Review Sheet Final The Nervous System CNS and PNS 1 Define the following Nissl body neurofilaments ganglia nuclei tract nerve axonal terminals neurilemma nodes of Ranvier endoneurium 12 07 2010 perineurium epineurium Nissl body Neurofilaments Ganglia Nuclei Tract nerve Axon terminals Neurilemma Nodes of Ranvier Endoneurium Perineurium Epineurium a biosynthetic center Cell body b receptive center Dendrites 2 Which part of a neuron is known as the 3 Name and describe the function of all 6 types of supporting cells Supporting cells neuroglia Four supporting cells are located in the CNS o Astrocytes Most abundant Numerous extensions that wrap around neurouns Involved in forming the blood brain barrier a selective barrier that regulates the chemicals environment of the brain Regulate brain function o Microglia Since the specific immune system does not have access to the CNS the microglia act as macrophages to engulf destroy pathogens and cell debris o Ependymal cells Ciliated columnar cells that line the ventricles cavities in the brain that contain cerebrospinal fluid CSF Currents created by beating of cilia circulate the CSF o Oligodendrocytes Their extensions myelinate axons of neurons in the CNS Two supporting cells are located in the PNS o Schwann cells neurolemmocytes Myelinate axons of neurons in the PNS o Satellite cells Surround cell bodies of neurons and control their chemical environment 4 Explain why myelinated axons in the CNS do not regenerate when severed complete The microglia poorly clean up area of damage debridement is not No neurilemma guide growth of severed axon Presence of growth inhibiting proteins in the CNS inhibit regeneration of a severed axon 5 Explain why impulses are conducted faster in a larger myelinated axon than in a smaller unmyelinated axon Myelinated axons use salutatory conduction where action potentials are generated only at the nodes of ranvier hence the impulse jumps from node to node down the axon Unmyelinated axons use continuous conduction where action potentials developed stepwise across the entire axolemma 6 Describe the a depolarization phase of an action potential entry of sodium ions sodium influx makes membrane potential less and less negative phenomenon o Threshold potential action potential develops an all or none o Upshoot or spike due to an explosive entry of sodium ions a positive membrane potential reached b repolarization phase of an action potential sodium channels close and potassium channels open and potassium ions rush out potassium efflux and reversal of membrane potential toward a negative membrane potential 7 What are the absolute and relative refractory periods in an action potential Absolute refractory period the depolarization phase of the action potential when sodium channels are opened another action potential cannot be generated Relative refractory period the repolarization phase of the action potential when the sodium channels are closed potassium channels are open an exceptionally strong stimulus can cause sodium channels leading to depolarization and the generation of another action potential 8 Name and describe the 3 structural classes of neurons Multipolar neuron has at least three processes one axon and at least two dendrites most abundant neuron in the human body Bipolar neuron has two processes one axon and one dendrites Unipolar neuron has one short process from the cell body and it bifurcates into a central process and a peripheral process 9 Name and describe the 3 functional classes of neurons Motor or efferent neuron transmits impulses away from the CNS to effector organs glands organs Sensory or afferent neuron transmits impulses from sensory receptors toward the CNS Association neurons or interneuron located in the CNS between the sensory neurons and the motor neurons Most of the neurons 99 in the body are associated neurons 10 Name and describe the 3 categories types of nerve fibers which type has the fastest conduction velocity and why Group A fibers have the largest diameter and heavily myelinated transmit impulse at the rate of 150 m s 300 miles per hour Group B fibers intermediate diameter and lightly myelinated transmit impulses at a rate of 15 m s Group C fibers smallest diameters and unmyelinated transmit impulses at a rate of 1 m s 12 07 2010 The Brain 1 Name the 3 structures protecting the brain Cranium bony helmet composed of the 8 cranial bones frontal parietal paired temporal paired occipital sphenoid ethmoid bones Meninges three connective membranes surrounding the brain o Dura mater outermost meninx double layered outer periosteal layer lining the internal surface of the cranium and the inner meningeal layer separated from the underlying arachnoid mater by the sudural space o Arachnoid mater middle meninx separated from the underlying pia mater by the subarachnoid space weblike extensions from the arachnoid mater to the subarachnoid space gives this meninx its name Arachnida spider family o The subarachnoid space contains CSF o Pia mater innermost meninx that clings to the surface of the Cerebrospinal fluid CSF filtered from blood located in the ventricles and also in the subarachnoid space hence CSF is found inside and outside of the brain acting as a liquid cushion provided buoyancy to the brain provides nutrients removes metabolic brain wastes Blood brain barrier a selective barrier that prevents harmful substance in blood from crossing to the brain 2 Name and describe the 3 meninges Dura mater outermost meninx double layered outer periosteal layer lining the internal surface of the cranium and the inner meningeal layer separated from the underlying arachnoid mater by the sudural space Arachnoid mater middle meninx separated from the underlying pia mater by the subarachnoid space weblike extensions from the arachnoid mater to the subarachnoid space gives this meninx its name Arachnida spider family The subarachnoid space contains CSF Pia mater innermost meninx that clings to the surface of the brain 3 Give the function of the CSF filtered from blood located in the ventricles and also in the subarachnoid space hence CSF is found inside and outside of the brain acting as a liquid cushion provided buoyancy to the brain provides nutrients removes metabolic wastes 4 Define the following septum pellucidum interventricular foramen cerebral aqueduct Give the locations of the lateral third and fourth ventricles Septum pelluciudum a thin median membrane Interventricular foramen channel in
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