8.2. encephalon

7/24/2019 8.2. Encephalon

1/86


2/86

8.3.1 Functions

8.3.2 Parts of the encephalon

8.3.3 Protecting coverings of the encephalon

8.3.4 Blood supply to the encephalon

8.3.5 Blood-brain barrier (BBB)

8.3.6 Cerebrospinal fluid (CSF)

8.3.7 Brain stem

8.3.8 Diencephalon

8.3.9 Cerebellum: structure and function

8.3.10 Cerebrum

8.3 THE ENCEPHALON


3/86

Register of sensations

Interrelations

Decision making

Execution of commands

Intelligence, emotions, behaviour and memory

8.3.1 FUNCTIONS OF THE ENCEPHALON


4/86

Brain stem:- Medulla oblongata

- Pons

- Midbrain

Diencephalon:- Thalamus

- Hypothalamus

- Epithalamus (pineal gland or body)

Cerebrum

Cerebellum

ADULT STRUCTURES OF THE ENCEPHALON


5/86

MAJOR PARTS OF THE ENCEPHALON

Cerebrum

Cerebellum

Diencephalon

Brain stem


6/86

The encephalon is protected by:

The skull

The meninges (cerebrospinal f luid, CSF)

Blood brain barrier (BBB)

8.3.3 PROTECTING COVERINGS OF THE

ENCEPHALON


7/86

Continuous with spinal meninges. Same layers: dura mater, arachnoid mater

and pia mater

Differences:

-Dura mater has 2 layers: periosteal(external) and meningeal

(internal) layer

-No epidural space around brain. Blood vessels pass along surface of

brain, penetrating it sheathed by layer of pia mater

MENINGES


8/86

Three extensions of the dura mater divide the brain in different parts:

The falx cerebri :divides the cerebrum in two hemispheres (left and right)

The falx cerebelli: separates the two hemispheres of the cerebellum (left and right)

The tentorium cerebelli: separates the cerebrum from the cerebellum

MENINGES


9/86

Encephalon is 2% of body weight

The brain requires 20% of oxygen

Noble or preferent organ

Cell nutrit ion: glucose

BLOOD SUPPLY TO BRAIN

The nervous tissue requires oxygen at high rates. Blood is

the only substrate of glucose. 15% of blood is pumped to

the encephalon for adequate supply of oxygen and glucose


10/86

Formed by endothelial cellsthat cover the nerve capillaries and

astrocytes (barrier/modify permeability)

Nerve capillaries are nearly impermeable:

Strong junct ions between endothelial cells andbetween

endothelial cells andastrocytes: GAP junctions, Adherens

junctions, Tight junctions (predominant)

High permeability: lipid-soluble substances

Low permeability: hydrosoluble susbtance

BLOOD-BRAIN BARRIER

Neurons must be protected from dangerous substances

that may be in blood. That is the reason why nerve capillarieshave low permeability and form the blood-brain barrier


11/86

Oxygen

Nutrients

(mainly glucose)

Capillary lumenEndothelial cells

Astrocyte

Interstitial fluidWaste products

Carbon dioxide

Tight junction

BLOOD-BRAIN BARRIER


12/86

BLOOD-BRAIN BARRIER


13/86

CEREBROSPINAL FLUID (CSF):

INTRODUCTION

It is synthesized by ependymal cells that cover the choroid

plexuses of the ventricles (cavities of the encephalon).

Function: physical and chemical protection of the encephalon

and spinal cord.

Continuous circulation:- Subarachnoid space (between arachnoid mater and pia mater)

- Cavities: ventricles

. - Central canal of the spinal cord


14/86

Lateral ventricles

Third ventricle

Fourth ventricle

There are four ventricles:

- First and second ventricles: lateral ventricles

- Third ventricle: superior to the hypothalamus

- Fourth ventricle: between brain stem and cerebellum

CEREBROSPINAL FLUID (CSF) AND

VENTRICULAR SYSTEM


15/86

Interventricular foramen (Monros aqueduct) communicates

the lateral ventricle with the thrid ventricle

Cerebral or Silvios aqueduct communicates third and fourth

ventricles

VENTRICULAR SYSTEM


16/86

VENTRICULAR SYSTEM


17/86

- Choroid plexuses: networks ofblood capillaries in walls of

ventricles covered by ependymal

cells that filter plasma to

synthesize CSF

- Tight junctions between

ependymal cells forming blood-

cerebrospinal fluid barrier

CSF: SYNTHESIS


18/86


19/86

CSF: SYNTHESIS AND CIRCULATION


20/86

BRAIN STEM


21/86

Brain stem:

