Human Neuromovement and Reflexes Quiz

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Questions and Answers

What is the primary effect of spasticity on muscle tone?

It leads to an involuntary increase in muscle tone (correct)

It results in a decrease in muscle responsiveness

It causes complete muscle paralysis

It produces a constant state of relaxation in muscles

How do descending motor commands influence spinal reflexes?

They completely inhibit all spinal reflex activity

They trigger spontaneous reflexes without any regulation

They have no effect on spinal reflexes

They regulate and modify the activity of spinal reflexes (correct)

What results from the removal of descending signals from motor areas of the brain?

Inhibition of all motor functions

Complete control over voluntary movements

Increased relaxation of muscle tone

Over-expression of spinal reflexes (correct)

Which of the following describes the nature of the stretch reflex in individuals experiencing spasticity?

It becomes hyper-reactive and velocity-dependent Signup and view all the answers

What is suggested about the production of movement in relation to spinal reflex circuits?

Spinal reflex circuits can produce most of the movement repertoire Signup and view all the answers

What initiates the withdrawal reflex?

Nociceptor activation Signup and view all the answers

Which of the following correctly describes the crossed extensor reflex?

Excitatory interneurons activate motor neurons of the opposite limb's extensor muscles Signup and view all the answers

How do transcortical stretch reflexes differ from spinal stretch reflexes?

They arrive slower than spinal stretch reflexes Signup and view all the answers

What is the primary role of excitatory interneurons in the withdrawal reflex?

To activate the motor neurons of flexor muscles Signup and view all the answers

In which situation are reflexes likely to be expressed differently?

In an unstable environment requiring adaptive responses Signup and view all the answers

Which of the following describes an automatic postural reaction?

A complex reaction to sudden stimuli that maintains balance Signup and view all the answers

Which statement about voluntary actions is correct?

They are generated by the cerebral cortex responding to internal desires Signup and view all the answers

What is a typical movement impairment seen with reflex abnormalities?

Delayed responses to painful stimuli Signup and view all the answers

What is the dependency of reflex sensitivity related to?

The amount of stretch encountered Signup and view all the answers

How does the level of co-contraction change when responding to postural challenges?

It increases in anticipation of disturbances Signup and view all the answers

What does a preparatory set refer to in the motor system?

The readiness to respond to unpredictability Signup and view all the answers

Which aspect does reflex amplitude NOT depend on?

The individual’s muscle strength Signup and view all the answers

In a complex 3D situation, reflexes are likely to be influenced by which of the following?

The direction of instability created by external factors Signup and view all the answers

What can be concluded about reflexes in relation to spinal and cortical responses?

They can maximize stability even in complex 3D scenarios Signup and view all the answers

Which of the following is NOT a factor influencing reflex modulation?

The individual's age Signup and view all the answers

What was the primary hypothesis tested regarding reflex responses to perturbations?

Reflexes would be altered depending on the orientation of instability Signup and view all the answers

What role do reflexes play in postural stability?

They facilitate rapid adjustments to counteract disruptions Signup and view all the answers

Which strategy is primarily used for small perturbations on a firm surface?

Ankle strategy Signup and view all the answers

What characterizes anticipatory postural adjustments (APAs) in response to self-movement?

Early activation of postural muscles Signup and view all the answers

Which of the following statements about automatic reactions is FALSE?

They involve fewer muscles than reflex responses. Signup and view all the answers

What mechanism likely generates reactive postural control strategies?

Brainstem processes Signup and view all the answers

What is a characteristic of transcortical reflexes compared to spinal reflexes?

They can be flexibly tuned. Signup and view all the answers

What role does the cortex play in reflex inhibition during voluntary actions?

It reduces the size of stretch reflexes. Signup and view all the answers

Which postural strategy is most suited for correcting posture during large or faster perturbations?

Stepping strategy Signup and view all the answers

How do automatic reactions differ from reflexes?

Reflexes are always faster than automatic reactions. Signup and view all the answers

Which of the following statements about the stability provided by co-contraction is TRUE?

Co-contraction enhances stability during specific movements. Signup and view all the answers

What is a potential benefit of anticipatory postural adjustments?

Facilitation of independent limb movement during perturbations Signup and view all the answers

What is suggested to reflect increases in neural activity for task-specific preparations?

Increased excitability of task-relevant circuits Signup and view all the answers

What role does preparatory set potentially play in reflex modulation?

Modification of reflexes to be more task-specific Signup and view all the answers

How did TMS affect long latency stretch reflexes in unstable situations?

They were significantly reduced Signup and view all the answers

What does the increase in co-contraction signify in relation to environmental stability?

It increases as stability is challenged Signup and view all the answers

What theory was posited regarding motor cortex inhibition's effect on StartReact responses?

It influences low-latency reflexes but not StartReact responses Signup and view all the answers

What was the primary method used in the study on co-contraction and balance?

Participants seated with feet attached to a motor Signup and view all the answers

How did stretch reflex sensitivity behave in unstable conditions according to the study?

Sensitivity decreased Signup and view all the answers

What conclusion was drawn regarding reflexes in the upper limbs compared to ankles?

Upper limb reflexes have a larger role in stability adjustments Signup and view all the answers

What impact does the preparatory set have on both cortical and subcortical responses?

It can enhance both reflex modalities Signup and view all the answers

What relationship exists between intrinsic stability in ankles and voluntary mechanisms?

They are dependent upon voluntary mechanisms Signup and view all the answers

Study Notes

Reflexes and Human Neuromovement

Reflexes are automatic responses to stimuli that allow for quick reactions to potential threats or changes in the environment.
Withdrawal reflex: triggered by pain receptors (nociceptors), causes the immediate withdrawal of a limb from a painful stimulus.
Crossed extensor reflex: occurs simultaneously with the withdrawal reflex; extends the limb opposite to the one experiencing pain to maintain balance.
Transcortical stretch reflexes: occur when signals from stretch receptors in a muscle are transmitted to the sensorimotor cortex, resulting in a motor response that arrives slightly later than the spinal stretch reflex.
Preparatory set: the “readiness” of the motor system to generate a desired action or response; influences reflex modulation and subcortical responses.
Reflex sensitivity: can be modified based on the amount of stretch encountered and the ability of the muscle to counteract limb disturbances.
Automatic postural reactions: complex patterns of muscle activity that occur too late for reflexes, thought to be coordinated in the brainstem.
Anticipatory Postural Adjustments (APAs): feed-forward motor control mechanisms that help maintain balance by anticipating disturbances.
Muscle synergies: a group of muscles activated in synchrony with fixed relative gains, could potentially simplify the degrees of freedom problem in body movement.

Reflex Abnormalities

Spasticity: an involuntary increase in muscle tone that leads to resistance against normal movements and potentially pain, often resulting from reduced descending control from motor areas.
Reflexes are not static: they are dynamically regulated by the brain, and disruptions in these pathways can lead to movement impairments, such as spasticity.

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Description

Test your knowledge on the various types of reflexes involved in human neuromovement. This quiz covers automatic responses like the withdrawal reflex and crossed extensor reflex, and explores concepts such as reflex sensitivity and preparatory set. Enhance your understanding of how the nervous system interacts with muscle responses.