Flashcards
NS 10 - spinal reflexes
Cards in this deck (29)
- 1reflexany response that occurs automatically without conscious effort
- 2afferents enter the spinal cord viaposteriorly via the dorsal root
(afferent cell bodies are in the dorsal root ganglia) - 3efferents exit the spinal cord viaanteriorly via the ventral root
(efferent cell bodies are in the grey matter of the spinal cord) - 4monosynaptic reflexes only haveone synapse between the afferent and efferent limbs
- 5polysynaptic reflexes havemultiple synapses and connections between the afferent and efferent limbs
- 6alpha motor neurons innervateskeletal muscle
- 7gamma motor neurons innervateintrafusal fibres (these are inside muscle spindles)
- 8importance of spinal reflexes (5)coordinate rapid withdrawal responses to painful stimuli
protect against over-stretching of muscles
emptying of pelvic organs (bladder)
purposeful muscle movement and contribute to proper balance and movement (walking, running, standing upright)
learned reflexes in sport - 9what are the 3 components of a reflexperipheral sensory receptors + afferent sensory nerve
integration in the CNS
efferent nerve and effector organ - 10exteroceptorsrespond to external stimuli and provide info about temperature, pressure, etc.
- 11proprioceptorsreceptors in muscles, tendons, joints that provide info about position of limbs in space and relative to the body
- 12interoceptorsreceptors on organs and provide information about pain, stretching of internal organs
- 13stretch reflex ismonosynaptic reflex
brief stretch of skeletal muscle leads to brief contraction of that muscle
functions to oppose sudden changes in muscle length - 14what receptor is used in the stretch reflexmuscle spindles
- 15what is the area of integration for the stretch reflexspinal cord
- 16what is the effector in the stretch reflexthe skeletal muscle being stretched
- 17outline the knee-jerk reflexbrief stretch of quadriceps when tapping the infrapatellar tendon with the tendon hammer
muscle spindles in quadriceps stretches, increases the activity of 1A sensory fibres.
interneurons connect 1A sensory fibres to alpha motor neurons in the spinal cord
quadriceps contracts and the knee extends, kicking the leg forward - 18grading of tendon jerks (0-4)4 - very brisk, often with clonus
3 - brisk, but considered normal
2 - normal
1 - minimal
0 - absent - 19hyperreflexia means why does it happenincreased stretch reflex
UMN lesion
due to damage to motor pathways going from the brain to the spinal cord (can happen after stroke/brain tumour or after damage to the cerebral cortex motor areas) - 20hyporeflexia means why does it happendecreased stretch reflex
results if there is damage at any point of the reflex pathway (receptors --> muscles) - 21areflexia means results fromabsent stretch reflex
lesions of the reflex arc - 22what does reciprocal innervation mean? use knee-jerk response as an exampleduring a stretch reflex, one muscle moves (agonist) - this means that the antagonistic muscle must relax and the stretch reflex must be inhibited in order to allow the agonist to move.
in the knee-jerk response: agonist = quadriceps and the antagonist = semitendinosus - 23what are the muscle sensory receptors? (2) and what do detect?muscle spindles - change in muscle length/time i.e. muscle tone
golgi tendon organs - change in muscle tension/time - 24muscle spindlesare stretched when muscle tone increases and compressed when muscle tone decreases
even when the muscle is relaxed, gamma motor neurons fire and keep the muscle spindles under proper tension
also send info about muscle tone to the brain and cerebellum - 25golgi tendon organsdetect changes in muscle tendons and are proprioceptive
encapsulated and found inside muscle tendons where they are connected to 10-15 muscle fibres
when muscle tension increases, type 1b sensory fibres activate and transmit signals to the spinal cord and brain - preventing too much tension in the muscle - 26examples of a polysynaptic reflex (3)flexor withdrawal reflex
crossed-extensor reflex
acquired/conditioned reflex - 27flexor withdrawal reflexprotective mechanism
afferent = fast, pain-communicating A delta fibres
when you touch a hot plate, A delta pain fibres transmit this sensory data to the spinal cord where they synapse with loads of interneurons which then communicate with the efferent limb. biceps contracts while triceps (antagonist) relaxes and the hand is pulled away from the stimulus
information is sent to the brain for processing - 28crossed-extensor reflexyou step on a sharp object but you don't fall over: 0.2-0.5 secs after the stimulus elicits the flexor reflex in the leg that stepped on the sharp object, the other leg begins to extend because signals from sensory nerves cross to the opposite side of the spinal cord to excite these extensors
- 29acquired/conditioned reflexesresult from practice and learning and may involve overriding basic reflexes
repeated skill performance generates new synaptic patterns in the CNS which substitute for the natural reflex and the skill becomes automatic
e.g. somersaults in sports
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- JC3 (Neuroscience ) Flashcards on NS 10 - spinal reflexes, created by Erica Lai on 29/11/2018.
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- Erica Lai
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