spinal cord Flashcards
- lies within the spinal cavity and extends from the foramen magnum to the lower border of the first lumbar vertebra - oval cylinder that tapers slightly as it descends - 2 bulges, one in cervical region and one in lumbar region
structure of the spinal cord
the 2 bulges in the spinal cord are called:
- cervical enlargement - lumbar enlargement
the anterior median fissure and the posterior median sulcus are two deep grooves; _____ fissure is deeper and wider
anterior
cervical enlargement extends from ___ to ___.
C4 to T1
lumbar enlargement extends ____ to ____.
T9 to T12
termination of the spinal cord. Tapers in a cone shape and ends at the level of the intervertebral disc between L1-2
Conus Medullaris
2 bundles of nerve fibers project from each side of the spinal cord are called
nerve roots
- carry sensory info into the spinal cord
fibers of dorsal (posterior) nerve root
cell bodies of these sensory neurons make up a small region of gray matter called:
dorsal root ganglion
- carry motor info out of the spinal cord
fibers of ventral (anterior) nerve root
cell bodies of these motor neurons are located in the ______ of the spinal cord
gray matter
_____ are located in the spinal cord’s gray matter core
interneurons
on each side of the spinal cord, the dorsal and ventral nerve roots join together to form a single mixed nerve called a:
spinal nerve
the spinal cord ends at:
L1
bundle of nerve roots extending from the conus medullaris at the inferior end of the spinal cord
cauda equina
_____ consists predominantly of cell bodies of interneurons and motor neurons and extend the length of the cord
gray matter
the left and right gray columns are joined in the middle by a band called the:
gray commissure
_____ carries CSF through the spinal cord
central canal
white matter surrounds gray matter and is subdivided in each half of the cord into three columns (funiculi):
- ant - post - lat white columns
Each white column consists of a large bundle of axons divided into tracts. Names of spinal tracts indicate:
- location of the tract - structure in which the axons originate - structure in which they terminate
2 main functions of the spinal cord:
- provides conduction routes to and from the brain - serves as the integrator, or reflex center for all spinal reflexes
- conduct sensory impulses up the cord to the brain
ascending tracts
- conduct motor impulses down the cord from the brain
descending tracts
tracts are both ____ and ____ organizations of nerve fibers composed of bundles of axons
structural and functional
ascending tract that deals with crude touch, pain, and temperature
lateral spinothalamic
ascending tract that deals with crude touch and pressure
anterior spinothalamic
ascending tract that deals with discriminating touch and conscious kinesthesia
posterior column-medial lemniscus
ascending tract that deals with subconscious kinesthia
spinocerebellar
ascending tract that deals with touch that triggers visual reflexes
spinotectal
descending tract that deals with voluntary movements on opposite side of the body (decussate in the medulla)
lateral corticospinal
descending tract that deals with voluntary movements on opposite side of the body
anterior corticospinal
descending tract that maintains posture during movement
reticulospinal
descending tract the transmits impulses that coordinate body movements and maintenance of posture (conveys impulses from the red nucleus)
rubrospinal
descending tract that moves head, eyes and trunk in response to visual or auditory stimuli
tectospinal
conveys impulses from vestibular nucleus to ipsilateral skeletal muscles of trunk and proximal parts of limbs for posture and balance in response to head movements
vestibulospinal
for the cerebral cortex to perform its sensory functions, impulses must first be conducted to sensory areas via relays of neurons referred to as:
sensory pathways
each side of the brain registers sensations from the opposite side of the bosy
crossed pathways
impulses are conducted from motor areas to skeletal muscles via motor neurons by:
somatic motor pathways
the cardinal principle about somatic motor pathways:
principle of the final common path
each motor neuron from the anterior gray horn (ventral horn) of the spinal cord conducts impulses to a specific motor unit within a skeletal muscle. axons from the anterior gray horn (ventral horn) are the only ones that terminate in skeletal muscle cells
principle of the final common path
any condition that makes ventral horn motor neurons unable to conduct impulses also makes skeletal muscle cells supplied by these neurons unable to contract.
clinical significance of somatic motor pathways
- fibers converge in medulla - AKA corticospinal tracts - important for stimulation and precise control of voluntary muscle function
pyramidal tracts
- much more complex than pyramidal tracts - all motor tracts from the brain to spinal cord - ventral horn motor neurons except corticospinal tracts - important in larger, automatic movements - sequencing or simultaneous contraction of muscle group
extrapyramidal tracts
_#_% of corticospinal tracts are pyramidal, lateral and anterior corticospinal tracts voluntary movement
90
_#_% of corticospinal tracts are extrapyramidal. They are more reflexive and automatic
10
