Nervous sistem презентация

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

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

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

Types of neurons

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)

According to length of axons
Golgi type 1 with long axon (axon leaves CNS)
Golgi type II with short axon (axon remains within CNS)

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

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)

Depolarizations sites

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

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

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.

Synapse

Synapse
There are two fundamentally different types of synapses: chemical and electrical synapse
In a chemical synapseIn a chemical synapse, electrical activity in the presynaptic neuron is converted (via the activation of voltage-gated calcium channelsIn 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 neurotransmitterIn 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.

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

Electrical Synapse
In an electrical synapseIn 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.

Structure of a typical chemical synapse
Axon terminal
Dendrite
Synaptic cleft
neurotransmitter
Synaptic
vesicle
Voltage-
gated Ca++
channel
Postsynaptic
density
Neurotransmitter
transporter
receptor

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

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.

Neural pathway
A neural pathway, is a series of neurons, 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, 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.

Neural pathway
A neural pathway that serves to connect relatively distant areas of the brainA 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 systemsA 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