医学英语中枢神经系统分析报告.ppt

Nervous System- CNS part 1 Study Guide SUMC 2011-212 The Meninges and Cerebrospinal Fluid * /group/hopes/cgi-bin/wordpress/2010/06/the-hopes-brain-tutorial-text-version/ For further reading please see following webpage: One way to classify neurons is by the number of extensions that extend from the neurons cell body (soma). Bipolar neurons have two processes extending from the cell body (examples: retinal cells, olfactory epithelium cells). Pseudo-uni-polar cells (example: dorsal root ganglion cells). Actually, these cells have 2 axons rather than an axon and dendrite. One axon extends centrally toward the spinal cord, the other axon extends toward the skin or muscle. Multipolar neurons have many processes that extend from the cell body. However, each neuron has only one axon (examples: spinal motor neurons, pyramidal neurons, Purkinje cells). Types of neurons. Neurons can also be classified by the direction that they send information: Sensory (or afferent) neurons: send information from sensory receptors (e.g., in skin, eyes, nose, tongue, ears) TOWARD the central nervous system. Motor (or efferent) neurons: send information AWAY from the central nervous system to muscles or glands. Interneurons: send information between sensory neurons and motor neurons. Most interneurons are located in the central nervous system. Types of neurons. A single neuron consist of: CELL BODY: is the metabolic center of the neuron, contains the Nucleus and Mitochondrion. DENDRITES: convey incoming messages to the cell body. AXON HILLOCK: a cone like region from where an axon arises. AXONS: generates nerve impulses and topically conduct them away from the cell body. A nerve is a group of axons”. Presynaptic terminals: The swollen, distal end of an axon; contains a neurotransmitter substance within synaptic vesicles. Also called synaptic ending. Axons Take information away from the cell body Smooth Surface Generally only 1 axon per cell No ribosomes Can have myelin Branch fu