This presentation was prepared for the GNM 1st year students with objectives: they will be able to: 1. define nervous system 2. describe neurones 3. explain different parts of brain and their function 4. list down types of nerves and their functions 5. differentiate between sympathetic and parasympathetic nervous system.

1. Nervous system

2. • The nervous system
– It is an organ system containing a network of
specialized cells called NEURONS that coordinate
the action and transmit signals between different
parts of body.

4. • Functions of nervous system
– Orientation to and perception of the ever
changing internal and external environment
– Activation, control and co-ordination of all the
other body part
– Intelligence – conceptual thoughts:
• Highly intellectual function:
– Imagination, abstract, reasoning, creativity, predictions,
calculation and control of violence
– Exhibition of capacity of the nervous system to RECORD,
PROCESS, STORE and RELATE IMFORMATION RECEIVED and
ACTION taken for the experience and use it for future reaction
to environment change or situation

5. CELLS AND TISSUES OF THE
NERVOUS SYSTEM

8. Properties of neuron
• The neurons are working
units of the nervous
system that generate and
transmit nerve impulses.
• 100 billion neurons in the
brain
• Each neuron consists of:
– Cell body
– Axon and dendrite

9. • Conductivity (transmit
impulse)
• Excitability (initiate
impulse)
• Stimulus
– Mechanical
– Electrical
– Chemical

10. • Cell body:
– Present at periphery in
the brain and in the
centre of the spinal cord
– Nuclei – in the CNS
– Ganglia – in the PNS

11. • Axon and dendrite:
– Are the branches which
extend from a tapered
portion of the cell body
– A neuron has only ONE
axon, 100 cm long thin
cylindrical projections,
– Axon are found deep in
brain and in periphery in
spinal cord
– Nerve fibres: is a term used
for neuron process (axon
and dendrite)

13. They are not
myelinated

14. • The nerve impulse or action potential
– Action potentials are electrochemical pulses that
transmit information along nerves.
– An action potential is a temporary change in electrical
potential of a neural cell membrane (the voltage
between the interior of the cell and the exterior) from
the resting potential.
– It involves a series of electrical and underlying
chemical changes that travel down the length of a
neuron.
– An action potential is a controlled, temporary shift in
the concentrations of charged molecules in the cell
that sweeps rapidly down a long, fiber-like projection
(axon).
Action potential - Dictionary definition of Action potential | Encyclopedia.com:
FREE online dictionary

16. Synapses and neurotransmitters
• Synapses:
– a junction between
two nerve cells,
consisting of a
minute gap across
which impulses pass
by diffusion of a
neurotransmitter.

17. Neurotransmitter
• A chemical substance which is
released at the end of a nerve
fibre by the arrival of a nerve
impulse and, by diffusing across
the synapse or junction, effects
the transfer of the impulse to
another nerve fibre, a muscle
fibre, or some other structure.
• They maintain signals in the
nervous system by binding to
receptors on post-
synaptic neurons and triggering
electrical impulses
• They also activate responses by
effector organs (such as
contraction in muscles or
hormone release from endocrine
glands)

19. Types of neurotransmitters
• Adrenaline
– Adrenaline is primarily a hormone released by the adrenal gland, but some
neurons may secrete it as a neurotransmitter
– It increases heart rate and blood flow, leading to a physical boost and
heightened awareness
– It is produced during stressful or exciting situations
• Noradrenaline
– In contrast to adrenaline, noradrenaline is predominantly a
neurotransmitter that is occasionally released as a hormone
– It contracts blood vessels and increases blood flow, improving attention
and the speed at which responsive actions occur
• Dopamine
– It is primarily responsible for feelings of pleasure, but is also involved in
movement and motivation
– People tend to repeat behaviours that lead to dopamine release, leading to
addictions
– Abnormal dopamine secretion is common in specific movement disorders,
like Parkinson’s disease

20. • Serotonin
– Contributes to feelings of well-being and happiness
– Is affected by exercise and light exposure, and plays a role
in the sleep cycle and digestive system regulation
• GABA
– Inhibits neuron firing in the CNS – high levels improve
focus whereas low levels cause anxiety
– Also contributes to motor control and vision
• Acetylcholine
– Involved in thought, learning and memory within the brain
– Activates muscle contraction in the body and is also
associated with attention and awakening
•

