8711300
| Question | Answer |
| What is a reflex? | Rapid involuntary stereotyped response to sensory stimulis. Inc. muscle contraction and glandular responses (eg lactation) |
| Describe spinal reflexes | Need stim, quick (few synapses), involuntary, automatic (little higher input) & stereotyped(simple circuitry) |
| Describe how the patellar reflex occurs | Stim to knee -> Spinal nerve to ventral root ->direct synapse to motor -> Passes through dorsal root & dorsal root ganglion -> stims extensor muscle contraction |
| Why does the patellar reflex occur? | Thigh extensor muscle stretches, reflex corrects stretching - PROPRIOCEPTIVE system |
| Describe the stretch reflex | Sensory fibre detects stretch and signals spinal cord -> Direct connection to motor neuron & AP contracts bicep -> At same time connection to inhibitory neuron inhibits m neurons in tricep so it relaxes (RECIPROCAL INHIBITION) |
| What are muscle spindles? | Proprioceptors (sense organs that monitor position and movement of body parts). Found in striated muscle esp ones involved in fine motor control |
| Describe muscle spindle innervation | Innervated by Ia sensory fibres which provide feedback on amount of muscle stretch occurring to alpha motor neurons innervating the surrounding muscles |
| What are gamma motor neurons | Their axons also innervate muscle spindles. Stim intrafusal (muscle) fibres to adjust spindle tension as extrafusal (muscle) fibres contract, so spindle is never slack |
| Loss of proprioception | Ian Waterman- 1972 infection destroyed his proprioception. Has to monitor every action. Also lost kinesthesia (sense of body moving in space) |
| Describe the Golgi Tendon Organ | Proprioceptor that detects muscle tension due to contraction. GTO sensory (Ib) afferent activation activated inhibitory interneurons which inhibit alpha motor neurons of that muscle. Prevents muscle contracting too much |
| Describe the flexor reflex | Flexor muscles contract quickly to withdraw limb from injurious stimulus (eg. heat). Results from activation of nociceptors. Postsynaptic reflec (multiple interneurons activate to sustain response --> PARALLEL AFTER DISCHARGE CIRCUIT) |
| Why do flexor reflexes often include contralateral elements? | Because rapid withdrawal of a limb may lead to imbalance |
| What is the role of inhibitory interneurons in the flexor reflex? | Activate to relax extensor muscles (reciprocal inhibition) |
| Describe the crossed extensor reflex | Pain in fight foot -> sensory activates excitatory and inhib. interneurons -> Ipsilat. m. neurons to flexor excite -> Ipsilat. flexor contracts -> Contralat. m. neurons to extensor excite -> Contralat. extensor contracts |
| What effect does spinal cord severing have on activity alternation & what does this imply? | Basic activity alternation continues, which implies local circuits generate patterns of alternating flexion and tension (central pattern generators) |
| Nematode proprioception | TRP4 loss leads to loopy swimming. DVA neuron detects body bending directly, repetitive spikes in swimming. DVA inhibits motor neurons |
| Describe Meissner corpuscles | Location: Dermal papillae of skin (palm,eyelid/lips,tongue) Modality: Light, touch, texture (movement) Sensitive to 30-50 Hz Adapt rapidly |
| Describe Pacinian Corpuscles | Location: dermis, joint capsules and viscera Modality: Deep pressure, stretch, tickle, vibration Sensitive to 250-350 Hz Adapt rapidly |
| Describe Ruffini Corpuscles | Location: dermis, subcutaneous tissue, joint capsules |
| Brain-->Spinal cord | Cranial/Rostral & caudal |
| Top of arm/leg--->Bottom of arm/foot | Proximal & Distal |
| Head-->Feet | Superior, Inferior |
| Front--> back | Anterior/Ventral,Posterior/dorsal |
| Middle of torso --> Hand | Medial,Lateral |
| Same side of body/ Opposite side of body | Ipsilateral / contralateral |
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