- Midbrain- Pons

- Medulla oblongata

Diencephalon:

- Thalamus- Hypothalamus

- Epithalamus (pineal gland)

Cerebellum

Cerebrum:

- Cortex (gray matter)

- Internal region (white matter) and nuclei (gray matter) within

PARTS OF THE BRAIN


22/86

It is the most primitive region of the encephalon. Located between

spinal cord and the diencephalon

Pons

Midbrain

Medulla

oblongata

Thalamus (diencephalon)

Spinal cord

Lateral view

Cranial nerves

BRAIN STEM


23/86

Inferior part of the brainstem

Above foramenmagnum

Below the pons

Gray matter / Whitemater

MEDULLA OBLONGATA


24/86

Ascendent fascicles (sensory)From the posterior column tracts

Descendent fascicles (motor)From the corticospinal tracts

White matter

MEDULLA OBLONGATA


25/86

Nuclei

Cardiovascular center

Respiratory center Reflex center (swallowing, vomit,

sneeze, hiccups)

Gray matter

MEDULLA OBLONGATA


26/86

Anterior or ventral:

Pyramids

Posterior or dorsal:

Gracile and cuneate

nuclei

Lateral:

Olives

MEDULLA OBLONGATA


27/86

Pons

Midbrain

Medulla oblongata

Thalamus

(diencephalon)

Spinal cord

Lateral view

Cranial nerves

Superior to the medulla oblongata and anterior to the cerebellum Gray (nuclei) / White matter (tracts)

Connects: spinal cord with encephalon

Some axons connect left and right sides of cerebellum. Others are

part of ascending or descending tracts

PONS


28/86

- It receives nerve impulses:

Transmits nerve impulses that control the

movement of skeletal muscles from the cortex to

the cerebellum

- Respiration control:

- Pneumotaxic area

- Apneustic area

PONS: FUNCTIONS


29/86

Extends from pons to inferior portion of diencephalon

Cerebral aqueduct:Connects third and fourth ventricles

Anterior or ventral portion

Posterior or dorsal portion

MIDBRAIN OR MESENCEPHALON
http://www.google.es/url?sa=i&rct=j&q=&esrc=s&frm=1&source=images&cd=&cad=rja&uact=8&ved=0CAcQjRw&url=http%3A%2F%2Fpixshark.com%2Faqueduct-of-midbrain-model.htm&ei=ZhfKVJSMOITmUti0gPAD&bvm=bv.84607526,d.d24&psig=AFQjCNH0i2uryKax7ZSLrZmIN5YAUPCTHg&ust=1422616560601835


30/86

Cerebral peduncles: paired bundles of axons

corticobulbar, corticospinal and corticopontine tracts

- Motor f ibers (axons)

- Corticospinal tract

- Corticobulbar tract

- Corticopontine tract

- Sensit ive fibers

to thalamus

ANTERIOR OR VENTRAL PORTION

MIDBRAIN


31/86

Also called tectum or

quadrigeminal lamina

- Quadrigeminal

tubercles (colliculi):

Superior

Inferior

POSTERIOR OR DORSAL PORTION

MIDBRAIN


32/86

-Superior collicul i:

- Reflex centers for movements (eyes, head,

neck) in response to visual stimuli and others.

-Inferior collicul i:

- Reflex centers for movements of the head and

trunk in response to hearing stimuli

MIDBRAIN: QUADRIGEMINAL TUBERCLES

MIDBRAIN


33/86

Substantia nigra (melanin): dopaminergic neurons control

subconcious muscular activity

Red nuclei:synapses with axons from cerebellum and cortex.

Control of muscular movement

MIDBRAIN


34/86

Ocular movements

Visual and auditoryreflexes

Coordination of breathing

Connectioncerebellum/cerebrum

Control of involuntary movements

(swallowing)

Center of cardiac control and vasomotor

Respiratory center

Vomiting center

MIDBRAIN

PONS

MEDULLAOBLONGATA

FUNCTIONS OF THE BRAIN STEM


35/86

DIENCEPHALON


36/86

Brain stem:

- Midbrain

- Pons

- Medulla oblongata

Cerebellum

Diencephalon:

- Thalamus

- Hypothalamus


Cerebrum:

- Cortex.

