Atrial Systole (Active Ventricular Filling)
心房收縮期（主動心室充盈 #1）
Figure 34.11: Pressure Changes Graph 壓力變化曲線圖 (Click/Drag on graph to scrub)
Left Heart Mechanics & Blood Flow
左心房、左心室、主動脈與瓣膜動態模型
Atrial pressure exceeds ventricular pressure, pushing the bicuspid valve open.
左心房壓高於左心室壓，血液順壓差推開二尖瓣流入心室。
Aortic pressure is much higher than LV pressure, keeping the semilunar valve tightly shut.
主動脈壓遠高於心室壓，高壓血液防止半月瓣開啟。
Step-by-Step Curve Breakdown & Your Notes Explained | 曲線各階段與手寫筆記深度解答
Why is there a small bump at #1?
為何 #1 處紅線與綠線有一小凸起？
During Atrial Systole (A.S.), the left atrium contracts to pump the remaining blood into the left ventricle. Because the bicuspid valve is open, both chambers are connected, so both green (LA) and red (LV) curves show a gentle pressure bump (~0.6 kPa).
在 0.0–0.1s 心房收縮期 (A.S.)，左心房收縮將餘下血液擠入左心室。由於此時二尖瓣處於開啟狀態，心房與心室相通，因此綠線（左心房）與紅線（左心室）同步輕微上升。
Why does the red line shoot straight up at #2?
為何 #2 處紅線幾乎垂直飆升？
At 0.1s, the thick left ventricle begins contracting (V.S.). LV pressure immediately exceeds LA pressure, slamming the bicuspid valve shut (1st heart sound 'lub'). Between 0.1s and 0.15s, LV pressure is still lower than aortic pressure (~10.8 kPa), so the semilunar valve is ALSO closed. Squeezing blood trapped in a completely sealed chamber causes pressure to skyrocket vertically (Isovolumetric Contraction).
在 0.1s，左心室開始強力收縮（V.S.），心室壓瞬間超越心房壓（紅線穿過綠線），衝擊並關閉二尖瓣，產生第一心音 'lub'。在 0.1–0.15s 期間，心室壓仍低於主動脈壓（~10.8 kPa），半月瓣尚未打開。心室在所有瓣膜緊閉的密閉狀態下收縮（等容收縮期），導致壓力垂直暴升！
Why do the red & blue curves arch together at #3?
為何 #3 處紅線與藍線重疊並一同達到最高峰？
At 0.15s, red (LV) crosses above blue (Aorta), forcing the semilunar valve open! Blood rushes from the ventricle into the aorta. Because the two form a single open channel, aortic pressure rises right alongside ventricular pressure to ~15.8 kPa (#3). Meanwhile, your note "blood filling atria" explains why the green line slowly rises from 0.2s to 0.45s: the atrium is in diastole (A.D.), steadily receiving blood from the pulmonary veins behind a closed bicuspid valve!
在 0.15s，紅線（心室壓）超越藍線（主動脈壓），衝開半月瓣！血液大量噴入主動脈，兩腔室相通，故藍線跟隨紅線一同攀升至約 16 kPa 的峰值 (#3)。同時你手寫標註的 "blood filling atria" 解釋了為何 0.2–0.45s 綠線持續上升：因為心房正處於舒張期 (A.D.)，二尖瓣關閉，肺靜脈血液不斷流入心房累積壓力。
Why does the red line plunge while the blue line stays high?
為何 0.4s 後紅線垂直暴跌，藍線卻緩慢下降？
At 0.4s, the ventricle relaxes (V.D.) and LV pressure drops below aortic pressure. Blood in the aorta tries to flow backward, snapping the semilunar valve shut (2nd heart sound 'dub'). LV pressure plunges vertically to ~0 kPa because the ventricle relaxes while both valves are closed. In contrast, the Aorta (blue line) stays high (11–14 kPa) because its thick elastic wall recoils inward (Windkessel effect), continuously squeezing blood forward during diastole!
在 0.4s，心室開始舒張（V.D.），心室壓跌破主動脈壓，主動脈血液回流關閉半月瓣，產生第二心音 'dub'。心室在雙瓣膜關閉下放鬆（等容舒張期），故紅線垂直跌至 0 kPa。相反，主動脈（藍線）維持高壓，是因為主動脈富含彈性纖維，舒張期時管壁彈性回縮（彈性儲器效應），持續推動血液前進。
What happens at 0.45s when red drops below green?
為何 0.45s 紅線跌破綠線後兩者重回低平？
At 0.45s, ventricular pressure falls below the pressure of the blood-filled left atrium (red crosses below green). This pressure difference pushes the bicuspid valve open! Blood stored in the atrium rushes rapidly into the relaxing ventricle, causing both pressures to drop near 0 kPa as the whole heart relaxes together until 0.8s.
在 0.45s，心室壓跌至低於已充盈的左心房壓（紅線跌破綠線），壓力差推開二尖瓣！積聚在心房的血液迅速湧入舒張中的心室，令房室壓力一同回落至接近 0 kPa，全心處於共同舒張並被動充盈，直至 0.8s 週期結束。
How does the Right Ventricle differ from the Left Ventricle?
圖片左上角問題：右心室壓力曲線與左心室有何不同？
Answer: The timing of contraction and valve opening/closing is identical, but the peak pressure in the right ventricle (~3.5 kPa) is much lower than in the left ventricle (~16 kPa). The right ventricle has a thinner muscular wall because it only pumps blood a short distance to the lungs (pulmonary circulation), whereas the left ventricle pumps blood around the entire body (systemic circulation).
解答：右心室壓力變化的時序與形狀與左心室相同，但右心室的最高收縮壓（約 3.5 kPa）遠低於左心室（約 16 kPa）。原因是右心室肌壁較薄，只需將血液泵往距離短、阻力低的肺循環；而左心室肌壁極厚，需產生高壓以克服全身體循環的高阻力。