Heart rate is the speed of the heartbeat typically expressed as beats per minute (bpm). The heart rate can vary depending on the body’s physical needs including the need to pump more blood when exercising. Heart rate is usually regulated by the autonomic nervous system which controls involuntary actions of the body such as heart rate digestion and respiration. The autonomic nervous system has two divisions the sympathetic nervous system and the parasympathetic nervous system which work together to regulate heart rate.
The sympathetic nervous system is responsible for the “fight or flight” response which increases heart rate and blood pressure in response to a perceived threat. The parasympathetic nervous system has the opposite effect and slows heart rate and decreases blood pressure. These two systems work together to maintain a balance and to keep heart rate within a normal range.
There are several factors that can influence which division of the autonomic nervous system is dominant at any given time. One of the most important factors is the level of stress hormones such as adrenaline in the body. When the body is under stress the sympathetic nervous system is activated and heart rate increases. Other factors that can influence heart rate include exercise temperature and emotions.
Heart rate can also be affected by certain medications such as beta blockers which are used to treat high blood pressure and heart conditions. Beta blockers work by blocking the effects of adrenaline which can help to slow the heart rate.
What is the SA node?
The SA node is the natural pacemaker of the heart.
What is the function of the SA node?
The SA node is responsible for the generation and propagation of electrical impulses in the heart.
What is the function of the AV node?
The AV node is responsible for conducting electrical impulses from the atria to the ventricles.
What is the function of the His-Purkinje system?
The His-Purkinje system is responsible for conducting electrical impulses from the ventricles to the muscles of the heart.
How does the SA node generate electrical impulses?
The SA node generates electrical impulses by depolarizing and then repolarizing.
How does the AV node conduct electrical impulses?
The AV node conducts electrical impulses by depolarizing and then repolarizing.
How does the His-Purkinje system conduct electrical impulses?
The His-Purkinje system conducts electrical impulses by depolarizing and then repolarizing.
What is the mechanism of depolarization?
Depolarization is caused by the opening of voltage-gated ion channels in the cell membrane.
What is the mechanism of repolarization?
Repolarization is caused by the closing of voltage-gated ion channels in the cell membrane.
What is the role of sodium ions in depolarization?
Sodium ions play a role in depolarization by moving into the cell during depolarization.
What is the role of potassium ions in repolarization?
Potassium ions play a role in repolarization by moving out of the cell during repolarization.
What is the role of calcium ions in depolarization?
Calcium ions play a role in depolarization by moving into the cell during depolarization.
What is the role of calcium ions in repolarization?
Calcium ions play a role in repolarization by moving out of the cell during repolarization.
What is the role of ATP in depolarization?
ATP plays a role in depolarization by providing energy for the opening of voltage-gated ion channels.
What is the role of ATP in repolarization?
ATP plays a role in repolarization by providing energy for the closing of voltage-gated ion channels.
