2. Nervous tissue

4. Morphology examples

5.  Conducts electrical impulses (signals) to the
CNS & transmits impulses from the CNS to
various structures of the body
 Conveys information from one area to
another
Neural tissue

6. Morphogenesis of the neural tissue
includes:
 Proliferation;
 Determination & differentiation;
 Address migration of cells;
 Address growth of processes of neurons;
 Formation of intercellular junctions -
synapses;
 Apoptosis.

7. Neurulation

8. Cells in the neural tube

9. Ependymal
(inner) layer
Cambial cells
Ependymal cells
Mantle
layer
Neuroblasts
Glioblasts
Neurons
Astrocytes
Oligodendrogliocytes
Marginal
layer
White matter of CNS organs

10. Gray matter
(cell bodies)
White matter
(myelinated axons)

11. Neural tube
• CNS (brain
&spinal cord)
Retina of the
eye
Olfactory
organ
Neural crest
• Neural ganglia
(spinal &cranial;
autonomic)
• Neurolemmocytes
Adrenal medulla
Diffuse endocrine
cells
Pigmental cells
Cells of arachnoid &
pia mater
Placodes
• Sensoepithelial cells
of organ of Corti &
equilibrium
Receptor cells of
taste organ
Epithelium of lens

12.  Neurons
Generate &Transmit nerve impulses
 Neuroglia
Support neural tissue
Help supply nutrients to neurons
Protect neurons
Form barriers
Neural tissue cells

13. Morphological classification of
neurons - based on number of processes found on
cell body
 Unipolar
 Bipolar
 Multipolar
 Pseudounipolar

14. Unipolar neurons
 Have only one axon
 Rare

15. Pseudounipolar
neurons
 Have a single process that
extends from the cell body &
subsequently branches into an
axon & dendrite
 Sensory neurons – located
mainly in spinal & cranial ganglia

16. Bipolar neurons
 2 processes. Have a
single dendrite and an axon
 Are present in some sense
organs: retina, spiral
ganglion.

17. Multipolar neurons
 >2 processes. Have two or more
dendrites and one axon
 Most common type of neuron.
>99% of neurons

18. Functional classification of neurons
 motor neurons - efferent (conduct impulses from CNS
to other neurons, muscles or glands);
 sensory neurons - afferent (receive stimuli from the
internal & external environment). Conduct nerve
impulses to the CNS.
 interneurons act as connectors of neurons in chain.
They most commonly connect sensory & motor neurons.
 secretory neurons
- neurons of hypothalamus: supraoptic & paraventricular
nuclei – neurons produce hormones: vasopressin &
oxytocin);
- all neurons produce neurotransmitters of synapses.

19. Nervous
Tissue

20. Sensory – interneuron – motor neuron

21. Neurons
 Functional unit of nervous system
 Special neuronal characteristics
Convey APs (excitable)
Longevity
Do not divide
High metabolic rate

22. Neuron structure
 Cell membrane with Na+-K+ pumps, that
maintain the necessary ion gradients.
 Nucleus with one prominent nucleolus
(“owl-eye” nucleus)
 Cytoplasm with various cytoplasmic
organelles & inclusions, & cytoskeletal
components

23. Neuron has
 Cell body (perikaryon, soma)
 Processes:
 Only one axon
 One & more dendrites

25. Nucleus with
Nucleolus
Parts of a Neuron
Axons or
Dendrites
Cell body
Neuroglial cells

26. Neuron structure Cell body (perikaryon or
soma)
 single nucleus with
prominent nucleolus
 Nissl bodies
(chromatophilic
substance) are stained
basophilic
 rough ER & free
ribosomes
(polysomes) for
protein synthesis
 Golgi complex
 Mitochondria
 Lysosomes

