Flashcards in Physiology Quiz 4 (Reflex Physiology) Deck (62):
Predictable, stereo typical response to a specific stimulus
Purpose of flexor withdrawal reflex
Protect tissue from damage
Minimize damage when you come into contact with damaging stimuli
Where does the sensory afferent neuron travel to in the flexor withdrawal pathway?
Travels to the spinal cord through the dorsal root ganglia to branch off one way sending sensory info up to the brain, and another way, to synapse upon several interneurons
What is the pathway the signal follows from the afferent neuron to the alpha motor neuron activating the hamstrings of the affected leg? (Flexor withdrawal reflex)
Sensory afferent--> excitatory interneuron--> excitatory interneuron--> alpha motor neuron inner acting hamstrings (contracts hamstrings)
Pathway the signal follows from the sensory afferent neuron to the quads of the affected leg
Sensory afferent--> excitatory interneuron--> inhibitory interneuron--> alpha motor neuron innervating quads (quad does not contract)
Pathway of signal that goes from sensory afferent neuron to quads of unaffected leg (flexor withdrawal reflex)
Sensory afferent--> excitatory interneuron--> excitatory interneuron--> axon crosses to other side of spinal cord--> excitatory interneuron--> alpha motor neuron innervating quads (quads contract)
Pathway of signal that goes from sensory afferent neuron to hamstrings of unaffected leg (flexor withdrawal reflex)
Sensory afferent--> excitatory interneuron--> excitatory interneuron-->crosses to other side of spinal cord--> inhibitory interneuron--> alpha motor neuron innervating hamstrings (hamstrings do not contract)
When one muscle is contracted (hamstrings) the opposite muscle is inhibited (quads). This happens in the flexor withdrawal reflex so that the affected leg is able to bend at the knee and move away from harm.
This process is typical of reflex and voluntary motor activity
Crossed extensor component (of flexor withdrawal reflex)
Opposite leg extending as the affected leg is flexing
What is the value of the flexor withdrawal reflex?
Protect tissue from damage
Support body weight when one leg is flexing due to nociceptive input
What conditions will interfere with the flexor withdrawal reflex?
Neuropathy (happens in diabetes)
Skeletal muscle responds to stretch by contracting (muscle spindles)
Other names for myotatic reflex
Deep tendon reflex
Spinal level reflex
A reflex that occurs at the spinal cord level
Is myotatic reflex a spinal level reflex?
Purpose of myotatic reflex
Keep body upright during postural perturbations (ie, using elevator, uneven terrain)
Where are muscle spindles?
Randomly disbursed in muscles
What is the only monosynaptic reflex in the body?
Are there interneurons in the myotatic reflex?
Where does the 1a afferent nerve go from the muscle spindle?
To spinal cord via dorsal root ganglion
What type of afferent nerve carries info from the muscle spindle to the CNS?
Ability to know where body parts are without looking at them
What tends to happen to gait in people with diabetes/neuropathy and why?
1. Steppage gait
2. Watch feet
Happens because proprioception is compromised
Walking with exaggeration of picking up feet
How does muscle spindle carry proprioceptive info to brain?
1a afferent nerve branches off after the dorsal root ganglion and goes up to the brain
Nerve pathway from muscle spindle to hamstring
1a afferent from spindle--> enters dorsal root ganglion--> inhibitory interneuron--> alpha motor efferent neuron innervating hamstring (inhibits hamstring via reciprocal inhibition)
Gamma motor neuron
Smaller than 1a efferents, myelinated
Referring to muscle spindle itself
Standard muscle cells surrounding spindle
Function of muscle spindle
CNS input about muscle length
Where are contractile filaments located on spindle
At tips of spindle (innervating by gamma motor neurons)
None in middle of spindle
What increases the firing rate of the 1a afferent is coming from the spindle?
center of the spindle is stretching
Activating both alpha and gamma motor neurons during contraction (happens when you do a contraction)
Cerebellum role in muscle contraction/coordination
Makes adjustments in muscle activation based on info from spindles (info about muscle length)
-tested by having a patient hold their arms in front of body with elbows bent, therapist pulls forearms away and patient is instructed to resist, therapist let's go...if patient hits self in chest, indicates problem with cerebellum
Subunits of spindles
Nuclear bag fibers
Nuclear chain fibers
How many subunits of spindle fibers are there?
Nuclear bag fibers AKA
Nuclear chain fibers AKA
What are nuclear bag fibers most effective at measuring?
Muscle length as the muscle length changes
What is nuclear chain fiber most effective at monitoring?
Muscle length when it is unchanging
Can nuclear bag fibers and nuclear chain fibers perform each other's function?
Yup, they are just not as good at it
(Nuclear bag/nuclear chain) fibers have lower viscosity
Nuclear (bag/chain) fibers have higher viscosity
Role of gamma motor fibers in spindles
Contract the filaments at the tips of the spindles in synchrony with the extrafusals
What is activated by higher motor control centers during voluntary and reflex motor activity?
Alpha and gamma motor neuron
What allows the higher motor control centers to monitor muscle length during voluntary and reflex contraction of muscle?
Activation of alpha and gamma motor neurons
Presenting of gamma activity as voluntary motor activity begins
What is gamma bias based on?
Prediction by motor centers as to how rapidly and how much muscle length will change with the activity
How gamma bias works with higher centers
As information comes in informing motor control centers about what is going on, this is compared to the predictions, and if there is a difference, corrections are made as movement proceeds
There is always some level of tone in muscle. What is it maintained by?
Partly maintained by gamma neurons
What does constant level of gamma tone allow for?
Constant flow of info about muscle length
Excessive gamma bias
Abnormally low gamma bias
What happens to gamma activity with neurological injury?
Balance between facilitation and inhibition of gamma activity is upset
Where are Golgi tendon organs found?
In tendons of all skeletal muscles
What des GTO monitor?
What type of afferent nerve carries info from GTO
1b fibers (myelinated, slightly smaller than 1a)
Where are the sensory endings located in the GTO
Intertwined among the collagen fibrils
How does GTO measure tension?
Tension transmitted through collagen fibrils, which stimulates the specialized sensory endings
Golgi tendon organ reflex AKA
Inverse Myotatic reflex
Function of GTO
Thought to be important in protecting tendons from injury...
Fater's opinion: role is to keep higher motor centers informed about the degree of muscle tension developed