Nervous system

NERVOUS SYSTEMNERVOUS SYSTEM is the master controlling and communicating is the master controlling and communicating

system of the body; works with other organ system;system of the body; works with other organ system;

electrical impulses which act as signaling device electrical impulses which act as signaling device and as a means of communicating with body cells and as a means of communicating with body cells are are specificspecific and cause an and cause an immediateimmediate response; response;

three overlapping functions:three overlapping functions:1.1. monitor changes occurring both inside and monitor changes occurring both inside and

outside the body (stimuli); the gathered input outside the body (stimuli); the gathered input is called SENSORY INPUT;is called SENSORY INPUT;

2.2. it process and interprets the sensory input it process and interprets the sensory input and decides on the input (INTEGRATION)and decides on the input (INTEGRATION)

3.3. it effects a response by activating muscles or it effects a response by activating muscles or glands (MOTOR OUTPUT)glands (MOTOR OUTPUT)

Structural Classifications:Structural Classifications:1.1. Central Nervous System (CNS)Central Nervous System (CNS) – consists of the – consists of the

brain and spinal cord;brain and spinal cord;

2.2. Peripheral Nervous System (PNS)Peripheral Nervous System (PNS) – outside the – outside the CNS; consists of the spinal nerves and cranial CNS; consists of the spinal nerves and cranial nervesnerves

Functional Classification: (concerned only with PNS Functional Classification: (concerned only with PNS structures) structures) 1.1. Sensory or Afferent divisionSensory or Afferent division – consists of nerves – consists of nerves

that convey impulses to the CNS from sensory that convey impulses to the CNS from sensory receptors located in various parts of the body;receptors located in various parts of the body;– Sensory fibers delivering impulses from the Sensory fibers delivering impulses from the

skin, skeletal muscles, and joints are called skin, skeletal muscles, and joints are called SOMATIC SENSORY FIBERS;SOMATIC SENSORY FIBERS;

– Sensory fibers transmitting impulses from the Sensory fibers transmitting impulses from the visceral organs are called VISCERAL visceral organs are called VISCERAL SENSORY FIBERS;SENSORY FIBERS;

2. Motor or Efferent division2. Motor or Efferent division – carries impulses from – carries impulses from the CNS the CNS to the effector organs, the muscles and to the effector organs, the muscles and glands;glands;a.a. Somatic Nervous System – allows conscious Somatic Nervous System – allows conscious

or voluntary control of our movements;or voluntary control of our movements;

b.b. Autonomic Nervous System – regulates Autonomic Nervous System – regulates events that are involuntary; such as the events that are involuntary; such as the activity of smooth and cardiac muscles and activity of smooth and cardiac muscles and glands;glands;

1.1. Sympathetic NSSympathetic NS2.2. Parasympathetic NSParasympathetic NS

STRUCTURE AND FUNCTIONSSTRUCTURE AND FUNCTIONS– the nervous system is made up of two principal the nervous system is made up of two principal

types of cells:types of cells:1.1. Supporting CellsSupporting Cells2.2. NeuronsNeurons

SUPPORTING CELLS SUPPORTING CELLS – these cells in the CNS are lumped together as these cells in the CNS are lumped together as

NEUROGLIANEUROGLIA;;– generally made up of cells that generally made up of cells that support, insulate, support, insulate,

and protectand protect the delicate neurons; the delicate neurons;– types of neuroglia:types of neuroglia:

1.1. AstrocytesAstrocytes – most abundant; form a living – most abundant; form a living barrier between capillaries and neurons; play barrier between capillaries and neurons; play a role in making exchanges between the a role in making exchanges between the capillaries and neurons;capillaries and neurons;

2. Microglia2. Microglia – are phagocytes that dispose of – are phagocytes that dispose of debris (dead brain cells, bacteria, etc.) debris (dead brain cells, bacteria, etc.)

