The document provides a detailed overview of the human nervous system, including its divisions, terminology, neuron types, synapses, and neurotransmitters. It also describes the organization and functions of the brain, specifically focusing on the cerebrum, its lobes, and associated motor areas. Additionally, it discusses cerebrospinal fluid, its properties, and the protective structures surrounding the central nervous system.

1. Nervous System
• Ajita Sadhukhan
• Reeya Amin
• Ashwin Kujur
• Vishwa Gandhi
Pharm D 4th Year
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2. Introduction
Afferent Division
→ Receptors within Joints, Skin,
Skeletal muscle (somatic –
sensory fibres)
Efferent Division
→ Skeletal muscle fibres
(somatic – motor fibres)
Sensory receptors within
visceral organs (visceral
– sensory fibres)
Smooth muscle within
visceral organs, cardiac
muscle, glands (visceral –
autonomic motor fibres)
Central
Nervous
System
Functional Subdivisions of the Nervous System
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3. A Few Terminologies
Terms Definitions
Nerve Fibre Axon
Nerve Bundle of nerve fibres outside the CNS
Tract Bundle of nerve fibres inside the CNS
Ganglion Collection of nerve cell bodies outside the CNS
Nucleus Collection of nerve cell bodies inside the CNS
Sensory Neuron Neuron that transmits impulses from a sensory receptor to the
CNS
Motor Neuron Neuron that transmits impulses from the CNS to the effector
organ, e.g. muscle
Somatic motor nerve Nerve that stimulates contraction of skeletal muscles
Autonomic motor nerve Nerve that stimulates contraction/inhibition of smooth and
cardiac muscles
Nerve plexus Network of intercalated nerves
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4. Neuron and its types
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5. Neuroglia
Cell Type Functions
Astrocytes • Help in the formation of blood-brain barrier, regulate ion, nutrient,
and dissolved gas concentrations
• Form scar tissue after injury to brain (gliosis)
Oligodendrocytes Form myelin sheath around the CNS axons
Microglia* Remove cellular debris, and pathogens in CNS by phagocytosis
Ependymal cells Line ventricles of the brain and central canal of the spinal cord.
Assist in production, circulation and monitoring of CSF.
Satellite cells Surround nerve cell bodies in peripheral ganglia and provide
nutrition to them
Schwann cells • Form myelin sheath around axons in PNS
• Helps in regeneration of nerve fibres after injury
*All the neuralgia are derived from ectoderm except microglia which are derived from
mesoderm.
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6. Types of Synapses and
Transmission of Nerve Impulse
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7. Neurotransmitters and their
effects
Neurotransmitter Typical effects
Acetylcholine Excitatory
Amines
• Noradrenaline
• Adrenaline
• Serotonin
• Dopamine (DOPA)
• Histamine
• Excitatory
• Excitatory
• Inhibitory
• Inhibitory
• Inhibitory
Amino acids
• Gamma-aminobutyric acid (GABA)
• Glycine
• Glutamate
• Aspartate
• Inhibitory
• Inhibitory
• Excitatory
• Excitatory
Neuropeptides
• Substance P
• Endorphins
• Enkephalins
• Excitatory
• Inhibitory
• Inhibitory
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8. Receptors and its associated
functions
Receptor Function (sensory modality)
Free nerve endings Pain, touch, temperature (heat and cold)
and pressure
Merkel’s discs Touch and pressure
Hair follicle receptor Touch
Meissner’s corpuscles Touch (two-point tactile discrimination)
Pacinian corpuscles Pressure and vibration
Ruffini’s corpuscles Stretch
Neuromuscular spindles Elongation of muscle (stretch)
Neurotendinous spindles Muscle tension
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9. Meninges
• The brain and spinal cord are enclosed in three protective membranes called
meninges. From without inwards these are: (a) dura mater, (b) arachnoid
mater, and (c) pia mater.
• The dura mater is mesodermal in origin while arachnoid and pia mater are
ectodermal in nature.
• The dura mater is the thick outermost covering of the brain and spinal cord.
The part enclosing the brain is called cranial/cerebral dura, and the part
around the spinal cord, the spinal dura. It is very tough, opaque, inelastic
membrane of fibrous tissue (dura=tough; mater=mother). It is also called
pachymeninx (pathy=thick).
• The arachnoid mater (arachnoid=cobweb like) is a delicate, avascular
membrane deep to dura mater. Many thread like tuberculae extend from it to
the pia mater.
• The pia mater (pia=tender) is a thin, transparent, vascular membrane closely
adherent to the surface of the brain and spinal cord.
• The arachnoid mater and pia mater are together termed as leptomeninges
(lepto=thin).
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10. Ventricles of the brain
• The brain contains 4 irregular-shaped cavities, or ventricles, containing the
cerebrospinal fluid (CSF). They are:
– Right and left lateral ventricles
– Third ventricle
– Fourth ventricle
• The lateral ventricles: These cavities lie within the cerebral hemispheres, one on
each side of the median plane just below the corpus callosum. They are separated
from each other by a thin membrane, the septum lucidum, and are lined with ciliated
epithelium. They communicate with the third ventricle by interventricular foramina.
• The third ventricle: The third ventricle is a cavity situated below the lateral
ventricles between the two parts of thalamus. It communicates with the fourth
ventricle by a canal, the cerebral aqueduct.
• The fourth ventricle: The fourth ventricle is a diamond-shaped cavity situated below
and behind the third ventricle, between the cerebellum and pons. It is continuous
below with the central canal of the spinal cord and communicates with the
