Review Of Anatomy And Physiology Of The Nervous

Review of Anatomy and Review of Anatomy and Physiology of the Nervous Physiology of the Nervous

SystemSystem

Anthony P. Toledo, MD, RN, MAN, FPAFPAnthony P. Toledo, MD, RN, MAN, FPAFP

Chairman, MS2Chairman, MS2

Our Lady of Fatima UniversityOur Lady of Fatima University

ObjectivesObjectives Review the anatomy and physiology of the Review the anatomy and physiology of the

nervous systemnervous system Identify specific topics for consideration during Identify specific topics for consideration during

health history assessment interview of the health history assessment interview of the client with neurologic disorders.client with neurologic disorders.

Describe assessment of neurologic function, Describe assessment of neurologic function, including examination of mental status, cranial including examination of mental status, cranial nerves, sensory nerves, motor nerves, nerves, sensory nerves, motor nerves, cerebellar dysfunction and reflexes.cerebellar dysfunction and reflexes.

Describe special neurologic examinations.Describe special neurologic examinations. Identify abnormal findings that may indicate Identify abnormal findings that may indicate

impairment of neurologic functions.impairment of neurologic functions.

Nervous SystemNervous System

initiates actions and coordinates the initiates actions and coordinates the activity of the musclesactivity of the muscles

monitors the organsmonitors the organsconstructs and also stops input from the constructs and also stops input from the

sensessenses

Organization of theNervous System

Peripheral

Somatic

Autonomic

Sympathetic

Parasympathetic

Enteric

Central

Parts of the Nervous SystemParts of the Nervous System

The nervous system is The nervous system is divided into the central divided into the central nervous system nervous system (consisting of the brain (consisting of the brain and spinal cord) and the and spinal cord) and the peripheral nervous peripheral nervous system (consists of system (consists of nerves made up of nerves made up of neurons that carry neurons that carry information to and from information to and from the central nervous the central nervous system).system).

Neuron StructureNeuron Structure

Cell body Cell body Large vesicular Large vesicular

nucleus nucleus Single prominent Single prominent

nucleolus nucleolus Mitochondria & other Mitochondria & other

organelles organelles Abundant RER (Nissl Abundant RER (Nissl

substance) substance) Microtubules & Microtubules &

neurofilaments neurofilaments


Dendrites Dendrites Receive information Receive information

and transmit it to the and transmit it to the cell body cell body


Axon Axon Thin, cylindrical Thin, cylindrical

process arising from process arising from the axon hillock the axon hillock

Contain abundant Contain abundant microtubules and microtubules and neurofilaments neurofilaments

Terminate as synaptic Terminate as synaptic boutons which contain boutons which contain vesicles of vesicles of neurotransmitter neurotransmitter


Node of RanvierNode of Ranvier Discontinuity in the Discontinuity in the

myelin myelin Exposed to Exposed to

extracellular space extracellular space Action potential skips Action potential skips

from node to node from node to node "saltatory conduction" "saltatory conduction"


Myelin Myelin Unmyelinated axons Unmyelinated axons

Seen in peripheral nerves Seen in peripheral nerves Surrounded by cytoplasm Surrounded by cytoplasm

of Schwann cells of Schwann cells Small diameter Small diameter Slow conduction velocity Slow conduction velocity

Myelinated axons Myelinated axons Larger diameter Larger diameter Ensheathed in myelin Ensheathed in myelin Rapid conduction velocityRapid conduction velocity


Myelin Forming CellsMyelin Forming Cells Schwann Cells Schwann Cells

Myelin forming cells of the peripheral nervous system Myelin forming cells of the peripheral nervous system Formed during fourth month of development Formed during fourth month of development One Schwann cell myelinates only one axon One Schwann cell myelinates only one axon

Oligodendrocytes Oligodendrocytes Myelin-forming cells of the CNS Myelin-forming cells of the CNS Begin formation during fourth month of development and Begin formation during fourth month of development and

continue until second decade of life continue until second decade of life Individual oligodendrocyte able to myelinate many axons Individual oligodendrocyte able to myelinate many axons Degeneration results in multiple sclerosis Degeneration results in multiple sclerosis

Classification of Neurons by Classification of Neurons by Neuronal ProcessesNeuronal Processes

Unipolar neurons -- one axon, no dendrites; Unipolar neurons -- one axon, no dendrites; occur only during development occur only during development

