Nervous sistem

1. Nervous sistem

2. The central nervous system contains

Neurons – the nerve cells
Neuroglia – the connective tissue of the
nervous system
The cells of meninges – the cover of the
central nervous system
Blood vessels
Nerves

3. The neuron

= the functional and structural units of
nervous system.
- specialised for reception, integration,
transfromation and onward transmission.
Cell body or soma (nucleol with
nucleolus and cytoplasm with Nissl
bodies)
Dendrites
Axon

4.

5.

6. Impulse travel

In the dendrite the nerve impulse always
travels towards cell body.
In the axon the impulse traveles away
from the cell body.
The axon ends in many ramifications
(flower buchet) , and each has a terminal
button.
In the terminal button – small blisters
with chemical mediator

7. Types of neurons

8.

Multipolar – make almost the entire
neuronal population of central nervous
system (brain & spinal cord)
Bipolar – sensory neurons ( olfactory,
visual, auditory, vestibular)
Unipolar – has a single process which
divides into two (axon and dendrite). Are
found in dorsal nerve root ganglia,
sensory ganglia of cranial nerves. (the
nucleus of trigeminal 5 nerve is unipolar)

9. According to length of axons

Golgi type 1 with long axon (axon leaves
CNS)
Golgi type II with short axon (axon
remains within CNS)

10. Sheath’s of the axon

Myelin – gives Ranvier
nodes - impulse jumps
Sheat of Schwann cell secrete myelin. Each cell for
each cilinder of myelin.
Conjunctive sheat Henle –
for strength
Sheath’s of the axon

11.

In the gray matter the neurites don’t have
myelin and Schwann sheat.
They get it after they enter into the white
matter (first myelin sheat and after it
formes the periferic nerve it gets the
Schwann sheat)

12. Depolarizations sites

13. Classification of nerve fibers

Tipe A – myelinated
- according to functional
A:
Motor alpha –somatic - for the fast skeletal
muscle
Motor beta – somatic - for the slow
skeletal muscle
Motor gamma - fibers of the muscle
effector spindles

14. Classification of nerve fibers

B: muscle sensory nerve fibers
C: cutaneous sensory nerve fibers
Type B - myelinated
leading sensitivity exteroceptors,
preganglionic autonomic fibers
Type C – nonmyelinated
postganglionic autonomic fibers

15. Synapse

= is a structure that permits a neuron (or
nerve cell) to pass an electrical or chemical
signal to another neuron
Or
= the communication from a neuron to any
other cell type, such as to a motor cell,
although such non-neuronal contacts may
be referred to as junctions.

16. Synapse

17. Synapse

There are two fundamentally different
types of synapses: chemical and electrical
synapse
In a chemical synapse, electrical activity in
the presynaptic neuron is converted (via
the activation of voltage-gated calcium
channels) into the release of a chemical
called a neurotransmitter that binds to
receptors located in the plasma
membrane of the postsynaptic cell.

18. Chemical synapse

Chemical synapses can be classified
according to the neurotransmitter released:
glutamatergic (often excitatory),
GABAergic (often inhibitory),
cholinergic (vertebrate neuromuscular
junction),
adrenergic (releasing norepinephrine).

19. Electrical Synapse

In an electrical synapse, the presynaptic
and postsynaptic cell membranes are
connected by special channels called gap
junctions or synaptic cleft that are capable
of passing an electric current, causing
voltage changes in the presynaptic cell to
induce voltage changes in the postsynaptic
cell. The main advantage of an electrical
synapse is the rapid transfer of signals
from one cell to the next.

20. Structure of a typical chemical synapse

neurotransmitter
Synaptic
vesicle
Voltagegated Ca++
channel
Postsynaptic
density
Neurotransmitter
transporter
receptor
Axon
terminal
Synaptic
cleft
Dendrite

21. Types of interfaces Synapses can be classified by the type of cellular structures serving as the pre- and post-synaptic

components.

22. Synapse - Role in memory

a role in the formation of memory.
the connection between the two neurons
is strengthened when both neurons are
active at the same time, as a result of the
receptor's signaling mechanisms.

23. Neural pathway

A neural pathway, is a series of neurons
connected together to enable a signal to be
sent from one brain region to another.
Neurons are connected by a single nerve
fibre or by bundles of nerve fibres known
as tracts.

24. Neural pathway

A neural pathway that serves to connect
relatively distant areas of the brain or
nervous system is a bundle of neurons,
known collectively as white matter
A neural pathway that spans a shorter
distance between structures, such as most
of the pathways of the major
neurotransmitter systems, is usually called
grey matter

25. Bundles and nerve pathways

Afferent pathways, sensory or upward
At leats 3 neurons: 1 in spinal ganglia
II in spinal cord
III in thalamus
Efferent pathways, descending: 2 neurons:
- one central motor neuron in the cortex
- one peripheral motor neuron in the spinal
cord or in the cerebral trunk.