CNS PART 2.pptx

SANTHI KRUPA DASARI
ASSISTANT PROFESSOR
KRISHNA UNIVERSITY COLLEGE OF PHARMACEUTICAL SCIENCES AND
RESEARCH

 The ventricles are structures that
produce cerebrospinal fluid, and transport it around
the cranial cavity. They are lined by ependymal
cells, which form a structure called the choroid
plexus. It is within the choroid plexus that CSF is
produced.
 Embryologically, the ventricular system is derived
from the lumen of the neural tube.
 In total, there are four ventricles; right and left
lateral ventricles, third ventricle and fourth
ventricle.
 Lateral Ventricles
 The left and right lateral ventricles are located
within their respective hemispheres of the cerebrum.
They have ‘horns’ which project into the frontal,
occipital and temporal lobes. The volume of the
lateral ventricles increases with age.

 Third Ventricle
 The lateral ventricles are connected to the third
ventricle by the foramen of Monro. The third
ventricle is situated in between the right and the left
thalamus. The anterior surface of the ventricle
contains two protrusions:
 Supra-optic recess – located above the optic chiasm.
 Infundibular recess – located above the optic stalk.
 Fourth Ventricle
 The fourth ventricle is the last in the system – it
receives CSF from the third ventricle via the cerebral
aqueduct. It lies within the brainstem, at the
junction between the pons and medulla oblongata.
 From the 4th ventricle, the fluid drains into two
places:
 Central spinal canal – bathes the spinal cord
 Subarachnoid cisterns – bathes the brain, between
arachnoid mater and pia mater. Here the CSF is
reabsorbed back into the circulation.

 Production and Reabsorption of Cerebrospinal
Fluid
 Cerebrospinal fluid is produced by the choroid
plexus, located in the lining of the ventricles.
 It consists of capillaries and loose connective
tissue, surrounded by cuboidal epithelial cells.
 Plasma is filtered from the blood by the
epithelial cells to produce CSF.
 In this way, the exact chemical composition of
the fluid can be controlled.
 Drainage of the CSF occurs in the subarachnoid
cisterns (or space). Small projections of
arachnoid mater (arachnoid granulations)
protrude into the dura mater. They allow the
fluid to drain into the dural venous sinuses.

 Cerebrospinal fluid (CSF) is the clear,
colorless and transparent fluid that
circulates through ventricles of brain,
subarachnoid space and central canal of
spinal cord. It is a part of extracellular fluid
(ECF). „
 PROPERTIES AND COMPOSITION OF
CEREBROSPINAL FLUID
 Properties Volume : 150 mL (100 mL to 200
mL)
 Rate of formation : 0.3 mL per minute
Specific gravity : 1.005 Reaction : Alkaline

 it contains more amount of sodium than
potassium. CSF also contains some
lymphocytes. CSF secreted by ventricle does
not contain any cell. Lymphocytes are added
when CSF flows in the spinal cord. „
 FORMATION OF CEREBROSPINAL FLUID
 „
SITE OF FORMATION CSF is formed by
choroid plexuses, situated within the
ventricles. Choroid plexuses are tuft of
capillary projections present inside the
ventricles and are covered by pia mater and
ependymal covering. A large amount of CSF is
formed in the lateral ventricles. „

 MECHANISM OF FORMATION
 CSF is formed by the process of secretion that involves
active transport mechanism.
 FUNCTIONS OF CEREBROSPINAL FLUID
 1. Protective Function CSF acts as fluid buffer and protects
the brain from shock. Since, the specific gravity of brain
and CSF is more or less same, brain floats in CSF. When
head receives a blow, CSF acts like a cushion and prevents
the movement of brain against the skull bone and thereby,
prevents the damage of brain. However, if the head
receives a severe blow, the brain moves forcefully and hits
against the skull bone, leading to the damage of brain
tissues. Brain strikes against the skull bone at a point
opposite to the point where the blow was applied. So, this
type of damage to the brain is known as countercoup
injury.


2. Regulation of Cranial Content Volume
Regulation of cranial content volume is
essential because, brain may be affected if
the volume of cranial content increases. It
happens in cerebral hemorrhage and brain
tumors. Increase in cranial content volume is
prevented by greater absorption of CSF
3. Medium of Exchange
 CSF is the medium through which many
substances, particularly nutritive substances and
waste materials are exchanged between blood
and brain tissues

 Hydrocephalus is defined as an abnormal
collection of cerebrospinal fluid within the
ventricles of the brain. It is a serious
condition, with chronic hydrocephalus
causing raised intracranial pressure, and
consequently cerebral atrophy.

 Blood-brain barrier (BBB) is a
neuroprotective structure that prevents the
entry of many substances and pathogens into
the brain tissues from blood.
 „
STRUCTURE OF BLOOD-BRAIN BARRIER
 Tight junctions in the endothelial cells of
brain capillaries are responsible for BBB
mechanism.