subarachnoid space by foramina in its roof. CSF enters the subarachnoid space
through these openings and through the open distal end of the central canal of the
spinal cord.
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11. Cerebrospinal fluid (CSF)
• CSF is somewhat similar to that of blood plasma and interstitial fluid. It is
present in the ventricular system within the CNS and in the subarachnoid
space surrounding the CNS. It bathes both the external and internal
surfaces of the brain and spinal cord and provides a protective cushion
between the CNS and the surrounding bones,
• In an adult, the total volume of CSF is about 150 ml, out of which only 30
ml is in ventricular system and remaining in the subarachnoid space.
• CSF is a clear, colourless and slightly alkaline fluid with a specific gravity
of 1005-1008. It contains urea, creatinine, inorganic salts, and traces of
protein and glucose similar to that of blood plasma. But it has a much
lower protein content than the plasma and the glucose content is about
half to that of blood, and the chloride content is slightly more in CSF.
• Normally CSF is almost cell-free having only 0-5 lymphocytes/cu. mm. In
bacterial meningitis, the fluid is cloudy, with raised protein content and
vastly increased number of cells.
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12. Special Properties of CSF
1. Due to presence of blood-CSF
barrier:
– Antibodies are not found in the CSF
hence infections of the CNS are often
fatal.
– Bile is not found in CSF, even in severe
jaundice.
– Most of the drugs cannot reach CSF.
2. There is no CSF-brain barrier,
hence if drugs are injected into
the subarachnoid space
(intrathecal injections), they
soon enter the extracellular
spaces around the neurons
and neuroglia.
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13. Functions of CSF
• It serves as a cushion between the CNS and the surrounding bones.
• CSF acts as a shock absorber (i.e., it prevents or diminishes the
transmission of jarring or shocking forces to the CNS).
• It supports the brain and the spinal cord, and maintains a uniform
pressure upon them. The brain simply floats in the CSF, and it has been
stated that a brain weighing 1,500 g in air, weighs no more than 50 g in
the cerebrospinal fluid.
• Change in the intracranial volume is sometimes compensated by the
controlled production and absorption of CSF. For example, if blood
volume of the brain increases then more CSF drains away. Conversely, if
brain’s blood volume reduces, more CSF is retained.
• It nourishes the CNS.
• CSF removes the metabolites (waste products) from the CNS.
• It serves as a pathway for pineal secretions to reach the pituitary gland.
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14. Nervous System
Central Nervous
System
Brain
Spinal Cord
Peripheral
Nervous System
Somatic
Nervous System
Autonomic
Nervous System
Parasympathetic
Nervous System
Sympathetic
Nervous System
Classification of Nervous
System
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15. The Central Nervous System
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16. Adult Derivatives of Brain Vesicles
Primary brain
vesicles (3)
Secondary brain
vesicles (5)
Parts of adult brain Parts of ventricular
system
Prosencephalon
(forebrain)
• Telencephalon
• Diencephalon
• Cerebral
hemispheres
- Thalamus
- Hypothalamus
- Subthalamus
- Epithalamus
• Lateral ventricles
• Third ventricle
Mesencephalon
(midbrain)
• Mesencephalon • Midbrain • Cerebral
aqueduct
Rhombencephalon
(hindbrain)
• Metencephalon
• Myelencephalon
• Pons
• Cerebellum
• Medulla oblongata
• Fourth ventricle
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17. Brain
• The brain is that part of the CNS which lies within the
cranial cavity.
• The functions of the brain are as follows:
– It receives information from, and controls the activities of trunk
and limbs mainly through its connections with the spinal cord.
– It receives the information from, and controls the activities of
head and neck structures through cranial nerves.
– It assimilates experiences, a requisite to higher mental
processes such as memory, learning and intelligence.
– It is also responsible for one’s personality, thoughts and
aspirations.
• Parts of the brain:
– The adult brain constitutes about one-fiftieth of the body
weight and weighs about 1400 g in males and 1200 g in
females.
– It consists of six major parts: The cerebrum, the diencephalon,
the midbrain, the medulla oblongata and the cerebellum.
– The midbrain, pons and medulla oblongata collectively form
the brain stem.
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18. The Forebrain
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19. Cerebrum
• The cerebrum is the largest part of the human brain that fills most of the cranial cavity. Its
large size is the result of progressive centralization (telencephalization) of the various higher
sensory and motor centres of the brain during evolution.
• The cerebrum is a heavily convoluted bilobed structure. The two lateral halves are called
cerebral hemispheres.
• A deep median cleft, the longitudinal cerebral fissure, incompletely separates the two
cerebral hemispheres. Both in front and behind, the cleft is complete, but in the central part the
cleft extends downwards up to the corpus callosum which is a large mass of white fibres joining
the two cerebral hemispheres across the medial plane.
• the longitudinal cerebral fissure is occupied by the following structures:
– Falx cerebri (a sickle-shaped fold of dura mater).
– Fold of arachnoid the follows the surfaces of falx cerebri.
– Pia mater covering the medial surface of falx cerebri.
– Anterior cerebral arteries and veins (which lie in the subarachnoid space between the arachnoid and pia)
• Each cerebral hemisphere consists of:
– An outer layer of grey matter called cerebral cortex,
