Lesson 16 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 White matter is superficial and contains mylenated axons white appearance Contains white columns Posterior white columns lie between posterior gray horns and posterior median sulcus Anterior white columns lie between anterior gray horns and anterior median fissure o Anterior white commissure area where axons cross from one side of spinal cord to the other Lateral white columns located on each side of spinal cord between anterior and posterior columns Grey matter surround the central canal of the spinal cord contains neural cell bodies neuroglia and unmyelinated axons Also contains gray horns Posterior gray horns contain somatic and visceral sensory nuclei Anterior gray horns contain somatic motor nuclei Lateral gray horns are in thoracic and lumbar segments contain visceral motor nuclei 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 What is the difference between the ventral and dorsal root What type of information do they carry Ventral root contains axons of motor neurons Dorsal root contains axons of sensory neurons Describe the organization of the meninges surrounding the spinal cord What happens in meningitis Injections of anesthesia occur between which meningeal layers 3 Spinal Meningeal Layers continuous with cranial meninges 1 Dura mater Outer layer of spinal cord 2 Arachnoid mater Middle meningeal layer 3 Pia mater Inner meningeal layer Meningitis Viral or bacterial infection of meninges o Can disrupt CSF flow damage of kill neurons and neuroglia Spinal anesthesia Injection of local anesthetics between the pia mater and arachnoid mater subarachnoid space spreads as CSF distributes along spinal cord o Spinal taps also occur at subarachnoid space 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 Every spinal cord segment is connected to a pair of spinal nerves o Every spinal nerve is surrounded by three connective tissue layers that support structures and contain blood vessels o Form lateral to the intervertebral foramen at the foramen the dorsal and ventral roots unite then branch and form pathways to destination Dorsal ramus Ventral ramus Contains somatic and visceral motor fibers Innervates the back Larger branch Innervates ventrolateral structures and limbs o In addition to motor impulses dorsal and ventral rami also carry sensory information How are spinal nerves protected by connective tissue There are 3 layers of connective tissue that protect the spinal nerve 1 Epineurium Outer layer Dense network of collagen fibers 2 Perineurium Middle layer Divides into fascicles axon bundles 3 Endoneurium Inner layer Surrounds individual axons What causes shingles How is the chicken pox virus involved Shingles painful rash caused by chicken pox herpes virus that travels to the dermatome bilateral region of skin served by the affected sensory nerve Virus stays dormant after pox infection o Virus remains dormant in neurons of anterior gray horns What are the four major plexuses of the ventral rami Nerve Plexuses o Complex interwoven networks of nerve fibers o Formed from blended fibers of ventral rami of adjacent spinal nerves o Control skeletal muscles of the neck and limbs Four main Plexuses of Ventral Rami 1 Cervical plexus supplies head neck upper shoulder major nerve phrenic nerve C3 5 controls diaphragm 2 Brachial plexus supplies pectoral girdle upper limbs 3 Lumbar plexus supplies anterolateral abdominal wall genitals lower limbs 4 Sacral plexus supplies buttocks perineum lower limbs What are the five patterns of neural circuits in neuronal pools Which functions do these neural circuits perform Neuronal Pools o Functional groups of interconnected neurons interneurons o Each with limited input sources and output destinations o May stimulate or depress parts of brain or spinal cord 5 Patterns of Neural Circuits in Neuronal Pools 1 Divergence o Spreads stimulation to many neurons of neuronal pools in CNS visual info goes to visual cortex and postural balance areas 2 Convergence o Brings input from many sources to single neuron subconscious control of breathing o Moves information in single line relay of pain 3 Serial processing info 4 Parallel processing o Moves same information along several paths simultaneously step onto nail you withdraw foot shift weight feel pain and scream 5 Reverberation o Positive feedback mechanism o Functions until inhibited o May help maintain consciousness muscle coordination and normal breathing Lesson 17 What are the components of the reflex arc What are the five steps in a neural reflex How are these reflexes classified Neural Reflexes o Rapid automatic responses to specific stimuli o Basic building blocks of neural function o One neural reflex produces one motor response o Reflex arc The wiring of a single reflex Beginning at receptor Ending at peripheral effector Generally opposes original stimulus negative feedback Five Steps in a Neural Reflex o Step 1 Arrival of stimulus activation of receptor Physical or chemical changes o Step 2 Activation of sensory neuron Graded depolarization leads to action potential generation o Step 3 Information processing by postsynaptic cell Triggered by neurotransmitters o Step 4 Activation of motor neuron Action potential generation in motor neurons o Step 5 Response of peripheral effector Triggered by neurotransmitters cause skeletal muscle contraction Four Classifications of Reflexes 1 By early development 2 By type of motor response 3 By complexity of neural circuit 4 By site of information processing Which spinal reflexes are the simplest Which are the most complex Monosynaptic reflex only 1 synapse in reflex arc o Simplest spinal reflex o Sensory neuron synapses directly onto motor neuron o A stretch reflex o Have the least delay between sensory input and motor output Ex Stretch reflex such as patellar reflex o Completed in 20 40 msec o Receptor is muscle spindle Polysynaptic reflexes more than 1 synapse in reflex
View Full Document
Unlocking...