 „
FUNCTIONS OF BLOOD-BRAIN BARRIER
 BBB By preventing injurious materials and
organisms, BBB provides healthy environment
for the nerve cells of brain.
 Substances which can Pass through Blood-
Brain Barrier 1. Oxygen 2. Carbon dioxide 3.
Water 4. Glucose 5. Amino acids 6.
Electrolytes 7. Drugs such as L-dopa, 5-
hydroxytryptamine sulfona mides,
tetracycline and many lipid-soluble drugs 8.
Lipid-soluble anesthetic gases such as ether
and nitrous oxide 9. Other lipid-soluble
substances.

 Substances which cannot Pass through
Blood-Brain Barrier
 1. Injurious chemical agents 2. Pathogens
such as bacteria 3. Drugs such as Penicillin
and the catecholamines.
 Dopamine also cannot pass through BBB. So,
parkinsonism is treated with L-dopa, instead
of dopamine.

 The brain constitutes about one-fiftieth of
the body weight and lies within the cranial
cavity. The parts are
 Cerebrum
 Midbrain
 Pons
 Medulla Oblongata
 Cerebellum

CEREBRUM
 This is the largest part of the brain and it
occupies the anterior and middle cranial fossa.
 It is divided by a deep cleft, the longitudinal
cerebral fissure, into right and left cerebral
hemispheres, each containing one of the lateral
ventricles. Deep within the brain the
hemispheres are connected by a mass of white
matter (nerve fibres) called the corpus
callosum. The falx cerebri is formed by the dura
mater.
 It separates the two hemispheres and
penetrates to the depth of the corpus callosum.

 The superficial (peripheral) part of the
cerebrum is composed of nerve cell bodies or
grey matter, forming the cerebral cortex,
and the deeper layers consist of nerve fibres
or white matter.
 The cerebral cortex shows many infoldings or
furrows of varying depth. The exposed areas
of the folds are the gyri or convolutions and
these are separated by sulci or fissures.

 each hemisphere of the cerebrum is divided
into lobes which take the names of the bones
of the cranium under which they lie:
 • frontal • parietal • temporal • occipital.
 The boundaries of the lobes are marked by
deep sulci (fissures). These are the central,
lateral and parieto-occipital sulci. Interior of
the cerebrum

 Cerebral cortex is also called pallidum and it
consists of two hemispheres. Surface area of
cerebral cortex in human beings is 2.2 sq m.
Both the cerebral hemispheres are separated
by a deep vertical fissure (deep furrow or
groove). The separation is complete
anteriorly and posteriorly. But in middle
portion, the fissure extends only up to corpus
callosum.
 Corpus callosum is the broad band of
commissural fibers, connecting the two
hemispheres. Surface of the cerebral cortex
is characterized by complicated pattern of
sulci (singular = sulcus) and Cerebral Cortex
 „

PARTS OF CEREBRAL CORTEX
 Cerebral cortex is divided into two parts
based on phylogeny (evolutionary
development of a species): 1. Neocortex 2.
Allocortex. 1. Neocortex Neocortex is the
phylogenetically new structure of cerebral
cortex. It is also called isocortex or
neopallium. gyri (singular = gyrus). Sulcus is
a slight depression or groove and gyrus is a
raised ridge.

Functions of the cerebrum
 There are three main varieties of activity
associated with the cerebral cortex:
 • mental activities involved in memory,
intelligence, sense of responsibility, thinking,
reasoning, moral sense and learning are
attributed to the higher centres
 • sensory perception, including the
perception of pain, temperature, touch,
sight, hearing, taste and smell
 • initiation and control of skeletal
(voluntary) muscle contraction.

Basal nuclei
 These are areas of grey matter, lying deep
within the cerebral hemispheres, with
connections to the cerebral cortex and
thalamus.
 The basal nuclei form part of the
extrapyramidal tracts and are thought to be
involved in initiating muscle tone in slow and
coordinated activities. If control is
inadequate or absent, movements are jerky,
clumsy and uncoordinated.

 Basal ganglia are the scattered masses of
gray matter submerged in subcortical
substance of cerebral hemisphere .
 Basal ganglia form the part of extra
pyramidal system, which is concerned with
motor activities
 . „
COMPONENTS OF BASAL GANGLIA Basal
ganglia include three primary components:
 1. Corpus striatum 2. Substantia nigra
 3. Subthalamic nucleus of Luys

 FUNCTIONS OF BASAL GANGLIA
1. CONTROL OF MUSCLE TONE
2. CONTROL OF MOTOR ACTIVITY
3. CONTROL OF REFLEX MUSCULAR ACTIVITY
4. ROLE IN AROUSAL MECHANISM
APPLIED PHYSIOLOGY – DISORDERS OF BASAL
GANGLIA
Parkinson disease occurs due to lack of
dopamine caused by damage of basal
ganglia. It is mostly due to the destruction
of substantia nigra and the nigrostriatal
pathway, which has dopaminergic fibers.