21. • Glutamate
– Most common brain neurotransmitter
– Regulates development and creation of new nerve
pathways and hence is involved in learning and
memory
• Endorphins
– Release is associated with feelings of euphoria and a
reduction in pain (body’s natural 'pain killers’)
– Released during exercise, excitement and sex
•

23. • Sensory nerves / afferent nerve:
– Transmit sensory impulses from receptors in the skin,
sense organ, muscles, joints and viscera into the CNS
• Somatic cutaneous – pain, temperature, touch, vibrations, etc
• Special senses: of tases,smell
• Proprioceptor senses: vision, hearing and balance via cranial
nerves
• Motor / efferent nerve:
– Convey nerve impulses from CNS to effectors (muscles or
glands)
– Two types:
• Somatic nerves- skeletal muscles contraction
• Autonomic nerves (parasympathetic and sympathetic):
contraction of smooth muscles, cardiac muscles, glands via cranial
and spinal nerves
• Mixed nerve:
– out side the spinal cord, enclosed in same sheath.

24. • NEUROGLIA:
– Also known as glial cells
or glia means glue are
non-neuronal cells in the
CNS and the PNS.
– They act as glue to the
neurons
– They maintain
homeostasis, form
myelin, and provide
support and protection
for neurons.

25. • Functions of neuroglia
– Form myelin which wrap
around axon to speed
up electric impulse
– Provide nutrients to
neurons, including
oxygen
– Destroy pathogens
– provide a general
support structure on
which neurons can sit

26. • Types of neuroglia
– Astrocytes
– Oligodendrocytes
– Ependymal cells
– Microglia

27. • Astrocytes: (CNS)
– Astro means star, cytes
means cells- star shaped cells
– Form the part of blood brain
barrier (helps to prevent
undesirable substances from
entering the brain via blood
vessels)
– Provide nutrients
– Structural support
– Release and absorption of
ions and neurotransmitters
for improved modulation of
cell to cell communication
between neuron
– They maintain the proper
balance of K+ ion for
generation of nerve impulses
– Repair of the neurons

28. • Oligodendrocytes
(CNS):
– Creates myelin sheaths
around the axons
neurons.
– These myelin sheaths
allows for action
potentials to travel down
the axon

29. • Microglia (CNS):
– Smallest of glial cells
– Derived from monocytes
(macrophages or WBC)
– Phagocytic in nature and
protect the CNS from
disease by engulfing,
invading microbes
– Clear away debris from
dead cells
– Help to reduce
inflammation through
release of anti
inflammatory chemical
signals

30. • Ependymal cells:
– Specialized cells that line
the cerebral ventricles
and central canal of the
spinal cord
– Funtions:
• CSF production
• Nutrient provision for
neurons
• Filtration of harmful
substances
• Neurotransmitter
distribution
Ependymal cells

31. • Swachnn cells (PNS):
– Are wrapped around
some neuronal axons to
form the myelin sheath
in PNS
– Help to improve nerve
signal conduction
– Assist in nerve
regeneration and nerve
repair
– Antigen recognition by T
cells

32. • Satellite glial cells:
– Covers the surface of the
nerve cell bodies in
sensory, sympathetic
and parasympathetic
glaglia
– Act as a protective
cushion sheath
– Supply nutrients to
neurons
– Link to neurochemical
– Similar role to astrocytes

33. NERVOUS SYSTEM
CENTRAL NERVOUS SYSTEM PEIPHERAL NERVOUS SYSTEM
AFFERENT NERVOUS
SYSTEM (SENSORY)
EFFERENT NERVOUS
SYSTEM (MOTOR)
SOMATIC NERVOUS SYSTEM AUTONOMIC NERCOUS SYSTEM
SYMPATHETIC NERVOUS
SYSTMEM
PARASYMPATHETIC NERVOUS
SYSTEM
BRAIN SPINAL CORD

35. Central nervous system
Brain
Spinal
cord

39. • Ventricles:
– The irregular cavities inside the brain which
produces and maintains CSF
– There are four types of ventricles
• Left and right ventricle
• 3rd ventricles
• 4th ventricles

44. • Mechanism of csf formation
– Plasma is passively filtered across the choroidal
capillary endothelium
– Secretion of water and ions across the choroidal
epithelium
• Bicarbonate, chloride, and potassium ions, enter the
CSF via channels in the epithelial cellaical membranes
• Aquaporins provide for water movement to blance
osmotic gradients

50. • THE BRAIN
– Brain is a large organ weighing 1.4 kg. it lies within
the cranial cavity.
– The portion of the central nervous system that is
located within the skull. It functions as a primary
receiver, organizer, and distributor of information
for the body. It has a right half and a left half, each
of which is called a hemisphere.

