230 BIOLOGY
CHAPTER 18
NEURAL CONTROL AND
COORDINATION
18.1 Neural System As you know, the functions of the organs/organ systems in our body
must be coordinated to maintain homeostasis. Coordination is the
18.2 Human Neural
process through which two or more organs interact and complement the
System
functions of one another. For example, when we do physical exercises,
18.3 Neuron as the energy demand is increased for maintaining an increased muscular
Structural and activity. The supply of oxygen is also increased. The increased supply of
Functional Unit oxygen necessitates an increase in the rate of respiration, heart beat and
of Neural increased blood flow via blood vessels. When physical exercise is stopped,
System the activities of nerves, lungs, heart and kidney gradually return to their
18.4 Central Neural normal conditions. Thus, the functions of muscles, lungs, heart, blood
System vessels, kidney and other organs are coordinated while performing physical
exercises. In our body the neural system and the endocrine system jointly
coordinate and integrate all the activities of the organs so that they function
in a synchronised fashion.
The neural system provides an organised network of point-to-point
connections for a quick coordination. The endocrine system provides
chemical integration through hormones. In this chapter, you will learn
about the neural system of human, mechanisms of neural coordination
like transmission of nerve impulse and impulse conduction across
a synapse.
Reprint 2025-26
, NEURAL CONTROL AND COORDINATION 231
18.1 N EURAL SYSTEM
The neural system of all animals is composed of highly specialised cells called
neurons which can detect, receive and transmit different kinds of stimuli.
The neural organisation is very simple in lower invertebrates. For
example, in Hydra it is composed of a network of neurons. The neural
system is better organised in insects, where a brain is present along with
a number of ganglia and neural tissues. The vertebrates have a more
developed neural system.
18.2 HUMAN NEURAL SYSTEM
The human neural system is divided into two parts :
(i) the central neural system (CNS)
(ii) the peripheral neural system (PNS)
The CNS includes the brain and the spinal cord and is the site of
information processing and control. The PNS comprises of all the nerves
of the body associated with the CNS (brain and spinal cord). The nerve
fibres of the PNS are of two types :
(a) afferent fibres
(b) efferent fibres
The afferent nerve fibres transmit impulses from tissues/organs to
the CNS and the efferent fibres transmit regulatory impulses from the
CNS to the concerned peripheral tissues/organs.
The PNS is divided into two divisions called somatic neural system
and autonomic neural system. The somatic neural system relays
impulses from the CNS to skeletal muscles while the autonomic neural
system transmits impulses from the CNS to the involuntary organs and
smooth muscles of the body. The autonomic neural system is further
classified into sympathetic neural system and parasympathetic neural
system.
Visceral nervous system is the part of the peripheral nervous system
that comprises the whole complex of nerves, fibres, ganglia, and plexuses
by which impulses travel from the central nervous system to the viscera
and from the viscera to the central nervous system.
18.3 N EURON AS STRUCTURAL AND FUNCTIONAL UNIT OF
NEURAL SYSTEM
A neuron is a microscopic structure composed of three major parts, namely,
cell body, dendrites and axon (Figure 18.1). The cell body contains cytoplasm
with typical cell organelles and certain granular bodies called Nissl’s granules.
Short fibres which branch repeatedly and project out of the cell body also
Reprint 2025-26
CHAPTER 18
NEURAL CONTROL AND
COORDINATION
18.1 Neural System As you know, the functions of the organs/organ systems in our body
must be coordinated to maintain homeostasis. Coordination is the
18.2 Human Neural
process through which two or more organs interact and complement the
System
functions of one another. For example, when we do physical exercises,
18.3 Neuron as the energy demand is increased for maintaining an increased muscular
Structural and activity. The supply of oxygen is also increased. The increased supply of
Functional Unit oxygen necessitates an increase in the rate of respiration, heart beat and
of Neural increased blood flow via blood vessels. When physical exercise is stopped,
System the activities of nerves, lungs, heart and kidney gradually return to their
18.4 Central Neural normal conditions. Thus, the functions of muscles, lungs, heart, blood
System vessels, kidney and other organs are coordinated while performing physical
exercises. In our body the neural system and the endocrine system jointly
coordinate and integrate all the activities of the organs so that they function
in a synchronised fashion.
The neural system provides an organised network of point-to-point
connections for a quick coordination. The endocrine system provides
chemical integration through hormones. In this chapter, you will learn
about the neural system of human, mechanisms of neural coordination
like transmission of nerve impulse and impulse conduction across
a synapse.
Reprint 2025-26
, NEURAL CONTROL AND COORDINATION 231
18.1 N EURAL SYSTEM
The neural system of all animals is composed of highly specialised cells called
neurons which can detect, receive and transmit different kinds of stimuli.
The neural organisation is very simple in lower invertebrates. For
example, in Hydra it is composed of a network of neurons. The neural
system is better organised in insects, where a brain is present along with
a number of ganglia and neural tissues. The vertebrates have a more
developed neural system.
18.2 HUMAN NEURAL SYSTEM
The human neural system is divided into two parts :
(i) the central neural system (CNS)
(ii) the peripheral neural system (PNS)
The CNS includes the brain and the spinal cord and is the site of
information processing and control. The PNS comprises of all the nerves
of the body associated with the CNS (brain and spinal cord). The nerve
fibres of the PNS are of two types :
(a) afferent fibres
(b) efferent fibres
The afferent nerve fibres transmit impulses from tissues/organs to
the CNS and the efferent fibres transmit regulatory impulses from the
CNS to the concerned peripheral tissues/organs.
The PNS is divided into two divisions called somatic neural system
and autonomic neural system. The somatic neural system relays
impulses from the CNS to skeletal muscles while the autonomic neural
system transmits impulses from the CNS to the involuntary organs and
smooth muscles of the body. The autonomic neural system is further
classified into sympathetic neural system and parasympathetic neural
system.
Visceral nervous system is the part of the peripheral nervous system
that comprises the whole complex of nerves, fibres, ganglia, and plexuses
by which impulses travel from the central nervous system to the viscera
and from the viscera to the central nervous system.
18.3 N EURON AS STRUCTURAL AND FUNCTIONAL UNIT OF
NEURAL SYSTEM
A neuron is a microscopic structure composed of three major parts, namely,
cell body, dendrites and axon (Figure 18.1). The cell body contains cytoplasm
with typical cell organelles and certain granular bodies called Nissl’s granules.
Short fibres which branch repeatedly and project out of the cell body also
Reprint 2025-26
