Chapter 13 The Spinal Cord, Spinal Nerves, and Somatic Reflexes

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The upper motor neurons that control skeletal muscles begin with a soma in
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the precentral gyrus of the cerebrum.
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The signals that control your handwriting travel down the spinal cord in
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the corticospinal tract.
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Many upper motor neurons synapse with lower motor neurons in
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the anterior horns.
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Which of the following sensory functions involves neurons in the posterior root ganglia?
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touch
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The spinal cord is divided into all of the following regions except
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pelvic.
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The following are all functions associated with the spinal cord except
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to protect neurons in both the ascending and descending tract.
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Which of the following fractures would be the least likely to cause a spinal cord injury
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a fracture of vertebra L4
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This figure shows a detail of the spinal cord, meninges and spinal nerves. What does “1” represent?
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posterior root of a spinal nerve
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This figure shows a detail of the spinal cord, meninges and spinal nerves. What does “4” represent?
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arachnoid mater
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Epidural anesthesia is introduced in the epidural space between ___ to block pain signals during pregnancy.
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dural sheath and vertebral bones
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This figure shows a cross section of the spinal cord. What does “3” represent?
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anterior horn
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Cerebrospinal fluid fills in the space between
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arachnoid mater and pia mater.
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Which of the following structures is the richest in lipid content?
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white matter
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Gray matter contains
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neurosomas, dendrites, and proximal parts of axons of neurons.
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___ carry motor commands from the brain along the spinal cord
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Descending tracts
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Second-order neurons synapse with third-order neurons in the
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thalamus.
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___ keep(s) nerve fibers insulated from one another.
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Endoneurium
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___ fibers innervate eyes and ears.
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Special
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A ganglion is a
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cluster of neurosomas in the PNS.
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There are __ pairs of spinal nerves.
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31
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This figure shows the anatomy of a nerve. What does “3” represent?
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perineurium
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This figure shows the posterior aspect of spinal nerve roots and plexuses. What does “3” represent?
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brachial plexus
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This figure shows the posterior aspect of spinal nerve roots and plexuses. What does “2” represent?
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the cervical enlargement
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The ventral rami of the spinal nerves form nerve plexuses in all regions except
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the thoracic region
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The cervical plexus gives origin to the ___ nerve(s
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phrenic
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Which of the following nerves originates in the coccygeal plexus?
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sciatic
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This figure shows a dermatome map. A patient with no sensation in the left thumb would probably have a nerve damaged in
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C6
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Which of these is an ascending tract of the spinal cord?
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the gracile fasciculus
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A mixed nerve consists of both
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afferent and efferent fibers
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Which of the following branches of a spinal nerve have somas of solely sensory neurons?
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posterior (dorsal) root
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The bundle of nerve roots that occupy the vertebral canal from L2 to S5 is called the
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cauda equina.
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Somatosensory refers to these sensory signals except the sensory signals from
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the viscera.
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Neurosomas of the posterior root are located in the ___, whereas neurosomas of the anterior root are located in the ___.
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posterior root ganglion; gray matter
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A ___ is a cordlike organ composed of numerous ___.
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nerve; axons
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Which one of the following best describes the order of a somatic reflex?
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somatic receptor afferent nerve fiber interneuron efferent nerve fiber skeletal muscle
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Which of the following groups of muscles have the most muscle spindles?
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muscles of the hand
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These are all properties of reflexes except
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reflexes are spontaneous actions of the nervous system.
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A muscle spindle contains mostly
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muscle fibers.
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A nurse pricks your finger to type your blood. You flinch at the pain, pulling your hand back. This is called the
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flexor (withdrawal) reflex.
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The quickest reflex arcs involve only two neurons, thus forming __ reflex arcs.
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monosynaptic
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The flexor (withdrawal) reflex employs a ____, which maintains a sustained contraction.
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parallel after-discharge circuit
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If a bee sting on the right thigh causes a quick involuntary reaction of the right arm, this would be an example of
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an intersegmental reflex.
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The sensitivity of the muscle spindle is maintained by
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gamma motor neurons.
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The fibers that carry action potentials to cause skeletal muscle to contract are
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alpha motor neurons.
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You go to the movies after a long day and you begin to nod off as soon as the movie starts. Your head starts to lower a little but this reflex causes your head to rise. This is called the
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stretch (myotatic) reflex.
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In the patellar tendon reflex arc, the patellar ligament is stretched, which stretches the quadriceps femoris muscle of the thigh. This reflex will cause the quadriceps femoris to
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contract and the antagonist muscles, the hamstrings, to relax.
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A reflex where the sensory input and motor output are on opposite sides of the spinal cord is called a(n) _____ reflex arc.
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contralateral
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The tendon reflex
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prevents overcontraction of a muscle.
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This reflex shows the least synaptic delay.
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tendon reflex
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Tendon organs are
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proprioceptors.
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Light touch, tickle, itch, temperature, pain, and pressure are stimuli collected by which spinal tract? A) gracile fasciculus B) lateral corticospinal C) ventral spinocerebellar D) spinothalamic
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D) spinothalamic
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Balance and posture, regulation of awareness of pain are all signals of which motor spinal tract? A) ventral spinocerebellar B) dorsal spinocerebellar C) ventral corticospinal D) lateral reticulospinal
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D) lateral reticulospinal
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This segment of the spinal cord has 8 spinal nerves. A) cervical B) thoracic C) lumbar D) sacral
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A) cervical
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Muscle spindles are a type of proprioceptors that respond to stretching of the A) tendon. B) ligament. C) muscle fibers. D) nerve.
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C) muscle fibers.
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An example of a polysynaptic reflex arc is a _______ reflex. A) reciprocal B) flexor C) stretch reflex D) myotatic
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B) flexor
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This spinal cord tract carries information about position and movement of the lower extremities to the brain. A) tectospinal B) cuneate fasciculus C) spinothalamic D) gracile fasciculus E) ventral corticospinal
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D) gracile fasciculus
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This area of the meninges has many smaller blood vessels and closely adheres to the outer surface of the central nervous system. A) dura mater B) subdural space C) arachnoid membrane D) subarachnoid space E) pia mater
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E) pia mater
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Sensory neurons enter the spinal nerve cord at the A) anterior root. B) ventral root. C) gray commissure. D) lateral horns. E) anterior median fissure.
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B) ventral root.
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Which branch of each spinal nerve gives rise to the nerves of the extremities? A) posterior ramus B) posterior root C) anterior ramus D) anterior root
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C) anterior ramus
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The brachial plexus innervates A) arms and shoulders. B) only the arm, but the whole arm. C) the upper arm only. D) the lower arm only.
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A) arms and shoulders.
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When the patellar reflex is elicited, the quadriceps muscles contract, but the hamstrings, their antagonists, relax. This relaxation is called A) reciprocal inhibition. B) polysynaptic. C) crossed extension. D) flexor withdrawal. E) extrafusal inhibition.
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A) reciprocal inhibition.

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