Bipolar neurons -- found in cochlear and Bipolar neurons -- found in cochlear and vestibular ganglia, retina and olfactory mucosa vestibular ganglia, retina and olfactory mucosa

Multipolar neurons -- one axon and multiple Multipolar neurons -- one axon and multiple dendrites, found in ventral horndendrites, found in ventral horn*Most neurons in body are multipolar *Most neurons in body are multipolar

Pseudounipolar neurons -- found in dorsal root Pseudounipolar neurons -- found in dorsal root ganglia and most cranial ganglia ganglia and most cranial ganglia

Classification of Neurons by Classification of Neurons by Functional RoleFunctional Role

Motor Neurons - Motor Neurons - Control effector organs Control effector organs and muscle fibers and muscle fibers

Sensory Neurons - Sensory Neurons - Receive sensory Receive sensory stimuli from internal or external stimuli from internal or external environment; Relay them to CNS environment; Relay them to CNS

Action PotentialAction Potential

Synapse Synapse

Synapses - Synapses - Specialized membrane Specialized membrane junctions designed for unidirectional junctions designed for unidirectional communication between neurons or communication between neurons or between neurons and effector cells. Pre- between neurons and effector cells. Pre- and postsynaptic membranes separated and postsynaptic membranes separated by 20 nm. space called synaptic cleft.by 20 nm. space called synaptic cleft.

Synaptic Vesicles Synaptic Vesicles Synaptic vesicles - Synaptic vesicles - Contain Contain

neurotransmitter. neurotransmitter. Release NT into synaptic cleft when Release NT into synaptic cleft when

vesicles fuse with presynaptic membrane. vesicles fuse with presynaptic membrane. NT may excite (depolarize) or inhibit NT may excite (depolarize) or inhibit (hyperpolarize) the postsynaptic membrane.(hyperpolarize) the postsynaptic membrane.

Certain NT are inactivated in synaptic cleft Certain NT are inactivated in synaptic cleft by Enzymatic degradation (e.g., ACh by by Enzymatic degradation (e.g., ACh by AChE). Reuptake by presynaptic cell (e.g., AChE). Reuptake by presynaptic cell (e.g., NE) NE)

Synaptic TransmissionSynaptic Transmission

Neuromuscular JunctionNeuromuscular Junction

Occurs at the motor end plateOccurs at the motor end plateSynapse between neurons and muscle Synapse between neurons and muscle

cells cells ACh released from axon depolarizes ACh released from axon depolarizes

sarcolemma via the acetylcholine nicotinic sarcolemma via the acetylcholine nicotinic receptors receptors

Autoimmune response causes myasthenia Autoimmune response causes myasthenia gravisgravis

Neuromuscular JunctionNeuromuscular Junction

NeurogliaNeuroglia

"Nerve glue""Nerve glue" In CNS: microglia, astrocytes, In CNS: microglia, astrocytes,

oligodendrocytes, and ependymal cells oligodendrocytes, and ependymal cells In PNS: Schwann cells In PNS: Schwann cells

Types of NeurogliaTypes of Neuroglia Astrocytes Astrocytes

Important in controlling microenvironment of nerve cells Important in controlling microenvironment of nerve cells Participate in maintenance of the blood-brain barrier Participate in maintenance of the blood-brain barrier

Oligodendrocytes Oligodendrocytes Myelinate axons of the CNS Myelinate axons of the CNS

Microglia Microglia Phagocytic, part of the mononuclear phagocyte system Phagocytic, part of the mononuclear phagocyte system Unlike other neuroglial cells which originate from neuroectoderm Unlike other neuroglial cells which originate from neuroectoderm Originate from mesoderm Originate from mesoderm

Ependymal cells Ependymal cells Line the ventricular cavities of the brain and central canal of spinal Line the ventricular cavities of the brain and central canal of spinal

cord cord Cilia present on cells helps move cerebrospinal fluid through Cilia present on cells helps move cerebrospinal fluid through

ventricles ventricles Schwann cells Schwann cells

Myelinate peripheral axons Myelinate peripheral axons

Derivatives of the Brain VesiclesDerivatives of the Brain Vesicles

Forebrain Forebrain Telencephalon — Telencephalon —

cerebral hemispheres cerebral hemispheres and lateral ventricles and lateral ventricles

