The Locus coeruleus is a part of the brainstem and is responsible for the physiological responses in the body related to stress and panic. The Locus coeruleus is one of the main areas where the neurotransmitter norepinephrine is produced, norepinephrine is one of the two main types of adrenaline found in the body and mainly plays a role in the "fight or flight" response. In the brain norepinephrine increases arousal and alertness, promotes vigilance, enhances formation and retrieval of memory, and focuses attention; it also increases restlessness and anxiety. In the rest of the body, norepinephrine increases heart rate and blood pressure.
When Strand said that their "better angels are dead" he is paraphrasing a speech made by Abraham Lincoln during his inaugural address, Lincoln was admonishing the nation to put aside hate and anger and set aside their differences as his inauguration occurred at the outbreak of the civil war. Better Angels (2012) also makes use of this phrase.
The title of this episode "the slaughter yard" in Spanish.