The peripheral nervous system.docx

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Biological Sciences
BIO 121
Jason Ramsay

The peripheral nervous system -Afferent:  Somatic sensory portion: monitors skeletal muscles and joints  Visceral sensory portion: monitors smooth muscles, cardiac muscle and other internal organs. -Efferent:  Somatic motor: controls skeletal muscle contraction  Visceral motor (autonomic): controls internal  The autonomic nerves can be further subdivided to form:  Parasympathetic nerves: cause pupil constriction, decrease heart rate, and tense the urinary bladder  Sympathetic nerves: cause pupil dilation, increase heart rate, and relax urinary bladder. Neural tissue consists of two cell types: 1. Neurons: nerve cells that are responsible for the transfer and processing of information in the nervous system. Consist of soma, axon, and dendrites. 2. Neuroglia: supporting cells & protect the neuron Functions of Neuroglia 1. Provide the framework for the neural tissue 2. Maintain the intercellular environment 3. Act as phagocytes  Over one billion  Roughly Types of Neuroglia  Astrocytes: in the CNS  Have the large number of cytoplasmic processes  Control the chemical content of the interstitial environment  Maintain the blood-brain barrier.  Oligodendrocytes: CNS  Cytoplasmic extensions contact the soma and axons  Cytoplasmic extensions tie axons together in a sheath of myelin  Microglia  Phagocytic cells  Protect the neuron by removing waste and debris  Ependymal cells  Line the ventricles of the brain  Line the central canal of the spinal cord  Monitor the CSF (cerebral spinal fluid)  Some of the ependymal cells secrete CSF  Satellite cells  regulate the exchange of material between the cell body and the environment  Schwann cells  Also called neurolemmocytes  Form the myelin sheath Details of Neuron Structure -Axon (nerve fiber) consists of: o Axon hillock area o Axoplasm o Axon vesicles containing neurotransmitters -Dendrites: stimulated by environmental changes or the activities of the other cells -Cell body: contains the nucleus, mitochondria, ribosomes, and other organelles and inclusions. -Axons: conduct nerve impulse (action potential) toward synaptic terminals. -Terminal boutons: affect another neuron or effector organ (muscle or gland) 1. Synapses with another neuron 2. Neuromuscular synapses 3. Neuroglandular synpases -Nissl bod
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