3. Ependymal cells3. Ependymal cells – line the cavities of the brain – line the cavities of the brain and spinal cord; their beating cilia helps and spinal cord; their beating cilia helps circulate CSF and forms a protective cushion circulate CSF and forms a protective cushion around the CNS;around the CNS;

4. Oligodendrocytes4. Oligodendrocytes – forms – forms myelin sheathmyelin sheath around the nerve fibers in the around the nerve fibers in the CNSCNS;;

Supporting Cells in the PNS comes in two major forms:Supporting Cells in the PNS comes in two major forms:1.1. Schwann Cells – form Schwann Cells – form myelin sheathmyelin sheath around around

the nerve fibers in the the nerve fibers in the PNSPNS;;

2.2. Satellite Cells – act as protective, cushioning Satellite Cells – act as protective, cushioning cells;cells;

NEURONSNEURONS– also called also called nerve cellsnerve cells;;– are the functional unit of are the functional unit of

the nervous system;the nervous system;– are highly specialized to are highly specialized to

transmit nerve impulsestransmit nerve impulses from one part of the from one part of the body to another;body to another;

– parts:parts:1.1. Cell Body – contains Cell Body – contains

the nucleus and is the nucleus and is the metabolic center the metabolic center of the cell;of the cell;

2.2. Dendrites – neuron Dendrites – neuron processes that processes that conduct nerve conduct nerve impulses toward the impulses toward the cell body;cell body;

3.3. Axons – processes Axons – processes that conduct nerve that conduct nerve impulses away from impulses away from the cell body;the cell body;

most long nerve fibers are covered with a whitish, most long nerve fibers are covered with a whitish, fatty material, called MYELIN;fatty material, called MYELIN;

- also protects and insulates the fibers and also protects and insulates the fibers and increases the transmission rate of nerve increases the transmission rate of nerve impulses;impulses;

- most axons are wrapped with myelin called most axons are wrapped with myelin called MYELIN SHEATH;MYELIN SHEATH;

- MULTIPLE SCLEROSISMULTIPLE SCLEROSIS

Clusters of neuron cell bodies in the Clusters of neuron cell bodies in the CNSCNS are called are called NUCLEI;NUCLEI;

Small collections of cell bodies in the Small collections of cell bodies in the PNSPNS are called are called GANGLIA;GANGLIA;

Functional Classification of a Neuron:Functional Classification of a Neuron:

1.1. Sensory / Afferent Neurons – carrying Sensory / Afferent Neurons – carrying impulses from the sensory receptors to impulses from the sensory receptors to the CNS;the CNS;

2.2. Motor / Efferent Neurons – carrying Motor / Efferent Neurons – carrying impulses from the CNS to the viscera impulses from the CNS to the viscera and/or muscles and glands;and/or muscles and glands;

3.3. Interneurons – connect the motor and Interneurons – connect the motor and sensory neurons;sensory neurons;

Structural Classification of Neurons (based on the Structural Classification of Neurons (based on the no. of processes)no. of processes)

1.1. Multipolar Neurons – several processes; most Multipolar Neurons – several processes; most common structural type;common structural type;

2.2. Bipolar Neurons – contain two processes, an Bipolar Neurons – contain two processes, an axon and a dendrite;axon and a dendrite;

3.3. Unipolar Neurons – contain a single neuronal Unipolar Neurons – contain a single neuronal process;process;

Neurons have two major functional properties:Neurons have two major functional properties:1.1. Irritability – ability to respond to a stimulus and Irritability – ability to respond to a stimulus and

convert it to a nerve impulse;convert it to a nerve impulse;

2.2. Conductivity – ability to transmit the impulse to Conductivity – ability to transmit the impulse to other neurons, muscles, or glands;other neurons, muscles, or glands;

REFLEXES – are rapid, predictable, and REFLEXES – are rapid, predictable, and involuntary response to stimuli;involuntary response to stimuli;

- Occur over neural pathways called Occur over neural pathways called REFLEX REFLEX ARCARC (a complete circuit consisting of a (a complete circuit consisting of a sensory neuron ending in the spinal cord, sensory neuron ending in the spinal cord, connecting neuron within the cord, and a connecting neuron within the cord, and a motor neuron to a muscle );motor neuron to a muscle );

- Autonomic ReflexesAutonomic Reflexes regulate the activity of regulate the activity of smooth muscles, the heart, and glands; ex. smooth muscles, the heart, and glands; ex. Salivary and Pupillary reflexSalivary and Pupillary reflex

- Somatic ReflexesSomatic Reflexes includes all reflexes that includes all reflexes that stimulate the skeletal muscles;stimulate the skeletal muscles;

CENTRAL NERVOUS SYSTEMCENTRAL NERVOUS SYSTEM– originates in the originates in the NEURAL TUBENEURAL TUBE;;

– is the part is the part enclosedenclosed by bone or the cranium; by bone or the cranium;

