Control And Coordination

Control and Co-ordination in Animals: Nervous system and

endocrine system.
In animals, the nervous system and hormonal system are responsible for
control and co¬ordination.

Receptors: Receptors are the specialized tips of the nerve fibres that
collect the information to be conducted by the nerves.
Receptors are in the sense organs of the animals.
These are classified as follows :

 Phono-receptors: These are present in inner ear.

Functions: The main functions are hearing and balance of the body.
 Photo-receptors: These are present in the eye.
Function: These are responsible for visual stimulus.
 Thermo-receptors: These are present in skin.Functions: These
receptors are responsible for pain, touch and heat stimuli.
These receptors are also known as thermoreceptors.
 Olfactory-receptors: These are present in nose.

Functions: These receptors receive smell.

 Gustatory-receptors: These are present in the tongue.

Functions: These helps in taste detection.

Parts of the Nervous System

It consists of two main parts.

 The Central Nervous System ( CNS)
 Peripheral Nervous System (PNS)
(Source – Wikipedia)

1.Central Nervous System

This system consists of the Brain and Spinal Cord.

2. Peripheral Nervous System

It consists of the cranial nerves coming from the brain and the spinal
nerves coming from the spine. There are 12 pairs of cranial nerves and
31 pairs of spinal nerves in humans.

The peripheral nervous system is made of up of the Autonomic nervous

system and Somatic Nervous System. The Sympathetic nervous system
and Parasympathetic nervous system fall under the autonomic nervous
system.

The following figure explains the interrelation between the various

nervous systems.
(Source – Wikipedia)

Nerves
A nerve is a thread like structure that comes out of the brain and the
spinal cord. So these nerves branch out to all the parts of the body and
are mainly responsible for carrying information and messages from part
to the other. All the nerves make up the peripheral system. They carry
information between the brain and spinal cord.

Types of Nerves

There are different types of nerves, according to the action they

perform. They are:

 Sensory Nerves – These send messages to the brain from all the
sensory organs,
  Motor Nerves – They carry messages from the brain to the muscles in
the body.
 Mixed Nerves – They carry the sensory and motor nerves. They help
in conducting the incoming sensory information and also the
outgoing information to the muscle cells.
Based on which part the nerves connect to the Central Nervous System,
they are classified as:

 Cranial Nerves – They start from the brain and carry messages from
the brain to the rest of the body. Certain nerves are sensory nerves
while some are mixed nerves.
 Spinal Nerves – These nerves originate from the Spinal Cord. They
carry messages to and from the central nervous system. They consist
of mixed nerves.

Neurons

Nerves are made up special cells called the nerve cells or neurons.
These neurons are the basic unit of the nervous system.

( Source – Wikipedia)
Three parts make up a neuron –
Axon
Cell body
Dendrites
The cell body is the main part and has all the components of the cell
such as the nucleus, mitochondria, endoplasmic reticulum etc.
Axons are long cable-like projections that carry the messages along the
length of the cell. These axons are covered by a protective covering
called the myelin sheath. This myelin is made of fat and has a role in
speeding up the transmission of messages down a long axon.
Dendrites are the small branch-like projections that form connections
with other neurons these dendrites can be present at both ends of the
cell.
Synapse is the junction between two nerve cells. It consists of a minute
gap. Impulses or messages pass by diffusion of a neurotransmitter.

Some Amazing Facts

 Neurons have high energy requirements and are bundled with blood
vessels.
 There are billions of neurons in the body, about 100 billion in the
brain and 13.5 million in the spinal cord.
 Axons can transmit electrical signals at a rate of 2,500 per second.

Human Brain
Weighing at just 2% of the total body weight, the human brain is
probably the most complex structure. It is the centre of control of all the
body functions and senses. The average weight of the human brain is
around 1.5 kg and it contains about 86 billion nerve cells (neurons) that
control every action you take.
The human brain along with the spinal cord, make up the Central
Nervous System in humans.

It is the command centre for the Nervous system.

The brain controls even the smallest of our actions such as laughing;
crying out in pain, walking, breathing, etc.

It is a communication centre where decision making happens and is also

responsible for the communication and coordination between different
parts of the body.

