The central nervous system presentation dawn part 1

BY,

DAWN V TOMY M.PHARM.,ASST. PROFESSOR,

DEPT. OF PHARMACOLOGY,

ST.JOSEPH’S COLLEGE OF PHARMACY, CHERTHALA.

Wednesday, December 17,

2014ST.JOSEPH’S COLLEGE OF PHARMACY, CHERTHALA.

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INTRODUCTION

• The central nervous system (CNS) consists of the brain and spinal cord.

• The brain is encased in the skull, and protected by the cranium.

• The brainstem connects the brain to the spinal cord. Brain communicate

with the peripheral nervous system (PNS) through the spinal cord.

• The spinal cord starts from the base of the skull, continues

through the foramen magnum, lies caudally to the brain and is protected

by the vertebra and terminates at the first or second lumbar vertebra.

CENTRAL NERVOUS SYSTEM (CNS)

The brain is situated in the cranial cavity formed by the cranial and

facial bones. It is protected by the meninges. It is nourished and

cushioned by the Cerebrospinal Fluid (CSF) formed in ventricles.



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ANATOMY OF THE BRAIN

STRUCTURE OF THE BRAIN.

4Wednesday, December 17,


An adult brain weighs between 1.3 to 1.4 kg and has a volume of about 1200 cc.



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BRAIN

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Major parts of the brain:

•Cerebrum

• Frontal lobes

• Parietal lobes

• Occipital lobes

• Temporal lobes

• Insula

•Diencephalon

•Epithalamus

•Thalamus

•Subthalamus and

•Hypothalamus

•Brainstem

• Medulla oblongata

•Pons

•Midbrain

•Cerebellum



Major Parts of the Brain

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• It helps to maintain homeostasis.

• Interprets sensations.

• Determines perception.

• Stores memory.

• Reasoning.

• Makes decisions.

• Coordinates muscular movements.

• Regulates visceral activities.

• Determines personality.

FUNCTIONS OF THE BRAIN.



Brain Development

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BLOOD FLOW

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Supply: Internal carotid and vertebral arteries.Return: Internal jugular veins (from head to heart)



BLOOD BRAIN BARRIER (BBB)

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The endothelial cells of the braincapillaries along with thick basementmembrane and astrocytes forms tightjunctions which selectively passessubstances from blood to brain.



CSF AND CEREBRAL VENTRICLES

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Ventricles and Cerebrospinal Fluid

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• There are four (4) ventricles• The ventricles are interconnected cavitieswithin cerebral hemispheres and brain stem.• The ventricles are continuous with thecentral canal of the spinal cord.• They are filled with cerebrospinal fluid (CSF).

• The four (4) ventricles are:• Lateral ventricles (2)

• Known as the first and second ventricles

• Third ventricle• Fourth ventricle

• Interventricular foramen.• Cerebral aqueduct.

Lateral ventricle

Third ventricle

Fourth ventricle

(a)

Interventricular

foramen

Cerebral

aqueduct

To central canal

of spinal cord

Third ventricle

(b)

Cerebral

aqueduct

To central canal

of spinal cord

Fourth

ventricle

Lateral

ventricle

Interventricular

foramen



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A lateral ventricle is located in each hemisphere ofthe cerebrum. Anteriorly, the lateral ventricles areseparated by a thin membrane, the septumpellucidum. The 3rd ventricle is a narrow cavity alongthe midline; superior to the hypothalamus andbetween the right and left halves of thalamus. The4th ventricle lies between the brain stem and thecerebellum. The 4th ventricle is continuous with thecentral canal of spinal cord.





Formation of CSF in the ventricles.

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CSF is produced in the choroid plexuses which are network ofcapillaries in the walls of the ventricles.The ependymal cells that cover the capillaries formcerebrospinal fluid from the blood plasma by filtration andsecretion process.The ependymal cells joined by tight junctions in the choroidcapillaries forms the blood-cerebrospinal fluid barrierpermitting selective diffusion, thereby protecting the brainand spinal cord from potentially harmful blood-bornsubstances.