– it includes the BRAIN and the SPINAL CORD;it includes the BRAIN and the SPINAL CORD;

– the chambers of the brain are called VENTRICLES the chambers of the brain are called VENTRICLES (filled with (filled with cerebrospinal fluidcerebrospinal fluid))

– Four Major Parts:Four Major Parts:

1.1. CerebrumCerebrum

2.2. DiencephalonDiencephalon

3.3. BrainstemBrainstem

4.4. CerebellumCerebellum

Anatomy of the BrainAnatomy of the Brain– the brain is the largest and most complex mass the brain is the largest and most complex mass

of nervous tissue in the body;of nervous tissue in the body;

Four major regions of the brain:Four major regions of the brain:

1.1. Cerebral Hemispheres (cerebrum)Cerebral Hemispheres (cerebrum)– are paired superior part of the brain;are paired superior part of the brain;– enclose and obscure most of the brain stem;enclose and obscure most of the brain stem;– GyriGyri – elevated ridges of tissue on the surface of – elevated ridges of tissue on the surface of

the cerebral hemispheres;the cerebral hemispheres;– SulciSulci – hollow grooves that separates the gyri; – hollow grooves that separates the gyri;– The cerebral hemispheres are separated by a The cerebral hemispheres are separated by a

single deep fissure called the LONGITUDINAL single deep fissure called the LONGITUDINAL FISSURE;FISSURE;

Lobes of the brain:Lobes of the brain:1.1. Parietal Lobe – Parietal Lobe –

area for somatic area for somatic sensory;sensory;

2.2. Frontal Lobe – area Frontal Lobe – area for motor for motor movement;movement;

3.3. Occipital Lobe – Occipital Lobe – area for vision;area for vision;

4.4. Temporal Lobe – Temporal Lobe – auditory and auditory and olfactory area;olfactory area;

A specialized area that is involved in our ability to A specialized area that is involved in our ability to speak is called BROCA’S AREA;speak is called BROCA’S AREA;

Areas involved in higher intellectual reasoning and Areas involved in higher intellectual reasoning and language comprehension is called WERNICKE’S AREA;language comprehension is called WERNICKE’S AREA;

Layers of cell bodies of Neurons:Layers of cell bodies of Neurons:

1.1. Gray Matter – outermost layer; functional area;Gray Matter – outermost layer; functional area;

2.2. White Matter – deeper layer; composed of White Matter – deeper layer; composed of fibers fibers tracts carrying impulsestracts carrying impulses to or from the cortex; form to or from the cortex; form tracts or bundles that connect two parts of the tracts or bundles that connect two parts of the cerebrum to other parts of the brain.cerebrum to other parts of the brain.

The cerebral hemispheres are connected by one large The cerebral hemispheres are connected by one large fiber tract called CORPUS CALLOSUM;fiber tract called CORPUS CALLOSUM;

2. Diencephalon2. Diencephalon– Or interbrain; Or interbrain;

– Sits atop the brainstem and is enclosed by the Sits atop the brainstem and is enclosed by the cerebral hemispheres;cerebral hemispheres;

– Major structures:Major structures:

a.a. Thalamus – encloses the Thalamus – encloses the third ventriclethird ventricle, is , is a relay station for sensory impulses a relay station for sensory impulses passing upward to the sensory cortex;passing upward to the sensory cortex;

b.b. Hypothalamus – forms the floor of the third Hypothalamus – forms the floor of the third ventricle; is an important autonomic NS ventricle; is an important autonomic NS center because it plays a role in regulation center because it plays a role in regulation of body temperature, water balance, and of body temperature, water balance, and metabolism; also secretes oxytocin and metabolism; also secretes oxytocin and ADH;ADH;

3. Brainstem3. Brainstem– Is found on the lower part of the brain hidden by Is found on the lower part of the brain hidden by

the cerebral hemispheres;the cerebral hemispheres;

– Provides a pathway for ascending and Provides a pathway for ascending and descending tracts;descending tracts;

– Their nuclei form the cranial nerves and control Their nuclei form the cranial nerves and control vital activities such as breathing and BP;vital activities such as breathing and BP;

– RETICULAR FORMATION – is a diffuse mass RETICULAR FORMATION – is a diffuse mass that extends in the entire length of the that extends in the entire length of the brainstem; brainstem;

Parts of Brainstem:Parts of Brainstem:

1.1. Midbrain – contains Midbrain – contains the cerebral aqueduct the cerebral aqueduct of Sylvius; of Sylvius;

– contains nuclei that contains nuclei that act as reflex centers act as reflex centers involved with vision involved with vision and hearing;and hearing;

Parts of Brainstem…..Parts of Brainstem…..

