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body .control systems in the body:

1- nervous system :- It controls and coordinates rapid activitiesof the body- how does the nervous system control itsfunctions ? Through neurotransmitters ,which work in these circumstances:

- short distance- short duration : its effect wont last for a

long time.

- its divided into two systems :1-Central nervous system2-peripheral nervous system

- The nervous system transmitselectrical signals.

2- Endocrine system :

- it Controls the metabolic activities in thebody .

- how does it control its function ?Through hormones which act in these

circumstances :

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-long distant- long duration : it effect lasts for a

long time

The endocrine system secrets hormones(chemical messengers) into the circulatingblood to distance sites of the body .

* Neurotransmitters are the chemicalssecreted by the neurons which allow thetransmission of signals from one neuron tothe next across synapses .

* nervous system regulates some hormonessecretion and at the same time hormonesaffect the function of the nervous system .

* presence of certain hormones is importantfor the developing of the nervous tissues .

ORGANAIZATION OF NERVOUSSYSTEM

Nervous system

1- CENTRAL NERVOUS SYSTEM :Consist of neurons : the neurons consist of :

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-cell body-axon-dendrite

Neurons lie entirely within the craniumskull or the vertebral column .( BRAIN & SPINAL CORD )

2- PERIPHERAL NERVOUS SYSTEM :

Divisions of the peripherral nervous system

- Afferent nerve fibers- Efferent nerve fibersAFEERENT nerve fibers are SENSORY anaalways remember that A in Afeerentmeans toward the brain that mean: itsresponsible of carrying the information fromthe body towards the brain ( integrating

cells) .Afferent consists of cell body and axon and its located outside the CNS in the othertissues of the body

EFFERENT nerve fibers are MOTOR andalways remember that the E in Efferent means away from the brain that mean : itscarrying away the response from the brain(integrating cells) to the cells of the bodyThe cell bodies of the efferent neurons arelocated within (inside) the CNS and their

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axons which are called the efferent axons(fibers) lie outside in the PNS (in the body)

We have 12 CRANIAL nerves (pairs)

And 31 SPINAL nerves (pairs)

EFEERENT DEVESIONS :

1- somatic nervous system : which givesme the motor neurons2-autonomic nervous system : which gives

me :- sympathetic nervous system- parasympathetic nervous

system- enteric nervous system : a

collection of nervecells that can act independently from the

CNS

SO to summarize :

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C ont ro l sys tem o f t he body

Endoc r i ne s ys temN e r v o u s s y s t e m

Pe r iphera l ne rvous sys temP NS

Ce nt ra l ne rvou s sys tem

C N Sn e u r o n s

Br ian Sp ina l co rd

Ef feren t d iv is ion

(ce ll bo dy)Ins ide CN S

Af ferent d iv is ion

(ce l lb o d y & a x o n)o u t s id e C N S

A u t o n o m ic n e r v o u ssys tem

S o m a t ic n e r vsys tem

M o t o r n e u r o nIn f ren icN SParasympathe t i c

N SS y m p a t he t ic N S


















Ce nt ra l ne rvou s sys tem

C N Sn e u r o n s








Br ian

Ce n t ra l ne rvou s sys tem

C N Sn e u r o n s








Sp ina l co rdB r ian

Ce n t ra l ne rvou s sys tem

C N Sn e u r o n s








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How do the CNS & the PNS worktogether to control the body :

Central

nervous(spinal c

Neurons are differentiated by their :functionlocationstructure

Notice that the cell body of theafferent is located outside the centalnervous system ( spinal cord) while theefferent is inside the spinal cord

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According to the previous picture we can seethe following

The afferent nerve cells receive stimuli(sensory or visceral) from the body tissues ,and then this stimuli is going to betransferred through the afferent fibers tothe CNS as an input(FROM PERIPHERAL TO CENTRAL )

Then in the central nervous system thebrain and the spinal cord decide the suitableresponse to this stimuli and it sends aresponse to the efferent nerve cells as anoutput(FROM CENTRAL TO PERIPHERAL)

Now in the efferent nerve cells the responsewill be sent to:1- either the somatic nervous system whichconsists of motor neurons that will transferthe response to the SKELETAL CELLS

2- or it will send it to the autonomic nervoussystem which will transfer the response tothe sympathetic and parasympatheticnervous systems which will transfer theresponse to the SMOOTH and CARDIAC

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MUSCLES and GLANDS .

