(Ch.13) Lesson 17: The spinal cord & spinal nerves Flashcards
How many spinal cord segments are there?
31 spinal cord segments
Where are spinal cords based?
Based on vertebrae where spinal nerves originate.
Do the positions of the spinal & vertebrae segments change?
Yes, they change w/ age
Why do the vertebrae & spinal segments change as you age?
As you age the vertebral column grows & ventral roots elongate.
How are cervical roots named?
They are named for the vertebra inferior to it
* The spinal nerve exits above the vertebrae it is named after
* All other nerves are named after their superior vertebra.
What are the 2 roots/branches of the spinal nerves?
- Ventral
- Dorsal
Ventral =
Axons of motor neurons
*Somatic and visceral effectors
Dorsal =
Axons of sensory neurons
Where is there spinal nerve located?
Found @ each side of the spine
1. Dorsal and ventral roots joins
2. Spinal nerve formed.
Dorsal roots + ventral roots =
Formation of spinal nerve
What do mixed nerves carry?
Carry afferent and efferent sensory fibers
What do mixed nerves carry?
Axons from ventral & dorsal roots
Explain what the spinal meninges specialize in.
Membranes the isolate spinal cord from the surroundings
What do the spinal meninges interact with?
Interact with the cranial meninges
What are the functions of the spinal meninges?
- Protecting the spinal cord
- Carrying blood to epidural & subarachnoid space
Explain what is meningitis
- Viral or bacterial meningitis
- Spinal meningitis or cerebral meningitis could disrupt CSF flow, damage or kill neurons & neuroglia
How does meningitis impact the body @ later stages?
Later stages of meningitis affect the entire meningeal system.
What are the 3 meningeal layers (in order of inner-outer)?
- Dura
- Arachnoid
- Pia
What are the physical characteristics of Dura mater?
- Tough & fibrous
- Cranially…
-Fuses w/ periosteum of occipital bone
-Continuous w/ dura mater - Caudally…
-Tapers w/ dense collagen fibers
- Joins filum terminal in coccygeal ligaments
Which space is located within the dura mater?
The epidural space
What is the epidural space?
The space between spinal dura mater and walls of vertebral canal/foramen
What type of tissue does the epidural tissue contain?
Contains loose connective tissue and adipose tissue
The epidural is which kind of site?
Anesthetic injection site
What is an epidural block?
Temporary sensory loss and possibly motor paralysis (mostly just sensory loss)
-Used at the inferior lumbar/sacral region for pain control during childbirth
- Only affects spinal nerves of the immediate area.
What layer is the arachnoid matter?
- Middle meningeal layer
- Arachanoid membrane
Which type of tissue layers the outer surface of the arachnoid matter?
Simple squamous epithelia
What are the interlayer spaces of arachnoid matter?
- Subdural space
- Subarachnoid space 0
An example/ of gray matter location controlling the body movement controlled
Cervical enlargement, from medial to lateral, somatic motor nuclei in the anterior horn control pectoral girdle, muscles of arm, forearm, hand, and fingers
Where is the subdural space located?
Between the arachnoid & dura mater
Where is the subarachnoid layer located?
Between the pia & the arachnoid mate.
List the physical characteristics that make up the subarachnoid layer.
- Contains collage/elastic fiber network (Arachnoid trabeculae)
- Filled with CSF
- Dorsal & ventral roots of cauda equina are located in subarachnoid space.
Within the meningeal layer where is the pia layer located?
The innermost layer
Describe the physical characteristics that make up the pia layer.
- Mesh of collagen & elastic fibers
- Bound to underlying neural tissue
- Blood vessels serving the spinal cord run along the surface of spinal pia matter within subarachnoid
What are the denticulate layers
Bilateral triangular lateral extensions of the pia mater anchor the spinal cord to the dura mater.
What are pair denticulate layers?
- Approximately 20-21 pairs
- Found on each side of the spinal cord
- Extend from pia mater to dura
- Stabilize lateral movement.
(Structure of spinal cord):
Blood vessels
- Found along the surface of spinal pia material
- Within subarachnoid space.
The sectional anatomy of the spinal cord consists of?
- White matter
- Gray matter
Characteristics of white matter?
