spinal cord Flashcards
Where does the spinal cord arise cranially?
It arises cranially as a continuation of the brainstem at the medulla oblongata
Where does the spinal cord terminate?
L1/L2 vertebrae where it terminates as the conus medullary (medullary cone)
What anchors the spinal cord in place?
a thin thread called the filum terminale which extends from the tip of the conus medullaris to the first coccygeal vertebra
What does the medulla oblongata control?
autonomic functions
What does the medulla oblongata connect?
brain and spinal cord
What is the name of the collection of spinal nerve roots distal to the conus medullaris?
Cauda equina
What does the cauda equina consist of?
sacral and coccygeal spinal cord segments
What is the cauda equina vital for?
bladder control, urethral and anal sphincters and overall maintenance of continence
What is the filum terminale made up of?
made up of a delicate band of fibrous tissue
What is the spinal cord surrounded by?
spinal meninges containing cerebrospinal fluid
How many spinal nerves are there?
31 bilatterally paired spinal nerves
where is the cervical enlargement of the spinal cord?
located approximately at C4-T1 level
What does the cervical enlargement of the spinal cord represent?
The origin of the brachial plexus
Where is the lumbar enlargement of the spinal cord located?
between T11-L1 level
What does the lumbar enlargement of the spinal cord represent?
The origin of the lumbar and sacral plexi
What are spinal meninges?
a layered unit of membranous connective tissue that surrounds the spinal cord and cauda equina
What do spinal meninges provide?
protection
What are the 3 layers of meninges and where are they?
superficially starts with dura mater then the arachnoid mater and Pia mater is the deepest layer
Where does the dura mater extend from and go to?
extends from the foramen magnum to the filum terminale
What is the space between the vertebra and dura mater called?
epidural space
What does the epidural space contain?
the internal vertebral venous plexus
What happens with the dura mater as spinal nerves exit the vertebral canal?
They pierce the dura mater passing through the epidural space, the dura mater surrounds the nerve root and fuses with the outer connective tissue covering the nerve
What is the outer connective tissue covering the nerve called?
epineurium
What is the dura mater composed of?
tough and fibrous collagen fibres
What type of membrane is the arachnoid mater?
a delicate membrane
What separates the pia mater and arachnoid mater?
subarachnoid space
What does the subarachnoid space contain?
Cerebrospinal fluid
What does the subarachnoid space expand to form distal to the conus medullaris?
the lumbar cistern
Where is the lumbar cistern located?
between the end of the spinal cord and the end of the vertebral column
Describe the pia mater
thin membrane that covers the spinal cord, nerve root and their blood vessels
Inferiorly what does the pia mater fuse with?
filum terminale
What does the pia mater do between the nerve roots?
thickens to form the denticulate ligaments
What do the denticulate ligaments attach to?
dura mater
What do the denticulate ligaments prevent?
lateral movement
What divides the spinal cord into two symmetrical halves?
dorsal median sulcus and ventral median fissure
What do afferent spinal nerves enter the cord via?
dorsal/posterior root
What do efferent spinal nerves exit the cord via?
the ventral/anterior root
What is the white matter divided into?
structures called columns or funiculus
Name the 3 columns that the white matter has?
dorsal (posterior), lateral and ventral (anterior)
What is the grey matter divided into?
horns
Name the horns of the grey matter
dorsal (posterior), lateral and ventral (anterior)
What does grey matter consist of?
Grey matter mainly consist of neuron cell bodies, dendrites and synaptic contact
here do most synapses occur?
in the grey matter
What does the dorsal horn of the grey matter contain and do?
cell bodies of sensory neurons and relays sensory information
What do the ventral and lateral horns of the grey matter contain ad do?
cell bodies of motor neurons relaying information either descending from the brain or from the dorsal horn to motor and autonomic nerves respectively
What does grey commissure contain?
contains axons that cross to the opposite of the cord
What does white matter consist mainly of?
myelinated axons
Why do axons appear white?
due to the myelin sheath covering them
What are the two types of nerve fibres?
ascending (sensory) and descending (motor)
what do ascending tracts do?
carry afferent/sensory information to the brain in the posterior columns
What do descending tracts do?