2. Pons – rounded 2. Pons – rounded structure that structure that protrudes below the protrudes below the midbrain; midbrain;

– contains many fiber contains many fiber tracts; tracts;

– involved in control involved in control of breathing; of breathing;

– also contains nuclei also contains nuclei of several cranial of several cranial nerves;nerves;

Parts of Brainstem…Parts of Brainstem…

3. Medulla Oblongata – is 3. Medulla Oblongata – is the most inferior part the most inferior part of the brainstem; of the brainstem;

– also an important also an important fiber tract area;fiber tract area;

– Also contains nuclei Also contains nuclei that regulate vital that regulate vital visceral functions;visceral functions;

– Contains centers Contains centers that control heart that control heart rate, BP, breathing, rate, BP, breathing, swallowing, and swallowing, and vomiting;vomiting;

4. Cerebellum4. Cerebellum

– Is a Is a large, cauliflowerlikelarge, cauliflowerlike structure that projects structure that projects dorsally from under the dorsally from under the occipital lobe of the occipital lobe of the cerebrum;cerebrum;

– Provides the Provides the precise timing precise timing or good coordination of or good coordination of skeletal muscle activityskeletal muscle activity and and controls our controls our balance,balance, posture, and equilibrium;posture, and equilibrium;

– AtaxiaAtaxia means clumsy, means clumsy, disorganized movements disorganized movements when the cerebellum is when the cerebellum is injured;injured;

PROTECTION OF THE CNSPROTECTION OF THE CNS

because of the delicate nature of the neurons, the body because of the delicate nature of the neurons, the body provides many protective structures to protect them:provides many protective structures to protect them:

1.1. SkullSkull

2.2. Vertebral ColumnVertebral Column

3.3. Meninges – this are three connective tissue Meninges – this are three connective tissue membranes that covers and protect the CNS;membranes that covers and protect the CNS;

The The outermostoutermost layer (DURA MATER) is a layer (DURA MATER) is a double-layered membrane that surrounds double-layered membrane that surrounds the brain;the brain;

The The middle meningealmiddle meningeal layer is the weblike layer is the weblike ARACHNOID MATER;ARACHNOID MATER;

The The innermost layerinnermost layer is the PIA MATER is the PIA MATER which clings tightly to the surface of the which clings tightly to the surface of the brain and spinal cord;brain and spinal cord;

The FALX CEREBRI is the fold of dura mater that The FALX CEREBRI is the fold of dura mater that passes transversely across the upper end of the passes transversely across the upper end of the posterior cranial fossa in the transverse fissure;posterior cranial fossa in the transverse fissure;– also separates the occipital lobe of the cerebrum also separates the occipital lobe of the cerebrum

from the upper surface of the cerebellum;from the upper surface of the cerebellum;

The SUBARACHNOID SPACE is filled with CSF;The SUBARACHNOID SPACE is filled with CSF;

ARACHNOID VILLI absorb CSF into the venous ARACHNOID VILLI absorb CSF into the venous blood; blood;

MENINGITIS – inflammation of the meninges;MENINGITIS – inflammation of the meninges;

ENCEPHALITIS – inflammation of the brain;ENCEPHALITIS – inflammation of the brain;

4. Cerebrospinal Fluid (CSF)4. Cerebrospinal Fluid (CSF)– Is a watery broth similar to blood plasma;Is a watery broth similar to blood plasma;– Formed by the Formed by the CHOROID PLEXUS;CHOROID PLEXUS;– Is found in and around the brain and spinal Is found in and around the brain and spinal

cord which forms a watery cushion that cord which forms a watery cushion that protects these fragile structures against protects these fragile structures against blows and trauma;blows and trauma;

EPIDURAL SPACE – is the interval EPIDURAL SPACE – is the interval between the dura between the dura mater and cranial bonesmater and cranial bones; in the SPINE, it is the ; in the SPINE, it is the space space between the dura mater and the vertebral between the dura mater and the vertebral canal;canal;

SUBDURAL SPACE – is the interval between the SUBDURAL SPACE – is the interval between the arachnoid and dura materarachnoid and dura mater of the brain or the spinal of the brain or the spinal cord;cord;

