Lecture 3- Reflexes, Spinal Cord & Spinal Tracts

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Questions and Answers

A lesion in the medulla oblongata disrupts the cuneate fasciculus. What sensory deficit would most likely result from this injury?

Impaired fine touch and proprioception on the ipsilateral side of the body. (correct)
Loss of motor control in the ipsilateral limbs.
Impaired balance and coordination.
Loss of pain and temperature sensation on the contralateral side of the body.

A patient exhibits an inability to maintain balance and keep their head upright. Which descending tract is most likely affected?

Tectospinal Tract
Lateral Corticospinal Tract
Reticulospinal Tract
Vestibulospinal Tract (correct)

Damage to the anterior spinocerebellar tract would most likely result in deficits related to which function?

Pain and temperature sensation from the trunk.
Unconscious proprioception from the lower limbs. (correct)
Motor commands to distal muscles.
Conscious perception of fine touch.

A patient has lost the ability to feel pain and temperature on the left side of their body. Where is the most likely location of the lesion?

Right spinal cord affecting the spinothalamic tract (A) Signup and view all the answers

After suffering a stroke, a patient has difficulty performing precise finger movements. Which descending tract is most likely affected?

Lateral Corticospinal (D) Signup and view all the answers

A person flinches and turns their head rapidly in response to a sudden loud noise. Which descending tract facilitates this response?

Tectospinal (D) Signup and view all the answers

Which of the following best describes the function of the reticulospinal tract?

Regulation of posture and muscle tone. (C) Signup and view all the answers

What would be the most likely result of damage to the anterior corticospinal tract?

Impaired movement of proximal muscles on both sides of the body. (C) Signup and view all the answers

If a patient has damage to the medial vestibulospinal tract, which deficit would you most likely observe?

Difficulty stabilizing head position during movements. (D) Signup and view all the answers

A patient reports a selective loss of vibration sense in their lower extremities. Which pathway is most likely compromised?

Gracile fasciculus (B) Signup and view all the answers

How does reciprocal inhibition contribute to the stretch reflex?

It causes relaxation of antagonist muscles, allowing the agonist muscle to contract without opposition. (D) Signup and view all the answers

During a weight-bearing flexor reflex, what is the role of the contralateral extension?

To maintain balance and support the body's weight while the ipsilateral limb is withdrawn. (A) Signup and view all the answers

What is the most likely explanation for the disappearance of the walking/stepping reflex around 5-6 months of age?

Cortical maturation leads to inhibition of the reflex pathways, allowing for more voluntary control of movement. (C) Signup and view all the answers

What is the key distinction between ascending tracts and descending tracts in the spinal cord?

Ascending tracts carry sensory information from the body to the brain, while descending tracts transmit motor commands from the brain to the body. (D) Signup and view all the answers

Why might the absence of the parachute reflex after 6-7 months post-birth raise concerns for a pediatrician?

It may be a sign of delayed motor development or neurological impairment. (B) Signup and view all the answers

What is the primary role of the third-order neuron in an ascending sensory pathway?

To transmit sensory information from the thalamus to the cerebral cortex for conscious perception. (B) Signup and view all the answers

How do gamma motor neurons contribute to muscle spindle function?

They innervate intrafusal muscle fibers, adjusting their tension and sensitivity to stretch. (C) Signup and view all the answers

Why are reflexes like the palmar grasp and rooting reflex present in infants but not typically in healthy adults?

These reflexes are mediated by subcortical structures that are gradually inhibited by the developing cerebral cortex. (B) Signup and view all the answers

What is the clinical significance of Babinski's sign in adults, and how does it relate to frontal lobe disorders?

Babinski's sign suggests damage to the corticospinal tract, such as in frontal lobe disorders where inhibitory control is compromised. (D) Signup and view all the answers

How does a sudden stretch impact the resultant contraction in the stretch reflex, and what neural mechanism underlies this phenomenon?

A sudden stretch increases the magnitude of the contraction due to heightened activation of muscle spindles, resulting in increased alpha motor neuron firing. (D) Signup and view all the answers

Which scenario exemplifies the most critical role of central pattern generators in the spinal cord?