– An inner mass of white matter,
– Large masses of grey matter embedded in the basal part of white matter called basal ganglia/basal
nuclei, and
– A cavity within it called lateral ventricle.
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20. External features of the cerebral
hemisphere
• Poles:
– Each cerebral hemisphere presents 3 poles – frontal, occipital and temporal. The
anterior end of the hemisphere is the frontal pole and the posterior end the
occipital pole. The temporal pole is below and in front at the junction of orbital
and tentorial surfaces.
• The frontal pole at thee anterior end of the hemisphere is more rounded than the occipital pole. It
lies opposite the medial part of the superciliary arch.
• The occipital pole at the posterior end of the hemisphere is more pointed than the frontal pole. It
lies at a short distance superolateral to the external occipital protuberance.
• The temporal pole between frontal and occipital poles points forwards. It fits into the anterior part
of the middle cranial fossa and is overhung by the lesser wing of the sphenoid.
• Surfaces:
– Each cerebral hemisphere has 3 surfaces – superolateral, medial, and inferior.
• The superolateral surface is the most convex and most extensive. It faces upwards and laterally
and conforms to the corresponding half of the cranial vault.
• The medial surface is flat and vertical. It presents a thick C-shaped cut surface of the corpus
callosum.
• The inferior surface is irregular to adopt the floors of anterior and middle cranial fossae. It is
divided into 2 parts by a deep horizontal groove or sulcus, the stem of lateral sulcus, viz. (a) a small
anterior part, the orbital surface, and (b)a large posterior part, the tentorial surface.
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21. • Borders:
– Each cerebral hemispheres presents with six borders, viz. superomedial, superciliary,
inferolateral, medial orbital, medial occipital and inferomedial.
• The superomedial border separates the superolateral surface from the medial surface.
• The superciliary border is at the junction of superolateral and orbital surfaces. Itlies just behind
the superciliary arch hence its name.
• The inferolateral border separates the superolateral surface from the tentnial surface. Posteriorly
this border exhibits a notch, the perioccipital notch about 3 cm in front of the occipital pole.
• The medial orbital border separates the medila surface from the orbital surface.
• The infeomedial/hippocampal border surrounds the cerebral peduncle. It is formed by the
medial aspect of uncus and parahippocampal gyrus.
• The medial occipital border separates the medial surface from the tentorial surface.
• Sulci and Gyri:
– The cerebral cortex (the surface layer of grey matter) is highly exclusive in man. To
accommodate it in the limited space available within the rigid cranial cavity, the surface of
cerebral hemisphere becomes folded, producing numerous convolutions separated by
fissures. These convolutions and fissures are termed gyri and sulci respectively. In
human brain the total surface area of cerebral hemisphere is about 2000 sq. cm but
approximately 2/3rd of this is hidden from surface view within the walls of the sulci.
– The gyri consist of a central core of white matter covered by a layer of grey matter.
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22. Lobes of the Cerebral Hemisphere
• The superolateral surface of the
cerebral hemisphere is arbitrarily
divided into 4 lobes – frontal, temporal,
lateral and occipital with the help of:
– Three main sulci central, lateral and parieto-
occipital, and
– Two imaginary lines
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23. Functions of the Cerebrum
• Three main varieties of activities associated with the cerebral cortex include:
– Mental activity involved in memory, intelligence, sense of responsibility, thinking,
reasoning, moral sense, and learning are attributed to the higher centres.
– Sensory reception including the perception of pain, temperature, touch, sight,
hearing, taste and smell.
– Initiation and control of sensory (voluntary) muscle contraction.
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24. Motor areas of the cerebrum
• The precentral (motor) area:
– This lies in the frontal lobe immediately anterior to the central sulcus. Cell bodies
initiate the contraction of the skeletal muscles.
• Nerve fibres initiated from the motor region passes downwards through the internal
capsule → medulla oblongata → crosses to the opposite side in the spinal cord.
• This means that the motor area in the right hemisphere of the cerebrum controls the
voluntary muscle movement on the left side of the body and vice-versa.
– The neuron with its cell body in the cerebrum is the upper motor neuron and the
other with its cell body in the spinal cord is the lower motor neuron.
– Damage to either of these neurons will result in paralysis.
– In the motor area of the cerebrum the body is represented upside down, i.e., the
cells nearest to the vertex (the point of intersection of lines) control the feet and
those in the lowest part control the head, neck, face and fingers.
– The sizes of the different areas of the cortex representing different areas of
the body are proportional to the complexity of movement of the body part, and
not its size.
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25. • The premotor area:
– It lies in the frontal lobe immediately anterior
to the motor area.
– Controls influence over the motor area,
ensuring an orderly series of movements. For
example, in tying a shoe lace or writing, many
muscles contract but the movements must be
coordinated and carried out in a particular
sequence.
– In the lower part of this area just above the
lateral sulcus there is a group of nerve cells
called the motor speech area which controls
