1 nervous system dr :waheeb aggad. 2 nervous system 1-it is a system which monitor the changes in...

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NERVOUS NERVOUS SYSTEMSYSTEM

DR :WAHEEB AGGADDR :WAHEEB AGGAD

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Nervous systemNervous system1-It is a system which monitor the changes 1-It is a system which monitor the changes

in the external and internal environment in the external and internal environment and start dealing with themand start dealing with them

.2-It is formed of highly specialized nerve .2-It is formed of highly specialized nerve cells (neurons) which can: cells (neurons) which can:

receive stimuli (from receptors scattered receive stimuli (from receptors scattered all over the body)all over the body)

and deal with themand deal with themand finally send the proper impulses to the and finally send the proper impulses to the

effectors which could be muscles or effectors which could be muscles or glands.glands.

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N.BN.B3)The C.N.S 3)The C.N.S can't can't regenerate if regenerate if injured.injured.

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4) .The functional unit of 4) .The functional unit of the Nervous System is the the Nervous System is the

neuron.neuron. NeuronNeuron is the term given to the nerve is the term given to the nerve

cell and all its processes. It is formed of :cell and all its processes. It is formed of : AA) ) cell bodycell body has nucleus has nucleus B) two types of processes, B) two types of processes, called an axon and dendrites. called an axon and dendrites. 1) 1) the axonthe axon is, single, the longest process of is, single, the longest process of

the cell body ,carries nervous impulses away the cell body ,carries nervous impulses away from the cell body. out side the CNS, the from the cell body. out side the CNS, the axons(nerve fibers) runs in groups forming axons(nerve fibers) runs in groups forming the different nerves of the bodythe different nerves of the body

2)Dendrites2)Dendrites are multiple ,the short are multiple ,the short processes of the cell body, which carry processes of the cell body, which carry impulses to wards the cell body.impulses to wards the cell body.

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Divisions of the Nervous Divisions of the Nervous SystemSystem

The nervous system is divided The nervous system is divided intointo

two main parts:two main parts: 1)1) The central nervous system The central nervous system 2)2) The peripheral nervous system The peripheral nervous system

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1-The central nervous 1-The central nervous systemsystem,,

1-The central nervous 1-The central nervous system system is the part of N.S is the part of N.S which is protected by which is protected by bones ,it is consists of: bones ,it is consists of:

a) The braina) The brain b) spinal cord b) spinal cord

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A) The brainA) The brain It isIt is formed of : formed of : a) cerebrum ( the 2a) cerebrum ( the 2 cerebral cerebral

hemispheres+ the interbrain).hemispheres+ the interbrain). b) b) Brain stem: which includes:Brain stem: which includes:

Midbrain ( upper part)Midbrain ( upper part) Pons (middle part)Pons (middle part) medulla oblongata (lower part)medulla oblongata (lower part)

c)cerebellumc)cerebellum

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A) The brainA) The brainit is it is coveredcovered by 3 meninges by 3 meninges : :

1-Dura (the outer layer )1-Dura (the outer layer )2-arachnoid (the middle)2-arachnoid (the middle)3-the pia (the inner) 3-the pia (the inner) matters.matters.

It It contains cavitiescontains cavities (Ventricles).(Ventricles).

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A) The brainA) The brain In cross sections, it showsIn cross sections, it shows:: a)a)Grey matterGrey matter :dark areas which contains the cell :dark areas which contains the cell

bodies .bodies . The grey matter on the surface of the The grey matter on the surface of the

cerebrum is called the cerebrum is called the cerebral cortexcerebral cortex . .

The term The term nucleus nucleus is used to describe is used to describe any collection of cell bodies which any collection of cell bodies which perform the same function.perform the same function.

b) b) White matterWhite matter :light areas which contain nerve :light areas which contain nerve fibers (axons) .fibers (axons) .

The fibers run inside the C.N.S .as bundles or tracts.The fibers run inside the C.N.S .as bundles or tracts.

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B) The spinal B) The spinal cordcord

The spinal cord The spinal cord

CoveredCovered by3 meninges like by3 meninges like the brain.the brain.

Contains cavityContains cavity called called the central canal . the central canal .

