nervous system - wordpress.com · 2021. 5. 18. · homeostasis the nervous system plays an...

NERVOUS SYSTEMKHALEEL ALYAHYA, PHD, MEDwww.khalelalyahya.net

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INTRODUCTION

The nervous system is arguably the most complex system in thebody.

It facilitates internal communication within the body by integratingand controlling the various functions of the body.

The nervous system is responsible for sending, receiving andprocessing nerve impulses, while the sense organs detect thevarious stimuli in the external environment that humans react to.

Sense organs provide the nervous system with information aboutthe environment by means of such senses as sight, hearing, smell,taste and touch.

The activities that keep the body operating, such as respiration,digestion, heart pumping, movement, all the senses, and the uniqueprocesses that make us human such as thinking, dreaming, laughingand memory, are not possible without a properly functioningnervous system.

3 Khaleel Alyahya, PhD, MEd

SPECIAL SENSES

Vision and sight, hearing, smell, taste and touch.

Vision senses are based on receptor cells or groups of receptor cellscalled sense organs.

Receptors respond to stimuli in the environment and send nerveimpulses along sensory neurons.

Everything we see, hear, feel, smell or taste requires billions ofnerve impulses to send messages to the brain.

Brain interprets the nerve impulse and, thus, we perceive theimpulse through one of our senses.

The figures illustrate the framework about structure and function ofnervous system and special senses.


HOMEOSTASIS

The nervous system plays an important role in coordinating andregulating body functions and communicating within andbetween the brain, spinal cord and all other parts of the body.

Another important function is to interpret stimuli from the externalenvironment so the body can respond accordingly.

Working in association with the endocrine system, the nervoussystem acts to maintain homeostasis, the body’s ability to maintaina constant internal state even in changing externalenvironments.

The nervous system consists of a network of specialized cells calledneurons.

Signals move between the brain and body via these neuralnetworks.


FUNCTIONS

Sensory Input - collect

information

Integration

Motor Output – send

feedback


STRUCTURAL CLASSIFICATION

Central Nervous System

Peripheral Nervous System

STRUCTURAL ORGANIZATION

Central Nervous System (CNS)

• Organs

o Brain.

o Spinal cord.

• Functions:

o Integration; command center.

o Interprets incoming sensory information.

o Issues outgoing instructions.

Peripheral Nervous System (PNS)

• Nerves extending from the brain and spinal cord.

o Spinal nerves—carry impulses to and from the spinal cord.

o Cranial nerves—carry impulses to and from the brain.

• Functions:

o Serve as communication lines among sensory organs, the brain and spinalcord, and glands or muscles.


FUNCTIONAL CLASSIFICATION

Sensory (Afferent)

Motor (Efferent)

FUNCTIONAL ORGANIZATION

Sensory (afferent) division

• Nerve fibers that carry information to the central nervous system.

o Somatic sensory (afferent) fibers carry information from the skin, skeletal muscles,and joints.

o Visceral sensory (afferent) fibers carry information from visceral organs.

Motor (efferent) division

• Nerve fibers that carry impulses away from the central nervous system organs toeffector organs (muscles and glands).

• Two subdivisions:

o Somatic nervous system = voluntary.

• Consciously (voluntarily) controls skeletal muscles.

o Autonomic nervous system = involuntary.

• Automatically controls smooth and cardiac muscles and glands.

• Further divided into the sympathetic and parasympathetic nervous systems.

Interneurons (association neurons)

• Cell bodies located in the CNS

• Connect sensory and motor neurons


COMBINING FORMS


PREFIX & SUFFIX


ABBREVIATIONS


CENTRAL NERVOUS SYSTEM

It consists of the brain and spinal cord.

These structures serve as the main processing centers for the rest ofthe nervous system, controlling the operations of the body.

All nerve impulses either originate or terminate in the CNS.

The CNS is responsible for processing sensations and thoughts usinginformation gathered from sensory receptors throughout the body.

The CNS also sends messages to the rest of the body to controlmovement, actions and responses to the environment.

The main form of communication in the CNS occurs through theneurons.


NERVOUS TISSUE

Nervous tissue is organized as:

• Grey matter: which contains the cell bodies & the processes of theneurons, the neuroglia and the blood vessels.

• White matter: which contains the processes of the neurons (no cellbodies), the neuroglia and the blood vessels.


NERVOUS CELLS

Nervous tissue is made up of two principal cell types:

• Neurons.

