155 Anatomy-CNS-2013-14

DR. T.C. MATHEW, Kuwait University

CENTRAL CENTRAL NERVOUSNERVOUSSYSTEMSYSTEM


Nervous TissueNervous Tissue

Each nerve cell consists of a central portion containing the nucleus, known as the cell body, and processes that arise from the cell body, the axons and dendrites.

NEURONS AND GLIAL CELLS.

Neurons transmit nerve messages.

Glial cells are supporting cells that surround the neurons


SynapseSynapse

The junction between a nerve cell and another cell is called a synapse.

Messages travel within the neuron as an electrical action potential.

The space between two cells is known as the synaptic cleft.

To cross the synaptic cleft requires the actions of neurotransmitters.


NEUROGLIA

Neuroglia is non-excitable nervous tissue that supports and insulates nerve cells in the central and peripheral parts of the nervous system. Glial cells fill in the spaces not occupied by neurons and blood vessels and provide structural and metabolic support for the nerves. The myelin sheath surrounding myelinated nerves is made from neuroglia.

CNS

OLIGODENDROCYTESASTROCYTESMICROGLIAEPENDYMA

PNS

SCHWANN CELLS

SATELLITE CELLS


Nervous TissueNervous Tissue

Endoneurium – layer of delicate connective tissue surrounding the axon

Nerve fascicles – groups of axons bound into bundles

Perineurium – connective tissue wrapping surrounding a nerve fascicle

Epineurium – whole nerve is surrounded by tough fibrous sheath


Peripheral nervous system (PNS) Outside the CNS Consists of nerves extending from

brain and spinal cord Cranial nerves Spinal nerves

Peripheral nerves link all regions of the body to the CNS

Basic Divisions of the Basic Divisions of the Nervous SystemNervous System

Central nervous system (CNS) Brain and spinal cord Integrating and command center


Sensory (afferent) signals picked up by sensory receptors Carried by nerve fibers of PNS to the CNS

Motor (efferent) signals are carried away from the CNS Innervate muscles and glands

Sensory Input and Motor OutputSensory Input and Motor Output


Neurons Classified by FunctionNeurons Classified by Function

Most neuronal cell bodies are located within the CNS, protected by bones of the skull and vertebral column

Ganglia – clusters of cell bodies, that lie along nerves in the PNS


Reflex arcReflex arc Reflex arcs – simple chains of neurons Simple reflex arc- a two neuron pathway- elicits

contraction of muscles Afferent- carries sensory impulse to the nervous

system Efferent- carries motor impulse out of the central

nervous system


THE CENTRAL NERVOUS SYTEM


Central nervous systemCentral nervous system

Central nervous system (CNS) consists of the brain and the Central nervous system (CNS) consists of the brain and the spinal cord. spinal cord. The brain lies in the cranial cavity. The brain lies in the cranial cavity. The average human brain weighs about 1,400 grams (3 lb). The average human brain weighs about 1,400 grams (3 lb).

The brain consists of:The brain consists of:

CEREBRUM.CEREBRUM.DIENCEPHALONSDIENCEPHALONSBRAIN STEM AND BRAIN STEM AND CEREBELLUM, CEREBELLUM,


The cerebrumThe cerebrumThe brain can be divided down the middle The brain can be divided down the middle lengthwise into two halves called the cerebral lengthwise into two halves called the cerebral hemispheres. hemispheres. Outer rim of gray matter is the cerebral cortex. Outer rim of gray matter is the cerebral cortex. Deep to it lies the cerebral white matter. Deep to it lies the cerebral white matter.

The right and left sides of the cerebral The right and left sides of the cerebral cortex are connected by a cortex are connected by a thick band of thick band of nerve fibersnerve fibers called the called the "corpus callosum"."corpus callosum".


