introduction to physiology of the nervous system (cls ,allied medical student)

8/3/2019 Introduction to Physiology of the Nervous System (Cls ,Allied Medical Student)

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Introduction toPhysiology of theNervous System

Dr Fawzia Alrouq

Physiology Department , College of Medicine , KingSaud University , Riyadh

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The Nervous System

A network of billions of nerve cells linkedtogether in a highly organized fashion to form

the rapid control center of the body.Functions include: Integrating center for homeostasis, movement,

and almost all other body functions.


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B asic Functions of the Nervous System

1. SensationMonitors changes/events occurring in and outside the body.Such changes are known as stimuli and the cells that monitorthem are receptors .

2. IntegrationThe parallel processing and interpretation of sensoryinformation to determine the appropriate response

3. ReactionMotor output. The activation of muscles or glands (typically via the release of

neurotransmitters (NTs))


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Nervous vs. Endocrine System

Similarities: They both monitor stimuli and react so as to

maintain homeostasis.

Differences: The Nervous System is a rapid, fast-acting system

whose effects do not always persevere. The Endocrine System acts slower (via blood-

borne chemical signals called Hormons and itsactions are usually much longer lasting.


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O rganization of the NervousSystem

2 big initial divisions:1. Central Nervous System

The brain + the spinal cord The center of integration and control

2. Peripheral Nervous SystemThe nervous system outside of the brainand spinal cord


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Nervous system organization

fig 6-37


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Classification of the Nervous SystemThe nervous system ( NS) can be classified in more than one way :

(I) Central & Peripheral NS(A) Central Nervous System (CNS) : consisting of the brain and spinal

cord , and(B) Peripheral Nervous System (PNS ) : Fibers outside the CNS

(II) Sensory & Motor NS(A) Sensory : includes (i) sensory ( afferent ) fibers , ascending

( sensory ) pathways , & brain sensory centers(B) Motor : includes brain motor centers , descending (motor )

pathways & motor ( efferent ) fibers .

(III) Somatic & Autonomic NS(A) Somatic ( Voluntary) Nervous System(B) Autonomic ( Inovluntary) Nervous System

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Nervous Tissue

Highly cellular2 cell types

1. NeuronsFunctional, signalconducting cells

2. NeurogliaSupporting cells

1.

2.


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NeuronsThe functional and structural unit of thenervous systemSpecialized to conduct information from one part of the body toanother

There are many, many different types of neurons but most havecertain structural and functional characteristics in common:

- Cell body (soma)- O ne or more

specialized, slenderprocesses(axons/dendrites)

- An input region(dendrites/soma)

- A conductingcomponent (axon)

- A secretory (output)

region (axon terminal)


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O verview of theB rain

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Components of The Brain

A/ Telencephalon(1) Cerebrum and(2) Basal Ganglia ( collection of

grey matter situated insidethe cerebral hemispheres )

B/ DiencephalonMainly :

(1) Thalamus ( mainly a relaystation for sensorypathways in their way tothe cerebral cortex )

(2) Hypothalamus ( containscesnter for autonomic andendocrine control )

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C/ Brainstem(1) Midbrain(2) Pons(3) Medulla

E/ Cerebellum


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The Brainstem

The term brainstem isactually an anatomic ratherthan physiologic term ,because it is easier , in termsof anatomy , to group allCNS structures that hang

between the cerebrum andspinal cord together .However , in terms ofPhysiology , the situation ismore complicated , becausebrainstem structures areinvolved in many diverse &different bodily functions .

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These functions include(1) regulation of Consciousness ,Wakefulness & Sleep ,(2) Respiratory , Cardiovascular

and Gastrintestinal control ,(3) Balance ( Vestibular nuclei ) .(4) Moreover , it contain several

Cranial Nerve nuclei .,


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Cerebrum

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The Cerebrum : Composed of 2 C erebral Hemispheres , each of whichcontrols functions on the opposite half of the body

Each hemisphere isdivided by big Sulci( fissures ) into 4lobe s :Parietal lobe

O ccipital lobeTemporal lobeFrontal lobe


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O cciptal Lobe

Contains primary visual Cotrex +Visual Association CortexDisease : blindness

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P arietal Lobe

Contains(1) Primary Somatosensory in the post-central gyrusto receive general sensations from opposite( contralateral ) half of the body(2) Sensory A ssociation Cortex( for integration & association of sensoryinformation ) Parietal lobe is essential for our feeling of touch,warmth / heat , cold, pain , body position andappreciation of shapes of palpated objects .When damaged , the person loses the ability torecognize shapes of complex objects by palpation(palpation = examaination of objects by touch ) .& develops Sensory Inattention on opposite side

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Temporal Lobe(1) contain centers for hearing and taste ,(2) contribute to smell perception .(3) essential for memory function .

