Flashcards in Stretch/Spinal Reflexes Deck (11):
1
3 Characteristics of Reflexes
Rapid
Involuntary
Stereotypic
2
Nuclear Bag vs. Chain Fibers
Nuclei clumped together in middle vs. spread out along fiber
3
Group IA vs. II Fibers
Wrap around middle (usually bag) vs. around whole thing (usually chain)
Phasic, report change of length vs. tonic, report length
4
Myotatic (Tendon Tap Reflex)
Stretch in muscle, IA fibers from MSO depol, send through DRG to synapse in spinal cord to alpha neuron to stimulate contraction of that muscle. Primary afferent fibers attached to MSO also form weaker synapses w/ synergistic muscles and excite inhibitory interneurons to antagonist muscles
5
Gamma Motor Neurons
Located next to alphas in spinal cord, cause muscle spindle to contract w/ muscle to keep sensory part at same length
6
Normal Muscle Tone
Determined by resting output of gamma motor neurons
7
Gamma Loop/Alpha-Gamma coactivation
Descending inputs control gamma motor firing to bring to intended length, meaning MSO fires until muscle reaches that length. Afferents keep activating alpha motor neurons until there
8
Golgi tendon organs
In series w/ fibers in tendons, only responds to muscle contraction. 1b fibers send info back and inhibit homonymous/synergist muscles and activate antagonist muscle to prevent overcontraction and damaging. Not stretched from passive stretch, that's absorbed by muscle fibers
9
Joint Receptors
Actually in ligaments and capsules and provide proprioceptive information, and cobine w/ signals from MSO, Golgi tendon organs, and skin Rs
10
Withdrawal Reflex
Painful stimulus travels up nociceptor afferent (III, C, or Adelta), and synapses in spinal cord to activate flexor, inhibit extensor, and do opposite on contralateral side to shift weight (if applicable)
11