Any external signal that causes a fluctuation from a set point.
What is a stimulus?
The skin is part of this subcategory of the immune system.
What is the innate immune system?

What is COVID-19?
Bone 1

What is the mandible?
This type of fracture breaks through the skin.
What is an open fracture?
Your body shivering is this type of feedback.
What is negative feedback?
Proteins that are produced by B-Cells.
What are antibodies?
Structure B
What is the capsid?
Bone 7

What is the clavicle?
This type of fracture leaves your bones misaligned.
What is a displaced fracture?
Blood clotting is this type of feedback.
What is positive feedback?
A type of "medicine" that introduces an antigen to your immune system to prepare for future infections.
What is a vaccine?
The protein on the surface of COVID-19 that carries the main antigen.
What is the spike (s) protein?
Bone 8

What is the humerus?
The type of fracture show in this x-ray image.

What is closed/non-displaced/transverse?
Thermoregulation is a common form of this type of feedback.
What is negative feedback?
The next step after 'attachment' in a virus lifecycle.
What is entry?
Bone 2

What is the sternum?
A type of fracture that results in bone being broken into multiple pieces or fragments.
What is comminuted fracture?
The release of oxytocin that stimulates uterine contractions is an example of this type of feedback.
What is positive feedback?
Once activated by a helper T-cell, this type of B cell releases antibodies into the blood stream.
What are plasma cells?
This type of viral RNA must first be converted into a different form before creating proteins.
What is negative-sense RNA?
Bone 19

What are the phalanges?
What is greenstick?