Test 1 Flashcards
What are the classifications and characteristics of A fibers?
alpha, beta, gamma, delta; fast, sharp, well-localized sensation
Name whether or not A, B, C fibers are myelinated or non-myelinated.
A and B are myelinated and C is non-myelinated.
What are the characteristics of C fibers?
slow, prolonged, poorly-localized; non-myelinated
What is the innervation, function, conduction velocity, and diameter of A-alpha fibers?
muscle spindle motor to skeletal; proprioception, motor; 15um; 100 m/s
What is the innervation, function, conduction velocity, and diameter of A-beta fibers?
touch and pressure afferents; touch, pressure; 10um; 50 m/s
What is the innervation; function, conduction velocity, and diameter of A-gamma fibers?
motor to muscle spindles; muscle spindles; 5um; 25 m/s
What is the innervation, function, conduction velocity, and diameter of A-delta fibers?
mechanoreceptors, nociceptors; pain (sharp), temperature; <5um; 25 m/s
What is the innervation/function, conduction velocity, and diameter of Type B fibers?
sympathetic pre-ganglionic, autonomic; <3um; 10 m/s
What is the function, conduction velocity, and diameter of Type C-dorsal root fibers?
pain (dull), temperature; 1um; 1 m/s
What is the function, conduction velocity, and diameter of Type C-sympathetic fibers?
post-ganglionic; 1um; >1 m/s
Review the image for interscalene block.
The targets of anesthesia for this block are the roots and proximal trunks of the brachial plexus where they are sandwiched between the anterior and middle scalene muscles at the level of the sixth cervical vertebra (C6).
The trunks are contained within the interscalene fascial sheath at this level. This block is indicated mostly for surgical anesthesia to the shoulder, upper arm, and forearm, but is often insufficient for the hand. A continuous block via interscalene catheter provides excellent analgesia after shoulder arthroplasty.
Identify the landmarks for the interscalene block.
The main surface landmark (sternocleidomastoid muscle) used for this block can be accentuated by asking the patient to reach for the ipsilateral knee and by rotating the head approximately 45º to the non-operative side. The head should also be slightly elevated, and the patient should be instructed to take a deep breath (contraction of the scalenus muscles accentuates the interscalene groove).
The interscalene groove lies immediately behind the lateral border of the clavicular head of the sternocleidomastoid muscle at the level of the cricoid cartilage (C6) and is located approximately 1 cm above the separation of the sternal and clavicular heads of the sternocleidomastoid muscle.
Define Transduction:
Noxious stimuli translated into electrical activity at the sensory nerve endings
Define Transmission:
Propagation of impulses throughout the sensory nervous system.
Define Modulation:
Efferent control of pain.; Modulation is telling the body “its not going to be so bad”.
Label the following structures of the Myelinated Nerve Fiber:
Ultrastructural features of myelinated (A) and unmyelinated (B) nerve fibers. (1) Nucleus and cytoplasm of a Schwann cell; (2) axon; (3) microtubule; (4) neurofilament; (5) myelin sheath; (6) mesaxon; (7) node of Ranvier; (8) interdigitating processes of Schwann cells at the node of Ranvier; (9) side view of an unmyelinated axon; (10) basal lamina.
Picture of anatomy of peripheral nerve:
Picture of the Unmyelinated Nerve Fiber:
________ or _______ pathways transmit pain, temperature, pressure, touch, vibratory sense, and proprioceptive information to the CNS.
Sensory or Afferent
Receptors for pain and temperature are located in the ________ and _______; those for pressure, touch, vibratory sense, and proprioception are located in the ________.
epidermis; dermis; dermis
Receptors can be classified as _______, which are located near the surface of the skin and oral mucosa, and _________, which are located in deeper skin layers, joint capsules, ligaments, tendons, muscles, and periosteum.
exteroceptors; proprioceptors
______ order neurons in the ganglia reach the spinal cord and synapse with the ______ order neuron.
first; second
What is a the primary site of opioid spinal analgesia?
substantia gelatinosa; apex of the posterior horn of the gray matter of spinal cord is capped by a V-shaped mass of translucent, gelatinous neuroglia called S.G.; Many mu and k opioid receptors, presynaptic and postsynaptic are found on these nerve cells; it is gelatinous due to low concentration of myelinated fibers.
How many cervical vetebrae exist in the human spinal cord?
7
How many cervical nerves exist in the human spinal cord?
8
How many thoracic vertebrae exist in the human spinal cord?
12
How many lumbar vertebrae exist in the human spinal cord?
