Nervous system.pdf

HUMAN ANATOMY AND PHYSIOLOGY NOTES
RAMDAS BHAT
KARAVALI COLLEGE OF PHARMACY 1
CHAPTER NO:10
NERVOUS SYSTEM
Prepared by,
RAMDAS BHAT
Asst. Professor
Karavali college of Pharmacy
Mangalore
7795772463
Ramdas21@gmail.com

RAMDAS BHAT
• NERVOUS SYSTEM is a part of the animal which controls and coordinates its actions by
the transmission of the impulses to and from various parts of the body
• Brain is held in the cranial cavity of skull and consist of Cerebrum, Cerebellum, medulla
oblongata and pons
• The nerves are formed by Cranial nerves and the spinal nerves
CELLS OF NERVOUS SYSTEM:
Neurons:
• These are structural and functional unit of the nervous system
• They contain the cell body dendrites and axons
• The impulses are taken up by the cell body and are transmitted to the other parts by the
axons containing telodendrions
Neuroglial cells:
• These cells are specialised connective tissue cells that does not convey impulses but
supports the neurons.

RAMDAS BHAT
TYPES OF NEURONS

RAMDAS BHAT
Neurotransmitters:
• These are the chemical messengers present in the body that help in the conveying of the
impulses from one part to another.
• They are present at the axonal terminal of the motor neurons and they stimulate the
muscle fibres.
ACETYLCHOLINE:
• They are the first neuro transmitter discovered and they stimulate the muscles fibres
including the GIT muscle.
• Other neurotransmitters include Norepinephrine, Dopamine, GABA, Glutamate,
serotonin, endorphin.
BRAIN:
• The Human brain is made of several divisions they are:
1. Brain stem
a) Medulla oblongata
b) Pons
c) Midbrain
2. Diencephalon
a) Hypothalamus
b) Thalamus
3. Cerebellum
4. Cerebrum

RAMDAS BHAT
CEREBRUM:
• Largest and the uppermost part of the brain
• They show the ridges called as the gyri and the grooves called as the sulci
• The deepest sulci are called the Fissure
• Falx Cerebri separates the cerebrum into 2 separate half or hemisphere that are
connected by the Corpus callosum
• The sulcus will divide the cerebral hemisphere into 4 different lobes and each lobe into
various convolutions.
• The various lobes are frontal, parietal, occipital and temporal.
• Cerebrum comprises of the outer cortex and inner medulla
• Cortex is made of the grey matter containing the nerve cell bodies and the dendrites that
gives the darker appearance to the region hence the name GREY.
• Inner medulla is made of the nerve fibres along with the myelin and shows the light
appearance hence the name White matter.
• Within the white matter there are the group of the cell body with the dendrites called as
BASAL GANGLIA that helps in the autonomic function and the postural balance.
• Cerebrum is divided into various lobes a) Frontal, b) Parietal, c) Occipital and d) Temporal
• There are various fissures in the cerebrum they are Central sulcus, Parieto-occipital sulcus,
Callosomarginal, Sylvian fissure (separates temporal with frontal and parietal)
• The main function of the Cerebrum is a) Sensory and b) Motor function

RAMDAS BHAT
• Motor functions are maintenance of the body balance, postural balance, special
movements, regulation of the muscle tone and control of the lower centres and also, they
contain the centres for speech, smell and control of eye movements.
• Sensory functions are sensation of touch, temp., pain, pressure, vibration and stereo
gnostic sensation and senses taste, smell, vision and hearing.
BASAL GANGLIA
• They are group of nuclei found in the grey matter
• They help in the coordination of the muscle tone and also, they help in the postural
balance
• Any lesion in the region can lead to the imbalance in the body

RAMDAS BHAT
LIMBIC SYSTEM:
• Their main role is in the maintaining the emotional changes and contain Septal area,
hypothalamus, amygdala, thalamus and a part of reticular formation
• They are involved in the emotional changes love, hate, envy(possessions), revenge,
selfishness and altruism (lack of interest)
• They act as a biological clock that are concerned with the diurnal variation.
• They help in the emotional homeostasis.
THALAMUS:
• Part of the forebrain present below the corpus callosum
• They are oval mass of grey matter.
• They help as the relay station for the sensory areas to the proper areas of the brain
• They help in the transmission of the sensory impulses towards the various centres of the
brain
• The sensory impulses such as the audition, tactile, gustatory, visual are transmitted from
the respective organ towards the brain.

