USMLE Step 1 Physiology Review 54 07 Autonomic Nervous System (2 of 5)

USMLE Step 1 Physiology Review 54 07 Autonomic Nervous System (2 of 5)

 

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Play USMLE Audio MP3 54 07 Autonomic Nervous System (2 of 5) Below

Begin 54 07 Autonomic Nervous System (2 of 5) Transcription

Okay, now for some more questions about peripheral control of the autonomic nervous system.

In both the parasympathetic nervous and the sympathetic nervous system, how many neurons in series make the connection between the CNS and the effector organs.

  • Two.

What is the term of the neuron that originates in the central nervous system?

  •  Preganglionic.

In what structure does the preganglionic neuron synapse with the next neuron in the series?

  • In the peripheral autonomic ganglion.

What is the term of the next neuron in the series, the one in the preganglionic neuron synapses with?

  • The postganglionic neuron.

So in both systems the parasympathetic and sympathetic, two neurons, the preganglionic and postganglionic, that are connected in series carry efferent, with an “e” efferent information from the CNS to the end organ.

Which neuron directly innervates the effector organ?

  • The postganglionic.

In the somatic system how many neurons in series are necessary to make the connection between CNS and the effector organ, i.e. skeletal muscle

  • One.

Student Doctor, please pause the tape and summarize the information discussed this far on the peripheral control of the autonomic nervous system.

  • In both the parasympathetic nervous and sympathetic nervous system, two neurons in series make the connection between the CNS and the effector organ. Preganglionic neuron originates in the central nervous system. The preganglionic neuron synapses with the next neuron in the series in the peripheral autonomic ganglion. This next neuron in the series, the one that the preganglionic neuron synapses with, is the postganglionic neuron. So in both systems the parasympathetic and sympathetic two neurons, the preganglionic and postganglionic that are connected in series carry efferent information from the CNS to the end organ. The postganglionic neuron directly innervates the effector organ. In the somatic system only one neuron is necessary to make the connection between the CNS and the effector organ, that is skeletal muscle.

Alright, let’s do some more questions about the peripheral control of the autonomic nervous system.

What is another term for the parasympathetic nervous system?

  • The cranio-sacral division of the ANS.

What does the cranio part of the cranio-sacral refer to?

  • The term cranio describes the parasympathetic outflow originating in preganglionic cell bodies in the midbrain and medulla.

Which four cranial nerves do the preganglionic cell bodies give rise to?  List them in numeric order along with their name. Please pause the tape.

  • First, third nerve, or Occulomotor.  Second, seventh nerve, Facial.  Third ninth nerve, Glossopharyngeal.  Fourth, tenth nerve, Vagus.

Which one of these nerves is most important in terms of life function?

  • The tenth nerve, or Vagus nerve.

What does the sacral part of cranio-sacral refer to? Please pause the tape.

  • The term sacral refers to parasympathetic outflow originating from the preganglionic cell bodies and spinal cord segments S2 to S4.

hich had the longer axons, preganglionic or postganglionic parasympathetic neurons?

  •  Preganglionic.

Student Doctor, please pause the tape and summarize the information on the peripheral control of the autonomic nervous system discussed since the last summary. The first question asked for another term for the parasympathetic nervous system.

  • Another term for the parasympathetic nervous system is the cranio-sacral division of the ANS. The cranio part of cranio-sacral refers to the parasympathetic outflow originating in preganglionic cell bodies in the midbrain and the medulla. These preganglionic cell bodies give rise to the third nerve, or Occulomotor, the seventh nerve, or Facial nerve, the ninth nerve, or Glossopharyngeal nerve, and the tenth nerve, or the Vagus nerve.  The tenth nerve, the Vagus nerve, is the most important in terms of life function.  The sacral part of cranio-sacral refers to parasympathetic outflow originating from the preganglionic cell bodies and spinal cord segments S2 to S4.  Among parasympathetic neurons, preganglionic axons are longer than the postganglionic axons.

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