Biomechanics of NS Flashcards
True/False: The Nervous System must be able to tolerate mechanical loading, move, and physically interface with adjacent tissue.
True, duh
What is the basic functional unit of the NS?
neuron
What are the parts of a neuron?
perikaryon, dendrites, axon
What is the perikaryon?
contains the neuron cell body.
is housed in the ventral horn of the SC, sympathetic trunk, and dorsal root ganglia)
Which of the following is not true for the axon?
a. multiple fibers extending from the cell body with branches near termination
b. site of impulse conduction
c. conduction speed increases with myelination
d. conduction speed correlates with fiber diameter
a - it is a single fiber
d- increased conduction velocity occurs in fibers with larger diameters
What is the dendrite?
branches from cell body and terminal axon, increase the number of synapses
Where is the brain entirely housed?
cranium
Which of the following is not true?
a. the SC is a continuation of the medulla oblongata from the foramen magnum
b. The SC terminates at the conus medullaris at T10
c. the SC attaches into the coccyx via filum terminale
d. nerve roots are the transitional structure from the CNS to the PNS
b - ends at L2
Match the meninge to the description,
a. pia mater
b. arachnoid mater
c. dura mater
i. delicate connective tissue meshwork housing CSF
ii. delicate and continuous layer of connective tissue meshwork surrounding all elements of the CNS
iii. tightly outermost meningeal layer with high collagen content aligned in layers longitudinally
iv. connects into pia mater via arachnoid trabeculae
v. highly vascularized and innervated
a = ii, b = i and iv, c = iii and v
Describe the structural hierarchy of the peripheral nervous system.
innermost, smallest unit is the nerve fiber housing axons within basement membrane and endoneurium.
bundle of nerve fiber = fascicle, surrounded by perineurium then epineurium.
bundle of fasciculi is a peripheral nerve trunk, enveloped by loose areolar tissue layer (mesoneurium)
What are the supporting cells between neurons, involved in myelination?
neuroglia
_ cells of the CNS, _ cells of the PNS.
oligodendrites, schwann
What do the pia and arachnoid mater allow?
stretch and compression without kinking
What does the dura mater provide?
tremendous axial loading strength and relative structural stability
What do the peripheral connective tissues provide?
protection and resistance to tensile and compression forces
Which of the following is not true for the connective tissue functions within the NS?
a. adds both tensile strength and elasticity to nervous tissue where movement is necessary
b. adds structural stability through attachments to adj structures
c. facilitates processes involved in nutrition, oxygenation, and waste removal
d. it and nervous tissue are highly innervated and nociceptive
e. influences interactions with endocrine and immune system
d - it is highly innervated but nervous tissue itself is not
Which of the following is true regarding NS integration with the vascular system?
a. 45% of oxygen utilized by NS, which is 5% of body mass
b. CNS but not PNS has extensive intrinsic vascular systems
c. susceptible to mechanical compression and tensions which can alter blood flow
d. both NS and VS are highly innervated and nociceptive
C is true. A = 20% and 2%, B = both have them, D = nervous tissue is not
The nervous system tissues are mechanically continuous by what means?
connective tissue associations
The NS tissues are electrically continuous by what means?
impulse generation and transmission
The NS tissues are chemically continuous by what means?
flow of neurotransmitters
What are the NS functions?
- conducts and regulate impulses via continuous electrochemical antegrade and retrograde flow
- associate physical, psychological, and environmental inpyts
- adapt dynamically to maintain and change its own function
- facilitate coordinated conscious and unconscious reactions of multiple body systems
What are the determinants of the mechanical properties of the NS?
continuity of nervous tissue tract;
supporting connective tissue structures;
PNS: interneural and intraneural plexus formation, and quantity of fascicles housed within nerve;
CNS: folding and twisting of axons, and nervous tissue movement in relation to neighboring bony segments
What serves to distribute force within combinations of nerves?
interneural plexus in PNS
What serves to distribute force within specific nerves?
intraneural plexus in PNS
True/False: Nerve compression with greater pressure is required to affect nerve fibers in a nerve with a greater number of fascicles.
false - smaller number of fascicles
What does redundancy within the tissues of the CNS allow?
neural structures to elongate prior to being exposed to significant tensile forces
True/False: Normal movement of the body requires the tissues of CNS to be able to move past adj structures in which they are housed.
true
What are the mechanical loads that the nervous system is exposed to?
compression, tension, excursion
Which type of mechanical load can lead to alterations in fluid and blood flow within neural tissue at relatively low pressures?
compression
True/False: Exposure to compression is normal if magnitude and duration is not excessive.
true
What does increased tensile loading lead to?
decreased cross sectional area and increased intraneural pressure = decrease blood flow @ 6-8% strain, stops at 15% strain
What occurs do to excursion loads on neural tissues?
“slide” relative to adj interfacing extraneural tissues
What can mechanical loading of nervous tissue result in?
altered axoplasmatic flow within a nerve and altered blood supply to a nerve
Treatment should avoid excessive loading of nervous tissue and usually focus on what?
relieving stresses and strains upon nerves
