CNS Class 7 - Reflexes & Intro to Spasticity Flashcards
The set of neurons involved in enacting the reflex response.
Reflex Arc
What are the 3 neurons involved in the basic spinal cord type of reflex?
1) Afferent Neuron
2) Interneuron
3) Efferent Neuron
The ________ neuron, which is a first order neuron in the sensory system, communicates from the tissue and enters the CNS at the ______ horn.
Afferent
Dorsal
T/F - Afferent neurons are always excitatory because they are transmitting tissue information up the afferent pathway.
True
The ________ neuron, which is an alpha neuron, has its cell body in the _______ horn and its axon in the PNS. Its role is to innervate its motor unit.
Efferent
Ventral
Some examples of ______ ____ include the withdrawal reflex, GTO reflex and joint protective reflexes.
Reflex Arcs
One major exception is the _______ reflex, which is ____________, meaning it has only two neurons in its reflex arc.
Stretch
Monosynaptic
A reflex arc that protects the muscle belly from an overstretch injury. Composed of a 1a sensory neuron and an alpha motor neuron.
Stretch (aka. Myotatic, Deep Tendon) Reflex
Which reflex arc is being described below?
“ 1a increases firing as the muscle belly elongates, especially so if the stretch happens quickly and/or is nearing end range. 1a synapses directly with α, so as its firing escalates it increases excitation chemistry in the synapse, causing increased α activation. The muscle tightens to counteract the stretch.”
Stretch (aka. Myotatic, Deep Tendon) Reflex
Which neurotransmitter is being released at the 1a → α synapse that causes excitation?
Acetylcholine
T/F - The stretch reflex is protective and requires activation from the CNS.
False - The stretch reflex is protective and DOES NOT require activation from the CNS.
A reflex arch that protects the tendon from overstretch injury. Composed of a 1b sensory neuron, an interneuron and an alpha motor neuron.
GTO Reflex
T/F - 1b is excitatory and the GTO reflex response needs to increase stress on the tendon, requiring excitation of α.
False - 1b is excitatory, BUT the GTO reflex response needs to REDUCE stress on the tendon, requiring INHIBITION of α.
Which reflex arc is being described below?
“1b increases firing as the tendon elongates, especially so if the stretch happens quickly and/or is nearing end range. 1b synapses with the interneuron, which releases an inhibitory neurotransmitter into its synapse with α, causing a decreased α activation. The muscle relaxes to reduce pull on the tendon.”
GTO Reflex
1b releases acetylcholine toward the interneuron to activate it. The interneuron then releases ______, which is an inhibitory neurotransmitter, toward α.
GABA
1a also synapses with an interneuron for the __________ __________ reflex. The interneuron is inhibitory and synapses with an α for the opposing muscle. It activates a __________ response when its partner muscle is activated by a stretch reflex.
Reciprocal Inhibition
Relaxation
T/F - The reciprocal inhibition reflex can be inhibited by the HMCs if the circumstance dictates an eccentric contraction is more suitable than relaxation of the muscle.
True
T/F - 1a and 1b sensory neurons synapse with different α motor neurons.
False - 1a and 1b sensory neurons synapse with the SAME α motor neuron.
The stretch reflex and GTO reflex have a ___________ relationship and their relationship plays a major role in maintaining muscle tone within normal parameters.
Homeostatic
Since there is no ___________ in the stretch reflex, instead it has an elaborate receptor structure called the _______.
Interneuron
Spindle
1a wraps around the central, ___-___________ portion of the structure inside the spindle, increasing firing as it _________ and reducing firing afterwards.
Non-Contractile
Elongates
__________ muscle fibres will add to the stretch detected by 1a if they _______, or reduce the stretch detected by 1a if they are _______.
Intrafusal
Shorten
Relaxed
T/F - Extrafusal fibres can be used to preset 1a sensitivity to stretch occurring to the muscle belly fibres outside the spindle.
