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41 Cards in this Set

  • Front
  • Back
What is included in the CNS and the PNS
Central Nervous System : brain, spinal chord

Peripheral Nervous System :
nerves, ganglia
What is the function of nerves? Distinguish between cranial and spinal nerves.
Nerves function as communication links between the body and CNS. Nerves that connect to the brain are called cranial nerves, and nerves that connect to the spinal cord are called spinal nerves (there is one exception to this generalization; the eleventh cranial nerve actually arises from the spinal cord).
How many cranial and spinal nerves are there?
How are the spinal nerves divided?
12 pairs of cranial nerves and 31 pairs of spinal nerves
Spinal nerves are named by region corresponding to the regions of the vertebral column: there are 8 cervical nerves, 12 thoracic, 5 lumbar, 5 sacral, and 1 coccygeal.
Describe neurulation
Its the development of the spinal cord. Neuroepithelial cells of neural tube proliferate to form two additional
layers; the original cell
layer becomes known as
the ventricular layer, around that is the mantle layer and around both of those is the marginal layer.
What do cells in the mantle layer form during neurulation?
the cells in the mantle layer
cluster together forming four
regions/columns: 2 basal plates ventrally and
2 alar plates dorsally
These plates eventually become the ventral and dorsal horns of grey matter.
What do the plates and the layers formed in neurulation become eventually ?
The basal and ajar plates eventually become the ventral and dorsal horns of gray matter.
. The marginal layer undergoes myelination and becomes the white matter. The ventricular layer remains as the lining of the central canal (ependymal layer).
What is in gray matter and white matter usually?
Gray: neuron cell bodies
White: axons (fiber tracts)
What are the general features of the vertebral column?
Spinal cord is in the vertebral canal, which is a channel through the column. The column is made up of 33 vertebrae, which are subdivided in 5 regions: cervical, thoracic, lumbar, sacral, and coccygeal
What are some characteristics of the vertebrae?
How many are there of each type of vertebrae?
The vertebrae in the sacral and
coccygeal regions are fused, forming the sacrum
and coccyx, respectively. Vertebrae in the cervical,
thoracic and lumbar regions are separated by
intervertebral discs. On the lateral aspect of the
column there are intervertebral foramina (holes)
that permit passage of vessels and nerves into or
out of the vertebral canal.
There are 7 cervical, 12 thoracic, 5 lumbar, 5 sacral, and 4 coccygeal.
What are the intervertebral foramina?
On the lateral aspect of the
column there are intervertebral foramina (holes)
that permit passage of vessels and nerves into or
out of the vertebral canal.
Where does the spinal cord originate and terminate? What is the terminal part called?
In adults it extends from the foramen magnum (where it is joined to the brainstem) to the upper lumbar region (L1- L2) of the vertebral column (in infants it may extend as far as L3). The terminal part of the spinal cord is called the conus medullaris.
Why does the spinal cord have two enlargements and where are they?
Enlarged b/c large number of neuron cell bodies are present to provide innervation to the limbs.
cervical enlargement – found in the C5-T1
lumbar enlargement – found in the L1-S3 regions
What are the meninges?
Three protective layers around the spinal cord. The dura mater is the thick outermost layer, the
arachnoid mater is the middle layer that resembles
a spider web, and the pia mater is the innermost
layer that is intimately applied to the spinal cord.
What is the epidural space?

What is the subdural space?
The epidural (extradural) space is the area
between the dura mater and the vertebral canal.
It is filled with fat and contains the internal
vertebral venous plexus.
The subdural space between the dura and arachnoid mater is a potential space (i.e. it does not normally contain anything, but could expand if something such as blood leaked into it).
Where does the epidural space begin/end and what is it used for by anesthesiologists?
It begins at the foramen
magnum and ends inferiorly at the sacral hiatus.
Local anesthesia is often injected into the
epidural space (epidural block) to anesthetize the
nerve roots (e.g. for childbirth).
What is the dural sac?
Deep to the epidural space, the dura forms a sac around the spinal cord. The dural sac begins at the foramen magnum where it is continuous with the dura mater around the brain. It extends approximately to the S2 vertebral level (varies between S1-S3), where it becomes the external filum terminale (coccygeal ligament) that is anchored to the coccyx.
What is the subarachnoid space?
The subarachnoid space located between the arachnoid mater and pia mater contains cerebrospinal fluid (CSF). It extends inferiorly as far as the dural sac (S2); therefore, fluid may be sampled from the subarachnoid space without fear of puncturing the spinal cord. The subarachnoid space of the spinal cord is continuous with the subarachnoid space of the brain.
What is the internal and external filum terminale?
The pia mater cannot be separated from the spinal cord. At the conus medullaris, a thin strand of pia mater continues inferiorly as the internal filum terminale, which joins the external filum at the inferior limit of the dural sac. The dural sac becomes the external filum terminale.
What are the denticulate ligaments?
The pia also sends lateral extensions called denticulate ligaments that fuse to the dura and help anchor the spinal cord within the vertebral canal.
What are somites?
Segments of the mesoderm, some parts of the body develop in a segmental fashion, each somite is associated with a portion of the spinal cord, and each portion has one PAIR of spinal nerves attached to it.
How are spinal nerves connected to the spinal cord?
Via rootlets, known collectively as the dorsal root (sensory neurons only) and has associated dorsal root ganglion with sensory cell bodies inside, and ventral root (motor neurons only).
What does the spinal nerve divide into?
It divides into two branches. One branch is the
dorsal primary ramus (DPR) that goes to the back region. The other branch is the ventral primary ramus (VPR) that travels
around the body wall and is distributed primarily to the neck, trunk and limbs. (ramii have mixed neuron types inside).
Which spinal nerve are considered typical and atypical?
Which rami form nerve plexuses?
Only the T2-T12 spinal nerves have the typical spinal nerve pattern shown in the diagram on the previous page; therefore, these are considered to be “typical” spinal nerves. Spinal nerves in the cervical, lumbar and sacral regions (as well as T1) are “atypical” because their VPR do not just travel around the body wall – they form nerve plexuses and travel out into the extremities (limbs).
What is a nerve plexus? Which rami form nerve plexuses?
A nerve plexus is a network or mixing of nerves. Only ventral primary rami form nerve plexuses.
Where do cervical spinal nerves exit the vertebral column? Where do the remaining nerves exit and why?
The cervical spinal nerves
exit the vertebral column superior to their same
numbered vertebra. However, since there is an eighth cervical nerve but no C8 vertebra, the C8 nerve passes
superior to the T1 vertebra and the T1 nerve must
pass inferior to the T1 vertebra. Consequently,
all the remaining spinal nerves pass inferior to
their corresponding vertebra.
What happens to the distance between a spinal cord segement and its corresponding vertebra as you move inferiorly down the cord?
The distance between them increases. This is particularly
obvious for the lumbar and sacral
spinal nerves, whose nerve roots
are seen in the inferior part of the
vertebral canal traveling towards
their corresponding intervertebral foramina.
This collection of nerve roots is called
the cauda equina, due to its resemblance
to a “horse’s tail”.
What is the functional unit of the nervous system?
What are the basic parts of this unit?
The neurons, cells that carry nerve impulses.
Typical neurons have three
basic parts: a cell body that contains
organelles, a receptive process (dendrite)
that carries the impulse towards the cell
body, and a conductive process (axon) that
carries the impulse away from the cell body.
The term “nerve fiber” is often used
interchangeably with “neuron”, however by
strict definition “nerve fiber” refers to the axon.
What is a nerve? Ganglion?