Cerebrospinal Fluid

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•Circulates in ventricles, centralcanal of spinal cord, and thesubarachnoid space.• Completely surrounds the brainand spinal cord.• Excess or wasted CSF is absorbedby the arachnoid villi.• It is a clear fluid similar to bloodplasma.• Volume is only about 120 ml.• Nutritive and protective function.• Helps maintain stable ionconcentrations in the CNS.

Third ventricle

Fourth ventricleCerebral aqueduct

Subarachnoid space

Arachnoid mater

Dura mater

Pia mater

Pia materCentral canal of spinal cord

Subarachnoid space

Filum terminaleArachnoid mater

Dura mater

Arachnoid

granulations

Choroid plexuses

of third ventricle

Blood-filled

dural sinus

Choroid plexus of

fourth ventricle





THE COMPOSITION OF CSF.

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Total volume of CSF is 80 to 150mL in anadult. It contains Glucose, Proteins, Lacticacid, Urea, Cations (Na+, K+, Ca2+ andMg2+) and Anions (Cl- and HCO3

-). It alsocontains WBCs.



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The CSF contributes to brain and spinal cord homeostasis in 3 ways.

1. Mechanical protection: It serves as shock absorbing medium that protects thedelicate tissues of the brain and spinal cord from impacts by not letting them hitthe bony walls of the cranial and vertebral cavities. The fluid also buoys the brainfloating it in the cranial cavity.

2. Chemical protection: Provides an optimal chemical environment for accurateneuronal signalling. Ionic composition to be maintained in homeostasis as evenslight changes in them can affect the production of action potentials andpostsynaptic potentials.

3. Circulation: CSF is a medium for exchange of nutrients and waste productsbetween the blood and nervous tissue.

FUNCTIONS OF CSF



Meninges

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• The meninges• Membranes of CNS• Protect the CNS• Three (3) layers:

• Dura mater• “Tough mother”• Venous sinuses• Falx

• Arachnoid mater• “Spiderweb-like”• Space contains cerebrospinal fluid (CSF)

• Pia mater• “Faithful mother”• Encapsulates blood vessels

Scalp

Cranium

Cerebrum

Cerebellum

Spinal cord

Meninges

Meninges

Cerebrum

(b)(a)

Gray matterWhite matter

Subarachnoid spaceFalx cerebri

Pia mater

Dura mater

Bone of skullSubcutaneous tissueSkin

Tentorium

cerebelli

Vertebra

Dural sinus Arachnoid

granulation

Arachnoid

mater



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Protective covering of the brain:The cranium and the cranial meninges surround and protect the brain.The cranial meninges are continuous with spinal meninges. They are:1. The outer dura mater (The cranial dura mater has 2 layers and

spinal dura mater has only one layer).2. The middle arachnoid mater and3. The inner pia mater.

The space between Dura mater and arachnoid mater is known assubdural space and that between arachnoid mater and pia mater isknows as subarachnoid space which is filled with cerebrospinal fluid(CSF).



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The parts of brain are separated by 3extensions of the dura mater. They are:1. The falx cerebri which separates 2

hemispheres of cerebrum.2. The falx cerebelli which separates 2

hemispheres of cerebellum and3. The tentorium cerebelli which separates

the cerebrum from the cerebellum.Wednesday, December 17,




Meninges of the Spinal Cord

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Spinal cord

Spinal cord

Pia mater

Arachnoid mater

Dura mater

Dorsal root

Dorsal root

Spinal nerve

Epidural space

(a) (b)

Ventral root

Dorsal root

ganglion

Thoracic

vertebra

Spinal

nerve

Dorsal root

ganglion

Subarachnoid space

Dorsal branch

(dorsal ramus)

Ventral branch

(ventral ramus)

Ventral root

Epidural space

Body of vertebra



STRUCTURE OF CEREBRUM.



Structure of the Cerebrum

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• Corpus callosum

• Connects cerebral hemispheres

(a commissure)

• Gyri

• Bumps or convolutions.

• Sulci

• Grooves in gray matter

• Central sulcus.

• Fissures

• Longitudinal: separates the

cerebral hemispheres

• Transverse: separates cerebrum

from cerebellum

• Lateral fissure (sulcus) of

Sylvius.

