Control and Coordination

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.
Nervous System: The nervous system is composed of specialized tissues, called nervous tissue. The
nerve cell or neuron is the functional unit of the nervous system. It is the nervous system which is
mainly responsible for control and coordination in complex animals.
Functions of the nervous system
 Nervous system receives information from the environment.
 To receive the information from the various body.
 To act according to through muscles and glands.
A neuron is the structural and functional unit of the nervous system.
Types of neuron
 Sensory neuron: These neurons receive signals from a sense organ.
 Motor neuron: These neurons send signals to a muscle or a gland.
 Association or relay neuron: These neurons relay the signals between sensory neuron and motor
neuron.
Synapse: The point contact between the terminal branches of axon of one neuron with the dendrite of
another neuron is called synapse.
Neuromuscular Junction (NMJ): NMJ is the point where a muscle fibre comes in contact with a motor
neuron carrying nerve impulse from the control nervous system.
Transmission of nerve impulse: Nerve impulses travel in the following manner from one neuron to
the next :
Dendrites → cell body → axon → nerve endings at the tip of axon → synapse → dendrite of next neuron.
Chemical released from axon tip of one neuron, cross the synapse or neuromuscular junction to reach
the next cell.
Human Nervous System: The nervous system in humans can be divided into three main parts;
1. Central Nervous System: The central nervous system is composed of the brain and the spinal cord.
The brain controls all the functions in the human body. The spinal cord works as the relay channel for
signals between the brain and the peripheral nervous system.
2. Peripheral Nervous System: The peripheral nervous system is composed of the cranial nerves and
spinal nerves. There are 12 pairs of cranial nerves. The cranial nerves come our of the brain and go to
the organs in the head region. There are 31 pairs of spinal nerves. The spinal nerves come out of the
spinal cord and go to the organs which are below the head region.
3. Autonomous Nervous System: The autonomous nervous system is composed of a chain of nerve
ganglion which runs along the spinal cord. It controls all the involuntary actions in the human body. The
autonomous nervous system can be divided into two parts :
 Sympathetic nervous system.
 Parasympathetic nervous system.
Human Brain: Human brain is a highly complex organ, which is mainly composed of nervous
tissue. The tissues are highly folded to accommodate a large surface area in less space. The brain is
covered by a three-layered system of membranes, called meninges. Cerebrospinal fluid is filled
between the meninges. The CSF providers cushion the brain against mechanical shocks.
Furthermore, protection. The human brain can be divided into three regions, viz. forebrain,
midbrain and hindbrain.
Parts of Human Brain :
 Fore-brain: It is composed of the cerebrum(control the movement of voluntary muscles),
olfactory lobes( sense of smell) and Diencephalon( sense of hunger)
 Mid-brain: It is composed of the hypothalamus.
 Hind-brain: It is composed of the cerebellum(balance of the body), pons(take part in
respiration), medulla oblongata (involuntary .. salivation, vomiting, BP)
Spinal cord: Spinal cord controls the reflex actions and conducts massages between different parts of
the body and brain.
Reflex Action: Reflex action is a special case of involuntary movement involuntary organs. When a
voluntary organ is in the vicinity of sudden danger, it is immediately pulled away from the danger to
save itself. For example, when your hand touches a very hot electric iron, you move away your hand in a
jerk. All of this happens in flash and your hand is saved from the imminent injury. This is an example of
reflex action.
Reflex Arc: The path through which nerves signals, involved in a reflex action, travel is called the reflex
arc. The following flow chart shows the flow of signal in a reflex arc.
Receptor → Sensory neuron → Relay neuron → Motor neuron → Effector (muscle)
The receptor is the organ which comes in the danger zone. The sensory neurons pick signals from the
receptor and send them to the relay neuron. The relay neuron is present in the spinal cord. The spinal
cord sends signals to the effector via the motor neuron. The effector comes in action, moves the
receptor away from the danger.
The reflex arc passes at the level of the spinal cord and the signals involved in reflex action do not travel
up to the brain. This is important because sending signals to the brain would involve more time.
Although every action is ultimately controlled by the brain, the reflex action is mainly controlled at the
level of spinal cord.
Protection of brain and spinal cord
Brain is protected by a fluid filled balloon which acts as shocks absorber and enclosed in cranium (Brain
box)
Spinal chord is enclosed in vertebral column.
Muscular Movements and Nervous Control: Muscle tissues have special filaments, called
actin and myosin. When a muscle receives a nerve signal, a series of events is triggered in the muscle.
Calcium ions enter the muscle cells. It result in actin and myosin filaments sliding towards each other
and that is how a muscle contracts. Contraction in a muscle brings movement in the related organ.

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CONTROL AND COORDINATION

Control and Co-ordination in Animals: Nervous system and endocrine system.

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