Chapter 13 - Spinal cord & spinal nerves Flashcards Preview

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Flashcards in Chapter 13 - Spinal cord & spinal nerves Deck (28):
1

Protective structures:

Vertebral column and the meninges (3) (protective CT layer) provide protect the spinal cord and provide physical stability. 

 

 

1) dura mater - superficial, continuous with brain dura mater, epineurium (outer layer of cranial/spinal nerve)

SUBDURAL SPACE

2) arachnoid mater - spiderweb arrangement

SUBARACHNOID SPACE

3) pia mater - deep, adheres to surface of CNS, denticulate ligament suspend spinal cord in middle of its dural sheath 

2

External anatomy of spinal cord 

(2) enlargements

1) conus medullaris

2) filum terminale 

 

cervical & lumbar enlargement

inferior to lumbar enlargement, spinal cord terminates at tapering conus medullaris 

extension of pia mater extending inferiorly & fuses to arachnoid & dura mater - filum terminale anchors spinal cord to coccyx

 

3

External anatomy of Spinal cord

 Posterior (dorsal) root & anterior(ventral) root 

 Posterior (dorsal root) ganglion 

cauda equina

 

roots = 2 bundles of axons that connect each spinal nerve to segment of cord by rootlets 

posterior (dorsal) root - only sensory axons, has swelling that contains sensory neuron cell bodies (posterior ganglion) 

anterior (ventral) root - only motor axons

cauda equina - roots of lumbar, sacral & coccygeal regions that run alongside filum terminale like wisps of hair

4

Internal Anatomy of Spinal Cord

1) anterior median fissure

2) posterior median sulcuss

3) gray & white commissures

4) central canal

5) anterior, posterior & lateral gray horns

6) anterior, posterior & lateral white columns

 

1) wide groove on anterior side 

2) narrow furrow on posterior side

3) gray- forms crossbar of H, white- connects white matter of left & right sides

4) space in center of gray commissure filled with CSF

5) gray matter subdivided into horns 

6) white matter divided into columns - contains bundles of axons with common destination (tracts) - sensory = ascending, motor = descending

5

White Matter 

Gray Matter

 

White - bundles of myelinated axons 

Gray - neuronal cell bodies & dendrites, unmyelinated axons & neuroglia

6

Nuclei 

functional clusters of neuronal cell bodies in gray matter

7

Spinal Nerve - 31 pairs; mixed nervs

Cervical (8) 

Thoracic (12) 

Lumbar (5)

Sacral (5) 

Coccygeal (1) 

8

Connective tissue covering of spinal nervs (3) 

define: fiber, fascicle & nerve

1) endoneurium - wraps individual axons within nerve

2) perineurium - wraps fascicles 

3) epineurium - wraps around entire nerve

 

fiber - single axon within endoneurium

fascicle - bundle of fibers within perineurium

nerve - bundle of fascicles with epineurium

9

Rami of Spinal Nerves

spinal nerve branches 

10

Rami of Spinal Nerves (2) 

 

posterior (dorsal) ramus - serve deep muscles & posterior skin of trunk

anterior (ventral) ramus - muscles/structures of limbs & skin of lateral & anterior trunk

11

All anterior rami form plexuses except?

T1-T11 

12

Cervical Plexus 

formed by anterior rami of C1-C5 

superficial & deep branches 

phrenic nerve - important (diaphragm)

13

Brachial plexus

formed by anterior rami of C5-C8 & T1

supplies shoulders & upper limbs

 

14

Brachial Plexus:

roots (unite)→ __..?

roots (unite)→ trunk (superior/middle/inferior) → divisions (anterior/posterior)→ cord (lateral/medial/posterior)→ nerves 

 

15

Important nerves that arise from brachial plexus (5) 

axillary 

musculocutaneous 

radial

median 

ulnar

16

Lumbar Plexus

formed by anterior rami of L1-L4

supplies anterolateral abdominal wall, external genitals, and part of lower limbs. 

Femoral & Obturator Nerves 

 

 

17

Sacral Plexus

anterior rami of L4-L5 and S1-S4

supplies butt, perineum & lower limbs

gives rise to large nerve in body - SCIATIC nerve

18

Coccygeal Plexus

Formed by anterior rami of S4-S5 and coccygeal nerves. 

supplies small area of skin in coccygeal region

 

19

Dermatome

the area of the skin that provides sensory input to CNS via 1 pair of spinal nerves or trigeminal nerve

20

Sensory and Motor Tracts

White matter tracts & gray matter

White Matter Tracts - highways for nerve impulse propogation

Gray matter - recieves & integrates incoming & outgoing info 

21

Reflex

fast, involuntary. unplanned response to a stimulus

22

Reflex Arc

pathway followed by nerve impulses that produce a reflex

23

A reflex arc includes (5)?

 

1) sensory receptor - responds to stimulus

2) sensory neuron - nerve impulse propogates to axon terminals in gray matter -> relay neurons to brain

3) integrating center 

4) motor neuron

6) effector

24

 
The Stretch Reflex

feedback mechanism to control muscle LENGTH

Causes contraction of skeletal muscle in response to stretching of muscle. 

monosynaptic

ipsilateral - same side

ex) knee jerk: stretching → activation of muscle spindles → sensory neuron →spinal cord →motor neuron → muscle contraction

 

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Tendon Reflex

feedback mechanism to control muscle tension by causing relaxation 

polysynaptic 

sensory receptor = golgi tendon organs

tension applied to tendon → tendon organ stimulated →nerve impulse →spinal cord →motor neuron → muscle relaxation to relieve tension

26

Flexor (withdrawal) Reflex

Stepping on a tack (stimulus) → nerve impulse → activation of interneuron → activation of motor neuron →muscle contraction withdrawal of the leg. 

polysynaptic 

ipsilateral 

 

27

Crossed Extensor Reflex

polysynaptic 

contralateral

Contraction of muscles that extend joints in opposite limb in response to a painful stimulus. 

Stepping on a tack (stimulus) → nerve impulse→activation of several 
interneurons → motor neurons → muscle contraction→ flexion of leg stepping on a tack & extension on opposite side. 

 

for maintaining balance

 

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