Spinal Cord Flashcards
Spinal cord function
Sends and receives signals between brain and rest of the body
Structure of the spinal cord
Inner core of grey matter
H-shaped pillar with anterior and posterior grey columns
Contains a small central canal
Surrounded by an outer covering of white matter
Divided into anterior, lateral and posterior white columns
Gray matter
The amount of gray matter present is related to the amount of muscle innervated at that level
Largest at cervical and lumbosacral region
Consists of a mixture of nerve cells, neuroglia and blood vessels
Enlargements
Cervical enlargement - 4th cervical to 2nd thoracic segment
Lumbo-sacral enlargement - 2nd lumbar to 3rd sacral segment
Describe the arrangement of spinal nerves
31 pairs of spinal nerves (8 cervical, 12 thoracic, 5 lumbar, 5 sacral, 1 coccygeal)
Attached by anterior/ventral (motor roots) and posterior/dorsal (sensory roots)
Each posterior nerve root processes a posterior root ganglion
Ganglia
Clusters of nerve cell bodies that carry nerve signals to and from the CNS
Sensory ganglia
Ovoid shape with an oval cell body
Motor ganglia
Long chain in the spine from base of the skull to the tail, contain irregular shaped cell bodies
Cauda equina
The collection of nerves at the end of the spinal cord
Paraplegic (paralysis of the legs) - levels & symptoms
Thoracic, lumbar or sacral level
Limited mobility
Chronic pain
Reduced bowel & bladder function
Loss of sexual function
Loss of muscle tone in legs
Weight gain
Quadriplegic - paralysis in all four limbs
Cervical level
Limited or complete absence of arm and hand function
Problems speaking, swallowing or breathing without assistance
Difficulty performing daily tasks, dressing and eating
Loss of muscle tone
Loss of bone density
Levels of spinal cord injury
A - Complete injury
B - Sensory incomplete
C - Motor incomplete
D - Muscle function below level of injury
E - Normal
PNS
Peripheral nerves are cranial and spinal nerves
Consists of parallel bundles of fibres that may be efferent or afferent axons
Surrounded by connective tissue sheaths
Types of receptors
Skeletal muscle propioreceptors
Skin mechanoreceptors
Nociceptors thermoreceptors
Role of Schwann cells
Produce myelin in PNS
Describe a simple reflex arc
- Stimulus
- Receptor
- Sensory neuron
- CNS
- Motor neuron
- Effector
- Response
Importance of reflexes
Safeguard our bodies from injury caused by unexpected external and internal stimuli
Stretch reflex
Monosynaptic
Most rapid
Simple reflex arc with a single synapse between the afferent and efferent neuron
Eg: patella reflex - muscle spindles
What are muscle spindles
Muscle spindles are stretch detectors
They sense how much and how fast a muscle is lengthened or shortened
Flexor withdrawal
Automatic response, withdrawing a limb from a painful stimulus
Intensity of reflex proportionate to intensity of stimulus
Polysynaptic reflex – uses interneurons
Cross extensor reflex
Flexor contracts and extensor relaxes to withdraw foot
Extensor contracts and flexor relaxes in opposite leg to support weight
Babinski reflexes
The plantar reflex (negative result) curling of the toes, is seen in healthy adults
The Babinski signs (positive result) occurs in the absence of curling toes. Normal in infants but pathological in adults
Myotomes
C5 - shoulder abduction & external rotation, elbow flexion
C6 - wrist extension
C7 - elbow extension & wrist flexion
C8 - thumb extension & finger flexion
T1 - finger abduction
L1/L2 - hip flexion
L3 - knee extension
L4/L5 - ankle dorsiflexion
L5 - great toe extension
S1 - ankle plantar flexion
S4 - bladder & rectum motor supply
