- The nervous system is divided into the central nervous system (CNS), which includes the brain and spinal cord, and the peripheral nervous system (PNS), which includes nerves outside the CNS. - Neurons are the basic functional units of the nervous system and transmit electrochemical signals. A neuron has a cell body, dendrites that receive signals, and an axon that transmits signals to other neurons or effector cells. - The PNS is further divided into the somatic and autonomic systems. The somatic system controls skeletal muscles and senses the external environment. The autonomic system regulates involuntary functions through the sympathetic and parasympathetic divisions.

1. The Nervous System
Andrea Audine P. Jandongan
Aleona Grace C. Puno
MPE - 1

2.  General functions
 Organization
 Sensory information & Reflexes
 Somatic Motor Neurons
 Vestibular Apparatus & Equilibrium
 Motor control functions of the Brain
 Motor functions of the Spinal Cord
 Control of motor functions
 Autonomic Nervous System

3. The nervous system provides the
body with a rapid means of internal
communication that allows us to move
about, talk, and coordinate the activity
of billions of cells. Thus, neural activity
is critically important in the body’s
ability to maintain homeostasis.

4. General Nervous System Functions
The nervous system is the body’s means of
perceiving and responding to events in the
internal and external environments. Receptors
capable of sensing touch, pain, temperature
changes, and chemical stimuli in several ways.
The nervous system is also responsible for
storing experiences (memory) and establishing
patterns of response based on previous
experiences (learning).

5. Summary of the functions of
the Nervous System
• Control of the internal environment (nervous
system works with endocrine system)
• Voluntary control of movement
• Programming of spinal cord reflexes
• Assimilation of experiences necessary for
memory or learning

6. Organization of the Nervous System
Nervous System
Central Nervous System (CNS)
Peripheral Nervous System (PNS)
Brain Spinal Cord
Sensory Motor

7. Organization of the Nervous System
Nervous System
Central Nervous System (CNS)
Peripheral Nervous System (PNS)
Brain Spinal Cord
Sensory Motor
 Responsible for transmission of neuron
impulses from sense organs (receptors) to
the CNS. These sensory fibers, which
conduct information toward the CNS, are
called afferent fibers.

8. Organization of the Nervous System
Nervous System
Central Nervous System (CNS)
Peripheral Nervous System (PNS)
Brain Spinal Cord
Sensory Motor
 Motor nerve fibers that conduct impulses
away from the CNS, are referred to as
efferent fibers.

9. Organization of the Nervous System
Nervous System
Central Nervous System (CNS)
Peripheral Nervous System (PNS)
Brain Spinal Cord
Sensory Motor
Somatic Autonomic

10. Organization of the Nervous System
Nervous System
Central Nervous System (CNS)
Peripheral Nervous System (PNS)
Brain Spinal Cord
Sensory Motor
Somatic
(which innervates skeletal muscle)

11. Organization of the Nervous System
Nervous System
Central Nervous System (CNS)
Peripheral Nervous System (PNS)
Brain Spinal Cord
Sensory Motor
Somatic Autonomic
(which innervates involuntary effector
organs like smooth muscle in the gut,
cardiac muscle, and glands)

12. Organization of the Nervous System
Nervous System
Central Nervous System (CNS)
Peripheral Nervous System (PNS)
Brain Spinal Cord
Sensory Motor
Somatic
Autonomic
Sympathetic
Parasympathetic

13.  The nervous system is the body’s means
of perceiving and responding to events in
the internal and external environments.
Receptors capable of sensing touch, pain,
temperature, and chemical stimuli send
information to the CNS concerning
changes in our environment.

14.  The nervous system is divided into
two major divisions: (1) the central
nervous system and (2) peripheral
nervous system. The central nervous
system includes the brain and the spinal
cord, whereas the peripheral nervous
system includes the nerves outside the
central nervous system.