Central sulcus

Gyrus

Sulcus

Frontal lobeLateral fissure of sylvius

Parietal lobe

Occipital lobe

Central sulcus

Parietal lobe

Occipital lobe

(a)

(b) (c)

Parietal lobe

Central sulcus

Occipital lobeFrontal lobe

Insula

Temporal lobe

Longitudinal

fissure

Transverse

fissure

Cerebellar

hemisphere

Retracted

temporal lobe





Lobes of the Cerebrum

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• Five (5) lobes bilaterally:

• Frontal lobe

• Parietal lobe

• Temporal lobe

• Occipital lobe

• Insula aka ‘Island of

Reil’

(c)

Parietal lobe

Central sulcus

Occipital lobeFrontal lobe

Insula

Retracted temporal lobe





Functions of the Cerebral Lobes

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Functional Regions of the Cerebral Cortex

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Cerebral cortex:

Thin layer of gray matter that constitutes the outermost portion of

cerebrum, contains 75% of all neurons in the nervous system

Frontal eye field

Central sulcus

Parietal lobe

Occipital lobe

Cerebellum

Brainstem

Interpretation of auditory

patterns

Lateral sulcus

Auditory area

Sensory areas involved with

cutaneous and other senses

Sensory speech area

( Wernicke’s area)

Combining visual images,

visual recognition of objects

Visual area

Temporal lobe

Motor speech area

(Broca’s area)

Motor areas involved with the control

of voluntary muscles

Concentration, planning,

problem solving

Front lobe



Motor Areas (pre-central sulcus)

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Frontal eye field

Central sulcus

Parietal lobe

Occipital lobe

Cerebellum

Brainstem

Interpretation of auditory patterns

Lateral sulcus

Auditory area



Sensory speech area



visual recognition of

objects

Visual area

Temporal lobe

Motor speech area (Broca’s area)




problem solving

Front lobe

• Primary motor areas

• Frontal lobes

• Control voluntary muscles

• Broca’s area

• Anterior to primary motor

cortex

• Usually in left hemisphere

• Controls muscles needed

for speech

• Frontal eye field

• Above Broca’s area

• Controls voluntary movements

of eyes and eyelids



Motor Areas

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Parietal lobe

Sensory area

Central sulcus

Motor area

Frontal lobe

Swallowing

ForearmArm Pelvis

Thigh

Leg

Lips

Forearm ArmNeck Pelvis

Thigh

Leg

Genitals

(a) Motor area (b) Sensory area

Longitudinal

fissure

Salivation

Vocalization

Mastication

Facial

expression

Thumb,

fingers,

and hand

Trunk

Foot and

toes

Tongue and

pharynx

Teeth and

gums

Upper

face

Hand, fingers,

and thumb

Trunk

Foot and

toes

Longitudinal

fissure



Sensory Areas (post-central sulcus)

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• Cutaneous sensory area• Parietal lobe

• Interprets sensations on

skin

• Visual area• Occipital lobe

• Interprets vision

• Auditory area• Temporal lobe

• Interprets hearing

• Sensory area for taste

• Near base of the central sulcus

• Sensory area for smell• Arises from centers deep within

the cerebrum

Frontal eye field

Central sulcus

Parietal lobe

Occipital lobe

Cerebellum

Brainstem


Lateral sulcus

Auditory area



Sensory speech area




objects

Visual area

Temporal lobe

Motor speech area

(Broca’s area)




problem solving

Front lobe


2014


Sensory Areas

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Parietal lobe

Sensory area

Central sulcus

Motor area

Frontal lobe

Swallowing

ForearmArm Pelvis

Thigh

Leg

Lips

Forearm ArmNeck Pelvis

Thigh

Leg

Genitals

(a) Motor area (b) Sensory area

Longitudinal

fissure

Salivation

Vocalization

Mastication

Facial

expression

Thumb,

fingers,

and hand

Trunk

Foot and

toes

Tongue and

pharynx

Teeth and

gums

Upper

face

Hand, fingers,

and thumb

Trunk

Foot and

toes

Longitudinal

fissure



Association Areas

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• Regions that are not primary motor or primary sensory areas.