The Cerebral HemispheresThe Cerebral Hemispheres

Fissures – deep grooves – separate major regions of the brain Transverse fissure – separates cerebrum and cerebellum Longitudinal fissure – separates cerebral hemispheres

Sulci – grooves on the surface of the cerebral hemispheres

Gyri – twisted ridges between sulci Prominent gyri and sulci are similar in all people


The Cerebral The Cerebral HemispheresHemispheres

Deeper sulci divide cerebrum into lobes

Lobes are named for the skull bones overlying them

Central sulcus separates frontal and parietal lobes Bordered by two gyri

Precentral gyrus Postcentral gyrus

Parieto-occipital sulcus Separates the occipital from

the parietal lobe Lateral sulcus

Separates temporal lobe from parietal and frontal lobes

Insula – deep within the lateral sulcus


Lobes of cerebrumLobes of cerebrum

Central sulcus- divides to frontal and parietal lobe. –Central sulcus- divides to frontal and parietal lobe. –Precentral gyrus- primary motor area. Precentral gyrus- primary motor area. Post central gyrus- primary somatosensory area. Post central gyrus- primary somatosensory area.


The cerebrumThe cerebrumLateral cerebral sulcus separates the frontal lobe from Lateral cerebral sulcus separates the frontal lobe from temporal lobe. temporal lobe. Parieto-occipital sulcus separates parietal lobe from the Parieto-occipital sulcus separates parietal lobe from the occipital lobe. occipital lobe. Insula- lies in the lateral cerebral sulcus, deep to parietal Insula- lies in the lateral cerebral sulcus, deep to parietal frontal and temporal lobes.frontal and temporal lobes.


OCCIPITAL LOBEOCCIPITAL LOBELocated at the back of the brain, behind the Located at the back of the brain, behind the parietal lobe and temporal lobe. parietal lobe and temporal lobe. Concerned with many aspects of vision.Concerned with many aspects of vision.


FRONTAL LOBEFRONTAL LOBELocated in front of the central sulcus. Located in front of the central sulcus. Concerned with reasoning, planning, parts of Concerned with reasoning, planning, parts of speech and movement (motor cortex), emotions, speech and movement (motor cortex), emotions, and problem-solving.and problem-solving.


TEMPORAL LOBE TEMPORAL LOBE Located below the lateral fissure. Located below the lateral fissure. Concerned with perception and recognition of Concerned with perception and recognition of auditory stimuli (hearing) and memory auditory stimuli (hearing) and memory (hippocampus).(hippocampus).


PARIETAL LOBE PARIETAL LOBE Located behind the central sulcus. Located behind the central sulcus. Concerned with perception of stimuli related to Concerned with perception of stimuli related to touch, pressure, temperature and pain.touch, pressure, temperature and pain.


The Cerebral HemispheresThe Cerebral Hemispheres

Home of our conscious mind Enables us to:

Be aware of ourselves and our sensations Initiate and control voluntary movementsCommunicate, remember, and

understand


Basal NucleiBasal Nuclei A group of nuclei deep within the cerebral white

matter Caudate nucleus – arches over the thalamus Lentiform nucleus – “lens shaped” Amygdala – sits on top of the caudate nucleu

Lentiform nucleus Divided into two parts

Globus pallidus Putamen


DIENCEPHALON


The DiencephalonThe Diencephalon

Forms the center core of the forebrain

Surrounded by the cerebral hemispheres

Composed of three paired structures: Thalamus, hypothalamus,

and epithalamus Border the third ventricle Primarily composed of gray

matter

Diencephalon extends from cerebrum to brain stem. Diencephalon extends from cerebrum to brain stem.


DiencephalonDiencephalon

ThalamusThalamus

Thalamus makes up 80% of diencephalon. Thalamus makes up 80% of diencephalon.

Thalamus is involved in sensory and motor Thalamus is involved in sensory and motor integration. integration.


EpithalamusEpithalamus

Epithalamus lies superior and posterior to thalamus. Epithalamus lies superior and posterior to thalamus. It contains the pineal gland and habenular nuclei.It contains the pineal gland and habenular nuclei. (Pineal gland: melatonin- biological clock; (Pineal gland: melatonin- biological clock; Habenular nuclei: Olfaction- emotional response to odors).Habenular nuclei: Olfaction- emotional response to odors).

SubthalamusSubthalamus

Subthalamus lies below the thalamus. Subthalamus lies below the thalamus.

It is involved in the control of movements.It is involved in the control of movements.


