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NERVOUS SYSTEM
1. NERVOUS SYSTEM
Shri Vishnu College of Pharmacy (Autonomous)
Affiliated to Andhra Univ., Visakhapatnam; Approved by AICTE and PCI, New Delhi, and recognised by APSCHE
Prepared by
Grandhi Sandeep Ganesh
Dept. of Pharmacology
2. NERVOUS SYSTEM
DEFINITION
It can be defined as an organized group of
cells, called neurons, specialized for the
conduction of an impulse—an excited state—from
a sensory receptor through a nerve network to an
effector, the site at which the response occurs
The nervous system in human is made up of
brain, spinal cord, sensory organs and neurons
The nervous system maintains internal order
within the body by coordinating the activities of
muscles and organs, receives input from sense
organs, trigger reactions, generating learning and
understanding, and providing protection from
danger
4. Central Nervous System (CNS):
It consists of the brain and the spinal cord, which act as the integrating and
command centers of the nervous system
They interpret incoming sensory information and issue instructions based on past
experience and current conditions.
Peripheral Nervous System (PNS):
It is the part of the nervous system outside the CNS.
They link all parts of the body by carrying impulses from the sensory receptors to
the CNS and from the CNS to the appropriate glands or muscles.
It consists mainly of the nerves that extend from the brain and spinal cord.
Cranial Nerves carry impulses to and from the brain.
Spinal Nerves carry impulses to and from the spinal cord.
CLASSIFICATION OF NERVOUS SYSTEM
5. SYNAPSE
The junction between two neurons is called a
synapse.
It is a specialized junction where
transmission of information takes place
between a nerve fibre and another nerve,
muscle or gland cell.
It is not the anatomical continuation. But, it
is only a physiological continuity between
two nerve cells.
6. Structure
A presynaptic ending that contains neurotransmitters, mitochondria and other cell
organelles
A postsynaptic ending that contains receptor sites for neurotransmitters
A synaptic cleft or space between the presynaptic and postsynaptic endings. It is
about 20nm wide
Functions
The main function of the synapse is to transmit the impulses, i.e. action potential
from one neuron to another
They allow integration, e.g. an impulse travelling down a neuron may reach a
synapse which has several post synaptic neurons, all going to different locations.
The impulse can thus be dispersed. This can also work in reverse, where several
impulses can converge at a synapse
SYNAPSE STRUCTURE AND FUNCTIONS
7. NEUROTRANSMITTERS
Neurotransmitters are chemical messengers that
transmit signals from a neuron to a target cell
across a synapse.
Target cell may be a neuron or some other kind
of cell like a muscle or gland cell.
Necessary for rapid communication in synapse.
Neurotransmitters are packaged into synaptic
vesicles - presynaptic side of a synapse.
9. Synthesis: Neurotransmitters are synthesized by the enzymatic transformation of
precursors.
Storage: They are packaged inside synaptic vesicles.
Release: They are released from presynaptic terminal by exocytosis when calcium
enters axon terminal during an action potential Diffuse across the synaptic cleft to
the postsynaptic membrane.
Binding: They bind to receptor proteins.
Inactivation: The neurotransmitter is degraded either by being broken down
enzymatically, or reused by active reuptake.
STEPS IN NEUROTRANSMITTER PROCESSING
10. MENINGES
The meninges are three connective
tissue membranes that lie just
external to the brain and spinal cord
11. MENINGES
CNS is covered by 3 membranes called meninges which are separated by 2
spaces called subdural & subarachnoid
Meninges of brain are continuous with spinal meninges at foramen magnum. In
skull, dura is fused with periosteum of skull
The meninges layers are
Dura mater
Arachnoid
Pia mater
12. VENTRICLES OF THE BRAIN
Ventricles are the Communicating cavity
within the CNS that are lined by ependymal
cells, which produces, contains and
circulates CSF
The ventricular system comprises
1. Two lateral ventricles
2. 2. Single 3rd Ventricle
3. 3. Single 4th Ventricle and
4. 4. Single Terminal Ventricle
All of these are connected in series
via channels.
13. CEREBRO SPINAL FLUID
Cerebrospinal fluid ( CSF) is the clear, colourless
and transparent fluid that circulates through
ventricles of brain, subarachnoid space and
central canal of spinal cord.
It is the part of extra cellular fluid (ECF).
CSF is formed by choroid plexus, situated with
in the ventricles
PROPERTIES
VOLUME: 150mL
RATE OF FORMATION: 500-600 mL per
minute
SPECIFIC GRAVITY: 1.005
14. CEREBRUM
Cerebrum is the largest part of the brain
located in the cranial cavity
It is divided into 2 parts, namely
Diencephalon (central core)
Telencephalon (cerebral hemisphere)
On the surface of cerebrum large size folds
can be seen
Depressions on the surface of cerebrum
are known as Sulci
Elevations between sulci is known as
Gyri
15. CEREBRUM
Surfaces of cerebrum
Three surfaces:
Superolateral surface: Between Superomedial border and inferolateral border.