Diencephalon — Diencephalon — thalamus, thalamus, hypothalamus, and hypothalamus, and epithalamus including epithalamus including the pineal gland, the pineal gland, mammilary bodies, mammilary bodies, retina, and optic nerve retina, and optic nerve

Derivatives of the Brain VesiclesDerivatives of the Brain Vesicles

Midbrain Midbrain Mesencephalon — Mesencephalon —

midbrain and cerebral midbrain and cerebral aqueduct aqueduct

Hindbrain Hindbrain Metencephalon — Metencephalon —

pons and cerebellum pons and cerebellum Myelencephalon — Myelencephalon —

medullamedulla

The BrainThe Brain

The BrainThe Brain

Cerebral Cortex Cerebral Cortex Surface is highly convoluted with bulges Surface is highly convoluted with bulges

referred to as gyri and spaces referred to as gyri and spaces separating the gyri called sulci separating the gyri called sulci

Two prominent sulci Two prominent sulci Sylvian fissure — divides the fontal and Sylvian fissure — divides the fontal and

temporal lobes temporal lobes Central sulcus of Rolando — separates Central sulcus of Rolando — separates

the parietal and temporal lobes the parietal and temporal lobes

The BrainThe Brain

Frontal LobeFrontal Lobe Primary motor cortex Primary motor cortex

— damage causes — damage causes contralateral spastic contralateral spastic paresis. Located in the paresis. Located in the precentral gyrusprecentral gyrus

Premotor cortex —Premotor cortex —damage causes damage causes apraxias apraxias

The BrainThe Brain

The motor homunculus The motor homunculus in precentral gyrusin precentral gyrus Muscles of head Muscles of head

represented most ventrally represented most ventrally closest to lateral fissure closest to lateral fissure

Dorsally, regions of neck, Dorsally, regions of neck, upper limb, and trunk on upper limb, and trunk on lateral aspect lateral aspect

Medial aspect motor Medial aspect motor representation for the representation for the pelvis and lower limb pelvis and lower limb

Supplied by branches of Supplied by branches of anterior cerebral artery anterior cerebral artery

The BrainThe Brain Prefrontal Cortex Prefrontal Cortex

Located in front of premotor area Located in front of premotor area Represents ¼ of entire cerebral cortex in Represents ¼ of entire cerebral cortex in

human brain human brain Involved in organizing and planning the Involved in organizing and planning the

intellectual and emotional aspects of behaviorintellectual and emotional aspects of behavior Lesions to prefrontal area Lesions to prefrontal area

Cannot concentrate Cannot concentrate Easily distracted Easily distracted General lack of initiative, foresight, and General lack of initiative, foresight, and

perspective perspective Apathy Apathy Suckling and grasp reflexes evidentSuckling and grasp reflexes evident

The BrainThe Brain

Expressive Aphasia Expressive Aphasia Area in left or dominant hemisphere Area in left or dominant hemisphere

affected.affected. Damage to Broca’s area produces Damage to Broca’s area produces

a motor, nonfluent, or expressive a motor, nonfluent, or expressive aphasia that reflects a difficulty in aphasia that reflects a difficulty in piecing together words to produce piecing together words to produce expressive speech expressive speech

The BrainThe Brain

Parietal Lobe Parietal Lobe Primary Somatosensory Cortex Primary Somatosensory Cortex

Begins posterior to central sulcus with Begins posterior to central sulcus with postcentral gyrus postcentral gyrus

Contains primary somatosensory Contains primary somatosensory cortex cortex

The BrainThe Brain

The sensory The sensory homunculus in homunculus in

postcentral gyruspostcentral gyrus Similar somatotopic Similar somatotopic

representation of bodyrepresentation of body Head, neck, upper Head, neck, upper

limbs, and trunk limbs, and trunk laterally laterally

Pelvis and lower limb Pelvis and lower limb mediallymedially

The BrainThe Brain Parietal LobeParietal Lobe

Posterior Parietal Association CortexPosterior Parietal Association Cortex Lesions here if in the dominant hemisphere Lesions here if in the dominant hemisphere

result in apraxia result in apraxia Deficit seems to reflect a lack of Deficit seems to reflect a lack of

understanding how to organize the understanding how to organize the performance of a pattern of movements performance of a pattern of movements

Astereognosia (inability to recognize items by Astereognosia (inability to recognize items by touch) may be present touch) may be present