• Supporting cells (called neuroglia, or glial cells, or glia).

o Resemble neurons.

o Unable to conduct nerve impulses.

o Never lose the ability to divide.

o Support.

o Insulate.

o Protect neurons.


NEURONS

Cells specialized to transmit messages (nerve impulses).

Major regions of all neurons:

• Cell body—nucleus and metabolic center of the cell.

• Processes—fibers that extend from the cell body.

Processes (fibers)

• Dendrites—conduct impulses toward the cell body.

o Neurons may have hundreds of dendrites.

• Axons—conduct impulses away from the cell body.

o Neurons have only one axon arising from the cell body at the axon hillock.

o End in axon terminals, which contain vesicles with neurotransmitters.

o Axon terminals are separated from the next neuron by a gap.

• Synaptic cleft—gap between axon terminals and the next neuron.

• Synapse—functional junction between nerves where a nerve impulse istransmitted.


NEUROGLIA

Astrocytes

• Abundant, star-shaped cells.

• Brace and anchor neurons to blood capillaries.

• Determine permeability and exchanges between blood capillaries and neurons.

Oligodendrocytes

• Produce myelin sheaths around axons of the CNS

Microglia

• Spiderlike phagocytes.

• Monitor health of nearby neurons.

• Dispose of debris.

Ependymal cells

• Line cavities of the brain and spinal cord.

• Cilia assist with circulation of cerebrospinal fluid.

Schwann cells

• Wrap axons in a jelly roll–like fashion (PNS) to form the myelin sheath

Satellite cells.

• Protect and cushion neuron cell bodies.


TERMS

Myelin: white, fatty material covering axons to speeds nerveimpulse transmission.

Nuclei: clusters of cell bodies in the CNS

Ganglia: collections of cell bodies outside the CNS in the PNS

Tracts: bundles of nerve fibers in the CNS

Nerves: bundles of nerve fibers in the PNS

White matter: collections of myelinated fibers (tracts)

Gray matter: mostly unmyelinated fibers and cell bodies


PHYSIOLOGY

Major regions of all neurons:

• Cell body—nucleus and metabolic center of the cell.

• Processes—fibers that extend from the cell body.

Electrical conditions of a resting neuron’s membrane

• The plasma membrane at rest is inactive (polarized).

• Fewer positive ions are inside the neuron’s plasma membrane than outside.

o K+ is the major positive ion inside the cell.

o Na+ is the major positive ion outside the cell.

• As long as the inside of the membrane is more negative (fewer positive ions)than the outside, the cell remains inactive.

Action potential initiation and generation

• A stimulus changes the permeability of the neuron’s membrane to sodium ions.

• Sodium channels now open, and sodium (Na+) diffuses into the neuron.

• The inward rush of sodium ions changes the polarity at that site and is calleddepolarization.


ACTION POTENTIAL

Stimulus starts the rapid change in voltage or action potential. Inpatch-clamp mode, sufficient current must be administered to thecell in order to raise the voltage above the threshold voltage to startmembrane depolarization.

Depolarization is caused by a rapid rise in membrane potentialopening of sodium channels in the cellular membrane, resulting in alarge influx of sodium ions.

Membrane Repolarization results from rapid sodium channelinactivation as well as a large efflux of potassium ions resulting fromactivated potassium channels.

Hyperpolarization is a lowered membrane potential caused by theefflux of potassium ions and closing of the potassium channels.

Resting state is when membrane potential returns to the restingvoltage that occurred before the stimulus occurred.


NERVE IMPULSES

Neurons have two major functional properties:

• Irritability, the ability to respond to a stimulus and convert it into a nerveimpulse.

• Conductivity, the ability to transmit the impulse to other neurons,muscles, or glands.

A nerve impulse is the way nerve cells (neurons) communicate withone another.

Nerve impulses are mostly electrical signals along the dendrites toproduce a nerve impulse or action potential.

The action potential is the result of ions moving in and out of thecell.

Specifically, it involves potassium (K+) and sodium (Na+) ions.

The ions are moved in and out of the cell by potassium channels,sodium channels and the sodium-potassium pump.


NERVE IMPULSES

Resting membrane is polarized.

• In the resting state, the external face of the membrane is slightly positive;its internal face is slightly negative. The chief extracellular ion is sodium(Na+), whereas the chief intracellular ion is potassium (K+).

• The membrane is relatively impermeable to both ions.

Stimulus initiates local depolarization.