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In cross sectionIn cross section ,it shows: ,it shows: a) Grey mattera) Grey matter: it is arranged in the shape of : it is arranged in the shape of

butter fly or like letter H. butter fly or like letter H. It projects as 2 dorsal horns (contain sensory It projects as 2 dorsal horns (contain sensory

neurons ) &2 ventral horns (contain motor neurons ) &2 ventral horns (contain motor neurons) .neurons) .

A third lateral horn is found only in the A third lateral horn is found only in the segments which give autonomic outflow.segments which give autonomic outflow.

B) White matterB) White matter : surrounds the grey matter : surrounds the grey matter and contains nerve fibers which run as tracts. and contains nerve fibers which run as tracts.

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The cord is divided into segments (31):The cord is divided into segments (31): a-cervical segments:8.a-cervical segments:8. b-Thoracic segments :12.b-Thoracic segments :12. c-Lumber segments :5.c-Lumber segments :5. d- Sacral segments :5.d- Sacral segments :5. e- Single Coccygeal . e- Single Coccygeal . N:B.: The right and left parts of the C.N.S. N:B.: The right and left parts of the C.N.S.

are connected together by nerve fibers are connected together by nerve fibers called commissures.called commissures.

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2-The peripheral nervous 2-The peripheral nervous systemsystem

The peripheral nervous systemThe peripheral nervous system, It is not , It is not protected by bones , protected by bones ,

It is divided functionally intoIt is divided functionally into : : a-Somatic nervous a-Somatic nervous

systemsystem :carries sensations and controls :carries sensations and controls skeletal muscles .skeletal muscles .

b-Autonomic nervous b-Autonomic nervous systemsystem :Controls smooth muscle ,heart :Controls smooth muscle ,heart &glands .&glands .

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A-The Somatic nervous A-The Somatic nervous SystemSystem

The Somatic nervous System : The Somatic nervous System : which formed of :which formed of :

a) cranial nervesa) cranial nerves :12 pairs of :12 pairs of nerves which arise from the brain. nerves which arise from the brain.

b) spinal nervesb) spinal nerves: 31 pairs of : 31 pairs of nerves and their associated ganglia nerves and their associated ganglia which arise from the spinal cord ,which arise from the spinal cord ,aa pair arises from each segment. pair arises from each segment.

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a)Cranial Nervesa)Cranial Nerves There are 12 pairs of cranial nerves There are 12 pairs of cranial nerves

that leave the brain and pass that leave the brain and pass through foramina in the skull. through foramina in the skull.

All the nerves are distributed in the All the nerves are distributed in the head and neck except the Xth head and neck except the Xth (vagus), which also supplies (vagus), which also supplies structures in the thorax and structures in the thorax and abdomen. ) .abdomen. ) .

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B) Spinal NervesB) Spinal NervesA total of 31 pairs of spinal nerves leave the A total of 31 pairs of spinal nerves leave the

spinal cord and pass through spinal cord and pass through intervertebral intervertebral foraminaforamina in the vertebral column . in the vertebral column .

The spinal nerves are The spinal nerves are named named according to the region of the according to the region of the vertebral column with which they are associated:vertebral column with which they are associated:

8 cervical,8 cervical, 12 thoracic,12 thoracic, 5 lumbar,5 lumbar, 5 sacral, and5 sacral, and 1 coccygeal1 coccygeal. .

).).

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N:BN:B Q )There are eight cervical nerves and only Q )There are eight cervical nerves and only

seven cervical vertebrae and that there is one seven cervical vertebrae and that there is one coccygeal nerve and four coccygeal coccygeal nerve and four coccygeal vertebrae. WHY?vertebrae. WHY?

A) During development, the spinal cord A) During development, the spinal cord grows slowly than the vertebral column. In grows slowly than the vertebral column. In the adult, when growth STOPED, the lower the adult, when growth STOPED, the lower end of the spinal cord reaches inferiorly only end of the spinal cord reaches inferiorly only as far as the lower border of the first lumbar as far as the lower border of the first lumbar vertebra( L1vertebra( L1

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B) Spinal B) Spinal NervesNervesEach spinal nerve is Each spinal nerve is

connected toconnected to the spinal the spinal cord by cord by two rootstwo roots::

A) the anterior root andA) the anterior root andB) the posterior root.B) the posterior root.