RAMDAS BHAT
HYPOTHALAMUS:
• They are part of the forebrain that are located just below the thalamus hence the name
hypothalamus
• They act as the main centre foe muscle coordination of the visceral muscle activity
• They have various centres such as sleep centre, they help in the control of the emotional
changes, help in regulation of the body temperature
• They act as the centres for the control of release of the hormones, also control the ANS
activity
• Control of hunger, feeling, thirst, appetite
• Control GA secretion, sexual behaviour.
RETICULAR FORMATION:
• They are diffused undefined mass of the nerve cells that passes through the upper
portion of the spinal cord, brain and diencephalon (thalamus and hypothalamus)
• Main activity is the muscle coordination and muscle activity.
MIDBRAIN:
• They are the structure that connects pons to the cerebellum.
• They provide the conduction pathway to the impulses from the higher to the lower
centres.
• It contains tectum, tegmentum, crus cerebri, substantia nigra and red nucleus

RAMDAS BHAT
CEREBELLUM:
• Biggest part of the hind brain located behind the pons and medulla
• Weighs about 150 g in adult
• They are not involved in any perception of sensation or consciousness and their removal
does not cause any impairment
• They play important role in the maintenance of the equilibrium and maintenance of the
body posture and the reflex regulation of the tone
• They play and important role in the coordination of the skeletal muscle contraction.
• It acts as a link btwn the cerebral cortex and PNS.
• Any lesions in them can lead to postural defects.

RAMDAS BHAT
MEDULLA OBLANGATA AND PONS:
• They are part of the brain stem and connects the brain to the spinal cord
• Pons are the rounded part [present btwn the medulla and mid brain
• They help in the maintenance of the rhythm of the respiration.
• Medulla is present below to the pons and act as the main centre for control of CVS
activity, control of respiration (inspiratory and expiratory centres), reflexes such as
coughing, sneezing, swallowing, salivation, sucking, vomiting (CTZ).
SPINAL CORD:
• Long cylindrical structure
• Located in the vertebral column extends up to the 1-2nd lumbar vertebrae and branches
they are called cauda equina.
• 46cm(l)
• The structure of the spinal cord shows the central canal that are surrounded by the mass
of grey matter
• The grey matter contains horns on the anterior and the posterior side
• The horn on the anterior side is called as the ventral horn which is wide and is connected
to the anterior root / ventral root
• The horn present in the posterior side is called as the Dorsal horn and is connected to
the dorsal root
• The grey matter is surrounded with the mass of the white matter that contains more
prominent anterior median sulcus and less prominent posterior median septum these
are inward projection that are seen white matter
• The white matter also contains 3 surfaces anterior funiculus, posterior funiculus and
lateral funiculus.
• The nerve fibres passing in the anterior root is motor in function and in the posterior
root is sensory in function.
• Dorsal horn contains a bulged part which contains ganglion

RAMDAS BHAT
• Spinal cord passes through the various segments of the spinal cord i.e., it starts from the
1st cervical and ends up to the L2 where it branches i.e., Filum terminal (cauda equina)
FUNCTIONS:
• Conduction of the sensory impulses through the ascending tracts to the brain
• Conduction of the motor impulses from down the brain through the descending tracts to
the efferent neurons supplied to the MUSCLES/ GLANDS
• it is helpful in the reflex activity as it is autonomic in nature.
MENINGES:
• These are the protective layer that are present inside the skull and surrounds the brain
and spinal cord
• It has 3 layers i.e., Dura mater, Arachnoid mater and Pia mater.
• Pia mater is closely associated with the brain and spinal cord and is very delicate in
nature and highly vascularised and will drip down in the fissures of the brain

