Download Nervous System

Nervous
System
Parts of Nervous System
• Central Nervous • Peripheral
Nervous System
System
• 1- Cerebrospinal
• 1- Brain
nervous system(12
• 2-Spinal cord
CNs, 31 SNs)
• 2- Peripheral
Autonomic
Nervous System
Base
of
the
Brain.
Lateral surface of brain.
Cross
section of
spinal
cord.
Cranial nerves.
• Spinal nerves &
formation of
• Cervical plexus
• Brachial plexus
• Lumbar plexus
• Sacral plexus
Spinal Nerves
• 31 nerves connecting the
spinal cord and various body
regions.
• 8 paired cervical
nerves
• 12 paired thoracic
nerves
• 5 paired lumbar
nerves
• 5 paired sacral nerves
• 1 pair of coccygeal
nerves
Spinal Nerves
• The 2 roots join to
form a spinal nerve
prior to exiting the
vertebral column.
• Roots are short and
horizontal in the
cervical and thoracic
regions while they
are longer and more
horizontal in the
sacral and lumbar
regions.
• Almost immediately after emerging from its intervertebral foramen,
a spinal nerve will divide into a dorsal ramus, a ventral ramus, and a
meningeal branch that reenters and innervates the meninges and
associated blood vessels.
Cells of Nervous System
• 1- Neurons: Excitable cells
• 2- Supporting cells: Non-excitable cells
(Neuroglia & Ependyma and Schwann cells)
Neuroglia
Neuron
Neuron
• 1- Cell body
• 2- Cell processes- Dendrites and Axon
• Types of neurons (According to number of
processes)
a- Unipolar, eg: mesencephalic nucleus
b- Pseudo-unipolar, eg: sensory ganglia
c- Bipolar, eg: vestibular ganglia
d- Multipolar, eg: most common
(According to length of axon- Golgi type 1 &2)
Neuron.
Types of neurons.
Neuroglia
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1- Neuroglia cells
2- Ependymal cells
3- Capsular or satellite cells
4- Schwann cells
5- Different types of supporting cells
Neuroglial cells are : Astrocytes,
Oligodendrocytes, Glioblasts, Microglia.
Functions of glial & ependymal cells
•
•
•
•
•
•
•
1- Support to neurons
2- Insulation
3- Phagocytosis
4- Repair of damaged areas
5- Storing of neurotransmitters
6- Oligodendrocytes myelinate tracts
7- Ependymal cells concerned with
blood- brain barrier.
Reflex arc
• It is the basic functional unit of the
nervous system.
• A simple arc made up of
a- a receptor
b- a sensory or afferent neuron
c- a motor or efferent neuron
d- an effector
Reflex Arcs
• A reflex is a rapid, predictable
motor response to a stimulus.
Unlearned and involuntary.
• Example?
• Components of a reflex arc:
– Receptor  site of
stimulus
– Sensory neuron 
transmits afferent info to
CNS
– Integration center  1 or
more interneurons
– Motor neuron 
transmits efferent signals
to effector
– Effector  muscle or
gland
Nerves
• Peripheral nerves
• Spinal nerves -31pairs
8- cervical
12-thoracic
5-lumbar
5-sacral
1-coccygeal
• Nerve plexuses
Nerve fibers
• Nerve fibre is an axon with its covering
of myelin sheath. Myelinated fibers.
• Thinner axons (less then 1micron) do
not have the myelin sheth.
Nonnyelinated fibres.
• Both will have a neurolemmal sheath,
but tracts wont have it.
Myelin sheath formation.
Classification of Peripheral nerve fibres
• According to function,
1- Somatic efferent
2- General vicseral efferent
3- Special vicseral efferent
4- General somatic afferent
5- General vicseral afferent
6- Special vicseral afferent
7- Special somatic afferent
Classification of Peripheral nerve fibres
• According to Size & speed of conduction,
1- Group A fibres: Thick and fast
2- Group B fibres: Medium size and speed
3- Group C fibres: Thinnest and slowest
Degeneration and Regeneration of
Neurons
(Wallerian Degeneration)
Autonomic nervous system
• It controls the involuntary activities of
the body.
• It is having
a) Preganglionic fibres, b) The ganglia,
c) Postganglionic fibres
• Two types
1- Sympathetic system
2-Parasympathetic system
• Autono
mic
nervous
system.
• Multipolar
motor
neuron.
• Section of
spinal cord.
• Diagram of
spinal cord
with
anterior &
posterior
root.
Sympathetic system
• 1- It is known as thoracolumbar out flow
(T1 to L2 segment)
• 2- Preganglionic fibres (medulleted-white
rami communicantes) arise from lateral
column of spinal cord, emerge through
ventral rami and connected to the ganglia
of sympathetic chain.
• 3- From the ganglia postganglionic fibres
(nonmedullated-grey rami communicantes)
run for some distancebefore reaching the
organ of supply.
• 4- Sympathetic nerve endings are
adrenergic in nature (noradrenalinneurotransmetre)
• 5- Functionally sympathetic nerves are
vasomotor, stimulation leads to increased
blood supply to skeletal muscles, heart and
brain. Also causes dilation of pupil, pale
face, dry mouth, tachycardia, rise in blood
pressure, inhibition of hollow viscera, and
closure of peripheral sphincters.
• By this deals with emergencies or
emotional crises.
Parasymapathetic system
• 1- It is known as craniosacral out flow (brain-3rd, 7th,
9th and 10th CNs and S 2-4 segment)
• 2- Preganglionic fibres are very long, reaching up to
the viscera of supply. The ganglia situated on or near
the viscera, therefore postganglionic fibres are very
short
• 3- Parasympatetic nerve endings are cholinergic in
nature
• 4- Functionally, parasympathetic activity is seen
when the subject is fully relaxed. It leads constricted
pupil, flushed face, moist mouth, slow pulse, low
blood pressure, contraction of bladder and gut and
relaxing of peripheral sphincters.
Applied anatomy
• 1. Irritation of motor nerve causes muscular
spasm and sensory nerve causes tingling,
numbness and pain over the area of
distribution.
• 2-Damage to a motor nerve causes muscular
paralysis and sensory nerve causes
anaesthesia and analgesia.
• 3- Severe pain along the distribution of anerve
is neuralgia. Inflammation is neuritis.
• 4- Denervation leads to tropic changes in the
skin.