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B) Spinal NervesB) Spinal Nerves1)The anterior root 1)The anterior root (Efferent fibers(Efferent fibers ) )

consists of: consists of: Motor fibersMotor fibers, arises , arises from the from the anterior horn of gray anterior horn of gray mattermatter of the spinal cord. of the spinal cord.

carrying motor impulsescarrying motor impulses from the from the central nervous system to skeletal central nervous system to skeletal muscle and cause them to contract muscle and cause them to contract

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B) Spinal NervesB) Spinal Nerves 2) The posterior root2) The posterior root (Afferent (Afferent

fibers)fibers) consists of consists of sensory fiberssensory fibers that are that are concerned with conveying information about concerned with conveying information about sensations ofsensations of( touch, pain, temperature, and ( touch, pain, temperature, and vibrations ) to the central nervous system, so vibrations ) to the central nervous system, so they are called they are called sensory fiberssensory fibers ,and ends in ,and ends in the dorsal horn of the gray matterthe dorsal horn of the gray matter of the of the spinal cord .spinal cord .

The cell bodies of these nerve fibers are The cell bodies of these nerve fibers are situated in a situated in a swelling on the posterior root swelling on the posterior root called the called the posterior rootposterior root ganglion ganglion

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B) Spinal NervesB) Spinal Nerves 3)posterior root 3)posterior root

ganglionganglion :each posterior :each posterior root carries posterior root root carries posterior root ganglion which contains an ganglion which contains an aggregation of cell bodies aggregation of cell bodies situated in a swelling.situated in a swelling.

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B) Spinal NervesB) Spinal Nerves At each intervertebral foramen, the At each intervertebral foramen, the

anterior and posterior roots unite toanterior and posterior roots unite to form a form a TrunkTrunk of spinal nerve Here, of spinal nerve Here,

the motor and sensory fibers become the motor and sensory fibers become mixed together, so that a spinal nerve mixed together, so that a spinal nerve is made up of a mixture of motor and is made up of a mixture of motor and sensory fibers .sensory fibers .

On emerging from the foramen, the On emerging from the foramen, the spinal nerve divides into 2 rami :spinal nerve divides into 2 rami :

. .

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B) Spinal NervesB) Spinal Nerves 1)Anterior ramus1)Anterior ramus : : it is a large mixed nerve . it is a large mixed nerve . The anterior ramus continues anteriorly to The anterior ramus continues anteriorly to

supply the supply the muscles and skin over the muscles and skin over the anterolateral body wall and all the muscles anterolateral body wall and all the muscles and skin of the limbs.and skin of the limbs.

It supplies those It supplies those eithereither directly directly oror after after plexuses formation with neighbouring ventral plexuses formation with neighbouring ventral rami .rami .

The ventral rami are connected to the The ventral rami are connected to the sympathetic chain by rami communicantessympathetic chain by rami communicantes

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B) Spinal NervesB) Spinal Nerves2)posterior ramus2)posterior ramus: : It is a smaller mixed nerve .It is a smaller mixed nerve . The posterior ramus passes The posterior ramus passes

posteriorly around the vertebral posteriorly around the vertebral column to supply column to supply the muscles the muscles and skin of the back.and skin of the back.

The dorsal rami The dorsal rami do not form do not form plexusesplexuses

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The Somatic nerve The Somatic nerve plexuses:plexuses:

The Somatic nerve plexuses: The Somatic nerve plexuses: Most of the ventral rami of the spinal nerves have great Most of the ventral rami of the spinal nerves have great

tendency to form nervous networks in which the nerve tendency to form nervous networks in which the nerve fibers exchanged between the neighbouring ventral rami . fibers exchanged between the neighbouring ventral rami .

At the root of the limbs, the anterior rami join one another At the root of the limbs, the anterior rami join one another to form complicated nerve plexuses. to form complicated nerve plexuses.

1- cervical 1- cervical 2-brachial plexuses: supply the skin &muscles of the upper 2-brachial plexuses: supply the skin &muscles of the upper

limbs.limbs.3- lumbar 3- lumbar 4-sacral plexuses supply the skin &muscles of the lower limbs.4-sacral plexuses supply the skin &muscles of the lower limbs. N.B.: the 12 thoracic ventral rami do not form N.B.: the 12 thoracic ventral rami do not form

plexus .plexus .

