Only a relatively small portion of the fibres of the optic nerves actually cross at the chiasma, many of them simply bending and remaining on the same side of the brain. The axon contains neurofibrils and neurotubules but does not have Nissl’s granules, Golgi complex, ribosomes, pigment granules, fat globules, etc. Most sensitive part of neuron is axon hillock. The part of cyton from where the axon arises is called axon hillock. They conduct nerve impulse towards the cell body and are called afferent processes (= receiving processes).Īxon is a single, usually very long process of uniform thickness. The dendrites contain neurofibrils, neurotubules and Nissl’s granules. These are usually shorter, tapering and much branched processes. These are of two types: dendrites or dendrons and an axon or axis cylinder or neuraxon. The processes of neurons are called neurites. Cyton is concerned with metabolic maintenance and growth. Ageing neurons contain a pigment lipofuscin (made up of residual bodies derived from lysosomes). Previously the name perikaryon was given to the cyton (cell body or soma). The cytoplasm immediately surrounding the nucleus is loaded with protein-synthetic machinery, and is called perikaryon. The Nissl’s granules probably synthesize proteins for the cell.Ĭentrioles, formerly believed to be absent in mature neurons, have been described in neurons and may be associated with the production and maintenance of microtubules. Finally, take advantage of the teaching resources to add depth and additional learning to your unit on the nervous system.The Nissl’s granules (also called Nissl’s bodies) are irregular masses of rough endoplasmic reticulum with numerous attached and free ribosomes and polysomes. Add worksheets, clip art and activities to really help your young students absorb the science and learn the concepts. Beginning with the lesson plans you can teach the nervous system to your class room in an easy and enjoyable way. It's a complicated system that can be difficult to teach. Teaching the human nervous system is a big job. Your brain and nerve endings feel the heat and signal your muscles to retract your hand. The nervous system is designed to help humans perceive the world around them and to keep them safe.Ī simple example of the human nervous system is when your finger or hand gets too close to a heat source and you instinctively pull back. The human nervous system is a system of nerves that begins in the brain and is part of every area of your body from your fingertips to your eyes, from the skin on your toes to your bones, tendons and ligaments.
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