Functions of the ThalamusContains approximately a dozen major nuclei

Send axons to regions of the cerebral cortex

Nuclei act as relay stations for incoming sensory messages


Functions of the Hypothalamus Control of the autonomic nervous system Control of emotional responses Regulation of body temperature Regulation of hunger and thirst sensations Control of behavior Regulation of sleep-wake cycles Control of the endocrine system Formation of memory


The brain stemThe brain stem

It is the region It is the region between the spinal between the spinal cord and diencephalon cord and diencephalon


The brain stem consists of The brain stem consists of

MIDBRAIN, PONS AND MEDULLA OBLONGATAMIDBRAIN, PONS AND MEDULLA OBLONGATA

In addition to In addition to these regions a these regions a netlike region of netlike region of interspersed interspersed gray and white gray and white matter called matter called reticular reticular formationformation extends through extends through the brain stem.the brain stem.


Midbrain (Mesencephalon)Midbrain (Mesencephalon)

The midbrain lies between pons and diencephalons. The midbrain lies between pons and diencephalons. It is about 2.5 cm. It is about 2.5 cm.

The anterior part contains a pair of tracts called The anterior part contains a pair of tracts called cerebral pedunclescerebral peduncles containing axons of motor containing axons of motor neurons that relay impulses from the cerebrum to the neurons that relay impulses from the cerebrum to the spinal cord, medulla and pons as well as sensory spinal cord, medulla and pons as well as sensory neurons that extend from the medulla to the neurons that extend from the medulla to the thalamus. thalamus.



The superior part contains four rounded elevations The superior part contains four rounded elevations called called colliculicolliculi. .

Superior colliculiSuperior colliculi are responsible for co-ordinating are responsible for co-ordinating movements of the eye balls in response to visual and movements of the eye balls in response to visual and other stimuli. other stimuli.

Inferior colliculiInferior colliculi co-ordinate movements of the head co-ordinate movements of the head and trunk in response to auditory stimuli and and trunk in response to auditory stimuli and startle startle reflexreflex (sudden response of the head and body when (sudden response of the head and body when surprised by loud noises).surprised by loud noises).



The nuclei of the midbrain are substantia nigra and red nuclei. The nuclei of the midbrain are substantia nigra and red nuclei.

Substantia nigra means black substance. Substantia nigra means black substance.

Dopaminergic neurons from substantia nigra extend to basal ganglia and Dopaminergic neurons from substantia nigra extend to basal ganglia and help control subconscious muscle activities. help control subconscious muscle activities.

Loss of these neurons lead to Parkinson disease. Loss of these neurons lead to Parkinson disease.



Red nuclei appear red coloured due to rich blood supply and an iron containing Red nuclei appear red coloured due to rich blood supply and an iron containing pigment. pigment.

Together with cerebellum it coordinate muscular movements. Together with cerebellum it coordinate muscular movements.

Axons from cerebellum and cerebral cortex synapse in the red nuclei. Axons from cerebellum and cerebral cortex synapse in the red nuclei.



Brain stem contains a broad region where the white Brain stem contains a broad region where the white matter and grey matter show a netlike appearance. matter and grey matter show a netlike appearance.

This region is called This region is called reticular formationreticular formation. .



Neurons of the reticular formation have both Neurons of the reticular formation have both sensory and motor functions. sensory and motor functions.

Reticular activating system (RAS), a part of Reticular activating system (RAS), a part of the reticular formation consists of sensory the reticular formation consists of sensory axons that project to the cerebral cortex. axons that project to the cerebral cortex.

RAS helps to maintain consciousness.RAS helps to maintain consciousness.


PonsPons

Pons lies superior to the Pons lies superior to the medulla and anterior to the medulla and anterior to the cerebellum (~2.5 cm). cerebellum (~2.5 cm).

Pons contains tracts that Pons contains tracts that connect the right and left side connect the right and left side of the cerebellum as well as of the cerebellum as well as ascending sensory and ascending sensory and descending motor tracts. descending motor tracts.


Pons lies superior to the medulla Pons lies superior to the medulla and anterior to the cerebellumand anterior to the cerebellum


PonsPons

It contains the pontine nuclei. It contains the pontine nuclei.

These nuclei are the sites at which signals for These nuclei are the sites at which signals for voluntary movements that originate in the cerebral voluntary movements that originate in the cerebral cortex are relayed into the cerebellum. cortex are relayed into the cerebellum.

Other nuclei present in the pons include Other nuclei present in the pons include apneustic apneustic and pneumotaxicand pneumotaxic areas that are involved in the areas that are involved in the control of breathing.control of breathing.


