PSL300 - MOTOR, ANS, & MUSCLE (PART 1)
QUESTIONS WITH COMPLETE SOLUTIONS
Are reflexes innate and genetically determined? Correct
Answers For the most part, yes; many reflexes are innate and
are genetically determined (eg. knee-jerk reflex)
Can every single reflex in the body be completely supresses (if
you no longer want that function anymore)? Correct Answers
Yes
Can reciprocal inhibition be inhibited? Correct Answers Yes;
when co-contraction of antagonists desired (for joint stiffness)
this circuit is suppressed
Can spinal reflex occur independently from the brain? Correct
Answers Yes; however, afferent sensory information,
nevertheless is sent to the brain and input to the spinal cord from
the brain can modulate the spinal reflexes
Compare the speed of the flexion withdrawal reflex to the
stretch reflex and the GTR ... Correct Answers Slow; b/c it goes
through several interneurons in the spinal cord (superficial
dorsal horn) and only uses slow conducting afferents = multi-
synaptic path to motoneurons
Describe sensitivity of the stretch reflex ... Correct Answers
Very sensitive and fast due to muscle spindle afferents, and
monosynaptic connection to motoneurons - even a micron
stretch is sufficient enough to activate it
, Do all of the reflexes share reciprocal inhibition? Correct
Answers Yes (default connection)
Does there have to be a heavy load to activate the stretch reflex?
Correct Answers No
How are reflexes influenced by the brain (CNS)? Correct
Answers Higher CNS control centers in the brain often
modulate the movement by changing the level of output for a
given input of basic reflexes or by turning reflexes on or off -->
this really demonstrates that the corticospinal tract and other
descending tracks manipulate the reflex pathway to determine
which motor pattern will be expressed with a given stimulus
(after Babinski sign slide)
How do reflexes function to carry out a specific task? Correct
Answers They function as a feedback loop to regulate a specific
variable, such as, say, a force of contraction and posture the
limbs, etc.
How do we ensure that the GTR is only activated when
necessary? Correct Answers The threshold for the interneurons
are very carefully set so that this reflex is activated only by
excess activity in the GTO (too much contraction)
Not used for silencing the muscle (turning it off), but rather to
regulate the amount of force
How do we supress reciprocal inhibition? Correct Answers Use
a different set of interneurons in the spinal cord - suppresses the
QUESTIONS WITH COMPLETE SOLUTIONS
Are reflexes innate and genetically determined? Correct
Answers For the most part, yes; many reflexes are innate and
are genetically determined (eg. knee-jerk reflex)
Can every single reflex in the body be completely supresses (if
you no longer want that function anymore)? Correct Answers
Yes
Can reciprocal inhibition be inhibited? Correct Answers Yes;
when co-contraction of antagonists desired (for joint stiffness)
this circuit is suppressed
Can spinal reflex occur independently from the brain? Correct
Answers Yes; however, afferent sensory information,
nevertheless is sent to the brain and input to the spinal cord from
the brain can modulate the spinal reflexes
Compare the speed of the flexion withdrawal reflex to the
stretch reflex and the GTR ... Correct Answers Slow; b/c it goes
through several interneurons in the spinal cord (superficial
dorsal horn) and only uses slow conducting afferents = multi-
synaptic path to motoneurons
Describe sensitivity of the stretch reflex ... Correct Answers
Very sensitive and fast due to muscle spindle afferents, and
monosynaptic connection to motoneurons - even a micron
stretch is sufficient enough to activate it
, Do all of the reflexes share reciprocal inhibition? Correct
Answers Yes (default connection)
Does there have to be a heavy load to activate the stretch reflex?
Correct Answers No
How are reflexes influenced by the brain (CNS)? Correct
Answers Higher CNS control centers in the brain often
modulate the movement by changing the level of output for a
given input of basic reflexes or by turning reflexes on or off -->
this really demonstrates that the corticospinal tract and other
descending tracks manipulate the reflex pathway to determine
which motor pattern will be expressed with a given stimulus
(after Babinski sign slide)
How do reflexes function to carry out a specific task? Correct
Answers They function as a feedback loop to regulate a specific
variable, such as, say, a force of contraction and posture the
limbs, etc.
How do we ensure that the GTR is only activated when
necessary? Correct Answers The threshold for the interneurons
are very carefully set so that this reflex is activated only by
excess activity in the GTO (too much contraction)
Not used for silencing the muscle (turning it off), but rather to
regulate the amount of force
How do we supress reciprocal inhibition? Correct Answers Use
a different set of interneurons in the spinal cord - suppresses the
