An educational presentation on basics of neuroanatomy. It defines various cells of nervous tissue. the structure and function is well defined. It also covers various scientific terminologies and lastly their is graphical representation of action potential generation.

1. DR. AYSHAH HASHIMI

2. Nervous System
• Large
• Complex organ
• Serve as center for nervous system
• Located in head
Two parts
• CNS
 Brain
 Spinal cord
• PNS
 Sensory
 Motor

3. Brain
• Main part of nervous system
• It integrates the received information and coordinates and influences the activity of all parts of the bodies
Brain 3 parts
• Forebrain/ Prosencephalon
• Midbrain/ Mesencephalon
• Hindbrain/ Rhombencephalon
Or
• Cerebrum
• Cerebellum
• Brainstem (Midbrain + Pons + Medulla)
Cerebrum
Cerebellum
Brainstem
Forebrain
Hindbrain
Midbrain

4. Forebrain/ Prosencephalon
2 parts
• Telencephalon (cerebral cortex) consist of 4 lobes
 Frontal
 Parietal
 Occipital
 Temporal
• Diencephalon consists of
 Thalamus
 Hypothalamus
 Pineal gland

5. Midbrain consist of
• Tectum
• Cerebral peduncle
• Substantia nigra
Hindbrain/ Rhombencephalon
• Metencephalon (Pons and Cerebellum)
• Myelencephalon (medulla oblongata)

6. Nervous system
• Neurons concern with communication signal
• Glial cells/ Supporting cells
What are Gyri and Sulci?
Gyrus are ridges on the cerebral cortex surrounded by sulci. They create folded appearance of a brain
Now anatomically CNS has 2 parts
• Grey matter
• White matter
Grey matter is collection of cell bodies of neurons within the CNS
White matter is collection of axons within the CNS

7. Division of grey matter
• Cortex (grey matter at periphery)
• Nucleus (pieces of grey matter that are embedded or surrounded by white matter )
Division of White matter
• Tracts : they take information within the CNS upward or downward
 Ascending tracts
 Descending tracts
• Commissural fibres: they connect or transmit information from right to left within the CNS (corpus callosum)
• Association fibres: they connect anterior to posterior

8. Reticular formation
• In brain grey matter is at periphery mainly while in spinal cord they are in centre so in brain stem grey
matter lies in centre.
• Motor sense/tract from cortex and sensory sense/tract from spinal cord criss-cross at brainstem
fragmenting its grey matter into small pieces. This structure is called as reticular formation. Many nucleus
arises from brainstem.

9. Peripheral Nervous System
• It is one of the two components that makeup the nervous system.
• Consists of nerves and ganglia outside the brain and spinal cord
• It serves as a relay between the CNS and the body
• Sensory PNS is classified into
1. Special senses ( vision, olfaction, taste, hearing, balance)
2. General senses are of two types
A. Somatic sensation (skin, locomotor system(pain, temp., vibration proprioception-sense of position))
B. Visceral sensation (pain or discomfort)
Other type of senses
1. Conscious sense
2. Unconscious sense (BP, peristalsis)

10. Motor response
• Somatic motor responses (controlled by us)
• Visceral/Autonomic motor response (uncontrollable) 2 types
 Sympathetic Nervous system
 Stimulate on fight and flight response
 Two kind of neurons preganglionic and postganglionic neurons
 Originate from thoracolumbar division of spinal cord (T1-L2/L3)
 Parasympathetic Nervous system
 Stimulate on rest and digest or feed and breed
 Originate from central nervous system as cranial nerves and sacral division (S2-S4) of spinal
cord (Craniosacral outflow)

11. Structure of Neuron
Neuron is a fundamental unit of nervous system that generate electrical signals called
action potential which allows them to quickly transmit information over long distances
It consist of 3 parts – Cell body, Dendrites and Axon
Dendrites
• Multiple extensions that extrude from cell body of neuron that communicate
with other neurons to collect information or receive information
• Increase the surface area of the neuron and act as sensory receptor.
• They tend to taper
• The dendrites have ligand gated ion channels and G protein coupled receptor
for the production of EPSP (excitatory postsynaptic potential) and IPSP
• on its surface

12. Cell Body/Soma/Cyton
• A compact structure that contains nucleus and in cytoplasm have Nissl’s granules
(present in both soma and dendrites but not in axon)
• Its function is to synthesize and release proteins that are important for neuronal
growth and regeneration of axons and could be neurotransmitter, enzymes etc.
Axon Hillock is junction between soma and axon
Axon
• Large single extension that conducts the processed information from neuron to
the axon terminal in the form of action potential (depolarization and
repolarization wave)
• Kinesin is a special protein present inside the axon that transfer these enzymes,
neurotransmitters and certain protein from the cell body towards the terminal
axon