• Widespread throughout the cerebral cortex.

• Analyze and interpret sensory experiences.

• Provide memory, reasoning, verbalization, judgment, emotions…

Frontal eye field

Central sulcus

Parietal lobe

Occipital lobe

Cerebellum

Brainstem


Lateral sulcus

Auditory area



Sensory speech area




objects

Visual area

Temporal lobe

Motor speech area

(Broca’s area)




problem solving

Front lobe



Association Areas

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• Frontal lobe association areas

• Concentrating

• Planning

• Complex problem solving

• Parietal lobe association areas

• Understanding speech

• Choosing words to express

thought

• Temporal lobe association areas

• Interpret complex sensory

experiences

• Store memories of visual scenes,

music, and complex patterns

• Occipital lobe association areas

• Analyze and combine visual

images with other sensory

experiences



Hemisphere Dominance

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• The left hemisphere is dominant in most individuals

• Dominant hemisphere controls:

• Speech

• Writing

• Reading

• Verbal skills

• Analytical skills

• Computational skills

• Nondominant hemisphere controls:

• Nonverbal tasks

• Motor tasks

• Understanding and interpreting

musical and visual patterns

• Provides emotional and intuitive

thought processes



Memory

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• Short term memory

• Working memory

• Closed neuronal circuit

• Circuit is stimulated over and

over

• When impulse flow ceases,

memory does also unless it

enters long-term memory via

memory consolidation

• Long term memory

• Changes structure or

function of neurons

• Enhances synaptic

transmission



FUNCTIONS OF CEREBRUM.

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Functions of the Cerebrum

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• Interpreting impulses• Initiating voluntary movements• Storing information as memory• Retrieving stored information • Reasoning• Seat of intelligence and personality



STRUCTURE OF BASAL NUCLEI



Basal Nuclei /Basal Ganglia

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Basal nuclei are masses of grey

matter deep within the white

matter of cerebral hemisphere with

connections to the cerebral cortex

and thalamus.

The basal nuclei form part of the

extrapyramidal tracts and are

involved in initiating muscle tone

in slow and coordinated activities.

• Caudate nucleus, putamen, and

globus pallidus.

• Produce dopamine.

Thalamus

Hypothalamus

Brainstem

Putamen

Cerebellum

Spinal cord

Longitudinal

fissure

Right cerebral

hemisphereCaudate

nucleus

Globus

pallidus

Basal

nuclei



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Thalamus

Hypothalamus

Brainstem

Putamen

Cerebellum

Spinal cord

Longitudinal

fissure

Right cerebral

hemisphereCaudate

nucleus

Globus

pallidus

Basal

nuclei



Basal ganglia lateral to thalamus is the

lentiform nucleus (lens shaped) divided

into 2 as:

a. Globus pallidus (globus=ball,

pallidus=pale) closer to thalamus.

b. Putamen (putamen=shell) closer

to cerebral cortex.

Caudate nucleus (caud=tail) ‘C’ shaped,

large head, tail arches over the

thalamus.

Caudate nucleus along with putamen

and globus pallidus is known as corpus

striatum.

Subthalamic nuclei interconnect the

globus pallidus in each cerebral

hemisphere.

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Functions:

To help regulate initiation and termination of movements in coordination with cerebral

cortex.

Putamen precedes or anticipates body movement.

Caudate nucleus responsible for eye movement.

Globus pallidus helps to regulate the muscle tone required for specific body movements.

It also controls subconscious contractions of skeletal muscles.

They initiate and coordinate cognitive processes such as attentions, memory, planning, and

may act with the limbic system to regulate emotional behaviours.

It estimates the passage of time.

It is associated with psychiatric disorders like:

o Obsessive compulsive disorder.

o Schizophrenia and

o Chronic anxiety all due to the dysfunction in circuits between basal ganglia and the

limbic system.

STRUCTURE OF DIENCEPHALON



Diencephalon

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• Between cerebral hemispheres and above the brainstem.

• Surrounds the third ventricle.

•Thalamus.

• Epithalamus.

• Hypothalamus.

• Optic tracts.

• Optic chiasm.

• Infundibulum.

• Posterior pituitary.