- Cerebral hemispheres

PARTS OF THE BRAIN


37/86

It is located between the brain stem and the cerebrum

THE DIENCEPHALON: LOCATION


38/86

- Paired oval-shaped masses of gray matter.

- Compossed of 80 nuclei with interspersed tracts of white

matter

THALAMUS


39/86

- Modulates sensory information that reaches the cerebral

cortex from the spinal cord and brain stem.

- Knowledge acquisition and maintenance of consciousness.

- Conscious pain, temperature control, thin touch andpressure (spinothalamic tracts).

- Contributes to motor functions by passing info from

cerebellum and basal nuclei to primary motor area of cerebral

cortex.

THALAMUS: FUNCTIONS


40/86

-Inferior to the thalamus and superior to the pituitary gland-Control of many conditions (homeostasis)

HYPOTHALAMUS


41/86

Functions: HOMEOSTASIS

1. Control of the Autonomic Nevous System (ANS)

2. Control of the hypophysis (pituitary gland): produces

oxytocin and antidiuretic hormone (vasopressin)

3. Regulation of emotional and behavioural patterns

4. Regulation of hunger and thirst

5. Control of body temperature

6. Regulation of circadian rhythms and consciousness

HYPOTHALAMUS


42/86

- Posterior and superior to thethalamus

- Contains:

- Pineal gland or epiphysis:Secrets melatonin (adjustment of

biological clock)

- Habenular nuclei:

Olfaction (emotional responses

to odors)

EPITHALAMUS


43/86

CEREBELLUM


44/86

Brain stem:

- Midbrain- Pons

- Medulla oblongata

Cerebellum

Diencephalon:

- Thalamus

- Hypothalamus

- Epithalamus (pineal gland) Cerebrum:

- Cortex (gray matter)

- Internal region (white matter) and nuclei (gray matter) within

PARTS OF THE BRAIN

anteriorTHE CEREBELLUM


45/86

It is the second biggest structure of the encephalon. In contains

gray matter (exterior) and white matter (interior)

cerebellum

Lateral view Ventral view

anterior

posteriorCerebellum

Dorsal view

2 hemispheres

vermisfolia

THE CEREBELLUM

THE CEREBELLUM STRUCTURE


46/86

- Cerebellar cortex and folia (gray matter)

- Cerebellar nuclei (gray matter)

- Arbor vitae (white matter)

- Cerebellar peduncles:Attach cerebellum to brain stem; here thespinocerebellar tracts arrive.

THE CEREBELLUM: STRUCTURE

THE CEREBELLUM STRUCTURE


47/86

- Separated from cerebrum by tentorium cerebelli

- Two cerebellar hemispheres separated by the falx cerebelli

THE CEREBELLUM: STRUCTURE

THE CEREBELLUM


48/86

Anterior lobe Anterior lobe

Flocculonodular lobe

The posterior and anterior lobe control subconscious aspects

of skeletal muscle movements

The flocculonodular lobe contributes to balance and

equilibrium

Posterior lobe Posterior lobe

THE CEREBELLUM

THE CEREBELLUM FUNCTIONS


49/86

Receives sensory information from: muscles, tendons, joints,

balance receptors, visual receptors

Regulates posture and balance, through the spinocerebellar

tracts and the vestibular nerve information

Compares voluntary movements designed by the cerebral

cortex with what is going to occur (coordinates thin and

complex movements)

Coordinates and smoothes complex sequences of skeletal

muscle contractions Fundamental for the motor activities that constitute an ability

CEREBELLUM damage: ataxia (reduction in the ability to

coordinate movements)

THE CEREBELLUM: FUNCTIONS


50/86

CEREBRUM

PARTS OF THE BRAIN


51/86

Brain stem:

- Midbrain- Pons

- Medulla oblongata

Diencephalon:

- Thalamus- Hypothalamus


Cerebellum

Cerebrum:

- Cortex and nuclei (gray matter)

- Tracts (white matter)