No loss of tactile or proprioceptive sensation No loss of tactile or proprioceptive sensation

The BrainThe Brain

Receptive Aphasia Receptive Aphasia Cannot comprehend spoken language, Cannot comprehend spoken language,

May or may not be able to read (alexia), May or may not be able to read (alexia), Characterized by fluent verbalization Characterized by fluent verbalization that lacks meaning, Generally unaware that lacks meaning, Generally unaware of deficitof deficit

The BrainThe Brain Occipital LobeOccipital Lobe

known as primary visual cortex known as primary visual cortex Retinal surface represented in orderly manner on Retinal surface represented in orderly manner on

surface of the area surface of the area Damage to discrete area will produce scotoma in Damage to discrete area will produce scotoma in

corresponding portion of visual field corresponding portion of visual field Unilateral lesion in results in a contralateral Unilateral lesion in results in a contralateral

homonymous hemianopsia with macular sparing homonymous hemianopsia with macular sparing

Posterior cerebral artery supplies occipital lobe and Posterior cerebral artery supplies occipital lobe and splenium of corpus callosum splenium of corpus callosum

The BrainThe Brain

Temporal LobeTemporal Lobe Primary Auditory Cortex Primary Auditory Cortex

located on the two transverse gyri of Heschl located on the two transverse gyri of Heschl Cross the superior temporal lobe deep within the Cross the superior temporal lobe deep within the

lateral sulcus lateral sulcus Patients with unilateral damage show little loss of Patients with unilateral damage show little loss of

auditory sensitivity but have some difficulty in auditory sensitivity but have some difficulty in localizing sounds in contralateral field localizing sounds in contralateral field

The BrainThe Brain CerebellumCerebellum

Derived from the Metencephalon Derived from the Metencephalon Located dorsal to the pons and Located dorsal to the pons and

medulla medulla Fourth ventricle found between Fourth ventricle found between

cerebellum and dorsal aspect of cerebellum and dorsal aspect of pons pons

Involved in fine tuning and Involved in fine tuning and coordination of muscle movements coordination of muscle movements

The BrainThe Brain

CerebellumCerebellum Midline vermis and two Midline vermis and two

lateral cerebellar lateral cerebellar hemispheres hemispheres

Vermis controls axial and Vermis controls axial and proximal musculature of proximal musculature of limbs limbs

Intermediate part of Intermediate part of hemisphere controls distal hemisphere controls distal musculaturemusculature

The BrainThe Brain

CerebellumCerebellum Midline vermis and two Midline vermis and two

lateral cerebellar lateral cerebellar hemispheres hemispheres

Lateral part involved in Lateral part involved in motor planning and motor planning and execution execution

Also called the Also called the cerebrocerebellum cerebrocerebellum due to input from due to input from cerebrum cerebrum

Flocculonodular lobe Flocculonodular lobe involved in control of involved in control of balance and eye balance and eye movements movements

Also called the Also called the vestibulocerebellumvestibulocerebellum

Cerebellar LesionsCerebellar Lesions

Hallmark of cerebellar dysfunction is tremor with Hallmark of cerebellar dysfunction is tremor with intended movement without paralysis or paresis intended movement without paralysis or paresis

Symptoms associated are expressed ipsilaterally Symptoms associated are expressed ipsilaterally Vermal region lesion Vermal region lesion

Difficulty maintaining posture, gait, or balance Difficulty maintaining posture, gait, or balance May be differentiated from those patients with lesion May be differentiated from those patients with lesion

of dorsal columns by presence of a Romberg’s sign of dorsal columns by presence of a Romberg’s sign Cerebellar lesion will have patient sway with eyes open Cerebellar lesion will have patient sway with eyes open

Cerebellar LesionsCerebellar Lesions Hemisphere lesions Hemisphere lesions

Intention tremor is seen when voluntary movements Intention tremor is seen when voluntary movements performed performed

Dysmetria — inability to stop a movement at the Dysmetria — inability to stop a movement at the proper place proper place

Dysdiadochokinesia — reduced ability to perform Dysdiadochokinesia — reduced ability to perform alternating movements alternating movements

Scanning dysarthria Scanning dysarthria Gaze dysfunction occurs when eyes try to fix on a Gaze dysfunction occurs when eyes try to fix on a

point point Hypotonia — occurs with acute insult Hypotonia — occurs with acute insult