13. • Dynein are proteins that transport in opposite direction i.e. from synaptic end to cell body and this
transport is called as Retrograde Axonal transport (nerve growth factors, mitochondria)
• Apart from this axonal transport, various infections like polio, rabies, varicella zoster, herpes simplex etc.
are using this machinery for their movement to cell body from axon terminal and back to it
• Voltage gated ion channels (Sodium and potassium)
• They have special insulating substance called myelin
Axon terminal
• Have voltage gated calcium channel
• Synoptic knobs contains neurotransmitter that are released to carry out the concerned function in
response to cacium
• Reuptake of neurotransmitters
• Myelin sheath an insulating layer around the axon and is not continuous to increase the saltatory
conduction of neuron. Schwann cells in PNS and Oligodendrites in CNS wrap over the axon to form myelin
sheath

14. Structural classification of neurons
• Unipolar are found in skin
• Bipolar in retina and olfactory cells
• Pseudo-unipolar in dorsal root ganglia of spinal cord, 5th cranial nerve nuclei
• Multipolar in most part of the body

15. Functional Types
• Sensory neuron carries the afferent information to the brain they are mainly pseudounipolar
 General visceral afferent neurons (from viscera)
 General Somatic afferent neurons (from locomotor system)
 Special senses afferent neurons (from eyes and ears etc.)
• Motor neurons carries motor impulses from brain or spinal cord to tissue level. They are of two types upper
& lower motor neurons
 General visceral efferent neurons (towards viscera)
 General Somatic efferent neurons (towards locomotor system)
• Interneurons connect sensory neurons to mo tor neurons

16. Supporting cells of brain
• There are six glial cell in nervous system
• Four in CNS and two in PNS
CNS PNS
Astrocyte Satellite cell
Oligodendrocyte Schwann cell
Microglia
Ependymal cell

17. Astrocytes (Star cell)
• Astrocyte are star shaped glial cells in brain and spinal cord. It interacts with up to 2 million neurons at a
time. They are the most abundant cells in the brain
• Have central body and some processes with foot plates in the end
2 types
• Fibrous astrocyte
 Long processes mostly unbranched and have vascular feet.
 Found in white matter of brain & spinal cord
• Protoplasmic astrocyte
 Short processes but are branched and have abundant of organelles and cytoplasm
 Seen in grey matter of brain and spinal cord

18. Functions
• Scaffold (covering neurons forming a meshwork around it)
 The number of astrocytes are more as compared to neurons
 Ratio of astrocytes to neurons is 5:1
 The astrocytes are present in CNS in the form of network
 They interlink with the help of footplates
• Reservoir of Glycogen
 In case of decrease ATP production in neurons, the astrocytes feeds neuron (contain glycogen and are
capable of gluconeogenesis and glycogenolysis) and provide nutrients
• Recycle neurotransmitters
 Excessive neurotransmitters are reuptake by axonal endings but at one point it is saturated
 Astrocytes now takes the charge and takes the excessive neurotransmitters and further supply it back to the
neurons

19. • Regulate neuronal communication by developing & stabilizing synapses (thrombosaponins I & II, Hevin,
Glypicans 4 & 6 – help in recruiting ampa receptors that makes synapses more active)
• Promote myelinating activity of oligodendrocytes
• Forms BBB
 The foot processes of astrocytes binds the junction of endothelium and prevent passage of various
substances forming blood brain barrier
 Mostly lipid soluble substances are permeable to this barrier
 Protein are not allowed to enter as they may stimulate any neuron
 There are places in the brain where blood brain barrier is absent is
 Area Postrema in medulla is devoid of BBB because in presence
of toxins it stimulate chemotactic centre in midbrain and causes vomiting
 Osmoreceptors around the hypothalamus checks hydrogen ion level,
electrolyte imbalance and accordingly stimulate posterior pituitary
 Hypothalamic-Pituitary axis

20. • Glial scar (repairs the damage)
 In case of injury, the astrocytes reaches the affected site and prevents blood loss
• Homeostasis (balance ion concentration in the brain)
 Rich in hydrogen ions
 Astrocytes can efflux and influx hydrogen ion
• Potassium buffer
 Membrane of the neuron has potassium channel that leaks out the potassium
 Sodium-potassium ATPase to counter balance the loss where in there is influx of two potassium ion and
efflux of 3 sodium ion
 Increase of potassium outside the cell, brings the potassium inside, exiting the neuronal cell
 In order to prevent this, astrocytes takes up the extra potassium and stores it