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Functionally, the nervous system can be Functionally, the nervous system can be further divided into :further divided into :

the somatic nervous system, which the somatic nervous system, which controls voluntary activities.controls voluntary activities.

the autonomic nervous system, the autonomic nervous system, which controls involuntary activities.which controls involuntary activities.

The nervous system, together with The nervous system, together with the endocrine system, controls and the endocrine system, controls and integrates the activities of the integrates the activities of the different parts of the body. different parts of the body.

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SUMARY TO N.SSUMARY TO N.S Central Nervous SystemCentral Nervous System The central nervous system is brain( cerebral hemisphere+The central nervous system is brain( cerebral hemisphere+Brain stem cerebellum )+spinal cord composed of large Brain stem cerebellum )+spinal cord composed of large

numbers of: a) nerve cells andnumbers of: a) nerve cells and b) their processes,b) their processes, c) supported by specialized tissue called neuroglia. c) supported by specialized tissue called neuroglia. the peripheral nervous system can be further dividedthe peripheral nervous system can be further divided

into :into : a-the somatic nervous systema-the somatic nervous system, which controls voluntary , which controls voluntary

activities. activities. a) 12 pairs of cranial nerves and a) 12 pairs of cranial nerves and b)31 pairs of spinal nerves and their associated ganglia.b)31 pairs of spinal nerves and their associated ganglia. b- the autonomic nervous systemb- the autonomic nervous system, which controls , which controls

involuntary activities.involuntary activities. The nervous system, together with the endocrine system, The nervous system, together with the endocrine system,

controls the activities of the different parts of body.controls the activities of the different parts of body.

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2-2-Autonomic Autonomic

Nervous Nervous SystemSystem

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2-Autonomic Nervous 2-Autonomic Nervous SystemSystem

2-Autonomic Nervous System2-Autonomic Nervous System The autonomic nervous system is the The autonomic nervous system is the

part of the nervous system concerned part of the nervous system concerned with the innervation of with the innervation of involuntary involuntary structuresstructures such as: such as: the heart, smooth the heart, smooth muscle , and glandsmuscle , and glands throughout the throughout the body .body .

It is distributed throughout theIt is distributed throughout the central central and and peripheral nervous system.peripheral nervous system.

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The autonomic systemThe autonomic system divided into two partsdivided into two parts

1)the sympathetic system .1)the sympathetic system .

2) the parasympathetic system2) the parasympathetic system. . Both systems have antagonistic Both systems have antagonistic

functions but they are functions but they are complementary to each other . To complementary to each other . To control the muscles & glands, control the muscles & glands,

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TheThe autonomic nervous system autonomic nervous system need 2 need 2 sets of neurons :sets of neurons :

1 - preganglionic neurons1 - preganglionic neurons : they carry : they carry the impulses from the CNS to ganglia out side the impulses from the CNS to ganglia out side the CNS .the CNS .

2 - Postganglionic neurons2 - Postganglionic neurons : they carry : they carry impulses from the ganglia to the smooth impulses from the ganglia to the smooth muscles and glands. muscles and glands.

A gangliaA ganglia means a collection of neurons means a collection of neurons (cell bodies ) out side the CNS .(cell bodies ) out side the CNS .

..In the ganglia the pre & Postganglionic In the ganglia the pre & Postganglionic neurons meet by making Synapse.neurons meet by making Synapse.

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1)the sympathetic 1)the sympathetic systemsystem

The Functions of the sympathetic part of the autonomic system:

prepare the body for an emergency,stress 3 f (fight ,freight,flight).

1. accelerates the heart rate,

causes constriction of the peripheral blood vessels, and raises the blood pressure.

2. Redistribution of the blood so that it leaves the areas of the skin and intestine and becomes available to the brain, heart, and skeletal muscle.

