PSL300 - CNS
Motor/Autonomic/Learning Exam
Questions and Questions and Answers
Graded A+
Simple reflexes - Correct answer-- Simplest form of motor control, governed by
spinal cord
- Sensory neurons synapse to spinal cord and spinal cord motor neurons to mediate
innate reflexes
- Usually a feedback loop to regulate force, hold position/posture
Central pattern generators (CPGs) - Correct answer-- Functional networks of
interneurons that mediate centrally coordinated posture and movement
- Located in spinal cord and brain stem
- Activated one-by-one in order of relevance
- Help coordinate many motor groups involved in rhythmic motions
- Important for locomotion & motor control
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,- Help restore posture & balance after perturbation
- Important in behavioural responses
Complex/volitional movement - Correct answer-Motor output planned and refined
by the motor cortex, basal ganglia and cerebellum. These are learned and evolved
movements that are removed form postural support in order to perform skills.
Interneurons - Correct answer-Central nervous system neurons that internally
communicate and intervene between the sensory inputs and motor outputs
Reflex loop - Correct answer-- A simple connection from a sensory cell to the
spinal cord and back to a muscle; produces motor response without involvement of
brain
- Stimulus => specific receptor => sensory (afferent) neuron => spinal cord (CNS)
=> efferent neuron => target cell (in skeletal muscle) => response
Monosynaptic reflex - Correct answer-A reflex loop where each sensory neuron is
directly connect by a single synapse in the spinal cord to the efferent neuron.
Polysynaptic reflex - Correct answer-A reflex loop where each sensory neuron is
synapsed to at least one interneuron in the spinal cord before synapsing to the
efferent neuron (i.e. multiple synapses).
Stretch reflex - Correct answer-*Stretch muscle, it contracts*
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,- Stimulus: passive stretch of muscle (e.g. applied load)
- Response: active contraction of muscle (same one that was stretched)
- Properties: subconscious, sensitive, fast
- Function: stabilize posture
- Muscles: extensor muscles, reflex strongest in postural muscles (for holding up
against gravity), delay for extensors farther from spinal cord
- Pathway: monosynaptic through spinal cord
- Sensed by: proprioceptors in muscle spindle which are connected directly to
motoneurons
- Suppressed during movement
Stretch reflex mechanism - Correct answer-Load => muscle stretch => activate
muscle spindle => activate motoneuron in spinal cord => efferent signal => same
muscle contracts
Golgi tendon reflex - Correct answer-*Contract muscle, it relaxes*
- Stimulus: active tension in muscle -- only if excess activity or excess load of
GTO
- Response: relaxation or reduction of tension in same muscle
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, - Properties: negative feedback, slightly slower than stretch reflex but still very
fast, subconcious
- Function: regulate level of activity to prevent over-stretching and protect muscle
- Muscle: same as stretch
- Pathway: polysynaptic through spinal cord
- Sensed by: GTO (Golgi Tendon Organ) which contains muscle spindles
- Suppressed when net motion is desired
Golgi tendon reflex mechanism - Correct answer-Excessive load => activate GTO
(Ib) => activate Ib interneurons in intermediate zone => inhibit α-motoneurons of
same muscle => relax muscle/reduce contraction
Stretch and Golgi Tendon Reflexes - Correct answer-- Work together to maintain
posture
- E.g. when a muscle is overextended, can either activate the stretch reflex of the
antagonistic muscle or activate the GT reflex of the overstretched muscle to inhibit
interneurons synapsing to the α-motoneurons of that same muscle
Ia afferent - Correct answer-- Monosynaptic path
- Stretch reflex
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Motor/Autonomic/Learning Exam
Questions and Questions and Answers
Graded A+
Simple reflexes - Correct answer-- Simplest form of motor control, governed by
spinal cord
- Sensory neurons synapse to spinal cord and spinal cord motor neurons to mediate
innate reflexes
- Usually a feedback loop to regulate force, hold position/posture
Central pattern generators (CPGs) - Correct answer-- Functional networks of
interneurons that mediate centrally coordinated posture and movement
- Located in spinal cord and brain stem
- Activated one-by-one in order of relevance
- Help coordinate many motor groups involved in rhythmic motions
- Important for locomotion & motor control
©COPYRIGHT 2025, ALL RIGHTS RESERVED 1
,- Help restore posture & balance after perturbation
- Important in behavioural responses
Complex/volitional movement - Correct answer-Motor output planned and refined
by the motor cortex, basal ganglia and cerebellum. These are learned and evolved
movements that are removed form postural support in order to perform skills.
Interneurons - Correct answer-Central nervous system neurons that internally
communicate and intervene between the sensory inputs and motor outputs
Reflex loop - Correct answer-- A simple connection from a sensory cell to the
spinal cord and back to a muscle; produces motor response without involvement of
brain
- Stimulus => specific receptor => sensory (afferent) neuron => spinal cord (CNS)
=> efferent neuron => target cell (in skeletal muscle) => response
Monosynaptic reflex - Correct answer-A reflex loop where each sensory neuron is
directly connect by a single synapse in the spinal cord to the efferent neuron.
Polysynaptic reflex - Correct answer-A reflex loop where each sensory neuron is
synapsed to at least one interneuron in the spinal cord before synapsing to the
efferent neuron (i.e. multiple synapses).
Stretch reflex - Correct answer-*Stretch muscle, it contracts*
©COPYRIGHT 2025, ALL RIGHTS RESERVED 2
,- Stimulus: passive stretch of muscle (e.g. applied load)
- Response: active contraction of muscle (same one that was stretched)
- Properties: subconscious, sensitive, fast
- Function: stabilize posture
- Muscles: extensor muscles, reflex strongest in postural muscles (for holding up
against gravity), delay for extensors farther from spinal cord
- Pathway: monosynaptic through spinal cord
- Sensed by: proprioceptors in muscle spindle which are connected directly to
motoneurons
- Suppressed during movement
Stretch reflex mechanism - Correct answer-Load => muscle stretch => activate
muscle spindle => activate motoneuron in spinal cord => efferent signal => same
muscle contracts
Golgi tendon reflex - Correct answer-*Contract muscle, it relaxes*
- Stimulus: active tension in muscle -- only if excess activity or excess load of
GTO
- Response: relaxation or reduction of tension in same muscle
©COPYRIGHT 2025, ALL RIGHTS RESERVED 3
, - Properties: negative feedback, slightly slower than stretch reflex but still very
fast, subconcious
- Function: regulate level of activity to prevent over-stretching and protect muscle
- Muscle: same as stretch
- Pathway: polysynaptic through spinal cord
- Sensed by: GTO (Golgi Tendon Organ) which contains muscle spindles
- Suppressed when net motion is desired
Golgi tendon reflex mechanism - Correct answer-Excessive load => activate GTO
(Ib) => activate Ib interneurons in intermediate zone => inhibit α-motoneurons of
same muscle => relax muscle/reduce contraction
Stretch and Golgi Tendon Reflexes - Correct answer-- Work together to maintain
posture
- E.g. when a muscle is overextended, can either activate the stretch reflex of the
antagonistic muscle or activate the GT reflex of the overstretched muscle to inhibit
interneurons synapsing to the α-motoneurons of that same muscle
Ia afferent - Correct answer-- Monosynaptic path
- Stretch reflex
©COPYRIGHT 2025, ALL RIGHTS RESERVED 4
