Week 4- Spinal Cord Flashcards
What is white matter
Mixture of nerve fibres,neuroglia, blood vessels
Myelinated- white colour
Name 1st order neuron
Cerebral cortex
name 2nd order neuron
Internucial neuron in anterior grey column
Name 3rd order neuron
Motor neurons in anterior grey column of spinal cord
Describe the structure of the spinal cord
-inner core is grey matter
-H shaped pillar with anterior and posterior columns/horns
-small central canal
-surrounded by outer white matter
-divided into anterior, lateral and posterior white columns
What is grey matter proportional to
The amount of muscle innervated at that level
Where is grey matter largest
Cervical and lumbosacral region
What does grey matter consist of
Nerve cells
Neuroglia
Blood vessels
Where is the cervical enlargement
4th C- 2T
Where is limbo-sacral enlargement
2 L- 3S cord segment
How many spinal nerves are attached to spinal cord
31 pairs
What are spinal nerves attatched to
Anterior/ ventral (motor roots)
Posterior/dorsal (sensory roots)
what does each spinal posterior nerve possess
Posterior root GANGLION
What are ganglia
Clusters of nerve cell bodies that carry nerve signals to and from CNS
What are sensory ganglia
Ovoid shape with an oval cell body
What are motor ganglia
They form a long chain in the spine from the base of skull to tail.
Irregular shaped cell bodies
What do anterior + posterior Ramus have
Sensory fibres and motor fibres
s anterior or posterior ramus larger
Anterior= larger
Posterior= smaller
What is the cauda equina
Collection of nerves at the end of spinal cord
What is the size of cervical and thoracic canal
Cervical= large
T= small
Describe problems with paraplegic
Limited mobility
Chronic pain
Reduced bowel and bladder function
Loss of sexual function
Loss of muscle tone in legs
Weight gain
What level is quadriplegic paralysis
Cervical
Name problems with quadriplegic
-Limited / complete absence of arm/hand function
-Problems speaking, swallowing or breathing without assistance
-difficulty performing daily tasks, dressing, eating
-muscle tone loss
-loss of bone density
List levels of spinal cord injury
A= complete injury. No function or sensation at the end of the cord
B=sensory incomplete. Sensory but not motor function retained
C=motor incomplete. Motor function is present to the end of spinal cord.
D= muscle function below level of injury is against gravity
E= normal
What cells control spinal cord function
Long axons
Sensory neurons
Spinal interneurons
Describe how long axons assist in spinal cord function
Control skeletal muscles in neck torso and limbs called motor neurons
Describe how sensory neurons assist in spinal cord function
Dorsal root ganglia cells/ afferent cary info from bidy to spinal cord. Found outside spinal cord
Describe how spinal interneurons assist in spinal cord function
Cells that help integrate sensory info with generate coordinated signals that control muscles, lie within spinal cord
Describe myelin
-white fatty substance produced by Schwann cells
-outer nerves coated with myelin (white matter)
-inner spinal cord nerves not coated with myelin (grey matter)
Describe peripheral nerves
Cranial and spinal nerves
Consist of parallel bundles of fibres that may be efferent of afferent axons
Surrounded by ct sheaths
Define reflex
Involuntary response to stimulus
What does a reflex arc consist of
Receptor organ
Afferent neuron
Control centre
Efferent neuron
Effector organ
What can reflexes be used to test
Any abnormalities in sensory pathways (CNS, PNS)
Lesions in reflex arc and level of lesion
Absent reflex and sensory loss- afferent arc of reflex
Absent reflex with paralysis - efferent arc
Describe stretch reflex
Monosynaptic
Most rapid
Simple reflex arc with a single synapse between afferent and efferent neuron
Example- patella reflex. Muscle spindles
Describe flexor withdrawal
Autonomic response, withdrawing a limb from a painful stimulus
Intensity of reflex proportionate to intensity of stimulus
Polysynaptic reflex- uses interneurons
Passes signals from sensory to motor neurons- creating multiple synaptic connections
Describe the process of flexor reflex
-step on stimulus
-fibres send signal to spinal cord
-interneurons branch to different spinal cord segments
-motor figures in several segments are activated
-more than 1 muscle group activated to lift foot off stimulus
Describe babinski reflexes
PLANATR REFLEX- (tool put under foot middle). Curling of toes is healthy in adults
Babinski sign (positive babinski reflex) occurs in absence of descending inhibition. It is normal in infants, but pathological in adults
Name 2 arteries that supply blood to the spinal cord
Anterior and posterior spinal arteries
Why is the circle of Willis circle shaped
Avoid blockages to supply the brain of bloody.
Other ways to allow blood to enter
Function of circle of Willis
Provide blood flow between A and P circulations of the brain
protecting against ischemia in the event of vessel disease or damage in one or more areas.
Name arteries that form circle of Willis
Posterior communicating artery
Anterior cerebral artery
Anterior communicating artery
Posterior cerebral artery