3. Dilatatios of the pupil.4. Stimulation of sphincters of gut .5. Erection of hairs .6. sweating

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Sympathetic SystemSympathetic System : : ItIt is formed of :is formed of : 1) pre ganglionic fibers1) pre ganglionic fibers:: Arise from neurons of the lateral Arise from neurons of the lateral

horn of thehorn of the The gray matter of the The gray matter of the spinal cord, in the following segment :spinal cord, in the following segment :

1)all thoracic segment1)all thoracic segment 2) the first and the second lumbar 2) the first and the second lumbar

segment ,SO,the name segment ,SO,the name thoraco thoraco lumber outflow lumber outflow

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the preganglionic the preganglionic fibersfibers

The axons of these cells leave the The axons of these cells leave the spinal cord in thespinal cord in the

anterior roots,anterior roots, nerve trunk ,ventral nerve trunk ,ventral ramus of the corresponding spinal ramus of the corresponding spinal nerve .nerve .

Finally ,the preganglionic fibers Finally ,the preganglionic fibers leave the leave the ventral ramus ventral ramus as the as the white white rami communicantes rami communicantes to the to the ganglia of ganglia of the sympatheticthe sympathetic chain. chain.

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Once the Once the preganglionic fiberspreganglionic fibers reach the ganglia in reach the ganglia in the sympathetic chain, the sympathetic chain, they may pass to the following they may pass to the following

destinations by dividing intodestinations by dividing into::

a- a- Ascending groupAscending group: These are fibers W make : These are fibers W make synapses with the cell bodies of upper ganglia synapses with the cell bodies of upper ganglia of the chain. of the chain.

b- b- Transverse groupTransverse group: These are fibers W make : These are fibers W make synapses with the cell bodies of same level synapses with the cell bodies of same level ganglia of the chain. ganglia of the chain.

c- c- descending groupdescending group: These: These are fibers W are fibers W make synapses with the cell bodies of lower make synapses with the cell bodies of lower ganglia of the chain. ganglia of the chain.

N.B.: SOME pre ganglionic fibers do not make N.B.: SOME pre ganglionic fibers do not make synapse with sympathetic synapse with sympathetic chain ,Instead ,they reach other distal chain ,Instead ,they reach other distal sympathetic ganglia ,e.g., Coeliac ganglion sympathetic ganglia ,e.g., Coeliac ganglion where they relay. where they relay.

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2-The postganglionic 2-The postganglionic nervenerve fibers fibers

The postganglionic nerveThe postganglionic nerve fibers: they are the axons of fibers: they are the axons of the cell bodies of sympathetic ganglia .the cell bodies of sympathetic ganglia .

They pass from the sympathetic ganglia to reach They pass from the sympathetic ganglia to reach different parts of the body by one different parts of the body by one of 3 methods :of 3 methods :

1) by rejoining the ventral &dorsal rami to be distributed 1) by rejoining the ventral &dorsal rami to be distributed via them.via them.

The connection between the ganglia &ventral rami are called The connection between the ganglia &ventral rami are called gray rami communicantes .gray rami communicantes .

They are distributed in the branches of the spinal nerves to They are distributed in the branches of the spinal nerves to supply the smooth muscle in the walls of blood vessels, the supply the smooth muscle in the walls of blood vessels, the sweat glands, and the erector pili muscles of the skin.sweat glands, and the erector pili muscles of the skin.

2)By passing along the blood vessels .2)By passing along the blood vessels .

3)By reaching the viscera directly.3)By reaching the viscera directly.

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3) Sympathetic 3) Sympathetic chainschains

1.1. . Sympathetic trunks are two ganglionated . Sympathetic trunks are two ganglionated nerve trunks that extend the whole length of nerve trunks that extend the whole length of the vertebral column the vertebral column

2.2. .There are 3 ganglia in each trunk of the .There are 3 ganglia in each trunk of the neck, 11 or 12 ganglia in the thorax, 4 or 5 neck, 11 or 12 ganglia in the thorax, 4 or 5 ganglia in the lumbar region, and 4 or 5 ganglia in the lumbar region, and 4 or 5 ganglia in the pelvis. ganglia in the pelvis.

3.3. The two trunks lie close to the vertebral The two trunks lie close to the vertebral column and end below by joining together column and end below by joining together to form a single ganglion, the ganglion to form a single ganglion, the ganglion impar.impar.

