The document discusses how brain cells work. It notes that the human brain contains two main types of cells - neurons and glial cells. Glial cells outnumber neurons and provide support and insulation. Neurons are the main signaling cells and transmit electrical signals via long projections called axons to other neurons or effector cells. At the junction between neurons, called a synapse, the electrical signal is converted to a chemical signal via neurotransmitters. This allows signals to be transmitted from one neuron to the next and enables the complex functioning of the human brain.

1. How brain cells work?

2. How brain cells work?
 What is the name of cells located in our brain?
 Guess, how many brain cells do we have?
 Do you know what makes them different from any other cells in our
body?
 What is their primary function?

3. How brain cells work?
 Human/vertebrate nervous system has two types of cells
Glial cells and Neurons

4. Glial cells
 Glial cells far outnumber neurons (they count 50x more than neurons), their name
comes from Greek – meaning glue
 Support neurons providing the brain with structure
 Insulate and separate neuronal groups from each other
 Some glial cells are scavengers – remove debris after injury or neuronal cell death
 Produce the myelin – to insulate axons of nerve cells
 Help nourish nerve cells, support them to conduct nerve signals

5. Different types of glial cells
 Astrocytes – star shaped glial cells, the most common,
support and repair nervous tissue, responsible for
plasticity of central nervous system
 Oligodendrocytes - wrap the tips of its tentacles around
axons in a „white matter“ coating called myelin
 Schwann cells - form a snug layer of myelin around the
axon, maintaining rapid conduction of nervous impulses
along axon, support neurons
 Microglia - this versatile microglia defend the brain from
invaders
 Oligodendrocyte precursor cells – may transform into
different kind of glia, but also in neurons
Astrocytes coloured with flourescent dye
Remember: astrocytes, oligodendrocytes and Schwann cells are
called macroglia

6. Different types of glial cells
more about Microglia
 Key cells in overall brain tissue maintenance
 They constantly scavenging the central nervous system for damaged or unnecessary neurons ,
synapses and infectious agenses
A) Resting microglia – small body and long branching
processes which are in constant movement - searching for
potential infectious agens
B) Reactive microglia – when in contact with „danger“ microglia becomes
shortening and thickening of branches and taking ameboid shape. Fights
off the infection as quickly as possible (by phagocytosis) to ensure
minimal injury on healthy brain cells
A B

7. Neural cells - Neurons
 Neural cells – Neurons – are the main signalling units of nervous system
 Neuron has four morphologically defined regions (each region has a distinct role in
generating signals between cells ):
 Cell body
 Dendrites
 Axon
 Presynaptic terminals

8. A simplified scheme of a multipolar neuron
Match: cell body, dendrites, nucleus, axon, node of Ranvier, myelin wreath, telodendria,
presynaptic terminals with synapses

9. Neural cells
 Cell body (soma)
 Contains nucleus – which stores genes of the cell , and endoplasmatic reticulum where
proteins for the cell are synthetised
 Usually gives rise to two kinds of processings :
 DENDRITES - branch out in tree-like fashion and process incoming signals from
the other neural cell
 one long tubular AXON – extends away from the soma and conduct signals to
other neurons or effector cells (muscle cells) , axons are usually insulated by a
myelin wreath that is interrupted at regular intervals by nodes of Ranvier. A the end
of an axon there is branching called telodendria with synapses

10. Neural cells
 Remember:
Whereas DENDRITES are the input signal elements of the neuron, the AXON is the only
output signal from the neuron

11. Neural cells – Axons
generating of an electric signal
 The cell conducting signal is generated in axon hillock (the initial segment of an axon)
 The signal is generated and propagated by charge-carrying ions including sodium
(Na+), potassium (K+), chloride (Cl−), and calcium (Ca2+)
 An axon can convey an electrical signal along distances up to 3metres. Electric signal is
called ACTION POTENIAL – is rapid, transient with duration of about 1ms, ( compare –
an eyeblink duration is 150ms)
 The signal moves down the axon by causing its depolarization
 Axon transmit signals to another neuron at a specific site called a synapse

12. Neural Synapse
 Junction point from one neuron to the next
 Determines the direction that the nervous system spreads from one
neuron to the next (one way signal)
Transmission of a signal through synapse:
The electrical signal from within the cell is
translated into a chemical signal using tiny
molecules called neurotransmitters. The pre-
synaptic neuron spits these transmitters into
the synapse, where they float across and bind
to receptors on the post-synaptic neuron. The
binding of transmitter provides the post-
synaptic cell with some information about how
it should respond to the signal, and it reacts
accordingly.

13. Neural cells - Neurons
 On the basis of shape, neurons are
classified into three groups:
 Unipolar cells – have a single
processing serving as a receptive and
releasing terminal (present in
invertebrates)
 Bipolar cells – have two processes
functionally specialized (1dendrite, 1
axon)
 Multipolar – have one axon and many
dendrites

14. Functional classification of neurons
 Afferent neurons -(sensory neurons)-
convey electrical impulses from
sensory receptors into the central
nervous system (CNS)
 Interneurons – connect neurons
within specific regions of the CNS
 Efferent neurons -(motor neurons) –
transmit signal from the CNS to the
effector (e.g. muscular) cells
Schematic diagram of reflex loop, notice afferent,
efferent neurons and interneurons

15. Neural cells – organization principle
 Individual nerve cells are relatively simple in their morphology, all
nerve cells share the same basic morphology
 The complexity of human behavior depends less on specialization of
individual nerve cell
 However these cells form precise anatomical circuits
 The key is organizational principle – nerve cells with similar
anatomical properties can produce different response due to their
unique connections to each other, or with the sensory receptors and
muscle cells

16. Summary
 Vertebrate nervous system consists two type of cells – neurons and glia
 Glial cells support neurons in their proper functioning
 Neurons are the main signalling units of nervous system – conduct electrical
signal from one cell to another or to effector cell (muscle, gland...)
 Junction point from one neuron to the next is called a synapse
 Synapse transforms electrical signal to a chemical signal by releasing of a small
amount of neurotransmitter into synaptic cleft, released molecules
neurotransmitter selectively bind to receptors of a postsynaptic cell – sending
signal to another neuron or providing desired response...

17. Brain structure

18. Brain structure

19. References:
https://blogs.scientificamerican.com
https://alieastrocyte.wordpress.com/2015/08/04/threes-
company-the-tripartite-synapse/
https://en.wikipedia.org/wiki/Microglia
http://humanbrainfacts.org/basic-structure-and-function-
of-human-brain.php