Term
| what includes descending pathways originating from motor nuclei, brain stem, and all other pathways not part of the pyramidal system |
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Definition
| indirect system (extrapyramidal system) |
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Term
| extrapyramidal pathways are complex and myltisynaptic and regulate: |
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Definition
| axial muscles that maintain balance and posture; muscles controlling coarse movements of the proximal portions of limbs;head, neck, and eye movements |
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Term
| what is the difference between an upper motor neuron lesion and a lower motor neuron lesion? |
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Definition
Lower motor neuron lesion
flaccid paralysis (paralysis accompanied by muscle tone loss)
e.g. poliomyelitis
Upper motor neuron lesion
Spastic paralysis (paralysis accompanied by servere muscle hypertonia, lower motor neurons become hyper-excited) |
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Term
| what are the 2 major functions of the spinal cord? |
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Definition
| provides a 2way conduction pathway to and from the brain (ascending and descending);works as integrating center for somatic and autonomic reflexes |
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Term
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Definition
| an involuntary response to a stimulus |
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Term
| what are reflexes mediated by the spinal cord called? |
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Definition
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Term
| spinal reflexes are automatic and involuntary. can the brain facilitate, inhibit, or adapt the spinal cord via descending pathways? |
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Definition
| yes. it can facilitate, inhibit, or adapt the spinal cord reflexes via descending pathways (pyramidal or extrapyramidal systems) |
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Term
| what are the 5 basic components of the reflex arch? |
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Definition
| receptor, sensory neuron, integration center, motor neuron, effector. |
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Term
| what is the myotatic stretch reflex? |
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Definition
| aka stretch reflex (like the knee jerk reflex) simple version of spinal circuitry involved (monosynaptic, no interneuron involved)(short latent period) |
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Term
| motor neurons innervating skeletal muscle |
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Definition
Motor neuron types associated with skeletal muscle
α motor neurons (part of stretch reflex)
Innervate extrafusal muscle fibers (contractile fibers)
γ motor neurons (not part of stretch reflex)
Innervate contractile region of the intrafusal muscle fibers; maintain spindle sensitivity
α-γ coactivation
α and γ motor neurons are usually co-activated
When a desired change in muscle length is made, the intrafusal muscle fiber length must be adjusted. |
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Term
| what neuron is activated in operation of muscle spindle? |
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Definition
| Only α-motor neuron is activated |
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Term
α-γ Co-activation via Descending Pathways
1) afferent input from sensory endings of muscle spindle fiber
2) alpha motor neuron output to regular skeletal muscle fiber
1/2) stretch reflex pathway
3) gamma motor neuron output to contractile end portions of spindle fiber
4) descending pathways co-activating alpha and gamma motor neurons. |
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Definition
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Term
| what is a golgi tendon reflex and where is it found? |
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Definition
| golgi tendon organ. activated by strong muscle contraction or passive stretching. helps avoid tearing of muscles and tendons. polysynaptic reflex |
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Term
| what is flexor-withdrawal reflex? |
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Definition
| initiated by pain or harmful stimulus. causes automatic withdrawal from stimulus. polysynaptic. reciprocal inhibition. divergence over multiple segments. (step on something and your foot automatically tries to get away from the pain stimulus) |
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Term
| what is crossed entensor reflex |
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Definition
| contralateral limb responded with opposite pattern of reciprocal inhibition. if you step on something with your right foot, your left will adjust to bear the weight |
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Term
Higher CNS Influences Spinal Reflexes
Motor cortex via corticospinal tracts
Brain stem via extrapyramidal tracts
Either facilitation or inhibition
13-27 |
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Definition
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Term
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Definition
| all that is required is for components of reflex arc be intact |
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Term
| Myotatic and somatosensory reflexes mediated by isolated spinal cord are often exaggerated due to loss of inhibitory signals from descending tracts |
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Definition
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