CBSE Class 10 Science Notes Chapter 6: Control and Coordination in Living Organisms

A common assumption is that something is alive if it moves. For example, the growth of a seedling is a form of movement in plants. However, movements may not be tied to growth in animals and some plants, like when a cat runs or children play. Movement is often a response to environmental changes. For instance, a cat may run after seeing a mouse while plants grow toward sunlight. These movements are not random; they are controlled and coordinated responses to environmental stimuli.

1.0Nervous System in Animals

• In animals, the nervous system plays a key role in coordinating and controlling movements. 
• The nervous system is made up of nerve cells, or neurons, which conduct information via electrical impulses. Sensory receptors in our sense organs—such as taste receptors in the tongue and smell receptors in the nose—detect environmental changes. 
• This information triggers a chemical reaction, creating electrical impulses that travel through neurons. 
• These impulses are then transmitted to muscles or glands, causing action.

Nervous System 

• The nervous system in vertebrates is highly evolved. It is the control system for all our actions, thinking and behavior. 
• It is concerned with receiving stimuli from the external or internal environment of the body, interpreting these stimuli and producing the appropriate response to these stimuli. 
• To achieve this, highly specialized cells are required which can receive the message and conduct them to the chief centers of the nervous system where they are to be interpreted and then returned to the relevant part of the body. 
• Neurons or nerve cells are the structural and functional unit of the nervous system. Each neuron has following two parts: 
• Cyton or cell body – Contains a central nucleus and cytoplasm with characteristic deeply stained particles called Nissl's granules [i.e. clumps of ribosomes]. 
• Cell processes – These are of two types
• Dendrites : These may be one to many, generally short and branched cytoplasmic processes. Dendrites are afferent processes because they receive impulse from a receptor or other neuron and bring it to the cyton. 
• Axon : It is a single generally long efferent process which conducts impulse away from cyton to other neurons. 
• Longest cell in the body is the neuron because the axon can be more than one meter long. Axon has uniform thickness but it has terminal thin branches called telodendria. 
• Terminal end buttons or synaptic knobs occur at the end of telodendria.

2.0Reflex Actions

• A reflex action is a quick involuntary action in response to an external or internal stimulus, generally without involvement of the brain. 
• E.g. A tap on the knee results in a spontaneous withdrawal i.e. a knee-jerk. Similarly, when we touch a hot object we spontaneously withdraw our hand.

3.0Human Nervous System

4.0The Human Brain

• The brain is the primary coordinating centre of the body, responsible for processing information and making decisions. 
• The brain has three major regions: the fore-brain, midbrain, and hind-brain. 
• The fore-brain is the main thinking centre, responsible for voluntary actions like talking or moving objects. 
• The midbrain and hind-brain, on the other hand, control involuntary actions such as heartbeat, breathing, and digestion.
• The brain is well-protected within the skull, which acts as a bony box. 
• The vertebral column protects the spinal cord, which is connected to the brain. 
• The central nervous system (CNS), composed of the brain and spinal cord, communicates with the rest of the body through the peripheral nervous system, which consists of cranial and spinal nerves.

Muscle Movement and Nervous Impulses

• When the nervous system sends an electrical impulse to muscles, the muscle fibers move by changing shape. 
• Muscle cells contain proteins that rearrange themselves when stimulated by electrical impulses, leading to muscle contraction. 
• Voluntary muscles, like those in the arms and legs, are controlled consciously, while involuntary muscles, such as those in the digestive system, function automatically without conscious control.

5.0Coordination in Plants

• Unlike animals, plants do not have a nervous system or muscles. Yet, they respond to stimuli in their environment. 
• For instance, the sensitive plant ("touch-me-not") folds its leaves when touched, a movement without growth. 
• Plants also show directional growth, called tropism, in response to environmental stimuli like light (phototropism) and gravity (geotropism). 
• Plant hormones, or chemicals, are crucial in controlling growth and responses to stimuli. Auxins, for example, promote cell growth and elongation, especially in the shoot tip. 
• When light hits one side of the plant, auxins move to the shaded side, causing the cells to grow faster, resulting in the plant bending toward the light. 
• Other hormones, like gibberellins, promote stem growth, while cytokinins stimulate cell division.
• Plants also have hormones that inhibit growth. Abscisic acid, for instance, causes leaves to wilt and slows growth. Plants rely on chemical communication rather than nervous impulses for control and coordination.

6.0Difference Between Tropic and Nastic Movement

7.0Hormones in Animals