the movements necessary for speech.
• The frontal lobe:
– This extends anteriorly from the premotor area
to include the remainder of the frontal lobe.
– It is a large area and it is highly developed in
humans than in other animals.
– It is thought that communication between this
and other regions in the cerebrum are
responsible for behaviour, character, and
emotional state of the individual.
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26. Sensory areas of the cerebrum
• The postcentral (sensory) area:
– This area is behind the sensory sulcus.
– Here sensations of pain, temperature, pressure, touch, knowledge of muscular
movement and positions of joints are perceived.
– The sensory area of the right hemisphere receives impulses from the left side of
the body and vice versa.
• The parietal area:
– This lies behind the postcentral (sensory) area and includes the greater part of
the parietal lobe of the cerebrum.
– Its functions are believed to be associated with obtaining and retaining
accurate knowledge of objects. It has been suggested that the objects can be
recognized by touch alone because of the knowledge from the past
experience (memory) retained in this area.
• The sensory speech area:
– This is situated in the lower part of the parietal lobe and extends into the
temporal lobe.
– It is here that the spoken word is perceived.
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27. • There is a dominant area in the left
hemisphere in the right handed people
and vice versa.
– The size of the areas representing
different parts of the body is proportional
to the extent of sensory interventions.
• The auditory (hearing) area:
– This lies immediately below the lateral
sulcus within the temporal lobe.
– The cells receive and interpret impulses
transmitted from the inner ear by the
cochlear (auditory) part of the
vestibulocochlear nerves (8th cranial
nerves).
• The olfactory (smell) area:
– This lies deep within the temporal lobe
where impulses from the nose via the
olfactory nerves (1st cranial nerves) are
received and interpreted.
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28. • The taste area:
– This is thought to lie just above the lateral sulcus in the deep layers of the
sensory area.
– This is the area where impulses from special nerve endings in taste buds in the
tongue and in the lining of the cheeks, palate and pharynx are perceived as
taste.
• The visual area:
– This lies behind the parieto-occipital sulcus and includes the greater part of the
occipital lobe.
– The optic nerves (2nd cranial nerves) pass from the eye to this area which
receives and interprets the impulses as visual impressions.
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29. Other areas of the cerebrum
• Deep within the cerebral
hemispheres there are
groups of cell bodies
called nuclei (previously
called ganglia) which act
as relay stations where
impulses are passed
from one neuron to the
next in a chain.
• Important masses of grey
matter include:
– Basal nuclei
– Thalamus
– hypothalamus
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30. • Basal nuclei:
– These are the areas of grey matter, lying deep within the cerebral
hemispheres having connections within the cerebral cortex and thalamus.
– The basal nuclei are thought to be involved in initiating muscle tone (normal
elasticity of muscle) in slow and coordinated activities.
– If control is inadequate or absent, movements are jerky, clumsy and
uncoordinated.
• Thalamus:
– The thalamus consists of two masses of nerve cells and fibres situated
within the corpus callosum (largest commissure of the brain connecting the
cerebral cortex of the two hemispheres), 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.
• Hypothalamus:
– 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.
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31. – The hypothalamus is linked to the posterior lobe of the pituitary gland and 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
the lobes of the gland.
Other functions of the hypothalamus:
– Hypothalamus is associated with the control of:
• The ANS (autonomic nervous system) → involuntary functions
• Appetite and satiety (a state of being satisfactorily full and unable to take on more), thirst and water
balance
• Body temperature
• Emotional reactions, i.e., pleasure, fear and rage (a state of extreme anger)
• Biological clocks or circadian rhythms, i.e., sleeping and waking cycles, body temperature and
secretion of some hormones.
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32. The Midbrain
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33. BRAINSTEM
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34. • The brain stem consist of diffuse system of nerve cells and nerve fibres called
reticular formation.
• FUNCTIONS OF BRAIN STEM:
– It provides passage to various ascending descending tracts that connect the spinal cord to
the different part of the forebrain.
– It contains important autonomic reflex centres associated with the control of the
respiration, heart rate and blood pressure.
– It contains reticular activating system which control consciousness.
– It contains important nuclei of the last ten cranial nerves (i.e., 3rd to 12th)
– The midbrain is the upper and shortest part of the brain stem.
– It is about 2.5 cm long and 2.5 cm wide. It connects the hindbrain with the forebrain.
– The midbrain like the other parts of the brainstem consists of grey and white matter.
• ANTERIOR SURFACE:
– Anteriorly ,it presents two large bundles of fibres on each side of the midline, called crus
cerebri.
– The oculomotor nerve emerges from the medical aspect of the crus of the same side.
– The crus cerebri bounds the interpeduncular fossa on either side.
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35. 3/26/2020 35