Medial Surface: Between Superomedial and inferomedial border.
Inferior Surface: Between Inferolateral and inferomedial border.
Three borders:
Superomedial border: between superolateral and medial surface.
Inferolateral border: between superolateral and inferior surface.
Inferomedial border: between inferior and medial surface.
Three poles:
Frontal pole: Anterior most part of cerebrum (frontal lobe)
Occipital pole: Posterior most part of cerebrum (Occipital lobe)
Temporal pole: Anterior most part of temporal lobe
16. CEREBELLUM
The cerebellum (Latin for little brain) is a
region of the brain that plays an important
role in motor control..
It is located at the back of the brain,
underlying the occipital and temporal lobes
of the cerebral cortex
The main parts two hemispheres vermis
Fissures primary fissure horizontal fissure (
prepyramidal fissure) posterior fissure
(posteroletral fissure)
Lobes include anterior lobe, posterior lobe
and Flocculonodular lobe
It consists of two parts outer grey matter
cerebellar cortex cerebellar nuclei inner
white matter
17. CEREBELLUM
Peduncles
Superior cerebellar peduncle : Connects to
midbrain. It Contains efferent fiber systems
extending to red nucleus and thalamus.
Middle cerebellar peduncle : Connects to
pons. It Contains fiber mass orginating from
pontine nuclei and represent continuation of
corticopontine tracts.
Inferior cerebellar peduncle : Connects to
medulla. It Contains spinocerebellar tracts and
connections to vestibular nuclei.
18. MID BRAIN
The midbrain develops from
mesencephalon. Cells within the midbrain
multiply continually and are compressed to
form cerebral aqueduct.
Connects the pons and cerebellum with the
forebrain.
It is about 0.8 inch in length
The midbrain is traversed by a narrow
channel called cerebral aqueduct filled with
CSF.
19. Anterior surface
Anteriorly, it presents two large bundles of
fibers, one on each side of the midline, called
crus cerebri
The oculomotor nerve emerges from the
medial aspect of the crus of the same side
The crus cerebri bounds the interpeduncular
fossa on either side.
MID BRAIN
20. MID BRAIN
Posteriorly, the midbrain presents four rounded swellings called colliculi- One
Superior and inferior colliculi on either side.
Each colliculus is laterally related to a ridge called brachium
Superior and inferior brachium arises from respective colliculi
Superior brachium connects the superior colliculus to lateral geniculate body
Inferior brachium connects the inferior colluculus to medial geniculate body
In the midline below the inferior colliculus, the trochlear nerve emerges which
then winds round the side of the midbrain to reach its ventral aspect
22. THALAMUS
It acts as a relay station that modulates and coordinates the function of various
systems
Locus for integration, modulation and intercommunication between various
systems
Its has important motor, sensory, arousal, memory, behavioural, limbic and
cognitive functions
The largest source of afferent fibres to thalamus is cerebral cortex and cortex is
the primary destination for projection fibres from the thalamus
23. HYPOTHALAMUS
Hypothalamus is described as “The Head ganglion
of the autonomic nervous system” by
“Sherrington”
Stimulation of the hypothalamus produces
autonomic response
It is a small bilateral structure extends from the
region of the optic chiasma to the caudal border of
the mammillary bodies
It lies below the Thalamus
Forms the floor and inferior part of the lateral
walls of the 3rd ventricle
It is an integrative center for regulation of
cardiovascular system, body temperature, food and
water intake and endocrine secretion
HT is only 0.3% of brain weight (10 gms)
24. HYPOTHALAMUS
Hypothalamic nuclei
It is typically divided into 4 regions from rostral to caudal
Pre optic area
Supra optic area (anterior)
Tuberal area (middle )
Mamillary area ( posterior)
27. BASAL GANGLIA
It is the Collection of masses of gray matter
situated within each cerebral hemisphere
They are paired & located between thalamus
and white matter
It Consist of 5 pairs of nuclei: These are
Caudate nucleus
Putamen
Globus pallidus
Substantia nigra
Subthalamic nucleus
28. BASAL GANGLIA
Two main circuits are
The Putamen Circuit For executing learned patterns of movement
The Caudate Circuit For Cognitive Control of Sequences of Motor Patterns
The term cognition means the thinking processes of the brain, using both
sensory input to the brain plus information already stored in memory. Most of
our motor actions occur as a consequence of thoughts generated in the mind, a
process called cognitive control of motor activity. The caudate nucleus plays a
major role in this cognitive control of motor activity.
29. FUNCTIONS OF BASAL GANGLIA
Function in association with the corticospinal system to control complex patterns
of motor activity(cutting paper with scissors, hammering nails, shooting a
basketball through a hoop, passing a football, throwing a baseball etc.