Muscles feel flabby on palpation Muscles feel flabby on palpation Deep tendon reflexes diminished Deep tendon reflexes diminished

The BrainThe Brain ThalamusThalamus

major sensory relay for ascending tactile, visual, auditory, major sensory relay for ascending tactile, visual, auditory, and gustatory information that goes to neocortexand gustatory information that goes to neocortex

The BrainThe Brain

HypothalamusHypothalamus

The BrainThe Brain

Limbic SystemLimbic System Involved in Feeding, Fighting, Feeling, Flight, and sex (5Fs)Involved in Feeding, Fighting, Feeling, Flight, and sex (5Fs)

Consists of cortical and diencephalic structures found on Consists of cortical and diencephalic structures found on the medial aspect of the hemisphere the medial aspect of the hemisphere

Prominent structure — hippocampal formation on medial Prominent structure — hippocampal formation on medial aspect of the temporal lobe aspect of the temporal lobe

Other limbic related structures Other limbic related structures Amygdala — deep in medial part of anterior temporal Amygdala — deep in medial part of anterior temporal

lobe rostral to hippocampus lobe rostral to hippocampus Septal nuclei — medial between anterior horns of lateral Septal nuclei — medial between anterior horns of lateral

ventricle ventricle

The BrainThe Brain

Basal GangliaBasal Ganglia Initiate and provide gross control over Initiate and provide gross control over

skeletal muscle movements skeletal muscle movements Disorders result in uncontrolled, excessive Disorders result in uncontrolled, excessive

movements or hypokinesiamovements or hypokinesia

The BrainThe Brain

Basal GangliaBasal Ganglia Major components Major components

Striatum—caudate Striatum—caudate nucleus and putamen nucleus and putamen

External and internal External and internal segments of globus segments of globus pallidus pallidus

Substantia Nigra Substantia Nigra (midbrain) (midbrain)

Subthalamus (ventral to Subthalamus (ventral to thalamus) thalamus)

Vascular Supply to the HeadVascular Supply to the Head

Supplied by the two Supplied by the two internal carotid internal carotid arteries and the two arteries and the two vertebral arteries vertebral arteries

Circle of WillisCircle of Willis

Cerebral Arteries DistributionCerebral Arteries Distribution

Internal carotid arteriesInternal carotid arteries Arises from bifurcation of Arises from bifurcation of

common carotid artery and common carotid artery and enters skull through carotid enters skull through carotid canal canal

Branch of ophthalmic Branch of ophthalmic artery comes off just before artery comes off just before it enters the subarachnoid it enters the subarachnoid space and terminates as space and terminates as middle and anterior middle and anterior cerebral arteries cerebral arteries

Cerebral Arteries DistributionCerebral Arteries Distribution Middle cerebral arteryMiddle cerebral artery

Supplies bulk of lateral Supplies bulk of lateral surface of hemispheres surface of hemispheres

Supplies the posterior limb Supplies the posterior limb of internal capsule and of internal capsule and basal ganglia basal ganglia

Occlusion results in Occlusion results in spastic spastic paresisparesis of contralateral of contralateral lower face and upper limb lower face and upper limb and and anesthesia anesthesia of of contralateral face and contralateral face and upper limb upper limb

If left middle cerebral artery If left middle cerebral artery branches involved branches involved Wernicke’s or Broca’s Wernicke’s or Broca’s areas may be affected areas may be affected resulting in aphasiaresulting in aphasia

Cerebral Arteries DistributionCerebral Arteries Distribution Anterior cerebral arteryAnterior cerebral artery

Smaller terminal branch of Smaller terminal branch of internal carotid internal carotid

Supplies the medial Supplies the medial surface of frontal and surface of frontal and parietal lobes parietal lobes

Includes motor and Includes motor and sensory cortical areas for sensory cortical areas for the pelvis and lower limbs the pelvis and lower limbs

Supplies anterior 4/5 of Supplies anterior 4/5 of corpus callosum corpus callosum

Approximately one inch of Approximately one inch of frontal and parietal cortex frontal and parietal cortex

Occlusion will results in Occlusion will results in spastic paresisspastic paresis and and anesthesiaanesthesia of contralateral of contralateral lower limb lower limb

Urinary incontinence may Urinary incontinence may be present if bilateral be present if bilateral damagedamage

