Cardiac Physiology and Electrical System

Study Notes

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 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 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.

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.

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.

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 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.

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.