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1、Nervous System- CNS part 1Study GuideSUMC 2011-212For further reading please see following webpage:One way to classify neurons is by the One way to classify neurons is by the number of extensionsnumber of extensions that extend from the that extend from the neurons cell body (soma).neurons cell body
2、 (soma). Bipolar neuronsBipolar neurons have two have two processes extending from processes extending from the cell body (examples: the cell body (examples: retinal cells, olfactory retinal cells, olfactory epithelium cells).epithelium cells). Pseudo-uni-polar cellsPseudo-uni-polar cells (example:
3、dorsal root (example: dorsal root ganglion cells). Actually, ganglion cells). Actually, these cells have 2 axons these cells have 2 axons rather than an axon and rather than an axon and dendrite. One axon dendrite. One axon extends centrally toward extends centrally toward the spinal cord, the other
4、 the spinal cord, the other axon extends toward the axon extends toward the skin or muscle.skin or muscle. Multipolar neuronsMultipolar neurons have have many processes that many processes that extend from the cell body. extend from the cell body. However, each neuron has However, each neuron has on
5、ly one axon (examples: only one axon (examples: spinal motor neurons, spinal motor neurons, pyramidal neurons, pyramidal neurons, Purkinje cells).Purkinje cells). Types of neurons.Types of neurons.Neurons can also be classified by Neurons can also be classified by the the direction that they send di
6、rection that they send information:information:Sensory (or afferent) neurons:Sensory (or afferent) neurons: send information from sensory send information from sensory receptors (e.g., in skin, eyes, nose, receptors (e.g., in skin, eyes, nose, tongue, ears) tongue, ears) TOWARDTOWARD the central the
7、 central nervous system. nervous system. Motor (or efferent) neurons:Motor (or efferent) neurons: send send information information AWAYAWAY from the central from the central nervous system to muscles or glands. nervous system to muscles or glands. Interneurons:Interneurons: send information send in
8、formation between between sensory neuronssensory neurons and and motor motor neuronsneurons. Most interneurons are located . Most interneurons are located in the central nervous system.in the central nervous system. Types of neurons.Types of neurons. A single neuron consist of:A single neuron consis
9、t of: CELL BODYCELL BODY: is the metabolic center of the : is the metabolic center of the neuron, contains the Nucleus and neuron, contains the Nucleus and Mitochondrion.Mitochondrion. DENDRITESDENDRITES: convey incoming messages to : convey incoming messages to the cell body.the cell body. AXON HIL
10、LOCKAXON HILLOCK: a cone like region from : a cone like region from where an axon arises.where an axon arises. AXONSAXONS: generates nerve impulses and : generates nerve impulses and topically conduct them away from the cell topically conduct them away from the cell body. A nerve is a group of axons
11、”.body. A nerve is a group of axons”. Presynaptic terminals: Presynaptic terminals: The swollen, distal The swollen, distal end of an axon; contains a neurotransmitter end of an axon; contains a neurotransmitter substance within synaptic vesicles. Also substance within synaptic vesicles. Also called
12、 synaptic ending.called synaptic ending.AxonsAxons Take information away Take information away from the cell body from the cell body Smooth Surface Smooth Surface Generally only 1 axon per Generally only 1 axon per cell cell No ribosomes No ribosomes Can have myelin Can have myelin Branch further fr
13、om the Branch further from the cell bodycell body DendritesDendritesn nBring information to the Bring information to the cell body cell body n nRough Surface (Rough Surface (dendriticdendritic spines) spines) n nUsually many dendrites Usually many dendrites per cell per cell n nHave Have ribosomesri
14、bosomes n nNo No myelin insulationmyelin insulation n nBranch near the cell bodyBranch near the cell bodyThere are several differences between axons and There are several differences between axons and dendrites:dendrites:NEUROGLIAL cells - there are six types of supporting cells; four in the CNS and two in the PNSThe Meninges and Cerebrospinal Fluid
