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42 Cards in this Set
- Front
- Back
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Once a sensory signal enters the gray matter of the spinal cord, where does the signal get sent? (2 places)
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1) motor neuron to initiate reflex or 2) up the cord to a higher region (brain or higher cord) for control
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2 types of anterior motor neurons
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alpha and gamma
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Function of alpha motor neurons?
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stimulate skeletal muscle motor units (type Aa)
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Function of gamma motor neurons?
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stimulate skeletal muscle intrafusal fibers (type Ay) as found in the muscle spindle
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Before a sensory nerve synapses on a moor neuron in the cord, what is typically found between them?
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interneuron that will process the information
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What are Renshaw Cells?
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inhibitory cells near motor neurons that inhibit adjacent motor neurons = "lateral inhibition"
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Why is "lateral inhibition" by Renshaw cells important?
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force direction of the action potential/impulse in one direction. by inhibiting the neighboring neurons, we prevent the action potential from diffusing away and focus all the power to one neuron/pathway
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What are propriospinal fibers?
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fibers that run up and down the spinal cord to different levels can communicate; used in multi-segmental reflexes
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Sensory function of muscle spindles
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report muscle length and rate of length change
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Sensory function of golgi tendon organ
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report muscle tension and rate of tension change
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Motor innervation of the muscle spindle (the ends of the fibers) is by which type of nerves?
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gamma efferent fibers
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Sensory innervation of the muscle spindle (the middle of the fibers) is by which type of nerves?
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type 1a fibers (primary ending) and type 2 fibers (secondary ending)
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2 types of intrafusal muscle spindle fibers
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nuclear bag muscle fibers and nuclear chain muscle fibers
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The secondary ending of the muscle spindle sends sensory information via (nuclear bag or nuclear chain fibers)?
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nuclear chain is associated with secondary ending. primary ending uses both bag and chain
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What is the "static response" of the muscle spindle?
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as a muscle stretches slowly, the firing of the primary AND secondary endings is directly proportional to the stretch for minutes as long as the stretch is still there
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What is the "dynamic response" of the muscle spindle?
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only the primary ending fires (rapidly) when there is a quick rate of change in the muscle spindle fiber
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gamma dynamic fibers control which type of muscle spindle fibers? (Nuclear bag or chain)
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nuclear chain fibers
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gamma static fibers control which type of muscle spindle fibers? (Nuclear bag or chain)
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nuclear bag fibers
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Which ending (primary or secondary) is responsible for the dynamic response?
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primary only
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Dynamic reflexes have what end result?
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a contraction/relaxation of a muscle to oppose the rapid rate of change in muscle length
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What is "damping"?
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the stretch reflex serve a "damping" purpose to elicit a smooth response rather than a jerky one with repeated firing
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What is "coactivation" and why is it important?
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coactivation refers to the alpha and gammg motor neurons being activated together to stretch the muscle spindle and normal skeletal muscle together. this is important since the muscle spindle should stay at a proportional stretch to the actual muscle to avoid over compensation
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How does a muscle spindle wok to stabilize body position?
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if both ends of a joint are activated, the muscle spindle leads to reflex excitation on both ends causing the muscles on both ends of the joint to tighten and stabilize the joint
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Exaggerated knee jerk reactions might be caused by (upper or lower) motor neuron lesions?
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upper lesion = hyper-reflexia
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What is clonus?
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oscillation of muscle jerks
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Golgi tendon organ uses what nerve fibers to relay sensory information?
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type 1b
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The golgi tendon organ sensory neuron synapses with an interneuron in the cord before synapsing on a motor neuron. This interneuron conveys what type of signal to the motor neuron?
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inhibitory. to provide negative feedback to stop contraction since the muscle is too tight
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With regards to the golgi tendon, what is the "lengthening reaction"?
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when a muscle/tendon is too tight, it sends a signal into the spinal cord that elicits an inhibitory response = muscle relaxation so the tight muscle doesn't get damaged
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For the "flexor reflex", what motor pathways are in use?
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motor activation to the flexor muscle, motor inhibition to the extensor, afterdischarge
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What is the crossed extensor reflex?
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when a flexor reflex occurs, the extensor on the opposite limb will contract (the extensor on the same side as the stimulus will be inhibited)
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What is the positive supportive reaction?
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pressure on the bottom of the foot = tighten muscle to support the standing
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What is the magnet reaction?
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pressure on one side of the body (e.g. foot pads) = extension of the limb in that direction = prevents us from falling to that side
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What are "cord righting reflexes"?
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when laying on one side, a spinal animal will make movements to return to straight
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What is the "stumble" reflex?
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if the foot is taking a step forward and encounters an obstruction it will raise even higher reflexively
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If the lumbar spine was not split down the middle, forward stepping of the right leg would be accompanied by what movement of the left leg?
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it would move backwards due to reciprocal innervation. the contralateral extensor muscles are innervated with the ipsilateral flexors
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What is the "mark time reflex"?
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diagonal innervation of all 4 limbs
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What is the "gallop reflex"?
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both forelimbs move together (e.g. flexion) and both the hind-limbs move in the opposite direction (e.g. extension)
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Why is deep anesthesia needed for intra-abdominal surgeries?
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irritation of the parietal peritoneum can cause an abdominal muscle spasm which can protrude the organs out of a surgical incision. this i bad so anesthesia must prevent this reflex
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Initial irritation of a muscle can lead to what type of feedback loop?
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positive feedback, leading to worse and worse spasm with irritation until the muscle cramps.
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What is "mass reflex"?
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excessive activity of the spinal cord = massive discharge
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What is spinal shock?
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sudden transection of the cord - immediate depression of spinal cord activity
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At the onset of spinal shock, what happens to BP?
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drops, sympathetic innervation is no longer vaso-constricting
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