15. Structure of the Neuron
The functional unit of the nervous
system is the neuron. Anatomically, neurons
can be divided into three regions: (1) cell
body, (2) dendrites, and (3) axon. The
center of operation for the neuron is the cell
body, or soma, which contains the nucleus.
Narrow, cytoplasmic attachments extend
from the cell body and are called dendrites.

16. Dendrites serve as a receptive area that can
conduct electrical impulses toward the cell body.
The axon (also called the nerve fiber) carries the
electrical message away from thee cell body
toward another neuron or effector organ. Each
neuron has only one axon; however, the axon can
divide into several collateral branches that
terminate at other neurons; muscle cells, or
glands. Contact points between an axon of one
neuron and the dendrite of another neuron are
called synapses.

17. Electrical Activity in Neurons
Neurons are considered “excitable
tissue” because of their specialized
properties of irritability and conductivity.
Irritability is the ability of the dendrites and
neuron cell body to respond to a stimulus
and convert it to a neural impulse.
Conductivity refers to the transmission of
the impulse along the axon.

18. The Central Nervous System
and the Neurons

19. Summary
• The nervous system is an organ system containing a
network of specialized cells called neurons that coordinate
actions and transmit signals between different parts of the
body.
• The spinal cord and the brain make up the CNS. Its main
job is to get the information from the body and send out
instructions. The PNS is made up of all the nerves which
transmit the messages from the brain to the rest of the
body. The PNS connects the CNS to sensory organs.
• Neurons are the formation-processing units of the brain
responsible for receiving and transmitting information.

20. • A neuron has three basic parts, the cell body or
soma, the axon, and the dendrites. The cell body
contains a well-defined nucleus surrounded by a
granular cytoplasm. The cell body is also known as
perikaryon or cyton.
• Dendrites are branched cytoplasm projections of
the cell body. They are for receiving impulses, from
the axon of another neuron.

21. The Peripheral Nervous System

22. Summary
• The peripheral nervous system is the channel for the
relay of sensory and motor impulses between the central
nervous system on one hand and the body surface,
skeletal muscles, and internal organs on the other hand.
• Neurons which carry information from the body to the
CNS are called sensory neurons whereas neurons which
carry information from the CNS to the rest of the body
are called motor neurons.
• The cell bodies of peripheral neurons are often found
grouped into clusters called ganglia.

23. • The somatic nervous system is composed of spinal
nerves and cranial nerves. The cranial nerves are the
ones that exit from the brain and the spinal nerves are
the ones that exit from the spinal cord.
• The somatic nervous system controls skeletal muscles
as well as external sensory organs such as the skin. This
system is said to be voluntary.
• The autonomic system is the part of the PNS
responsible for regulating involuntary body functions
such as blood flow, heartbeat, digestion and breathing.

24. • Involuntary actions are controlled by antagonistic
actions of the two divisions of the autonomic nervous
system – the sympathetic and the parasympathetic
divisions.
• Stimulation from sympathetic nerves dilates the pupils,
accelerates the heartbeat, increases the breathing rate
and inhibits the digestive tract.
• The parasympathetic system returns the body
functions to normal after they have been altered by
sympathetic stimulation.

25. Sensory Information and Reflexes
The CNS receives a constant bombardment of
messages from receptors throughout the body about
changes in both the internal and external
environment. These receptors are “sense organs”
that “change” forms of energy in the “real world” into
the energy of nerve impulses, which are conducted
to the CNS by sensory neurons. Receptors that
provide the CNS with information about body
position are called proprioceptors, or kinesthetic
receptors.

26. Reflexes
A reflex arc is the nerve pathway from the
receptor to the CNS and from the CNS along a
motor pathway back to the effector organ. Reflex
contraction of skeletal muscles can occur in
response to sensory input, and is not dependent on
activation of higher brain centers. One purpose of
a reflex is to provide a rapid means of removing a
limb from a source of pain.

