CH 3: PNS: fibers of the spinal nerves Flashcards

1
Q

somatic nerves in the periphery=

A

the fibers that innervate the muscles, joints and skin of the body wall

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2
Q

visceral nerves in the periphery=

A

innervate the internal organs of the body cavities and blood vessels throughout the body

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3
Q

sensory fibers=

A

afferent

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4
Q

motor fibers=

A

efferent

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5
Q

general nerve fibers=

A

innervate skin, muscles, bones and viscera throughout the body

all nerve fibers in the spinal nerves are general

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6
Q

special nerve fibers=

A

reserved for sensory organs and muscles found only in unique regions in the head (retina, inner ear)

cranial nerves as a group contain both general and special fibers

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7
Q

general afferent fibers of the spinal nerves are ____ fibers with cells of origin in the _____

A

sensory fibers

dorsal root ganglia

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8
Q

dorsal root ganglia cells are

A

round and have only 1 process leaving the cell body.

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9
Q

the process from the dorsal root ganglia cells splits into..

A

1: peripheral branch: which enters the nerve
2: central branch: which passes through the dorsal root to the SC

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10
Q

general somatic afferent (GSA) fibers carry:

A

1: exteroceptive information:
2: proprioceptive information:

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11
Q

exteroceptive information from:

A

from receptors in the skin that mediate pain, temperature and touch

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12
Q

proprioceptive information from:

A

from sensory endings in muscles, tendons, and joints that mediate position sense, muscle length, rate of change of muscle length and muscle contraction

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13
Q

general visceral afferent (GVA) fibers carry:

A

interoceptive information

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14
Q

interoceptive information from:

A

from receptors in visceral structures that mediate data concerning distension and contraction of these structures

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15
Q

general efferent fibers are _____ fibers with cells of origin in the ______

A

motor fibers

spinal cord

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16
Q

general somatic efferent (GSE) fibers consist of:

A

motor fibers
originating from the cell bodies of alpha, beta and gamma motoneurons in lamina IX. These fibers innervate striated skeletal muscles

17
Q

general visceral effect (GVE) fibers consist of:

A

pre-ganglionic and post-ganglionic autonomic fibers that innervate smooth muscle and cardiac muscle and regulate glandular secretion.

pre-ganglionic fibers from the SC synapse on the cell bodies of post-ganglioic autonomic neurons

18
Q

nerve fibers can be categorized according to:

A

fiber diameter

conduction velocity of the nerve impulse

sensory vs. motor

19
Q

the larger the diameter of the fiber..

A

the thicker the myelin sheath and the greater the AP conduction velocity

20
Q

compound nerve=

A

nerve containing many motor and sensory fibers

21
Q

electrophysiological classification is based on:

A

the conduction velocities of different types of motor and sensory nerve fibers

22
Q

conduction velocities separate fibers into 3 groups:

A

A: myelinated
further subdivided

B: myelinated

C: unmyelinated

23
Q

A fiber groups are further divided on the basis of mean conduction velocity and hence fiber size:

A

A alpha fibers: large diameter; innervate EXTRAFUSAL muscle fibers (striated skeletal muscle outside the muscle spindles)

A gamma fibers: small diameter; innervate INTRAFUSAL muscle fibers (located within muscle spindles)

A beta fibers: intermediate sized; includes fibers that innervate both types of muscle

24
Q

C fibers are subdivided into 2 classes:

A

sC fibers: postganglionic efferent sympathetic C fibers

drC fibers: afferent dorsal root C fibers

25
Q

sensory fibers are also divided into 4 groups:

A

I-IV
differentiated chiefly on the basis of diameter (and thus speed of conduction)

also divide fibers into groups according to the sensory receptors they innervate

26
Q

A alpha

A

motor: axons of alpha motoneurons of lamina IX, innervating extrafusal muscle fibers

Ia: primary afferents of muscle spindles

Ib:afferents of golgi tendon organs, touch and pressure receptors

27
Q

A beta

A

motor: motor axons innervating both extrafusal and intrafusal (muscle spindle muscle fibers)

II:secondary afferents of ms spindles, touch and pressure receptors and Pacinian corpuscles (vibratory sensors)

28
Q

A gamma

A

motor: axons of gamma motoneurons of lamina IX, innervating intrafusal fibers (muscle spindles)

29
Q

A delta

A

III: small, lightly myelinated fibers; touch, pressure, pain and temperature receptors

30
Q

B

A

motor: small, lightly myelinated preganglionic autonomic fibers

31
Q

C

A

motor: postganglionic autonomic fiber (all unmyelinated)

IV: unmyelinated pain & temperature fibers