Now, this communication takes place with the help of neurons or nerve
cells that send information in the form of chemical and electrical
signals.

The brain receives input from the sensory organs and then sends out the
output to the muscles.

Parts of the human brain

The human brain is made up different parts and compartments, for each
of the functions. Take a look at the different parts of the brain.

 Forebrain
 Midbrain
 Hind Brain
(Source – Wikipedia)

Fore Brain

It is the main thinking part of the brain and controls the voluntary
actions. The forebrain processes sensory information that is collected
from the various sense organs such as ears, eyes, nose, tongue, skin. It is
because of the presence of forebrain, humans are placed at the highest
level in the animal chain.

The forebrain consists of the Cerebrum, Thalamus and Hypothalamus.

The cerebrum is the biggest part of the brain. This part we associate
with higher brain functions such as thinking and action. It contains the
cerebral cortex and other subcortical structures. The cerebral cortex is
highly wrinkled and makes the brain very efficient.

Now the cerebral cortex again divides into four divisions called lobes.
They are:

 Frontal lobe –Is associated with parts of speech, reasoning, problem-

solving, planning, movement and emotions
 Parietal lobe – We associate parietal lobe with recognition,
orientation, and perception of stimuli
 Occipital lobe – Is responsible for visual processing
 Temporal lobe – Finally temporal lobe is associated with memory,
speech perception and recognition of auditory stimuli
The cerebrum is divided into two halves by a deep furrow.

These halves are the left and right hemispheres.

Each side functions slightly different from the other, even though they
are symmetrical. So the right hemisphere links to creativity whereas the
left hemisphere relates to logic abilities.

And Corpus callosum connects the two hemispheres.

Mid Brain

The midbrain connects the forebrain and the hindbrain. It acts as a

bridge and transmits signals from hindbrain and forebrain. It is
associated with motor control, vision, hearing, temperature regulation,
alertness.

Hind Brain

It is the control centre for visceral function.

As a result, this part of the brain plays a role in controlling the heart
rate, breathing, blood pressure, sleep and waking up functions etc.
The hindbrain has three parts, namely – medulla oblongata, pons and
cerebellum.

The cerebellum is responsible for maintaining equilibrium, transfer of

information, fine adjustments to motor actions, coordinating eye
movements etc.

Coordination and body balance, posture during walking, riding,

standing, swimming, running, are all maintained by the cerebellum.

Hormones In Animals
Animals are more complex than plants.

They have many specialised organs that perform specialised functions

for their control and coordination.

This coordination in animals occurs due to the nervous coordination

(Nervous System) and the chemical coordination (Endocrine System).
Both these systems act in a coordinated manner in animals, so as to
regulate the various body activities.

Endocrine System

The endocrine system comprises of different endocrine glands and

hormones.

These endocrine glands in animals help in the chemical coordination.

They secrete chemicals called hormones.

They are special messengers that control many body functions,

including hunger, body temperature, mood, growth and
development, metabolism, reproductive processes etc.
The endocrine glands are ductless and hence are also called as ductless
glands.

What are Hormones?

Hormones are chemicals secreted by the endocrine glands directly into

the bloodstream.

Through the blood, these hormones in animals reach their target organs
to stimulate or inhibit specific physiological processes.

The site of production of the hormones is different and the site of action
is different.

Even though there are different hormones in the bloodstream, each will
act only on the specific target organ.

There are around 20 major hormones in animals that are released by the
endocrine glands into the blood, playing a major role in many of the
physiological processes happening in the body.

Different Endocrine Glands

 Hypothalamus
 Pituitary gland
 Thyroid gland
 Parathyroid gland
  Pineal gland
 Adrenal gland
 Pancreas
 Testes
 Ovaries

(Source – Wikipedia)

Hypothalamus

This gland forms an important link between the nervous system and the
endocrine system, via the pituitary gland.

Some of the important functions are:

 Helps in maintaining the body temperature, controls sleep, hunger,
thirst, emotions and moods.
 It also controls the release of 8 major hormones by the pituitary
gland.
 Controls the sexual behaviour and reproduction.
 It controls the circadian rhythm of the body.
Pituitary Gland

The pituitary gland is very small in size but is called as the Master
Gland, as many endocrine glands are controlled by the hormones
secreted by it.

