Mechanical Activity of the Myocardium

<p>It contributes to internal energy loss (D)</p> Signup and view all the answers

<p>There is a direct interplay between VR and CO that is essential for heart function. (B)</p> Signup and view all the answers

<p>The potential to do work is load dependent (D)</p> Signup and view all the answers

<p>Oxygen availability (C)</p> Signup and view all the answers

<p>MHC ATP-ase activity (C)</p> Signup and view all the answers

<p>Release from the sarcoplasmic reticulum (A)</p> Signup and view all the answers

<p>Increased calcium sensitivity (B)</p> Signup and view all the answers

<p>Through Ca channels and SERCA (D)</p> Signup and view all the answers

<p>They increase contractility with decreased load. (D)</p> Signup and view all the answers

<p>Facilitates calcium binding for contraction (D)</p> Signup and view all the answers

<p>Increase in Ca2+ (A)</p> Signup and view all the answers

<p>Decreased pH levels (A)</p> Signup and view all the answers

<p>It relates tension in the heart wall to pressure and radius. (A)</p> Signup and view all the answers

<p>Ventricular filling time (B)</p> Signup and view all the answers

<p>Alpha decreases, beta increases (A)</p> Signup and view all the answers

<p>Sodium channels (D)</p> Signup and view all the answers

<p>Progressive increases in contractility with increased heart rate (D)</p> Signup and view all the answers

<p>Enhanced pH levels (C)</p> Signup and view all the answers

<p>Length-tension relationship (D)</p> Signup and view all the answers

<p>Troponin C (D)</p> Signup and view all the answers

<p>$\Delta E = QA + Wi + QS + We$ (B)</p> Signup and view all the answers

<p>Actin (A)</p> Signup and view all the answers

<p>Increase in force of contraction with greater muscle stretch (B)</p> Signup and view all the answers

<p>Velocity of muscle shortening (C)</p> Signup and view all the answers

<p>Cross-bridge cycling (C)</p> Signup and view all the answers

<p>It has different spliced variants affecting contraction speed (B)</p> Signup and view all the answers

<p>Hill equation (D)</p> Signup and view all the answers

<p>Thick filament (C)</p> Signup and view all the answers

<p>Stroke work = p x SV (D)</p> Signup and view all the answers

<p>Wall tension (D)</p> Signup and view all the answers

<p>Reduces the connection between microtubules and sarcomeres. (C)</p> Signup and view all the answers

<p>Cardiac output and venous return (D)</p> Signup and view all the answers

<p>The energy balance of the cardiac cycle (D)</p> Signup and view all the answers

<p>External load applied during contraction (D)</p> Signup and view all the answers

<p>Calcium release enhances myocardial contractility (C)</p> Signup and view all the answers

<p>Ca uptake via SERCA (A)</p> Signup and view all the answers

<p>Overlap of actin and myosin filaments under certain conditions (A)</p> Signup and view all the answers

<p>Contributes to the duration of contraction (A)</p> Signup and view all the answers

<p>It supports the maintenance of membrane potential without effect on contractility (A)</p> Signup and view all the answers

<p>Load, MHC ATP-ase activity, and calcium ion concentration (A)</p> Signup and view all the answers

<p>Increased preload affecting initial length (B)</p> Signup and view all the answers

<p>Enhanced sodium influx (C)</p> Signup and view all the answers

<p>Chronic overload conditions (A)</p> Signup and view all the answers

<p>Increased expression of beta isoforms (D)</p> Signup and view all the answers

<p>$T = \frac{(p \times R)}{2h}$ (B)</p> Signup and view all the answers

<p>Significant alterations in pH levels (C)</p> Signup and view all the answers

<p>Rate of ATP generation (A)</p> Signup and view all the answers

<p>Higher contractility with repetitive stimulation (A)</p> Signup and view all the answers

<p>Increased intracellular calcium levels (A)</p> Signup and view all the answers

<p>Sarcomere length-tension relationship (D)</p> Signup and view all the answers

<p>Rate of muscle shortening (D)</p> Signup and view all the answers

<p>Troponin C (D)</p> Signup and view all the answers

<p>(P + a) v = b(Po - P) (D)</p> Signup and view all the answers

<p>The enhanced contractility at higher heart rates (D)</p> Signup and view all the answers

<p>Rate of energy liberation equation (B)</p> Signup and view all the answers

<p>Thin filament (A)</p> Signup and view all the answers

<p>Regulates cross-bridge detachment (C)</p> Signup and view all the answers

<p>Troponin T (C)</p> Signup and view all the answers

<p>Constant length with varying tension (A)</p> Signup and view all the answers

The mechanical processes, like contraction and relaxation, within the heart muscle.

The process linking electrical signals to muscle contractions in the heart.

Muscle contraction without change in length.

Muscle contraction with a change in length.

A mathematical model relating muscle force (P) and velocity (v) during contraction.

A protein filament responsible for muscle contraction (in the thick filaments).

A protein filament responsible for muscle contraction (in the thin filaments).

A complex of proteins that regulate muscle contraction, especially by responding to calcium.

The repeating cycle of interactions between myosin and actin filaments that leads to muscle shortening.

The fundamental unit of muscle contraction.

The elasticity of the series components of muscle and other tissues, which is involved in lengthening and shortening.

The relationship between the length of cardiac muscle fibers and the force they generate, showing distinct differences and double-overlap.

The ability of the myocardium to shorten in response to a stimulus; a vital parameter in cardiac function.

