A dramatic medical and cinematic illustration of the human cardiovascular and nervous system during severe presyncope (pre-fainting). A transparent human silhouette is shown from the waist up. The heart in the chest is glowing with an intense, chaotic fiery red and orange light, pulsating rapidly to represent tachycardia. Thick, vibrant red blood vessel pathways force a powerful updraft of glowing light particles up through the carotid arteries toward the neck and head. The brain at the top is contrasting, glowing in a dimming, fading cold blue and pale white, showing a critical lack of oxygen and energy. Dark, smoky tendrils blur the edges of the frame to simulate tunnel vision. Deep black background, highly detailed anatomy, octane render, 8k resolution, cinematic lighting.