• A stimulus changes the permeability of a local "patch" of the membrane,and sodium ions diffuse rapidly into the cell.

• This changes the polarity of the membrane (the inside becomes morepositive; the outside becomes more negative) at that site.

Depolarization and generation of an action potential.

• If the stimulus is strong enough, depolarization causes membrane polarityto be completely reversed, and an action potential is initiated.


NERVE IMPULSES

Propagation of the action potential.

• Depolarization of the first membrane patch causes permeability changesin the adjacent membrane, and the events described in step 2 arerepeated.

• Thus, the action potential propagates rapidly along the entire length ofthe membrane.

Repolarization.

• Potassium ions diffuse out of the cell as the membrane permeabilitychanges again, restoring the negative charge on the inside of themembrane and the positive charge on the outside surface.

• Repolarization occurs in the same direction as depolarization.

Initial ionic conditions restored.

• The ionic conditions of the resting state are restored later by the activityof the sodium-potassium pump. Three sodium ions are ejected for everytwo potassium ions carried back into the cell.


REFLEXES

Reflexes are rapid, predictable, and involuntary responses to stimuli.

Reflexes occur over neural pathways called reflex arcs.

Two types of reflexes:

• Somatic reflexes.

• Autonomic reflexes.

Somatic reflexes:

• Reflexes that stimulate the skeletal muscles.

• Involuntary, although skeletal muscle is normally under voluntary control.

• Example: pulling your hand away from a hot object.

Autonomic reflexes:

• Regulate the activity of smooth muscles, the heart, and glands.

• Example: regulation of smooth muscles, heart and blood pressure, glands,digestive system.


ELEMENTS OF REFLEX

Five elements of a reflex arc:

• Sensory receptor—reacts to a stimulus.

• Sensory neuron—carries message to the integration center.

• Integration center (CNS)—processes information and directs motoroutput.

• Motor neuron—carries message to an effector.

• Effector organ—is the muscle or gland to be stimulated.

Two-neuron reflex arcs:

• Simplest type.

• Example: patellar (knee-jerk) reflex.

Three-neuron reflex arcs:

• Consists of five elements: receptor, sensory neuron, interneuron, motorneuron, and effector.

• Example: flexor (withdrawal) reflex.


Central Nervous

System

BRAIN


CEREBRUM

The largest region.

Cerebral hemispheres are paired (left and right) superior parts of the brain

• Include more than half of the brain mass.• The surface is made of ridges (gyri) and grooves (sulci).• Fissures are deeper grooves.• Lobes are named for the cranial bones that lie over them.

o Frontal, Parietal, Temporal and Occipital lobes.

Three main regions of cerebral hemisphere

• Cortex is superficial gray matter.• White matter.• Basal nuclei are deep pockets of gray matter.

Cerebral cortex

• Primary somatic sensory areao Located in parietal lobe posterior to central sulcus.

o Receives impulses from the body’s sensory receptors.

• Pain, temperature, light touch (except for special senses).

o Left side of the primary somatic sensory area receives impulses from right side(and vice versa).


CEREBRUM

Cerebral areas involved in special senses

• Visual area (occipital lobe)• Auditory area (temporal lobe)• Olfactory area (temporal lobe)• Primary motor area

o Located anterior to the central sulcus in the frontal lobeo Allows us to consciously move skeletal muscleso Motor neurons form pyramidal (corticospinal) tract, which descends to spinal cord.

• Broca’s area (motor speech area)o Speech Productiono Involved in our ability to speako Usually in left hemisphere

• Other specialized areaso Anterior association area (frontal lobe)o Posterior association area (posterior cortex)o Speech area (Wernicke’s area) (for comprehension of written and spoken language)

Cerebral white matter

• Composed of fiber tracts deep to the gray mattero Corpus callosum connects hemisphereso Tracts, such as the corpus callosum, are known as commissureso Association fiber tracts connect areas within a hemisphereo Projection fiber tracts connect the cerebrum with lower CNS centers


BASAL NUCLEI

Basal nuclei

• Islands of gray matter buried deep within the white matter ofthe cerebrum.

• Regulate voluntary motor activities by modifying instructionssent to skeletal muscles by the primary motor cortex.


DIENCEPHALON

Sits on top of the brain stem.

