Autonomic Nervous System

Question 1

How does the parasympathetic nervous system innervate the heart?

Answer 1

Vagus nerves travels via jugular foramen -> carotid -> carotid sheath -> superior throacic apeture -> Cardiac plexus.

Synapses in cardiac plexus.

Post-G fribres travel to SA and AV nodes.

Question 2

How does the sympathetic nervous system innervate the heart?

Answer 2

Pregang fibres (T1-6) -> cardiopulmonary splanchnic nerve -> cardiac ganglion = Synapse.

Postganglionic nerve travels to SA node, AV node and myocardium.

Increases cardioacceleratory centres and increases HR and contractllity

Question 3

What is the function of the parasympathetic nervous system on the heart?

Answer 3

Decreases the heart rate.

Question 4

What is the function of the sympathetic nervous system on the heart?

Answer 4

Increase HR and contractility

Question 5

What is the difference between a1 and a2 adrenoreceptors and target cell responses?

Answer 5

a1: Mechanism of action involves: Signal molecule activates receptor -> G-Prot activates PLC -> PLC increases DAG and IP3.

DAG activates PKC= phosphorylates prot, IP3 increases intracellular [Ca2+]

Leads to contraction of tissue.

a2: Mechanism of action: Signal molecule activates G-Prot -> Inhibits adenyl cyclase -> decreases the [cAMP].

May inhibit the release of noradrenalin or assist in platelet aggregation and vasoconstriction.

Question 6

What is the difference between b1 and b2 adrenoreceptors and target cell responses?

Answer 6

b1: Signal molecule binds to G-Prot. -> G-Prot activates adenyl cyclase -> converts ATP to cAMP -> cAMP activates protein kinase A -> protein kinase A activates oher proteins.

Increases HR and Contractility and sudomotion.

b2: G-Prot activates adenyl cyclase -> converts ATP to cAMP -> cAMP activates protein kinase A -> protein kinase A activates oher proteins.

Induces dilation