Carry efferent/motor information from the brain to the spinal cord in the anterior and lateral columns
What does the anterior white commissure do?
interconnects anterior white columns where axons cross to the other side
Where are the dorsal and ventral horns larger in the spinal cord?
at the lumbar and cervical regions due to the number of tracts and output in the arms and legs
Where do spinal nerves originate from?
spinal cord
What do rootlets attach to?
the dorsolateral and ventrolateral aspects of the spinal cord
What does the posterior rami supply?
nerve fibres to the synovial joints of the vertebra, motor and sensory input to deep muscles of the back and overlying skin
What does the anterior rami supply?
nerve fibres to the majority of the body’s sesnorimotor innervation
all major neural plexus
cervical, brachial and lumbrosacral
describe a spinal stretch reflex
extensor muscle is stretched
muscle spindle is stimulated
primary afferent neuron is excited
primary afferent neuron stimulates alpha motor neuron to the extensor muscle
alpha motor neuron stimulates extensor muscle to contract
primary afferent neuron also stimulates the inhibitory interneuron at the same time
interneuron inhibits alpha motor neuron to the flexor muscle
flexor muscle (antagonist) relaxes
allowing the extensor muscle to contract without
what is a neural pathway?
a neural pathway is a bundle of axons that connects two or more different neurons
Where are neural pathways located?
Either soley in the brain, providing connections between several of its structures or link link the brain and spinal cord together
How many order neurons do ascending pathways have?
3
How many order neurons do descending pathways have?
2
What do ascending tracts carry?
sensory information to the periphery
Name the conscious ascending tracts
anterior spinothalamic tract
lateral spinothalamic tract
dorsal column medial lemniscus tract
name the unconscious ascending tracts
dorsal spinocerebellar
ventral spinocerebellar
cuneo-cerebellar
rostal spinocerebellar
What delicate sensations does the dorsal column transmit?
Vibration
proprioception
two point discrimination
What does the anterior spinothalamic tract?
crude touch and pressure
What does the lateral spinothalamic tract?
pain and temperature
What does the spinocerebellar tract transmit?
It transmits information ipsilaterally between the cerebellum and the body
Involved in coordination and posture maintenance
Where are the first order neurons of the ascending tracts found?
the dorsal root ganglia
Where are the second order neurons of the ascending tracts found?
usually found in the spinal cord or brainstem
Where are the third order neurons of the ascending tracts found?
usually found in the thalamus
What are the two types of descending tracts?
pyramidal and extra pyramidal motor tracts
Where do descending tracts originate from?
originate from the cortex or the brainstem
What are descending tracts involved in?
voluntary motion, involuntary motion, reflexes and regulation of muscle tone
Why is pyramidal named that?
because it forms a pyramid as it passes through the medulla oblongata
Name the pyramidal tracts
corticospinal
corticobulbar
Name the extra pyramidal tracts
reticulospinal
vestibulospinal
tectospinal
rubrospinal
Name the major neural pathway providing voluntary motor function
corticospinal tract
What tract is involved with speed and agility of voluntary movements?
corticospinal tract
What does the corticospinal tract do?
connects the cortex to the spinal cord to enable movement of distal extremities
Where does the lateral corticospinal tract decussate?
in the medulla
Where does the anterior corticospinal tract decussate?
spinal cord
What type of innervation does the corticospinal tract have?
contralateral
What type of innervation of anterior corticospinal tract have?
ipsilateral and contralateral control therefore the trunk muscles bilaterally cortically innervates
What do intrafusal fibres detect?
changes in length and velocity of the muscle
What do intrafusal fibres send?
sensory information tot he spinal cord
What are extrafusal fibres innervated by?
alpha motor neuron
What are intrafusal muscle fibres innervated by?
gamma motor neuron
What modulates the stretch reflex?
descending pathways from CNS