Nuclei present Nuclei present in the ponsin the pons

NUCLEI OF NUCLEI OF CRANIAL NERVES CRANIAL NERVES

trigeminal (V), trigeminal (V), abducens (VI), abducens (VI), fascial (VII) and fascial (VII) and vestibulocochlear (VIII).vestibulocochlear (VIII).


Medulla oblongata (Medulla)Medulla oblongata (Medulla)

The medulla oblongata begins The medulla oblongata begins at foramen magnum and at foramen magnum and extends to the inferior border extends to the inferior border of the pons (~ 3cm). of the pons (~ 3cm).

The white matter of the The white matter of the medulla consists of sensory medulla consists of sensory (ascending) and motor (ascending) and motor (descending) tracts. (descending) tracts.


Medulla oblongata (Medulla)Medulla oblongata (Medulla)On the anterior aspect of the medulla, there are On the anterior aspect of the medulla, there are protrusions of the white matter called pyramids. protrusions of the white matter called pyramids.

The pyramids consist of largest motor tracts that The pyramids consist of largest motor tracts that pass from the cerebrum to the spinal cord.pass from the cerebrum to the spinal cord.

Antrior-inferior view


Medulla oblongata (Medulla)Medulla oblongata (Medulla)

Decussation of pyramidsDecussation of pyramids

90% of the axons of the right pyramid cross 90% of the axons of the right pyramid cross to the left side and 90% of axons from left to the left side and 90% of axons from left side cross to the right side just superior to side cross to the right side just superior to the junction of the medulla with the spinal the junction of the medulla with the spinal cord. cord.

This crossing is called decussation of This crossing is called decussation of pyramids. pyramids.


It is well-known that the right side of the brain It is well-known that the right side of the brain controls muscles on the left side of the body and the controls muscles on the left side of the body and the left side of the brain controls muscles on the right left side of the brain controls muscles on the right side of the body. side of the body.

Similarly, sensory information from the left side of Similarly, sensory information from the left side of the body crosses over to the right side of the brain the body crosses over to the right side of the brain and information from the right side of the body and information from the right side of the body crosses over to the left side of the brain. crosses over to the left side of the brain.

Therefore, brain damage to one side of the brain Therefore, brain damage to one side of the brain will affect the opposite side of the body.will affect the opposite side of the body.


Nuclei present in the medullaNuclei present in the medulla

The medulla contains various nuclei that The medulla contains various nuclei that control various vital activities of the body. control various vital activities of the body.

They are the They are the cardiovascular centercardiovascular center (regulates the rate and force of the heart (regulates the rate and force of the heart beat and diameter of blood vessels) and beat and diameter of blood vessels) and medullary rhythamicity areamedullary rhythamicity area (adjusts the (adjusts the basic rhytham of breathing) of the basic rhytham of breathing) of the respiratory center. respiratory center.


Medulla- OLIVEMedulla- OLIVE

Another structure of the Another structure of the medulla is the olive. medulla is the olive.

It is an oval shaped It is an oval shaped swelling that lies lateral swelling that lies lateral to each pyramid. to each pyramid.

The olive contains the The olive contains the inferior olivary nucleus. inferior olivary nucleus.


Medulla- OLIVEMedulla- OLIVE

The inferior olivary nucleus relays impulses The inferior olivary nucleus relays impulses from proprioceptors that monitor joint and from proprioceptors that monitor joint and muscle position to the cerebellum. muscle position to the cerebellum.

Prorioception is the awareness of the precise Prorioception is the awareness of the precise positions of the body part.positions of the body part.


Nuclei present in the medullaNuclei present in the medulla

Other nuclei in the medulla control Other nuclei in the medulla control reflexes for vomiting, reflexes for vomiting, coughing and coughing and sneezing.sneezing.

The major nuclei present in the medulla are the The major nuclei present in the medulla are the gracile (=slender) and cuneate (wedge shaped) nuclei. gracile (=slender) and cuneate (wedge shaped) nuclei.

These nuclei are associated with sensations of touch, These nuclei are associated with sensations of touch, conscious proprioception, pressure and vibration. conscious proprioception, pressure and vibration.


