chapter 9 - muscular system; part 2

Question 1

what is a triad?

Answer 1

it is a T tubule and two terminal cisternae (an enlarged area of sarcoplasmic reticulum)

Question 2

what happens when action potentials move into the T tubule system?

Answer 2

this causes Ca2+ channels to open and release Ca2+ from the sarcoplasmic reticulum

Question 3

ATP is required for what?

Answer 3

it is required for the cycle of cross-bridge formation, movement, and release; also to transport Ca2+ into the sarcoplasmic reticulum and to maintain normal concentration gradients across the plasma membrane

Question 4

where are calcium ions transported to?

Answer 4

they are transported into the sarcoplasmic reticulum

Question 5

where do calcium ions diffuse away from?

Answer 5

they diffuse away from troponin, preventing further crossbridge formation

Question 6

what is a muscle twitch?

Answer 6

it is the contraction of a single muscle fiber or a whole muscle in response to a stimulus; a muscle twitch has lag, contraction, and relaxation phases

Question 7

what is a motor unit?

Answer 7

it is one motor neuron and all the muscle fibers it controls

Question 8

precise movement

Answer 8

uses small motor units

Question 9

gross movement

Answer 9

uses larger motor units

Question 10

treppe

Answer 10

it is an increase in the force of contraction during the first few contractions of a rested muscle; the force of contraction of a whole muscle increases with increased frequency of stimulation because of an increasing concentration of Ca2+ around the myofibrils and because of complete stretching of muscle elastic elements