Chapter 11 - ANS

The parasympathetic nervous system always promotes muscle relaxation, and the sympathetic nervous system always promotes muscle contraction.

• True

• False

Answer explanation

The parasympathetic nervous system and sympathetic nervous system BOTH promote muscle contraction AND relaxation, depending on the muscle. For example, the parasympathetic nervous system can contract the inner circular muscles of our eyes. The sympathetic nervous system can relax the smooth muscles in our bronchioles.

Pupil dilation and constriction is an example of a(n) ________________________ effect.

Answer explanation

Antagonistic effects oppose each other. Our parasympathetic nervous system and sympathetic nervous system can have opposing/opposite effects, such as pupil constriction vs pupil dilation.

The neurotransmitter secreted by the preganglionic neurons of the sympathetic division is:

• ACh

• NE

• E

• Dopamine

Answer explanation

All preganglionic neurons secrete ACh.

Postganglionic neurons differ depending on the branch of the ANS we are working with, but preganglionic neurons will always secrete the same NT.

Which of the following is a primary function of the sympathetic nervous system?

• Decreasing heart rate

• Stimulating digestive activities

• Increasing heart rate and blood pressure

• Constricting pupils

Postganglionic neurons of the sympathetic nervous system secrete _______ 80% of the time.

• ACh

• NE

• E

• Dopamine

Answer explanation

Sympathetic postganglionic neurons can secrete E, and even ACh at sweat glands. However, it releases NE the most (80% of the time).

What NT do Muscarinic-1 Receptors respond to?

Answer explanation

Muscarinic-1 Receptors are for the parasympathetic nervous system. The parasympathetic nervous system only secretes ACh, so all of its receptors will only respond to ACh.

Which receptor is involved in lowering the heart rate?

• M-1

• M-2

• B-2

• a-1

Answer explanation

Because we are lowering HR, we know that we are dealing with the parasympathetic nervous system. This means that we are dealing with Muscarinic Cholinergic Receptors. M-2 receptors are inhibitory, and prevent cardiac muscle contraction. This will lower our HR :)

alpha-1 adrenergic receptors use which 2nd messenger system to cause a depolarization in smooth muscle?

• Phosphatidylinositol 2nd Messenger System

• cAMP

  2nd Messenger System

• cGMP

  2nd Messenger System

• Trick question: They don't use any 2nd messenger system

Answer explanation

alpha-1 receptors will use the Phosphatidylinositol 2nd messenger system. IP3 will trigger calcium release from the Smooth ER, and DAG will activate protein kinase C and cause phosphorylation.

Compared to norepinephrine, epinephrine has a greater affinity for what type of receptor?

• a-1

• Muscarinic

• B-2

• B-1

Answer explanation

B-2 receptors respond best to E. One way to remember this is to think of EpiPens. If someone is having an allergic reaction, they can take E to increase bronchodilation (which is a response caused by B-2 receptors) and help them breathe.

Which receptor is involved in raising HR?

• M-1

• B-1

• a-2

• B-3

Answer explanation

Because we are increasing HR, we know that we are dealing with the sympathetic nervous system. This means that it won't be M-1. We also know that we are dealing with muscle contraction and excitation, so it can't be a-2. We don't really talk about B-3, but that's involved with lipolysis.

Tip:

B-1 = 1 Heart -> Increases HR

B-2 = 2 Lungs -> Bronchodilation