Chapter 1
The body's three engines
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Chapter 2
Levers, lines, and brain signals
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Chapter 3
Fueling the fire
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Chapter 4
Weird, wild, and ancient muscles
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YOUR GOAL
Master of The human muscular system
Ch 4 · Weird, wild, and ancient muscles
artiteacher Human Muscular System
Got a mighty bite? Your masseter's power, Holds your jaw so tight!
Fun Fact
Ear wiggling: The auricularis muscles around our ears are evolutionary leftovers that once helped our ancestors pinpoint distant sounds.
Glossary
palmaris longus (noun)
A superficial muscle of the forearm that helps to flex the hand at the wrist. Roughly fifteen percent of humans lack this tendon, which once aided primate ancestors in climbing trees.
A superficial muscle of the forearm that helps to flex the hand at the wrist. Roughly fifteen percent of humans lack this tendon, which once aided primate ancestors in climbing trees.
Quiz
What type of neural pathway allows reflexes like the knee-jerk reflex to occur without involving the brain?
Quiz
Why does the human body shiver involuntarily when exposed to cold temperatures?
Quiz
Which muscle in the human body is capable of exerting the most pressure relative to its size, primarily used for chewing?
Quiz
Which muscles in the human body are considered the fastest-acting, capable of contracting in under 100 milliseconds?
Quiz
What evolutionary purpose did ear-wiggling muscles once serve for human ancestors?
Quiz
What tiny muscles at the base of hair follicles contract to cause goosebumps when you are cold or scared?
Quiz
What is the palmaris longus, which is missing in about 14 percent of the modern human population?
Quiz
What is the main cause of the condition known as rigor mortis, where muscles stiffen after death?