FLOW OF CSFFLOW OF CSFCHOROID PLEXUSCHOROID PLEXUS

LATERAL VENTRICLESLATERAL VENTRICLES

FORAMEN OF MONROEFORAMEN OF MONROE

THIRD VENTRICLETHIRD VENTRICLE

AQUEDUCT OF AQUEDUCT OF SYLVIUSSYLVIUS

FOURTH VENTRICLEFOURTH VENTRICLE

FORAMEN OF FORAMEN OF MAGENDIEMAGENDIE AND AND LUSCHKALUSCHKA

SUBARACHNOID SPACESUBARACHNOID SPACE (space between the arachnoid and pia mater) (space between the arachnoid and pia mater)

ARACHNOID VILLI DURAL SINUSESARACHNOID VILLI DURAL SINUSES VENOUS VENOUS SYSTEMSYSTEM

THE BLOOD BRAIN BARRIERTHE BLOOD BRAIN BARRIER– the brain is very dependent on a constant the brain is very dependent on a constant

environment;environment;

– separates the neurons from blood-borne separates the neurons from blood-borne substances;substances;

– composed of least permeable capillaries in the composed of least permeable capillaries in the body;body;

– water-soluble substances like water, glucose, and water-soluble substances like water, glucose, and essential amino acids pass easily;essential amino acids pass easily;

– is virtually useless against fats, respiratory gases, is virtually useless against fats, respiratory gases, and other fat-soluble molecules that diffuse easily and other fat-soluble molecules that diffuse easily thru all the plasma membranes;thru all the plasma membranes;

SPINAL CORDSPINAL CORD– is a glistening white is a glistening white

continuation of the continuation of the brainstem;brainstem;

– provides a two-way provides a two-way conduction pathway to conduction pathway to and from the brain;and from the brain;

– enclosed within the enclosed within the vertebral or spinal vertebral or spinal column;column;

– extends from the extends from the FORAMEN MAGNUM of FORAMEN MAGNUM of the skull to the 1st or 2nd the skull to the 1st or 2nd lumbar vertebra;lumbar vertebra;

– it is protected and it is protected and cushioned by meninges;cushioned by meninges;

In humans, 31 pairs In humans, 31 pairs of spinal nerves of spinal nerves arise from the cord;arise from the cord;

Collection of spinal Collection of spinal nerves at the nerves at the inferior end of the inferior end of the vertebral canal is vertebral canal is called CAUDA called CAUDA EQUINA;EQUINA;

the gray matter of the spinal cord the gray matter of the spinal cord is H-shaped and is found more is H-shaped and is found more interior;interior;

the two posterior projections are the two posterior projections are the DORSAL or POSTERIOR the DORSAL or POSTERIOR HORNS for HORNS for sensorysensory functions; functions;

the two anterior projections are the two anterior projections are the VENTRAL or ANTERIOR the VENTRAL or ANTERIOR HORNS for HORNS for motor functionmotor function of the of the somatic nervous system somatic nervous system (voluntary);(voluntary);

the LATERAL HORN is a bulge on the LATERAL HORN is a bulge on each limb of gray substance in the each limb of gray substance in the thoracic and upper lumbar thoracic and upper lumbar segments; segments;

the gray matter surrounds the the gray matter surrounds the central canal of the cord which central canal of the cord which contains the CSF;contains the CSF;

PLEXUSES:PLEXUSES:1.1. Cervical PlexusCervical Plexus – on each side of the body is made – on each side of the body is made

up of the ventral divisions of the C1-C4;up of the ventral divisions of the C1-C4;Supplies the skin and muscles of the scalp, Supplies the skin and muscles of the scalp, neck, and part of the face;neck, and part of the face;The PHRENIC NERVE originates from this The PHRENIC NERVE originates from this plexus;plexus;

2.2. Brachial PlexusBrachial Plexus – formed by C5-T1; lies posterior to – formed by C5-T1; lies posterior to the clavicle;the clavicle;

Supplies the shoulder and upper limb;Supplies the shoulder and upper limb;

3.3. Lumbar PlexusLumbar Plexus – formed by L1-L4; lies in the – formed by L1-L4; lies in the posterior abdomen in the area of the psoas muscle; posterior abdomen in the area of the psoas muscle; supplies the FEMORAL NERVE;supplies the FEMORAL NERVE;

