Part 1: Nervous System and Spinal Nerves

Question 1

Central Nervous System composition and role:

Answer 1

• comprised of neuronal cell bodies, nerve fibers, and connective tissues of the brain and spinal cord.
• regulates and coordinates body functions

Question 2

Collections of neuronal cell bodies within the CNS are called:

Answer 2

nuclei

Question 3

The nerve fibers of the CNS are commonly arranged into discrete bundles called:

Answer 3

tracts

Question 4

Peripheral Nervous System (PNS) composition and role:

Answer 4

• Comprised of the neuronal cell bodies, nerve fibers and connective tissues that lie outside the CNS.
• Convey information between the CNS and peripheral structures.

Question 5

Collections of neuronal cell bodies outside the CNS (in the PNS) are called:

Answer 5

ganglia

Question 6

Somatic PNS composition and role:

Answer 6

• Comprised of peripheral nervous tissue responsible for carrying signals to and from skeletal muscles, tendons, joints and skin.
• Conveys general sensations of pain, temperature, touch and proprioception from the periphery to the CNS.

Question 7

The cell bodies of lower somatic motor neurons are located in:

Answer 7

the ventral horn of the spinal cord

Question 8

The cell bodies of somatic sensory neurons are located in:

Answer 8

dorsal root (spinal) and cranial nerve ganglia.

Question 9

Viscera refers to:

Answer 9

the internal organs of the body

Question 10

Autonomic PNS composition and role:

Answer 10

• Comprised of peripheral nervous tissue responsible for carrying signals to and from the viscera.
• Conveys viscera sensations such as distension.
• Sympathetic and parasympathetic components.

Question 11

The two components of the Autonomic PNS:

Answer 11

• sympathetic component; “fight or flight”
• parasympathetic component; “rest and digest”
• Both utilize two motor neurons in the peripheral path to innervate smooth and cardiac muscle.

Question 12

Role of parasympathetic component of autonomic PNS:

Answer 12

• controls digestive functions, slows the heart rate and constricts the pupils.

Question 13

Role of sympathetic component of autonomic PNS:

Answer 13

• controls pupillary dilation, increased heart rate, blood pressure and sweating.

Question 14

How do the sympathetic and parasympathetic components of the autonomic ANS innervate smooth and cardiac muscle?

Answer 14

two motor neurons in the peripheral path.

Question 15

Neuron structure:

Answer 15

cell body, dendrite(s) and an axon.

Question 16

Neurons can be classified as:

Answer 16

• multipolar, bipolar or unipolar based upon the number of processes associated with their cell body.
• motor (efferent) or sensory (afferent).

Question 17

Motor (efferent) Neurons:

Answer 17

• multipolar and carry information away from the CNS.
• cell bodies located in nuclei within the ventral horn of the spinal cord.

Question 18

Cell bodies of somatic motor neurons are located in:

Answer 18

• nuclei within the ventral horn of the spinal cord.

Question 19

Somatic motor neurons stimulate:

Answer 19

• contraction of skeletal muscle.
• nuclei are in ventral horn.

Question 20

Sensory (afferent) Neurons:

Answer 20

• unipolar and carry information towards the CNS.
• cell bodies clustered in ganglia located outside the CNS.

Question 21

Cell bodies of somatic sensory neurons are located in:

Answer 21

ganglia located outside the CNS

Question 22

Ganglia associated with spinal nerves are called:

Answer 22

dorsal root ganglia (spinal ganglia).

Question 23

The spinal cord lies within the vertebral canal extending from:

Answer 23

• the foramen magnum to the level of the intervertebral disc between L1/L2 vertebra.

Question 24

The spinal cord is surrounded by:

Answer 24

• bone
• epidural fat
• three meningeal layers:
  
  • dura mater (outermost),
  • arachnoid mater (intermediate)
  • pia mater (innermost)
• cerebrospinal fluid (CSF) that fills the subarachnoid space.

Question 25

White matter:

Answer 25

* bundles of myelinated axons arranged in discreet fiber tracts in the spinal cord * carry information up and down the spinal cord

Question 26

Gray matter:

Answer 26

* bundles of neuronal cell bodies or unmyelinated axons arranged into three major horns: ventral (motor), dorsal (sensory) and lateral (autonomic motor).

Question 27

Ventral horn:

Answer 27

* output side (efferent side) * contains the cell bodies of only motor neurons * multipolar

Question 28

Dorsal horn:

Answer 28

* input side (afferent) * contains only sensory neurons * unipolar

Question 29

How many vertebrae are there?

Answer 29

33

Question 30

How many pairs of spinal nerves are there?

Answer 30

* 31: * 8 cervical * 12 thoracic * 5 lumbar * 5 sacral * 1 coccyx

Question 31

Spinal nerves (31 pairs) attach to the spinal cord via:

Answer 31

* ventral (motor) and dorsal (sensory) roots

Question 32

Conus medullaris:

Answer 32

* the tapered end of the spinal cord beginning at L1/L2

Question 33

Spinal nerves exit the vertebral canal through:

Answer 33

* the intervertebral foramina. * C1-C7 exit above corresponding vertebral level. * C8 emerges below C7 vertebra. * Thoracic, lumbar and sacral nerves exit below vertebral level.

Question 34

Each spinal nerve is attached to the spinal cord via:

Answer 34

* a ventral (motor) root and a dorsal (sensory) root. * ventral root carries only motor nerve fibers * dorsal root carries only sensory nerve fibers

Question 35

Structure of a spinal nerve:

Answer 35

* a ventral (motor) root and a dorsal (sensory) root. * roots merge to form the mixed (motor and sensory fibers) spinal nerve. * spinal nerve divides into two forming a ventral ramus and a dorsal ramus which are also mixed nerves.

Question 36

Dorsal rami innervate:

Answer 36

* three things: * skin of the back * true back muscles * zygapophyseal joints

Question 37

Ventral rami innervate:

Answer 37

* all skin besides the back skin * skeletal muscles of the neck, trunk and limbs (no back muscles)

Question 38

The ventral root carries only:

Answer 38

* motor nerve fibers (multipolar) * origin is in ventral horn * merges with dorsal root in spinal nerve

Question 39

The dorsal root carries only:

Answer 39

* sensory nerve fibers (unipolar) * origin is in dorsal horn * merges with ventral root in spinal nerve * houses dorsal root ganglion

Question 40

Dorsal root ganglion:

Answer 40

* an enlargement on the dorsal root that houses the cell bodies of sensory neurons.

Question 41

The skin of the neck, body wall and limbs is divided up into segments or slices called:

Answer 41

* dermatomes (skin slice). * each dermatome is innervated by the ventral or dorsal rami of spinal nerves.

Question 42

Do dermatomal segments overlap one another?

Answer 42

* Yes. * Example: innervation to the T10 segment is supplied in part by the T9 and T11 ventral rami. Thus complete anesthesia of the T10 dermatomal segment would require “knocking out” the T9, T10, and T11 ventral rami.

Question 43

How many dermatomes are there?

Answer 43

* 31; one for each spinal nerve pair * 8 cervical * 12 thoracic * 5 lumbar * 5 sacral * 1 coccyx