Chapter 13 - Spinal cord & spinal nerves Flashcards
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
**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
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
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
White Matter
Gray Matter
**White - **bundles of myelinated axons
**Gray - **neuronal cell bodies & dendrites, unmyelinated axons & neuroglia
Nuclei
functional clusters of neuronal cell bodies in gray matter
Spinal Nerve - 31 pairs; mixed nervs
Cervical (8)
Thoracic (12)
Lumbar (5)
Sacral (5)
Coccygeal (1)
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
Rami of Spinal Nerves
spinal nerve branches
**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
**All anterior rami **form **plexuses **except?
T1-T11
Cervical Plexus
formed by **anterior rami of C1-C5 **
superficial & deep branches
phrenic nerve - important (diaphragm)
Brachial plexus
formed by anterior rami of C5-C8 & T1
supplies shoulders & upper limbs
Brachial Plexus:
roots (unite)→ __..?
roots (unite)→ **trunk (superior/middle/inferior) → **divisions(anterior/posterior)→ cord(lateral/medial/posterior)**→ nerves **
Important nerves that arise from **brachial plexus **(5)
axillary
musculocutaneous
radial
median
ulnar
Lumbar Plexus
formed by** anterior rami of L1-L4**
supplies anterolateral abdominal wall, external genitals, and part of lower limbs.
**Femoral & Obturator Nerves **
Sacral Plexus
anterior rami of L4-L5 and S1-S4
supplies butt, perineum & lower limbs
gives rise to large nerve in body - SCIATIC nerve
Coccygeal Plexus
Formed by anterior rami of S4-S5 and **coccygeal nerves. **
supplies small area of skin in coccygeal region
Dermatome
the area of the skin that provides sensory input to CNS via 1 pair of spinal nerves or trigeminal nerve
Sensory and Motor Tracts
White matter tracts & gray matter
**White Matter Tracts - **highways for nerve impulse propogation
**Gray matter - **recieves & integrates incoming & outgoing info
Reflex
fast, involuntary. unplanned response to a stimulus
Reflex Arc
pathway followed by nerve impulses that produce a reflex
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
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
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
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 **
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
