The Human Nervous System

� � � � � The Human Nervous System �� The Human Nervous System �� 13 The membranes of the cell body and its dendrites have special chemicals Our bodies have over ten million million (10 ) living cells Terminal dendrite which must work in co-operation for us to live and grow. To Nerve Impulse onto which a signalling chemical from another neuron can lock and Imagine you are on a boat in the stimulate it into activity. co-operate they must communicate. The brain, spinal cord, middle of the ocean with no sail, no compass and no rudder. How nerves, sense organs and receptors are the vital parts of Synaptic vesicle The axon is the long extension from the nerve cell body that transfers the signal to the target site. Axons can be up to one metre in length; the long do you think it would take to the human nervous system that facilitate communication Synaptic knob Transmitter transfer time over one long axon is much shorter than if the signal had fi nd land? betweenOur bodies our cells. have In this over lesson ten we willmillion look atmillion the formation (1013 ) living cells substance The membranes of the cell body and its dendrites have special chemicals Tetorminal travel dendriteover many cells. If the nerve cells were the same size as most Health care systems can be just Nerve Impulse onto which a signalling chemical from another neuron can lock and andwhich function must of the work nervous in co-operation system. for us to live and grow. To other cells, then, for example, a signal from the foot to the brain would like that boat at sea. Without new Imagine you are on a boat in the have to travel along about 200,000 cellsstimulate and would ittake into about activity. seven medicines to tackle disease, middle of the ocean with no sail, Howco-operate is our nervousthey must system communicate. formed? The brain, spinal cord, minutes.We could not survive if there were such delays in responding without new equipment to no compass and no rudder. How Release of to dangersSynaptic vesicle The axon is the long extension from the nerve cell body that transfers Thenerves, central nervous sense system organs (CNS) andbegins receptors to form halfway are into the the vital parts of Presynaptic perform operations, and perhaps most importantly of all, without transmitter membrane long do you think it would take to embryonic period, 28 days after conception. The development of substance Synaptic knob The numerous terminal dendrites ensure extensivethe signal communication to the target with site. Axonsexperienced can be up researchers to one metre to come in length; up with thenew breakthroughs, the human nervous system that facilitate communication Synaptic Transmitter our health care system could just drift aimlessly and never reach fi nd land? the central nervous system is the fi rst major event in the formation of cleft many of the cells of the target tissue. Synaptictransfer knobs timetransfer over the signalsone long axon is much shorter than if the signal had between our cells. In this lesson we will look at the formation substance new ground. organs in the developing embryo. The nervous system develops from to the target cell. to travel over many cells. If the nerve cells were the same size as most Health care systems can be just the ectoderm, the outer of the three germ layers. The skeletal system Receptor Postsynaptic The Health Research Board (HRB) provides direction and funding and function of the nervous system. molecule other cells, then, for example, a signal from the foot to the brain would like that boat at sea. Without new develops from the mesoderm, the middle of the germ layers, with the membrane What is the role of neurotransmitters? to support health research in Ireland. By doing so, the HRB cranium and vertebrae forming a protective cover around the brain and have to travel along about 200,000 cells and would take about seven medicines to tackle disease, Fig.2 The synaptic cleft Although nerve signals are electric in nature, the nervous system is not underpins the delivery of, and the continued improvement of, our spinalHow cord. is our nervous system formed? minutes.We could not survive if there were such delays in responding strictly like an electric circuit. Due to the presence of the synaptic cleft, health care system. without new equipment to Sensory neurons transferRelease signals of from the stimulated sense organs to to dangers The central nervous system (CNS) begins to form halfwaythe into central the nervous system (CNS). Motor neurons transfer signals from the ‘electricalPresynaptic signal’ cannot run directly into the target cell. The HRB funds research into a wide range of areas. Our fundedperform operations, and perhaps most importantly of all, without transmitter membrane embryonic period, 28 days after conception. The developmentthe CNS toof the musclessubstance and glands initiating a response to a stimulus. The arrival of a signal, called an impulse, Thetriggers numerous the release terminal of special dendrites researchersensure extensive study