RAMDAS BHAT
• Arachnoidal mater is a delicate layer that are present btwn the Pia and dura mater that
extends upto IInd sacral vertebrae made of epithelial tissue and space between ach.
Mater and pia mater is called as sub arachnoidal space, CSF fills this space
• Dura mater is outer tough fibrous membrane extends upto S-2 ver. They are closely
associated with the skull, the space between the dura mater and arachnoid mater is
called as the SUB DURAL SPACE
VENTRICLES OF BRAIN:
• Ventricles are hollow cavities in the brain where the CSF gets pass and baths the brain
• They are of 3 types
• Lateral ventricles: present in the cerebrum that are present below the choroid plexus,
the connected to the 3rd ventricle by interventricular foramen
• 3rd ventricle presents in the thalamus and is connected to the 4th ventricle with the
cerebral aqueduct
• 4th ventricle lies in front of cerebellum behind the medulla and pons, continuous with
the central canal of the spinal cord.

RAMDAS BHAT
CEREBRO-SPINAL FLUID
• Modifies tissue fluid present in the sub arachnoidal space produced from Choroid
plexus.
• 150ml produced in adult
• Clear, colourless, watery produced by blood vessels of the choroid plexus
• 40-60mg% glucose, protiens, nitrogenous substances, electrolytes like sodium,
potassium, calcium, chlorides and bicarbonates
• Provides shock absorbance effect, baths brain and spinal cord
• Provides nutrition to brain and removes waste from brain and spinal cord
• Prevents brain and spinal cord from infection and acts as buffer
REFLEX ACTIVITY:
• Reflex activity is an autonomic response to a external stimuli.
• They will be dependent on the integrity of the reflex pathway.
• Reflex arc consists of the Afferent neurons, Afferent neurons, Receptor and the Effector
Organ.
• The reflexes are mainly dependent on the number of the synapse formed between
Afferent and Efferent neurons.
• So, they are classified as a) Monosynaptic b) Polysynaptic reflexes.
MONOSYNAPTIC REFLEX:
• There is single synapse will be found in between the afferent and efferent neurons.
• The monosynaptic reflex is also called as the stretching reflex.
• The example for the Monosynaptic reflex is the stretching reflex where the patellar
tendon is hit with the patellar hammer there will be knee jerking movement along with
the stretching of the leg.
• The legs are supplied with the muscle spindle which are supplied with the afferent
neurons.
• When the patellar tendon which is hit with the patellar hammer there will be
contraction of the quadriceps muscle of the leg which is followed with the Relaxation of
the Hamstring. Here hamstring is a flexor muscle which will act as a antagonist.
• Hamstring will be inhibited.

RAMDAS BHAT
• The afferent neurons present in the muscle spindle of the quadriceps will carry the
impulse to the spinal cord and the efferent neuron will carry the impulses back to the
effector muscle.
POLYSYNAPTIC REFLEX:
• Such reflexes are seen under the presence of the noxious stimuli or painful stimuli.
• It is also called as the withdrawal reflex.
• It is a complex process and there are presence of more than one synapse in between the
afferent and efferent neurons and as a result complex branches are formed.
• Ex: When a finger comes in contact with the hot surface the hand will be withdrawn with
a big jerk.
• This is because the receptor cell present in the skin of the hand will perceive the
stimulus and are relayed to spinal cord by the sensory neurons.
• The response is sent back to the particular muscle through the motor neurons or
efferent neurons.
• The mechanism involves the contraction of the flexor group of the muscles. As a result
the limb gets flexed away from the stimuli. This is called as the Flexor Reflex or Flexor
Response.
• In the presence of the stronger stimuli the flexor reflex is seen along with the extensor
of the opposite limb. This is called as the CROSSED EXTENSOR REFLEX.
• The impulses are later taken to the brain that helps in realizing what had happened.

RAMDAS BHAT
SPINAL NERVES:
• They arise from the spinal cord
• They are of 31 pairs
• Ie 8 cervical, 12 thoracic, 5 lumbar, 5 sacral, 1 coccygeal nerve
• Each spinal nerve arising from the spinal cord has 2 roots
• Ventral is motor in function whereas the dorsal is sensory in function
• The dorsal root has the ganglion called as the dorsal root ganglion

