Glossary — Page 448, Lesson 692

I want to walk you through some key terms from the glossary that are essential for understanding human performance in the cockpit. Let's start with Diffusion — that's the movement of particles from regions of high concentration to regions of lower concentration. This is a basic physical process that governs how gases move in your lungs and how oxygen gets into your bloodstream. Next, we have three important medical measurement devices you'll see referenced. ECG stands for Electrocardiogram — now, the glossary here says it measures the synchronisation of the brain's electrical impulses with the beating of the heart, specifically the pulse rate. I want to be precise: in standard aviation medicine, an ECG primarily records the electrical activity of the heart itself, but the glossary is highlighting the relationship between brain signals and heart rate. EEG is Electroencephalogram — that measures the electrical activity of the brain directly. EMG is Electromyogram — this measures the electrical activity associated with the contraction and relaxation of muscles. So ECG for heart-brain timing, EEG for brain waves, EMG for muscle activity. Let's move to the inner ear. Endolymph is the fluid that fills the inner ear, and specifically the three semicircular canals. Those canals use this fluid to detect angular movement — that means rotation of your head — and they provide balance cues to your brain. This is critical for a pilot because your semicircular canals can give you false sensations during flight, especially in instrument conditions. Electrolytes — an electrolyte is a chemical capable of carrying or conducting an electrical charge in solution. Your body relies on the presence of electrolytes to carry nerve impulses and to maintain cell metabolism. So when you sweat or become dehydrated, losing electrolytes directly affects your nervous system function. EOG stands for Electroculogram — that's a device to measure eye movement using electrodes attached to the outer corners of the eyes. This is used in sleep research and fatigue studies. Episodic Memory is a part of long-term memory that stores episodes or events in our lives — specific experiences you can recall, like your first solo flight. Ergonomics — this is the principle of design which ensures that the job required should be fitted to the man rather than the man to the job. In aviation, that means cockpit design, seat placement, control layout — everything should be built around the pilot's capabilities and limitations. Expiratory Reserve Volume — this is the amount of air that can still be exhaled by forceful expiration after the end of the normal tidal expiration. So after you breathe out normally, you can force out additional air — that extra volume is the expiratory reserve volume. Faults — this is a category of errors. The key distinction here: the action satisfies the operator's intent, but the intent itself was incorrect. So you did what you meant to do, but what you meant to do was wrong. That's different from a slip, where you intended correctly but executed incorrectly. Fight or Flight — the glossary directs you to see Automatic Nervous System. That's the body's immediate response to a perceived threat, preparing you to either confront it or flee. Formication — this is a creeping sensation felt on the skin as a result or symptom of hypoxia. So if you're not getting enough oxygen at altitude, you might feel like something is crawling on your skin — that's formication. Now the eye. Fovea — that part of the retina composed only of cones, and it's the most central part of the retina. Only at the fovea do you have 6/6 or 20/20 vision — that's standard visual acuity. It is the area of highest visual acuity, and away from the fovea the acuity declines rapidly. So when you're trying to read an instrument or see a distant aircraft, you need to look directly at it so the image falls on your fovea. General Adaptation Syndrome, or GAS — this is the term used to describe the mechanism by which an individual reacts to an outside perceived threat. It's the three-stage stress response: alarm, resistance, and exhaustion. Gestalt Theory — from the German word gestalt meaning "shape". This theory of learning proposes that any individual's understanding of the world results from sorting out and combining multiple cues perceived in the environment until a "coherent whole" appears that is acceptable according to the individual's standards regarding the world. In simple terms, your brain takes in lots of separate pieces of information and organizes them into a meaningful pattern. Finally, Glaucoma — a disease of the eye which causes a pressure rise of the liquid within the eye. Glaucoma can cause severe pain and even blindness. It exists in two forms: Acute and Chronic. For a pilot, this is a significant medical condition that can affect your vision and your ability to hold a medical certificate.