diseases communication like diabetes, cancer with and Parkinson’sexperienced researchers to come up with new breakthroughs, Interneurons relay signals between the motor and sensory neurons. chemicals into Synapticthe gap. These chemicals, neurotransmitters, diffuse disease. In Parkinson’s disease we are studying ways to growour health care system could just drift aimlessly and never reach the central nervous system is the fi rst major event in the formation of cleft many of the cells of the target tissue. Synaptic knobs transfer the signals across the gap locking into the receptor molecules in the target cell nerve cells outside the body which could then be transplantednew ground. organs in the developing embryo. The nervous system developsThe motor from and sensory neurons are specialised for rapid, long distance, to the target cell. back into the body. This is just one of our projects on the central direct communication. They have three major functions – to receive membrane, causing it to ‘switch on’. It switches off when no more the ectoderm, the outer of the three germ layers. The skeletal system Receptor neurotransmittersPostsynaptic are released and those that were previously released nervous system. The Health Research Board (HRB) provides direction and funding Brain signals, transmit signals quickly over a long distancemolecule and transfer signals develops from the mesoderm, the middle of the germ layers,to with the target the cell. havemembrane been broken down by an enzyme inWhat the gap. isThe thebroken roledown of neurotransmitters?In addition to funding research, we also carry out our ownto support health research in Ireland. By doing so, the HRB neurotransmitters are then reabsorbed into the synaptic knob. cranium and vertebrae forming a protective cover around the brain and Fig.2 The synaptic cleft research in areas such as mental health, child health and drugunderpins the delivery of, and the continued improvement of, our Fig.3 The sensory and motor neuron Although nerve signals are electric in nature, the nervous system is not spinal cord. Because the transmission between neurons is by a chemical process, misuse. The HRB keeps databases on drug misuse, disability andhealth care system. strictly like an electric circuit. Duemental to the health. presence By examining of the thissynaptic data we cleft, can spot trends, and NeurotransmitterSensory swelling neurons transferDendrites signals from the stimulatedit is possible sense to alter organs signalling to between nerve cells by using chemical Spinal cord the central nervous system (CNS). Motor neuronssubstances. transfer The signals most commonfrom are knownthe ‘electrical as anaesthetics; signal’ such cannot run helpdirectly others into plan the relevant target services cell. where they are needed aroundThe HRB funds research into a wide range of areas. Our funded the country. the CNS to the muscles and glands initiating asubstances response can to bea stimulus.used for pain-relief and the restoration of mental researchers study diseases like diabetes, cancer and Parkinson’s Axon health, while others, if abused or mis-administered,The arrival can of havea signal, serious called an impulse, triggers the release of special terminals Interneurons relay signals between the motor and sensory neurons. Health research can provide a rich, varied and stimulatingdisease. In Parkinson’s disease we are studying ways to grow Cell body health consequences. chemicals into the gap. These career.chemicals, Health neurotransmittersresearchers can have, adiffuse background in nursing, Axon across the gap locking into the socialreceptor science, molecules maths, medicine, in the computers,target cell chemistry, physicsnerve cells outside the body which could then be transplanted The motor and sensory neuronsNucleus are specialisedIt foris essential rapid, longthat the distance, lines of communication between the brain and or biology. back into the body. This is just one of our projects on the central direct communication. They have three majormuscle functions tissue remain– to intactreceive to permit manymembrane, important body causing functions. it to ‘switch on’. It switches off when no more Node of neurotransmitters are released and those that were previously released nervous system. Brain Ranwier signals, transmit signals quickly over a long distanceNerve impulsesand transfer pass tosignals and from the spinal cord along the axons of D sensory and motor neurons in the 31 pairshave of spinal been nerves broken; each downnerve by an enzyme in the gap. The broken down Cell body to the target cell. IRECTION OF IMPULSE More information about the HRB can be found at ourIn addition to funding research, we also carry out our own can be compared with a thick telephone cable with many thousands of neurotransmitters are then reabsorbedwebsite intowww.hrb.ie the synaptic or www.sta.ie. knob. research in areas such as mental health, child health and drug Nucleus Axon wires (axons) in separate bundles.

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