الرحيم الرحمن الله بسم

THE NERVOUS THE NERVOUS SYSTEM SYSTEM

FUNCTIONS AND FUNCTIONS AND ORGANIZATION ORGANIZATION

FUNCTIONSFUNCTIONS• collection of collection of

sensory inputsensory input• integrationintegration• motor outputmotor output

The function of the The function of the nervous system of all nervous system of all animals is to detect animals is to detect changes in the:changes in the: External or Internal External or Internal environments.environments.So, it bring about So, it bring about appropriate appropriate responses in Muscles,responses in Muscles,Organs and Organs and Glands. Glands.

ORGANIZATIONORGANIZATION

STRUCTURAL• CNSCNS• PNSPNS

FUNCTIONAL• sensory division sensory division

(Afferent)(Afferent)• motor division motor division

(Efferent)(Efferent)– autonomicautonomic– somaticsomatic

Prof. Saeed Makarem

The basic structural (anatomical) , functional and The basic structural (anatomical) , functional and embryological unit of the nervous system is the nerve cell or embryological unit of the nervous system is the nerve cell or neuroneneurone..

The human nervous system is estimated to contain about The human nervous system is estimated to contain about 10101010. .

Neurons

Prof. Saeed Makarem

• The functions of the neuron are The functions of the neuron are to receive and integrate to receive and integrate incoming informationincoming information from sensory receptors or other from sensory receptors or other neurons and to transmit information to other neurons or neurons and to transmit information to other neurons or effector organs. effector organs.

• Neuronal structure is Neuronal structure is highly specializedhighly specialized to fulfill these to fulfill these functions. functions.

Prof. Saeed Makarem

Information is passed Information is passed between neurons at between neurons at specialized regions specialized regions called called synapsessynapses

In the synapsesIn the synapses the the membranes of membranes of adjacent cells are in adjacent cells are in close apposition close apposition (contiguity not (contiguity not continuity).continuity).

Prof. Saeed Makarem

• There is wide diversity There is wide diversity in the shape and size of in the shape and size of neurons in different neurons in different parts of the nervous parts of the nervous system.system.

• But all share certain But all share certain common characteristics. common characteristics.

• There is a single There is a single cell cell bodybody from which a from which a variable number of variable number of branching processes branching processes emerge. emerge.

Prof. Saeed Makarem

Most of these Most of these processes are processes are receptive in function.receptive in function.

They are known as They are known as dendritesdendrites..

Prof. Saeed Makarem

The dendrites possess The dendrites possess synaptic specializations,synaptic specializations, sometimes many thousands sometimes many thousands of them, through which of them, through which they receive information they receive information from other neurons with from other neurons with which they make contactwhich they make contact. .

In sensory neurons, the In sensory neurons, the dendritesdendrites may be specialized to may be specialized to detect changes in the external or internal environment.detect changes in the external or internal environment.

Olfactory receptor neurons

Prof. Saeed Makarem

Prof. Saeed Makarem

• One of the processes leaving One of the processes leaving the cell body is called the the cell body is called the axonaxon which carries which carries information away from information away from the cell the cell body. body.

• Axons are highly variable in Axons are highly variable in length and may divide into length and may divide into several branches or several branches or collateralscollaterals through which through which information can be distributed information can be distributed to a number of different to a number of different destinations simultaneously. destinations simultaneously.

• At the end of the axon, At the end of the axon, specializations called specializations called terminal buttonsterminal buttons occur. occur.

• Here information is Here information is transferred to the dendrites of transferred to the dendrites of other neurones. other neurones.

Prof. Saeed Makarem

• Transmission of information Transmission of information between neurons almost between neurons almost always occurs byalways occurs by chemicalchemical rather than electrical means. rather than electrical means.

• Action potential causes release Action potential causes release of specific chemical that are of specific chemical that are stored in stored in synaptic vesiclessynaptic vesicles in in the presynaptic ending. the presynaptic ending.

• These chemicals are known as These chemicals are known as neurotransmittersneurotransmitters and and diffuse across the narrow gap diffuse across the narrow gap between pre- and postsynaptic between pre- and postsynaptic membranes to bind to membranes to bind to receptorsreceptors on the postsynaptic on the postsynaptic cell, inducing changes in the cell, inducing changes in the membrane potential. membrane potential.

• Neuroglia, or glia cells constitute the other major cellular component of the nervous system.

• It is a specialized connective tissue for the nervous system.• Unlike neurones, neuroglia do not have a direct role in

information processing but they are essential for the normal functioning of nerve cells.

• Neuroglia, or glia cells constitute the other major cellular component of the nervous system.

• It is a specialized connective tissue for the nervous system.• Unlike neurones, neuroglia do not have a direct role in

information processing but they are essential for the normal functioning of nerve cells.