27. Microtubules (neurotubules) move material
inside cell
Neurofilaments (specific type of intermediate
filaments) give cell shape and support
Microfilaments (actin) associated with the cell
membrane
Neurofilaments & neurotubules form
neurofibrils – is artefact. Neurofibrils appear at
time of slide preparing & can be distinguish
inside of neurons
Lipofuscin pigment clumps (harmless aging)
Lipid inclusions
 Cell processes = dendrites & axon

28. Perikaryon or soma
Cell body is location for most protein synthesis
neurotransmitters & repair proteins

30. Dendrites
 Conduct impulses towards the
cell body
 Typically short, highly branched
 Surfaces specialized for
contact with other neurons
(spines) – increase the area
useful for synapse formation
 Have arborized terminals –
permit a neuron to receive
stimuli at the same time from
many other neurons
 Contains neurofibrils & Nissl
bodies

31. Axon Conducts impulses away from
cell body
 Long, thin cylindrical process of
cell
 Arises at axon hillock – a
region of the soma that lacks
rER & ribosomes but contains
many neurotubules &
neurofilaments
 May has collaterals (branching
at right angles from the main
trunk)
 Axon terminals (many small
branches from which impulses
are passed to another neuron
or other type of cell)
 Swollen tips called synaptic

32. Transport
 Dendritic – the movement of
substances & organelles through the
dindrites
 Axonal - the movement of
substances & organelles through the
axon

33. Axonal Transport
 Axonal transport system moves substances
slow axonal flow
 movement in one direction only -- away from cell body
 movement at 1-5 mm per day
fast axonal flow
 transports in either direction
 at 100-500 mm per day
 moves organelles & materials along surface of
microtubules
 for use or for recycling in cell body
•Anterograde transport – carries material away from the soma
•Retrograde transport – carries material toward the soma for
reutilization, recycling, or degradation

34. Neuroglia
Macroglia
 Astrocytes
 Oligodendrocytes
 Ependymal cells
Microglia
 Neuroglia of CNS: astrocytes, oligodendrocytes,
ependymal cells, microglia
Neuroglia of PNS: neurolemmocytes (Schwann cell),
satellite cells

35. Neuron and Neuroglia

36. CNS Neuroglia
 Astrocytes
 protoplasmic (CNS gray
matter)
 fibrous (CNS white
matter)
Function:
1. scavenge ion & debris
(wastes) from neuron
metabolism & supply
energy for metabolism.
2. Provide structural support
for nervous tissue
3. Form a protective barrier
between pia mater & the
nervous tissue of the brain
& spinal cord
4. Form scar tissue after
injury to the CNS

38. Neuroglia of CNS
 Astrocytes
 Promote tight junctions
to form blood-brain
barrier
1. Endothelium of the
capillary (between
endothelial cells there
are tight junctions)
2. basement membrane
of endothelium
3. perivascular
membrane – is formed
by foot processes of
astrocytes

39. Blood-brain barrier
1 – endothelium; 2- basement membrane; 3 – astrocyte’s body, 4 –
foot processes of astrocyte; 5 – neuron, 6 – neuron’s processes; 7-
oligodendroglial cell

41. Neuroglia of CNS
 Ependymal Cells
 Line ventricles of the
brain, spinal cord
central canal, choroid
plexus
 Secrete & move liquor
 Form blood-liquor
barrier:
1. Endothelium of
capillary
2. Basement membrane
of endothelium
3. Loose connective
tissue
4. Basement membrane
of ependymal cells
5. Ependymal cells

43. Oligodendrocytes
 Produce the
myelin sheath
which provides
the electrical
insulation for
certain neurons
in the CNS
Neuroglia of
CNS

45. Neuroglia of CNS
 Microglia
Specialized
macrophages
Ag-presentation
Has mesenchymal
origin

46. Supporting cells in the PNS
 Satellite cells
 Schwann cells / neurolemmocytes

47. Neuroglia of PNS
 Schwann cells or neurolemmocytes
 Wrap around portion of only one axon to form myelin sheath
 Satellite cells are flattened cells
 Surround neuron cell bodies in ganglia, provide support and
nutrients

