Title NEURAL CONTROL & COORDINATION.pdf ✅

 Digital www.allendigital.in [ 165 ] 1. Introduction : • To maintain homeostasis of the body functions of the organs/organ systems in our body must be coordinated. • Coordination is the process through which two or more organs interact and complement the functions of one another. For example- (a) When we do physical exercises, the energy demand is increased for maintaining an increased muscular activity, for that the supply of oxygen is also increased. The increased supply of oxygen necessitates an increase in the rate of respiration, heart beat and increased blood flow via blood vessels. (b) When physical exercise is stopped, the activities of nerves, lungs, heart and kidney gradually return to their normal state thus, the functions of muscles, lungs, heart, blood vessels, kidney and other organs are coordinated while performing physical exercises. • In human body the neural system and the endocrine system jointly coordinate and integrate all the activities of the body so that the organs function in a synchronised fashion. • Nervous system and endocrine system are called Integrative system of the body. • The neural system provides an organised network of point-to-point connections for a quick coordination and 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. • The 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. • Vertebrates have a more developed neural system. Brain Ganglia Vertebrates Hydra Insect Nerve cells Neural Control and 04 Coordination
NEET : Biology [ 166 ] www.allendigital.in  Digital 3. Human Neural System : • The human neural system is divided into two parts : Central neural system (CNS) : The CNS includes the brain and the spinal cord and is the site of information processing and control. Peripheral neural system (PNS) : The PNS comprises of all the nerves of the body associated with the CNS (brain and spinal cord). • The PNS is divided into two divisions :- (A) Somatic neural system (SNS) : It relays impulses from the CNS to skeletal muscles and voluntary organs. (B) Autonomic neural system (ANS) : It transmits impulses from the CNS to the involuntary organs and smooth muscles of the body. The autonomic neural system is further classified into sympathetic neural system and parasympathetic neural system. Peripheral Nervous System (PNS) Afferent fibres Efferent fibres The efferent fibres transmit regulatory impulses from the CNS to the concerned peripheral tissues/organs. The afferent nerve fibres transmit impulses from tissues/organs to the CNS. Sympathetic neural system • Works in during emergency condition. • Prepare us for stressful conditions. Parasympathetic neural system • Works in during normal life. • Relaxes us after stress is over. Autonomic neural system Central Nervous System (CNS) • Brain and spinal cord • Integrative and control centres Peripheral Nervous System (PNS) • Cranial nerves and spinal nerves • Communication lines between the CNS and the rest of the body Sensory (afferent division) • Somatic and Visceral sensory nerve fibres. • Conducts impulses from receptors to CNS. Motor (efferent division) • Motor nerve fibres Conducts impulses from CNS to Effectors organs (muscles, glands and organs). Somatic Nervous System (SNS) • Voluntary (somatic motor) • Conducts impulses from the CNS to skeletal muscles Autonomic Nervous System (ANS) • Involuntary (visceral motor) • Conducts impulses from the CNS to cardiac muscles, smooth muscles and glands Sympathetic division Parasympathetic division
Neural Control and Coordination  Digital www.allendigital.in [ 167 ] • Visceral nervous system is the part of the peripheral nervous system that comprises the whole complex of nerves, fibres, ganglia, and plexuses by which impulses travel from the central nervous system to the viscera and from the viscera to the central nervous system. 4. Nervous Tissue : • Nervous tissue originates from ectoderm and is specialized for receiving stimuli (Excitability) and transmit message (conductivity). (A) Neuron (Nerve Cell) : • It is the functional and structural unit of nervous system. • It generates and transmits nerve impulses. • It is the longest cell of the body. A neuron is a microscopic structure composed of three major parts, namely :- (i) Cell body or Cyton (ii) Dendrites or dendrons (iii) Axon (i) Cell Body or Cyton or Soma or Perikaryon : • The cell body contains cytoplasm with typical cell organelles and certain granular bodies called Nissl’s granules. • Except centriole, all cell organelles are found in cytoplasm. • Centriole is absent in the nerve cell thus cell division is absent. • Neurofibril are also found in nerve cell. Nissl's granules • Endoplasmic reticulum & ribosome form granules like structure. • These are the centre of protein synthesis. • Site of Nissl’s Granules - Cyton & dendron. Neuron Neuroglia (neuroglial cells) Cyton/Cell body Process of Neuron (Neurites) Dendrites (Highly branched) Axon (Longest) NEURAL TISSUES Dendrites Nissl’s granules Cell body Nucleus Schwann cell Axon Myelin sheath Node of Ranvier Axon terminal Synaptic knob
NEET : Biology [ 168 ] www.allendigital.in  Digital Neurofibrils • Many small fibrils are found in the cytoplasm called neurofibrils, these help in internal conduction in the cyton. • Site of Neurofibrils – Cyton, dendron & Axon (ii) Dendrites or Dendrons : • Short fibers • Branch repeatedly • Project out of the cell body • Also contain Nissl’s granules • These fibers transmit impulses towards the cell body (Centripetal Conduction). (iii) Axon : • The axon is a long fibre, the distal end of axon is branched called telodendria. • Axon is covered by Axolemma. • Part of cyton where axon arises is called Axon hillock. • Cytoplasm which contains in axon is called axoplasm. • Each branch terminates as a bulb-like structure called synaptic knob which possess synaptic vesicles containing chemicals called neurotransmitters. • The axon transmit nerve impulses away from the cell body to a synapse or to a neuro-muscular junction. • Nissl's granules are absent in the axoplasm. • Conduction is centrifugal. (B) Myelinogenesis : • Myelin is a fatty material (Phospholipids) with a high electrical resistance and acts as an electrical insulator in the same way as the rubber and plastic covering of electrical wiring. (i) Myelinogenesis in PNS : • Axon is covered by a layer of phospholipids/sphingomyelin which is called as medulla or myelin sheath. • Schwann cell takes part in the deposition of myelin sheath (myelinogenesis) across Axon. • Myelin sheath acts as insulator and prevents leakage of ions. • The neurilemma is membrane of Schwann cells. CNS — Oligodendrocytes (Neuroglia) PNS — Schwann Cell MYELINOGENESIS In (Carried out by) Dendron Dendrites Axon hillock Axolemma Synaptic knob Telodendria Axoplasm