Cerebral Arteries DistributionCerebral Arteries Distribution Posterior cerebral arteryPosterior cerebral artery

Formed by terminal Formed by terminal bifurcation of basilar artery bifurcation of basilar artery

Supplies occipital and Supplies occipital and temporal cortex on inferior temporal cortex on inferior and lateral surfaces of and lateral surfaces of hemisphere hemisphere

Supplies occipital lobe and Supplies occipital lobe and posterior 2/3 of temporal posterior 2/3 of temporal lobe on medial surface of lobe on medial surface of hemisphere hemisphere

Supplies thalamus and Supplies thalamus and subthalamic nucleus subthalamic nucleus

Occlusion - results in Occlusion - results in homonymous hemianopsia homonymous hemianopsia of contralateral visual field of contralateral visual field with macular sparingwith macular sparing

Dural Venous SinusesDural Venous Sinuses

Ventricular SystemVentricular System Brain and spinal cord float within a protective bath of CSF Brain and spinal cord float within a protective bath of CSF Produced continuously by choroids plexus Produced continuously by choroids plexus Four ventricles Four ventricles

Two lateral ventricles deep within each cerebral Two lateral ventricles deep within each cerebral hemisphere hemisphere

Third ventricle located in midline within diencephalons Third ventricle located in midline within diencephalons Fourth ventricle located on dorsal surface of pons and Fourth ventricle located on dorsal surface of pons and

upper medulla upper medulla Ventricles connected resulting in flow of CSF Ventricles connected resulting in flow of CSF

Flow of CSFFlow of CSF

CSF flows from lateral ventricles CSF flows from lateral ventricles → → interventricular foramen of Monro interventricular foramen of Monro → → third third ventricle ventricle → → cerebral aqueduct cerebral aqueduct → → fourth fourth ventricle ventricle → → subarachnoid space either subarachnoid space either throught the foramen of Magendie or throught the foramen of Magendie or foramina Luschkaforamina Luschka

Cerebrospinal FluidCerebrospinal Fluid Adults produce 90 – 150 mL of total CSF Adults produce 90 – 150 mL of total CSF About 70 % secreted by choroids plexus located in parts About 70 % secreted by choroids plexus located in parts

of the lateral, third, and fourth ventricles, lined by highly of the lateral, third, and fourth ventricles, lined by highly vascularized ependymal cells vascularized ependymal cells

Almost all CSF returns to venous system by draining Almost all CSF returns to venous system by draining through arachnoid granulations into superior sagittal through arachnoid granulations into superior sagittal dural venous sinus dural venous sinus

Concentration of protein is much lower compared to Concentration of protein is much lower compared to serum serum

Few lymphocytes present; presence of PMN’s always Few lymphocytes present; presence of PMN’s always abnormal abnormal

RBCs may be present after traumatic spinal tap or RBCs may be present after traumatic spinal tap or subarachnoid hemorrhage subarachnoid hemorrhage

CSF AbnormalitiesCSF Abnormalities HydrocephalusHydrocephalus caused by excess volume or pressure of caused by excess volume or pressure of

CSF CSF Communicating hydrocephalusCommunicating hydrocephalus

Caused by oversecretion of CSF without obstruction in Caused by oversecretion of CSF without obstruction in the ventricles or by problems with absorption in the ventricles or by problems with absorption in subarachnoid space subarachnoid space

Noncommunication hydrocephalusNoncommunication hydrocephalus Caused by obstruction of CSF flow inside ventricular Caused by obstruction of CSF flow inside ventricular

system at foramen of Monro, cerebral aqueduct, or system at foramen of Monro, cerebral aqueduct, or fourth ventricle fourth ventricle

Could also be obstruction at foramina Magendie or Could also be obstruction at foramina Magendie or Luschka Luschka

Normal Pressure hydrocephalusNormal Pressure hydrocephalus

Blood Brain BarrierBlood Brain Barrier

Formed by capillary endothelium connected by Formed by capillary endothelium connected by tight junctions tight junctions

Astrocytes participate in maintenance of BBB Astrocytes participate in maintenance of BBB Numerous long processes with expanded Numerous long processes with expanded

vascular end-feet that attach to walls of vascular end-feet that attach to walls of capillaries capillaries

Water diffuses across BBB readily; glucose must Water diffuses across BBB readily; glucose must be actively transported acrossbe actively transported across

MeningesMeninges

Brain StemBrain Stem

Divisible into three Divisible into three continuous parts: continuous parts: midbrain, pons, midbrain, pons, medulla medulla

Home of origins of the Home of origins of the sites or termination of sites or termination of fibers in 9/12 CNs fibers in 9/12 CNs

Brain StemBrain Stem

Midbrain site of origin for Midbrain site of origin for CN III and CN IV CN III and CN IV

Pons site of entrance or Pons site of entrance or exit exit CN V, CN VI, CN VII, and CN V, CN VI, CN VII, and

CN VIII CN VIII

Medulla site of entrance Medulla site of entrance or exit or exit CN IX, X, and XII CN IX, X, and XII

Useful in diagnosing brain Useful in diagnosing brain stem injury stem injury

MidbrainMidbrain

Located between pons Located between pons

and diencephalon and diencephalon Cerebral aqueduct Cerebral aqueduct

passes throughpasses through

PonsPons

Located between medulla Located between medulla and midbrain; cerebellum and midbrain; cerebellum overlies overlies

Fourth ventricle found Fourth ventricle found between dorsal surface between dorsal surface and cerebellum and cerebellum

Ventral surface Ventral surface dominated by fibers dominated by fibers forming a ventral forming a ventral enlargement carrying enlargement carrying pontine fibers to middle pontine fibers to middle cerebellar peduncle (key cerebellar peduncle (key feature of pons)feature of pons)

PonsPons Aides in relaying Aides in relaying

messages in the brain, messages in the brain, and contains the and contains the pneumotaxic centres that pneumotaxic centres that help regulate respiration. help regulate respiration.

There are two main There are two main domains in the pons for domains in the pons for control of respirationcontrol of respiration apneustic center - lower apneustic center - lower

pons (promote inspiration)pons (promote inspiration) pneumotaxic center - upper pneumotaxic center - upper

pons (inhibiting effect)pons (inhibiting effect)

PonsPons

Blood to the pons Blood to the pons supplied by a number of supplied by a number of arteries.arteries. Pontine arteriesPontine arteries Anterior inferior cerebellar Anterior inferior cerebellar

artery (AICA)artery (AICA) Superior cerebellarSuperior cerebellar

MedullaMedulla

Above the spinal cord, Above the spinal cord, below the pons, and below the pons, and anterior to the anterior to the cerebellum.cerebellum.

MedullaMedulla It controls autonomic It controls autonomic

functions and relays functions and relays nerve signals between nerve signals between the brain and spinal cord.the brain and spinal cord.

The Medulla oblongata is The Medulla oblongata is responsible for controlling responsible for controlling several major autonomic several major autonomic functions of the body:functions of the body: respiration (via dorsal respiration (via dorsal

respiratory group and respiratory group and ventral respiratory group) ventral respiratory group)

blood pressureblood pressure heart rateheart rate reflex arcsreflex arcs vomitingvomiting

MedullaMedulla Blood to the medulla is Blood to the medulla is

supplied by a number of supplied by a number of arteries.arteries. Anterior spinal artery Anterior spinal artery Posterior inferior cerebellar Posterior inferior cerebellar

artery (PICA)artery (PICA) Direct branches of the Direct branches of the

vertebral arteryvertebral artery

IV Trochlear

III Oculomotor

VII Facial

VI Abducens

V Trigeminal

CEREBRAL HEMISPHERE

MIDBRAIN

PONS

MEDULLA

CRANIAL NERVESCRANIAL NERVES II Optic

I Olfactory

VIII Acoustic

XII Hypoglossal

XI Accessory

X Vagus

IX Glossopharyngeal

Cranial NervesCranial Nerves

Cranial NervesCranial Nerves

Spinal CordSpinal Cord

The The spinal cordspinal cord lies lies within the spinal within the spinal cavity, consisting of cavity, consisting of the the vertebral columnvertebral column, , the meninges, spinal the meninges, spinal nerves, spinal fluid, nerves, spinal fluid, blood vessels, and a blood vessels, and a cushion of adipose/fat cushion of adipose/fat tissue. tissue.