- Superficial
- Contains myelinated & myelinated axons
Characteristics of gray matter
- Surround the central canal of the spinal canal
- Contains neurons cell bodies, neuroglia, unmyelinated axons
- Has projections (gray horns)
What does the organization of gray matter consist of?
- Gray horns
- Gray commissures
- Cell bodies of neurons form function groups called nuclei
- Sensory & location.
(Gray matter organization)
Different gray horns
- Posterior gray horn
- Anterior gray horn
- Lateral gray horn
(Gray matter organization):
Gray commissures (ant. & post.)
Axons that cross one side to the other side before reaching gray matter.
(Grey matter organzaion)
Cell bodies of neurons form function groups called nuclei, what are the different types of nuclei?
- Motor nuclei
- Sensory nuclei
(Gray matter organization)
Sensory & location
The sensory-motor nucleus’s location within gray matter determines which body part it controls.
(Grey matter)
What is the difference between motor and sensory nuclei?
Sensory:
1. Dorsal
2. Connects to peripheral receptor
Motor:
1. Ventral
2. Connect to peripheral effectors
Organization of white matter?
- Posterior white columns
- Anterior white columns
- Lateral white columns
(White matter)
Where do the Posterior white columns lie?
Lie between posterior gray horns and posterior median sulcus
What are the posterior white columns responsible for controlling?
- Proprioception
- Ventral pressure
- Fine touch
- Vibrations
(White matter)
Where do Anterior white columns lie?
Lie between anterior gray horns and anterior median fissure
What are anterior white columns responsible for controlling?
Crude touch & pressure, somatic motor
What are anterior white commissures?
Where axons cross from one side of the spinal cord to the other
(white matter)
Where do lateral white columns lie?
Located on each side of the spinal cord between posterior and anterior column
What are lateral white columns responsible for controlling?
Proprioception and somatic motor.
(Organizing white matter)
What are tracts/fasciculi?
- Bundles of axons in white columns
- Relay the same info to the same direction
What is ascending tract?
Responsible for carrying info to the brain
What are descending tracts?
Responsible for carrying motor commands to the spinal cord.
Why is the spinal cord so highly organized?
It allows for more accurate predictions of injuries to specific areas.
What is each spinal cord segment connected by?
They are connected by a pair of spinal nerves
What does each spinal nerve consist of?
- Surrounded by 3 connective tissue layers
- Supports strictures and connective blood vessels.
What are the 3 connective tissue layers that make up the spinal nerves?
(Eat. Patties. Earl)
- Epineurium
- Perineurium
- Endoneurium
The physical makeup of epineurium
Dense connective tissue of collagen fibers
Physical characteristics of perineurium
- Divided halves into fascicles
- Blood vessels found outside the fascicles
Physical characteristics of endoneurium
Surrounds individual axons
Explain what are peripheral nerves.
- Interconnecting branches of spinal nerves
- Surrounded by connective tissue sheaths
What are the peripheral distributions of spinal nerves?
- Spinal nerves
- Motor nerves
- Sensory nerves
- Desmatones
Explain how spinal nerves contribute to the peripheral distribution.
The spinal nerves contribute with the following…
- First branch (COMMUNICATION)
- Dorsal & Central rami
The first branch is made up of>
- White ramus
- Gray ramus
White ramus function is to?
(Found between T1 & L2)
Carry visceral motor fibers to sympathetic ganglion of the ANS
The function of the gray ramus?
- Unmyelinated nerves
- Return from the sympathetic ganglion to rejoin the spinal nerve before traveling to the target gland/smooth muscle.
Dorsal ramus functions?
- Contains somatic & visceral motor fibers
- Innervates the back
The function of ventra ramus?
- Larger branch
- Innervates ventrolateral struct & limbs
What are the sensory nerves responsible for?
They’re responsible for sensory info carried from the skin/skeletal muscle of the back, ventrolateral surface & visceral organs.
What are dermatomes?
- bilateral region of the body
- Monitored by a specific pair of spinal nerves
What causes peripheral neuropathy?
- Trauma
- Compression of nerve.
Explain how peripheral neuropathy affect the body.
It causes regional loss of sensory or motor function
How is shingles triggered?
