• The anatomic structure of the spinal cord.
• The cross sectional anatomy of the spinal cord.
• The components of the reflex arc.
• Several important reflexes
• The naming and distribution of the spinal nerves.
Materials Required: VanPutte/Seeley text Chapter 12 • Media Phys module 6 • A & P Revealed
A. External anatomy
1. Anterior median fissure and posterior median sulcus
2. Spinal cord extends to the level of the second lumbar vertbra
3. Cauda equina contains the dorsal and ventrals of nerves L2 –S5
4. 31 segments to the spinal cord: Each segment produces 1 pair of spinal nerves
B. Cervical enlargement
1. in the inferior cervical region corresponds to th elocation where nerve fibers that supply upper limbs enter and leave spinal cord
C. Lumbosacral enlargement
1. inferior thoracic, lumbar and superior sacral regions supplying lower limbs enter and leave spinal cord
D. Conus medullaris
1. conelike region inferior to lumbosacral enlargement, its tip is the inferior end of the spinal cord ends ad level of 2nd lumbar vertebra
E. Filium terminale
Where does the spinal cord originate? Foramen Magnum
Where does the spinal cord end? Level of Second Lumbar Vertebra
What is the lowest vertebral foramen which contains the spinal cord? Level of Second Lumbar Vertebra
What is found in the vertebral canal of the vertebrae distal to the end of the spinal cord? “Horses tail” Cauda Equina
How many segments of the spinal cord are there? 31
What does each segment of the spinal cord produce? 1 pair of spinal nerves
What is found in the dorsal root? 6-8 rootlets
What is found in the ventral root? 6-8 rootlets
A. Epidural space: a true space between the walls of the vertebral canal and the dura matter of the spinal cord
B. Dura mater (thecal sac) - the most superficial and thickest mambrane (Forms Thecal Sac)->attached to rim of foramen magnum
C. Subdural space : Between the Arachnoid and the Dura matter (contains a very small amount of serous fluid)
D. Arachnoid membrane :Middle meningeal membrane, very thin and wispy (Arachnoid means cob webs)
E. Subarachnoid space : Between pia and arachnoid matter (web-like strands) containing blood vessels and cerebrospinal fluid
F. Pia mater : Third, deepest meningeal layer bound tightly to the surface of the spinal cord and brain
G. Denticulate Ligaments : connective tissue septa extending from lateral sides of spinal cord to dura matter
H. Filum Terminale : connective tissue strand that anchors the conus medullaris and thecal sac to first coccygeal vertebra
Where is cerebrospinal fluid found? within the subarachnoid space
How do meninges & other connective structures stabilize spinal cord. Tendon-like structures attach to vertebra & other menegeal structures.
Cranially
Caudally
Laterally
: Dura mater fuses with the periostium of the occipital bone
: Filium terminal anchors conus medullaris and dura mater to the first coccygeal vertebra
: Denticulate ligaments –extend from the spinal cord to the dura mater.

A. White matter
1. What is a column (funiculus)?
Bundle of myelinated fibers that run the length of the core
2. How many columns are there on each side of the spinal cord? - 3 per side: anterior, posterior, and lateral
3. What is a tract (fasciculus)?
Subdivision of columns
4. What is contained within a tract?
All axons in the tract relay the same type of information in the same direction
5. What is the difference between an ascending and descending tract?
Tracts are either ascending or descending
B. Gray matter
1. Describe the location of and state what is found within each of the three horns of gray matter of the spinal cord :
-
-
Anterior
Lateral
-cell bodies of somatic motor neurons
-Cell bodies of visceral motor neurons (Only in thoracic and lumbar segments)
Posterior - somatic and visceral sensory neurons
2. What is the function of the gray commissure?
connect right and left sides
3. What is contained within the central canal?
contains cerebrospinal fluid
4. How do the spinal nerves arise from the spinal cord?
from numerous rootlets along the dorsal and ventral surfaces of the spinal cord
Refer to A & P Revealed, Nervous System, Animations, Physiology, Reflex Arc • Refer to MediaPhys, Modules 6.36 and 6.37