Cognitive control of motor activity e.g. if a person comes across a lion he will
subconsciously plan
Turning away from the lion,
Beginning to run, and
Even attempting to climb a tree
To Change the Timing and to Scale the Intensity of Movements
A lesions of the posterior parietal cortex produce an inability to accurately
perceive objects through normally functioning sensory mechanisms, a
condition called agnosia.
33. REFLEXES
The Reflex Arc is an automatic, rapid response to an adverse stimulus.
Action is involuntary the brain is not involved in the event but may be informed
of it
Many reflex actions are protective
Some complex actions (swallowing, coughing and blinking) are coordinated by
reflexes.
Five Essential Components to the Reflex Arc
Receptor – detects the stimulus
Afferent (sensory neuron) – transmits impulses to the CNS
Integration center – consists of one or more synapses in the CNS
Efferent (motor neuron) – conducts impulses from integration center to an
effector
Effector – muscle or gland cell, Responds to efferent impulses, Contraction or
secretion
35. TYPES OF REFLEXES
Monosynaptic reflex – simplest of all reflexes
Just one synapse
The fastest of all reflexes
Example – knee-jerk reflex
Polysynaptic reflex – more common type of reflex
Most have a single interneuron between the sensory and motor neuron
Example – withdrawal reflexes
37. OLFACTORY NERVE
Component: Sensory
Function: Smell
Origin: Olfactory receptor nerve cells
Opening to the skull: openings in
cribriform plate of ethmoid
38. OPTIC NERVE
Component: Sensory
Function: Vision
Origin: Back of the Eyeball
Opening to the skull: Optic Canal
39. OCCULOMOTOR NERVE
Component: Motor
Function:
Raises upper eyelid
Turns eyeball upward, downward and
medially
Constricts pupil
Accommodated the eye
Origin: Anterior surface of the midbrain
Opening to the skull: Superior orbital
fissure
40. TROCHLEAR NERVE
Component: Motor
Function: Assisting in turning eyeball
downward and laterally
Origin: Posterior surface of the midbrain
Opening to the skull: Superior orbital
fissure
41. TRIGEMINAL NERVE
Component: Motor and sensory
Function:
Opthalamic: sensory information from
the upper part of your face
Maxillary: sensory information from
the middle part of your face including your
cheeks, upper lip, and nasal cavity
Mandibular: It sends sensory
information from your ears, lower lip, and
chin. It also controls the movement of muscles
within your jaw and ear.
Origin: midbrain and medulla oblongata
42. Component: Motor
Function: Lateral rectus muscle turns
eyeball laterally
Origin: Medulla oblongata
Opening to the skull: Superior orbital
fissure
ABDUCENT NERVE
43. Component: Mixed
Function:
Muscles of the face and scalp
Stapedius muscle
Posterior belly of diagastric
Origin: Medulla oblongata
Opening to the skull: Interior acoustic
meatus, facial canal, stylomastoid
foramen
FACIAL NERVE
44. Component: Sensory
Function:
Vestibular – Saculae, saccule,
semicircular canals – positions of
head
Cochlear – Organ of Corti - hearing
Origin: Medulla oblongata
Opening to the skull: Interior acoustic
meatus
VESTIBULOCOVHLEAR NERVE
45. Component: Mixed
Function:
Motor: Assists swallowing
Sensory: Taste, tongue and pharynx
Origin: Medulla oblongata
Opening to the skull: Jugular foramen
GLOSSOPHARYNEGEAL NERVE
46. Component: Motor
Function:
Heart and great thoracic blood vessels
Larynx, trachea, bronchi and lungs
Alimentary tract from pharynx to
splenic flexure of colon
Liver, kidney, pancreas
Origin: Medulla oblongata
Opening to the skull: Jugular foramen
VAGUS NERVE
47. Component: Motor
Function:
Cranial root
Muscles of soft palate
Muscles of pharynx
Muscles of larynx
Spinal root
Sternocleidomastoid and trapezius
muscle
Origin: Medulla oblongata
Opening to the skull: Jugular foramen
ACCESSORY NERVE
48. Component: Motor
Function: Muscle of tongue
Origin: Medulla oblongata
Opening to the skull: Hypoglossal canal
HYPOGLOSSAL NERVE
54. Summary of parasympathetic neurons and
synapses
• Preganglionic neurons
• Long
• Synapse with postganglionic
• neurons at or near organ
• Release acetylcholine (ACH) to activate
nicotinic receptors on postganglionic
neurons
• Postganglionic neurons
• Short
• Synapse on the target organ
• Release acetylcholine (ACH) to activate
muscarinic receptors on the target organ
Summary of sympatheticneurons and
synapses
• Preganglionic neurons
• Short
• Synapse with postganglionic
• neurons near spinal cord
• Release acetylcholine (ACH) to activate
nicotinic receptors on postganglionic
neurons
• Postganglionic neurons
• Long
• Synapse on the target organ
• Release norepinephrine to activate adrenergic
receptors on target organs
ANS SUMMARY