Spinal Reflexes
Works via Ia afferents from spindle providing information on changes in length. Inhibits antagonistic muscle to allow movement to occur.
What is the stretch reflex?
Time during which a nerve is refractory to a second stimulus.
Absolute refractory period.
Has an additive effect on end plate potentials until threshold is reached and AP is generated
WHat is ACh?
The group of motoneurons that innervate a single muscle.
What is a motoneuron pool?
Present throughout muscle and signal vibration.
What are Pacinian corpuscles?
Can be triggered by group II, III or IV fibers. Afferents of this can produce crossed extension to stabilize the weight and maintain balance and equilibrium.
What is the flexor withdrawal reflex?
Principle that an AP does not vary from minimum to maximum. Once it reaches threshold it is this.
What is all or none principle?
They are bidirectional, allowing ions to move back and forth, and are faster than their counter-partner.
What are Electrical synapses?
They provide the force of a muscle contraction, stimulated by alpha motor neurons.
What are extrafusal fibers?
Increase in resistance to passive movement, occurring with an increase in sensitivity of spindles.
What is hypertonia?
Doesn't synapse directly on the homonymous motor pool. Highly exemplified in those with a spastic limb. Uses Ib fibers.
What is the inverse myotatic reflex?
Triggered by a delayed increase in conductance of K followed by its gradual return to resting states.
What is repolarization?
Keep concentration of ACh high, so that receptors can open longer and produce larger endplate potentials to activate muscles and cause contractions.
What are cholinesterase inhibitors?
Have a single row of nuclei. Shorter and thinner than their counterpart. Group II fibers tend to form on these.
What are nuclear chain fibers?
The population of larger motoneurons that require stronger stimuli to get them in the excited state.
What is Subliminal fringe?
Overlapping discharge zones of 2 afferents cause the summation to be less than the sum of motoneurons excited independently.
What is occlusion?
AP occurs only at these in myelinated axons because this is the location of regenerative Na and K channels.
Activates nicotinic AChR at the NMJ non-competitively; degraded by a circulating butyrylcholinesterase which acts in a slow manner.
What is Succinylcholine?
They respond to noxious stimuli and are innervate by group III or IV-C fibers.
What are free nerve endings?
Flank the VC bilaterally; also found in the body wall, thoracic cavity and head and limbs.
What are sympathetic chain ganglia?
The result of persistent neural activity between polysynaptic circuits and neuronal pools located at the level of the spinal cord. Caused by the presence of parallel, reverberating circuits.
What is after discharge?
An AP can occur on a nerve only if this is open.
What is inactivation gate?
Increasing conductance of K or gcl will hyperpolarize the cell causing this.
What is an IPSP?
Are small and encapsulated in sheaths of CT, running parallel to their counterpart, but not running the entire length of the muscle. Fine muscles have a larger number of these.
What are intrafusal fibers?
Their stimulation increases intracellular cAMP levels, triggering metabolic changes in the target cell.
What are Beta receptors?