5
Where does the spinal cord begin and end in the adult human vertebrae?
begins at the occipital bone and extends down between the first and second lumbar vertebrae; specifically, from the foramen magnum through to the conus medullaris near the second lumbar vertebrae; terminates in a fibrous extension known as the filum terminale (cauda equina)
How many sacral segments exist in the human spinal column?
S1-S5
How many pairs of spinal nerves exist in the human spinal vertebrae?
31 pairs; 1 pair for each segment; except 8 total for the 7 cervical, and 1 total for the 3 coccygeal segments
Of the Type A fibers, which is the slowest to be blocked? fastest?
Type A alpha is slowest, Type A delta is fastest (based on sensitivty to block on powerpoint chart)
How do local anesthetics work?
they reversibly decrease the rate of depolarization and repolarization; mainly act by inhibiting sodium influx through sodium-specific ion voltage gated channels in the neuornal cell membrane; action potential normally increases with the rush in of Na+
Tell whether dorsal and ventral are efferent or afferent.
Remember “DAVE”; Dorsal afferent, Ventral Efferent
What nerve fiber comes first in the order of a block?
Light myelinated Type B fibers; they are preganglionic/autonomic fibers with high sensitivity (based on graph in slides)
Describe visceral pain.
results from activation of nociceptors of the thoracic, pelvic, or abdominal viscera (organs); often diffuse, difficiult to localize and referred to as distant; can be a sharp pain and may increase in discomfort with deep breathing
Which fiber can be associated with a patient in acute sharp pain? Also associated with temperature.
A delta fiber
What is the sensory pathway originating in the spinal cord that transmits information to the thalmus about pain, temperature, itch, and crude touch?
The spinothalamic tract
Which part of the spinothalamic tract transmits pain and temperature?
lateral
Which part of the spinothalamic tract transmits crude touch and pressure?
anterior (ventral)
According to the Gokin article, what fibers were the most susceptible to minimal lidocaine concentrations?
Faster conducting C-fibers were more susceptible than slower ones. At 1% lidocaine, all fibers were tonically blocked.
Put the following in the correct order of “block”: A-Beta, B, A-delta, A-gamma, A-Alpha, C
B, C & A-delta, A-gamma, A-Beta, A-Alpha
Are C-fibers efferent or afferent?
They are both.
Review the following image.
Name the fiber that is a primary afferent fiber, large in diameter, fast-conducting (travel rate of 20 m/s), and myelinated.
A-delta fibers; they respond only to mechanical stimuli over a specfic intensity and are associated with a sharp, localized, and pricking quality of pain.
What is the neurotransmitter in the dorsal hor and the receptor that it acts on for an A-delta fiber?
Glutamate acting on AMPA receptors
What is the neurotransmitter in the dorsal horn for C-fibers, and the receptors they act on?
Glutamate along with certain peptides such as substance P and the receptors for glutamate are AMPA and N-methyl-D-asparate (NMDA)
The mode of transmission of an action potential through each node of Ranvier in myelinated nerve cells is called?
Saltatory conduction
Name the layers of a neuron from the outermost layer inwards:
epineurium, perineurium, fasicle, endoneurium
When are muscle tissues most sensitive?
during contraction and ischemia
What actions cause pain to visceral tissue?
sensitive to twisting and distention; insensitive to cutting, heating, and pinching (think of what they do during lap procedures)
How many milligrams of lidocaine are present in 15ml of 1% solution?
150mg
If you have a T-6 sensory block, what level is the sympathetic and motor block?
T-8 for motor and T-4 for sympathetic
When injection local anesthetic for an epidural, you inject into the _______ space; for a spinal you inject into the __________ space.
epidural; sub-arachnoid
At every level of the spine, nerve roots exit the central nervous system and enter the peripheral nervous system through openings called the _______.
foramina
The position of the white matter and gray matter in the spinal column is opposite to the brain. The white matter is in the _______ and the gray matter is _______ and has a _______ shape.
periphery; central; butterfly
Between what two vertebrae does the C8 nerve exit through?
T1 and C7; each nerve exits between the upper set of vertebrae (ex: C7 exits b/w C6 and C7)
There is a strong correlation between volume and the cranial migration of local administration in the epidural space. Do larger volumes increase or decrease the cephalad distribution of local anesthetics?
increases; epidural administration naturally has a cephalad migration
When performing a spinal you draw a horizontal line from the top of the iliac crest. What is this line called and what spinous process does it intersect?
Tuffier’s line; passes through L4 spinous process
How many vertebrae are in the lumbar spine?
How many vertebrae are in the cervical spine?
7
How many vertebrae are in the thoracic spine?
12
What 3 ligaments do you penetrate when performing an epidural or spinal?
supraspinous, interspinous, and ligamentum flavum