False - INTRAFUSAL fibres can be used to preset 1a sensitivity to stretch occurring to the muscle belly fibres outside the spindle.
_____ motor neurons are the efferent neurons that innervate the intrafusal fibres. Their cell bodies are found in the ventral horn.
Gamma
T/F - Gamma motor neurons are acted on directly by the HMCs, which act to influence the stretch reflex.
True
What are the 2 pathways that the HMCs can influence activation of alpha motor neurons in the spinal cord?
1) Pyramidal
2) Extrapyramidal
The _________ pathway involves direct excitation transmission and nuanced direct __________ of alpha, making it less responsive to incoming tissue afferentation.
Pyramidal
Inhibtion
The ______________ pathway influences receptor and interneuron ______________ in reflex arcs.
Extrapyramidal
Responsiveness
Muscle hypertonia as a result of exaggerated, disregulated reflex responses, which are in turn the result of an imbalance between excitation and inhibition in the CNS regulation of reflex sensitivity and motor activities, including reflexes.
Spasticity
The ability of the HMCs to exert their complex balancing act of excitation and inhibition ensures that perfect performance of an action. This compromised with __________ due to some type of _____ motor neuron injury or disease-caused damage.
Spasticity
Upper
With spasticity, the damage occurs in the __________ fibres of the brain, brainstem or spinal cord. The location of it influences the severity and presentation of spasticity.
Projection
T/F - Spasticity occurs as a result of damage to one HMC.
False - Spasticity DOES NOT occur as a result of damage to one HMC.
Spasticity results when integrated HMC transmission is ___________ somewhere as it makes its way through the brain and down the _________ pathways.
Interrupted
Pyramidal
T/F - Spasticity typically results from grey matter lesions in the brain, brainstem or spinal cord.
False - Spasticity typically results from WHITE matter lesions in the brain, brainstem or spinal cord.
Which damage pattern in the brain is being described below?
“An infarction causes fatal axonal injuries to a group of neurons supplied by the affected artery. Retrograde degeneration produces loss of those axons and this interrupts the capacity of any integrated efferent transmission to both the alpha and gamma neurons in the pathway(s) of the lost upper motor neurons, as well as transmission that modulates the companion reflexes.”
Stroke Pattern
Which damage pattern in the brain is being described below?
“Accumulation of a large number of plaques throughout the upper motor neurons. Even though each one is small, over time it adds up to disconnecting transmission from reaching the anterior horn cells in an effective way.”
Multiple Sclerosis Pattern
T/F - Traumatic brain injuries can occur in numerous presentations.
True
Keep in mind that reflexes are __________, meaning they do not require CNS involvement to perform their basic response. The input of the HMCs is to modulate, regulate, __________ and integrate their natural responses into performance of smooth, purposeful and efficient activities.
Autonomous
Coordinate
T/F - When it comes to spasticity, HMC input is predominantly inhibiting.
True
Rigidity is typically seen in ______________ lesions, such as the basal ganglia, rubrospinal or vestibulospinal tracts.
Extrapyramidal
Spasticity generally only occurs during muscle _______ and not at rest. It is usually accompanied by increased tendon reflexes and a __________ response.
Stretch
Babinski’s
T/F - With rigidity, muscle tone is decreased at rest, but is usually present during PROM.
False - With rigidity, muscle tone is INCREASED EVEN at rest, AND is usually present during PROM.
There is more resistance in one direction than the other with __________, but the same resistance in all directions for ________ because it affects all muscles surrounding a particular joint equally.
Spasticity
Rigidity
A type of spasticity where there is more tone in the initial part of movement.
Clasp Knife Spasticity
________ is not velocity dependent, as it does not vary with speed of movement of muscle groups involved. __________ is velocity dependent meaning that more rapid movement triggers a stronger involuntary contraction or “catch” of the affected muscles.
Rigidity
Spasticity
