The 650 skeletal muscles in the human body contract when they receive signals from motor neurons, which are triggered from a part of the cell called the sarcoplasmic reticulum. Motor neurons tell your muscles to contract and the better you become at having those signals tell your muscles to contract, the stronger you can get.
A. a persons pitch or inflection
Answer:
Vertical allows people to nod, horizontal allows people to twirl
Explanation:
The vestibular system, which is key to our senses of balance, motion, and body position, is comprised of three semicircular canals connected to two membranous sacs called the saccule and utricle. The saccule and utricle are often referred to as the otolith organs. The otolith organs allow us to sense the direction and speed of linear acceleration and the position (tilt) of the head. The semicircular canals allow us to sense the direction and speed of angular acceleration. The semicircular canals are oriented along three planes of movement with each plane at right angles to the other two. Pilots and astronauts call these three planes of rotation pitch (<u>up and down; nod your head "yes")</u>, roll <u>(tumbling left or right; move your head from your left to your right shoulder or vice versa)</u>, and yaw (<u>lateral movement left and right; shake your head "no").</u>