Prof. Saeed Makarem

Neuroglia

Prof. Saeed Makarem

Three main types of neuroglial cell are recognized:

1. Oligodendrocytes (oligodendroglia) they form the myelin sheath that surrounds many neuronal axons, which increase the rate of conduction.

Prof. Saeed Makarem

2. Microglia have a phagocytic role in response to nervous system damage.

Prof. Saeed Makarem

3. Astrocytes are thought to form a selectively permeable barrier between the circulatory system and the neurons of the brain and spinal cord.

• This is known as the 'blood-brain 'blood-brain barrierbarrier'' and has a protective function.

Central and Central and peripheral peripheral

nervous systems nervous systems

Prof. Saeed Makarem

The nervous system is The nervous system is divided into: divided into:

• 1- C1- Central nervous entral nervous systemsystem ( (CNSCNS))..

• 2- P2- Peripheral nervous eripheral nervous systemsystem ( (PNSPNS). ).

Prof. Saeed Makarem

• The The central nervous central nervous systemsystem consists of consists of the the brain and the spinal brain and the spinal cord,cord, lying within the lying within the protection of the cranium protection of the cranium and vertebral column, and vertebral column, respectively. respectively.

• This is the most complex This is the most complex part of the nervous system. part of the nervous system.

• It contains the majority of It contains the majority of nerve cell bodies and nerve cell bodies and synaptic connections. synaptic connections.

Prof. Saeed Makarem

• The The peripheral nervous peripheral nervous systemsystem constitutes the constitutes the link between the CNS and link between the CNS and structures in the structures in the periphery of the body. periphery of the body.

• It receives sensory It receives sensory information from the information from the body.body.

• It sends controlling It sends controlling impulses in response to impulses in response to these information. these information.

• The peripheral nervous The peripheral nervous system consists:system consists:

• 1- Cranial nerves1- Cranial nerves• 2- Spinal nerves.2- Spinal nerves.

Prof. Saeed Makarem

• Spinal nerves serving Spinal nerves serving the upper or lower the upper or lower limbs form the limbs form the brachialbrachial or or lumbar plexuslumbar plexus..

• Nerve cell bodies that Nerve cell bodies that are aggregated within are aggregated within these structures called these structures called gangliaganglia..

Autonomic Autonomic Nervous SystemNervous System

Prof. Saeed Makarem

• Neurones that Neurones that detect changes in, detect changes in, and control the and control the activity of, the activity of, the viscera are viscera are collectively referred collectively referred to as the to as the autonomic autonomic nervous system. nervous system.

• Its components are Its components are present in both the present in both the central and central and peripheral nervous peripheral nervous systemssystems. .

Prof. Saeed Makarem

• The autonomic nervous The autonomic nervous system is divided into two system is divided into two anatomically and functionally anatomically and functionally distinct partsdistinct parts::

• SympatheticSympathetic and and parasympatheticparasympathetic divisions. divisions.

• They generally have They generally have antagonistic effects on the antagonistic effects on the structures that they innervate. structures that they innervate.

• The autonomic nervous The autonomic nervous system innervates:system innervates:

• Smooth muscle, Smooth muscle, • Cardiac muscle,Cardiac muscle,• Secretory glands. Secretory glands. • It is an important part of the It is an important part of the

homeostatic mechanisms that homeostatic mechanisms that control the internal control the internal environment of the bodyenvironment of the body. .

Afferent, Efferent and Afferent, Efferent and Interneuron Interneuron

• Nerve cells that carry information from Nerve cells that carry information from peripheral receptors to the peripheral receptors to the CNSCNS are referred are referred to as to as afferentafferent neurones neurones . .

• If the information they carry reaches a If the information they carry reaches a conscious level they are also called conscious level they are also called sensory sensory neuronsneurons..

• Efferent neuronesneurones carry impulses away carry impulses away from the from the CNSCNS

• If they innervate skeletal muscle to cause If they innervate skeletal muscle to cause movement they are also referred to as movement they are also referred to as motormotor neuronsneurons..

• The vast majority of neurones, however, lies The vast majority of neurones, however, lies entirely within the CNS and are usually entirely within the CNS and are usually called called interneuroninterneuron

REGIONS OF THE BRAINREGIONS OF THE BRAIN

• Cerebral Cerebral hemisphereshemispheres

• DiencephaloDiencephalonn

• CerebellumCerebellum• Brain stemBrain stem

CEREBRAL HEMISPHERESCEREBRAL HEMISPHERES

• The largest part The largest part of the brainof the brain

• They have They have elevations, called elevations, called gyrigyri

• Gyri are Gyri are separated by separated by depressions depressions called called sulcisulci

• Each hemisphere Each hemisphere is divided into 4 is divided into 4 lobeslobes

• Lobes are Lobes are separated by separated by deeper grooves deeper grooves called called fissures or fissures or sulci. sulci.

