Cardiac Physiology and Electrical System

Questions and Answers

What initiates the heartbeat and coordinates the contraction of the atria?

Bundle of His

Atrioventricular (AV) node

Sinoatrial (SA) node (correct)

Parasympathetic nervous system

How is cardiac output calculated?

Stroke Volume - Heart Rate

Stroke Volume / Heart Rate

Heart Rate × Stroke Volume (correct)

Heart Rate + Stroke Volume

What is the role of the atrioventricular (AV) node during heart contraction?

To generate electrical impulses

To delay the electrical signal (correct)

To initiate ventricular contraction

To regulate blood pressure

Which mechanism is involved in controlling blood pressure through blood vessel behavior?

Dilation and constriction Signup and view all the answers

What contributes to both heart rate and stroke volume in determining cardiac output?

Level of physical activity and nervous system signals Signup and view all the answers

What effect does vasodilation have on blood pressure?

It lowers blood pressure by decreasing resistance. Signup and view all the answers

What role do baroreceptors play in blood pressure regulation?

They send signals to the brain when blood pressure is too high. Signup and view all the answers

What initiates the formation of angiotensin II in the RAAS?

Release of renin from the kidneys. Signup and view all the answers

Which part of an ECG represents ventricular depolarization?

QRS complex Signup and view all the answers

How does the sympathetic nervous system affect blood pressure during stress?

It releases hormones that increase heart rate and blood pressure. Signup and view all the answers

Study Notes

Electrical System of the Heart

Heart rhythm is regulated by an electrical system starting at the sinoatrial (SA) node.
SA node is located in the right atrium and generates electrical impulses, causing simultaneous contraction of the atria.
After the atria contract, impulses move to the atrioventricular (AV) node which delays the signal to allow ventricular filling.
The bundle of His transmits the impulse to ventricles, prompting them to contract and pump blood.

Cardiac Output

Cardiac output refers to the volume of blood pumped by the heart per minute.
Determined by heart rate (beats per minute) and stroke volume (amount expelled with each beat).
Formula: Cardiac Output (CO) = Heart Rate × Stroke Volume.

Blood Pressure Control

Blood pressure is the force of blood against vessel walls, regulated through various mechanisms.
Vasoconstriction and Vasodilation: Blood vessels constrict or dilate, impacting resistance and blood pressure.
Baroreceptor Reflex: Baroreceptors detect blood pressure changes and send signals to adjust heart rate and vessel diameter.
Renin-Angiotensin-Aldosterone System (RAAS): Regulates blood pressure through hormone release from kidneys, promoting vasoconstriction and fluid retention.
Sympathetic and Parasympathetic Nervous System: Sympathetic activation increases heart rate and pressure, while parasympathetic activation decreases both.

Electrocardiogram (ECG)

ECG records heart's electrical activity, identifying heart rate, rhythm, and conduction abnormalities.
Key components include:
- P wave: Atrial depolarization
- QRS complex: Ventricular depolarization
- T wave: Ventricular repolarization.

Cardiac Diseases

Ischemic Heart Disease: Reduced blood flow to heart muscle due to blocked arteries, resulting in angina or heart attacks.
Arrhythmias: Disruptions in electrical conduction causing abnormal heart rhythms (tachycardia or bradycardia).
Valvular Heart Disease: Valve dysfunctions like stenosis or regurgitation affecting blood flow and heart workload.
Cardiomyopathies: Conditions affecting heart muscle structure and function; includes hypertrophic, dilated, and restrictive types.
Thrombosis and Embolism: Blood clot formation can block vessels; dislodged clots may travel, causing complications.

Nervous System Structure and Function

Central Nervous System (CNS): Comprises the brain and spinal cord; processes sensory data and coordinates motor commands.
Peripheral Nervous System (PNS): Encompasses all nervous tissue outside the CNS, delivering sensory information and motor commands.
Somatic Nervous System: Controls voluntary movements and processes sensory information.
Autonomic Nervous System (ANS): Manages involuntary functions such as heartbeat and digestion; divided into sympathetic (fight or flight) and parasympathetic (rest and digest).

Neurons and Glial Cells

Neurons transmit electrical and chemical signals; consist of cell body, dendrites, and axon.
Glial cells support neurons by providing structural support, insulation, and regulating the environment.

Neurological Alterations Leading to Disease

CNS Tumors:
- Primary tumors can be intracerebral (astrocytomas, oligodendrogliomas) or extracerebral (meningiomas).
- Secondary tumors originate from cancer in other body regions that spreads to the brain.
Nerve Injury and Regeneration:
- Most axons are myelinated for faster conduction; repair is possible in the PNS if injury is distal.
Demyelination: Chronic autoimmune diseases can cause demyelination in the CNS, affecting nerve function.

Description

Explore the intricacies of cardiac physiology and the electrical system that regulates the heart's rhythm. Understand how the sinoatrial node, atrioventricular node, and bundle of His work together to ensure coordinated heart contractions. Learn about normal contraction, cardiac output, and blood pressure control mechanisms in the vasculature.