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Chapter 13 The Spinal Cord, Spinal Nerves, and Somatic Reflexes
Spinal cord conducts signals up and down the body passing through gray and white matter, respectively.
Cervical and lumbar enlargements are wide points in the cord marking the emergence of motor nerves.
Each portion of the spinal cord served by a spinal nerve is called a segment of the cord.
Nerve fibers in a given tract in the white matter are similar in origin, destination, and function.
Motor signals typically begin in an upper motor neuron in the thalamus.
Most nerves are motor nerves.
A nerve fiber is enclosed in its own fibrous sleeve called perineurium
A ganglion is a swelling along a nerve containing cell bodies of peripheral neurons.
A dermatome is a nerve innervating a specific region in the skin.
Posterior root ganglia contain somas of unipolar neurons
Somatic reflexes are responses of skeletal, smooth and cardiac muscles.
The stretch reflex is a tendency of a muscle to stretch when it is overcontracted.
A stretch reflex is often accompanied by reciprocal inhibition.
The tendon reflex is the inhibition of a muscle contraction that occurs when its tendon is excessively stretched.
The cross extension reflex is the contraction of the extensors on one side of the body when the flexors are contracted on the other side
the precentral gyrus of the cerebrum.
The upper motor neurons that control skeletal muscles begin with a soma in
the corticospinal tract.
The signals that control your handwriting travel down the spinal cord in
the anterior horns.
Many upper motor neurons synapse with lower motor neurons in
Which of the following sensory functions involves neurons in the posterior root ganglia?
The spinal cord is divided into all of the following regions except
to protect neurons in both the ascending and descending tract.
The following are all functions associated with the spinal cord except
a fracture of vertebra L4
Which of the following fractures would be the least likely to cause a spinal cord injury
posterior root of a spinal nerve
This figure shows a detail of the spinal cord, meninges and spinal nerves. What does "1" represent?
This figure shows a detail of the spinal cord, meninges and spinal nerves. What does "4" represent?
dural sheath and vertebral bones
Epidural anesthesia is introduced in the epidural space between ___ to block pain signals during pregnancy.
This figure shows a cross section of the spinal cord. What does "3" represent?
arachnoid mater and pia mater.
Cerebrospinal fluid fills in the space between
Which of the following structures is the richest in lipid content?
neurosomas, dendrites, and proximal parts of axons of neurons.
Gray matter contains
___ carry motor commands from the brain along the spinal cord
Second-order neurons synapse with third-order neurons in the
___ keep(s) nerve fibers insulated from one another.
___ fibers innervate eyes and ears.
cluster of neurosomas in the PNS.
A ganglion is a
There are __ pairs of spinal nerves.
This figure shows the anatomy of a nerve. What does "3" represent?
This figure shows the posterior aspect of spinal nerve roots and plexuses. What does "3" represent?
the cervical enlargement
This figure shows the posterior aspect of spinal nerve roots and plexuses. What does "2" represent?
the thoracic region
The ventral rami of the spinal nerves form nerve plexuses in all regions except
The cervical plexus gives origin to the ___ nerve(s
Which of the following nerves originates in the coccygeal plexus?
This figure shows a dermatome map. A patient with no sensation in the left thumb would probably have a nerve damaged in
the gracile fasciculus
Which of these is an ascending tract of the spinal cord?
afferent and efferent fibers
A mixed nerve consists of both
posterior (dorsal) root
Which of the following branches of a spinal nerve have somas of solely sensory neurons?
The bundle of nerve roots that occupy the vertebral canal from L2 to S5 is called the
Somatosensory refers to these sensory signals except the sensory signals from
posterior root ganglion; gray matter
Neurosomas of the posterior root are located in the ___, whereas neurosomas of the anterior root are located in the ___.
A ___ is a cordlike organ composed of numerous ___.
somatic receptor afferent nerve fiber interneuron efferent nerve fiber skeletal muscle
Which one of the following best describes the order of a somatic reflex?
muscles of the hand
Which of the following groups of muscles have the most muscle spindles?
reflexes are spontaneous actions of the nervous system.
These are all properties of reflexes except
A muscle spindle contains mostly
flexor (withdrawal) reflex.
A nurse pricks your finger to type your blood. You flinch at the pain, pulling your hand back. This is called the
The quickest reflex arcs involve only two neurons, thus forming __ reflex arcs.
parallel after-discharge circuit
The flexor (withdrawal) reflex employs a ____, which maintains a sustained contraction.
an intersegmental reflex.
If a bee sting on the right thigh causes a quick involuntary reaction of the right arm, this would be an example of
gamma motor neurons.
The sensitivity of the muscle spindle is maintained by
alpha motor neurons.
The fibers that carry action potentials to cause skeletal muscle to contract are
stretch (myotatic) reflex.
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
contract and the antagonist muscles, the hamstrings, to relax.
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
A reflex where the sensory input and motor output are on opposite sides of the spinal cord is called a(n) _____ reflex arc.
prevents overcontraction of a muscle.
The tendon reflex
This reflex shows the least synaptic delay.
Tendon organs are