Lesson 16 1 How is the gray matter and white matter arranged in the spinal cord What are the functions of the white columns and gray horns Where are the enlargements of the spinal cord located and why are they enlarged there Gray matter Surrounds central canal of spinal cord transports CSF Contains neuron cell bodies neuroglia unmyelinated axons Has projections gray horns Covered by a thick layer of white matter 1 The gray horns a Posterior gray horns contain somatic and visceral sensory nuclei b Anterior gray horns contain somatic motor nuclei c Lateral gray horns are in thoracic and lumbar segments contain visceral motor nuclei a Axons that cross from one side of cord to the other before reaching 2 Gray commissures gray matter 1 The cell bodies of neurons form functional groups called nuclei remember cell body groups in PNS called are called ganglia a Sensory nuclei Dorsal posterior Connect to peripheral receptors b Motor nuclei Ventral anterior Connect to peripheral effectors 2 Sensory or motor nucleus location within the gray matter determines which body part it controls White matter Superficial Contains myelinated axons Consists of ascending and descending axons Organized in columns Contains axon bundles with specific functions 1 Posterior white columns lie between posterior gray horns and posterior median sulcus median fissure 2 Anterior white columns lie between anterior gray horns and anterior 3 Anterior white commissure area where axons cross from one side of 4 spinal cord to the other Lateral white columns located on each side of spinal cord between anterior and posterior columns 5 Tracts or fasciculi are bundles of axons in the white columns Relay same information in same direction a Ascending tracts Carry information to brain b Descending tracts Carry motor commands to spinal cord Enlargements of the Spinal Cord are caused by Amount of gray matter in segment Involvement with sensory and motor nerves of limbs o Cervical enlargement Nerves of shoulders and upper limbs o Lumbar enlargement Nerves of pelvis and lower limbs 2 What is the difference between the ventral and dorsal root What type of information do they carry Two branches of spinal nerves 1 Ventral root Contains axons of motor neurons 2 Dorsal root Contains axons of sensory neurons 3 Describe the organization of the meninges surrounding the spinal cord What happens in meningitis Injections of anesthesia occur between which meningeal layers Spinal Meninges Continuous with cranial meninges o Specialized membranes isolate spinal cord from surroundings Functions of the spinal meninges include Protecting spinal cord Carrying blood supply deliver O2 and nutrients The Three Meningeal Layers Protecting spinal cord Carrying blood supply o Dura mater Outer layer of spinal cord o Arachnoid mater Middle meningeal layer Tough and fibrous Cranially Fuses with periosteum of occipital bone Is continuous with cranial dura mater Caudally inferiorly Tapers to dense cord of collagen fibers Joins filum terminale in coccygeal ligament Subdural space Between arachnoid mater and dura mater Subarachnoid space Between arachnoid mater and pia mater Contains collagen elastin fiber network arachnoid trabeculae extends to filum terminale Filled with cerebrospinal fluid CSF o Pia mater Inner meningeal layer Is a mesh of collagen and elastic fibers Is bound to underlying neural tissue Blood vessels serving the spinal cord run along surface of spinal pia mater within the subarachnoid space Meningitis Viral or bacterial infection of meninges o Spinal meninges or cerebral meninges o Can disrupt CSF flow damage or kill neurons and neuroglia 4 What is a spinal nerve Is it a mixed nerve How are spinal nerves formed from the spinal cord What happens to the spinal nerve distal to the spinal cord Which rami perform which functions What are the body areas that they serve called Located on each side of spine Dorsal and ventral roots join to form a spinal nerve Carry both afferent sensory and efferent motor fibers Spinal Nerve Mixed Nerve There are 31 pairs of spinal nerves each identified by its association with adjacent vertebrae Motor nerves o Dorsal ramus Contains somatic and visceral motor fibers Innervates the back o Ventral ramus Larger branch Innervates ventrolateral structures and limbs 5 How are spinal nerves protected by connective tissue Every spinal nerve is surrounded by three connective tissue layers that support structures and contain blood vessels Layers o Epineurium Outer layer Dense network of collagen fibers o Perineurium Middle layer Divides nerve into fascicles axon bundles o Endoneurium Inner layer Surrounds individual axons 6 What causes shingles How is the chicken pox virus involved painful rash caused by chicken pox herpes virus that travels to the dermatome served Shingles by the affected sensory nerve Virus stays dormant after chicken pox infection Virus remains dormant in neurons of anterior gray horns Bilateral region of skin Monitored by specific pair of spinal nerves Dermatome 7 What are the four major plexuses of the ventral rami Nerve Plexus Complex interwoven networks of nerve fibers Formed from blended fibers of ventral rami of adjacent spinal nerves Control skeletal muscles of the neck and limbs Cervical plexus supplies head neck upper shoulder major nerve phrenic nerve C3 5 controls diaphragm Brachial plexus supplies pectoral girdle upper limbs Lumbar plexus supplies anterolateral abdominal wall genitals lower limbs Sacral plexus supplies buttocks perineum lower limbs 8 What are the five patterns of neural circuits in neuronal pools Which functions do these neural a Spreads stimulation to many neurons or neuronal pools in CNS visual info goes to visual cortex and postural balance areas a Brings input from many sources to single neuron subconscious and conscious control of a Moves information in single line relay of pain info a Moves same information along several paths simultaneously step onto nail you withdraw foot shift weight feel pain and scream 5 Reverberation a Positive feedback mechanism b Functions until inhibited c May help maintain consciousness muscle coordination and normal breathing circuits perform 1 Divergence 2 Convergence breathing 3 Serial processing 4 Parallel processing Lesson 17 these reflexes classified 1 What are the components of the reflex arc What are the five steps in a neural reflex How are Reflex Arc The wiring of a single reflex o Beginning at receptor o Ending at peripheral effector
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