Facilitating repetitive muscle contractions during walking. (A) Signup and view all the answers

During a rapid eccentric contraction (muscle lengthening under load), what is the MOST significant role of gamma motor neurons associated with muscle spindles?

To maintain the tension and sensitivity of intrafusal fibers, allowing the spindle to detect changes in muscle length during the stretch. (D) Signup and view all the answers

In a complex motor task requiring precise control and fine motor skills, such as playing the piano, where would you expect to find the highest density of muscle spindles?

In the muscles of the fingers and hands. (A) Signup and view all the answers

Which of the following represents the MOST accurate sequence of events in a typical spinal reflex arc?

Stimulus → Receptor → Sensory neuron → Integration center → Motor neuron → Effector → Action (B) Signup and view all the answers

Why are spinal reflexes characterized as involuntary, and what implications does this have for their execution?

Spinal reflexes are not subject to conscious control; they are processed at the level of the spinal cord, allowing for rapid, automatic responses to stimuli. (B) Signup and view all the answers

What is the functional significance of the distinction between primary and secondary sensory fibers within a muscle spindle?

Primary fibers provide information about both the rate of change and the length of the muscle, whereas secondary fibers primarily provide information about muscle length. (C) Signup and view all the answers

How does the concept of 'neural integration' within the spinal cord contribute to complex motor functions?

By summating and processing both excitatory and inhibitory signals, allowing modulation of motor neuron activity and coordinated muscle actions. (A) Signup and view all the answers

How would the disruption of gamma motor neuron function MOST directly impact motor control and proprioception?

It would impair the ability of muscle spindles to detect changes in muscle length, especially during movement, leading to inaccurate proprioceptive feedback and motor incoordination. (C) Signup and view all the answers

Considering the role of the spinal cord in both conduction and neural integration, how do these functions interact to produce a coordinated motor response to a sensory stimulus?

Conduction carries sensory information to the integration center, where interneurons process the signal and modulate motor neuron activity to generate a context-appropriate response. (B) Signup and view all the answers

Monosynaptic reflexes involve direct activation of a motor neuron by a sensory neuron, bypassing interneurons. How does this unique neural circuit influence the characteristics of the resulting reflex?

It leads to a faster and more direct response, as the signal does not need to be processed through additional interneurons. (D) Signup and view all the answers

A patient presents with selective damage to the medulla oblongata, specifically affecting decussation of sensory pathways. Which sensory deficit would MOST likely be observed as a direct result of this damage?

Contralateral loss of fine touch sensation in the upper extremities. (B) Signup and view all the answers

Why is the integration center considered a crucial component of the reflex arc?

It analyzes sensory information and determines the appropriate motor response. (B) Signup and view all the answers

A lesion completely transects the anterior spinocerebellar tract at the level of the lumbar spinal cord. Which functional deficit would MOST likely be observed in the patient?

Impaired coordination and balance without conscious awareness. (A) Signup and view all the answers

A patient suffers a stroke that selectively damages the lateral corticospinal tract in the right cerebral hemisphere. Which of the following deficits would MOST likely be observed?

Contralateral deficits in fine motor control. (D) Signup and view all the answers

What is the functional significance of the high density of muscle spindles in muscles responsible for fine motor control?

Provides precise and rapid feedback about muscle length and changes in length. (A) Signup and view all the answers

How do gamma motor neurons contribute to the sensitivity of muscle spindles, particularly during muscle shortening?

By maintaining tension on intrafusal fibers, ensuring the spindle remains responsive. (C) Signup and view all the answers

A patient exhibits impaired postural control and difficulty coordinating movements of the trunk. Which descending tract is MOST likely affected?

Reticulospinal tract (C) Signup and view all the answers

What would be the most likely effect of damage to central pattern generators in the spinal cord?

Inability to perform rapid, alternating movements like running or swimming. (C) Signup and view all the answers

Following a traumatic injury, a patient exhibits an inability to turn their head in response to sudden auditory or visual stimuli. Which descending tract is MOST likely compromised?

Tectospinal tract (A) Signup and view all the answers

How do primary and secondary sensory fibers within muscle spindles differ in their functional contributions?

