeostasis)
Two subunits:
Sympathicus: Increase in energy
consumption, organism is prepared for
action ("fight and flight")
Parasympathicus: reduction of energy
consumption, recovery ("rest and
digest")
Peripheral nervous system (PNS)
(Kahle, Taschenatlas der Anatomie Band 3)
The nervous system of the vertebrates: Main components
Main axes of the CNS
(Kandel et al., Principles of Neural
Science)
The nervous system of the vertebrates: Main components
The nervous system of the vertebrates: The mouse as a
model
The nervous system of the vertebrates: The mouse as a
model
> 99% of all genes have homolog in humans (a gene inherited in
two species by a common ancestor) → disease model
Diverse genetic tools: (conditional) transgenic, knockout, knock-in mouse
models
Complete genome information (2002)
Limitations:
- Rats are a better model for high blood pressure and atherosclerosis
- Rabbits are physiologically more similar to humans
Fertilized egg Blastula Gastrulagrowth invagination
Formation of the neural plate
from the ectoderm along the
axis of the embryo
Evolution and development
Nervous system
multilayered structure of three
germ layers:
- ectoderm
- mesoderm
- endoderm
Evolution and development
Central nervous system (CNS)
Dorsally positioned tube-like
nerve strand (produced by invagination of the
neural plate)
Posterior part
→ spinal cord
Anterior part
→Vesicles
→Brain(Segmental structure,
present in both hemispheres
of the brain)
(Kahle, Taschenatlas der Anatomie Band 3)
Principles of organization
Mammal Body weight Brain weightRelative brain
weight
elephant
greenland whale
mouse
man
gorilla
cat
2047 kg
62250 kg
21 g
60-72 kg
95,5 kg
4-5 kg
4048 g
2490 g
0,4 g
1300-1500 g
425 g
27,3-32 g
0,2%
0,004%
1,9%
2-2,3%
0,46%
0,64-0,68%
(R. Nickel, A. Schummer, E. Seiferle, Lehrbuch
der Anatomie der Haustiere Bd. 4, Parey)
1. Increase in the relative size of the brain
2. Increase in differentiation and segmentation
Principles of organization
3. Increase in complexity of the forebrain
Principles of organization
4. Increase in the surface of the cerebral cortex
Principles of organization
5. Separation in gray and white matter
Functionality of the CNS requires optimization of two competing
requirements:
- high interconnectivity
- short conduction delays
→ Solution: Segregation between gray and white matter:
- High connectivity in small regions („local connections“) (maximal number of
cells: about 10,000 neurons with tolerable delay (ms range) → gray matter
- Fast connections with high conduction speed („global wiring“) → white matter
(Lit.: Wen, Q., and Chlovskii, D.B. (2005) Segregation of the brain into gray and white
matter: a design minimizing conduction delays. PLOS Computational Biol. 1: e78-
e87.)
Principles of organization
6.Serial organization and orderly connections
- Serial organization
(relays); information is
transformed at every step
- Pathways that link the
components (tracts, „Bahnen“)
- Pathways cross to the other side
(contralateral side) of the body at
a certain anatomical level
- Projections occur in an orderly
fashion thus producing neural
maps (somatotopy)
(Kandel et al., Principles of Neural
Science)
Principles of organization
Total of 700 km of veins
→ Large surface (180 cm2/g brain):
→ Efficient gas exchange (O2, CO2)
Blood supply
Brain is highly vulnerable – anoxia and ischemia within the range of
seconds cause neurologic symptoms and within the range of minutes
irreversible damage of neurons (stroke)
Blood and liquor system
(Kahle, Taschenatlas der Anatomie Band 3)
Blood supply by four large
arteries:
- 2 Arteriae carotides
internae
- 2 Aa. vertebrales
Blood supply
Blood and liquor system
(Kahle, Taschenatlas der Anatomie Band 3)
Cerebrospinal fluid (CSF)
Blood and liquor system
CNS is surrounded by Liquor
cerebrospinalis including the four
ventricles (about 140 ml) →
provides cushion and buoyancy
(Reduction of brain weight
from 1400 g to 45 g)
Liquor cerebrospinalis is present in the subarachnoid space
Secreted by the choroid plexus in the lateral ventricles
Absorbed through the arachnoid membranes (purple;
„Spinngewebshaut“) and transported through the arachnoid
granules into the venous sinuses → provides a one-way system
to remove harmful metabolites (turnover 3 times/24 hrs.)
Composition of the
CSF may be
altered during
disease →
diagnostic tool
(Kahle, Taschenatlas der Anatomie Band 3)
Cerebrospinal fluid (CSF)
Blood and liquor system
Cerebrospinal fluid (CSF)
Blood and liquor system
1st Goldmann-Experiment (Edwin Goldmann, 1909):
IV (intravenous) Trypan blue injection → No staining of brain and spinal cord
(Saunders et al., The rights and wrongs of
blood-brain permeability studies“
Frontiers in Neuroscience, 2014)
Blood brain barrier
Blood and liquor system
2nd Goldmann experiment: Trypan blue injection into liquor room →
only brain and spinal cord stain → blood-liquor barrier
Blood brain barrier is present already
early during embryonal
development
Blood brain barrier
Blood and liquor system
(Campbell, Biologie)
Blood brain barrier
Blood and liquor system
Blood brain barrier
Blood and liquor system
Blood brain barrier
Blood and liquor system
Tight junctions between endothelial cells formed under the influence of
astrocytes
1. Water-soluble substances do not
pass through the blood-brain
barrier
2. Lipid-soluble substances pass
through the blood-brain barrier
Blood brain barrier
Blood and liquor system
Disease: Hydrocephalus (accumulation
of CSF) – genetic defect or caused
by infection H. occlusus: blockage of foramina
H. aresorptivus: decreased resorption by
arachnoid membranes
H. hypersecretorius: increased production
Foramen interventriculare
(Monroi)
(Kahle, Taschenatlas der Anatomie Band 3)
Blood brain barrier
Blood and liquor system