Spinal Cord Flashcards
spinal cord anatomy
18 inches long, 1/2 inch wide
ends between L1 and L2, doesn’t go all the way down back
bilateral symmetry
grooves that divide spinal cord into L and R, the posterior median sulcus and the anterior median fissure
enlargements of spinal cord
caused by amount of gray matter in segment
involvement with sensory and motor nerves of limbs
Cervical enlargement of spinal cord
nerves of shoulders and upper limbs
Lumbar enlargement of spinal cord
nerves of pelvis and lower limbs
gray matter areas in lumbar are bigger
more interpretative and sensory/motor tracts to filter information
two branches of spinal nerves
ventral root - contains axons of motor neurons
Dorsal root - contains axons of sensory neurons
spinal nerves are always what kind of nerve?
mixed nerves
Dorsal root ganglia
contain cell bodies of sensory neurons
white matter of spinal cord superficial and doesn’t need to be
myelinated, but some are
gray matter of spinal cord
surrounds central canal of spinal cord
contains neuron cell bodies, neuroglia, unmyelinated axons
has gray horns - “projections”
posterior and anterior and lateral gray horns
posterior contain somatic and visceral sensory nuclei
anterior gray horns contain somatic motor nuclei
lateral gray horns are in thoracic and lumbar segments; contain visceral motor nuclei ***only in thoracic and lumbar, innervating viscera…
gray commissures
axons that cross over 1:18:00 go there
posterior columns, anterior columns, and lateral white columns
listen to 1:18:00
4 major nerve plexus’
cervial, brachial, lumbar, sacral
what’s a reflex arc?
- The wiring of a single reflex
- Beginning at receptor
- Ending at peripheral effector
- Generally opposes original stimulus (negative
feedback)
5 steps in a neural reflex
– Step 1: Arrival of stimulus, activation of receptor
* Physical or chemical changes
– Step 2: Activation of sensory neuron
* Graded depolarization
– Step 3: Information processing by postsynaptic cell
* Triggered by neurotransmitters
– Step 4: Activation of motor neuron
* Action potential
– Step 5: Response of peripheral effector
triggered by neurotransmitters
classifying nerve reflexes - 4 categories
- By early development
- By type of motor response
- By complexity of neural circuit
- By site of information processing
Innate reflexes
Basic reflexes and formed BEFORE birth!
other type is “acquired”
Stretch or deep tendon reflexes (e.g., patellar, or “knee-
jerk,” reflex) is an example of what type of reflex?
somatic reflex - involuntary control of nervous system
reflexes that control systems other than muscular system
visceral reflexes or “autonomic reflexes”
what’s a Monosynaptic reflex
Sensory neuron synapses directly onto motor neuron
what’s a polysynaptic reflex?
At least one interneuron between sensory neuron and
motor neuron
Intersegmental reflex arcs produce…
a highly variable motor response - many segments react
this reflex produce either EPSPs or IPSPs
polysynaptic reflex