PARTS OF THE BRAIN

CEREBRUM: FUNCTIONS


52/86

CEREBRUM: FUNCTIONS

THANKS TO THE CEREBRUM WE ARE ABLE TO

TALK

READ

WRITEMAKE CALCULATIONS

REMEMBER THE PAST, PLAN FOR THE FUTURE

CREATE

CEREBRUM: STRUCTURE


53/86

Biggest part of the encephalon

External Gray matter Cerebral cortexInternal White matter and nuclei of gray matter (basal nuclei)

White matter

Gray matter

CEREBRUM: STRUCTURE

CEREBRUM: STRUCTURE OF CORTEX


54/86

-Convolutions or gyri:folds

-Fissures:deep grooves

-Sulci:shallower grooves

CEREBRUM: STRUCTURE OF CORTEX

CEREBRUM: STRUCTURE


55/86

Cerebral hemispheres and longitudinal fissure

Longitudinal

fissure

The falx cerebri is located within the longitudinal fissure

CEREBRUM: STRUCTURE

CEREBRUM: STRUCTURE


56/86

The two hemispheres are connected by the corpus callosum

The corpus callosum is a broad band of white matter

C U S UC U

THE CEREBRUM


57/86

Formed by two hemispheres bound by the corpus callosum.

Each hemisphere is divided in four lobes, termed after the corresponding

bone of the skull: frontal,parietal, occipital and temporal lobes

Temporal lobe

Frontal lobe

Occipital lobe

Parietal lobe

THE CEREBRUM

CEREBRUM: STRUCTURE


58/86

Central sulcus

Lateral cerebral sulcus

(fissure)

Cerebral lobes and sulcus

Parieto-Occipital

sulcus

CEREBRUM: STRUCTURE

CEREBRUM: STRUCTURE


59/86

CEREBRUM: STRUCTURE

CEREBRUM: PRIMARY AREAS


60/86

Precentral

gyrus Postcentral

gyrus

CEREBRUM: PRIMARY AREAS

CEREBRUM: FUNCTIONAL AREAS OF THE CEREBRAL CORTEX


61/86

Sensory areas:Receive and process signals orsensory impulses

Motor areas:start voluntary movements

Association areas:perform more complex

integrative functions (memory, emotions,

reasoning, will, judgement, personality traits,

and intelligence)




62/86

SENSORY AREAS

Receive sensory signals

Posterior half of the cerebral

hemispheres

Posterior to the central sulcus

MOTOR AREAS Exit of motor orders

Mainly in the anterior part of

each hemisphere

ASSOCIATION AREAS

Motor and sensory areas

Large areas in the lobe surfaces:

parietal, occipital, temporal and

frontal


SENSORY AREAS


63/86

Primary somatosensoryarea

-Posterior to the central sulcus, in the

parietal lobe

-Receives signals for touch, pain, tickle,proprioception, itch, vibration, pressure,

temperature

Primary auditory area-Temporal lobe

-Receives information for sound

Primary gustatory area-Postcentral gyrus superior to the lateral

sulcus in the parietal cortex

-Receives impulses for taste

Primary olfactory area-Medial aspect of the temporal lobe

-Receives impulses for smell. Olfactory

perception

Primary visual area-Posterior tip of occipital lobe

-Receives visual information. Visual

perception

SENSORY AREAS

SENSORY AREAS


64/86

SENSORY AREAS

MOTOR AREAS


65/86

Primary motor area

-Precentral gyrus of the frontal

lobe

-Controls contractions of skeletal

muscles at the opposite side of the

body

Brocas speech area

-Frontal lobe, close to the lateral

cerebral sulcus

-It is located in left hemisphere in

97% of population

-Sends nerve impulses topremotor regions to coordinate

contraction of muscles involved in

speech and breathing

MOTOR AREAS

MOTOR AREAS


66/86

MOTOR AREAS

ASSOCIATION AREAS


67/86

Somatosensoryassociation area

-Posterior to the primary

somatosensory area

-Integrates and interprete somatic

sensations (shape, texture)

Visual association area -Occipital lobe-Relates present and past visual

experiences

Auditory associationarea

-Inferior to the primary auditive area in

the temporal cortex-Allows recognition of particular

sounds

Wernikes area -Temporal and parietal lobe-Interpretes meaning of speech

Common integrative area -Receives and interpretes impulsesfrom other areas. Formation of

thoughts

Premotor area -Anterior to the primary motor area-Controls contraction of muscles with a

complex and sequential nature

ASSOCIATION AREAS


68/86

CEREBRUM: HEMISPHERIC LATERALIZATION


69/86

Left hemisphere Right hemisphere

SENSORY AND MOTOR PATHWAYS OF THE SOMATIC SYSTEM


70/86

Ascendent (SENSORY) pathways: from the body surfaceto the primary somatosensory area

