CNS / spinal cord

Question 1

Intro info

Answer 1

• extends from the foramen magnum to the lower border of L1 (18 inches) - oval cylinder that taper slightly as it descends - two bulges, one in C and one in L - two deep groves: anterior median fissure (deeper and wider) and posterior median fissure

Question 2

Dorsal nerve root fibers

Answer 2

Posterior - carry sensory info into the spinal cord - cell bodies of these sensory neurons make up a small region of gray matter (dorsal root ganglion)

Question 3

Ventral nerve root fibers

Answer 3

Anterior - carry motor info out of the spinal cord - cell bodies of these motor neurons are located in the gray matter of the spinal cord

Question 4

Answer 4

Question 5

Conus medullaris

Answer 5

Spinal cord ends at vertebra L1 in a tapered cone

Question 6

Causa equina

Answer 6

Bundle of nerve roots extending from the conus medullaris at the inferior end of the spinal cord

Question 7

Gray matter

Answer 7

Consists predominantly of cell bodies of interneurons and motor neurons - extend the length of the cord - left and right gray columns are joined in the middle by a band called the gray commissure - central canal carries CSF through the spinal

Question 8

White matter

Answer 8

Surrounds the gray matter and is subdivided in each half of the cord into three columns (funiculi): ant, post, and lateral - each column consists of a large bundle of axons divided into tracts - names of spinal tracts indicate the location of the tract, the structure in which the axons originate, and the structure in which they terminate

Question 9

Functions of spinal cord

Answer 9

Provides conduction routes to and from the brain - serves as the integrator or reflex center, for all spinal reflexes

Question 10

Ascending tracts (conduction routes)

Answer 10

Conduct sensory impulses up the cord to the brain

Question 11

Descending tracts (conduction routes)

Answer 11

Conduct motor impulses down the cord from the brain

Question 12

Conduction routes

Answer 12

Bundles of axons compose all tracts - tracts are both structural and functional organizations of nerve fibers

Question 13

Lateral spinothalamic tract

Answer 13

Ascending - crude touch - pain - temp

Question 14

Anterior spinothalamic tract

Answer 14

Ascending - crude touch - pressure

Question 15

Posterior column-medial lemniscus tract

Answer 15

Ascending - fasciculi gracilis and cuneatus - discriminating touch

Question 16

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Question 17

Spinocerebellar

Answer 17

Ascending - subconscious kinesthesia

Question 18

Spinotectal

Answer 18

Ascending - touch that triggers visual reflexes

Question 19

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Question 20

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Question 21

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Question 22

Lateral corticospinal tract

Answer 22

Descending - decussate in the medulla - voluntary movements on opposite side of the bod

Question 23

Anterior corticospinal tract

Answer 23

Descending - voluntary movements on opposite side of the body

Question 24

Recticulospinal tract

Answer 24

Descending - maintain posture during movement

Question 25

Rubrospinal tract

Answer 25

Descending - transmit impulses that coordinate body movements and maintenance of posture Conveys impulses from the red nucleus (rubro)

Question 26

Tectospinal tract

Answer 26

Descending - moves head, eyes, and trunk in response to visual or auditory stimuli

Question 27

Vesibulospinal tract

Answer 27

Descending - conveys impulses from vestibular nucleus to ipsilateral skeletal muscles of trunk and proximal parts of limbs fro posture and balance in response to head movements

Question 28

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Question 30

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Question 31

Somatic sensory pathways

Answer 31

For the cerebral cortex to perform its sensory functions, impulses much first be conducted to sensory areas via relays of neurons (sensory pathways) - watch side of the brain registers sensations from the opposite side of the body (crossed pathways)

Question 32

Somatic motor pathways

Answer 32

Impulses are conducted from motor areas to skeletal muscles via motor neurons by (motor pathways) - the cardinal principle about somatic motor pathways is the final common path

Question 33

Final common path

Answer 33

Each motor neuron from the anterior gray horn (ventral) of the spinal cord conducts impulses to a specific motor unit within a skeletal muscle (only 1 final common path) - axons from the anterior gray horn are the only ones that terminate in skeletal muscle cells

Question 34

Clinical significance of somatic motor pathways

Answer 34

Any condition that makes ventral horn motor neurons unable to conduct impulses also makes skeletal muscle cells supplied by these neurons unable to contract - produces flaccid paralysis by destroying ventral horn motor neurons - polio

Question 35

Pyramidal tracts

Answer 35

Fibers converge in medulla - aka corticospinal tracts - important for stimulation and precise control of voluntary muscle function

Question 36

Extrapyramidal tracts

Answer 36

Much more complex - 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 groups

Question 37

Answer 37