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2) Parasympathetic 2) Parasympathetic SystemSystem

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2) 2) The The Functions of the Functions of the Parasympathetic SystemParasympathetic System

parasympathetic part of the autonomic parasympathetic part of the autonomic system conserving and restoring energy. system conserving and restoring energy. i.e., i.e.,

rebuilding the body resources during rest :rebuilding the body resources during rest :1.1. They slow the heart rateThey slow the heart rate2.2. increase peristalsis of the intestine and increase peristalsis of the intestine and

glandular activity, and open the sphincters.glandular activity, and open the sphincters.3.3. constriction of the pupil.constriction of the pupil.NB .The hypothalamus of the brain controls the NB .The hypothalamus of the brain controls the

autonomic nervous system and integrates the autonomic nervous system and integrates the activities of the autonomic and activities of the autonomic and neuroendocrine systems, thus preserving neuroendocrine systems, thus preserving homeostasis in the body homeostasis in the body

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It is formed of: It is formed of: 1)1)The preganglionic fibers: The preganglionic fibers: They arise from CNS in 2 sites :They arise from CNS in 2 sites :

1.1. with the with the cranial nervescranial nerves number 10,9,7,3. number 10,9,7,3.

2.2. From the neurons of the lateral horn ofFrom the neurons of the lateral horn of sacral sacral spinal segments number 2,3,4.spinal segments number 2,3,4.

SO the name SO the name cranio -sacral outflowcranio -sacral outflow. leave the . leave the spinal cord in the anterior roots of the spinal cord in the anterior roots of the corresponding spinal nerves. They then leave corresponding spinal nerves. They then leave the sacral nerves and form the pelvic the sacral nerves and form the pelvic splanchnic nerves.splanchnic nerves.

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2 -peripheral ganglia:2 -peripheral ganglia: The preganglionic fibers synapse with The preganglionic fibers synapse with

cells in peripheral ganglia, which are cells in peripheral ganglia, which are usually situated usually situated close to the viscera close to the viscera they innervate. they innervate.

The cranial preganglionic fibers relay in (The cranial preganglionic fibers relay in (4 4 cranial Para sympathetic ganglia )the cranial Para sympathetic ganglia )the ciliaryciliary, pterygopalatine, submandibular, , pterygopalatine, submandibular, and otic ganglia .and otic ganglia .

The preganglionic fibers in the pelvic The preganglionic fibers in the pelvic splanchnic nerves relay in ganglia in the splanchnic nerves relay in ganglia in the hypogastric plexuses or in the walls of hypogastric plexuses or in the walls of the viscera.the viscera.

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3)3)The postganglionic The postganglionic fibersfibers::

The post ganglionic Para The post ganglionic Para sympathetic fibers (The sympathetic fibers (The axons of the cell bodies axons of the cell bodies inside the ganglia ) leave inside the ganglia ) leave the ganglia to reach their the ganglia to reach their targets.targets.

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N.B.N.B.

1) peripheral nerves can 1) peripheral nerves can regenerate if injuredregenerate if injured. .

2) peripheral nerves are either2) peripheral nerves are either : : a-Motora-Motor ( Efferent):if they carry ( Efferent):if they carry

orders ,e.g., to a gland or muscle.orders ,e.g., to a gland or muscle. b-Sensoryb-Sensory (Afferent) : if they carry (Afferent) : if they carry

sensations ,e.g., pain or touch.sensations ,e.g., pain or touch. c- Mixedc- Mixed: if they contain both motor : if they contain both motor

&sensory fibers .&sensory fibers .

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Clinical NotesClinical Notes Clinical Modification of the Activities of Clinical Modification of the Activities of

the Autonomic Nervous Systemthe Autonomic Nervous System Many Many drugs and surgical proceduresdrugs and surgical procedures that that

can modify the activity of the autonomic can modify the activity of the autonomic nervous system are available.nervous system are available.

For example, drugs can be administered For example, drugs can be administered to to lower the blood pressure by blocking lower the blood pressure by blocking sympathetic nervesympathetic nerve endings and causing endings and causing vasodilatation of peripheral blood vessels. vasodilatation of peripheral blood vessels.

In patients with In patients with severe arterial disease severe arterial disease affecting the main arteries of the lower affecting the main arteries of the lower limb. limb.

1 nervous system dr :waheeb aggad. 2 nervous system 1-it is a system which monitor the changes in...

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