Primary fibers respond to both length and rate of change in length, while secondary fibers primarily indicate length. (C) Signup and view all the answers

A patient has a lesion affecting the anterior corticospinal tract at the level of the cervical spinal cord. Which motor deficits would MOST likely result from this lesion?

Weakness in axial muscles, affecting posture and balance. (D) Signup and view all the answers

In the context of spinal reflexes, what is the functional significance of their involuntary nature?

It enables rapid responses to stimuli, bypassing conscious processing for protection. (B) Signup and view all the answers

A lesion selectively damages the lateral vestibulospinal tract. Which of the following deficits would be MOST anticipated?

Difficulty maintaining balance in response to tilting. (D) Signup and view all the answers

A patient experiences a spinal cord injury that selectively disrupts the spinothalamic tract. Which sensory deficit would MOST likely result from this injury?

Loss of pain and temperature sensation on the contralateral side of the body. (B) Signup and view all the answers

How does the absence of a spinal reflex typically present in infants, such as the Moro reflex, at a later developmental stage raise clinical concern?

It suggests a potential issue with sensorimotor integration or neurological development. (A) Signup and view all the answers

What role does the spinal cord play in neural integration, and how does this contribute to complex motor functions?

It integrates sensory input with motor commands, allowing for modulated and coordinated responses. (A) Signup and view all the answers

A patient presents with damage to the fasciculus cuneatus. Which specific sensory function would likely be compromised?

Fine touch sensation from the upper limbs. (D) Signup and view all the answers

Considering a patient with damage to the spinoreticular tract, which of the following clinical presentations would be the MOST expected?

Altered levels of arousal and increased sensitivity to chronic pain. (B) Signup and view all the answers

How does reciprocal inhibition contribute to the function of spinal reflexes, specifically during movements?

It ensures smooth and coordinated movements by inhibiting the activity of antagonist muscles. (B) Signup and view all the answers

What is the functional significance of the anatomical separation of sensory and motor pathways within the spinal cord?

It prevents signal interference, ensuring efficient and specific communication between the brain and periphery. (A) Signup and view all the answers

An adult patient with a known history of frontal lobe damage exhibits a pronounced palmar grasp reflex. What is the MOST likely explanation for this clinical finding?

The frontal lobe damage has disinhibited primitive reflexes, allowing the palmar grasp reflex to re-emerge. (D) Signup and view all the answers

During a neurological examination, an adult patient exhibits Babinski's sign. What does this finding suggest about the patient's neurological status?

It suggests potential damage or dysfunction along the corticospinal tract. (D) Signup and view all the answers

In a scenario where a person quickly steps on a sharp object, what is the MOST crucial role of the contralateral extension reflex that accompanies the flexor reflex?

To maintain balance and support the body's weight as the opposite leg is flexed. (D) Signup and view all the answers

What aspect of the stretch reflex is MOST immediately dependent on reciprocal inhibition?

The relaxation of antagonist muscles to allow the desired movement to occur unimpeded. (A) Signup and view all the answers

Why does the walking/stepping reflex typically disappear around 5-6 months of age in infants?

Because of the maturation of higher-level motor control centers in the brain that inhibit the reflex. (B) Signup and view all the answers

During rapid eccentric contraction, what is the MOST significant role of gamma motor neurons associated with muscle spindles?

To maintain the sensitivity of the muscle spindle so it can detect changes in muscle length; preventing sensory saturation. (D) Signup and view all the answers

First-order neurons in ascending sensory pathways serve what primary function?

To relay sensory information from the periphery to the spinal cord or brainstem. (D) Signup and view all the answers

What is the primary function of the third-order neuron in an ascending sensory pathway?

To transmit sensory information from the thalamus to the cerebral cortex. (C) Signup and view all the answers

Flashcards

Spinal Cord: Conduction

Pathways for sensory (ascending) and motor (descending) information to travel to/from the brain.

Spinal Cord: Neural Integration

The spinal cord integrates sensory input and generates motor output, e.g., bladder control.

Spinal Cord: Locomotion

The repetitive motor sequences such as walking are controlled by central pattern generators in the spinal cord.