21. Microglia
• Microglia are the macrophages of the brain that broadly function to destroy pathogens and scavenge dead or
dying cells
• They form the main form of active immune defence in CNS. They travel within the CNS & perform different job
according to the need.
• Types: 1. Resting/Ramified microglia stays at one place and has a small cell body and a thin projections that r
monitoring or sensing the local environment. (express to IL10 & TGFß)
• 2. Reactive/activated microglia are highly motile (express to IL-1ß)
• 3. Phagocytic microglia
• Microglia dysfunction (area of research in Alzheimer’s disease)

22. • Synaptic Pruning- Clean up xtra synapses in early childhood
Receptors usually have sialic acid to protect them from phagocytosis but an enzyme released by microglia c/a
neuraminidase cleaves it and through series of reaction leads to phagocytosis. It also chews neurons that have
no CD200 or CD47 molecules.
• Scavenging property/ housekeepers
Very sensitive to small change in the environment. Sense any foreign material, damaged cells, apoptotic cells,
plaques, cleans dead cells or debris or engulf any foreign material
• Phagocytosis and promote inflammation
During the inflammation or injury to brain there is rise in microglia that pull their branches and increase their
cell body and multiply to increase its no. to fight against infection by secreting IFN-ɤ.

23. • Cytotoxicity
Apart from phagocytosis it releases variety of cytotoxic substances eg. ROS H2O2, NO, that directly damages cell.
Protease cytokine like IL1 causes demyelination of neuronal axons. Also IL1 inhibits IL10 and TGFß
• Antigen presenting cell and releases protein called cytokines (IL8) that help T cell to enter brain and fight
infection.
• Promotion of repair
Finally, they signal astrocyte to repair and heal the tissue, astrocyte releases IL10 and TGFß which is sensed by
resting microglia that stops further inflammation

24. Ependymal cells
• Neuroepithelial lining of the ventricular system of the brain and the central canal of the spinal cord.
• Contains cilia and microvilli on its surfaces. Cilia helps in moving CSF while microvilli helps in reabsorption of
CSF.
• Ependymal cells surrounded by blood vessels are called as Choroid Plexus that produces and regulates CSF.
• Neuro-regeneration: a recent study observed that ependymal lining might be a source of cells which can be
transplanted into the cochlea to reverse hearing loss.
• SATELLITE GLIAL CELL
These are the astrocytes of PNS

25. OLIGODENDROCYTES
Signals are needed to send at farthest tissue within a given limit of time and myelin sheath helps in the same.
From where does this myelin comes from?
Again Glial cell – Oligodendrocyte are the last cells to form in our brain (25-30yrs).
• They produce certain proteins (BDNF, IGF1) that helps neuron grow and forms synapses.
• These cells have a special lipid membrane that helps in forming myelin sheath around neurons.
• This myelin sheath provide support and insulation to axons
• 1 oligodendrocyte extends its process to approx. 50 neurons
SCHWANN CELLS
• Glia of PNS
• Wrap around axons in PNS i.e. does myelination

26. Na/K ATPase
Leaky K ion Channel
Leaky Na ion Channel
Resting potential
• Na/K ATPase
 It efflux 3 Na ions and influx 2 K ions
 Net change is loss of 1 cation
 Responsible for minor change in electronegativity
(approx. -5mV)
• Leaky Na ion channel
 Concentration of sodium ion is more outside the cell
so there is less efflux of Na+ ion, thus less change in
electronegativity
• Leaky K ion channel
 Potassium ion are usually present with anion
 Concentration gradient is also favourable
 Efflux of K+ ion results in generating electronegativity
3 Na+
2 K+
K+
K+
K+
K+
Anions
Anions
Anions
Anions
Na +
Na +
Na +
Na +

27. G- Protein coupled
Receptor
Ligand gated K/Cl ion
channel
Ligand gated Na/Ca
ion channel
Graded Potential
• Ligand gated Na/Ca ion channel (excitatory postsynaptic
potential) stimulate under the influence of glutamate
• Ligand gated K/Cl ion channel (Inhibitory postsynaptic potential)
stimulate under the influence of GABA
• G Protein coupled receptor stimulate under the influence of
protein, lipids etc.
Na +
Na +
Na +
-70mV
↓
-55mV

28. Voltage gated Ca ion
channel
Voltage gated K ion
channel
Voltage gated Na ion
channel
Action Potential
• Voltage gated Na ion channel (responsible for depolarization)
• Voltage gated K ion channel (responsible for repolarization)
• Voltage gated Ca ion channel (release of neurotransmitter)
+30
↑
-10mV
↑
-55mV
↑
-70mV
+30
↓
-10mV
↓
-55mV
↓
-70mV