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Questions and Answers
Which component is not part of the reflex arc?
Which component is not part of the reflex arc?
- Sensory receptor
- Neuromuscular junction
- Motor neuron
- Cerebral cortex (correct)
What is the primary function of a sensory (afferent) neuron in a reflex arc?
What is the primary function of a sensory (afferent) neuron in a reflex arc?
- To cause muscle contraction directly
- To carry impulses from the brain to the muscle
- To connect a sensory neuron to a motor neuron
- To carry sensory impulses to the central nervous system (correct)
What characterizes a monosynaptic reflex?
What characterizes a monosynaptic reflex?
- It always results in the inhibition of muscle contraction.
- It requires conscious thought.
- It involves multiple interneurons within the spinal cord.
- It involves a single synapse between a sensory and a motor neuron. (correct)
Which of the following is an example of a monosynaptic reflex?
Which of the following is an example of a monosynaptic reflex?
What role does an interneuron play in a polysynaptic reflex arc?
What role does an interneuron play in a polysynaptic reflex arc?
Which of the following reflexes is polysynaptic?
Which of the following reflexes is polysynaptic?
How does a reflex differ from a response?
How does a reflex differ from a response?
If the spinal cord is severed cranial to the reflex arc, which of the following would still be present?
If the spinal cord is severed cranial to the reflex arc, which of the following would still be present?
Damage to the lower motor neurons (LMN) typically results in which of the following?
Damage to the lower motor neurons (LMN) typically results in which of the following?
What is characteristic of upper motor neuron (UMN) damage, compared to lower motor neuron (LMN) damage?
What is characteristic of upper motor neuron (UMN) damage, compared to lower motor neuron (LMN) damage?
If the spinal cord is damaged in the C6-T2 region, which limb would be affected?
If the spinal cord is damaged in the C6-T2 region, which limb would be affected?
Which nerves are involved in the pupillary light reflex?
Which nerves are involved in the pupillary light reflex?
The menace response involves which action?
The menace response involves which action?
What nerve mediates the perineal reflex?
What nerve mediates the perineal reflex?
Which functional segment of the spinal cord controls the bladder, anus, and tail function?
Which functional segment of the spinal cord controls the bladder, anus, and tail function?
The cutaneous trunci muscle is innervated by what?
The cutaneous trunci muscle is innervated by what?
In the stretch reflex, where does the afferent (sensory) neuron send information?
In the stretch reflex, where does the afferent (sensory) neuron send information?
Which of the following is the correct sequence of events in a reflex arc?
Which of the following is the correct sequence of events in a reflex arc?
If you are testing the depth of anesthesia, which reflex would you MOST likely assess?
If you are testing the depth of anesthesia, which reflex would you MOST likely assess?
Which reflex relies on coordinated contraction of many flexor muscles across several joints?
Which reflex relies on coordinated contraction of many flexor muscles across several joints?
Following a spinal cord injury at L2, what deficits would you primarily expect to observe?
Following a spinal cord injury at L2, what deficits would you primarily expect to observe?
What is the functional consequence of damaging the sensory neuron in a monosynaptic reflex arc?
What is the functional consequence of damaging the sensory neuron in a monosynaptic reflex arc?
Which statement accurately describes how the menace response differs from a reflex mediated solely by the spinal cord?
Which statement accurately describes how the menace response differs from a reflex mediated solely by the spinal cord?
How does the absence of the panniculus reflex caudal to the mid-thoracic region relate to the localization of a spinal cord lesion?
How does the absence of the panniculus reflex caudal to the mid-thoracic region relate to the localization of a spinal cord lesion?
A patient presents with exaggerated patellar reflexes bilaterally. What could this indicate about the location of the lesion?
A patient presents with exaggerated patellar reflexes bilaterally. What could this indicate about the location of the lesion?
Why is use of excessive force inappropriate when eliciting a withdrawal reflex?
Why is use of excessive force inappropriate when eliciting a withdrawal reflex?
Damage confined to the interneuron within a reflex arc will most directly affect which aspect of that reflex? Assume a typical 3-neuron arc.
Damage confined to the interneuron within a reflex arc will most directly affect which aspect of that reflex? Assume a typical 3-neuron arc.