Spinal CordSpinal Cord Thirty-one pairsThirty-one pairs of nerves of nerves

connect to the spinal connect to the spinal cord. They have no cord. They have no special names, but are special names, but are numbered according to numbered according to the level of the spinal the level of the spinal column from which they column from which they emerge. There are emerge. There are 8 8 cervicalcervical (C1-C8), (C1-C8), 12 12 thoracicthoracic (T1-T12), (T1-T12), 5 5 lumbarlumbar (L1-L5), (L1-L5), 5 sacral5 sacral (S1-S5), and (S1-S5), and 1 coccygeal1 coccygeal pairs of spinal nerves. pairs of spinal nerves.

Spinal CordSpinal Cord

The spinal cord has The spinal cord has two general functions:two general functions:

1) It provides the two-1) It provides the two-way conduction way conduction routes to/from routes to/from ((afferent/efferentafferent/efferent) the ) the brainbrain

2) it serves as the reflex 2) it serves as the reflex center for all spinal center for all spinal reflexes. reflexes.

Spinal Cord and TractsSpinal Cord and Tracts

Spinal Cord and TractsSpinal Cord and Tracts

Spinothalamic tractSpinothalamic tract, carrying pain and , carrying pain and temperature impulses to the thalamus temperature impulses to the thalamus and the parietal lobe (sensory)and the parietal lobe (sensory)

Dorsal columnsDorsal columns, carrying position and , carrying position and pressure sense to the thalamus and the pressure sense to the thalamus and the parietal lobe (sensory)parietal lobe (sensory)

CorticospinalCorticospinal (or (or pyrimidalpyrimidal) ) tracttract, carrying , carrying impulses to initiate muscle activity from impulses to initiate muscle activity from the frontal lobe. (motor)the frontal lobe. (motor)

Spinothalamic TractSpinothalamic Tract

Dorsal ColumnDorsal Column

Reflex ArcReflex Arc

A reflex is an automatic, i.e."involuntary," A reflex is an automatic, i.e."involuntary," response of the body to some stimulus, response of the body to some stimulus, e.g. pupil dilation, to collect more light, at e.g. pupil dilation, to collect more light, at night. Reflexes have night. Reflexes have afferent afferent (signals (signals toto the CNS) and the CNS) and efferentefferent (signals (signals fromfrom the the CNS) components and may involve one CNS) components and may involve one nerve/synapse (nerve/synapse (monosynaptic reflexmonosynaptic reflex) or ) or multiple synapses (multiple synapses (polysynaptic reflexpolysynaptic reflex). ). The simplest spinal reflex is the The simplest spinal reflex is the tendon tendon reflexreflex, a monosynaptic reflex. , a monosynaptic reflex.

Reflex ArcReflex Arc

Peripheral Nervous SystemPeripheral Nervous System

Spinal NervesSpinal Nerves

All All cervical spinal nervescervical spinal nerves control control movement of the shoulder and arm movement of the shoulder and arm muscles and receive all sensory input from muscles and receive all sensory input from the skin, muscles, bones, and joints. After the skin, muscles, bones, and joints. After leaving the vertebral canal, they merge to leaving the vertebral canal, they merge to form form peripheral nervesperipheral nerves. The merger of . The merger of the spinal nerves in the neck region is the spinal nerves in the neck region is called the called the brachial plexusbrachial plexus. .

Brachial PlexusBrachial Plexus

Sensory Innervation of the HandSensory Innervation of the Hand


The The thoracic spinal nervesthoracic spinal nerves do not do not recombine into plexuses. The anterior recombine into plexuses. The anterior roots control the muscles of the abdomen roots control the muscles of the abdomen and back; the posterior roots receive and back; the posterior roots receive information from the abdomen, skin, and information from the abdomen, skin, and muscles and joints of the chest and upper muscles and joints of the chest and upper back. back.


The The lumbar and sacral nerveslumbar and sacral nerves, like the , like the cervical, do combine after leaving the cervical, do combine after leaving the vertebral canal. This merger, occuring in vertebral canal. This merger, occuring in the pelvis, is called the the pelvis, is called the lumbosacral lumbosacral plexusplexus, which controls the movement of, , which controls the movement of, and receives information from, the lower and receives information from, the lower extremities, bladder, and bowel. extremities, bladder, and bowel.

Lumbo Sacral PlexusLumbo Sacral Plexus

Sensory Innervation of the FootSensory Innervation of the Foot

The EndThe End

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Health & Medicine

Review Of Anatomy And Physiology Of The Nervous