FRONTAL

PARIETAL

TEMPORAL

OCCIPITAL

MAIN SENSORY AREAS OF THE MAIN SENSORY AREAS OF THE CORTEXCORTEX

• SSomatic sensory omatic sensory areaarea is located in the is located in the parietal lobeparietal lobe posterior to the posterior to the central sulcuscentral sulcus

• VisualVisual area in the area in the medial surface of the medial surface of the posterior lobe posterior lobe

• Auditory Auditory sensationssensations are are received in the received in the temporal lobe close temporal lobe close to the lateral sulcusto the lateral sulcus

• Olfactory Olfactory sensationssensations are are received deep inside received deep inside the temporal lobethe temporal lobeolfactory

PRIMARY MOTOR AREA OF THE PRIMARY MOTOR AREA OF THE CORTEXCORTEX

• PPrimary rimary motor areamotor area is is located in the located in the frontal lobefrontal lobe, , anterior to the anterior to the central sulcuscentral sulcus

• Body is Body is represented represented upside downupside down

• Axons of these Axons of these neurons form neurons form the the pyramidalpyramidal tract tract (corticospinal (corticospinal tracttract))

TISSUE OF THE CEREBRAL TISSUE OF THE CEREBRAL HEMISPHERESHEMISPHERES

• The outermost layer is The outermost layer is the the gray mattergray matter or or cortexcortex

• Deeper is located the Deeper is located the white matterwhite matter, , composed of bundles composed of bundles of nerve fibers, of nerve fibers, carrying impulses to carrying impulses to and from the cortexand from the cortex

• Corpus callosumCorpus callosum is a is a very large fiber tract very large fiber tract connecting the 2 connecting the 2 cerebral hemispherescerebral hemispheres

• BBasal nucleiasal nuclei are made are made from gray matter and from gray matter and are located deep are located deep within the white within the white mattermatter

• They help the motor They help the motor cortex in the cortex in the regulation of voluntary regulation of voluntary motor activitiesmotor activities

Basal nuclei

DIENCEPHALONDIENCEPHALONThe diencephalon is located between the 2 hemispheres and is linked to them and to the brainstem.

The diencephalon is located between the 2 hemispheres and is linked to them and to the brainstem.

The major structures of the diencephalon are the thalamus, hypothalamus and Epithalamus.

The major structures of the diencephalon are the thalamus, hypothalamus and Epithalamus.

THALAMUSTHALAMUSThe thalamus is a relay station for sensory impulses passing upward to the sensory cortex.

The thalamus is a relay station for sensory impulses passing upward to the sensory cortex.

EPITHALAMUSEPITHALAMUSThe epithalamus forms the roof of the 3rd ventricle. It is made from two parts: the pineal body and the choroid plexus.

The epithalamus forms the roof of the 3rd ventricle. It is made from two parts: the pineal body and the choroid plexus.

The choroid plexus produces cerebrospinal fluid.

The choroid plexus produces cerebrospinal fluid.

The pineal body is part of the endocrine system.

The pineal body is part of the endocrine system.

HYPOTHALAMUSHYPOTHALAMUS

The hypothalamus is an important center for regulation of the autonomic nervous system. It regulates body temperature, water balance and metabolism.

The hypothalamus is an important center for regulation of the autonomic nervous system. It regulates body temperature, water balance and metabolism.

It is connected to the pituitary gland, important for the regulation of the endocrine system, and the mammillary bodies, reflex centers involved in olfaction.

It is connected to the pituitary gland, important for the regulation of the endocrine system, and the mammillary bodies, reflex centers involved in olfaction.

THE LIMBIC SYSTEMTHE LIMBIC SYSTEM

• The hypothalamus is an important part The hypothalamus is an important part of the limbic system.of the limbic system.

• The hypothalamus has centers that The hypothalamus has centers that regulate :regulate :

• Appetite, Appetite, • Thirst, Thirst, • Sex, Sex, • Pain, Pain, • PleasurePleasure

BRAIN STEMBRAIN STEM

The brainstem has three parts: midbrain, Pons and medulla oblongata.

The brainstem has three parts: midbrain, Pons and medulla oblongata.

MIDBRAINMIDBRAIN

The midbrain extends from the mammillary bodies to the Pons. It has 3 parts: cerebral aqueduct, cerebral peduncles and corpora quadrigemina.

The midbrain extends from the mammillary bodies to the Pons. It has 3 parts: cerebral aqueduct, cerebral peduncles and corpora quadrigemina.

MIDBRAINMIDBRAIN

Corpora quadrigemina are reflex centers involved with vision and hearing.

Corpora quadrigemina are reflex centers involved with vision and hearing.

The cerebral aqueduct is a canal connecting the 3rd and the 4th ventricle.