48. Satellite Cells

50. The End

51. Nerve fibers
 Myelinated fibers
 Unmyelinated fibers

52. Unmyelinated Myelinated
Localization
Mostly in the autonomic NS In the CNS and PNS
Speed of the conduction of the nerve impulse
low (0,5-2 m/s) High (5-120 m/s)
Nerve fiber of the cable type
(cytoplasm of the Schwann cell can
contains 10-20 axons of different
neurons)
Nerve fiber contains only 1 axon. But
in tne CNS 1 oligodendrocyte can takes
part in the process of myelinization
until 40-50 nerve fibers.
Structural components
1.axon (many axons)
2.cytoplasm of the Schwann cell +
mesaxon (mesaxons)
3.basement membrane
1.axon
2.myelin sheath with Schmidt-
Lanterman clefts and node of Ranvier.
3.cytoplasm and nucleus of the
Schwann cell.
4.basement membrane.
Conduction of the nerve impulse is
continuous.
Conduction of the nerve impulse is
salutatory (from the node to node of
Ranvier – nerve impulse jumps)

53. Myelinated and Unmyelinated
Axons

54. Unmyelinated nerve fibers

55.  Axons surrounded by a lipid & protein
covering (myelin sheath) produced by
Schwann cells.
 Myelin sheath is composed of multiple
layers of Schwann cell membrane
wrapped concentrically around the
axon.
 The myelin sheath is segmented
because it is formed by numerous
Schwann cells.
 The junctions where two adjacent
Schwann cells meet is devoid of
myelin.
 gaps called nodes of Ranvier
 Areas of incomplete fusion of the
Schwann cell membrane occur, &
small amounts of Schwann cell
cytoplasm are trapped between the
membranes – Schmidt-Lanterman
clefts (defects in the myelin
formation)
Myelinated nerve fiber

56. Schmidt-
Lanterman clefts

58. Myelin
sheath

59. Myelination in the CNS
Myelin sheaths
are formed by
oligodendrocytes

60. Myelination in the PNS
Myelin sheaths are formed
by Schwann cell

61. Myelin Sheath
 Whitish, fatty (protein-lipid), segmented
sheath around most long axons
 It functions in:
Protection of the axon
Electrically insulating fibers from one another
Increasing the speed of nerve impulse
transmission

62. Myelin Sheaths

63. Nodes of Ranvier
 Gaps in the myelin sheath between
adjacent Schwann cells
 They are the sites where collaterals can
arise

64. Nodes of Ranvier

65. Conduction of nerve impulse
A – in the unmyelinated nerve fiber (continuous)
B – in the myelinated nerve fiber (salutatory)

67. Nerve endings
Functionally they can be divided into 3 groups:
 synapses – provide the connection between
neurons;
 efferent (motor) endings – transmit signals from
the NS to the working organs (muscles, glands);
are present on the axons.
 receptor (sensitive) endings – receive the
irritation from the external environment and from
the internal organs; are present on the
dendrites.

68. Electrical
In mammals are rarely
present. They are as nexus
– provide the passive
transport of the electric
current through the cleft
from the cell to other in the
both directions and without
delay.
Chemical
Mostly distributed. The conduction of the nerve
impulse is determined by the special substance -
neurotransmitters.
The conduction of the nerve impulse is only in
the one direction and with delay.
The are divided into:
Axodendritic, occurs between axons and
dendrites
Axosomatic, occurs between axons and the cell
body
Axoaxonic, occurs between axons and axons
Dendrodendritic, occurs between dendrites and
dendrites.
Synapses are divided into:

69. Synapses
 Presynaptic neuron
 Postsynaptic neuron

71. Synapses
 Axodendritic synapses
 Axosomatic synapses
 Axoaxonic synapses
 Dendrodendritic synapses

73. Synapse structure
 Presynaptic element
Axon terminal
Synaptic vesicles
Neurotransmitters
Mitochondria
 Synaptic cleft
 Postsynaptic
elements
NT receptors
May generate AP

75. Synaptic
Transmission
 An AP reaches the
axon terminal of the
presynaptic cell and
causes V-gated Ca2+
channels to open.
 Ca2+ rushes in, binds
to regulatory proteins &
initiates NT exocytosis.
 NTs diffuse across the
synaptic cleft and then
bind to receptors on
the postsynaptic
membrane and initiate
some sort of response
on the postsynaptic
cell.

