Not very many autonomic nervous system questions, but there are a few. As I know many of you are focusing on membrane excitability for now that is understandable. If they happen to come up throughout the week in your studies, however, please feel free to add the questions below in the comments section and we can work through them together there!
Here are your questions:
1. Ok,
so on question 11:
11. Which of the following is a feature of the
sympathetic, but not the parasympathetic, nervous system?
A. Ganglia located in the effector organs
B.
Long preganglionic neurons
C.
Preganglionic neurons release norepinephrine
D.
Preganglionic neurons release acetylcholine (ACh)
E.
Preganglionic neurons originate in the thoracolumbar spinal cord
F.
Postganglionic neurons synapse on effector organs
G.
Postganglionic neurons release epinephrine
H.
Postganglionic neurons release ACh
I
picked G, but the right answer is E. Do parasympathetic nerves release Epi
somewhere? I guess they do if that's not the right answer! So where?
Question 11 is: Which of the following is
a feature of the sympathetic, but not the parasympathetic, nervous
system? Could E and G be correct. Originating from the
thoracolumnar spinal cord and release of epinephrine?
Yes, the sympathetic nervous system does release epinephrine, but that is not the MAIN neurotransmitter released from that system. Remember that the chromaffin cells release approximately 80% epinephrine and approximately 20% norepinephrine while the majority of the postganglionic neurons in the sympathetic nervous system release approximately 80% norepinephrine and approximately 20% epinephrine. Therefore E is a better answer than G, but to make entirely not correct the answer choice SHOULD say Postganglionic neurons primarily release epinephrine (or something to that effect).
2. Question 1 is
A
person is taking a drug that causes, among other things, dryness of the mouth
and speeding of the heart rate but no
impairment of the ability to use the skeletal muscles. What type of
receptor does this drug probably block? Why is the answer Muscarinic Ach receptor. There would be impairment to the skeletal muscles if it was blocked. Wouldn't it be B1 dealing with salivation and heart?
The symptoms of the drug are an increase in the sympathetic nervous system (dryness of mouth and increased heart rate). Therefore the drug needs to be increasing the sympathetic stimulation or blocking (as the question asks) the parasympathetic stimulation. As the parasympathetic nervous system is typically on at rest, blocking the nicotinic ACh receptors (which would block stimulation to both systems) would cause the phenotype to look like activation of the sympathetic nervous system. In this case, however, you know that the skeletal muscles (which are also activated by the nicotinic ACh) receptors are unaffected, therefore you know that it must be a blockage of the parasympathetic system and specifically the muscarinic ACh receptor. Yes, you are dealing with the B1 receptor, but you are ACTIVATING it not blocking it.
3. Also, does epi bind to the same Adrenergic receptors as norepi? They do the same thing it seams like, so i am somewhat confused when it is Epi or norepi being released.
Epi and NE do bind to the same Adrenergic receptors but their affinities for different types vary. Those affinities you do not need to worry much about for this lecture. What is important is where they are released primarily (Epi primarily released by Chromaffin cells and NE primarily released by other post-synaptic neurons of the sympathetic NS), and what receptors they do bind to. The details of the cellular signalling cascades of their activation of the Adrenergic receptors was covered by Dr. Meisenberg.
Hello Dr. J,
ReplyDeleteClarification needed in lec notes. In the Spinal Cord and Autonomics PowerPoint, the parasympathetic/sympathetic image used on slides 22-23 shows that Sympathetic system inhibit salivation.
In the past, I studied that BOTH parasympathetic/sympathetic INCREASE salivation. This is also the case in slide 28 of the same lecture.
Please let us know your stance on this. Thank you.
That's a GREAT CATCH from the text book picture! In fact you are right in what you have studied in the past, BOTH parasympathetic and sympathetic increase salivation, it is just the type of salivation that they increase. Sympathetic, which essentially wants to shut down GI activity, stimulates a thick mucus-like saliva release while Parasympathetic, which stimulates GI activity, stimulates the release of a watery saliva that helps lubricate the entire system. The indication that the sympathetic system inhibits salivation is not entirely correct in the picture.
DeleteI was wondering if you could explain why CTL question #1 of the ANS has "E" as the answer. I know Ach is the NT released at the ganglia and there is an alpha or beta receptor at the target organ. But I thought you told us the pre-ganglionic neuron would be short and unmyelinated and the post-ganglionic neuron would be long and myelinated for sympathetic, but maybe I'm confused because this doesn't appear to be an option. Could you explain why option E is correct?
ReplyDeleteI do not have the CTL questions in front of me so could you remind me what the question is asking? I will say, however that Ach never binds to either alpha or beta adrenergic receptors only to nicotinic or muscarinic receptors.
ReplyDeleteI had the same question regarding the CTL #1 question:
ReplyDeleteWhich of the following answer choices best describes the efferent neurons of the sympathetic nervous system?
Pre-ganglionic Neuron Post-ganglionic neuron NT released at ganglia Receptor at target organ
A Short and myelinated Long and myelinated Ach alpha or beta
B Long and myelinated Short and unmyelinated NE or E muscarinic
C Short and unmyelinated Long and unmyelinated Ach nicotinic
D Long and myelinated Long and unmyelinated NE or E muscarinic
E Short and myelinated Long and unmyelinated Ach alpha or beta
The answer was E but how do we go about choosing E over A?
It is my understanding that actually neither E nor A are correct. Preganglionic neurons from the SNS are mostly short and unmyelinated (although some are myelinated). Postganglionic neurons are much longer and typically myelinated. Therefore this question is not fully accurate and I would state that of the answer choices, A is more accurately a correct answer choice. I apologize that this question is still available to you with what I believe as incorrect information. Dr. Yin, however, could probably provide some further insight onto this subject for further clarification.
Delete