Factors influencing the strength of myocardial contractions, including intrinsic factors (like initial sarcomere length) and external factors (like load).

The intracellular calcium concentration, a crucial factor affecting contractility.

The rate at which the myosin protein hydrolyses ATP, directly influencing contractile strength.

Altering the amount of calcium released affects the strength and speed of muscle contractions.

The sensitivity of the proteins that cause contraction to calcium, a core determinant of contractility.

The energy used by the heart to eject blood during a single heartbeat. It's calculated by multiplying stroke volume (SV) and pressure (p).

The total energy used by the heart in one minute. It's calculated by multiplying stroke work by heart rate (HR).

A protective sac that encloses the heart, providing stability and preventing excessive expansion.

The ratio of the useful energy (work done by the heart) to the total energy used by the heart. It represents how efficiently the heart converts energy into useful work.

Microtubules are intracellular structures involved in muscle contraction. Tubulin tyrosine ligase (TTL) regulates microtubule function, and its disruption affects heart contractility.

An increase in contractile force with repeated stimulation at a constant frequency. Describes the phenomenon where heart muscle contractions become stronger with consecutive beats.

A stronger contraction following a premature beat (extrasystole). The heart is able to contract more powerfully after recovering from a premature beat.

A group of drugs that increase the force of heart muscle contractions by inhibiting the sodium-potassium pump, leading to an increase in intracellular calcium.

A decrease in contractile force with repeated stimulation at a constant frequency. The heart muscle gradually weakens with consecutive beats, similar to muscle fatigue.

Activation of the sympathetic nervous system causes increased heart rate and contractility by triggering the release of norepinephrine and adrenaline, leading to increased intracellular calcium.

The relationship between the initial length of heart muscle fibers and the force they generate. A longer muscle fiber length results in a stronger contraction, but only up to a point.

A positive feedback loop where increased preload initially leads to a stronger contraction but eventually causes a decrease in ejection fraction and cardiac function, potentially leading to heart failure.

Describes the relationship between wall tension, pressure, and radius in a hollow chamber like the heart. Higher tension is required to maintain a certain pressure in a larger chamber.

The Fenn effect describes the increase in heat production by muscle during isometric contraction compared to isotonic contraction. This means more energy is used when the muscle shortens.

The Hill equation is a mathematical model describing the relationship between the force (P) and velocity (v) of muscle contraction. It explains how force decreases as velocity increases.

Myosin is a motor protein found in thick filaments, responsible for muscle contraction. Actin is the protein found in thin filaments, which interacts with myosin to generate force.

The troponin complex regulates muscle contraction by binding to calcium. It consists of three proteins: troponin T, troponin I, and troponin C.

The cross-bridge cycle is a series of steps where myosin heads bind to actin, pull, detach, and reset. This cycle is powered by ATP and requires calcium.

In isometric contraction, muscle tension increases but muscle length remains constant. Think of pushing against an immovable object.

In isotonic contraction, muscle length changes while tension remains constant. Think of lifting a weight.

Calcium binds to troponin, initiating a cascade of events that allows myosin and actin to interact, leading to muscle contraction.

The work done by a muscle is related to the energy it uses. More work requires more energy. This energy comes from breaking down ATP.

The elasticity of the components in a muscle that are arranged in series, such as tendons and connective tissues. It contributes to the lengthening and shortening of the muscle during contraction.

When a muscle is rapidly released after being stretched, the series elastic components recoil, contributing to the initial rapid shortening of the muscle. This can be observed in quick-release experiments.

The relationship between the length of a muscle fiber and the force it can generate. In cardiac muscle, there is a specific length at which maximum force is produced, and there are distinct differences in the relationship compared to skeletal muscle.

The heart muscle, responsible for pumping blood throughout the body. It's crucial for maintaining blood flow and oxygen delivery.

The ability of the heart muscle to contract forcefully. It's a vital parameter in cardiac function, affected by factors like the amount of calcium available and the activity of the myosin protein.

Calcium plays a vital role in regulating muscle contraction. Its concentration within the muscle cells (intracellular calcium) directly influences the strength of myocardial contractions.

The activity of the myosin protein, which breaks down ATP to provide energy for muscle contraction, directly affects the strength of myocardial contractions. A faster breakdown of ATP leads to stronger contractions.

External factors, such as the load on the heart, also significantly impact contractility. This includes things like the pressure the heart has to pump against.

The ratio of useful energy (work done by the heart) to the total energy used by the heart. It represents how efficiently the heart converts energy into useful work.

A protective sac that encloses the heart, providing stability and preventing excessive expansion.

Calcium ions (Ca2+) play a crucial role in regulating heart muscle contraction. Mitochondria, the powerhouses of the cell, also accumulate Ca2+. This accumulation impacts heart function by influencing energy production and potentially contributing to intracellular Ca2+ overload.

Cardiac glycosides are drugs that strengthen heart contractions by inhibiting the sodium-potassium pump (Na/K pump). This inhibition leads to a buildup of sodium ions inside the cell, which indirectly increases calcium accumulation and contractility.

Beta-adrenergic stimulation, triggered by the sympathetic nervous system, increases heart rate and contractility. This happens through the release of adrenaline (epinephrine) and norepinephrine, which stimulate the release of calcium from intracellular stores.

The Law of Laplace describes the relationship between wall tension, pressure, and radius within a hollow chamber like the heart. A larger heart chamber requires a greater wall tension to maintain a certain pressure.