CNS Class 7 - Reflexes & Intro to Spasticity

Question 1

The set of neurons involved in enacting the reflex response.

Answer 1

Reflex Arc

Question 2

What are the 3 neurons involved in the basic spinal cord type of reflex?

Answer 2

1) Afferent Neuron
2) Interneuron
3) Efferent Neuron

Question 3

The ________ neuron, which is a first order neuron in the sensory system, communicates from the tissue and enters the CNS at the ______ horn.

Answer 3

Afferent
Dorsal

Question 4

T/F - Afferent neurons are always excitatory because they are transmitting tissue information up the afferent pathway.

Answer 4

True

Question 5

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.

Answer 5

Efferent
Ventral

Question 6

Some examples of ______ ____ include the withdrawal reflex, GTO reflex and joint protective reflexes.

Answer 6

Reflex Arcs

Question 7

One major exception is the _______ reflex, which is ____________, meaning it has only two neurons in its reflex arc.

Answer 7

Stretch
Monosynaptic

Question 8

A reflex arc that protects the muscle belly from an overstretch injury. Composed of a 1a sensory neuron and an alpha motor neuron.

Answer 8

Stretch (aka. Myotatic, Deep Tendon) Reflex

Question 9

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.”

Answer 9

Stretch (aka. Myotatic, Deep Tendon) Reflex

Question 10

Which neurotransmitter is being released at the 1a → α synapse that causes excitation?

Answer 10

Acetylcholine

Question 11

T/F - The stretch reflex is protective and requires activation from the CNS.

Answer 11

False - The stretch reflex is protective and DOES NOT require activation from the CNS.

Question 12

A reflex arch that protects the tendon from overstretch injury. Composed of a 1b sensory neuron, an interneuron and an alpha motor neuron.

Answer 12

GTO Reflex

Question 13

T/F - 1b is excitatory and the GTO reflex response needs to increase stress on the tendon, requiring excitation of α.

Answer 13

False - 1b is excitatory, BUT the GTO reflex response needs to REDUCE stress on the tendon, requiring INHIBITION of α.

Question 14

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.”

Answer 14

GTO Reflex

Question 15

1b releases acetylcholine toward the interneuron to activate it. The interneuron then releases ______, which is an inhibitory neurotransmitter, toward α.

Answer 15

GABA

Question 16

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.

Answer 16

Reciprocal Inhibition
Relaxation

Question 17

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.

Answer 17

True

Question 18

T/F - 1a and 1b sensory neurons synapse with different α motor neurons.

Answer 18

False - 1a and 1b sensory neurons synapse with the SAME α motor neuron.

Question 19

The stretch reflex and GTO reflex have a ___________ relationship and their relationship plays a major role in maintaining muscle tone within normal parameters.

Answer 19

Homeostatic

Question 20

Since there is no ___________ in the stretch reflex, instead it has an elaborate receptor structure called the _______.

Answer 20

Interneuron
Spindle

Question 21

1a wraps around the central, ___-___________ portion of the structure inside the spindle, increasing firing as it _________ and reducing firing afterwards.

Answer 21

Non-Contractile
Elongates

Question 22

__________ muscle fibres will add to the stretch detected by 1a if they _______, or reduce the stretch detected by 1a if they are _______.

Answer 22

Intrafusal
Shorten
Relaxed

Question 23

T/F - Extrafusal fibres can be used to preset 1a sensitivity to stretch occurring to the muscle belly fibres outside the spindle.

Answer 23

False - INTRAFUSAL fibres can be used to preset 1a sensitivity to stretch occurring to the muscle belly fibres outside the spindle.

Question 24

_____ motor neurons are the efferent neurons that innervate the intrafusal fibres. Their cell bodies are found in the ventral horn.

Answer 24

Gamma

Question 25

T/F - Gamma motor neurons are acted on directly by the HMCs, which act to influence the stretch reflex.

Answer 25

True

Question 26

What are the 2 pathways that the HMCs can influence activation of alpha motor neurons in the spinal cord?

Answer 26

1) Pyramidal
2) Extrapyramidal

Question 27

The _________ pathway involves direct excitation transmission and nuanced direct __________ of alpha, making it less responsive to incoming tissue afferentation.

Answer 27

Pyramidal
Inhibtion

Question 28

The ______________ pathway influences receptor and interneuron ______________ in reflex arcs.

Answer 28

Extrapyramidal
Responsiveness

Question 29

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.

Answer 29

Spasticity

Question 30

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.

Answer 30

Spasticity
Upper

Question 31

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.

Answer 31

Projection

Question 32

T/F - Spasticity occurs as a result of damage to one HMC.

Answer 32

False - Spasticity DOES NOT occur as a result of damage to one HMC.

Question 33

Spasticity results when integrated HMC transmission is ___________ somewhere as it makes its way through the brain and down the _________ pathways.

Answer 33

Interrupted
Pyramidal

Question 34

T/F - Spasticity typically results from grey matter lesions in the brain, brainstem or spinal cord.

Answer 34

False - Spasticity typically results from WHITE matter lesions in the brain, brainstem or spinal cord.

Question 35

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.”

Answer 35

Stroke Pattern

Question 36

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.”

Answer 36

Multiple Sclerosis Pattern

Question 37

T/F - Traumatic brain injuries can occur in numerous presentations.

Answer 37

True

Question 38

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.

Answer 38

Autonomous
Coordinate

Question 39

T/F - When it comes to spasticity, HMC input is predominantly inhibiting.

Answer 39

True

Question 40

Rigidity is typically seen in ______________ lesions, such as the basal ganglia, rubrospinal or vestibulospinal tracts.

Answer 40

Extrapyramidal

Question 41

Spasticity generally only occurs during muscle _______ and not at rest. It is usually accompanied by increased tendon reflexes and a __________ response.

Answer 41

Stretch
Babinski’s

Question 42

T/F - With rigidity, muscle tone is decreased at rest, but is usually present during PROM.

Answer 42

False - With rigidity, muscle tone is INCREASED EVEN at rest, AND is usually present during PROM.

Question 43

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.

Answer 43

Spasticity
Rigidity

Question 44

A type of spasticity where there is more tone in the initial part of movement.

Answer 44

Clasp Knife Spasticity

Question 45

________ 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.

Answer 45

Rigidity
Spasticity