Physiology Quiz: Heart Rhythm and Blood Pressure Regulation

Heart Rhythm and Regulation

• The rhythmic nature of the heart is determined by the anatomy of the sinus node.
• The ability of the heart to contract according to the "all or nothing" law and the presence of a long period of absolute refractoriness also influence heart rhythm.

Hormonal Response to Blood Loss

• The hormone considered as the "first line of defense" in reducing blood pressure caused by blood loss is adrenaline.
• Adrenaline helps to increase blood pressure and counteract the effects of blood loss.

Blood Pressure Regulation

• The main factor determining blood pressure is the work of the heart, which is influenced by blood circulation, venous return, hematocrit, vein tone, and other factors.

Blood Flow and Circulation

• Continuous blood flow in the vessels is maintained despite pulsatile systolic ejection due to the elasticity of the aorta and large arteries.
• The large mass of circulating blood, blood viscosity, and vascular resistance also contribute to maintaining blood flow.

Blood Vessels and Resistance

• Arterioles and venules are the resistive vessels that create the general resistance of the bloodstream.

Atrioventricular Conduction

• The atrioventricular delay in conduction of excitation ensures the correct coordination of contractions of the atria and ventricles.
• The atrioventricular delay allows for the transfer of excitation from the atria to the ventricles and ensures the functioning of the myocardium as a functional syncytium.

ECG Interpretation

• The presence of a P wave before the QRST complex on an ECG can be used to judge the correct location of the 1st order pacemaker.
• The duration of the RR intervals on an ECG reflects the time of one cardiac cycle.

Reflexes and Heart Rate

• The reflexes that change the work of the heart in the experiment are conjugated peripheral visceral cordial and intestinal reflexes.

Cardiomyocyte Function

• Cardiomyocytes derived from the sinus node are capable of generating automatic impulses.

Baroreceptors and Heart Rate

• An increase in pressure in the aortic arch or in the sinocarotid region causes inhibition of cardiac activity by reducing the frequency of impulses in the depressor and sinocarotid nerves.

Adrenaline Effects on the Heart

• Adrenaline causes tachycardia and increases contractions of the heart.

ECG Components

• The P-Q interval on an ECG reflects the time of excitation from the atria to the ventricles.
• The S wave on an ECG reflects conduction of excitation along the interventricular septum.

Ventricular Systole

• The duration of ventricular systole is typically 0.3-0.33 seconds.