Spinal Cord Anatomy Flashcards
reflex
- nearly instantaneous, automatic, involuntary motor responses caused by nervous system
- caused by stimuli inside or outside body
- sometimes involve brainstem
brainstem
contains midbrain, pons, medulla
reflex arc
- neural pathway that nerve impulse travels
- if goes thru CNS, that reflex can be used to examine nervous system function
- 5 components (for spinal reflexes)
gray matter
- central part of spinal cord
- contains cell bodies of neurons
- where neurons synapse with other neurons (e.g. interneurons)
white matter
- surrounds gray matter in spinal cord
- contains axons of neurons
dorsal root ganglion (DRG)
contains cell bodies of sensory neurons
dorsal root (of nerve)
- contains axons of sensory neurons
- sensory info goes through here to enter spinal cord
ventral root (of nerve)
- contains axons of motor neurons
- motor info leaves spinal cord through here
anterior horn
- located in gray matter
- contains motor neuron cell bodies
posterior horn
- located in gray matter
- where sensory neurons synapse on interneurons
spinal reflexes
- faster than conscious decision to move from brain
- fewer neurons, impulses have shorter length of travel
receptor
- located at end of sensory neuron
- reacts to stimulus
sensory (afferent) neuron
conducts impulses from receptor via afferent pathway to CNS
integration center
one or more synapses within CNS
motor (efferent) neuron
conducts impulses away from integration center via efferent pathway to effector
effector
responds to efferent impulses by contracting (muscle) or secreting (gland)
stretch reflexes
- protect muscle against an increase in length that may tear/damage muscle fibers
- important for maintaining posture
- ex. = patellar reflex
patellar reflex
- prevents overstretching of quadratis femoris muscle
- tapping patellar tendon (when leg suspended off table) stretches the patellar tendon, which stretches the quadratis femoris attached to it, causing the knee-jerk reflex
flexor withdrawal reflex
- happens when touch something hot (pain receptor in skin generates nerve impulses
- more complicated than stretch reflexes, involves many interneurons (including excitatory and inhibitory interneurons)
muscle spindles
- specialized muscle cells that monitor amount of stretch in a muscle
- when sense stretch, send a signal to the spinal cord via reflex arc