36. STRUCTURAL COMPONENTS AND
FUNCTIONS OF MID BRAIN
COMPONENTS FUNCTIONS
GREY MATTER
Superior colliculi Reflex centres for visual reflexes.
Inferior colliculi Lower auditory centres,probably concerned with
reflexes involving auditory stimuli.
Red nuclei Involuntary control of muscle tone and posture.
Substantia nigra Regulate the activity of basal nuclei.
WHITE MATTER
Cerebral peduncles containing number of ascending
descending tracts
Provides passage to the fibres of motor and sensory
tracts.
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• POSTERIOR SIDE:
– Posteriorly, the midbrain presents four rounded swellings called colliculi-one superior and
inferior colliculi one on each side.
– Each colliculus is laterally related to a ridge called brachium.
• STRUCTURE OF MIDBRAIN:
– The midbrain comprises two lateral halves called-Cerebral peduncles: which is again
divided into two parts by a pigmented band of grey matter, substantia nigra.
1)Anterior part: Crus cerebri
2)Posterior part: Tegmentum

37. • Arterial supply: Basilar artery through its
posterior cerebral and superior cerebellar
arteries. Basilar artery also supplies
midbrain through direct branches.
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BLOOD SUPPLY OF THE
MIDBRAIN

38. The Hindbrain
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39. PONS
• The pons is the middle part of
brainstem and situated between
the midbrain and medulla.
• On either side, the pons is
continuous as the middle
cerebellar peduncle, thus
forming a bridge between the
two cerebellar hemispheres,
hence its name ,pons.
• Pons is about 2.5 cm long and
forms the upper half of the floor
of the fourth ventricle.
• Structurally the pons consist of
grey and white matter
consisting number of nuclei and
fibre tracts respectively.
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40. STRUCTURAL COMPONENTS AND
FUNCTIONS OF THE PONS:
COMPONENTS FUNCTIONS
GREY MATTER
Pontine nuclei Relay stations of corticopontine fibres and give origin to
the pontocerebellar fibres.
Nuclei of 5th,6th,7t and 8th cranial nerves Give or receive nerve fibres of the cranial nerves.
Pontine respiratory centre Modifies the output of the respiratory centre in the
medulla.
WHITE MATTER
Ascending and descending tracts Subserves the motor and sensory functions.
Transverse pontocerebellar fibres Forms the distal segment of the recently evolved cortico
ponto cerebellar pathway.
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41. EXTERNAL FEATURES OF PONS:
• The pons has two surfaces: a ventral and a dorsal.
• And two borders : a superior and an inferior.
• VENTRAL SURFACE :
– It is also known as anterior surface.
– Ventral surface is convex in the both directions i.e. from before backwards and from side to
side.
– The trigeminal nerve is attached to this surface by two roots; a small motor and a large
sensory root.
• DORSAL SURFACE:
– It is also known as posterior surface.
– The dorsal surface of the pons is covered by the cerebellum and separated from it by the
cavity of fourth ventricle.
– The dorsal surface of pons is triangular in shape and forms upper part of fourth ventricles.
• SUPERIOR BORDER:
– The cerebral peduncles are attached to this border.
• INFERIOR BORDER:
– The upper end of the medulla is continuous with this border.
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42. INTERNAL STRUCTURE OF
PONS:
• A cross section at any level of pons shows two distinct regions:
➢ A large ventral or basilar part,
➢ A small dorsal or tegmental part.
The ventral or basilar part is continuous inferiorly with the pyramids of the medulla and
on each side with the middle cerebellar penducle.
The dorsal or tegmental part is direct upward continuation of the medulla excluding the
pyramids.
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BLOOD SUPPLY OF PONS:
• The pons is supplied by the following arteries:
➢ Numerous pontine branches from the basilar artery.
➢ Anterior inferior cerebellar artery.

