COORDINATION IN HUMAN BIOLOGY

Do we sleep every day? Yes, we do, unless we have an important event or

examination coming up, we take a sound sleep. But how do we fall asleep? Does our
brain shut down once we are asleep?
How are we able to react as soon as we dip our fingers into a hot cup of tea? How
are we able to change paths while walking when we hear a car horn honk? Your
answer to all these questions is that animals have a system which is responsible for
all these sudden responses to stimuli. This system is called the Nervous system.
These series of actions that occurs within a fraction of seconds in response to a
change or situation is what basically control and coordination.

Let us have a detailed look at the control and coordination in humans as well as
plants.

Control and Coordination in Humans

In human beings, the control and coordination take place through the nervous
system and the endocrine system that produce and secrete hormones. The five
sense organs in our body, eyes, ears, nose, tongue and skin are called receptors
and these organs functions by receiving information from the environment around
us. Therefore, the response and coordination in both humans and animals involve
the sense organs, the nervous system and hormones.

What is the Nervous system?

The nervous system consists of nerve fibres and nerve cells which transmit
impulses of the nerve between different parts of the body.

It is a system found in animals that synchronizes its functions by passing signals to

and from different parts of the body.

It is brought about by the nervous system after it detects any physical response on
any part of the body due to various changes such as temperature, pressure, light,
etc.

Furthermore, the nervous system coordinates with the endocrine system to react
accordingly. This system of control and coordination is brought about after the
involvement of various internal systems working in sync to respond in accordance.

The neuron is the structural and functional unit of the nervous system. It receives
and transmits electrical nerve impulses. A neuron comprises of :

cell body
dendrites

axon

The cell body consists of a nucleus and granular cytoplasm called Nissl’s granules.

Dendrites are several branched, finger-like projections that transmit nerve impulse
towards the cell body.

The axon arises from the cell body which is branched at the distal end. The cells of
the axon are called Schwann cells which are covered by a myelin sheath. The space
between the myelin sheath is known as Nodes of Ranvier. The end of the axon
contains bulb-like structures called the Synaptic Knob.

Parts of the Nervous System

Vertebrates have a distinct nervous system, which is divided into two main parts:

Central Nervous System (CNS)

Peripheral Nervous System (PNS)

Central Nervous System

It consists of the brain and spinal cord. Generation of sensory emotions takes place
here. Thoughts and emotions are produced, leading to the formation of memories. It
gathers information from all over the body and syncs its activity accordingly. Apart
from sensory motions, it also controls the rate at which we breathe, heart rate, the
temperature of the body, etc.

Explore more about Central Nervous System

Peripheral Nervous System

Everything apart from the brain and spinal cord constitutes the PNS. It includes
nerves and everything that goes down the spinal cord. It is responsible for bringing
information from all parts of the body to the brain. The nerves in the PNS are known
as peripheral nerves, and these nerves connect our sense organs and all other
organs, blood vessels, etc., to the CNS.

Explore more about Peripheral Nervous System

Organs of the Human Nervous System

The human nervous system consists of the following organs:

Brain
Spinal cord

Nerves

Brain
Our brain controls all the actions of the body. It receives the signals from the
sensory organs It comprises of three parts:

Forebrain

Midbrain

Hindbrain

Forebrain helps in the control and coordination of all the voluntary functions and is
the thinking part of the brain.

Midbrain transmits signals from the hindbrain and forebrain.

It helps in controlling the vision, hearing, temperature, etc.

The hindbrain controls and coordinates the heart rate, blood pressure, breathing,
walking, sleeping, etc.

Spinal Cord
The spinal cord is a thick nerve located in the cavity of the backbone. Its upper end
is connected to the brain. It is connected to all the parts of the body through nerves
and controls all the functions of the body by transmitting the information received
through the sensory organs to the brain.

Nerves
The nerves connect the brain and spinal cord to all parts of the body. There are
three types of nerves in our body:

Cranial Nerves connect all parts of the head to the brain.

Spinal Nerves connect all parts of the body to the spinal cord.

Visceral Nerves connect the spinal cord to the internal organs.

Functions of the Nervous System

The main function of a nervous system is the conduction and transmission of the
nerve impulse.
Conduction and Transmission of Nerve Impulse
The information is carried in the form of a nerve impulse. It refers to any electrical,
chemical, or mechanical disturbances created by a stimulus in a neuron. A nerve
impulse is conducted across the synapse with the help of neurotransmitters.

A neuron is non-conducting. Its membrane is positive on the outside and negative

on the inside. The resting potential of a neuron is 70 to 90. The membrane is thus
said to be polarized.

Sodium-potassium pump operates to maintain the resting potential. The axon which
is filled with axoplasm is immersed in the extracellular fluid. The sodium-potassium
pump located on the membrane of the axon pumps 3 sodium ions from axoplasm to
extracellular fluid and 2 potassium ions from extracellular fluid to axoplasm. The
conduction is mediated by the enzyme Sodium-potassium ATPase.

When a stimulus is applied, the sodium ions start rushing inside and the potassium
ions start rushing outside. This changes the permeability of the axon membrane
and the pump stops operating. The resting potential inside the membrane is -70mV
and the action potential is +30mV and the membrane is said to be depolarized. The
action potential travels along the membrane and this is known as a nerve impulse.

After a certain time of action potential, the sodium-potassium pump operates again
and the membrane of the axon gets repolarized by the resting potential.

Reflex Action and Reflex Arcs

Reflex action includes all the actions that are not under the control of our will. That
means these actions are voluntary. For eg., sneezing, coughing, blinking, etc. It is
an automatic response to a stimulus.

Reflex arc refers to the pathways taken by nerve impulses in a reflex action. There
are two types of reflexes- spinal reflexes that involve only the spinal cord, and the
cerebral reflexes that involve only the brain.

The sensory neurons transmit signals from the sensory organ to the relay neuron
present in the spinal cord. These signals are sent back to the muscles through the
motor neuron. The muscles attached to the sense organ move the organ away from
danger.

Also refer Creutzfeldt-Jakob Disease

Hormones in Animals
The endocrine system in animals consists of endocrine glands and hormones.
Hormones are chemical substances that are produced in the endocrine system and
are responsible for passing signals/messages to different parts as a result of an
occurrence in the body, which results in different parts reacting differently to the
message from hormones. Not all cells in the body react to hormones, the cells who
react are called target cells.

Functions of hormones in Animals

Ensures proper growth Responsible to look after the maturing and development in a
proper time frame

Makes sure reproduction happens at the right time

For instance, Thyroid secretes two hormones: Thyroxine (T4) and Thyronine (T3)
which affects everyday metabolism.

Plants don’t possess the same organs and organ systems found in animals.
However, they do have comparable systems to bring similar functions. Continue
reading to know more about how plants bring about control and coordination in
their systems.

Control and Coordination in Plants

Plants do coordinate, but in a different way than animals. Some plants are short,
some are tall, some dense and some scanty. All these parameters are influenced by
the presence of hormones called plant hormones. These hormones are also called
phytohormones or Plant growth regulators. Phytohormones are responsible for
control and coordination in plants. This movement is always in a controlled and
organized environment.

Also read- Plant growth regulators

But if plants coordinate too, why are we not able to see any movement or change?
This is because the response of plants to such reactions is practically too slow, slow
to an extent that we see a change in plants may be weeks or months later. For
example, once we stop watering a plant, it does not die or wither away in a day or
two, it withers away after a fortnight or more.