The cerebral aqueduct is a canal connecting the 3rd and the 4th ventricle.

MIDBRAINMIDBRAIN

The cerebral peduncles are two big fiber tracts which carry ascending and descending fibers.

The cerebral peduncles are two big fiber tracts which carry ascending and descending fibers.

PONSPONS

The Pons is a rounded part of the brainstem that contains mainly fiber tracts. The reflex center regulating breathing is also located there.

The Pons is a rounded part of the brainstem that contains mainly fiber tracts. The reflex center regulating breathing is also located there.

MEDULLA OBLONGATAMEDULLA OBLONGATA

Medulla oblongata connects the brain with the spinal cord. It contains many fiber tracts and the centers that regulate heart rate, blood pressure, breathing, swallowing and vomiting.

Medulla oblongata connects the brain with the spinal cord. It contains many fiber tracts and the centers that regulate heart rate, blood pressure, breathing, swallowing and vomiting.

CEREBELLUMCEREBELLUM

Cerebellum has 2 hemispheres and a convoluted surface. It has an outer cortex of gray matter and an inner region of white matter. It provides precise coordination for body movements and helps maintain equilibrium.

Cerebellum has 2 hemispheres and a convoluted surface. It has an outer cortex of gray matter and an inner region of white matter. It provides precise coordination for body movements and helps maintain equilibrium.

PROTECTION OF THE CNSPROTECTION OF THE CNS

THE CNS IS PROTECTED BYTHE CNS IS PROTECTED BY::• Skull & vertebral column (bone)Skull & vertebral column (bone)• MeningesMeninges (membranes) (membranes)• Cerebrospinal fluidCerebrospinal fluid (watery (watery

cushion)cushion)

THERE ARE 3 LAYERS OF THERE ARE 3 LAYERS OF MENINGES:MENINGES:

• Dura materDura mater (outer) (outer)• Arachnoid materArachnoid mater (middle) (middle)• Pia materPia mater (inner) (inner)

MENINGESMENINGES

DURA MATERDURA MATER• Double-layered membraneDouble-layered membrane• Outermost layer is attached to the inside surface of the skull Outermost layer is attached to the inside surface of the skull

bones (bones (endostial layerendostial layer))• Internal layer (Internal layer (meningeal layermeningeal layer) covers the surface of the ) covers the surface of the

brain and the spinal cordbrain and the spinal cord• The two layers are fused together, except in 3 places where The two layers are fused together, except in 3 places where

they form channels (they form channels (dural sinusesdural sinuses) where venous blood ) where venous blood from the brain is collectedfrom the brain is collected

• in some places the inner dural membrane forms folds (in some places the inner dural membrane forms folds (falx falx cerebricerebri) that attaches the brain to the cranial cavity) that attaches the brain to the cranial cavity

ARACHNOID MATERARACHNOID MATER• looks like cobweblooks like cobweb• has threadlike extensions (has threadlike extensions (arachnoid villiarachnoid villi) that ) that

attach it to the innermost membrane (pia mater)attach it to the innermost membrane (pia mater)• the arachnoid villi absorb cerebrospinal fluidthe arachnoid villi absorb cerebrospinal fluid• contains the contains the subarachnoid spacesubarachnoid space filled with filled with

cerebrospinal fluidcerebrospinal fluid

PIA MATERPIA MATER• thin, delicate membranethin, delicate membrane• attached to the surface of the brainattached to the surface of the brain

BRAIN VENTRICLESBRAIN VENTRICLES • Brain is bathed by the Brain is bathed by the cerebrospinal fluid cerebrospinal fluid (CSF)(CSF)

• Inside the brain, there Inside the brain, there are spaces are spaces (ventricles)(ventricles) filled with CSFfilled with CSF

• There are 4 ventriclesThere are 4 ventricles 2 2 lateral ventricleslateral ventricles

are in the are in the hemispheres hemispheres

33rdrd ventricle ventricle in the in the diencephalon diencephalon

44thth ventricle ventricle between the Pons and between the Pons and the cerebellumthe cerebellum

CCerebral aqueducterebral aqueduct connects the 3connects the 3rdrd to to the 4the 4thth ventricle ventricle

CEREBROSPINAL FLUIDCEREBROSPINAL FLUIDCSF is constantly produced by the choroid plexuses inside each ventricle.

CSF is constantly produced by the choroid plexuses inside each ventricle.

Inside the brain, CSF flows from the lateral ventricles in the 3rd and 4th ventricle.

Inside the brain, CSF flows from the lateral ventricles in the 3rd and 4th ventricle.

From the 4th ventricle, part of the CSF flows down in the central canal of the spinal cord.

Most of the CSF drains from the 4th ventricle in the subarachnoid space around the brain and returns to the dural sinuses through the arachnoid villi.

THANK THANK YOUYOU