43. MEDULLA OBLONGATA
• The medulla oblongata is the direct upward
continuation of the spinal cord,extending from the
foramen magnum to the lower border of the pons.
• The medulla is shaped like a truncated cone(bulb like)
hence its alternative name “bulb”.
• Medulla oblongata measures about 3 cm in lenghth, 2
cm in breadth and 1.25 cm in thickness.
• The medulla contains vital centres which are
essential for life. These are cardiac centre,
vasomotor centre and respiratory centre.
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44. 3/26/2020 44

45. STRUCTURAL COMPONENTS AND
FUNCTIONS OF THE MEDULLA OBLONGATA
COMPONENTS FUNCTIONS
GREY MATTER
Nucleus gracilis and nucleuscuneatus Relay propioceptive sensations to the thalamus
Olivary nuclei Relay information associated with voluntary muscle
movement to the cerebellum.
Vital centres
• Cardiac centre Regulate heart rate and force of contraction.
• Vasomotor centre Regulates distribution of blood flow in vessels.
• Respiratory centre Regulates respiratory movements.
other nuclei Relay ascending sensory information from spinal cord to
the higher centres.
WHITE MATTER
Ascending and descending tracts Connect the spinal cord with other parts of the brain.
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46. FEATURES OF MEDULLA
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FEATURES OF THE ANTERIOR(VENTRAL) ASPECT OF MEDULLA:
• Pyramids:
– These are two elongated elevations, one on either
side of anterior median fissure and are produced by
the pyramidal fibres. Most of these fibres about
75% cross to the opposite side in the lower part of
the medulla and then descend as lateral
corticospinal tract in the lateral white column of the
spinal cord.
– About 20% of uncrossed fibres run downwards as
anterior corticospinal tract in the anterior white
column of the spinal cord, and remaining 5% run
downwards along with uncrossed fibres in the
lateral white column of the spinal cord.
• OLIVES:
– These are oval elevations,posterolateral to the
pyramids and are produced by an underlying mass
of grey matters called inferior olivary nucleus.
• Rootlets of the hypoglossal nerves:
- These emerge from the anterolateral sulcus between the pyramid and the olive.

47. • The dorsal aspect the medulla is well demarcated into lower closed and upper open
parts.
• FEATURES OF CLOSED PART:
– The closed part on either side of the posterior median sulcus presents three longitudinal elevations.
• FEATURES OF THE OPEN PART:
– The open part of medulla forms the lower part of the forth ventricle, which present number of features
like medial sulcus, hypoglossal and vagal triangles.
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FEATURES ON THE POSTERIOR(DORSAL)
ASPECT OF MEDULLA:
INTERNAL STRUCTURE OF MEDULLA
• In the medulla the white matter surrounds the central mass of grey matter but in the
later the grey matter is broken up into the nuclei that are separated by nerve fibres.
• The internal structure of medulla is well appreciated by examining its transverse
section at the four levels.
➢ At the level of decussation of pyramids.
➢ At the level of decussation of medial lemnisci
➢ At the level of olives
➢ At the level just inferior to the pons.