Thalamus.
 The thalamus consists of two masses of nerve
cells and fibres situated within the cerebral
hemispheres just below the corpus callosum,
one on each side of the third ventricle.
Sensory input from the skin, viscera and
special sense organs is transmitted to the
thalamus before redistribution to the
cerebrum.

FUNCTIONS OF THALAMUS
 Thalamus is primarily concerned with somatic
functions and it plays little role in the visceral
functions. Following are the various functions of
thalamus: „
1. RELAY CENTER
 „
2. CENTER FOR PROCESSING OF SENSORY
INFORMATION
 3. CENTER FOR DETERMINING QUALITY OF
SENSATIONS
 „
4. CENTER FOR SEXUAL SENSATIONS Thalamus forms
the center for perception of sexual sensations.
 „
5. ROLE IN AROUSAL AND ALERTNESS REACTIONS
Because of its connections with nuclei of reticular
formation, thalamus plays an important role in
arousal and alertness reactions. „
 6. CENTER FOR REFLEX ACTIVITY Since the sensory
fibers relay here, thalamus forms the center for many
reflex ac

 The hypothalamus is composed of a number
of groups of nerve cells. It is situated below
and in front of the thalamus, immediately
above the pituitary gland.
 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.
 Through these connections, the
hypothalamus controls the output of
hormones from both lobes of the gland.

 Brainstem is the part of brain formed by medulla
oblongata, pons and midbrain. Brainstem
contains ascending and descending tracts
between brain and spinal cord. It also contains
many centers for regulation of vital functions in
the body. „
 MEDULLA OBLONGATA
 Medulla oblongata or medulla is the lowermost
part of brain. It is situated below pons and is
continued downwards as spinal cord. Medulla
forms the main pathway for ascending and
descending tracts of the spinal cord.

 PONS
 The pons is the largest part of the brainstem,
located above the medulla and below
the midbrain.
 It is a group of nerves that function as a
connection between
the cerebrum and cerebellum (pons is Latin for
bridge).
 The pons develops from
the embryonic metencephalon (part of the
hindbrain, developed from the
rhombencephalon), alongside the cerebellum.
 Pons forms a bridge between medulla and
midbrain.

Functions of Pons
 1. Pons forms the pathway that connects
cerebellum with cerebral cortex.
 2. Pyramidal tracts pass through the pons
Pons contains the pneumotaxic and apneustic
centers for regulation of respiration
 . It also contains the vestibular nuclei, which
are already mentioned in medulla
oblongata. „

 MIDBRAIN
 Midbrain lies between pons and diencephalon.
 It consists of two parts: A. Tectum B. Cerebral
peduncles.
 The midbrain, or mesencephalon, is the most
rostral part of the brainstem that connects
the pons and cerebellum with the forebrain. For
most of its part, the midbrain sits in the
posterior cranial fossa, traversing the hiatus of
the tentorium cerebelli.
 The midbrain is the shortest part of the
brainstem. However, it contains many important
structures that make it essential for the proper
functioning of the body:

It also has many important centers which
control the vital functions.
1. Respiratory Centers Dorsal and ventral
group of neurons form the medullary
respiratory centers, which maintain
normal rhythmic respiration.

 2. Vasomotor Center :
Vasomotor center controls blood pressure and
heart rate.
 3. Deglutition Center
 Deglutition center regulates the pharyngeal
and esophageal stages of deglutition.
 4. Vomiting Center
 Vomiting center induces vomiting during
irritation or inflammation of gastrointestinal
(GI) tract.
 5. Superior and Inferior Salivatory
 Nuclei Salivatory nuclei control the secretion
of saliva

 Eye movement, ocular and auditory reflexes,
breathing, pain modulation, mood
regulation, enables the passage of the major
ascending and descending pathway

Vestibular Nuclei
 Vestibular nuclei contain the second order
neurons of vestibular nerve. There are four
vestibular nuclei, situated in the rostral part
of medulla and caudal part of pons, namely
superior, medial, lateral and inferior
vestibular nuclei. Medial and inferior
vestibular nuclei extend into medulla

 ANATOMICAL DIVISIONS
 On structural basis, the whole cerebellum is
divided into three portions:
 1. Anterior lobe
 2. Posterior lobe
 3. Flocculonodular lobe.
 1. Anterior Lobe : Anterior lobe includes
lingula, central lobe and culmen. It is
separated from posterior lobe by primary
fissure.


 2. Posterior Lobe: Posterior lobe consists of
lobulus simplex, declive, tuber, pyramid,
uvula, paraflocculi and the two portions of
hemispheres, viz. ansiform lobe and
paramedian lobe.
 3. Flocculonodular Lobe: Flocculonodular
lobe includes nodulus and the lateral
extension on either side called flocculus. It is
separated from rest of the cerebellum by
posterolateral fissure

CNS PART 2.pptx

More Related Content

Similar to CNS PART 2.pptx

More from Santhi Dasari

Recently uploaded

CNS PART 2.pptx