Made of three structures:

• Thalamus• Hypothalamus• Epithalamus

Thalamus

• Encloses the third ventricle• Relay station for sensory impulses passing upward to the cerebral cortex• Transfers impulses to the correct part of the cortex for localization and

interpretation

Hypothalamus

• Makes up the floor of the diencephalon• Important autonomic nervous system center

o Regulates body temperature

o Regulates water balance

o Regulates metabolism

• Houses the limbic center for emotions• Regulates the nearby pituitary gland• Houses mammillary bodies for olfaction (smell)

Epithalamus

• Forms the roof of the third ventricle• Houses the pineal body (an endocrine gland)• Includes the choroid plexus—forms cerebrospinal fluid


BRAINSTEM

Attaches to the spinal cord

Midbrain

• Extends from the mammillary bodies to the pons inferiorly

• Cerebral aqueduct (tiny canal) connects the third and fourth ventricles

• Two bulging fiber tracts, cerebral peduncles, convey ascending anddescending impulses

• Four rounded protrusions, corpora quadrigemina, are visual and auditoryreflex centers

Pons

• The rounded structure protruding just below the midbrain

• Mostly composed of fiber tracts

• Includes nuclei involved in the control of breathing

Medulla Oblongata

• The most inferior part of the brain stem that merges into the spinal cord

• Includes important fiber tracts

• Contains important centers that control:

o Heart rate and Blood pressure

o Breathing, Swallowing and Vomiting

• Fourth ventricle lies posterior to pons and medulla34 Khaleel Alyahya, PhD, MEd

CEREBELLUM

Two hemispheres with convoluted surfaces.

Outer cortex of gray matter and inner region of white matter.

Control balance.

Provides precise timing for skeletal muscle activity and coordinationof body movements.


SPINAL CORD

Extends from the foramen magnum of the skull to the first or second lumbar vertebra

Cauda equina is a collection of spinal nerves at the inferior end

Provides a two-way conduction pathway to and from the brain

31 pairs of spinal nerves arise from the spinal cord

Gray matter of the spinal cord and spinal roots

• Internal gray matter is mostly cell bodies

• Dorsal (posterior) horns house interneurons

o Receive information from sensory neurons in the dorsal root; cell bodies housed in dorsal root ganglion

• Anterior (ventral) horns house motor neurons of the somatic (voluntary) nervous system

o Send information out ventral root

• Gray matter surrounds the central canal, which is filled with cerebrospinal fluid

White matter of the spinal cord

• Composed of myelinated fiber tracts

• Three regions: dorsal, lateral, ventral columns

• Sensory (afferent) tracts conduct impulses toward brain

• Motor (efferent) tracts carry impulses from brain to skeletal muscles36 Khaleel Alyahya, PhD, MEd

MENINGES

Dura mater

• Outermost leathery layer

Arachnoid mater

• Middle layer

• Weblike extensions span the subarachnoid space to attach it tothe pia mater

• Subarachnoid space is filled with cerebrospinal fluid

Pia mater

• Internal layer

• Clings to the surface of the brain and spinal cord


CEREBROSPINAL FLUID

Similar to blood plasma in composition.

Formed continually by the choroid plexuses.

• Choroid plexuses—capillaries in the ventricles of the brain.

CSF forms a watery cushion to protect the brain and spinal cord.

Flows through the ventricles and into the subarachnoid space via themedian and lateral apertures. Some CSF flows through the central canalof the spinal cord.

CSF flows through the subarachnoid space.

CSF is absorbed into the dural venous sinuses via the arachnoid villi.


Peripheral Nervous

System

NERVE STRUCTURE

PNS consists of nerves and ganglia outside the CNS.

Nerves are bundles of neurons found outside the CNS.

Endoneurium is a connective tissue sheath that surrounds each fiber.

Perineurium wraps groups of fibers bound into a fascicle.

Epineurium binds groups of fascicles.

Mixed nerves.

• Contain both sensory and motor fibers.

Sensory (afferent) nerves.

• Carry impulses toward the CNS.

Motor (efferent) nerves.

• Carry impulses away from the CNS.


CRANIAL NERVES

12 pairs of nerves serve mostly the head and neck.

4 pairs are mixed:

• trigeminal (5th).

• Facial (7th).

• glossopharyngeal (9th).

• vagus (10th).

5 pairs are motor:

• occulomotor (3rd).

• trochlear (4th).

• abducent (6th).

• accessory (11th).

• hypoglossal (12th).

3 pairs are sensory:

• olfactory (1st).

• optic (2nd).

• vestibulocochlear (8th).