27. Example
Consider the case of a person touching a sharp
object. The obvious reaction to this painful stimulus
is to quickly remove the hand from the source of
pain. This rapid removal is accomplished via reflex
action.
The pathways for this neural reflex are as follows:
1. A sensory nerve (pain receptor) sends a nerve impulse to
the spinal column;
2.Interneurons within the spinal cord are excited and in
turn stimulate motor neurons;
3.The excited interneurons cause depolarization of specific
motor neurons, which control the flexor muscles
necessary to withdraw the limb from the point of injury.

28. Another interesting feature of the
withdrawal reflex is that the opposite
limb extended to support the body during
the removal of the injured limb. This
event is called the crossed-extensor
reflex. The extensors are contracting as
the flexors are inhibited.

30. In Summary
 Proprioceptors are position receptors located in
joint capsules, ligaments, and muscles. The three
most abundant joint and ligament receptors are
free nerve endings, Golgi-type receptors, and
Pacinian Corpuscles. These receptors provide the
body with a conscious means of recognizing the
orientation of body parts as well as feedback
relative to the rates of limb movement.
 Reflexes provide the body with a rapid
unconscious means of reacting to some stimuli.

31. Somatic Motor Function
The term somatic refers to the outer (nonvisceral)
regions of the body. The somatic motor portion of the
peripheral nervous system is responsible for carrying
neural messages from the spinal cord to skeletal muscle
fibers. These neural messages are the signals for muscular
contraction to occur.
Motor Neuron – somatic neuron that innervates skeletal
muscle fibers.
Motor Unit – a motor neuron and all the muscle fibers
that it innervates.

32. When a single motor neuron is activated, all
the muscle fibers that it innervates are stimulated
to contract. However, note that the number of
muscle fibers that a motor neuron innervates is
not constant and varies from muscle to muscle.
The number of muscle fibers innervated by a
single motor neuron is called the innervation
ratio (number of muscle fibers/motor neuron). In
muscle groups that require fine motor control the
innervation ratio is low while innervation ratios of
large muscles that are not involved in fine motor
control is high.

33. Vestibular Apparatus and Equilibrium
The vestibular apparatus, an organ located in the inner
ear, is responsible for maintaining general equilibrium. The
receptors contained within the vestibular apparatus are
sensitive to any change in head position or movement
direction. Movement of the head excites these receptors, and
nerve impulses are sent to the CNS regarding this change in
position. Specifically, these receptors provide information
about linear acceleration and angular acceleration. This
mechanism allows us to have a sense of acceleration or
deceleration when running or travelling by car. Further, a sense
of angular acceleration helps us maintain balance when the
head is turning or spinning (e.g performing gymnastics or
diving).

34. The vestibular apparatus controls head
and eye movement during physical activity,
which serves to maintain balance and visually
track the events of movement. In summary,
the vestibular apparatus is sensitive to the
position of the head in space and to sudden
changes in the direction of body movement.
Its primary function is to maintain
equilibrium and preserve a constant plane of
head position.

35. Failure of the vestibular apparatus to
function properly would prevent accurate
performance of any athletic task that
requires head movement. Since most
sporting events require at least some head
movement, the importance of the vestibular
apparatus is obvious.

36. How Exercise Affects
the Nervous System

37. Short Term Effects
The immediate effects of exercise are
on the neurotransmitters. It causes complex
signals to pass through the neurons in the
brain. This alerts the brain for learning and
makes information easier to retain.

38. Long Term Effects
Exercise stresses the muscles which
creates growth factors. This contributes to
brand new brain cells and it increases the
number of pathways for oxygen energy, and
to remove waste from the brain.

39. Aerobic Exercise
Aerobic exercise is the most beneficial
type of exercise on the nervous system. It
improves cognition for all people, but the
cognitive abilities of aerobically active
children particularly stand out against those
who are not aerobically active.

40. Anaerobic Exercise
Anaerobic exercise has no proven
effect on the nervous system, however it
still is a very important part of a balanced
exercise plan and positively affects other
body systems.

41. - END -