What is a nucleus?
What is a tract?
Hollow tube of connective tissue with neuron axons/dendrites travelling inside.
Ganglion is a collection of cell bodies in the PNS enclosed by connective tissue.
A nucleus is a collection of cell bodies in the CNS.
Collection of neuron processes (axons) in the CNS.
What are the different neuron structure types?
unipolar – have 1 process; common in invertebrates (not found in humans after birth).

pseudounipolar – have 1 process that splits into 2; abundant in the PNS.

bipolar – have 2 processes; only found in a few special locations such as the retina.

multipolar – have more than 2 processes; abundant in the PNS and CNS, most neurons like this.
How are nerves classified according to function?
1. direction their impulse is travelling, 2. type of structure they are innervating.
What are the neuron classifications for the direction an impulse is travelling?
afferent neurons – conduct impulses towards the CNS. They are pseudounipolar.

efferent neurons – conduct impulses away from the CNS. They are multipolar.
What are the neuron classifications for the structures a neuron innervates?
somatic structures – these are the parts of the body that are derived from
somites; they include skeletal muscle,
skin, bones and joints. Somatic structures
generally are involved with moving and supporting the body as a whole – they
form the “framework” of the body.

visceral structures – these are the parts of the body that are concerned with
involuntary activities; they include organs, glands and blood vessels (specifically, visceral neurons innervate the smooth and cardiac
muscle that forms and/or lines organs and blood vessels). Visceral structures carry out the “internal functions” of the body such as digestion, respiration, and excretion.
What are the four functional types of neurons?

somatic afferent, somatic efferent, visceral afferent, visceral efferent.
*are found everywhere in the body so the prefix “general” is added to their name
What types of neurons can a nerve contain?
What are the functional components of a nerve?
A nerve can contain any combination of the functional types of neurons. Some nerves contain only sensory neurons (GSA and GVA), while others contain only motor neurons (GSE and GVE); these are called sensory nerves and motor nerves, respectively. Nerves that contain both sensory and motor neurons are called mixed nerves. The types of neurons a nerve contains are its functional components.
Give a description of GSA and GSE
Afferent impulses from skin, skeletal muscles, bones, ligaments and tendons (touch, pain, temperature, proprioception)
Motor impulses to skeletal muscle
Give a description of GVA and GVE
Afferent impulses from organs, glands, mucous membranes and blood vessels (pain, stretch, contraction). These fibers are often part of visceral reflexes.
Motor impulses to smooth and cardiac muscle, and secretory impulses to glands
What type of structure do afferent neurons have? efferent?
what is unique about GVE?
GVE is unique because it consists of a two-neuron chain.
What is a nerve map? Why are they used?
A nerve map is basically a crude drawing of the innervation of a particular structure. They are useful for determining the route of a particular neuron. Diagnosing nerve lesions and sectioning groups of nerves to relieve pain are just two clinical examples.
What is a dermatome?
In an adult, the term dermatome refers to that area of skin (that is innervated by the spinal nerve pair).
What are cutaneous nerves and what do they contrain?
cutaneous nerves are nerves that innervate the skin. As discussed above, cutaneous nerves contain sensory fibers (GSA) that innervate the skin itself (i.e. detect pressure,
temperature, etc.). Cutaneous nerves also
contain motor fibers (GVE) that innervate
structures found within the dermis of the skin (i.e. sweat glands, arrector pili muscles, blood vessels, etc.).