Protection of CNS

The nervous tissue inside the CNS is verydelicate structure ,,, and if the neurons getdamaged it can NOT be replaced so the CNSmust be well protected

The CNS structure is protected by :1- the bony structure : the skull and thevertebral column.

2- meninges :-Dura mater-Arachnoids mater

-Pia mater : its attached inf. To the brain andthe spinal cord ( actually it tightly enclosesthem)

* meningitis : inflamation of the meninges

3- cerebro-spinal fluid (CSF) : which acts as ashock absorber4- blood brain barrier : limits the movementof certain substances from the blood into the

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brain tissue

THE BRAIN METABOLISM :

- O2 and glucose are important to producethe ATP in the brain (aerobic metabolism) ,and they must be continuously supplied tothe brain because :

- there is no anaerobic metabolism ofglucose in the brain

- brain does not store glucoseCutting of O2 supply from the brain for morethan 4 mins lead to brain damage

-hypoglycemia decreases brain activities ,,,and if it continues for a long time it will leadto brain damage

Glial Cells ( Neuroglia)They are considered as the connectivetissue of the nervous system supportingnervous system physically , metabolicallyand homeostatically.

We have to differentiate between neuralgiaand neurons : neurons initiate and conductimpulse while neuroglia dont

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-90% of the cells within the CNS are glialcells

- Glial cells do not branch extensively- they cannot divide- there are 4 types of glial cells :

1- Astrocytes2-oligodendrocytes3- microglia4-epedendymal cells

ASTEROCYTES:-

- hold the neurons together- Repair brain injuries from neural scartissue - support the neurons metabolically and

homeostatically bycreating and maintaining a properenvironment to enable the neurons toperform its function in a proper way-it takes up excess k+ from brain extracellular fluid

- establish blood brain barrier (BBB) :it acts as a selective barrier ( anatomicrestriction and physiologic selection anatomic restriction = there is an anatomic

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composition tight junction between thecapillary space and the capillary cells in thebrain that prevent the down concentration

transition of nutrients and gasesPhysiologic selection = these tight junctionstransport materials through canals andcarriers selectively

-- act as scaffold(bridge) during braindevelopment ,it guides the nerve cellstoward their distance in other words :they can act as scaffolding for neuron

movement, . They actively participate in theregulation and metabolism ofneurotransmitters used by neurons to sendsignals to other neurons and muscles. Infact, they themselves are thought to beinvolved in the signaling process. In

addition, astrocytes are known to act asscavengers to remove debris from dead ordying neurons.# So in general :-1- Astrocytes are involved in setting upscaffolding/template for neurons to migrateon.

2- They're expressed early in development.3- Oligodendrocytes are one of the last cellsto form and express a neuroinhibitoryprotein.

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#And it plays a role in the formation ofneural scarp tissue

Important Questions :-What cells make up glial limiting membrane?What cells establish blood brain barrier byinducing tight junction formation?What cells guide neuroblasts to finaldestination?What cells take up excess K+ during highneuronal activity ?What cells form gliotic scar following CNSinjury?The Answer for all these questions is''Astrocytes''.So According to this we can define and

Summary the Astrocytes function with :-1) Structural support.2) Induce tight jxn formation by endothelialcells.3) take up neurotransmitters within synapticregions.4) Take up excess K+ released during high

neuronal activity.5) Form glial scar after CNS lesion.

Oligodendrocytes :

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they form the myelein sheaths around theaxons in the CNS (corresponding to the

Schwann cells in the PNS)

# Note :- Myelin is made up of %70 Lipidand 30% Protein

# Functions of oligodendrocytes:-1) Ensheath multiple CNS axons with myelin.2) Locally regulate axon size.3) Stabilize axon numbers in a developingpathway. Microglia :

-important in immune system ; they arephagocytic cells in the CNS ,they

phagocytose the foreign bodies , andsometimes secrete some chemicals todestroy these foreign bodies but sometimesthese chemicals could lead to damaging theneurons

# Functions of microglia :-1- Brain macrophages.2- Regulate astrocytes during developmentand injury.

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Ependymal cellsepithelial cells that line the internal cavities

of the CNS like :

cerebrospinal fluid(CSF) ventricles in thebrain and the spinal cord

# FINALLY the doctor advised us to go to(Sherwood) and read the material fromthere.

Hope that we all gonna pass this year ,,,work hard study well and pray for each other

DONE BY : RMZ RABADI

Corrected by : Tamer al-qudahMuath al-z3be

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#1 CNS .... Script