• Mammillary bodies.

• Pineal gland.Wednesday, December 17,




Diencephalon

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Thalamus:

•It makes up 80% of the diencephalon.

•The thalamus consists of two masses of nerve cells

(nuclei) and fibres, situated within the cerebral

hemispheres just below the corpus callosum, one on each

side of the third ventricle.

•It sends axons to regions of the cerebral cortex.

•Nuclei act as relay stations for incoming sensory

messages.



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Functions:

•Relays all sensory impulses to the cerebral cortex. Sensory input

from the skin, viscera and special sense organs is transmitted to the

thalamus (Receives all sensory impulses except smell).

•Afferent impulses converge on the thalamus. Nuclei organize and

amplify or tone down signals (Gateway for sensory impulses

heading to cerebral cortex).

•Channels impulses to appropriate part of cerebral cortex for

interpretation.

•Helps motor functions by transmitting information from the

cerebellum and basal ganglia to the primary motor area of the

cerebral cortex.

•Also helps in maintaining consciousness.Wednesday, December 17,


Diencephalon

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Hypothalamus:

•It is composed of a number of group of nerve cells.

•It is situated inferior and anterior to the thalamus, immediately

above the pituitary gland (pituitary gland projects inferiorly).

•The hypothalamus is linked to the posterior lobe of the pituitary

gland by nerve fibres and to the anterior lobe by a complex system

of blood vessels.

•Maintains homeostasis by regulating visceral activities.

• Links nervous and endocrine systems (hence some say the

neuroendocrine system.



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Functions:

• Control of the endocrine system (The secretion of hormones from both lobes

of the pituitary gland).

• The control of the autonomic nervous system (mainly visceral control center

of the body).

• The control of emotional responses (e.g. pleasure, fear, rage sexual

behaviour including mating and child rearing), control of behavior.

• Regulation of body temperature.

• Regulation of hunger and thirst sensations.

• Regulation of sleep-wake cycles: Biological clocks or circadian rhythms

(e.g. sleeping and waking cycles) by hormone melatonin from pineal gland.

• Formation of memory.Wednesday, December 17,


Diencephalon

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Epithalamus:

• Forms part of the “roof” of the third ventricle, consists of a

tiny group of nuclei Includes the pineal gland (pineal

body), which secretes the hormone melatonin under

influence of the hypothalamus and the habenular nuclei.

Infundibulum:

• A hollow funnel shaped stalk that connects the

Hypothalamus and the posterior lobe of pituitary.

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The Limbic System (the emotional brain)



1. Limbic lobe – rim of cerebral cortex on the medial surface of each hemisphere.

a. Allows us to shift between thoughts.

b. Interprets pain as unpleasant – cingulate gyrus (cingul=belt) lies above corpus callosum.

Parahippocampal gyrus lies in the temporal lobe below.

2. Dentate gyrus (dentate=tooth head) – lies between hippocampus (seahorse shape) and

parahippocampal gyrus.

3. Amygdala (amygda=almond shaped) stimulation of it produces fear and aggression. It composed of

groups of neurons located close to caudate nucleus.

4. Septal nuclei – lies in the septal area formed by regions under corpus callosum and the paraterminal

gyrus (cerebral gyrus).

5. Mammillary bodies of the hypothalamus – they are the 2 round masses near the cerebral peduncles.

6. Anterior and medial nucleus – it participate in limbic circuits.

7. Olfactory bulbs – flattened bodies of olfactory pathway that rests on the cribriform plate of the ethmoid

bone of the skull.

8. Fornix, striaterminalis, striamedullaris, medial forebrain bundle and mammillothalamic tract are

interconnected by bundles of myelinated axons.

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60



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Functions:

It plays an important role in a range of emotions including pain,

pleasure, docility, affection and anger (helps in experiencing intense

pain or extreme pleasure).

It is also involved in olfactory (smelling) and memory.

Stimulation of limbic system area produces tameness and affection.

Hippocampus functions in memory.



