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Basic concept of nervous system
1. Basic Concept of Nervous
System
Aditya Johan Romadhon, SST.Ft, M.Fis
2. Introduction
Spinal nerves carry impulses to and from the spinal cord, and cranial nerves carry impulses to and from the brain
The PNS consists mainly of nerves (bundles of axons) that extend from the brain and spinal cord, and ganglia (collections of neuron cell
bodies)
The peripheral nervous system (PNS) is the part of the nervous system outside the CNS
The central nervous system (CNS) consists of the brain and spinal cord, It interprets sensory input and dictates motor output based on
reflexes, current conditions, and past experience
We have one highly integrated nervous system. For convenience, it is divided into two principal parts, Central Nervous System (CNS)
and Peripheral Nervous System (PNS)
Every thought, action, and emotion reflects its activity of cells communicate by electrical and chemical signals, which are rapid and
specific, and usually cause almost immediate responses
The nervous system is the master controlling and communicating system of the body
4. Basic function of nerve system
The nervous system has
three overlapping
functions
Sensory input, the nervous
system uses its millions of
sensory receptors to
monitor changes occurring
both inside and outside the
body
Integration, the nervous
system processes and
interprets sensory input
and decides what should be
done at each moment
Motor output, the nervous
system activates effector
organs the muscles and
glands to cause a response
5. Brain development
The brain and spinal cord begin as an
embryonic structure called the neural tube
As soon as the neural tube forms, its anterior
(rostral) end begins to expand and constrictions
appear that mark off the three primary brain
vesicles
6. Pattern distribution of grey & white matter
• Gray and white matter have a unique distribution in the brain
• The gray matter of the CNS consists of short, nonmyelinated neurons and neuron cell
bodies
• The white matter is composed of myelinated and nonmyelinated axons.
7. Basic region of hemisphere
Each of the cerebral hemispheres has three basic
regions
A superficial cerebral cortex of gray matter, which
looks gray in fresh brain tissue, the cerebral cortex
contains three kinds of functional areas: motor areas,
sensory areas, and association areas
Internal white matter, the white matter deep to the
cortical gray matter is responsible for communication
between cerebral areas and between the cerebral
cortex and lower CNS centers (association,
commissural, projection)
Basal nuclei, islands of gray matter situated deep
within the white matter
9. Brainstem
Positioned between
the cerebrum and the
spinal cord, the brain
stem also provides a
pathway for fiber
tracts running
between higher and
lower neural centers
Brain stem centers
produce the rigidly
programmed,
automatic behaviors
necessary for survival
The brain stem has
nuclei of gray matter
embedded in the
white matter, a
feature not found in
the spinal cord.
From superior to
inferior, the brain
stem regions are
midbrain, pons, and
medulla oblongata
10. Cerebellum
The cerebellum is located dorsal to the pons and medulla (and to the intervening
fourth ventricle), it protrudes under the occipital lobes of the cerebral
hemispheres
By processing inputs received from the cerebral motor cortex, various brain
stem nuclei, and sensory receptors from sinal cord
The cerebellum provides the precise timing and appropriate patterns of
skeletal muscle contraction for smooth, coordinated movements and agility
needed for our daily living, cerebellar activity occurs subconsciously
Deep fissures subdivide each hemisphere into anterior (muscle tone),
posterior (coordinated), and flocculonodular lobes (balance)
11. Spinal cord
The spinal cord is about the
width of a thumb for most of its
length, but it has obvious
enlargements where the nerves
serving the upper and lower
limbs arise, these enlargements
are the cervical and lumbar
enlargements
In humans, 31 pairs of spinal
nerves part of the peripheral
nervous system
Each nerve exits from the
vertebral column by passing
superior to its corresponding
vertebra via the intervertebral
foramen, and travels to the body
region it serves
In cross section the gray matter
of the cord looks like the letter H
or like a butterfly
The two dorsal projections of the
gray matter are the dorsal
(posterior) horns, and the
ventral pair are the ventral
(anterior) horns
The thoracic and superior
lumbar segments of the cord
have an additional pair of gray
matter columns, the small
lateral horns
12. The ventral horns have some
interneurons but mainly house
cell bodies of somatic motor
neurons
These motor neurons send their
axons out to the skeletal muscles
(their effector organs) via the
ventral rootlets that fuse together
to become the ventral roots of the
spinal cord
The lateral horns consist mostly of
the cell bodies of autonomic
(sympathetic division) motor
neurons that serve visceral organs.
Their axons leave the cord via the
ventral root along with those of
the somatic motor neurons
Afferent fibers carrying impulses
from peripheral sensory receptors
form the dorsal roots of the spinal
cord that fan out as the dorsal
rootlets before they enter the
spinal cord
13. Hierarchy of motor control
The cerebral cortex is at the highest level
of our conscious motor pathways, but it
is not the ultimate planner and
coordinator of complex motor activities
The cerebellum and basal nuclei
(ganglia) play this role and are therefore
at the top of the motor control hierarchy
Motor control exerted by lower levels is
mediated by reflex arcs in some cases
Three levels of motor control: the
segmental level, projection level, and
precommand level
