Nervous Tissue - S&E
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Created by:
karenyan1203 on February 14, 2012
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38 terms
Terms | Definitions |
|---|---|
 CNS | Brain and spinal cord enclosed in bony coverings |
| PNS | nerve = bundle of axons in connective tissue |
| Sensory (afferent) divisions | Going to CNS |
| Motor (efferent) divisions | CNS to effectors that divides into the ANS and Somatic motor division |
| Sensory (afferent) neurons | Detect changes in body and external environment Info transmitted into brain or spinal cord |
| Interneurons | Most abundant, bring info between afferent and motor, connect afferent and efferent |
| Motor (efferent) neuron | Sends signals out to muscles and gland cells |
| Excitability (irritability) | Ability to respond to changes in the body and external environment called stimuli Respond electrically |
| Cell body | Perikaryon = soma Single, central nucleus with large nucleolus, cytoskeleton of microtubules and neurofibrils |
| Dendrites | Projections for receiving signals |
| Axon | Arising from axon hillock for rapid conduction |
| Oligodendrocyte | Form myelin sheaths ONLY in CNS |
| Ependymal cells | produce CSF (cerebral spinal fluid) |
| Microglia | (macrophages) formed from monocytes |
| Neuroglial Cells | support cells for neurons |
| Neuroglial tumor | Brain cancer |
| Astrocytes | Most abundant glial cells - contribute to Blood Brain Barrier (BBB) and regulate composition of brain tissue fluid |
| Schwann | Cells make myelin in the PNS |
| Node of Ranvier | Gaps between myelin segments |
| Trigger Zone | Initial segment (area before 1st schwann cell) and axon hillock |
| Speed of Nerve Signals | Large, myelinated fibers > small, myelinated fibers > small, unmyelinated fibers |
| Regeneration of Peripheral Nerves | Occurs if soma and neurilemmal tube is intact |
| Types of Nerve Injury | 1. Laceration 2. Evulsion - worst prognosis 3. Compression - Best prognosis |
| Resting Membrane Potentials | ~-70mV inside the cell comparing to outside the cell - electrolytes such as Na+ and K+ pump in/out to maintain the equilibrium |
| Local Potentials | 1. Occurs on a part of the neuron when that part has been stimulated 2. They are graded and decremental (it gets weaker as spread out more) 3. Reversible, work like a dimer |
| Action Potentials | Electrical information found on axon, only be found within an axon and it will only occur if that trigger zone said it should occur |
| Characteristics of AP | 1. All-or-nothing 2. Always be the same, if it occurs, it occurs all the way like a light switch 3. Irreversible |
| Absolute Refractory period | Axon cannot have another action potential |
| Relative Refractory period | Action potential/axon can make another action potential, but the stimulus for that to occur has to be greater than normal |
| Purpose of Refractory Period | Preventing back-fire of the conduction, so the electrical msg only go down one direction |
| Saltatory Conduction | Myelinated fibers insulate the fibers, make the skips down, only the nodes of Ranvier conduct down |
| Neuron use other chemicals as neurotransmitters | Acetylcholine Amino acid neurotransmitters Monoamines Neuropeptides |
| Excitatory postsynaptic potentials neurotransmitters | Glutamate and Asparate Increase the mV |
| Inhibitory postsynaptic potentials | GABA and Glycine Decrease the mV |
| Temporal Summation | Single synapse receives many ESPS's in short time |
| Spatial Summation | Single synapse receives many EPSP's from many cells |
| Converging circuit | Taking msg from a whole lot different nerve cells and stimulate the axon hillock |
| Diverging circuit | Same nerve cells spreads out to many different nerves |
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