Extrinsic Control of the Heart

Flashcards covering key concepts related to the extrinsic control of the heart from the lecture notes.

What are the two main components of the autonomic nervous system that control heart rate?

The parasympathetic system and sympathetic system.

What neurotransmitter is primarily associated with the parasympathetic system in heart control?

Acetylcholine (ACh).

What type of receptors does ACh act on in the parasympathetic system?

Cholinergic receptors, specifically nicotinic and muscarinic receptors.

What effect does ACh have at muscarinic receptors in the heart?

It causes the opening of K+ channels, leading to hyperpolarization.

What is the normal threshold potential for the SA node action potentials?

-60mV.

What effect does the sympathetic system have on heart rate?

It increases heart rate.

Which type of adrenergic receptors are primarily found on cardiac muscle cells?

Beta-1 (β1) receptors.

What is the effect of noradrenaline binding to beta-1 receptors on cardiac muscle?

It causes increased inflow of Na+ ions, resulting in a stronger contraction.

How does the parasympathetic system affect the conduction delay at the AV node?

It increases the conduction delay, reducing heart rate.

What is the role of the adrenal medulla in heart activity?

It releases hormones like noradrenaline and adrenaline that increase heart rate and stroke volume.

How does the sympathetic system affect the strength of contraction in the heart?

It increases the force of contraction, thus increasing stroke volume.

What happens to the heart rate at rest in the absence of extrinsic influences?

Without extrinsic influences, the heart rate is about 100 bpm, which is slowed down by the parasympathetic system.