48. BLOOD SUPPLY TO MEDULLA
• The medulla is
supplied by
following arteries.
➢ Two vertebral
arteries.
➢ Anterior and
posterior spinal
arteries.
➢ Anterior and
posterior inferior
cerebellar arteries.
➢ Basilar arteries.
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49. CEREBELLUM
• The cerebellum is the largest part of the
hindbrain and second largest part of the
brain as whole.
• Its weight about 150 g.
• It is located in the posterior cranial fossa
underneath the tentorium cerebelli and
behind the pons and medulla oblangata.
• It is separated froms pons and medulla by
a cavity of the fourth ventricle.
• The cerebellum is connected to the
brainstem by these three pairs of large
fibre tracts called cerebellar peduncles.
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• The three primary functions of the
cerebellum are:
➢ Maintenance of posture.
➢ Maintenance of muscle tone.
➢ Coordination of voluntary motor activity.

50. EXTERNAL FEATURES OF
CEREBELLUM:• The external features of the cerebellum comprise three parts, two surfaces, two notches,
and three well marked fissures.
• PARTS OF CEREBELLUM:
– The cerebellum consist of two large lateral hemisperical lobes, the cerebellar hemispheres which are united to
each other by a narrow median worm like portion calle vermis.
– The superior and inferior aspects of vermis are termed superior and inferior vermis respectively.
– The ridge like superior vermis is continuous on the either side with the superior surface of cerebellar hemisphere
imperreptively.
– The inferior vermis is more clearly demarcated from the hemispheres in the floor of vallecula cerebelli.
• SURFACES OF CEREBELLUM:
– The superior surface of the cerebellum is convex.
– The two cerebellar hemispheres are continuous with each other on this surface.
– The inferior surface presents a deep median notch called vallecula which separates the two cerebellar
hemispheres.
– The floor of the valeculla is formed by inferior vermis and is limited on each side by sulcus valleculae.
• NOTCHES OF CEREBELLUM:
– The anterior aspect of the cerebellum is marked by a wide shallow anterior cerebellar notch which accomodates
pons and medulla.
– The posterior cerebellar notch is deep and narrow, the lodges the flax cerebelli.
• FISSURES OF CEREBELLUM:
– The horizontal fissure is most conspicuous and runs along the lateral and posterior margins of the cerebellum.
It marks the junction between the superior and inferior surfaces of the cerebellum.
– The posterolateral fissure lies on the inferior surface of the cerebellum and separates the flocculomodular lobe
from the rest of the cerebellum.
– The V-shaped fissura prima on the superior surface cuts the superior vermis at the junction of its anterior two-
third and posterior one-third.
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51. • SUBDIVISIONS OF CEREBELLUM:
➢Anatomical subdivisons
➢Morphological subdivisons
• Anatomically cerebellum is divided in to three lobes:
➢ The anterior lobe.
➢ The posterior/middle lobe.
➢ The flocculonodular lobe.
• Based on functional criteria and phylogenetic the cerebellum is divided
into three parts:
➢ Vestibular cerebellum.
➢ Spinal cerebellum.
➢ Cerebral cerebellum.
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SUBDIVISONS OF CEREBELLUM:

52. SUBDIVISONS OF CEREBELLUM:
• Vestibular cerebellum: It mainly concerned with the maintenance of
equilibrium,posture and tone of trunk muscles.
• Spinal cerebellum: It mainly concerned with tone,posture and movements of limbs.
• Cerebral cerebellum: It mainly concerned with smooth performance of voluntary
movements.
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INTERNAL STRUCTURE OF CEREBELLUM
• The cerebellum is made up of a thin surface layer of grey matter, the cerebellar
cortex and a central core of white matter.embedded within the central core of white
matter are masses of grey matter called intracerebellar nuclei.
• GREY MATTER:
The grey matter of the cerebellum is represented by:
a)The cerebellar cortex and
b) The intracerebellar nuclei
• Cerebellar cortex consists of three distinct layers:
➢ An outer molecular layer.
➢ An intermediate purkinje cell layer.
➢ An inner granular layer.