76. Efferent nerve endings
Motor
Are present in the striated and
smooth muscles.
By structure they are like synapses,
but there are some features: nearly
to the muscle fiber the axon loses
the myelin sheath and gives some
small branches. They are covered
by the Schwann cells and
basement membrane.
The transmission of the excitation
is provided by the neurotransmitter
- acetylcholine.
Secretory
Are present in the glands
Can make next influences:
- hydrokinetic (mobilization of
the water);
- proteokinetic (secretion of the
proteins);
- synthetic (to increase the
synthesis);
- trophic (to maintain the normal
structure and function).

77.  Motor unit
 One neuron
 Muscle cells stimulated
by that neuron
• Neuromuscular
junctions – association
site of nerve and
muscle

80. Receptor nerve endings
 exteroreceptors (receive the signals from
the external environment). They are: visual,
auditory, olfactory, taste, tactile receptors.
 interoreceptors. They are divided into
visceroreceptors – receive signals from
the inner organs; and proprioreceptors –
receptors of the locomotor system.

81. Physiological classification of the
receptor nerve endings
 mechanoreceptors (pressure, vibration)
 chemoreceptors (taste, smell)
 thermoreceptors (cold, warm)
 pain receptors

82. Morphological classification
Receptor nerve endings
Free(simple)
They are consists of
terminal branches of the
dendrites of the sensory
neuron.
They provide the
perception of the pain,
cold, warm, tactile
signals.
They are present inside of
the epithelium and in the
loose connective tissue,
which is located beneath.
It is consists of only of the
dendrite.
Restricted (compound)
Encapsulated
They are surrounded by the
connective tissue capsule.
Structure:
branches of the dendrite
surrounding Schwann cells
connective tissue capsule.
Examples:
Vater-Pacini corpuscles
Meissner’s tactile corpuscles
Ruffini’s curpuscles
Bulb of Krause
Neuromuscular spindles
Tendon organ of Golgi
Unencapsulated
They are consist of the
branches of the
dendrites that are
surrounded by the
Schwann cells.
They are present in
the dermis of the skin
and in the lamina
propria of the tunica
mucosa.

83. Free nerve endings
(pain, temperature,
light touch)
Merkel endings (touch) Pacinian corpuscle
(vibration, deep pressure)
Krause’s end
bulb (touch)
Meissner’s
corpuscle (touch)
Ruffini’s corpuscle
(stretch)
(Fibroblasts,
collagen,
fluid)
(Collagen
fibers)
Receptor nerve endings

84. Free nerve endings

85. Meissner corpuscle

86. Vater-Pacini
corpuscle

87. Pacinian corpuscle

88. Neuromuscular spindle

89. Vater-Pacini corpuscles – are present on the connective
tissue of the skin and inner organs. They are responsible for the
sensation of the pressure and vibration.
Meissner’s tactile corpuscles - are located in the papillary
layer of the dermis in skin, mostly: tips of fingers, lips, nipple
and area which is around.
Ruffini’s curpuscles – are located in the connective tissue of
the skin and in the capsules of the articulations. Take in
pressure.
Bulb of Krause – is present in the papillary layer of the dermis,
lamina propria of the tunica mucosa in the oral cavity. It is
mechanoreceptor.
Neuromuscular spindle – receptors of the sprain of the
muscle fibers. It has motor and sensory innervations.
Tendon organ of Golgi – receptor of the sprain. It is located in
the places where the skeletal muscle fibers join to the tendon.

90. Good bye! ☻