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40 Cards in this Set
- Front
- Back
Reflex |
Involuntary, stereotyped response to a sensory stimulus |
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What are the 3 required components of a reflex? |
Receptor Sensory (afferent) neuron Motor (efferent) neuron |
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What nerves to spinal reflexes involve? |
Sensory - dorsal root ganglion neurons Motor - ventral horn Interneurons are also often involved to connect the sensory and the motor |
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Monosynpatic Reflex |
One synapse Does not utilize an interneuron |
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Disynaptic reflex |
2 synapses Utilizes a motor neuron |
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Multisynaptic reflex |
Many neurons and synapses |
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What are the 3 principal spinal (segmental) reflexes involving the limbs? |
Muscle stretch reflex Flexor withdrawal Golgi tendon organ |
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Muscle Spindle |
Stretch receptor embedded within the muscle |
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In the muscle stretch reflex, what does the sensory neuron synapse on? |
alpha motor neurons |
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What kind of reflex is the muscle stretch reflex? |
Monosynaptic |
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Knee-Jerk Reflex Process |
1. Patellar tendon is tapped --> stretch the quadriceps muscle 2. Muscle spindles are stretch --> excite sensory neurons 3. Sensory neuros synapse on alpha motor neurons and gamma motor neurons 4. Alpha motor neurons cause the contraction of the muscle 5. Gamma motor neurons reset the muscle spindle to maintain sensitivity and muscle tone |
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In the case of peripheral nerve injury, what would happen to the muscle stretch reflex? |
Hyporeflexia Areflexia Due to disruption of the reflex arc |
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In the case of CNS injury, what would happen to the muscle stretch reflex? |
Hyperreflexia due to the disruption of inhibitory input |
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Clonus |
Repetitive vibratory movements characteristic of an upper motor neuron injury |
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Triceps reflex: muscles invovled |
Triceps brachii |
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Triceps reflex: spinal cord segments |
C6, C7, (C8) |
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Triceps reflex: peripheral nerve |
radial |
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Biceps reflex: muscles |
biceps brachii |
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Biceps reflex: spinal cord segments |
C5, C6 |
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Biceps reflex: peripheral nerve |
musculocutaneous |
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Knee-jerk reflex: muscles |
quadriceps femoris |
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Knee-jerk reflex: spinal cord segments |
L3, L4 |
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Knee-jerk reflex: peripheral nerve |
femoral |
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Ankle-jerk reflex: muscles |
gastrocnemius Soleus |
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Ankle-jerk reflex: spinal cord segments |
S1, S2 |
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Ankle-jerk reflex: peripheral nerve |
tibial |
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What are the 2 major functions of the gamma motor neurons? |
Maintain the sensitivity of the muscle spindle Determine muscle tone |
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Muscle tone |
Slight tension in a muscle that allows for normal function |
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What nerves are involved in maintaining normal muscle tone? |
Gamma motor neurons and alpha motor neurons |
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What is the activity of muscle tone controlled by? |
Descending motor systems --> inhibitory control |
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How is muscle tone assessed clinically? |
By passively extending and flexing the limbs |
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What is an increase in muscle tone indicative of? |
Injury to the descending control of the gamma loop Upper motor neuron lesion |
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What is a decrease in muscle tone indicative of? |
peripheral nerve injury lower motor neuron lesion |
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Spasticity |
Velocity-dependent resistance to passive stretch and typically results form injury to the descending motor systems controlling the muscle stretch reflex |
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Rigidity |
Characterized by increased uniform resistance that persists throughout the whole range of motion and typically results from injury to the basal ganglia |
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Flexor Withdrawal Reflex |
1. Pain receptors activate excitatory interneurons 2. Interneurons synapse with flexor muscles to withdraw limb 3. Flexion is facilitated because the afferents synapse with inhibitory neurons which synapse with antagonistic extensor muscles |
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What kind of reflex is the flexor withdrawal reflex? |
Disynpatic |
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Where are golgi tendon organs located? |
Junction between the muscle fiber and the tendon |
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What kind of information does the golgi tendon organ provide? |
Amount of tension in an organ |
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Golgi tendon organ reflex |
1. Afferent fiber of golgi tendon organ innervates inhibitory neurons that project to motor neurons supplying the same muscle from which the afferent originates 2. Activation of afferent --> inhibition of motor neurons supplying the muscle that experiences the stretch --> relaxation of the muscle |