BY 30 – Fall 2001
17.1. Protective
Structures
a. The spinal cord is protected by a series of bones called _________________, which form a structure called the _______________________________. The spinal cord lies in a space called the _________________________ and spinal nerves exit to either side through spaces called ________________________.
b. The three connective tissue layers that surround and protect the brain and spinal cord are collectively called the ____________________, which consist of the ___________________________, __________________________, and _________________________________. Cerebrospinal fluid is located in the __________________ space located between the ____________________ and _______________________.
c. The tough outer layer of the meninges is called the _____________________, which consists of _______________________ connective tissue. Just outside this structure is the _________________________ space which contains loose connective tissue, adipose tissue and blood vessels.
d. The middle layer of the meninges is called the _________________________, which is separate from the dura mater by the __________________________ space and the pia mater by the ____________________________ space. This layer gets its name by the spider-like extensions that lie within the ______________________________________ space.
e. The innermost layer of the meninges is called the ______________________, which is tightly adherent to the surface of the spinal cord. In some regions it gives rise to ___________________ ligaments which anchor the spinal cord to the _______________________.
17.2. Gross
Anatomy of the Spinal Cord
a. The spinal cord begins at the ___________________________ and ends at the _______________________________________ which lies at vertebral level ___________________________. Along the way there are two enlargements called the ________________ and ____________________ enlargements.
b. Extending from the inferior portion of the spinal cord is the ______________, which represents a continuation of the pia mater.
c. Arising from the spinal cord are a series of ________________________ and ____________________ roots that combine to form ____________________, of which there are ________________ pairs. The portion of the spinal cord that gives rise to the roots that form a single pair of spinal nerves is called a spinal _____________________, which are named on the basis of the spinal nerves that arise from it.
d. Of the 31 pairs of spinal nerves, there are ________________ pairs of cervical nerves; ______________ pairs of thoracic nerves; _______________ pairs of lumbar nerves; __________________ pairs of sacral nerves; and a single pair of _____________________ nerves.
e. Because in development the spinal cord stops growing before the vertebral column, the spinal cord only extends to vertebral segments _____________. Yet because the spinal nerves still exit intervertebral foramina at vertebral levels corresponding to the spinal segments, ventral and dorsal roots must descend below the termination of the spinal cord, collectively forming the __________________________.
f. A lumbar puncture procedure is designed to obtain a sample of __________________ from the _______________________ space. Because of where the spinal cord terminates, this procedure is usually done between vertebral segments ______________________ to minimize the danger of the needle hitting the spinal cord.
17.3. Histology of
the Spinal Cord and Spinal Nerves
a. The spinal cord can be subdivided into _______________________ and _____________________. The _________________________ is located centrally and consists of neuron ________________________________, _______________________, and _____________________________. In addition ____________________________ cells are also present.
b. The gray matter is shaped somewhat like a butterfly. The “wings” are the ______________________ and ______________________________ horns, while the connecting portion is called the ___________________________, which has the ___________________________ in the middle. In general the dorsal gray matter has ______________________ functions while the ventral gray matter has _________________________ functions.
c. Within the ventral horn, the large neurons are called ____________________, which supply the extrafusal fibers of skeletal muscle while the smaller ________________________ neurons supply the intrafusal fibers.
d. In spinal segments T1-L2 preganglionic sympathetic motor neurons form the _______________________ horn, located somewhat between the ventral and dorsal horns. In spinal segments ________________________, a comparable region is created due to the presence of preganglionic parasympathetic motor neurons.
e. Within the dorsal horn of the spinal cord are found _____________________, which act as integration neurons associated with _______________________ function.
f. The white matter consist of _______________________________, (mostly _____________________) along with ______________________ cells. On the outside of the white matter are two grooves called the _____________________ fissure and the ______________________ sulcus. The white matter is subdivided into ______________________________, ________________________, and ___________________________ portions. Within each are groups of axons called ____________________________.