1) Posterior column medial lemniscus pathway

2) Spinothalamic (anterolateral) pathway

Descendent(MOTOR) pathways: origin in the primary

motor area and brain stem:

Direct Indirect

SENSORY PATHWAYS


71/86

SENSORY PATHWAYS


72/86

1storder:

From somatosensory

receptorto spinal cord or brain

stem

2ndorder:

From spinal cord or

brain stem to thalamus

3rdorder:

From thalamus to

primary somatosensoryarea of the cerebrum

Somatic PNS;

Afferent neurons

CNS;

ThalamusCNS;

Cerebral cortex

ASCENDING OR SENSORY PATHWAYS


73/86

Posterior column medial lemniscus pathway

Spinothalamic tract (anterolateral pathway)

POSTERIOR COLUMN PATHWAY: MEDIAL LEMNISCUS


74/86

Posterior column

Segunda Neurona

THEY CROSS IN THEMEDULLA OBLONGATA

Second order neuron

First order neuron

POSTERIOR COLUMN PATHWAY: MEDIAL LEMNISCUS


75/86

Third order neuron:From the thalamus until the somatosensory area of the

cerebral cortexde la corteza.

Sensations: Proprioception, vibration, thin touch, stereognosis


76/86

SPINOTHALAMIC (ANTEROLATERAL) PATHWAY


77/86

Lateral

Anterior

Pain and temperature

Crude touch, pressure

tickle

Contains 2 bundles or tracts:

Spinal cord


78/86

First orderneuron

Axons cross in the

spinal cord and ascend

Second orderneuron

Third order

neuron

MOTOR PATHWAYS


79/86

Somatic motor pathways(descending):

- Direct or pyramidal Start in the cerebral cortex.

Anterior and lateral corticospinal

Corticobulbar (voluntary movements)

-Indirect or extrapyramidal Start in other areas

such as the brain stem

Rubrospinal, Vestibulospinal, Reticulospinal (2)

(muscle tone, balance)

MOTOR PATHWAYS


80/86

Superior somatic neuron (upper motor neuron, UMN):- Contact neurons with the lower motor neurons through the

somatic motor pathways

Inferior motorneuron (lower motor neuron, LMN):- End of the motor pathways

- Body of somas in spinal cord (innervate limbs andtrunk) or brain stem (innervate face and head). Axons reachskeletal muscles

- Only neurons that go from the CNS to the skeletalmuscles

MOTOR PATHWAYS


81/86

Superior somatic

neurons

Inferior motor neurons

CNS;

Brain stem orspinal cord

PNS;

Skeletal muscle

CNS;

Cortex (direct)Brain stem

(indirect)

Interneurons


82/86

MOTOR PATHWAYS

Axons cross at the level of

the pyramids in the medulla

oblongata

Upper Motor Neuron

Lower Motor Neuron

Lateral cort icospinal

pathways


83/86

MOTOR PATHWAYS

Axons cross in

the spinal cord

Anterior

corticospinalpathways

Upper Motor Neuron

Lower Motor Neuron

CORTICOBULBAR PATHWAY


84/86

Some fibers

decussate andothers dont, ending

in the nuclei of the

cranial pairs.

DIRECT SOMATIC MOTOR PATHWAYS


85/86

Lateral Corticoespinaltract

-Axons decussate in pyramids-Control distal skeletal muscles of limbs

-Skilled movements of hands and feet

Anterior Corticoespinaltract

-Axons do not decussate in the pyramids

-Axons decussate in the spinal cord(cervical or lumbar segments)

-Movements of neck and trunk (axial

skeleton) and proximal limbs

Corticobulbar tract -From cortex to brain medulla oblongata-Exit through 9 cranial pairs of the brainstem (from III to XII)

-Voluntary movement of eyes, tongue

and neck

TEXT BOOKS


86/86

TORTORA JW. "Principles of Anatomy and Physiology". 13th ed. Willey

Eds., 2011

SILVERTORN. "Human Physiology: An Integrated Approach. 5th Edition.

Panamericana eds, 2009

8.2. encephalon

Documents