Nuclei present in Nuclei present in the medullathe medulla

NUCLEI OF CRANIAL NUCLEI OF CRANIAL NERVES NERVES

VIII (vestibulocochlear), VIII (vestibulocochlear), IX (glossopharyngeal), IX (glossopharyngeal), X (vagus), X (vagus), XI (accessory), and XI (accessory), and XII (hypoglossal).XII (hypoglossal).


CerebellumCerebellum

The word "cerebellum" comes from the Latin word The word "cerebellum" comes from the Latin word for "little brain". for "little brain".

The cerebellum is located behind the brain stem. The cerebellum is located behind the brain stem.

It has a butterfly like appearance. It has a butterfly like appearance.

Although it is about a tenth of the brain in size, it Although it is about a tenth of the brain in size, it contains nearly half of the neurons in the brain. contains nearly half of the neurons in the brain.



The central constricted area of the cerebellum is The central constricted area of the cerebellum is called vermis (means worm). called vermis (means worm).

The wings like structures are the cerebellar The wings like structures are the cerebellar hemispheres. hemispheres.

The cerebellar hemisphere is divided into anterior The cerebellar hemisphere is divided into anterior and posterior lobes by distinct fissure. and posterior lobes by distinct fissure.

These lobes are concerned with the subconscious These lobes are concerned with the subconscious aspects of skeletal muscle movements.aspects of skeletal muscle movements.



Cerebellar cortex consists of grey matter that Cerebellar cortex consists of grey matter that appears as parallel ridges called folia. appears as parallel ridges called folia.

Deep to folia are tracts called arbour vitae (= Deep to folia are tracts called arbour vitae (= tree of life). tree of life).

Deep within the white matter are nuclei that Deep within the white matter are nuclei that give rise to axons that carry impulses from the give rise to axons that carry impulses from the cerebellum to other brain centers and to the cerebellum to other brain centers and to the spinal cord. spinal cord.



Three paired Three paired cerebellar pedunclescerebellar peduncles attach cerebellum to the brain attach cerebellum to the brain stem. stem.

They are:They are:Inferior cerebellar peduncle :Inferior cerebellar peduncle :Middle cerebellar peduncles:Middle cerebellar peduncles:Superior cerebellar peduncle:Superior cerebellar peduncle:



Cerebellum is the main brain region that Cerebellum is the main brain region that regulate posture and balance. regulate posture and balance.

It is responsible for all skilled muscular It is responsible for all skilled muscular activities. activities.

Cerebellum may also have a role in cognition Cerebellum may also have a role in cognition and language processing.and language processing.


Expansions of the brain’s central cavityFilled with cerebrospinal fluidLined with ependymal cellsContinuous with each other Continuous with the central canal of the spinal cord

Lateral ventricles – located in cerebral hemispheresHorseshoe-shaped from bending of the cerebral hemispheresThird ventricle – lies in diencephalon Connected with lateral ventricles by interventricular foramen Cerebral aqueduct – connects 3rd and 4th ventriclesFourth ventricle – lies in hindbrainConnects to the central canal of the spinal cord

Ventricles of the BrainVentricles of the Brain


The 12 Pairs of Cranial NervesThe 12 Pairs of Cranial Nerves


Cranial Nerves

Number Name Function

I Olfactory Nerve Smell

II Optic Nerve Vision

III Oculomotor Nerve

Eye movement; Pupil dilation

IV Trochlear Nerve Eye movement

V Trigeminal Nerve

Somatosensory information (touch, pain) from the face and head; muscles for chewing.


VI Abducens Nerve Eye Movement

VII Facial Nerve

Taste (anterior 2/3 of tongue); Somatosensory information from ear; Controls muscles used in facial expression.

VIII Vestibulocochlear Nerve

Hearing; Balance

IX Glossopharyngeal Nerve

Taste (posterior 1/3 of tongue); Somatosensory information from tongue, tonsil, pharynx; Controls some muscles used in swallowing.


X Vagus Nerve Sensory, motor and autonomic functions of viscera (glands, digestion, heart rate)

XI Spinal Accessory Nerve

Controls muscles used in head movement.

XII Hypoglossal Nerve

Controls muscles of tongue


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155 Anatomy-CNS-2013-14

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Transcript of 155 Anatomy-CNS-2013-14