53. – INTRACEREBELLAR
NUCLEI:
• The intracerebellar
nuclei are masses of
grey matter
embedded in the
white matter of the
cerebellum. on each
side of the midline
they are four in
number.
• WHITE MATTER:
– The white matter of
cerebellar is made up of
three types of fibres:
a)Instrinsic,
b)Afferent, and
c)Efferent.
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54. ARTERIAL SUPPLY OF THE
CEREBELLUM:
• The cerebellum is supplied by three pairs of
cerebellar arteries.
➢Superior cerebellar artery,
➢Anterior inferior cerebellar artery,
➢Posterior inferior cerebellar artery.
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55. What is Peripheral Nervous
System?
• The peripheral
nervous system
(PNS) is the division
of the nervous
system containing all
the nerves that lie
outside of the central
nervous system
(CNS).
• Primary role:
to connect the
CNS to the organs,
limbs and skin. These
nerves extend from the
central nervous system
to the outermost areas
of the body.
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56. PERIPHERAL NERVOUS SYSTEM
(PNS)
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57. Somatic Nervous System
• The part of the peripheral nervous system responsible for
carrying sensory and motor information to and from the
central nervous system.
• Derives its name from the Greek word soma, which means
“body”.
• Responsible for transmitting sensory information as well as
for voluntary movement.
Contains two major types of neurons:
• Sensory neurons (or afferent neurons) - carry information
from the nerves to the central nervous system
• Motor neurons (or efferent neurons) - that carry
information from the brain and spinal cord to muscle fibres
throughout the body.
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58. Sensory-Somatic Nervous System
• The sensory-somatic
system consists of
– 12 pairs of cranial
nerves and
– 31 pairs of spinal
nerves.
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59. • Cranial Nerves - Nerves that emerge
directly from the brain, in contrast to
spinal nerves, which emerge from
segments of the spinal cord. In
humans, there are traditionally twelve
pairs of cranial nerves. Only the first
and the second pair emerge from the
cerebrum; the remaining ten pairs
emerge from the brainstem.
• Spinal Nerves - Spinal nerves or
nerve roots, branch off the spinal cord
and pass out through a hole in each of
the vertebrae called the Foramen.
These nerves carry information from
the spinal cord to the rest of the body,
and from the body back up to the brain.
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60. 3/26/2020 60
Cranial nerves

61. • Sensory neurons running from stimulus
receptors that inform the CNS of the stimuli
• Motor neurons running from the CNS to the
muscles and glands - called effectors - that take
action.
It is responsible for monitoring conditions in the
internal environment and bringing about
appropriate changes in them. The contraction of
both smooth muscle and cardiac muscle is
controlled by motor neurons of the autonomic
system.
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62. 3/26/2020 62

63. Spinal nerves
• 31 nerves containing
the spinal-
cord and various
body region.
– 8 paired cervical
nerves
– 12 paired thoracic
nerves
– 5 paired lumber
nerves
– 5 paired sacral
nerves
– 1 pair of coccygeal
nerves
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64. Autonomic Nervous System
• Is the part of the
peripheral nervous
system responsible for
regulating involuntary
body functions, such as
blood flow, heartbeat,
digestion and breathing.
• Further divided into two
branches:
– Sympathetic system
regulates the flight-or-
fight responses.
– Parasympathetic
system helps maintain
normal body functions
and conserves physical
resources.
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65. 3/26/2020 65

66. Sympathetic Nervous System
• The sympathetic nervous system is located to the sympathetic chain, which connects
to skin, blood vessels and organs in the body cavity. The sympathetic chain is
located on both sides of the spine and consists of ganglia.
• stimulates heartbeat
• raises blood pressure
• dilates the pupils
• dilates the trachea and bronchi
• stimulates glycogenolysis — the conversion of liver glycogen into glucose
• shunts blood away from the skin and viscera to the skeletal muscles, brain, and heart
• inhibits peristalsis in the gastrointestinal (GI) tract inhibits contraction of the
bladder and rectum
• and, at least in rats and mice, increases the number of AMPA receptors in the
hippocampus and thus increases long-term potentiation (LTP).
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Sympathetic stimulation causes:

67. Parasympathetic Nervous System
• The Parasympathetic system is the branch of the Autonomic Nervous System (ANS)
responsible for the body’s ability to recuperate and return to a balanced state (known
as "homeostasis") after experiencing pain or stress.
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Parasympathetic stimulation causes:
• slowing down of the heartbeat
• lowering of blood pressure
• constriction of the pupils
• increased blood flow to the skin and viscera
• peristalsis of the GI tract

68. References
• Essentials of Medical Physiology by K.
Sembulingam, Prerna Sembulingam, 7th
edition, the Health Sciences Publisher.
• Clinical Neuroanatomy by Snell
• Clinical Neuroanatomy by Vikrant Singh
(Elsivier)
• Human Anatomy and Physiology by Ross and
WiIson
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