4.4. Sacral PlexusSacral Plexus – formed by L4-S3; located within the – formed by L4-S3; located within the pelvis on the posterolateral wall; the largest branch pelvis on the posterolateral wall; the largest branch is the SCIATIC NERVE;is the SCIATIC NERVE;

PERIPHERAL NERVOUS SYSTEMPERIPHERAL NERVOUS SYSTEM

– consists of nerves and scattered groups of neuronal consists of nerves and scattered groups of neuronal cell bodies found outside the CNS;cell bodies found outside the CNS;

A. NERVESA. NERVES– Is a bundle of neuron fibers found outside the CNS;Is a bundle of neuron fibers found outside the CNS;

Afferent / Sensory NerveAfferent / Sensory NerveEfferent / Motor NerveEfferent / Motor Nerve

B. CRANIAL NERVES (CN)B. CRANIAL NERVES (CN)– arise directly from the base of the brain (brainstem), arise directly from the base of the brain (brainstem),

and are not associated with the spinal cord;and are not associated with the spinal cord;– The The 12 pairs12 pairs primarily primarily serve the head and neckserve the head and neck exceptexcept

for the CN X (vagus) which extends to the thoracic and for the CN X (vagus) which extends to the thoracic and abdominal cavities;abdominal cavities;

– most cranial nerves are mixed (both motor and most cranial nerves are mixed (both motor and sensory function);sensory function);

– ““OOOTTAFAGVAH”OOOTTAFAGVAH”

CNCN I – olfactory n. I – olfactory n. II – optic n. II – optic n. III – oculomotor n.III – oculomotor n.

IV – trochlear n. IV – trochlear n. V – trigeminal n.V – trigeminal n. VI – abducens n.VI – abducens n.

VII – facial n.VII – facial n.VIII – auditory n.VIII – auditory n.

IX – glossopharyngeal nIX – glossopharyngeal nX – vagus n.X – vagus n.

XI – spinal XI – spinal accessory accessory

n.n.XII – hypoglossal XII – hypoglossal

n. n. “Pls. read your book!”

AUTONOMIC NERVOUS SYSTEMAUTONOMIC NERVOUS SYSTEM– is the motor subdivision of the PNS that is the motor subdivision of the PNS that

controls body activities automatically;controls body activities automatically;

– regulates cardiac muscle activity, smooth regulates cardiac muscle activity, smooth muscle contraction, and secretion of exocrine muscle contraction, and secretion of exocrine glands;glands;

– has a chain of two motor neurons:has a chain of two motor neurons:1.1. Preganglionic axons – axons Preganglionic axons – axons before before the the

ganglion; leaves the CNS to synapse with the ganglion; leaves the CNS to synapse with the second motor neuron in a ganglion outside second motor neuron in a ganglion outside the CNS;the CNS;

2.2. Postganglionic axons – the axon extends to Postganglionic axons – the axon extends to the organ it serves;the organ it serves;

two divisions (usually they are two divisions (usually they are antagonistic)antagonistic)

1.1. Sympathetic NS (thoracolumbar division) – is Sympathetic NS (thoracolumbar division) – is often called the “fight-or-flight” system;often called the “fight-or-flight” system;

– Controls body functions that are essential Controls body functions that are essential for for survival;survival;

– Effects:Effects:1.1. Increases heart rateIncreases heart rate2.2. Increases BPIncreases BP3.3. Bronchial dilationBronchial dilation4.4. Decreases peristalsisDecreases peristalsis5.5. Dilated pupilsDilated pupils

2.2. Parasympathetic NS (craniosacral Parasympathetic NS (craniosacral division)division)

is most active when the body is is most active when the body is at at restrest and not threatened in any and not threatened in any way;way;

Concerned with normal body Concerned with normal body functions, usually opposite the functions, usually opposite the SNS;SNS;

BLOOD SUPPLY OF THE BRAIN:BLOOD SUPPLY OF THE BRAIN:– the brain is supplied by a specialized form of the brain is supplied by a specialized form of

blood vessels called the CIRCLE OF WILLIS;blood vessels called the CIRCLE OF WILLIS;

– Arteries that supply the brain:Arteries that supply the brain:

1.1. internal carotid artery – branch of the internal carotid artery – branch of the common carotid artery;common carotid artery;

2.2. vertebral artery – branch of the subclavian vertebral artery – branch of the subclavian artery;artery;

3.3. middle meningeal artery – branch of the middle meningeal artery – branch of the external carotid artery;external carotid artery;