A. What is a reflex? Refer to Process Figure 12.5
: An automatic response to a stimulus produced by a reflex ark
1. Processing sites : Cranial or spinal
2. Nature : Somatic or visceral
3. Complexity : Monosynaptic or polysynaptic
4. Distribution : Ipsilateral or contralateral
B. 5 components & Functions of the reflex arc
1. A sensory receptor
2. A sensory Neuron
3. An Interneuron
4. A Motor Neuron
5. An Effector Organ
C. Types of reflexes
1. Stretch
2. Golgi Tendon
3. Withdrawal
4. Crossed Extensor
D. What is the difference between a somatic and a visceral reflex?
1. somatic
2. visceral
E. Define the following terms as they relate to reflexes
1. monosynaptic : involve simple neronal pathways in which sensory neurons synaps directly with motor neurons
2. polysynaptic : more complex pathways & intergative centers with one or more internurons between sensory & motor neurons
3. ipsilateral : the same side
4. contralateral : the opposite side
F. Examples: Explain the structure and function of each of the following reflexes:
1. Stretch –
Refer to Process Figure 12.6
- Monosynaptic and ipsilateral
- Reciprocal innervation - Agonist is stimulated • Antagonist is inhibited
- Also synapses with a neuron that relays information to the brain
- Brain not necessary for the reflex • Brain makes us aware that the reflex has occurred
2. Tendon (Golgi) –
Refer to Process Figure 12.7
- Polysynaptic and ipsilateral
- Causes inhibition of the motor neuron leading to muscle relaxation
- Prevents damage due to tension
3. Flexor reflex (withdrawal)
Refer to Process Figures 12.8 & 12.9
- Polysynaptic, ipsilateral, and intersegmental
- Withdrawal of a limb due to contraction of the flexor muscles
- Reciprocal innervation causes the extensors to relax
- Example –hand touches a hot stove
4. Crossed extensor
Refer to Process Figure 12.10
- Polysyaptic, contralateral, and intersegmental
- Motor response on the opposite side of the stimulus
- Complements the flexor reflex and occurs simultaneously
- Example : Step on a sharp object:
–withdraw the foot (flexor) Shift your weight to the opposite side to keep your balance (crossed extensor)
G.Clinical significance What is the clinical significance of a reflex?
1. Exaggerated or absent or abnormal reflexes indicate damage along a particular pathway

H. List several clinically significant reflexes.
1. Patellar (knee jerk)
2. Achilles reflex (ankle jerk)
3. Babinski
4. Abdominal
Refer to A & P Revealed, Nervous System, Animations, Anatomy, Typical Spinal Nerve.
A. Describe the connective tissue associated with the spinal nerves and state the specific
structure which is encased by each of the following divisions of connective tissue
1. Epineurium : Connective tissue surrounding the axon, nerve fiver and its Schwan cell sheath
2. Perineurium : Heavier connective tissue layer surrounding a group of axons creating nerve fascicles
3. Endoneurium : Third layer of dense connective tissue binding nerve fescicles together to form a nerve
B spinal nerves are classified as being motor, sensory, or mixed (both motor and sensory)?
C. Give the names and numbers or the 31 pairs of spinal nerves which originate from the spinal cord.
1.
8 pairs cervical (C1-C8)
2.
12 pairs thoracic (T1-T12)
3.
5 pairs lumbar (L1-L5)
4.
5 pairs sacral (S1-S5)
5.
1 pair coccyx (C0, or just cocial)
D. Peripheral distribution
E. Where areas are innervated by the fibers found in the dorsal ramus?
1.skin and muscle of dorsal trunk
What areas are innervated by the fibers found in the ventral ramus?
1. All except thoracic nerves form plexuses
F. To what structure do the fibers found in the communicating rami connect?
1. associated with the ANS
G. What is a dermatome?
1. an area of skin supplied with sensory innervation by a pair of spinal nerves
What is the clinical significance of a dermatome?
1. Sense of touch
H. Nerve plexuses : Ventral rami of several nerves join to form a plexus
1. Means “Braid” and describes the organization produced by the intermingling of the nerves
How are the nerve plexuses formed?
1. The ventral rami of different spinal nerves called roots, join with each other to form a plexus
State which nerves are involved in the formation of each of the following plexuses.
Also state some of the major nerves which originate from each plexus.
1. Cervical : C1-C4 -
• Ansa Cervicalis (a loop between C1 & C3) - Infrahyoid muscles
• Phrebic Nerve : decends along each side of the neck to enter the thorax and then decend along
the sides of the medastinum to reach the diaphram
2. Brachial plexus : C5-T1 -
• 5 nerves of the upper limbs
• Axilary Nerve : deltoid and teres minor muscles plus sensory innervation to shoulder joint & skin over part of the shoulder
• Radial Nerve : midway down the shaft of the humerous in the radial groove. Innervates all extensor muscles of
•
• upper limb, supinator muscle & brachioradialis with cutaneous sensory distribution to posterior portion of upper limb including posteriot surface of hand.