Caused by chicken pox (herpes) virus & varicella-zoster virus (VZV)
Explain how shingles attack the nerves.
- The virus travels to the dermatome served by the affected sensory nerve
- Virus stays dormant in neurons of anterior gray horns of the spinal cord after chickenpox infection.
Is there a preventative treatment for shingles?
Antiviral VZV Vaccine (Zostavax)
What are the 4 plexuses of ventral rami?
- Cervical
- Brachial plexus
- Lumber plexus
- Sacral plexus
How are the nerve plexuses formed?
They are formed from blended fibers of ventral rami of adjacent spinal nerves
What are the nerve plexuses responsible for controlling?
The control skeletal muscles of the neck & limbs.
Describe the physical characteristics that makeup nerve plexuses.
Complex, interwoven networks of nerve fibers
What does the cervical plexus include?
- Ventral rami of spinal nerves C1-C5
- Innervates neck, thoracic cavity, diaphragmatic muscles
Which major nerve is located within the cervical plexus?
Phrenic nerve (C3-C5)
What is the phrenic nerve responsible for>
The phrenic nerves is responsible for controlling the diaphragm.
What can damage to the phrenic nerve cause?
It can cause you to stop breathing. Other branches of this nerve innervate skin of neck and superior chest.
What does the brachial plexus include?
- Included ventral rami of spinal nerves (C5-T1)
What does the brachial plexus innervate?
It innervates pectoral girdle and upper limbs.
Which major nerves are found within the brachial plexus?
- Musculotaneous nerve
- Radial nerve
- Median nerve
- Ulnar nerve
- Axillary nerve
Musculocutaneous nerve
Responsible for arm flexion
Receives sensory info
on the lateral surface of the forearm
Radial nerve
Extensor muscles of arm and forearm
receives sensory info from posterolateral surface
Median nerve
- Flex the forearm
- Receives sensory info from anterolateral hand
Ulnar nerve
- Flex hand
- Receives sensory info from medial surface of hand
Axillary nerve
Deltoid muscle for the abduction of arm
What includes the lumbar plexus?
Included ventral rami of spinal nerves (T12-L4)
What does the lumbar plexus innervate?
Anterolateral abdominal wall, genitals, lower limbs.
Which major nerves are found within the lumbar plexus?
The femoral nerve- serves the medial & anterior compartments of the leg.
What does the sacral plexus include:
Includes ventral rami of spinal nerves (L4-S4)
What does the sacral plexus innervate?
The sacral plexus innervates the buttocks, perineurium, and lower limbs.
Which major nerves are found within the sacral plexus?
- Fibular/sural nerve
- Tibial nerve
Fibular nerve- sural nerve
Formed from a fibular nerve that innervates the lateral portion of the foot (part of this nerve is used in nerve grafts.
(Function organization of neurons)
Sensory neurons
- About 10 million
- Deliver info to the CNS
(Functional organization of neurons)
Motor neurons
- About 1/2 million
- Deliver commands to peripheral effectors
(Functional organization of neurons)
Interneurons
- About 20 billion
- Interpret, plan, and coordinate signals that go in and out.
List the 5 patterns of neural circuits in neuronal pools.
- Divergence
- Convergence
- Serial processing
- Parallel processing
- Reverberation
What are neuronal pools?
- Functional groups of interconnected neurons
- Each with limited input sources and output destinations
- May stimulate or depress parts of brain or spinal cord.
What are neural circuits?
‘wiring of neurons’ in neuronal pools.
Example of divergence
- Visual info goes to the visual cortex and postural/balance areas
What pattern does divergence show?
Spread stimulation to many neurons or neuronal pools in CNS
What does the convergence pattern show?
Brings input from many sources to single neuron
What is an example of convergence
Subconscious and conscious control of breathing
How does serial processing move?
Move information in single line
What is an example of serial processing
Relays pain info.
How does information move during parallel processing?
Moves same information along several paths simultaneously
What is an example of parallel processing?
- Step onto nail
- You withdraw foot
- Shift weight
- Feel pain
- Scream
How is information moved around during reverberation?
- Positive feedback mechanism
- Functions until inhibited
- May help maintain consciousness, muscle coordination, and normal breathing.