Only the pair of vagus nerves extends to thoracic and abdominal cavities.41 Khaleel Alyahya, PhD, MEd

CRANIAL NERVES

Oh – Olfactory

Oh – Optic

Oh – Oculomotor

To – Trochlear

Touch – Trigeminal

And – Abducens

Feel – Facial

Very – Vestibulocochlear

Green – Glossopharyngeal

Vegetables – Vagus

A – Accessory

H – Hypoglossal


CRANIAL NERVES


SPINAL NERVES

31 pairs.

Formed by the combination of the ventral and dorsal roots of the spinal cord.

Named for the region of the spinal cord from which they arise.

Spinal nerves divide soon after leaving the spinal cord. into a dorsal ramusand a ventral ramus.

• Ramus—branch of a spinal nerve; contains both motor and sensory fibers.

• Dorsal rami—serve the skin and muscles of the posterior trunk.

• Ventral rami (T1–T12) —form the intercostal nerves that supply muscles and skin of the ribs and trunk.

• Ventral rami (except T1–T12)—form a complex of networks (plexus) for the anterior.

Plexus—networks of nerves serving motor and sensory needs of the limbs.

Form from ventral rami of spinal nerves in the cervical, lumbar, and sacralregions.

Four plexuses:

• Cervical

• Brachial

• Lumbar

• Sacral44 Khaleel Alyahya, PhD, MEd

Autonomic Nervous

System

OVERVIEW

Motor subdivision of the PNS

• Consists only of motor nerves.

• Controls the body automatically (and is also known as the involuntary nervoussystem).

• Regulates cardiac and smooth muscles and glands.

Somatic and Autonomic Nervous Systems Compared

• Somatic nervous system

o Motor neuron cell bodies originate inside the CNS

o Axons extends to skeletal muscles that are served

• Autonomic nervous system

o Chain of two motor neurons

• Preganglionic neuron is in the brain or spinal cord

• Postganglionic neuron extends to the organ

o Has two arms

• Sympathetic and Parasympathetic divisions


FUNCTIONS

Body organs served by the autonomic nervous system receive fibersfrom both divisions.

• Exceptions: blood vessels, structures of the skin, some glands, and the adrenalmedulla.

• These exceptions receive only sympathetic fibers.

When body divisions serve the same organ, they cause antagonisticeffects due to different neurotransmitters.

• Parasympathetic (cholinergic) fibers release acetylcholine.

• Sympathetic postganglionic (adrenergic) fibers release norepinephrine.

• Preganglionic axons of both divisions release acetylcholine.


SYMPATHETIC & PARASYMPATHETIC

Sympathetic—fight or flight division

• Response to unusual stimulus when emotionally or physicallystressed or threatened.

• Takes over to increase activities.

• Remember as the “E” division.

o Exercise

o Excitement

o Emergency

o Embarrassment

Parasympathetic—rest and digest activates.

• “Rest-and-digest” system.

• Conserve's energy.

• Maintains daily necessary body functions.

• Remember as the “D” division.

o Digestion

o Defecation

o Diuresis48 Khaleel Alyahya, PhD, MEd

Pathology & Diseases

Check page 263-267 from the book Mastering Medical Terminology for thecomplete list of pathology and diseases.

ALZHEIMER’S DISEASE

Alzheimer’s disease (dementia) also known as Alzheimer’s dementia, isan irreversible, progressive brain disorder of deteriorating mentalcapacity.

It is characterized by confusion, memory loss, other cognitive defectsand eventually even the inability to carry out the simplest tasks oractivities of daily living.

The Alzheimer’s brain is characterized by the deposit of amyloid plaquesand atrophy.

Alzheimer’s disease is the most common cause of dementia amongolder people.


PARKINSON’S DISEASE

Parkinson’s disease is a slowly progressive, degenerative neurologicdisorder.

Nerve cells in the brain deteriorate causing a deficiency of theneurotransmitter dopamine.

Parkinson’s disease is characterized by:

• Rhythmic fine tremors or trembling in the hands, arms, legs, jaw and face.

• Stiffness of the limbs and joints.

• Bradykinesia.

• Impaired balance and coordination.

It causes weakness and stiffness of the muscles and interferes withspeech, walking and daily tasks.

There is no cure for Parkinson’s disease, therefore treatment is aimedat improving the symptoms.


EPILEPSY

Epilepsy is an episodic neurological disorder characterized by recurrent,transient abnormal electrical activity in the brain.

The normal pattern of neuronal activity becomes disturbed, causing aperiod of confusion, sensory disturbances, a staring spell, convulsions,muscle spasms and/or loss of consciousness.

