IVANA HRADILOVÁ SVÍŽENSKÁ
organ system containing a network of
specialized cells (neurons and glia)
that coordinate the actions of an
organism and transmit signals between
different parts of its body
Nervous system
 one of four major classes of vertebrate
tissue
 composed of
 neurons - transmit impulses
 glial cells - assist propagation of the
nerve impulse as well as provide
nutrients to the neuron
Nervous tissue
Zones of a neuron
Structural classification of neurons:
A. multipolar neurons
B. bipolar neurons
C. pseudounipolar neurons
D. unipolar neurons
Neuron
- a complex internal scaffold of protein
filaments and tubules and their
associated proteins.
1. neurotubules - 20-25 nm in diameter
2. neurofilaments - 10 nm in diameter
3. actin microfilaments - 5 nm in diameter
Cytoskeleton
- a distribution of many substances and
organelles through the cytoplasm
to and from the neuronal body
axoplasm = cytoplasm of the axon
Axoplasmic transport
 turnover of membranous and skeletal
materials
 movement of neurotransmitters to the
synapses
 recognition of the surroundings
 not changed during the conduction
of nerve impulses
Axoplasmic transport
 Speed
 fast rate >100 mm/day (i.e., hundreds of
mm/day)
 slow rate < 10 mm/day
 Direction
 anterograde movement from the cell body to
the terminals
fast+ slow
 retrograde movement toward the cell body
fast
Axoplasmic transport
 Rapid (at a speed of 300-400 mm/day)
 Synaptic vesicles, transmitters, mitochondria,
lipids and proteins of the plasma membrane
 Slow (at 5-10 mm/day)
 skeletal elements, proteins and other
substances to renew and maintain the
axoplasm, soluble enzymes
Anterograde transport
 Rapid (at a speed of 150-200 mm/day)
 transport of exhausted organelles and old
membrane constituents(e.g. receptors, …)
 transport of trophic and other signalling
molecules from the periphery to the neuronal
body
 some neurotropic viruses such as poliomyelitis,
herpes, and rabies and neurotoxins enter
peripheral nerve endings and ascend to infect
the cell body via retrograde transport
Retrograde transport
Fast axonal transport
Slow axonal transport
Glial cells
PNS (neural crest)
• Schwann cells
• satellite glial cells
• enteric glial cells
CNS
 Microglia (mesoderm)
specialized macrophages capable of phagocytosis
that protect neurons of the central nervous system
 Macroglia (ectoderm)
• Astrocytes
• Oligodendrocytes
• Ependymal cells
• Radial glia
Radial glia
Glia of PNS
 Schwann cells
• conduction of nervous impulses along axons
• nerve development and regeneration
• trophic support for neurons
• production of the nerve ECM
• modulation of neuromuscular synaptic activity
• presentation of antigens to T-cells
Glia of PNS
 Schwann cells
• myelinating Schwann cells form myelin sheaths
around peripheral axons
• non-myelinating Schwann cells
• terminal Schwann cells
Saltatory conduction
Myelination in the PNS
mesaxon
Schwann cell development
Node of Ranvier
Terminal Schwann cells
Pacinian corpuscle
 satellite glial cells - support neurons in the PNS ganglia
Glia of PNS
 surround neurons and hold them in place
supply nutrients and oxygen to neurons
insulate one neuron from another
destroy pathogens and remove dead
neurons
participate in synaptic transmission
regulate the clearance of
neurotransmitters from the synaptic cleft
release gliotransmitters such as ATP, which
modulate synaptic function
Glia of CNS
Astrocytes - provide a link between the vasculature and
neurons
 Oligodendrocytes - form the myelin sheath around axons
of the CNS
 Microglia - phagocyte cells that migrate through the CNS
removing foreign matter and degenerated brain tissue
 Ependymal cells - line the ventricular system of the CNS,
are involved in the secretion of the cerebrospinal fluid
and aid in its circulation
Glia of CNS
Myelin sheath in the CNS
BARRIERS OF THE CNS
Intracellular compartment
Extracellular compartment
Compartment of CSF
Intravascular compartment
Meningeal barrier
Blood – CSF barrier
Blood – brain barrier
 A barrier separating the circulating blood from the
extracellular space of the CNS
 Functions
• protects the brain from "foreign substances" in the
blood that may injure the brain
• protects the brain from hormones and neurotransmitters
in the rest of the body
• maintains a constant environment for the brain
BLOOD – BRAIN BARRIER
• Endothelial cells connected by tight junctions
• Foot processes of astrocytes
• Basement membrane
Structural
components
of BBB
Transport through the BBB
• simple diffusion (lipofillic substances)
• facilitated diffusion through a protein carrier
energy independent
• simple diffusion through an aqueous channel
• active transport – energy dependent
 areas of the human brain without the BBB:
• Pineal body (epiphysis)
• Neurohypophysis (posterior pituitary) - releases
neurohormones (oxytocin and vasopressin) into blood
• Median eminence: regulates anterior pituitary through
release of releasing and inhibiting hormones
• Subcommissural organ: glycoprotein SCO-spondin
• Subfornical organ: important for the regulation
of body fluids
• Vascular organ of lamina terminalis: responsible
for osmosensory balance
• Area postrema: "vomiting center"
Circumventricular organs
Liquor cerebrospinalis (CSF)
Clear, colorless fluid,150 mL, secreted at the
rate of 500-800 mL daily
Produced by the choroid plexuses of ventricles
Protects the brain, prevents the weight of the
brain from compressing the nerves and vessels
against the cranium
Removes the harmful substances from the CNS
to venous blood
Has immune functions