g. Sensory information that arises from receptors in the body and travels up the spinal cord to end in the __________________ form ___________________ tracts. In the case of sensory information that we have conscious awareness of, it all passes through a portion of the brain called the ________________ on its way to the cerebrum. Most of this sensory information follows one of two tracts called the _________________________ and the ________________________ tracts. The dorsal columns lie in the _____________________ white mater; while the lateral spinothalamic tract lies in the ___________________ white, and the ventral spinothalamic tract lies in the _____________________ white.
h. Motor information that originates in the brain and descends into the spinal cord forms _________________________ tracts. Of the many examples, the motor information that originates within the cerebrum forms the lateral and ventral ________________________ tracts, which lie in the _____________ and ___________________ white mater, respectively.
i. A spinal nerve forms by the union of a ____________________________ and ____________________________ root. The ventral root consists of axons of _____________________ neurons while the _______________________ root contains axons of sensory neurons. Along the course of the dorsal root is the _____________, which contains the cell bodies of ______________________ neurons.
j. A spinal nerve lies within an __________________________ and splits into a ___________________ and _______________________ ramus. The ventral rami of spinal nerves T2-T12 form ________________________ nerves. The ventral rami of other spinal nerves supply various ______________________, like the ____________________________, ___________________________, and __________________________ plexuses.
k. The outside of a nerve is covered by a layer of dense irregular FECT called the _____________________. Extensions of this layer pass inward as the ______________________________ to enclose groups of axons called a ________________________. The connective tissue that surrounds individual axons is called the _____________________________.
17.4. Spinal
Reflexes
a. Spinal reflexes can be subdivided into ________________________ reflexes, which involve skeletal muscle; and visceral reflexes which involve __________________________, _________________________________, or ________________________________ as effectors.
b. A typical spinal reflex involves a ____________________________ limb, an ______________________ center, and a ________________________ limb.
c. The sensory limb involves a ____________________________ neuron whose cell body lies within a _________________________. This cell, described as ____________________________ in shape has one portion of the axon in the periphery whereas the other portion projects into the ____________________. In some cases, there are specialized sensory ___________________ involved. In any event, some change gives rise to a graded potential, sometimes called a ___________________________ which if sufficient in intensity will bring the primary afferent neuron to ________________________, creating an action potential.
d. In most spinal reflexes, the integration center consist of one or more _____________________ located in the ___________________ of the spinal cord. These cells receive synapses from ______________________ neurons, most of which are excitatory. In turn these interneurons send their axons to ____________________________ neurons.
e. The motor limb of a spinal reflex involves _____________________ neurons for somatic reflexes and ___________________ autonomic motor neurons for visceral reflexes.
f. The ____________________ reflex involves contraction of a skeletal muscle when it has been stretched. This reflex is referred to as _________________ because it involves only one synapse, and is most usually tested at the ____________________ joint.
g. The sensory limb of the stretch reflex involves special stretch receptors called __________________ located in muscle fibers called ___________________ fibers. When a muscle is stretched, by say tapping on the patellar tendon, these muscle spindles become ___________________, increasing the number of _______________________. These action potentials travel along the axon of the primary afferent neuron to end on _____________________ neurons.
h. The motor limb of the stretch reflex involves the _______________________ neurons that supply ___________________________ fibers, constituting a ______________________ unit. As a result of this reflex, these muscle fibers _____________________________.
i. The principle of ______________________ innervation involves relaxation of antagonistic muscle groups. In the stretch reflex, the primary afferent neuron also ends on an _________________________________ which in turn forms ______________________ synapses on a motor neurons supplying antagonistic muscles to the muscle which was stretched.
j. The ______________________ reflex involves muscle actions that take place in response to some painful stimulus. As a result of some painful stimulus, the primary afferent neurons project into the spinal cord to end on several different ____________________ located in the ___________________ horn.
k. During the withdrawal reflex, flexors on the side of the stimulus (called the _____________________ side) will _________________________ while the extensors will __________________________ due to reciprocal innervation.
l. During the withdrawal reflex, flexors on the side opposite to the stimulus (called the ____________________ side) will ________________________ and the extensors will ______________________, due to the ________________________________________ reflex.