Heart Function and Nervous System

Dr. Marc explains how the nervous system controls heart rate and contraction through the sympathetic and parasympathetic divisions. The sympathetic system, associated with fight-or-flight responses, increases heart rate and contractility via the cardioacceleratory center in the medulla. It sends signals through the spinal cord to the heart, affecting the SA and AV nodes and myocardium. The parasympathetic system, linked to rest and digest, decreases heart rate through the cardioinhibitory center, using the vagus nerve to release acetylcholine, which hyperpolarizes nodal cells, making it harder for the heart to contract.

What is the primary role of the sympathetic nervous system in relation to heart function?

• To decrease heart rate and contractility

• To increase heart rate and contractility

• To maintain a constant heart rate

• To regulate blood pressure

Where does the sympathetic innervation for the heart begin?

• In the paravertebral ganglia

• At the cardioacceleratory center in the medulla

• In the spinal cord

• In the cerebrum

What is the function of the SA node in the heart?

• To contract the ventricles

• To set the rhythm of the heart

• To regulate blood flow

• To slow down the heart rate

How does noradrenaline affect the heart's nodal cells?

• It inhibits beta-1 receptors

• It increases sodium and calcium entry

• It releases potassium from the cells

• It decreases sodium and calcium entry

What is the role of beta-1 receptors in the heart?

• To inhibit calcium entry

• To release acetylcholine

• To increase heart rate and contractility

• To decrease heart rate

Which neurotransmitter is released by the parasympathetic nervous system to slow down the heart?

• Serotonin

• Acetylcholine

• Dopamine

• Noradrenaline

What is the effect of acetylcholine on the heart's nodal cells?

• It inhibits beta-1 receptors

• It decreases calcium entry

• It increases sodium entry

• It increases potassium exit

How does the vagus nerve affect heart rate?

• It increases heart rate

• It regulates blood pressure

• It maintains a constant heart rate

• It decreases heart rate

What is the primary function of the cardioinhibitory center?

• To increase heart rate

• To decrease heart rate

• To regulate blood pressure

• To contract the ventricles

Which part of the brain is involved in both sympathetic and parasympathetic control of the heart?

• Cerebrum

• Cerebellum

• Medulla

• Thalamus