Epilepsy has many possible causes, including illness, an imbalance ofneurotransmitters, brain injury and abnormal brain development.

In many cases, the cause is unknown.

Epilepsy is classified by the type of seizure; partial or focal andgeneralised.

In partial seizures, there is no loss of consciousness rather the patientmay appear to be daydreaming with only mild symptoms.

Generalised seizures include a loss of consciousness with possiblemusclespasm.

Epilepsy can usually be controlled by anticonvulsant medications.


MENINGITIS

Meningitis is an inflammation in the meninges.

Most cases are due to a bacterial or viral infection.

Meningitis usually has a sudden onset and is characterized by a severeheadache, neck stiffness, irritability, fever, nausea, vomiting anddelirium.

A particular type of meningitis, meningococcal meningitis, ischaracterized by a rapidly spreading rash.

Meningitis can be life threatening because of the proximity to thebrain and spinal cord; therefore, the condition is classified as a medicalemergency.

A lumbar puncture is performed to diagnose the condition.

Treatment is with specific antibiotics.


PARALYSIS

Paralysis is loss of the ability to move one or more muscles.

It may be associated with loss of feeling and other bodily functions.

Paralysis may be partial or complete, and temporary or permanent.

It is not usually caused by problems with the muscles, but by problemswith the spinal cord or nerves that control muscles.

A person with paralysis will usually have some form of nerve damage.

Most paralysis results from cerebrovascular accidents and spinal cordinjuries.

Other causes of paralysis include Bell’s palsy, multiple sclerosis, andGuillain-Barré syndrome.


CEREBRAL PALSY

It refers to a variety of neurological conditions that manifest as disordersof movement or posture.

Body movement and muscle coordination are permanently affected.

While it may appear to be a muscular disorder, cerebral palsy isactually due to damage to the part of the brain that controls musclemovements.


MULTIPLE SCLEROSIS

It is a progressive degenerative neurological disease with scatteredpatches of demyelination of nerve fibres of the brain and spinal cord.

Common symptoms include tingling, numbness, muscle weakness orspasm, ataxia, dysarthria, dysphagia, visual problems (such as diplopia),fatigue, pain and bladder and bowel incontinence.


HYDROCEPHALUS

It is an increased amount of cerebrospinal fluid (CSF) within the ventricles ofthe brain.

It results in an abnormal widening of the ventricles.

This widening creates a potentially harmful increase in pressure on thecerebral tissues.


Tests & Procedures

Check page 268-269 from the book Mastering Medical Terminology for thecomplete list of tests and procedures.

CEREBRAL ANGIOGRAPHY

Cerebral angiography is a procedure which uses radio-opaque contrastto record x-ray images of the blood vessels in the brain to identifyconditions such as aneurysms, occlusion and haemorrhage in the brain.


CEREBRAL FLUID ANALYSIS

Cerebrospinal fluid (CSF) analysis is a test that is undertaken todiagnose a range of diseases and conditions affecting the CNS.

Conditions include infectious diseases such as meningitis andencephalitis, haemorrhaging from the brain and tumours within theCNS.


LUMBAR PUNCTURE

The patient lies on one side, curled forward to open the interspinousspaces of the lumbar region. The spine of vertebra L4 is identified in theintercristal (supracristal) plane at the level of the tops of the iliac crests.

Under aseptic conditions, a lumbar puncture needle is introducedobliquely above the spine of vertebra L4, parallel to the plane of thespine. The needle is passed through the interspinous ligament. A slightgive is perceived when the needle pierces the dura–arachnoid mater andenters the subarachnoid space.

Transverse section showing the cauda equina floating in the subarachnoidspace. The anterior and posterior roots of spinal nerve L3 are comingtogether as they leave the lumbar cistern.


COMPUTED TOMOGRAPHY

A CT is a diagnostic test that can be used to identify disorders of thebrain and spinal cord.


MAGNETIC RESONANCE IMAGING

MRI is a process of diagnostic testing to create images of the brainusing radio waves and a magnetic field to identify lesions that cannotbe easily noted on x-ray


DOPPLER ULTRASOUND STUDY

A Doppler ultrasound study is a test using ultrasound technology toanalyze the speed of blood flow in the carotid and intracranial arteriesby measuring echoes from the blood vessel


QUESTIONS?

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nervous system - wordpress.com · 2021. 5. 18. · homeostasis the nervous system plays an...

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