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EXAM 4 STUDY BUNDLE Learning Outcomes Lesson 16 The Spinal Cord and Spinal Nerves 13 1 Describe the basic structural and organizational characteristics of the nervous system efficiently o The nervous system is highly organized which allows for it to function o Involves the spinal cord spinal nerves and spinal reflexes 13 2 Discuss the structure and functions of the spinal cord and describe the three meningeal layers that surround the central nervous system o The spinal cord has bilateral symmetry and is divided by grooves the posterior median sulcus and anterior median fissure o Spinal enlargements are caused by the amount of gray matter in a spinal segment which is due to the involvement of sensory and motor neurons of limbs The cervical enlargement is associated with the nerves of the shoulders and upper limbs The lumbar enlargement is associated with nerves of the pelvis and lower limbs o The conus medullaris is the thin conical spinal cord below lumbar enlargement The filum terminale is a thin thread of fibrous tissue at end of conus medullaris that attaches to coccygeal ligament The filum terminale is an important structure because it provides longitudinal support to the spinal cord Nerve roots ventral and dorsal extending below conus medullaris and into sacrum is the cauda equine o The spinal cord is divided into a total of 31 segments based on vertebrae where spinal nerves originate which can change with age A cervical nerve is named for vertebra inferior to it All other nerves are named for superior vertebra o The two branches of the spinal nerves are the ventral and dorsal roots The ventral root contains motor neurons and the dorsal root contains sensory neurons Dorsal root ganglia contain the cell bodies of sensory neurons 1 EXAM 4 STUDY BUNDLE The cell bodies of motor neurons are located in the gray matter of the spinal cord o The spinal cord is isolated from it s surroundings by spinal meninges The main functions of the spinal meninges are protecting the spinal cord and carrying blood supply o The three meningeal layers are dura matter arachnoid matter and pia matter outer inner Dura matter is tough and fibrous outer layer of the spinal cord that fuses with the periosteum of the occipital bone and is continuous with cranial dura matter Caudally dura matter tapers to dense core or collagen fibers and joins filum terminale in coccygeal ligament The epidural space between the spinal dura matter and walls of vertebral canal contain loose connective tissue and adipose tissue acts as a protective padding This location is an anesthetic injection site to produce a local epidural block blocks local sensory nerves The arachnoid matter is the middle layer and it is composed of simple squamous epithelia and covers the outer surface of the arachnoid matter The subdural space is located between the arachnoid matter and dura matter The space between the arachnoid and pia matter is the subarachnoid space It contains a network of collagen elastin fibers that extends into the filum terminale This area is filled with CSF o CSF carries dissolved gases nutrients and wastes o A spinal tap is a procedure that withdraws spinal fluid from the subarachnoid space The pia matter innermost layer is a mesh of collagen and elastic fibers bound to underlying neural tissue Blood vessels run along the surface of pia matter within the subarachnoid space 2 EXAM 4 STUDY BUNDLE Paired denticulate ligaments are found on each side of the spinal cord They extend from the pia matter to dura matter to stabilize side to side lateral movement 13 3 Explain the roles of white matter and gray matter in processing and relaying sensory information and motor commands o Superficial white matter contains myelinated and unmyelinated axons White matter on each side of the spinal cord is divided into 3 columns posterior anterior and lateral white columns Posterior white columns lie between posterior gray horns and posterior median sulcus They re involved in proprioception fine touch ventral pressure and vibrations Anterior white columns lie between anterior gray horns and anterior median fissure This is the area where axons cross from one side of the spinal cord to the other Lateral white columns are located on each side of the spinal cord between the anterior and posterior columns Tracts fasciculi are bundles of axons in white columns that relay the same information in the same directions The ascending tracts carry information to the brain the descending tracts carry motor commands to the spinal cord o Gray matter surrounds the central canal of the spinal cord and contains neuroglial neuron cell bodies and unmyelinated axons The gray horns are projections of gray matter There are three types of gray horns posterior anterior and lateral The posterior gray horns contain somatic and visceral sensory nuclei The anterior gray horns contain somatic motor nuclei The lateral gray horns are located in the thoracic and lumbar segments and contain visceral motor nuclei Axons that cross from one side of the cord to the other before reaching gray matter are called gray commissures Nuclei are functional groups of neuronal cell bodies Sensory nuclei are dorsal and connect to peripheral receptors motor nuclei are ventral and connect to peripheral effectors 3 EXAM 4 STUDY BUNDLE The location of sensory or motor neurons within the gray matter determines which part of the body it controls 13 4 Describe the major components of a spinal nerve and relate the distribution pattern of spinal nerves to the regions they innervate o Each spinal cord is surrounded by three connective tissue layers that support structures and contain blood vessels The three layers are epineurium perineurium and endoneurium The epineurium is the outermost layer and consists of a dense network of collagen fibers The middle layer is the perineurium it divides nerves into fascicles axon bundles blood vessels found outside the fascicles The endoneurium in the inner most layer and it surrounds individual axons o The spinal nerves branch and interconnect to form peripheral nerves peripheral nerves are also surrounded by connective tissue o The peripheral distribution of spinal nerves Spinal nerve forms lateral to the intervertebral foramen where dorsal and ventral roots unite Then they branch to form pathways to it s final destination For motor neurons the first branch commnicans from the spinal nerve carries visceral motor fibers to sympathetic ganglion of the autonomic


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FSU BSC 2085 - The Spinal Cord and Spinal Nerves

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