51. • Parts of brain:
– Fore brain (procencephalon)
• Olfactory lobe
• Cerebrum
– Cerebral cortex (grey mater – cell body)
– Medulla (white mater - axon )
• Diencephalon
– Epithalamus
– Thalamus
– Hypothalamus
– Mid brain (Mecencepahalon)
• Tectum
– Superior coliculus
– Inferior coliculus
• Tegmentum
– Hind brain – cerebellum
• Pons BRAIN STEM
• Medulla oblongata

53. • Fore brain
1. Olfactory lobe –
covered by cerebral
hemisphere
– Olfactory bulb (A)
– Olfactory tract (B)
• One pair
• Solid small structure
• Connected to
olfactory region of
temporal lobe
• Detection of smell

54. • Olfactory lobe Either
member of a pair
of lobes in the forebrain,
at the anterior end of the
cerebrum. They contain
the endings of
the olfactory nerves (the
first pair of cranial
nerves) and are
concerned with the
sense of smell

57. • Function of the cerebral cortex:
– Higher order functions: the mental activities
involved in memory, sense of responsibilities
– Sensory perception, including the perception of
pain, temperature, touch, sight, hearing, taste,
and smell
– Initiation and control of skeletal muscle
contraction and therefore voluntary movement

58. • Corpus collusum
– The corpus callosum is a
thick band
of nerve fibers that
divides the cerebral
cortex lobes into left and
right hemispheres. It
connects the left and
right sides of the brain
allowing for
communication between
both hemispheres.
– The corpus callosum
transfers motor, sensory,
and cognitive
information between the
brain hemispheres.

59. • Corpus Callosum Function
– The corpus callosum is the
largest fiber bundle in the
brain, containing nearly
200 million axons. It is
composed of white
matter fiber tracts known
as commissural fibers. It is
involved in several
functions of the body
including:
– Communication Between
Brain Hemispheres
– Eye Movement and Vision
– Maintaining the Balance of
Arousal and Attention
– Tactile Localization

60. • Lobes of the
cerebrum

62. • Functional areas of the cerebral cortex
–Motor area
–Sensory area
–Association areas

63. Motor area
Area Location Function
Primary motor area Frontal lobe
immediately anterior to
the central sulcus
Control skeletal muscles
activity
Motor speech (broca’s
area)
Frontal lobe just above
the lateral sulcus
Muscle movements
needed for speech

64. Sensory area
Area Location Funtion
Somatosensory area Immediately behind the
centralsulcus
pain, temperature,
pressure and touch,
awareness of muscular
movement and the
position of joints are
percieved.
Auditory area Immediately below the
lateral sulcus
Hearing
Olfactory area Deep within the temporal
loe
Smell
Taste area Lateral sulcus in the deep
layers of the
somatosensory area
Taste
Visual area Behind the parieto-
occipital sulcus
Vision

65. Associated areas
Area Location Function
Premotor area Frontal lobe immedeately
anterior to the motor area
Coordinate movement eg
tying a lace or writing –
manual dexterity
Prefrontal area Extrends anteriorly from the
premotor area to include the
remainder of the frontal area
Intellectual functions –
perception and
comprehension of the
passage of time, the avbility
to anticipate consequences
of the events and
management of emotion
Sensory speech (wernicke’s)
area
Temporal lobe adjacent to
the parieto-occipitotemporal
area
Spoken words are perceived,
and comprehension and
intelligence are based,
language based,
Perieto-occipitotemporal
area
Behind the somatosensory
area
Spatial awareness,
interpretation of written
language and the ability to
name objects

68. Blood supply to the brain

70. • Circulus arteriosus play a vital role in
maintaining a constant supply of oxygen and
glucose the brain
• The brain receives about 15% of the cardiac
output (750 ml) of blood per min

71. Venous drainage of the brain

73. • Diencephalon
– Connects the
cereburm and the
midbrain
– Consists of :
• Thalamus
• hypothalamus

74. Sensory receptors in the skin and viscera
send information about touch, pain and
temperature and inputs from the special
sense organs travel to the thalamus where
there is recognition and relays information to
the brain

75. Pneumonic for cranial nerves
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