You are examining a dog with suspected spinal cord trauma. When performing the patellar reflex test, you notice an absence of the reflex in the right hind limb and an exaggerated reflex in the left hind limb. Given this information, where is the MOST likely location and nature of the spinal cord lesion?
You are examining a dog with suspected spinal cord trauma. When performing the patellar reflex test, you notice an absence of the reflex in the right hind limb and an exaggerated reflex in the left hind limb. Given this information, where is the MOST likely location and nature of the spinal cord lesion?
Which clinical scenario BEST illustrates a situation where the pupillary light reflex is present, but the menace response is absent?
Which clinical scenario BEST illustrates a situation where the pupillary light reflex is present, but the menace response is absent?
After administering a neuromuscular blocking agent, which component of the reflex arc is FIRST affected?
After administering a neuromuscular blocking agent, which component of the reflex arc is FIRST affected?
In performing a neurological exam on a horse, you note an absent withdrawal reflex but a normal patellar reflex in the same limb. Based on this finding, which of the following is the MOST likely location of the lesion?
In performing a neurological exam on a horse, you note an absent withdrawal reflex but a normal patellar reflex in the same limb. Based on this finding, which of the following is the MOST likely location of the lesion?
What type of nerve fiber is responsible for transmitting sensory information from the skin receptor to the spinal cord in a polysynaptic reflex?
What type of nerve fiber is responsible for transmitting sensory information from the skin receptor to the spinal cord in a polysynaptic reflex?
After an injury to the spinal cord at the T3-L3 region, what reflex would a veterinarian MOST likely examine to evaluate bladder function in a small animal?
After an injury to the spinal cord at the T3-L3 region, what reflex would a veterinarian MOST likely examine to evaluate bladder function in a small animal?
In a patient with a severed spinal cord at C7, what aspect of the panniculus reflex would be MOST likely observed?
In a patient with a severed spinal cord at C7, what aspect of the panniculus reflex would be MOST likely observed?
Why is the pupillary light reflex considered a polysynaptic reflex arc?
Why is the pupillary light reflex considered a polysynaptic reflex arc?
A veterinarian is performing a neurological examination on a dog that experienced some trauma after being hit by a car including a fractured femur. What is a critical strategy that should be employed when assessing reflexes to ensure accurate interpretation?
A veterinarian is performing a neurological examination on a dog that experienced some trauma after being hit by a car including a fractured femur. What is a critical strategy that should be employed when assessing reflexes to ensure accurate interpretation?
Flashcards
What is a reflex?
What is a reflex?
A simple, involuntary reaction to a stimulus.
What's included in a reflex arc?
What's included in a reflex arc?
Sensory receptors, sensory neurons, spinal cord segment, motor neurons, neuromuscular junction, and the target muscle or organ.
What is a monosynaptic reflex?
What is a monosynaptic reflex?
Small segment of the nervous system; tests a very specific area.
What is a polysynaptic reflex?
What is a polysynaptic reflex?
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What is a stimulus?
What is a stimulus?
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What is a receptor?
What is a receptor?
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What are sensory (afferent) neurons?
What are sensory (afferent) neurons?
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What is an interneuron?
What is an interneuron?
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What are motor (efferent) neurons?
What are motor (efferent) neurons?
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What is a monosynaptic reflex?
What is a monosynaptic reflex?
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What initiates the monosynaptic reflex?
What initiates the monosynaptic reflex?
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What muscle is involved in the monosynaptic reflex?
What muscle is involved in the monosynaptic reflex?
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What is the patellar reflex?
What is the patellar reflex?
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What is a polysynaptic reflex?
What is a polysynaptic reflex?
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What does the polysynaptic reflex involve?
What does the polysynaptic reflex involve?
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What does the withdrawal reflex involve?
What does the withdrawal reflex involve?
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What is a reflex?
What is a reflex?
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What is a response?
What is a response?
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What is a lower motor neuron (LMN)?
What is a lower motor neuron (LMN)?
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What is an upper motor neuron (UMN)?
What is an upper motor neuron (UMN)?
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What is the menace response?
What is the menace response?
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What is the pupillary light reflex?
What is the pupillary light reflex?
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What is the panniculus reflex?
What is the panniculus reflex?
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What is the palpebral reflex?
What is the palpebral reflex?
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What is the perineal reflex?
What is the perineal reflex?
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Study Notes
- A reflex arc facilitates a simple, involuntary reaction to a stimulus.
