Conducting system of the heart

Control of coordination an timing Where does the heart beat originates from? The heart itself How is it regulated? By both the nervous and hormonal control.

Watch the video from 15min onwards n5KdjM n5KdjM What are the name and position of the 2 nodes?

Sino-atrial node

Sino-Atrial Node (SAN) is located in the upper part of the wall of the right atrium.

Sino-atrial node Atrio ventricular node

Sino-Atrial Node (SAN) is located in the upper part of the wall of the right atrium. Atrio-Ventricular Node (AVN) is located near the base of the atria.

What is special about the cells in the SAN? They are auto-rhythmic cells exhibiting spontaneous excitation. What is the function of the cells in the SAN? Pacemaker: They set the rate at which cardiac muscle cells contract. How is the timing of cardiac cells achieved to produced a coordinated action?

The timing is controlled by the impulse from the SAN spreading through the atria and then travelling to the atrio-ventricular node (AVN). The AVN in turn sends out impulses into a bundle of conducting fibres which cause the ventricles to contract

What is generated by these impulse that can be picked up by a machine? Electrical current What is the name of given to lines which represent the electrical activity over the heart? An electrocardiogram (ECG)

Regulation of heart rate How can the pacemaker (SAN) respond to situations if it can set the rate on its own? It is connected to part of the brain called the medulla.

The autonomic nervous system (ANS) = part of the nervous system which regulates the internal environment by controlling: The heart Blood vessels Bronchioles Alimentary canal. This control is in general involuntary because it normally works automatically without the person’s conscious control.

Regulation of heart rate How can the pacemaker (SAN) respond to situations if it able to set the rate on its own? It is connected to part of the brain called the medulla. What is the autonomic nervous system (ANS)? It is the part of the nervous system which regulates the internal environment by controlling structures and organs such as the heart, blood vessels, bronchioles and alimentary canal. This control is in general involuntary because it normally works automatically without the person’s conscious control. Slide of nervous system organisation What two systems are Sympathetic system (prepares the body for action) Parasympathetic system (calm body down returning it to normal state) How can the difference in action of the 2 systems be described? Antagonistic How does the medulla regulate the rate of the SAN? Through the antagonistic action of the autonomic nervous system What is the effect of sympathetic nerves on heart rate? Sympathetic accelerator nerves release noradrenaline (nor-epinephrine) causing an increase in heart rate. What is the effect of parasympathetic nerves on heart rate? They release acetylcholine causing a decrease in heart rate. Under which circumstances and how can hormones affect heart change? Circumstances such as stress or exercise the sympathetic nervous system causes the adrenal glands to release adrenaline (epinephrine) which results in an increase in heart rate.

Regulation of heart rate How can the pacemaker (SAN) respond to situations if it able to set the rate on its own? It is connected to part of the brain called the medulla. What is the autonomic nervous system (ANS)? It is the part of the nervous system which regulates the internal environment by controlling structures and organs such as the heart, blood vessels, bronchioles and alimentary canal. This control is in general involuntary because it normally works automatically without the person’s conscious control. Slide of nervous system organisation What two systems are Sympathetic system (prepares the body for action) Parasympathetic system (calm body down returning it to normal state) How can the difference in action of the 2 systems be described? Antagonistic How does the medulla regulate the rate of the SAN? Through the antagonistic action of the autonomic nervous system What is the effect of sympathetic nerves on heart rate? Sympathetic accelerator nerves release noradrenaline (nor-epinephrine) causing an increase in heart rate. What is the effect of parasympathetic nerves on heart rate? They release acetylcholine causing a decrease in heart rate. Under which circumstances and how can hormones affect heart change? Circumstances such as stress or exercise the sympathetic nervous system causes the adrenal glands to release adrenaline (epinephrine) which results in an increase in heart rate.

Regulation of heart rate How can the pacemaker (SAN) respond to situations if it able to set the rate on its own? It is connected to part of the brain called the medulla. What is the autonomic nervous system (ANS)? It is the part of the nervous system which regulates the internal environment by controlling structures and organs such as the heart, blood vessels, bronchioles and alimentary canal. This control is in general involuntary because it normally works automatically without the person’s conscious control. Slide of nervous system organisation What two systems are Sympathetic system (prepares the body for action) Parasympathetic system (calm body down returning it to normal state) How can the difference in action of the 2 systems be described? Antagonistic How does the medulla regulate the rate of the SAN? Through the antagonistic action of the autonomic nervous system What is the effect of sympathetic nerves on heart rate? Sympathetic accelerator nerves release noradrenaline (nor-epinephrine) causing an increase in heart rate. What is the effect of parasympathetic nerves on heart rate? They release acetylcholine causing a decrease in heart rate. Under which circumstances and how can hormones affect heart change? Circumstances such as stress or exercise the sympathetic nervous system causes the adrenal glands to release adrenaline (epinephrine) which results in an increase in heart rate.

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