Musculocutaneous Nerve : motor innervation to the anterior muscles of the arm as well as cutanious sensory innervation to part of the forearm
Ulnar Nerve : innervates two forearm muscles plus most of the intrinsic hand muscles, except some associated
•
• with the thumb. It’s sensory distribution is to the ulnar side of the hand
Median Nerve : innervates all but one of the flexor muscles of the forearm and most of the hand musscles at the base of the thumb, called thenar area of the hand. Cutanious sensory distribution is to the radial portion of the palm of the hand
Pectoral, Long Thoracic, Thoracodorsal, Subscapular & Suprascapular nerves
3. Lumbar plexus : L1-L4 -
• The Obturator: Median thigh, cutanious sensory distribution to medial side of thigh
• Femoral Nerves: Anterior thigh, cutanious sensory distribution toanterior & lateral thigh & medial leg and foot
• Tibial Nerve: posterior thigh, leg and foot - cutanious sensory distribution to calf of leg and plantar surface of the foot
Sciatic Nerve
• Common Fibular: Posterior thigh, anterior and lateral leg and foot - cutanious sensory distribution to lateral and
anterior leg and dorsom of the foot
• Gluteal nerves: innervate hip muscles that act on the femur
• Pudendal Nerve: Innervate the abdominal floor
• Ilioinguinal Genitofemoral & Cutaneous Femoral Nerve: Innervates skin of the suprapubic area, genetalia,
Superior medial and posterior thigh
4. Sacral plexus : L4-S4 -
5. Coccygeal plexux : S5 and C0 -

Materials Required: VanPutte/Seeley text Chapter 12
• Overview
• Thoracic Region
• Cervical Region
• Lumbar Region
• Typical Spinal Nerve
• Cervical Plexus • Brachial Plexus
• Upper Limb Anterior • Upper Limb Posterior
• Lumbosacral Plexus • Lower Limb Anterior
• Lower Limb Posterior
Use the materials listed above to complete the following performance objectives
a. conus medullaris b. cervical enlargement c. filum terminale d. lumbar enlargement e. cauda equina
a. locate and give the function of the following
1) dura mater
2) epidural space
3) arachnoid membrane
4) subdural space
5) pia mater
6) subarachnoid space b. state the two locations where cerebrospinal fluid can be found
a. identify the following structures on a cross-section drawing of the spinal cord:
1) *white matter
2) *lateral white column
3) *gray matter
4) *posterior (dorsal) white column
5) *central canal
6) ventral root
7) *posterior (dorsal) gray horn
8) dorsal root
9) *anterior (ventral) gray horn
10) dorsal root ganglion
11) *lateral gray horn
12) spinal nerve
13) *anterior (ventral) white column
14) *gray commisure
15) *anterior (ventral) median fissure
16) *posterior (dorsal) median sulcus b. be able to identify the structures indicated by * on the slide of the spinal cord (Refer to the Power Point Presentation) c. state where the sensory neuron cell body is located d. state where the motor neuron cell body is located e. state what neuron fibers are found in the dorsal root f. state what neuron fibers are found in the ventral root g. describe the symptoms a patient would have if damage occurred to the dorsal root, ventral root, or spinal nerve

a. state the number of spinal nerves b. define a sensory nerve c. define a motor nerve d. define a mixed nerve e. state whether the spinal nerves are sensory, motor, or mixed f. identify the five divisions of the spinal nerves and give the number of nerves in each division g. identify the opening through which the spinal nerves exit the vertebral column
Refer to the Power Point Presentation a. to list the following connective tissues and state where they are located: epineurium, perineurium, and endoneurium b. locate the epineurium, perineurium, and endoneurium on a slide
a. Identify the plexus from which the following spinal nerves originate:
1) phrenic
2) femoral
3) musculocutaneous
4) sciatic
5) ulnar
6) tibial
7) radial
8) common fibular (peroneal)
9) median
10) obturator
11) axillary
12) pudendal b. state the general area innervated by each of the nerves listed in Part a c. locate all of the above nerves and plexuses on the various lab drawings
a. list the five structures making up a somatic reflex arc b. list the six structures making up a visceral reflex arc c. define following terms as they relate to reflexes:
1) monosynaptic
2) polysynaptic
3) contralateral
4) ipsilateral d. demonstrate a simple tendon reflex such as the patellar or achilles reflex e. explain how conditions such as fatigue, activity, and concentration affect a reflex