THE STRUCTURE OF BRAIN STEM



Brainstem

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Three parts:

1. Medulla Oblongata

2. Pons

3. Midbrain

Spinal cord

Thalamus

HypothalamusDiencephalon

Pons

Midbrain

Corpus

callosum

Corpora quadrigemina

Cerebral

aqueduct

Reticular

formation

Medulla

oblongata



Medulla Oblongata

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Pyramidal tract

Pons

Optic nerve Optic chiasma

Thalamus

Spinal cord

Pituitary gland

Pineal gland

Optic tractMammillary body

(a) (b)

Olive


Cerebral

peduncles

Superior

colliculus

Inferior

colliculus

Third

ventricle

Fourth

ventricle

Cerebellar

pedunclesMedulla

oblongata

• Enlarged continuation of

spinal cord

• Conducts ascending and

descending impulses between

brain and spinal cord

• Contains cardiac, vasomotor,

and respiratory control

centers.

• Contains various nonvital

reflex control centers

(coughing, sneezing,

swallowing, and vomiting)









Pons

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Pyramidal tract

Pons

Optic nerve Optic chiasma

Thalamus

Spinal cord

Pituitary gland

Pineal gland

Optic tractMammillary body

(a) (b)

Olive


Cerebral

peduncles

Superior

colliculus

Inferior

colliculus

Third

ventricle

Fourth

ventricle

Cerebellar

pedunclesMedulla

oblongata

• Rounded bulge on underside

of brainstem.

• Between medulla oblongata

and midbrain.

• Helps regulate rate and

depth of breathing.

• Relays nerve impulses to and

from medulla oblongata and

cerebellum.



Midbrain

• Between diencephalon and pons

• Contains bundles of fibers that join lower parts of brainstem and spinal cord with

higher part of brain

• Cerebral aqueduct

• Cerebral peduncles (bundles of nerve fibers)

• Corpora quadrigemina (centers for visual and auditory reflexes)









Reticular Formation

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•The reticular formation is a

collection of neurones in the core

of the brain stem (runs through

the central core of the medulla,

pons and midbrain), surrounded

by neurons which conduct

ascending and descending nerve

impulses between the brain and

the spinal cord. It has widespread

connections ideal for arousal of

the brain as a whole

•Filters incoming sensory

information.

• Arouses cerebral cortex into

state of wakefulness.

Spinal cord

Thalamus

HypothalamusDiencephalon

Pons

Midbrain

Corpus

callosum

Corpora

quadrigemina

Cerebral

aqueduct

Reticular formation

Medulla

oblongata



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Functions:

The reticular formation is involved in:

Coordination of skeletal muscle activity associated with voluntary

motor movement and the maintenance of balance.

Coordination of activity controlled by the autonomic nervous system,

e.g. cardiovascular, respiratory and gastrointestinal activity.

Selective awareness that functions through the reticular activating

system (RAS) which selectively blocks or passes sensory information

to the cerebral cortex (Maintains consciousness, alertness and also

functions in sleep and arousal from sleep).

Types of Sleep

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• Slow wave

• Non-REM sleep

• Person is tired

• Decreasing activity of

reticular system

• Restful

• Dreamless

• Reduced blood pressure and

respiratory rate

• Ranges from light to heavy

• Alternates with REM sleep

• Rapid Eye Movement (REM)

• Paradoxical sleep

• Some areas of brain active

• Heart and respiratory rates irregular

• Dreaming occurs



STRUCTURE OF CEREBELLUM



Cerebellum

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• Situated inferior to occipital

lobes, posterior to pons and

medulla oblongata

• Has two hemispheres.

• Vermis connects hemispheres.

• Cerebellar cortex (gray matter).

• Arbor vitae tree of life (white

matter).

• Cerebellar peduncles (nerve fiber

tracts).

• Dentate nucleus (largest nucleus

in cerebellum).

Thalamus

Superior

peduncle

Middle peduncle

Inferior peduncle

Pons

Medulla oblongata

Cerebellum

Corpus callosum

Longitudinal

fissure





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Functions:

•Integrates sensory information concerning

position of body parts.

•Smoothens and coordinates contractions

of skeletal muscles.

•Regulates posture and balance.

•Cognition and language processing.Wednesday, December 17,



2014

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Health & Medicine

The central nervous system presentation dawn part 1