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 application to patient management. 1.1.6 D...

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 application to patient management. 1.1.6 Describe relevant and appropriate physiology and explain its application to patient management Intended Learning Outcomes including Part 2 Students will be able to: List the characteristics of nervous tissue List and describe the cells of nervous tissue Explain the mechanism by which impulses are generated and their relevance in dentistry The Nervous System The nervous system detects and responds to changes inside and outside the body. Together with the endocrine system it controls important aspects of body function and maintains homeostasis. Nervous system stimulation provides an immediate response while endocrine activity 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 Peripheral Nervous System Sensory division Motor division – voluntary- somatic nervous system - involuntary-autonomic nervous system / \ sympathetic parasympathetic / \ fight or flight rest and digest Nervous Tissue Cells of the nervous system Neurones Schwann Cells Neuroglial/Glial Cells Neurones Key Features 1. Cell body 2. Axon 3. Schwann Cells 4. Nodes of Ranvier 5. Dendrites 6. Synaptic end bulb Cell Body  Axons Communication 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)  Schwann Cells Wrapped around axon so there are layers of Schwann cell Mainly provide myelin insulation to axons in the peripheral nervous system MYELIN SHEATH: High phospholipid (fatty) content offers electrical insulation Nodes of Ranvier Exposed areas between the Schwann Cells Assist rapid transmission of action potentials in myelinated neurones. Dendrites Extensions of the cell body Provide a large surface area to receive information 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 Properties of Neurones Irritability – ability to initiate nerve impulses in response to stimuli from either inside the body or outside. Conductivity- ability to transmit an impulse. 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 continue to replicate throughout life. These are; Microglia Astrocytes Oligodendrocytes  MICROGLIA- are found mainly in the area of blood vessels. They enlarge and become phagocytic in areas of inflammation and cell destruction. ASTROCYTES- form the main supporting tissues of the central nervous system. Star shaped with fine 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 fibres in the CNS. They form and maintain myelin and have the same function as Schwann cells in the peripheral nerves. Blood-brain barrier Is a selective barrier that protects the brain from potentially toxic substances and chemical variations in the blood eg: after 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 Synaptic End Bulbs Important for nerve impulse conduction from one neurone to another or neurone to an effector Contain enclosed sacs called synaptic vesicles These store neurotransmitters Synapse Pre-synaptic neurone Pre-synaptic knob Neurotransmitters – acetylcholine/noradrenaline Calcium Mitochondria Neurotransmitter receptors Post-synaptic knob Post-synaptic neurone Neuro-transmission Break time!