RAMDAS BHAT
• C1-C5 are cervical plexus, C6-T1 are brachial plexus, L1-L5 are lumbar plexus, S1-S5 sacral
plexus
CRANIAL NERVE:
• CRANIAL NERVES are the nerves that are attached to the brain
• They are of 12 pairs
• They are numbered according to their connection with the brain
SPINAL NERVE LOCATION
RADIAL NERVE C5-C8, T1(BRACHIAL PLEXUS)
MEDIAN NERVE C5-C8, T1(BRACHIAL PLEXUS)
ULNAR NERVE C8, T1(BRACHIAL PLEXUS)
INTERCOSTAL NERVE T1-T11
PHRENIC NERVE C3-C5
FEMORAL NERVE L2-L4(LUMBAR PLEXUS)
SCIATIC NERVE L4-S3(LUMBOSACRAL PLEXUS)

RAMDAS BHAT
INTRODUCTION OF AUTONOMIC NERVOUS SYSTEM (ANS):
It is the part of nervous system that deals with the involuntary movements. It is also known
as visceral nervous systems. It works under the conscious and unconscious conditions and
maintain the involuntary functions. It controls automatically, pumping of blood, beating of
heart, contraction of blood vessel, lungs and GI tract, secretion of saliva, lacrimal fluid etc.

RAMDAS BHAT
Anatomy of Autonomic Nervous System (ANS):
Hypothalamus
Coordinate with Midbrain/Spinal Cord
Stimulate Preganglionic Neuron/Fiber
Release Neurotransmitter – I at Autonomic Ganglion
Stimulate Postganglionic Neuron/Fiber
Release Neurotransmitter – II at Neuron Effector Junction
It stimulates various receptors of respective organs
Produce various autonomic action
▪ In the brain, hypothalamus mainly regulate the autonomic functions of the body.
Hypothalamus coordinate with the midbrain and spinal cord for autonomic function.
▪ From the midbrain and spinal cord, some nerves fibers are emerged out which is called
as preganglionic neurons or preganglionic fibers.
▪ At the end of preganglionic neuron/fiber, post ganglionic neurons/fibers start.
▪ The gap between the end of preganglionic neurons and starting portion of post ganglionic
neurons is known as junction-I, which is known as autonomic ganglion/autonomic
junction.
▪ Post ganglionic neurons end near to the different organ/tissue/cell, and the end portion
of post ganglionic neurons near to the different organ/tissue/cell form junction-II which
is known as neuron effector junctions.
▪ Autonomic ganglion (Junction-I) and neuron effector junction (Junction-II), in their gap
consist neurotransmitter that stimulate the various respective receptors and gives
different kind of autonomic functions.
Autonomic nervous system is subdivided into the two portions:
1. Parasympathetic Nervous System (Cholinergic Nervous System)
2. Sympathetic Nervous Systems (Adrenergic Nervous System)

RAMDAS BHAT
PARASYMPATHETIC DIVISION:
▪ Their cell body are present in brain and in sacral region of the spinal cord(S2-S4)
▪ Hence, they are called as the CRANIO-SACRAL DIVISION.
▪ Here the ganglion will be present closer to the effector region.
CRANIAL OUTFLOW:
▪ They are having 4 different types of Cranial nerves
They are:
1. OCCULOMOTOR NERVE (IIIrd Cranial nerve)
2. FACIAL NERVE (VIIth Cranial nerve)
3. GLOSSOPHARYNGEAL NERVE (IXth Cranial nerve)
4. VAGUS NERVE (Xth Cranial nerve)
▪ Nerve supply to head: They contain III, VII, IX nerve.
▪ Nerve supply to the Thorax and Abdomen.
▪ SACRAL OUTFLOW: They are having S2-S4 nerves and are innervated to Lower abdomen
and genitals.

RAMDAS BHAT
SYMPATHETIC DIVISION:
• They are also called as the THORACO-LUMBAR DIVISION. As they lie in the spinal cord of
T1-L3 segment.
• Here the cell body of the Preganglionic nerve fibres are present in Intermediolateral horn
of the spinal cord.
• The axons of the preganglionic nerve fibers will come out of the spinal cord through
vertebral foramina.
• The fibers will now synapse to the PARAVEREBRAL GANGLION which lie closer to the spinal
cord.
• The paravertebral ganglion will now branch further to form ganglions.
• The ganglions will now form the synapse with Post ganglionic nerve fiber this will have
their cell body in the Visceral Organs.

RAMDAS BHAT

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