Nervous System Part 1 PDF

Nervous System Part 1 Anatomy & Physiology of Nervous Tissue Tutor Debbie Hemington Module Biomedical Sciences  GDC Learning Outcomes 1.1.5 Describe relevant and appropriate dental, oral, craniofacial and general anatomy and explain their applica;on to pa;ent management. 1.1.6 Des...

Nervous System Part 1 Anatomy & Physiology of Nervous Tissue Tutor Debbie Hemington Module Biomedical Sciences  GDC Learning Outcomes 1.1.5 Describe relevant and appropriate dental, oral, craniofacial and general anatomy and explain their applica;on to pa;ent management. 1.1.6 Describe relevant and appropriate physiology and explain its applica;on to pa;ent management Intended Learning Outcomes including Part 2 Students will be able to: List the characteris;cs of nervous ;ssue List and describe the cells of nervous ;ssue Explain the mechanism by which impulses are generated and their relevance in den;stry  Major system The Nervous System muscies/organs/gland. The nervous system detects and responds to changes inside and outside the body. Together with the endocrine system it controls important aspects of body func;on and maintains homeostasis. Nervous system s;mula;on provides an immediate response while endocrine ac;vity is, in the main, slower and more prolonged. There are 2 divisions of the nervous system 1. Central nervous system (CNS) –brain & spinal cord 2. Peripheral nervous system (PNS) –all other nerves  Central nervous outside system Cranial or spinal nerves. Peripheral Nervous System - receptors (skin muscles organs) info from sensory , ,. ~ collects Sensory division + carries to central nervous system. movements voluntary Motor division – voluntary- soma;c nervous system - involuntary-autonomic nervous system > - I / \ outgoing ingo from sympathe;c parasympathe;c central nervous system fast / \ and delivers to acting Pght or Qight rest and digest muscle glands to control the motor functions. car towards brown caraway froma Nervous Tissue Cells of the nervous system Neurones Schwann Cells Neuroglial/Glial Cells  NERVE CELLS vast numbers ~ Neurones Single cell body with branching processes, most are receptive in function - Dendrites. One process leaving the cell - Axon/nerve fibre, carries information away from cell body. Information is passed between neurons through synapses — membranes of adjacent cells close together. Nerves - bundles of axons bound together. Can appear in different forms depending on location and function. Key Features 1. Cell body 2. Axon 3. Schwann Cells 4. Nodes of Ranvier 5. Dendrites 6. Synap;c end bulb  Grey matter of nervous system? Peripheral of brain and centre of spinal cord Well developed nucleus Many organelles Cell Body No mitotic apparatus - can’t be replaced but they can regenerate to certain extent.  Divides up into collaterals so info can be sent to different locations at same time. Myelin sheath acts as insulator Axons Communica;on route between cell body & axon terminals Conducts electrical impulses away from the neurone's cell body Longer than dendrites – can be longer than 1m!! Large axons & those of the peripheral nervous system are surrounded by a MYELIN sheath (series of Schwann cells)  ' Arrange along length of Axon and form Myelin sheath Every so often the myelin sheath has gaps called Nodes of ranvier Schwann Cells Wrapped around axon so there are layers of Schwann cell Mainly provide myelin insula;on to axons in the peripheral nervous system MYELIN SHEATH: High phospholipid (fa\y) content o]ers electrical insula;on  Right side - Myelinated nerve with nodes of ranvier - allows for rapid transmittion of nerve impules Nodes of Ranvier Exposed areas between the Schwann Cells Assist rapid transmission of ac;on poten;als in myelinated neurones. Dendrites Extensions of the cell body Provide a large surface area to receive informa;on to pass to the cell body Same structure as axons but shorter Plasma has dense chemical ion channels for impulse transmission Form synapses with other dendrites or terminate in specialised sensory receptors e.g. skin ProperJes of Neurones Or excitability Inside body - Change in carbon dioxide concentration in blood increases respiration rate. Irritability – ability to ini;ate nerve impulses in Outside body - touch or light waves or thought that results in voluntary movement. response to s;muli from either inside the body or outside. ConducJvity- ability to transmit an impulse. Neurone at rest has electrical potential - resting potential When stimulated or excited - brief reversal of polarity - action potential  Don’t have a role in information processing but perform many roles for normal functioning. Neuroglial cells- support network Three types of non-excitable glial (glue-like) cells support the neurones of the central nervous system. Unlike nerve cells, these con;nue to replicate throughout life. These are; Microglia Astrocytes Oligodendrocytes  MICROGLIA- are found mainly in the area of blood vessels. They enlarge and become phagocy;c in areas of inQamma;on and cell destruc;on. ASTROCYTES- form the main suppor;ng ;ssues of the central nervous system. Star shaped with Pne branching processes, they lie in a muccopolysaccharide ground substance. Found in large numbers adjacent to blood vessels. OLIGODENDROCYTES smaller then astrocytes and are found in clusters around the neurone cell wall, and adjacent to, and along the length of many myelinated nerve Pbres in the CNS. They form and maintain myelin and have the same func;on as Schwann cells in the peripheral nerves.  Astrocytes processes form a sleeve around blood vessels. Blood is separated arted from neurons by capillary wall and layer of astrocytes Selective and protective barrier Blood-brain barrier Is a selec;ve barrier that protects the brain from poten;ally toxic substances and chemical varia;ons in the blood eg: acer a meal. Oxygen, carbon dioxide, glucose and other lipid soluble substances such as alcohol quickly cross the barrier into the brain. Some large molecules, many drugs, inorganic ions and amino acids pass more slowly or do not pass at all from the blood to the brain SynapJc End Bulbs Important for nerve impulse conduc;on from one neurone to another or neurone to an e]ector Contain enclosed sacs called synapJc vesicles ↑ These store neurotransmiPers  Space between one neurone and another - synaptic cleft ALWAYS more than one nerve involved in its transmission of nerve impulses from origin to destination Synapse No physical contact but there is a synapse. Pre-synap;c neurone Pre-synap;c knob Neurotransmi\ers – acetylcholine/noradrenaline Calcium Mitochondria Neurotransmi\er receptors Post-synap;c knob Post-synap;c neurone