It also stimulates other endocrine glands to produce hormones.

Some of the hormones released by this gland are growth hormone,

thyroid stimulating hormone, MSH, LH, FSH etc.

Thyroid Gland

It is the largest endocrine gland that is shaped like a butterfly. It

produces the thyroxine hormone, which controls the metabolic rate in
the body.

Apart from that, it also plays a role in the bone growth, development of
the brain and nervous system in children. Iodine is important for the
synthesis of thyroxine.

Parathyroid Gland

This gland releases parathormone which helps in regulating the calcium

and phosphorus levels in the bone.
Pineal gland

This produces melatonin hormone that regulates the sleep patterns.

Adrenal gland

These glands are located on top of the kidneys and produce hormones
such as adrenaline, cortisol, and aldosterone etc.

These hormones control stress, help control blood sugar, burn protein
and fat and also regulate blood pressure.

Pancreas

They secrete two important hormones – insulin and glucagon. Both

work together to maintain the glucose levels in the blood.

Testes

These glands are present in males and produce testosterone hormone.

Ovaries

These glands are present in females. The hormones produced by ovaries

are oestrogen and progesterone.

Coordination in Plants
Unlike animals, plants do not have any muscular system or nervous
system.

But, they are still able to show movement and also coordination. These
movements are always controlled and not haphazard.
What is coordination in plants?
Coordination is the ability to use different parts of the plant together,
smoothly and efficiently.

In plants, coordination is due to the result of a chemical system, wherein

plant hormones or phytohormones have a major role.

Movement in plants

Plants exhibit two types of movements.

1. Growth-dependent movements called the Tropic Movements.

( towards or away from a stimulus)

2. Non-growth dependent movements called the Nastic Movements.

( independent of stimulus)

Tropic movements

These can be classified again into 5 types. They are:

 Phototropism (light)
 Geotropism (gravity)
 Hydrotropism (water )
 Chemotropism (chemicals)
 Thigmotropism (touch)

1. Phototropism – It is the movement of plants in response to light. The

shoot system of a plant exhibits this characteristic. The shoot moves
towards the light.
2. Geotropism – It is the movement of a plant part towards the soil. This
is a characteristic of the root system. The roots always move in
the direction of the earth’s gravity.
3. Hydrotropism– It is the movement of a plant towards the water. The
stimulus here is water.
4. Chemotropism – It is the movement of plants in response to a
chemical stimulus. A classic example of this type of movement is
the growth of the pollen tube towards the ovule, during fertilization,
in a flower.
5. Thigmotropism – It is a directional movement in plants in response to
touch. For e.g. the plant tendrils climb around any support which they
touch.

Nastic Movements

Nastic movements in plants are not directional movements.

They are not dependent on stimulus and are growth independent.

For example, the leaves of a touch me not plant (Mimosa pudica), fold
up immediately when touched.
These kinds of changes occur due to the changes in the amount of water
in the leaves.

Depending on the quantity, they either swell up or shrink.

Plant hormones or phytohormones

They are responsible for the control and coordination of plants.

There are different types of hormones, which affect the growth of a

plant.
 Phytohormones are chemical compounds which are released by
stimulated cells.

These hormones are diffused around the plant cells.

They have a role to play in the cell division, cell enlargement, cell
differentiation, fruit growth, falling of leaves, ripening of fruits, ageing
of plants etc.

The different types of phytohormones are:

1. Auxins
2. Gibberellins
3. Cytokinins
4. Abscisic acid
Auxins – They help in the cell growth at the shoot tips. By elongating
the cells, they help in the growth process.

Gibberellins – These hormones are responsible for the cell growth in

the stem, seed germination, and flowering.

Cytokinins – They promote cell division in plants. They also promote

the opening of the stomata and delay ageing in leaves.

Abscisic acid – This hormone inhibits the growth of the plant. And
therefore, it promotes dormancy in seeds and buds. The detachment of
fruits, flowers, and falling of leaves etc. are promoted by this hormone.