USMLE Step 1 Physiology Review 54 09 Autonomic Nervous System (4 of 5)

USMLE Step 1 Physiology Review 54 09 Autonomic Nervous System (4 of 5)

 

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Begin 54 09 Autonomic Nervous System (4 of 5) Transcription

Now for some questions on the physiology of the autonomic nervous system.

Which system, parasympathetic or sympathetic is involved in the maintenance, conservation and protection of bodily resources and energy stores, or rather anabolic action?

  • Parasympathetic.

What kinds of end organs do parasympathetic neurons excite?

  • Parasympathetic neurons excite organs responsible for absorbing food.

Parasympathetic neurons reduce the activity of other kinds of organs. What kinds of organs have their activity reduced by parasympathetic neurons?

  • Parasympathetic neurons reduce the activity of organs that expend a lot of energy. For example, parasympathetic neurons can reduce heart rate.

How is the sympathetic system involved with bodily resources or energy?

  • The sympathetic system is involved with the expenditure of bodily resources, in other words it is involved with catabolic action.

The activation of which system, parasympathetic or sympathetic, supports the fight or flight response?

  • The sympathetic.

Which neuron transmitter is released with the activation of the sympathetic neuron system in the fight or flight response?

  • Epinephrine.

From where is epinephrine released? That is, from what structure, gland or organ?

  • Epinephrine is released from the adrenal medulla.

Student Doctor, please pause the tape and summarize the information discussed this far on the physiology of the autonomic nervous system. The first question was about how the parasympathetic nervous system was involved in the conservation of bodily resources.

  • The  parasympathetic nervous system is involved in the maintenance, conservation and protections of bodily resources and energy stores. In other words, it is involved in anabolic action. The Parasympathetic neurons excite organs responsible for absorbing food. Parasympathetic neurons reduce the activity of organs that expend a lot of energy.  For example, parasympathetic neurons can reduce heart rate.  The sympathetic nervous system is involved with the expenditure of bodily resources.  In other words, it is involved with catabolic action. The activation of the sympathetic nervous system supports the fight or flight response. Epinephrine is released with activation of the sympathetic nervous system in the fight or flight response.  Epinephrine is released from the adrenal medulla.

And now for some more questions.

In many organs the sympathetic and parasympathetic nervous systems have opposing effects.  Therefore, they must work in concert.

What is the term for this process where the parasympathetic and sympathetic nervous systems work in concert?

  • Functional synergism.

Another key concept in the physiology in the ANS is tone.

What does tone describe?

  • Tone is the basal outflow from either the sympathetic or parasympathetic nervous system.

If the inhibitory influence on an organ, let’s say the heart, is removed, what kind of response would the ANS produce on the heart?

  • Heart rate would increase to basal levels.

Because of tone, innervation by both parasympathetic and sympathetic nervous systems is not always necessary.

Student Doctor, please pause the tape and summarize the information on the physiology of the autonomic nervous system discussed since the last summary. The first question was about functional synergism.

In many organs the sympathetic and parasympathetic nervous systems have opposing effects.  Therefore, they must work in concert in a process called functional synergy.  Another key concept in the physiology of the ANS is tone.  Tone is the basal outflow from either the sympathetic or the parasympathetic nervous system.  If the inhibitory influence on an organ, let’s say the heart, is removed heart rate will increase to basal levels. Because of tone, innervation by both parasympathetic and sympathetic nervous systems is not always necessary.

****END OF TRANSCRIPTION****

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