A P Test 4 Study Guide Chapter 16 slides 33 66 1 Explain the function of the white columns of the spinal cord Posterior white columns lie between posterior gray horns and posterior median sulcus Anterior White columns life between anterior gray horns and anterior median fissure 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 2 Describe the connective tissue layers covering the spinal nerves Epineurium outer layer dense network of collagen fibers Perineurium middle layer divides nerve into fascicles axon bundles Endoneurium inner layer surrounds individual axons 3 Describe the locations and function of the major nerve plexuses Nerve Plexuses 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 Four major Plexuses of Ventral Rami Cervical Plexus Supplied head neck upper shoulder major nerve Phrenic nerve C3 5 which 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 4 Describe the five different patterns of neural circuits found in neuronal pools Neural Pools Functional groups of interconnected neurons interneurons Each with limited input sources and output destinations may stimulate or depress parts of brain or spinal cord Five Patterns of Neural Circuits in Neuronal Pools Divergence Spreads stimulation to many neurons or neuronal pools in CNS visual info goes to visual cortex and postural balance areas Convergence Brings input from many sources to single neuron subconscious and conscious control of breathing Serial Processing Moves information in single line relay of pain info Parallel Processing Moves same information along several paths simultaneously step onto nail you withdraw foot shift weight feel pain and scream Reverberation Positive feedback mechanism Functions until inhibited May help maintain consciousness muscle coordination and normal breathing Chapter 17 1 Explain what is a reflex and the components of the reflex arc Reflexes Automatic responses coordinated within spinal cored through interconnected sensory neurons motor neurons and interneurons Produces both simple and complex reflexes preserves homeostasis by making rapid adjustments in organs organ systems function Each time a particular reflex is activated produces the same motor response Reflex arc The writing of a single reflex Beginning at receptor Ending at peripheral effector Generally opposes original stimulus negative feedback 2 Describe the five steps in a neural reflex Neural Reflexes Rapid automatic responses to specific stimuli Basic building blocks of neural function One neural reflex produces one motor response Step 1 Arrival of stimulus activation of receptor Physical or chemical changes Step 2 Activation of sensory neuron Graded depolarization leads to action potential generation Step 3 Information processing by postsynaptic cell Triggered by neurotransmitters Step 4 Activation of motor neuron Action potential Generated in motor neurons Step 5 Response of peripheral effector Triggered by neurotransmitters cause skeletal muscle contraction 3 Describe how reflexes are categorized By Early development By Type of motor response By complexity of neural circuit By site of information processing 4 Explain the difference between monosynaptic and polysynaptic reflexes Monosynaptic reflex only 1 synapse in reflex arc Sensory neuron synapses directly ont motor neuron Polysynaptic reflex more then 1 synapse in reflex arc At least one interneuron between sensory neuron and motor neuron a What are some examples of these reflexes Monosynaptic Reflexes A Stretch reflex Have the least delay between sensory input and motor output why For example stretch reflex such as patellar reflex Completed in 20 40 msec Receptor is muscle spindle Polysynaptic Reflexes More complicated than monosynaptic reflexes ex Tendon reflex withdrawal reflexes Interneurons control more than one muscle group Produce either EPSP s or IPSP s at CNS motor nuclei EPSP s in motor neuron causes contraction of muscles while IPSP s in another motor neuron inhibits contraction of antagonistic muscles b What are the characteristics of polysynaptic reflexes Five General Characteristics of Polysynaptic Reflexes 1 Involve pools of interneurons may be excitatory flexor cross extensor reflex of inhibitory tendon reflex 2 Are intersegmental in distribution 3 Involve reciprocal inhibition 4 Have reverberating circuits Which prolong reflexive motor response 5 Several reflexes cooperate To produce coordinated controlled response 5 Explain the difference between intrafusal and extrafusal muscle fibers Intrafusal muscle fibers innervated by sensory and motor neurons Make up Muscle spindles in bundles Extrafusal muscle fibers large skeletal muscle fibers which surround muscle spindles 6 Explain the function of the muscle spindle Muscle Spindles The receptors in stretch reflexes Made up of bundles of small specialized intrafusal muscle fibers and surrounded by Extrafusal muscle fibers Maintain resting muscle tone and will contract when stimulated at greater levels 7 Explain the difference between alpha and gamma motor neurons Gamma Efferents Axons of the gamma motor neurons a Complete the reflex arc i Synapse back onto intrafusal fibers to contract them b Important in voluntary muscle contractions i Allow CNS to adjust sensitivity of muscle spindles ii Stretching of muscle spindle stimulates sensory neuron to generate action potentials which stimulate alpha motor neurons to contract extrasfusal fibers reducing muscle stretch 8 Describe the postural reflex tendon reflex and withdrawal reflex Tendon Reflex Sensory receptors distinct from muscle spindles or proprioceptors Prevents muscles from Developing too much tension Tearing or breaking tendons Greater the tension on tendon the greater the inhibitory effect on the muscle Withdrawal Reflexes Move body part away from stimulus pain or pressure For example Flexor reflex pulls hand away from hot stove Strength and extent of response and Depend on intensity and location of stimulus Postural Reflexes Maintain normal upright posture Many stretch reflexes are postural reflexes Stretched muscle responds by contracting automatically
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