Reflex Arc Components
- Sensory receptors detect the stimulus.
- Sensory neurons transmit the signal.
- The spinal cord segment processes the information.
- Motor neurons carry the response signal.
- Neuromuscular junction facilitates signal transmission to the muscle.
- Muscle or other end organ executes the response.
Monosynaptic Reflex
- Involves a small segment of the nervous system, testing a very specific area.
- An example is the patella reflex.
- Characterized as simple, uncommon, and rapid.
- Known as the stretch reflex.
- The Process includes the stretch on the tendon stimulating muscle spindles
- Information passes via the afferent sensory neuron to the spinal cord and the impulse transmitted to the efferent motor neuron innervating the quadriceps muscle.
- There is no interneuron involved.
Patellar Reflex
- It is a monosynaptic reflex.
- A test of the femoral nerve.
- Striking the patellar ligament should result in the contraction of the quadriceps muscle.
Polysynaptic Reflex
- Involves a broad area and multiple segments.
- An example is the withdrawal reflex.
- There may be involvement of motor neurons to several muscles and involve inhibition of muscle contraction.
- An interneuron is utilized in the spinal cord.
- The skin receptor detects a stimulus, passing it to the sensory neuron, which synapses on an interneuron; this then synapses at a motor neuron, reaching a muscle via the spinal cord.
Withdrawal Reflex
- It is a polysynaptic reflex.
- Pinching a limb results in flexion of all joints in the limb.
- Coordinated contraction of many flexor muscles occurs across several joints.
- A message is sent to the opposite leg to engage extensor muscles.
- If too much force is used, the test assesses pain, not the reflex.
Reflex vs Response
- A reflex only involves the spinal cord and doesn't require conscious thought.
- Reflexes are present even if the spinal cord is severed cranial to the reflex.
- A response carries sensory information to the brain for interpretation.
Lower Motor Neuron (LMN)
- Motor neuron in the peripheral nervous system that connects directly to the muscle.
- It originates in the grey matter of the spinal cord within the reflex arc area
- Damage is more likely to be permanent.
- Results in flaccid muscle tone (loose and floppy) and weak or absent reflexes.
Upper Motor Neuron (UMN)
- Located totally in the CNS
- Communicates with the LMN to initiate motor movement.
- It originates in the brain and travels within the spinal cord to communicate with the LMN in the gray matter.
- Resulting in some tone in muscles, where muscle tone is often exaggerated.
- Damage is more likely to recover as the UMN has the ability to find a new neuron connection.
Spinal Functional Segments
- Higher Cervical C1-C5: UMN
- Lower Cervical C6-T2,: LMN to front and UMN to the rear
- Thoracolumbar T3-L3: UMN to the rear
- Lumbosacral L4-S3: LMN to the rear legs
- Sacrocaudal S1: caudal; LMN to the bladder, anus, and tail
Menace Response
- Blinking in response to a potentially harmful object moving toward the eye
- The opposite eye must be covered during testing.
- A positive response is blinking.
- Not seen in puppies/kittens under 16 weeks old.
- It is a learned response.
Pupillary Light Reflex
- It is a polysynaptic reflex.
- It involves cranial nerve II (optic nerve) and cranial nerve III (oculomotor nerve).
- It does not assess vision.
- The pupil will constrict with bright light.
Panniculus Reflex
- Polysynaptic reflex.
- Light touch is applied along the dorsal surface of the back.
- The muscle along the back is the cutaneous trunci.
- A stimulus to the trunk causes the cutaneous trunci muscle to twitch.
- Ascending sensory tracts extend up the spinal cord to the cell body of the lateral thoracic nerve in spinal cord segment C8.
- The lateral thoracic nerve supplies motor innervation to the cutaneous trunci.
Palpebral Reflex
- Polysynaptic reflex.
- Touching the eyelid sends sensory information over the trigeminal nerve (CN V) to synapse with the facial nerve (CN VII) in the brain stem.
- Motor fibers of the facial nerve cause the orbicularis oculi muscle to contract.
- Often used to evaluate the depth of anesthesia.
Perineal Reflex
- Polysynaptic reflex.
- It is tested by touching the sides of the perineal area.
- A positive test results in contraction of the anal sphincter and flexion of the tail.
- Mediated by the pudendal nerve, with roots from S1-S3.
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