Physiology of Heart and Circulatory System

These flashcards cover key concepts regarding the physiology of heart and circulatory systems, focusing on mechanisms of muscle contraction, regulation of heart rate, and gas exchange.

What regulates the pacemaker cells in the heart, and how do sympathetic and parasympathetic systems influence heart rate?

Sympathetic regulation increases heart rate through NE binding to B1 receptors, causing faster depolarization. Parasympathetic regulation decreases heart rate via ACh binding to muscarinic receptors, causing hyperpolarization.

How does calcium play a role in skeletal muscle contractions?

Calcium released from the SR binds to troponin, causing conformational changes that allow myosin to bind to actin, enabling the crossbridge cycle.

What are the sources of calcium for skeletal and cardiac muscle during contraction?

In skeletal muscle, calcium comes from the SR upon activation by an action potential. In cardiac muscle, calcium comes from both the extracellular space and the SR.

What triggers contraction in skeletal muscle?

Contraction is triggered by the depolarization of the motor neuron leading to the exocytosis of ACh, which initiates an action potential in the muscle.

What occurs during the crossbridge cycle?

During the crossbridge cycle, calcium binds to troponin, myosin heads attach to actin, undergo conformational changes, pivot to pull actin, then detach using ATP.

How does preload affect stroke volume?

Increased preload stretches cardiac muscle, enhancing contraction strength (Frank-Starling Law), which increases stroke volume.

What is atherosclerosis and how does it affect blood pressure?

Atherosclerosis is a disease with plaque buildup in arteries that narrows blood vessel diameter, increasing resistance and leading to higher blood pressure.

What drives changes in oxygen concentration during pulmonary and systemic circulation?

In pulmonary circulation, low O2 from the arteries diffuses into blood in the lungs, raising O2 levels. In systemic circulation, O2 from blood diffuses into tissues, lowering blood O2 levels.

Describe the mechanical changes during inhalation and exhalation.

Inhalation involves diaphragm contraction and intercostal muscle contraction, increasing thoracic volume and decreasing pressure. Exhalation involves relaxation of diaphragm and intercostal muscles, decreasing volume and increasing pressure.

What happens during the chloride shift?

The chloride shift transports CO2 in blood; bicarbonate exits RBCs as Cl- enters, maintaining electrical neutrality. In lungs, the reverse occurs: Cl- exits, bicarbonate enters, and CO2 is produced for exhalation.