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Spinal reflexes
| Question | Answer |
|---|---|
| What is a reflex? | Fast, involuntary, unplanned sequence of action that occurs in response to a particular stimulus and helps to maintain homeostasis |
| What serves as the integrating center for spinal reflexes and where does it occur? | Spinal cord, grey matter |
| Are reflexes cranial or spinal? | Can be either |
| What makes up a reflex arc? | Specific neuronal circuit that includes at least synapse |
| What is the purpose of a reflex arc? | Helps maintain homeostasis by permitting the body to make exceedingly rapid adjustments to homeostatic imbalances |
| What are the components of a reflex arc? | Receptor, sensory neuron, integrating center, motor neuron, and effector |
| What kind of innervation do reflexes exhibit? | Reciprocal innervation which is contraction of one muscle and relaxation of its antagonistic muscle(s) |
| What is a stretch reflex? | Feedback mechanism to control muscle length by causing muscle contraction |
| What is the purpose of a stretch reflex? | Prevents injury from overstretching by contracting |
| How many synapses are activated and which side does the stretch reflex occur? | Monosynaptic, ipsilateral |
| What detects the stretching of muscles? | Motor spindles |
| What sets muscle spindle sensitivity and muscle tone? | Brain |
| What is muscle tone? | Degree of muscle contraction at rest |
| How is a stretch reflex stimulated? | Muscle spindles signals stretch of muscle which excites the sensory neuron which sends the info to the integrating center (grey matter of spinal cord) which then activates a motor neuron to cause contracture |
| What are some examples of a stretch reflex? | Patellar, achilles, semitendinosus, biceps, brachioradialis, triceps |
| What kind of innervation does a stretch reflex have? | Reciprocal - Polysynaptic-interneuron → antagonistic muscles relax as part of reflex |
| What is a tendon reflex? | Feedback mechanism to control muscle tension by causing muscle relaxation when muscle force becomes too extreme |
| What will a tendon reflex do to activation of original stimulus? | Reverses it |
| What is an example of a tendon reflex? | Making you drop a heavy weight because it is too much |
| How many synapses are activated and which side does the tendon reflex occur? | Polysynaptic, ipsilateral |
| Which structures are being protected in a tendon reflex? | Tendon and muscle |
| What structure detects muscle tension? | Golgi tendon organs in tendons |
| How are golgi tendon organs activated? | Stretching of tendon |
| What happens after a golgi tendon organ is activated? | Inhibitory neuron is stimulated (polysnaptic) and motor neuron is hyperpolarized →muscle relaxes |
| What kind of innervation does a tendon reflex have? | Reciprocal - polysnaptic - causes contraction of ipsilateral muscle group |
| What is a flexor (withdrawal) reflex? | Ipsilateral and protective withdrawal reflex that moves a limb to avoid pain |
| What is the result of a flexor reflex? | Contraction of flexor muscles to move a limb to avoid injury or pain |
| What is the sensory receptor for a flexor reflex? | Dendrites of pain-sensitive neurons |
| Why is a flexor reflex considered and intersegmental reflex arc? | Because in the integrating center of spinal cord (grey matter) sensory neuron activates interneurons in several spinal segments |
| What is the implication of being an intersegmental reflex arc? | More than one muscle groups are activated → triggers crossed extensor reflex |
| What is a crossed extensor reflex? | Contralateral reflex that helps to maintain balance during flexor reflex |
| What activates a crossed extensor reflex? | Pain stimuli that triggered flexor (withdrawal) reflex |
| How does info from another reflex activate a crossed extensor reflex? | Pain signals cross to opposite spinal cord which activates several interneurons that stimulate contralateral extensor muscles |
| What does the babinski reflex test for? | Dysfunction of corticospinal tract - UML |
| What is a positive Babinski's test | When test concludes that there is UMN, dysfunction of corticospinal tract - upward extensor movement |
| What is a negative Babinski's test? | Flexor (downward) movement of foot |
| Babies will test positive for a Babinski's test, is this normal? | Yes, only in adults is it abnormal |
| What does an achilles reflex test for? | Checks if S1 and S2 nerve roots are intact - could be indicative of sciatic nerve pathology or peripheral neuropathy |
| Besides sciatic nerve pathology, when would a reduced achilles reflex occur? | Herniation at L5-S1 |
| What are the 3 columns that make up white matter in the spinal column? | Posterior, lateral, anterior |
| Where is the posterior column? | Between midline and dorsal horn of spinal cord |
| What kind of nerves are in the posterior column? | Purely sensory |
| What are the two tracts within the posterior column? | Gracile fasciculus, Cuneate fasciculus |
| Where is the lateral column? | Between dorsal and ventral horns |
| What kind of nerves are in the lateral column? | Sensory and motor |
| What tracts are in the lateral column? | Corticospinal, rubrospinal, reticulospinal, vestibulospinal |
| Where is the anterior column located? | Between midline and ventral horn of spinal cord |
| What kind of nerves are in the anterior column? | Both sensory and motor |
| What tracts are in the anterior column | Tectospinal tract |
| For inhibition of pain, where would the pathway travel down to? | Spinal cord, in grey matter, in substantia gelatinosa |
Created by:
nnguyen44
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