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NEURAL CONTROL AND COORDINATION 53 SCAN CODE Neural Control and Coordination NEURAL CONTROL AND COORDINATION 21
54 NEURAL CONTROL AND COORDINATION SCAN CODE Neural Control and Coordination Chapter 21 Neural Control and Coordination 1. Introduction to Coordination Coordination is the process through which two or more organs interact and complement the functions of one another. Example: When we do physical exercises, the energy demand is increased for maintaining an increased muscular activity. The supply of oxygen is also increased which in turn increases the rate of respiration, heart beat and blood flow via blood vessels. When physical exercise is stopped, the activities of nerves, lungs, heart and kidney gradually return to their normal conditions. Thus, the functions of muscles, lungs, heart, blood 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 whereas the endocrine system provides chemical integration through hormones. 2. Neural 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. 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. Fig. 21.1 Nerve net in Hydra Fig. 21.2 Nervous system in Cockroach
NEURAL CONTROL AND COORDINATION 55 SCAN CODE Neural Control and Coordination Fig. 21.3 Nervous System in Human 3. Human Neural System  Human neural system is divisible into two main parts:  Central Nervous System (CNS): It is a hollow, dorsally placed structure lying along the mid dorsal axis of the body. It comprises the brain and spinal cord. The brain is lodged in the skull while the spinal cord is enclosed by the vertebral column.  Peripheral Nervous System (PNS): The nerves arising from the central nervous system constitute the peripheral neural system. The nerves originate from the brain and spinal cord and are known as cranial nerves and spinal nerves respectively. Fig. 21.4 Human Neural System
56 NEURAL CONTROL AND COORDINATION SCAN CODE Neural Control and Coordination  Based on their functions, the nerve fibres of PNS are divided into two groups, namely  Afferent nerve fibres: These nerve fibres transmit sensory impulses from tissues and organs to the CNS and form the sensory or afferent pathway.  Efferent nerve fibres: These nerve fibres transmit the motor impulses from the CNS to the concerned tissue/organs called effectors and comprise the motor or efferent pathway.  The peripheral nervous system is again divided into two subdivisions:  Somatic nervous system: This system includes the nerves supplying the skeletal muscles. Thus, the somatic neural system controls the movement of the body by acting on the skeletal muscles.  Autonomic nervous system (ANS): It controls and coordinates such organs which are under involuntary control. So, it is otherwise called an involuntary neural system. It is further classified into:  Sympathetic Neural System  Parasympathetic Neural System 4. Neuron: The Structural and Functional Unit of Nervous System Fig. 21.5 Structure of a Neuron  Nervous tissue is composed of nerve cells or neurons and neuroglia.  A neuron is the structural and functional unit of the nervous system.  Neuroglial cells are non-nervous supporting cells that fill in the interneuronal space. The neuroglial cells are capable of regeneration.  A neuron is a microscopic structure composed of three major parts, namely, the cell body, dendrites and axon.  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 contain Nissl’s granules and are called dendrites. These fibres transmit impulses towards the cell body.  The axon is a long fibre, the distal end of which is branched. Each branch terminates in a bulb-like structure called synaptic knob which possess synaptic vesicles containing chemicals called neurotransmitters.  The axons transmit nerve impulses away from the cell body to a synapse or to a neuro-muscular junction. 4.1 Types of Neurons  Based on their functions, the neurons are classified into three types: