BSCI201 Final Review Sheet The Nervous System CNS and PNS Nissl body specialized ER that synthesizes protein Neurofilaments intermediate filaments within neuron cell bodies Ganglia cluster of cell bodies outside the CNS o Neuron cell bodies are sometimes found here Nuclei clusters of cell bodies within the CNS Tracts formed by neuron fibers running through the CNS made of white matter Nerve bundle of axons within the PNS Axon terminals ends of axons where neurotransmitters are stored o Generate and conduct nerve impulses Neurilemma part of the Schwann cell external to the myelin sheath o Houses the nucleus and cytoplasm Nodes of Ranvier gaps in the myelin sheath Endoneurieum within a nerve each fiber is surrounded by a delicate connective tissue sheath o Wraps individual axons Perineurium CT that wraps around fascicles Epineurium all fascicles are bound by this white fibrous CT o Wrapping nerve tract Which part of the neuron is known as the o Biosynthetic center and why Cell body because it s the central mass of a neuron which the axons and dendrites attach to It contains the nucleus and other organelles o Receptive center and why Dendrite because they have receptors for neurotransmitters released by other neurons They receive and convey signals to the cell body o Conducting region and why Axons because it s the part that carries away from the nerve cell body It generates and transmits signals away from the cell body o Secretory region and why Axon terminal because vesicles are released from the axon terminal via exocytosis It secretes neurotransmitters Name and describe the function of all 6 types of supporting cells o Microglia ingest and destroy foreign matter o Oligodendrocytes myelinate the extensions of the neurons o Astrocytes control the chemical environment around neurons facilitate capillary nerve exchanges o Ependymal Cells circulate cerebrospinal fluid o Schwann Cells myelinate the extensions of the neurons o Satellite Cells surround cell body of the neuron Explain why myelinated axons in the CNS don t regenerate when severed o Oligodendrocyte cells don t regenerate because there is no neurilemma to guide the growth of severed axons o Presence of growth inhibiting proteins in the CNS inhibit regeneration of a Explain why impulses are conducted faster in a larger myelinated axon than in a severed axon smaller unmyelinated axon o Large axons transmit impulses at a faster rate because they have a larger diameter so there is less resistance impulse transmissions o Smaller axons have higher resistance which impeded the impulse o Myelinated axons transmit impulses at a faster rate because they use transmissions saltatory conduction Action potentials are generated at Nodes and the impulse jumps from node to node down the axon o Unmyelinated axons use continuous conduction The action potential develops stepwise across axolemma Describe o Depolarization phase of an action potential The neuron is activated by a stimulus of appropriate intensity The sodium gates open in the membrane and sodium ions move into the cell down the concentration gradient The interior of the cell becomes less negative and eventually positive depolarization Depolarization occurs when the charge across the plasma membrane reverses from a negative to a positive charge o Repolarization phase of an action potential When the action potential is reached meaning the threshold potential is reached potassium gates open allowing potassium ions to move out of the cell down their concentration gradient This is when the membrane repolarizes reestablishing the concentration gradients of the RMP What are the absolute and relative refractory periods in an action potential o Absolute refractory periods occurs when the sodium gates are still open and the neuron is unable to initiate a new action potential o Relative refractory period when the neuron is undergoing repolarization and therefore sodium gates are closed an exceptionally strong stimulus can initiate another action potential Name and describe 3 structural classes of neurons o Unipolar o Bipolar A single process extending from the cell body which conducts impulses towards the CNS divided into peripheral and central processes Two processes attached to the cell body consisting of one dendrite and one axon found only in the eye ear and olfactory mucosa o Multipolar Many processes issued from the cell body consisting of one axon and many dendrites and is the most abundant type of neuron in the cell body Name and describe 3 functional classes of neurons o Sensory neurons afferent carry impulses from the sensory receptors o Motor neurons efferent carry impulses away from CNS to organs muscles towards the CNS and glands o Association neurons interneurons conduct impulses within the CNS Name and describe 3 types of nerve fibers which type has the fastest conduction velocity and why o Group A fibers have the largest diameter and heavily myelinated Motor neurons Fastest conducting velocity because its based on the diameter and degree of myelination o Group B fibers intermediate diameter and lightly myelinated Preganglionic autonomic fibers o Group C fibers small diameter and unmyelinated Postganglionic autonomic fibers The brain Name the 4 protective structures of the brain o Cranium o Meninges Bony helmet composed of 8 cranial bones 3 connective membranes surrounding the brain o Cerebrospinal fluid Located in the ventricles and in the subarachnoid space between arachnoid mater and pia mater It s found inside and outside of the brain acting as a liquid cushion providing buoyancy to the brain o Blood brain barrier A selective barrier that prevents harmful substance in blood from crossing to the brain Name and describe the 3 meninges o Dura mater outermost tough meninges Periosteal layer outer layer that is attached to the inner surface of the cranium Meningeal layer inner layer that projects into fissures it s continuous with the dura mater of the spinal cord o Arachnoid mater middle of the three Very delicate and net like Spreads over the CNS o Pia mater innermost layer of the 3 Very thin and highly vascularized Follows all contours of the brain surface Helps nourish brain and spinal cord Septum pellucidum separates the lateral ventricles of the cerebral cortex Interventricular foramen where the cerebrospinal fluid circulates through as it goes from the two lateral ventricles to the third ventricle Cerebral aqueduct what the cerebrospinal fluid moves through as it goes
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