ANS Innovation Of The Heart

Question 1

What are the 2 branches of the ANS?

Extra point - What is the debatable 3rd branch

Answer 1

Sympathetic and parasympathetic

Extra point - Enteric nervous system.

Question 2

What is the origin of the sympathetic nerves?

Answer 2

Thoracolumnar origin. Segments T1 to L2/L3

Question 3

What is the origin of the parasympathetic nerves?

Answer 3

Craniosacral - cranial nerves 3, 7, 9 and 10. Sacral nerves S2 - S4

Question 4

What is the neurotransmitter in post ganglionic fibres of the sympathetic ANS?

Answer 4

Noradrenaline. Except for sweat glands which have Acetylcholine.

Question 5

What is the neurotransmitter in the post ganglionic fibres of the parasympathetic ANS?

Answer 5

Acetylcholine

Question 6

What are Chromaffin cells?

Answer 6

Specialised post ganglionic cells which are found in the adrenal glands.

Question 7

What do Chromaffin cells do?

Answer 7

Release noradrenaline directly into the blood stream.

Question 8

What are the 2 types and 4 subtypes of adrenoreceptors?

Answer 8

Alpha - 1 and 2

Beta - 1 and 2

Question 9

Why do tissues have different subtypes of adrenoreceptors?

Answer 9

It allows diversity of action.

Can be exploited with selectivity of drugs for desired effect

Question 10

What are adrenoreceptors ?

Answer 10

G protein coupled receptors with no ion channels. They receive adrenaline/noradrenaline.

Question 11

Which branch of the ANS increases under stressful situations?

Answer 11

The sympathetic branch.

Question 12

Which branch of the ANS increases after you have eaten?

Answer 12

The parasympathetic.

Question 13

What does acetylcholine do to the heart?

Answer 13

Act on M2 receptors which decrease heart rate.

Question 14

Where do the post ganglionic fibres of the parasympathetic ANS sit on the heart?

Answer 14

Epicardial surface or within the walls of the heart.

Question 15

What does the sympathetic ANS do to the heart?

Answer 15

Innervates the sino atrial and atrial ventricular nodes as well as the myocardium.

Question 16

What effect does noradrenaline have one heart?

Answer 16

Acts on beta 1 adrenoreceptors so increases the heart rate and force of contraction.

Question 17

How does the pacemaker of the heart work?

Answer 17

The cells within the sino atrial node steadily depolarise toward the threshold until it meet them then an action potential is fired. This is called the pacemaker potential - turning on of slow Na+ conductance and opening of Ca2+ channels.

Question 18

What is the action of the sympathetic ANS on the pacemaker potential?

Answer 18

Increases the slope on the graph. This is due to it effecting the beta 1 receptors and increasing cAMP.
Protein kinase causes phosphorylation of Ca2+ channels and and increase in Ca2+ entry during an action potential.
This increases the force of contraction.

Question 19

What is the action of the parasympathetic ANS on the pacemaker potential?

Answer 19

Decreases the slope on the graph. Uses M2 receptors.

Increases K+ conductance and decreases cAMP.

Question 20

Which branch of the ANS do most blood vessels receive their innovation from?

Answer 20

The sympathetic. Except specialised tissue eg erectile tissue which receives parasympathetic.

Question 21

What type of adrenoreceptor does most arteries and veins have?

Answer 21

Alpha 1

Question 22

Arteries and veins in which 3 extra tissue types have beta 2 adrenoreceptors?

Answer 22

Liver, skeletal and coronary. Adrenaline has a higher affinity for Beta 2 adrenoreceptors.

Question 23

What is vasomotor tone?

Answer 23

The normal output of a vessel.

Question 24

What is it called when the output of a vessel increases?

Answer 24

Vasoconstriction.

Question 25

What is it called when the output of a vessel decreases?

Answer 25

Vasodilation.

Question 26

How does vasodilation occur?

Answer 26

Activation of the beta 2 adrenoreceptors causes vasodilation by an increase in cAMP that opens the K+ channels so the smooth muscle relaxes.

Question 27

How does vasoconstriction occur?

Answer 27

Alpha 1 adrenoreceptors are activated. | Increase the concentration of Ca2+ entering the cell so there is contraction of smooth muscle.

Question 28

What effect does metabolites have on vasomotor tone?

Answer 28

They have a strong vasodilatior effect.

Question 29

What are baroreceptors?

Answer 29

Nerve endings in the carotid sinus and aortic arch that are sensitive to stretch.

Question 30

How do baroreceptors work?

Answer 30

When they are stretch due to an increased arterial pressure they feedback to the medulla which adjusts the efferent pathway. (The heart and vessels)

Question 31

What are the 3 classes of drugs which effect the ANS?

Answer 31

1) Sympathonimetrics 2) Adrenoreceptor antagonists 3) cholinergics

Question 32

What are the 2 types of Sympathonimetrics?

Answer 32

Alpha adrenoreceptor agonists. | Beta adrenoreceptor agonists.

Question 33

What are the 2 types of cholinergics?

Answer 33

Muscarinic agonists and antagonists.

Question 34

What is an example of how muscarinic agonists are used in clinical practice?

Answer 34

Treatment of a glucoma using Pilocapine.

Question 35

What is an example of how muscularinic antagonists are used in clinical practice?

Answer 35

Tropicqmide is used to dilate the pupils for examination of the eye.

Question 36

What is a cardiovascular use for Sympathonimetrics?

Answer 36

Adrenaline is used to restore function during a cardiac arrest. OR A beta agonist - Dobutamine - used in cardiogenic shock.

Question 37

What is a clinical use for adrenoreceptor antagonists?

Answer 37

Alpha 1 antagonists eg Prazosin are hypertensive agents. Can be used as an anti hypertensive agent which inhibits the noradrenaline action on vascular smooth muscle causing vasodilation. Beta adrenoreceptor antagonists eg Propranolol. Can be used to slow heart rate and reduce the force of contraction. Non selective with beta 1/2.

Question 38

Why is Atenolol sometimes used instead of propranolol?

Answer 38

Because Atenolol is selective for beta 1 which means there is less risk of bronchoconstriction in the patient. - This can be especially dangerous for people with asthma.