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30 Cards in this Set
- Front
- Back
motor unit
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motor unit and all the muscle cells it services, basic functional unit of the muscle
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neurons and muscle cells are electrically activated by
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changing their electrical charges
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NT
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chemicals released by a neuron which cause excitation, facilitation, or inhibition
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neuron activations are
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waves of depolarization caused by Na+ influx
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chemical gates
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least numerous, found in nerve cell body and dendrites, and muscles at nerve synapse; unlocked by NT
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electrical gates
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most numerous, found in neuronal axons, found distal to synapses in muscle cells, open when resting membrane potential exceeds threshold
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the opening of electrical gates that causes
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necessary level of depolarization called AP
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the nerve impulse must _______ before another impulse can be sent down an axon
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repolarize
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repolarization requires
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energy ATP to repolarize
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the Na, K pump requires
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ATP for pump
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facilitation
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raising the resting potential above the normal potential, increasing likelihood that NT release cause exceeding threshold
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inhibition
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lowering resting potential below normal potential, decreasing likelihood of reaching potential
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most common excitatory and facilitory NT
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Norepi and Acetylcholine
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most common inhibitory NT
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GABA
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spatial summation
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NT release from more than one neuron is necessary to cause excitation
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temporal summation
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altering frequency of a nerve firing, to ensure sufficient amounts to cause depolarization
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rate coding
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temporal summation occurs in skeletal muscles
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tetanus
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muscle achieve maximal temporal summation
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safety net for muscle groups
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inhibition for muscle groups
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can't be overstimulated to perform
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fine motor skills
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nerve failure
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When a nerve fails to activate its target through some mechanism other than inhibition.
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fatigue.
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When the nerve fails to activate a muscle then the condition is generally referred to
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3 main causes of nerve failure (neuronal based fatigue)
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neuron don't repolarize; neuron don't release NT; Branch Point Failure
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1. Neuron does not repolarize
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Repolarization requires an active Na-K pump. The Na-K pump needs energy (ATP) to operate. Therefore, if the ATP is “used up", the neuron can not repolarize and hence fails
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Neuron does not repolarize; identified by
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finding high post-exercise serum potassium levels
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when neuron don't repolarize
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condition usually will occur with high stimulation frequencies or rapid temporal summation
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2. Neuron does not release neurotransmitter.
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Neurotransmitter is made and stored in packets in the synaptic end bulb. If neurotransmitter release occurs faster than the rate at which it is being made, the neuron will eventually "run out" of neurotransmitter. With no transmitter, even if the neuron depolarizes, the target will not be activated.
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how will neuron not releasing NT will occur
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with high stimulation frequencies or rapid temporal summation; (not releasing NT)
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3. Branch Point Failure
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Most neuronal axons have branches of varying lengths (esp. motor neurons). When a neuron is being stimulated at high frequencies, some of the longer branches can not repolarize as fast as the rest of the axon. Thus when the neuron is activated again, some of the branches can't depolarize because they have not repolarized yet.
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all 3 nerve failures occur with
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(all 3) high stimualtion frequencies or rapid temporal summation
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