BSC2085 Exam 4 Study Guide Lesson 16 The Spinal Cord and Nerves Organization of White Matter sulcus Posterior White Columns Lie between posterior gray horns and posterior median 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 Lateral White Columns Located on each side of spinal cord between anterior cord to the other posterior columns Tracts Fasciculi Bundles of axons in the white columns o Relay same information in same direction o Ascending Tracts Carry information to brain o Descending Tracts Carry motor commands to spinal cord 1 BSC2085 Exam 4 Study Guide Spinal Cord Summary Spinal cord has a narrow central canal surrounded by gray matter o Contains sensory motor nuclei Sensory nuclei are dorsal Motor nuclei are ventral Gray matter covered by a thick layer of white matter White Matter o Consists of ascending AND descending axons o Organized in columns o Contains axon bundles with specific functions Spinal cord highly organized o Possible to predict results of injuries to specific areas Anatomy of Spinal Nerves Every spinal cord segment is connected to a pair of spinal nerves Every spinal nerve is surrounded by three 3 connective tissue layers that support structures contain blood vessels Three 3 Connective Tissue Layers of Spinal Nerves 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 2 BSC2085 Exam 4 Study Guide Peripheral Distribution of Spinal Nerves Motor Nerves o Dorsal Ramus Contains somatic visceral motor fibers Innervates the back o Ventral Ramus Larger branch Innervates ventrolateral structures and limbs 3 BSC2085 Exam 4 Study Guide Sensory Nerves impulses o Dorsal ventral rami also carry sensory information in addition to motor Dermatomes Bilateral region of skin monitored by specific pair of spinal nerves 4 BSC2085 Exam 4 Study Guide Peripheral Neuropathy Regional loss of sensory or motor function o Caused by trauma or compression o Shingles Painful rash caused by chicken pox herpes virus that travels to the dermatome served by the affected sensory nerve Virus remains dormant after chicken pox infection in neurons of Nerve Plexuses anterior gray horns Nerve Plexus Complex interwoven network of nerve fibers Formed from blended fibers of ventral rami of adjacent spinal nerves Control skeletal muscles of the neck limbs Four 4 Major Plexuses of Ventral Rami o 1 Cervical Plexus Supplies head neck upper shoulder Major nerve phrenic nerve C3 5 controls diaphragm o 2 Brachial Plexus Supplies pectoral girdle upper limbs o 3 Lumbar Plexus Supplies anterolateral abdominal wall genitals lower limbs o 4 Sacral Plexus Supplies buttocks perineum lower limbs 5 BSC2085 Exam 4 Study Guide Functional Organization of Neurons Sensory Neurons deliver information to CNS Motor Neurons deliver commands to peripheral effectors o 10 million o million Interneurons interpret plan and coordinate signals in out o 20 billion most common type Neuronal Pools Neuronal Pools Functional groups of interconnected neurons interneurons o Each with limited input sources output destinations o May stimulate or depress parts of brain or spinal cord Five 5 Patterns of Neural Circuits in Neuronal Pools o 1 Divergence 6 BSC2085 Exam 4 Study Guide Spreads stimulation to many neurons or neuronal pools in CNS Visual info goes to visual cortex postural balance areas o 2 Convergence Brings input from many sources to single neuron Subconscious conscious control of breathing o 3 Serial Processing Moves information in a single line Relay of pain info o 4 Parallel Processing o 5 Reverberation Positive feedback mechanism Functions until inhibited Moves same information along several paths simultaneously Ex Step onto nail withdraw foot shift weight feel pain scream May help maintain consciousness muscle coordination normal breathing Lesson 17 Spinal Reflexes Automatic responses coordinated within spinal cord through o Interconnected sensory neurons o Motor neurons o Interneurons Produce simple AND complex reflexes Preserves homeostasis makes rapid adjustments in organs organ system function Neural Reflexes Rapid automatic responses to specific stimuli o Building blocks of neural function o One neural reflex produces one motor response Reflex Arc The wiring of a single reflex Reflexes 7 BSC2085 Exam 4 Study Guide o Begins at receptor o Ends at peripheral effector o Opposes original stimulus negative feedback Five 5 Steps in a Neural Reflex o 1 Arrival of stimulus activation of receptor Physical or chemical changes o 2 Activation of sensory neuron Graded depolarization leads to action potential generation o 3 Information processing by postsynaptic cell Triggered by neurotransmitters o 4 Activation of motor neuron Action potential generated in motor neurons o 5 Response of peripheral effector Triggered by neurotransmitters cause skeletal muscle contraction Four 4 Classifications of Reflexes o 1 Time of development o 2 Type of motor response o 3 Complexity of neural circuit o 4 Site of information processing 1 Development of Reflexes o Innate Reflexes Formed before birth Basic neural reflexes Ex Withdrawal from pain chewing suckling tracking objects with eyes o Acquired Reflexes Learned motor patterns Rapid automatic Ex Riding a bike pressing on brakes when someone cuts you off in traffic 2 Motor Response o Nature of resulting motor response o Somatic Reflexes Involuntary control of muscular system Superficial Reflexes Skin mucous membranes Ex Plantar Reflex Toes curl in adults fan out in infants Stretch or Deep Tendon Reflexes 8 BSC2085 Exam 4 Study Guide Ex Patellar or Knee Jerk Reflex o Visceral Reflexes Autonomic reflexes control systems other than muscular system 3 Complexity of Neural Circuit Ex Consensual Light Reflex Shine light on one eye and both eyes flinch o Monosynaptic Reflex Only 1 synapse in reflex arc Sensory neuron synapses directly onto motor neuron o Polysynaptic Reflex More than 1 synapse in reflex arc At least one interneuron between sensory neuron motor neuron 4 Site of Information Processing o Spinal Reflexes Occur in spinal cord o Cranial Reflexes Occur in brain Spinal Reflexes Range in increasing order of complexity Simplest most complex o Monosynaptic reflexes o Polysynaptic reflexes o Intersegmental Reflex Arcs Many segments interact produce a highly variable
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