(4) lesion may lead to memory impairment &can be associated with temporal lobe epilepsy

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F rontal Lobe

Responsible for initiation and execution ofvoluntary movement .Also contains Brocas area of speech in thedominnat hemisphere ( i.e., in the lefthemisphere in most people ) .Lesion can cause

(1) paralysis on opposite side of the body ,

(2) aphasia ( loss of ability to speak ) if lesioninvolves Brocas area in the dominanthemisphere ) .

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Cerebellum

Important for ccordination ofbody movements and balance .Diseases can result ininccordination of movement andataxia .

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F rontal contains voluntarymotor functions and areas forplanning, mood, smell and

social judgementP arietal contains areas for sensory reception &integration of sensory informationO ccipital is visual center of brainTemporal contains areas for hearing, smell,learning, memory, emotional behaviorCan make a drawing on your hand

Functions of Cerebrum Lobes


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Meninges

Dura mater -- outermost, tough membrane Closest to bone

Arachnoid mater is spider web filamentous layerPia mater is a thin vascular layer adherent to contours of brain


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Cerebrospinal FluidClear liquid fills ventricles and canals & bathesits external surface (in subarachnoid space)B rain produces & absorbs about 500 ml/day

- produced by ependymal cells lining the ventricles filtration of blood through choroid plexus

Functions buoyancy -- floats brain so it neutrally buoyant protection -- cushions from hitting inside of skull chemica l stability -- rinses away wastes. B uoyancy (voevcee)


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The spinal cord is generallycylindrical in shape

From it emerge 31 pairs ofspinal nerves:8 cervical,12 thoracic,5 lumbar,5 sacral and

1 coccygeal.

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Spinal Cordand Spinal Ner ves


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The spinal cord , beside carrying sensory

( ascending ) and motor ( descending ) tracts ,A lso contains the centers of Spinal Reflexes


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Nervous system organization

fig 6-37


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S pinal Tracts


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P eripheral nervous system: efferent division (motorsystem)

fig 6-43

Somatic: single neuron, innervates skeletal muscle,voluntary control

Autonomic: 2 neuron chain, innervates smooth, cardiacmuscle, glands, largely involuntary control


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S ensory S ystem


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Components of Sensory System

ReceptorsPeripheral nerves

Spinal cordTractsThalamus

Thalamocortical projectionSomatosensory cortex


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How inf o rmati o n ab o ut internal & externalHow inf o rmati o n ab o ut internal & external

envir o nment reaches the CNS?envir o nment reaches the CNS?

Via sens o rs i.e.,Via sens o rs i.e.,

Recept o rsRecept o rs that arethat arec o nnected t o the CNS byc o nnected t o the CNS by

different cables [i.e.,different cables [i.e.,ascending tracts].ascending tracts].


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Classificati o n o f recept o rsClassificati o n o f recept o rs

Cutaneous

receptorsM echanoreceptors:Thermoreceptorsnociceptors

M usculoskeletalreceptorsproprioce

ptors

Visceralreceptors

e . g. ,chemoreceptors,baroceptors,mechanoreceptors


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Sensory Pathways Sensorypathways


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DO RSAL CO LUMNPATHWAY

CARRIES FINETO UCH,PO SITIO N,

PRESSURE,VIB RATIO N,TWO PO INT

DESRIMINATIO Nstereognosis

ANTERO LATERALPATHWAY

CARRIES PAIN &TEMPRATURE(lateral

Spinothalamictract)CRUDE TO UCH &PRESSURE (VENTeral. Sp. Th)


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THANK YO U

introduction to physiology of the nervous system (cls ,allied medical student)

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