From the list of terms provided, fill in the blanks in the following text such t
ID: 56896 • Letter: F
Question
From the list of terms provided, fill in the blanks in the following text such that, upon completion, the passage correctly details the somatic segment of the motor branch of the peripheral nervous system and differentiates it from the autonomic segment.
Terms: acetylcholine, autonomic, cannot, involuntary, neuromuscular junction, NMJ, pre-ganglionic, post-ganglionic, skeletal, somatic, stimulatory, voluntary
Somatic neurons are efferent neurons that specifically innervate effectors under _____________ control - which primarily consists of ____________ muscle cells.
This contrasts the efferent neurons in the ______________ division of the peripheral nervous system, which innervate cardiac or smooth muscle cell or gland cell effectors - all of which are under the opposite - i.e. _________________ control.
The cell bodies of ______ motor neurons lie within and receive input from neurons of the CNS. However, their axons exit the CNS and travel to and synapse directly with their effector cells. In other words, single neuron (or single fiber) systems connect the CNS to skeletal muscle cells. In the autonomic division, the situation is different. Here, different than the 1, single fiber that lies between the CNS and the somatic motor neuron's effector, 2 neurons lie between the CNS and the involuntarily-controlled effectors. The first of these, called the _____________ fiber is like the somatic motor neuron in that its cell body lies within and receives signals from neurons of the CNS. However, it is different than the somatic motor neuron in that it does not synapse directly with the effector cell. Instead, it synapses with a second neuron, called the ______________ fiber, and it is this second nerve cell in the 'pathway' that actually synapses and communicates directly with the effector cells.
The junction between a somatic motor neuron and its effector cell is called the _________________, often abbreviated as the __________. All somatic motor neurons release the same signaling molecule (neurotransmitter) into this synapse - which is _____________. This neurotransmitter always has a ______________ effect on the effector cell - that means - it always promotes depolarization and subsequent contraction of the effector cell.
Effectors of somatic motor neurons are considered non myogenic - which means they _____________ spontaneously contract - rather, they need to be prompted, or stimulated by the somatic motor neuron to 'spur' their contraction. In the absence of release of the neurotransmitter from a somatic motor neuron, these non myogenic muscle cells remain relaxed.
Explanation / Answer
Somatic neurons are efferent neurons that specifically innervate effectors under voluntary control- which primarily consists of skeletal muscle cells.
This contrasts the efferent neurons in the autonomic division of the peripheral nervous system, which innervate cardiac or smooth muscle cell or gland cell effectors - all of which are under the opposite - i.e. involuntary control.
The cell bodies of somatic motor neurons lie within and receive input from neurons of the CNS. However, their axons exit the CNS and travel to and synapse directly with their effector cells. In other words, single neuron (or single fiber) systems connect the CNS to skeletal muscle cells. In the autonomic division, the situation is different. Here, different than the 1, single fiber that lies between the CNS and the somatic motor neuron's effector, 2 neurons lie between the CNS and the involuntarily-controlled effectors. The first of these, called the pre-ganglionic fiber is like the somatic motor neuron in that its cell body lies within and receives signals from neurons of the CNS. However, it is different than the somatic motor neuron in that it does not synapse directly with the effector cell. Instead, it synapses with a second neuron, called the post-ganglionic fiber, and it is this second nerve cell in the 'pathway' that actually synapses and communicates directly with the effector cells.
The junction between a somatic motor neuron and its effector cell is called the Neuromuscular junction, often abbreviated as the NMJ. All somatic motor neurons release the same signaling molecule (neurotransmitter) into this synapse - which is Acetylcholine. This neurotransmitter always has a stimulatory effect on the effector cell - that means - it always promotes depolarization and subsequent contraction of the effector cell.
Effectors of somatic motor neurons are considered non myogenic - which means they cannot spontaneously contract - rather, they need to be prompted, or stimulated by the somatic motor neuron to 'spur' their contraction. In the absence of release of the neurotransmitter from a somatic motor neuron, these non myogenic muscle cells remain relaxed.
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